V6 Engineering
V6 Engineering
V6 Engineering
Materials Technology I
This need for information before mining starts is the classical problem of exploration.
Two main aspects are to be considered:
Geometry of the raw material deposit, that means geological boundaries like interfaces of
formations, faults and also topography
Quality of the rocks in terms of chemical and mineralogical composition, physical
characteristics like hardness, abrasiveness, pozzolanic activity.
Obviously this task of exploration is not a simple one. Our means of acquiring data is limited
compared to the large size of rock volumes to be investigated. Exploration drillings provide
precise but also very spotty information on the rock volumes. In order to fill the gaps
Cement Manufacturing Course Version 2005 Volume 1 - Page 4
between drillholes and also in order to interpret results of drillings, we need a model of the
raw material deposit. This model is developed with the help of the natural science
GEOLOGY. Within this science, all aspects with respect to rock formation, deformation and
transformation are studied and general rules are established. These concepts of geology are
absolutely instrumental for the interpretation of any raw material deposit.
The application of geology is, however, also an ambiguous matter. There are hardly two
geologists who are of the same opinion on a given raw material deposit. This fact creates
confusion especially amongst engineers, who are used to well-defined systems, expressed
in precise figures. Exactly these precise figures can never be provided by the geologists,
because of the inherent ambiguities of the geology. Why is that so?
Geology is a relatively young natural science. It is part of nature and hence very tricky. The
development of this science is not as advanced as, for example, chemistry or physics. The
reason for this lies in the complexity of the subject. It represents a combination of every
conceivable combination of physical, chemical and biological processes at all scales.
Many phenomenons observed in nature are not understood and related processes are not
controlled by scientists. A good example of this fact is the inability to predict earthquakes.
A further reason lies in the fact that geology deals with very different dimensions, from the
very tiny atoms and molecules to finally the whole globe. Especially the large dimensions are
difficult to overcome.
Additionally geology deals with a very long time span. It is an ambitious task to reconstruct
the history of a given rock because of the scarce information. Normally such a history has to
be pieced together the geologist is obliged to use his imagination to fill in gaps in the
information.
Nevertheless, the geological concepts are the only help in the interpretation of raw material
deposits. In order to arrive at the best possible interpretation, it is important to ask the most
adequate person for an opinion. Considering the many different specialists which exist in the
field of geology (see table 1), the choice is not always easy. Very often different specialists
contribute to the erection of a geological model for a raw material deposit. As for instance in
the field of medicine, it is important to select the correct specialist for the purpose in mind
(nobody would select as gynaecologist for an appendix operation).
Because of the difficulties described, the results of geological studies are often qualitative.
For the design of a cement or aggregate plant, however, the engineers require quantitative
results. Also from this side emerges a problem of communication between geologists and
engineers. This is expressed in the fact that qualitative statements of the geologists are
discarded by engineers, and that they the base the design of equipment on shaky but
apparently precise figures. The result of this practice can be very costly. It is the aim of the
following lessons to improve on this special communication between geologists and
engineers.
The geologists have to learn that quantification is an absolute must in our industry
The engineers have to learn that no raw material deposit is homogenous and no deposit
can be characterized by precise figures alone.
Geological Specialities
Stratigraphy/Biostratigraphy
Igneous Geology
Volcanology
Sedimentology
Structural Geology/Tectonics
Paleontology/Micropaleontology
Palynology
Geochemistry
Hydrology
Geophysics
Oil Geology
Engineering Geology
Paleogeography
TABLE 2
The crust and the upper mantle together form the lithosphere, which forms a solid plate of
rock of about 100 km thickness.
O 46,6 %
Si 27,7 %
Al 8,1 % 91,0 %
Fe 5,0 %
Ca 3,6 %
Na 2,8 %
K 2,6 %
Mg 2,1 %
Rocks of this type are often used in Cement and aggregate industry, e.g. as pozolana or
crushed rock (granite, basalt), see table 4.
Volcanics tuff
ash
lava
perlite
agglomerate
Plutonics granite
diorite
Intrusives andesite, basalt
Deposition occurs frequently in the form of a more or less horizontal layering called
stratification (strata = layer).
Sedimentary rocks are the most significant resource for the cement and aggregate industry
(Table 5). Detailed descriptions and criteria of assessment are given in section 4
"Assessment of Cement Raw Materials".
chemical limestone
gypsum
anhydrite
ironoxihydrate
aluminiumoxihydrate
rock salt
organic limestone
coal
oil
TABLE 11
These ion concentrations are derived from weathering and dissolution processes onshore,
e.g. in mountain ranges.
Fig. 5 summarizes the chemical conditions for common sedimentary minerals :
H2O H+ + OH -
aq aq
The knowledge of chemical equilibrium constants and pH of natural sea water made it
possible to calculate carbonate solubilities for various marine environments.
It has been found that in shallow, warm sea waters concentration of CaCO3 is close to
saturation. This depends largely on the peculiar behaviour of H2CO3, which dissolves calcite
when present in higher concentrations and only stimulates CaCO3 precipitation when
present in small quantities. This is the case in relatively warm water, where plants
additionally remove CO2, calcite is readily removed by dissolution. Below ~ 4000 m, the so-
called "compensation depth", no calcite is normally present.
The dominant energy source is waves, the tide and long shore currents. Particles are
extensively reworked and rearranged, refer Fig. 5e. Note the occurrence of dunes which
depend also on wind transport. According to climate, tide differences, material supply and
vegetation, many variations of the presented model may occur.
Deep sea fan (bathyal to abyssal environment)
Deep sea fans are formed by means of a special transport mechanism called "turbidity
current". Unconsolidated particles which are deposited on the shelf edge may become
unstable and start to flow downwards in form of an high density aquatic suspension. These
carry large masses of sediments down the continental slope and spread in the deep marine
basins over large areas (thousands of km2). During settling of the particles, typical "graded
bedding" develops.In addition to which various other sedimentary features such as flue
casts, parallel lamination, current ripple lamination, convolute bedding and pelitic (clay)
layers.
The same principles may be applied to the group of calcareous-siliceous (sandy) materials
and the group of siliceous and clayey rocks.
Cement Manufacturing Course Version 2005 Volume 1 - Page 36
1.6 Structural geology
Structural geology deals with the deformation of rocks. This deformation is a result of
tectonic (mechanical) forces, which occur in the solid lithosphere due to movements of the
continental plates. In detail, a stressfield applied on the rock formations results in
deformation in form of rupture in the case of brittle deformation or flow in case of plastic
deformation. These stressfield forces are very large and act over long time periods. In the
case of brittle deformation, the theoretical approach by means of physical - mathematical
methods is not too complex. However, as soon as plastic deformation over a long period of
time is also considered the analytical approach becomes very complicated. The study of the
phenomena of rock deformation is known as "tectonics." A science, which incorporates
higher mathematics.and physics.
In our industry the structural behaviour and characteristics of the raw material deposits is of
high interest, since it has an important impact on the distribution of rock qualities within the
deposits. For the description of deformation, one requires a reference system, which shows
the effect of deformation with regard to an original, undeformed situation. One very common
system is stratification, a frequently observed sedimentary feature. In it's original state
stratification is practically horizontal, due to the gravity forces. If strata are found in inclined
position in the field, a deformation phase is normally responsible.
By measuring the inclined position of bedding planes, fault planes, joint surfaces, inclination
and orientation of folds etc. the degree and type of deformation can be determined.
The corresponding measurements are called strike and dip. For example, in order to
measure the orientation and inclination (strike and dip) of a bedding plane (refer figure 8).
The intersection of the inclined bedding plane and an imaginary horizontal plane (water line)
represents a straight line in space. This line or 'strike direction' has an astronomical
orientation, which is measured, with a compass, in degrees clockwise from the (Azimuth).
The inclination, or 'dip', of the bedding plane is measured along a line perpendicular to the
strike direction. The dip angle is measured with an inlinometer in degrees with respect to the
horizontal plane. There are normally two solutions for this dip angle depending on the
orientation 'strike' of the bedding plane ie. dipping in a N or S direction.
A complete measurement of strike and dip of a bedding plane at the locality (or position) A21
would be "A21 - 124 / 25 N". There are various conventions in different countries for
recording these measurements. In the USA the dip direction is very often given in form of an
azimuth reading such that the above reading would be "A21 - 034 / 24."
By means of these measurements it is often possible to define the type and intensity of rock
deformation and therefore work out the "tectonic style" of a given raw material deposit. In the
case of geologic faults, three main fault types are defined, based on the orientation of the
three main stress axis of the applied stressfield (1, 2 and 3, whereby 1>2>3) (Fig.
9):
1 vertical, 2 and 3 horizontal: the gravity becomes the largest force and therefore
blocks of rock glide downward along typically inclined faults of 60. These faults are
called normal faults. They are typical for extensional tectonics.
1 and 2 horizontal, 3 vertical: This situation represents a compressional regime,
where the rock body is shortened by overthrusts and or folds. Typically, the fault planes
are inclined 30 with respect to the horizontal plane.
1 and 3 horizontal, 2 vertical: The result of this configuration is the so called strike-
slip faults (or wrench faults) which are generally vertical and indicate a strike which
deviates 30 from the 1 direction.
In nature, these clear-cut cases are seldom found. Fault zones are mostly accompanied by
secondary faults and by a pattern of "joints" (small fractures).
Combination of fault types and repetitions thereof are frequently found, e.g. series of normal
faults, series of overthrusts and folds etc.
In case of folding, the variability of structures produced is also bewildering (see fig 10):
depending on the geology of the rocks involved and the stress forces applied, a wide range
of different of folds types develop.
Fig. 10 (A) Symmetrical, open, nonplunging anticline, showing the position of the axial
surface (AS). (B) Asymmetrical south-plunging folds showing the position of the axial surface
(AS) in the anticline. In this case the axial surface to the west. (C) Isoclinal, nonplunging,
closed, inclined fold. (D) Overturned north-plunging fold. Overturning is to the east. The axial
surfaces (AS) dip west-ward. (E) Recumbent, nonplunging fold. The axial surface is
essentially horizontal. Sometimes referred to as "nappe structures," although the underlying
limb is not always present (e.g., Austro-Alpine nappes). (F) Monocline. (G) Cylindrical, east-
plunging anticline. (H) Conical, west-plunging syncline. The plunge symbols diverge from a
vertex located near the east edge of the diagram.
1. INTRODUCTION ..............................................................................................................43
2. DESK STUDY ..................................................................................................................44
2.1 Geological maps........................................................................................................44
2.2 Documents ................................................................................................................47
2.3 Photogeology ............................................................................................................47
2.4 Remote sensing ........................................................................................................48
2.5 Where to look for information? ..................................................................................49
2.6 Results of the desk study ..........................................................................................49
2. INTRODUCTION
In the following chapters, we will elaborate on the procedures developed especially for the
exploration of raw materials for cement and aggregates. The proposed scheme is based on
experience and modeled according to the needs of the cement industry. Of course, every
exploration project is unique and requires a particular approach.
Basically, the scope and extent of every exploration procedure is governed by the following
series of criteria:
Scope of work
Status of geological knowledge of the area to be examined
Raw materials: exposures, structures, overburden
Time and financial resources available
Climatic conditions
Physiography and topography of the area
The Holcim approach
The deposits are investigated in a stepwise fashion from a general overview to more detailed
exploration activities. Each step is defined with regard to the respective scope, extent, costs,
time requirement, reliability of the results (error limits) and the development of risk.
In practice, the proposed procedure encompasses the following sequence of events:
1) Desk study
2) Preliminary prospecting of raw materials
3) Overall investigations of raw materials
4) Detailed investigations of raw materials
3. DESK STUDY
Once the scope of work for required investigations has been agreed on and a quotation
therefore accepted a fact finding study is conducted. This study, called a desk study, is
carried out with the aim of gathering and evaluating all the available data and information.
In consideration of the cost, field work must be focused on selected areas. A successful
exploration programme will therefore begin with a literature search and the geologist will look
for the followings documents:
3.3 Photogeology
A considerable amount of geological information can be obtained from the interpretation of
from aerial photographs,. Different rock types can be identified because of their strong tonal
and textural contrasts due to:
erosion levels and patterns
colour and reflectivity
vegetation cover
structure
Lineaments (faults or other discontinuities) may be distinguishable as any alignment of
features on an aerial photograph.
Folds are easily recognized and it is often possible to define the fold type (i.e. open, tight).
Fig. 3 shows a folded structure where it is possible to differentiate several lithologies. Dip
and strike of the layers and fold axis can be determined.
From an aerial photograph, structure and a lithology can be quickly defined.
Tools Resolution
(pixels)
Landsat MultiSpectral Scanner (MSS) 80 m
Landsat Thematic Mapper (TM) 30 m
SPOT MultiSpectral Scanner (SPOT-XS) 20 m
SPOT Panchromatic (SPOT-P) 10 m
ERS-1 (European Radar Satellite) 10 m
RadarSat
Airborne Radar (Radar)
Passive sensors like Landsat and SPOT can not see through clouds since they depend on
naturally reflected or radiated energy. Only an active sensor, like radar, which emits a signal
and records its reflection can penetrate clouds.
In heavily vegetated areas or in regions with high sun angles or with a low relief, the use of
radar will significantly increase the visibility of the structure.
An example of prospecting for raw materials at Polpaico - Chile, by remote sensing, is given
at the end of this chapter.
1. GENERAL ........................................................................................................................51
2. THEORETICAL INTRODUCTION....................................................................................52
2.1 General......................................................................................................................52
2.2 LANDSAT satellites...................................................................................................52
2.3 Generation of images ................................................................................................53
2.4 Analysis of the information ........................................................................................53
3. GEOLOGICAL EXAMINATION .......................................................................................54
3.1 Introduction................................................................................................................54
3.2 Results of the photos.................................................................................................55
3.3 Results of examinations on site.................................................................................55
4. CONCLUDING REMARKS ..............................................................................................56
1. GENERAL
There are very few limestone deposits in Chile. This applies particularly to the central region
of this extremely long country of 4000 km. Only in the south (Madre de Dios archipelago)
and in the cordilleras of the Andes at an altitude of 3000 to 5000 m above sea-level near the
border to Argentina, are there any significant limestone deposits.
The two factories which satisfy the needs of the greater part of the market round Santiago
and the rest of the country utilize deposits which incur heavy raw-material costs. Cemento
Polpaico utilizes a deposit of siliceous limestone 40 km north of Santiago, a material which
requires a special flotation treatment, while Cemento Mlon exploits a lime-stone deposit of
good quality situated some 120 km north of Santiago, where it is mined 500 m below
ground-level.
In view of this situation, it was decided in 1992 that prospecting for new limestone deposits
should be carried out along the coastal Cordilleras, roughly between 31 and 33 of longitude
S, representing an area of some 12 000 km2. One third of this area exhibited geological
formations in which limestone could be expected with a certain degree of probability.
The exploration of such a large area demanded many days of field work on the spot. To
reduce this to a minimum, the most interesting zones had to be selected beforehand, and
then work concentrated on them. The most obvious question was: Where are these areas
and how can they be selected? To obtain an answer it was decided to resort to the analysis
of satellite photos.
This procedure is used quite often when prospecting for metallic raw material, especially in
Northern Chile, and astonishing results have been achieved. One company, for instance,
located a large gold deposit in the region of Zapaleri (high cordilleras of the Atacama region)
solely with the aid of satellite photos, and this long before the geologists working for the
competitors had returned to their offices, analyzed their data and likewise reached the
conclusion that the area was of interest. With non-metallic deposits not so much experience
has been acquired, but it is nevertheless very promising, as the discovery of large saltpetre
shows deposits in the Atacama Desert. And thereby hangs a tale: When examining the
satellite photos, a line was observed which crosses the entire desert and consisted of
saltpetre. When this remarkable phenomenon was examined on site, the line was found to
be the route by which the Incas used to transport saltpetre to Peru. The saltpetre recorded in
the photos was lost on the way by the pack animals.
In view of the excellent results obtained with this method it was decided that it should be
used for limestone, despite the lack of experience with this material. First the feasibility of the
method was tested with photos of the known deposits in the area surrounding the works of
Cemento Polpaico. They are located between 3230' and 3330' longitude (Fig. 1). Owing to
the proximity of the area and its good accessibility, it was an easy matter to check the
results. It ought to be possible to see the limestone deposits of Cemento Polpaico and
Mlon, which were of use in analysing the satellite information.
2. THEORETICAL INTRODUCTION
2.1 General
The use of satellite photos of the Earth's surface has grown in importance for geological
investigations since the seventies, when the first satellite of the LANDSAT series was put in
orbit. With satellites certain information can be acquired quicker and more economically than
with conventional methods.
The photo gives a representative impression of the surface, though vegetation can prove
disturbing. For this reason the method provides better results in semi-dry, desert-like areas
where the rock strata are more exposed.
In the latest method known as remote sensing, a sensor (or a group of sensors) suitable for
measuring the intensity in a given waveband in the electromagnetic spectrum is mounted on
an aircraft, a helicopter or a satellite, so as to cover the largest possible area for prospecting.
There are a number of satellites fitted in this way, such as LANDSAT, SPOT and NOAA,
which were developed for the particular purposes.
3. GEOLOGICAL EXAMINATION
3.1 Introduction
The area selected for the examination corresponds to a segment of the coastal Cordilleras
situated roughly between 3230' and 3330' S in longitude. A photo was used which had
been taken by LANDSAT TM at 10 a.m. on a summer morning (March).
In summer this area also exhibits quite an appreciable coverage of vegetation (about 70%),
but it decreases notably with increasing altitude. Although this affects the method, it was
hoped that interesting places would be found in the uncovered areas as well as limestone
outcrops in covered areas. At the strongest resolution of the sensor deposits 30 m or more in
size would saturate the photo to such an extent that identification would be quite easy.
In view of the fact that carbonate cannot be identified by the bands detected by TM and,
moreover, certain bands are easily mistaken for hydroxyls, it was decided that the PC and
the comparison method should be used, using the limestone outcrops in the region of
Polpaico as reference pattern. The limestone deposits of the open quarry could not be used
as reference because their white colour and the outstanding reflection properties of the
surface saturated all bands. The photos obtained by combining different PCs and bands
were therefore modified so that their colours stressed the zones in which there were known
to be limestone outcrops, whereas the rest of the photo was darkened, assuming that areas
containing unknown limestone outcrops would be stressed to the same extent.
Fig. 1: PC1/PC2/B1: Points with a clear yellow colour and/or very weak red
pigmentation were selected.
Fig. 2: PC1/PC2/PC3: Points with a pink colour and light green pigmentation
were selected.
Fig. 3: PC2/PC3/PC4: Points with a definite olive-green colour and a clear light-
blue tinge were selected.
Fig. 4 On account of the comparison of the results of the various photos the
areas shown were selected
4. CONCLUDING REMARKS
This method can be used in the regional search for limestone deposits. The subsequent
local search does not last long and involves lower costs than when conventional methods
are used (about 0.5 US$/m2), although the initial investment appears high.
Exclusive use of this method cannot solve the problem. It is essential to carefully study the
literature at the same time, in order that adequate results may be obtained.
As regards the investigation carried out, it is judged to be a success from the geological
point of view. In addition to the results (no limestone reserves in the area examined) it
showed Polpaico the necessity for developing new strategies to locate additional reserves of
raw materials in other areas.
We should like to thank Cemento Polpaico for financing and supporting us in the
development of this new method, and the experts of the University of Chile for their active
cooperation in analysing the information.
1. INTRODUCTION ..............................................................................................................60
2. GEOGRAPHICAL SITUATION OF THE DEPOSITS.......................................................60
3. GEOLOGICAL SITUATION OF THE DEPOSITS ............................................................60
4. SAMPLING.......................................................................................................................61
4.1 Sampling methods.....................................................................................................61
4.2 Quantity of materials .................................................................................................64
5. QUALITY OF THE RAW MATERIALS ............................................................................66
5.1 Quality of raw materials for cement manufacturing ...................................................67
5.2 Quality of pozzolanas ...............................................................................................67
5.3 Quality of aggregates ................................................................................................68
In some cases, the sample quantity is also determined the testing programme to be carried
out. Experience has shown that the following quantities of cement raw materials are
necessary for laboratory tests conforming to HMC standards (Table 1).
Cl- < 0.02 % All components can have high Cl- content
From a physical point of view, the outcrops are investigated in order to determine the
following features:
Table 1
Geophysics Drilling
Logistic portable heavy drilling machine
Information 17 vertical electrical 17 drill holes (850
soundings m)
Data Additional 3 drill holes (150 m) none
exploration
Field acquisition 4 days 85 days
Duration Interpretation 2 days 3 days
Additional drilling 15 days -
Total 21 days 88 days
geophysics: 10'400 88'000 US$
US$
Cost add. Drillings: 16'000
US$
Total 264000 US$ 88000 US$
drilling advance: 10 m/day drilling cost: 100 US$/m specialist: 1000 US$/day
2 labourers: 300 US/day each geophysical tools: 2000 US$
The cost of the application of refraction seismics will be within the same range. On the other
hand, the cost of the application of reflection seismics would be around 30% more
expensive.
Nevertheless, the geophysical methods are indirect methods of reconnaissance. The results
are physical values which have to be interpreted in terms of rocks and/or sediments. The
experience of the geologist / geophysicist and a good knowledge of the local geology are
indispensable prerequisites for obtaining very accurate results. The main disadvantages are
as follows:
no samples
drill hole of calibration
Calibration of the geophysical values within a few drill holes considerably improves the
accuracy of the results. It is also advisable to sink two to three drill holes after a geophysical
campaign.
3.1 Geoelectrics
An electricity field is emitted by one or two electrodes, and the difference of potential created
by this field is measured by two other electrodes. Different types of array are available to the
specialist. The most frequently applied arrays for prospecting are as follows:
Vertical electrical sounding (YES) Schlumberger type
Four pole profiling (4P-PRFL)
The goal of the geoelectrical methods is as follows:
With VES, to define the true resistivity . This allows to determine the kind of rocks and
the thickness of the formation
With 4P-PRFL, to map the distribution of the apparent resistivity. This reveals the
structure of the subsurface for a given depth of investigation depending of the array
configuration
3.2 Seismics
Waves are artificially generated by means of explosions or hammer within the earth crust.
The waves are reflected and refracted on the in homogeneous plans (fault) or on
stratification. The wave characteristics and the time during which the seismics waves pass
from the emission centre to the geophones are recorded.
In refraction seismics, only the first arrival waves are considered. The Fig. 1 shows a record
of refraction seismics. This method is suitable for determination of rock quality (i.e.
rippability).
In reflection seismics, all reflected waves are considered. A shallow reflection seismics
allows the interpretation of complex geological situation on the subsurface for a few years.
In shallow reflection seismic, acquisition of raw data and its processing must be treated with
great care.
Cement Manufacturing Course Version 2005 Volume 1 - Page 73
In the acquisition of raw data, the distance between the points of emission and the distance
between the geophones are very important . These distances influence the data density
which can be defined by the two following parameters:
Coverage: how often a point on a reflector is reached by a roll along acquisition
Common depth point (CDP) corresponds to half the distance between the geophone
An example of the importance of the raw data acquisition is given in Fig 2. The effect of the
variation of the data density can be clearly seen.
For shallow seismic surveys, the consistent use of both reflection and refraction profiling is
recommended. Although the reflection method is unrivaled for imaging the more complex
geological structures, usually better velocities of the subsurface layers are obtained by
refraction analysis.
Table 2
An estimate of the price of the shallow reflection seismic is given in Fig. 3 in relation to the
depth of investigation.
3.4 Geomagnetics
Geomagnetic method is the measure of the geomagnetic field on the surface. Iron-ore
deposits are particularly suitable for investigation with this method, but it is less suitable for
investigations of raw materials for cement.
3.5 Radar
Radar is a new method of prospecting, based on the electromagnetic waves. The tools
consist of two antennae - transmitter and receiver. The transmitter generates
electromagnetic impulses of 22 up to 100 MHz frequency. The depth of investigation
depends on the frequency and of the mineral composition of the subsurface. An example of
a radar is shown in Fig 4.
The apparent resistivity maps in Fig. 7 show the apparent resistivity for two different depths
of investigation. The interpretation of these maps gives the geologist an indication of the
structure of the subsurface for the investigated depth.
The result of this investigation is shown in the contour line map of the granite (Fig 8)
Fig. 8 Thickness of the basalt and contour line map of the top of the granite
The lithological contact as well as the thin interbeds of clay are clearly identified.
1. INTRODUCTION ..............................................................................................................95
2. DRILLING.........................................................................................................................96
2.1 Diamond core drill .....................................................................................................96
2.2 Other types of drilling ................................................................................................99
3. GEOLOGICAL MAPS AND CROSS -SECTIONS .........................................................100
3.1 Geological mapping.................................................................................................100
3.2 Geological cross-sections .......................................................................................104
3.3 Classification of reserves ........................................................................................109
4. OVERBURDEN ..............................................................................................................111
5. BULK SAMPLing TECHNOLOGICAL TESTS..............................................................113
5. INTRODUCTION
The overall raw materials exploration serves the purpose of acquiring sufficient data on a
raw material deposit in order to establish a feasibility study for a project. It is important that
the investigation program is well specified and that the responsibilities are clearly defined.
This incorporates methods, responsibilities, information flow, cost controls, schedule and
milestones.
The investigations of the quality and the quantity of 1 to 3 deposits (which were shortlisted in
the preliminary field investigations) are appraised. The following work needs to be carried
out in order to obtain accurate information about the deposits:
Geological mapping and cross-sections.
Purpose : Distribution of the lithology / formations and geological structure
Drilling :
1'000 to 2'000 m of core drilling for the main limestone deposit
500 to 1'000 m for the secondary deposits.
Purpose : Description of the lithology, sedimentology, structure, moisture content,
porosity, density, compressive strength, sampling for chemical analyses
Chemical analyses :
LOI, SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, K2O,Na2O,TiO2, P2O5, Mn2O3, Cl-
Calculation of reserves
Geophysics if necessary
Raw mix design
Preliminary concept of quarrying
Bulk samples for technological tests
The results of these investigations must be sufficiently precise in order to decide on the
feasibility of the project with regard to the raw material aspects.
6.1.1 Bits
The bits consist of a steel blank, to the lower end of which a metallic alloy matrix is sintered.
This matrix is encrusted or impregnated with diamond grains (natural or synthetic) or
occasionally with chips of tungsten carbide or silicon carbide as special alternative.
In soft formations such as clay, larger teeth or blades are needed. The cutting edge being
made of tungsten or silicon carbide or polycrystalline diamond.
6.1.4 Recovery
The drilling should be carried out in such a manner that a maximum core recovery is
ensured.
The minimum core recovery is 95% per drill hole. Below 80 %, the accuracy of the geological
information derived and associated chemical analysis is doubtful.
According to Holcim drilling specifications, the client has the right to reject the core and
therefore the samples received from the drilling contractor if the core recovery is below 80%.
Only if the insufficient core recovery is due to inadequate drilling. In which event, the
contractor is obliged to redrill the borehole at no cost to the client. On the other hand the
drilling contractor, cannot be held responsible if the geologist confirms that the poor core
recovery is due to lithological features (e.g. cavities, caves, incompetent ground, etc).
Good core recovery is difficult to obtain from unconsolidated material for two reasons:
large gravel pieces tend to either move about in the core bit and so prevent clean cutting
or they jam in the bit
fine sand, whilst feeding into the barrel, will not be rigid enough to be retained by the
core lifter.
Folding may entail incorrect reserve estimates. In this case (Fig. 10), the claystone formation
could not be recognised at the surface. By measuring dip and strike, the anticline structure of
this deposit would in all likelyhood have been detected.
Once the geological and geochemical limits are well defined within the deposit boundaries
(physical, chemical, legal, etc.) the reserve calculations can be carried out.
Prior to calculating the reserves the following parameters must be defined.
Geological structure of the deposit: limit of formations
Structures: dip and strike of stratas, folds, fault
Overburden
Groundwater level, natural drainage
Qualitative limits: chemical
Mineralogical
Base mining level and the final slope of the quarry
Physical properties
Economical aspect
The most suitable method to calculate the reserves is based on geological cross-sections
and the distance between each parallel cross section (Fig. 11f).
V= ((A1 + A2)/2) * L12+ ......+ ((Am + An)/2) * Lmn
V = volume
Am= surface area of the cross-section m
Lmn= distance between cross-sections m and n
For a deposit with horizontal stratification, the volume is quickly calculated by determining
the area and multiplying it by the thickness of the useable rocks.
Calculation of the tonnage
The reserves are normally indicated in tons rather than in volume. The bulk apparent specific
weight has to be determined on a few samples.
Reserves of raw material = V * r
r = density
8. OVERBURDEN
Overburden is defined as material of any nature, consolidated or unconsolidated which
overlies the deposit of useful materials. Ideally, attempts should always be made to utilise
the overburden material as a raw material component. Should utilisation be impossible due
to chemical or physical character, the overburden is dumped in selected areas. These areas
should be optimised with respect to potential rehabilitation and transportation costs.
Moreover, the dumping areas should never obstruct the exploitation. Fig 12 shows few
favourable and inappropriate dumping areas. Unsuitable areas of dumps may render further
exploitation uneconomical and may reduce the potential reserves considerably.
In the overall investigations, the amount and the quality of the overburden must be defined
accurately. An important consideration in the economics of the open pit mining is the
stripping ratio, which is defined as the ratio of total waste removed to total suitable material
mined. The overburden ratio is defined as the ratio of the vertical thickness of overburden
to the vertical thickness of suitable material.
The volume of and the contact betwenn overburden/useful materials is determined during
exploration activities eg. geological mapping, drilling, geophysics etc.
It should be noted that nature only seldomly provides a raw material of the desired chemical
composition. Normally, mixtures of various components are necessary to obtain the raw mix
suitable for the production of OPC.
10.2.1 General
Basically, the following raw material classes can be distinguished:
Main components
They contribute CaO, SiO2, Al2O3 and Fe2O3. CaO is supplied by the calcareous
(carbonatic) component
and
% CaCO3 Designation
95 - 100 high-grade limestone
85 - 95 limestone
75 - 85 marly limestone
However, by applying only chemical Information nothing is stated regarding the appearance,
lithology, type of formation, etc. of such rocks. A great variety of rocks may fulfill the above
classification (refer Table 20).
"limestone"
marly
limestone
chalk
coral
limestone
marble
"lime-sand"
shell deposits
etc.
The above can all have an identical titration value!
According to specifications for a cement raw mix, a perfectly suited raw material would
contain approx. 75 % CaCO3 and 25 % clay and sand components. Such raw Materials very
seldom occur in nature as e.g. natural cement stone".
The economic value of a Potential industrially processed cement raw material depends
largely on its conformity with the above specifications, i.e. conformity means favourable
economy. It is wrong to assume that an increased carbonate content of a calcareous raw
material would result in a higher economic value. For example, a calcareous component with
80 - 85 % CaCO3 is often preferable to a high-grade limestone with 95 - 100 % CaCO3
because fewer other raw Materials have to be added to meet the specifications.
Note
It should be pointed out that the titration method for the carbonate determination includes all
carbonates, i.e. the "titration value" is not identical with the CaCO3-content but includes
MgCO3, FeCO3, Na2CO3, etc.
Titration thus produces only guide values which have to be verified by means of total
chemical analysis.
clay "clay"
loess unconsolidated,
loose
claystone
mudstone consolidated,
siltstone compact
(slate)
shale
CaCO3
marl calcareous 65 - 75 %
marl
marl 35 - 65 %
clayey marl 25 - 35 %
marly clay 15 - 25 %
others tuff volcanic origin
ash
phyllite
slate metamorphic origin
amphibolite
In rare cases, where the abundant calcareous materials do not contain a sufficient amount of
calcium carbonate, a high-grade limestone (CaO) - corrective has to be supplied.
limestone
limestone instead of sand
clay iron ore
bauxite
Mississauga Guayaquil
98 - 100 % marly limestone 82 - 85 % limestone
0 - 2 % shale 12 - 15 % clay
1 - 3 % iron ore
Apasco
77 - 85 % limestone Geelong
8 - 22 % clay 55 % high-grade "limestone
0 - 4% sandy clay 44 % low-grade "limestone"
1 -3 % iron ore
Atocongo 1% pyrites ash
27 % limestone
73 % marl Hardegsen
92 % limestone
Darra 7 % sand
91 % coral 0.5 % iron ore
5 % sand 0.5 % gypsum (SO3)
3 % clay
1 % iron ore
Obourg
Dudfield 89 % limestone
88 % limestone 6 % sandy marl
6 % clay 1 % pyrites ash (Fe2O3)
6 % boiler ash (Al2O3) 1 % coal mine waste
0 - 1 % magnetite (Fe2O3) 3 % coal mine waste
pyrites ash (Fe2O3) containing combustibles
Wunstorf Gmunden
91 % limestone / marl 68 % limestone
1.5 % clay 29 % marl
4.54 % sand 3 % iron oxide
3 % iron ore
Constituents Designation
*
SiO2
AL2O3 main elements
Fe2O3 (oxides)
CaO
MgO
SO3 minor elements
K2O
Na2O
TiO2
Cr2O3
Mn2O3
P2O5 Trace elements
Cl
F
* plus loss on ignition
It should be mentioned that the assessment of each raw material component has to be made
with consideration of a potential raw material combination; i.e. it should not be assessed in
isolation but take into account the other components involved and the specifications for the
cement raw mix.
For example:
A limestone yielding 98 % carbonate content may contain 3.5% MgO. An isolated
assessment would result in the rejection of this Materials If the raw mix consists of 20 % clay
(say without MgO) and 80% limestone to achieve a carbonate content of 75%, a MgO
content of approx. 2.8% (4.5 % resp. when loss on ignition free) results, which is still
tolerable for most markets.
The following tables (26 - 30) display a series of analytical results of cement raw materials
and are to be interpreted according to the above criteria.
10.3.2.6 Ray Diffraction for Determination of Crystal Structure and Identification of Minerals
X-ray diffraction is a tool to supply data and information on the crystal structure not
obtainable by other techniques. In the cement industry it is applied for the identification of the
mineralogical composition of raw Materials clinker, rings, refractory Materials cement and
hydration products. It is based on the determination of the distance "d" between equispaced
planes of the crystal lattice (4.3.2.3). A set of characteristic d - values represent the
"fingerprint" of a mineral.
When a monochromatic beam of X-rays of wavelength (X of the same order of magnitude as
the distance between lattice points) falls on a crystal, the characteristic fingerprint of the
corresponding mineral is produced by reflection. This phenomenon is not a surface reflection
as with ordinary light. Rather it can be compared with the diffraction of a monochromatic
light-beam on an optical lattice. This phenomenon normally called "X-ray diffraction" is
explained as follows (Fig. 35):
Parallel to the crystal face is an infinite series of equispaced atomic planes, spaced at a
distance d. The X-rays penetrate to a depth of several million of such planes, whereby they
may undergo the same reflection as on the surface plane. If these various reflections arrive
in phase, they form a composite reflected X-ray beam. If the reflection on the multitude of
identical planes occurs out of phase, the X-ray in the crystal is absorbed and no reflection
occurs.
The diffraction method requires only small amounts (a few grams) of material.
The main application of X-radiation in the cement industry is that of X-ray fluorescence which
is used for the determination of the chemical Composition of materials (see section 15,
quality assurance, p. 15/33ff). The differences in principle (figure 38) and application
between fluorescence and diffraction are briefly summarised in Table 31a.
10.3.2.7 Polymorphism
An element or compound is defined as polymorphic if it forms two or more crystalline solid
phases differing in atomic Arrangement with identical chemical Composition The
polymorphism depends on pressure and temperature, i.e. a particular modification is only
stable under defined pressure and temperature conditions.
As a consequence of polymorphism it occurs that materials with identical chemical
Composition may exhibit different physical and chemical properties. A good example is pure
carbon in graphite and diamond form. In the graphite form the carbon is black, soft, and is
used, for example, as a lubricant or for electrodes. In the diamond form it is clear,
transparent and hard a much coveted precious stone. The lattice structures of these two
polymorphic crystalline forms are shown in Fig. 39.
Minerals with weaker lattice forces and thus better burnability are :
clay minerals
10.3.3.1 General
Mineralogy is concerned with crystalline solids all kinds, whether natural or industrial.
Crystalline solids of all kinks, whether natural or industrial. Crystalline solids come in endless
variety: the rocks of the earth's crust, the concrete of buildings and steel are a few examples
of materials composed of crystals.
SiO4-tetrahedra can be combined in different ways (Fig. 43 - 46) leading to different silicate
types:
single tetrahedron - nesosilicates : olivine and garnet groups
double tetrahedra - sorosilicates. : epidote group
rings - cyclosilicates : tourmaline, beryll
single and double chains - inosilicates pyroxene and amphibole groups
sheets - phyllosilicates: mica and clay mineral groups
framework - tectosilicates: feldspar group
The fact that so many possibilities to combine the structural unit exist, may explain why the
silicate group contains a large number of different minerals (about 500). The Si of the SiO4-
tetrahedron may be replaced by Al; and nearly all silicate structures show the ability of
exchanging cations (Na, K, Ca, Mg, Fe, Al, etc.). Within the structure of many of the resulting
lattices, there is free space left for different cations (e.g. Na, K, Ca, Al, Mg).
The amount of silicates in the earth's crust is estimated to be about 90 %.
As indicated on page 4/36, the group of silicates consists of several structural types such as:
10.3.4.1 Definition
Rocks are combinations of one or more kinds of minerals being stable under given
conditions of pressure and temperature.
Equilibrium conditions exist between the minerals of a rock as well with respect to the
surrounding of the rock (conditions of low free energy). If the conditions change for some
reason, reactions towards a new equilibrium occur. This is possible in the system itself by
reactions between minerals present in the rock or by reactions with agents introduced to the
system from outside.
In the case of rock weathering, agents from outside are added to the system (water, air);
Pressure P1 H2O Pressure P3
Temperature T1 O2 Temperature T3
Rock A Rock C
Minerals a, b, c Minerals a, b, e, f
Chemical Chemical
Composition I Composition II
The process of clinker formation can be compared, to some extent, with rock
metamorphosis.
10.4.3.1 General
The description of the relevant physical ("engineering") properties is given in 4.3.5. Basically,
limits or guidelines for physical properties can hardly be given. In practice, appropriate
process-technological methods have to be selected and adapted in order to permit optimum
processing.
A series of physical properties and their effects on various stages of the cement
manufacturing process are listed in Table 40. The influence of these properties is known
only very generally; it is almost impossible to express them quantitatively, because only a
few out of the total can be measured exactly.
1. INTRODUCTION ............................................................................................................167
2. DETAILED DRILLING CAMPAIGN: OPTIMAL DRILL HOLE PATTERN ....................167
3. GEOTECHNICAL ASPECTS .........................................................................................169
3.1 Slope failures...........................................................................................................170
3.2 Overall slope stability ..............................................................................................173
Optimal grid design (spacing, regular, irregular, etc.) can be tested with the aim to minimise
the estimation errors in the interpretation of the data by kriging (Fig. 2)
Wedge failure (Fig. 4) occurs when two discontinuities strike obliquely across the slope
face and their line of intersection daylights in the slope face. The wedge of rock resting on
these discontinuities will slide down along the line of intersection, if the inclination of this line
is greater than the angle of friction.
Circular failure (Fig. 5) occurs when the materials are very weak. For example in a soil
slope, or when the rock mass is heavily jointed or broken, (waste rock dump). The failure will
be defined by a single discontinuity surface and will tend to follow a circular failure path.
Toppling (Fig. 6) occurs when the sub-vertical layers become unsteady and fall over.
1. INTRODUCTION ............................................................................................................177
2. ECOLOGY......................................................................................................................177
3. REHABILITATION OF QUARRIES ...............................................................................177
4. EXAMPLE OF REHABILITATION .................................................................................179
4.1 Landfill of the quarry "Brengraben", Switzerland...................................................179
15. ECOLOGY
Ecology is defined as the relationship between nature (plants, animals), man and the
environment. The environment is the sum of all external forces or influences. Every plant
and animal exists within a unique and continually changing microenvironment. The
ecosystem is made up of three of ecological systems:
individual
population
ecosystem
The ecosystem, being a balance or equilibrium of the existence and the interactions between
populations, has been disrupted by man causing a profound change of these balanced
ecosystems.
In part, the quarrying activities can be disruptive, if not totally destructive to an ecosystem.
Apart from the more apparent effects of an anaesthetic pollution caused by dust and smoke,
there is also the local destruction of the flora and fauna. Usually, quarries are situated in
rocky outcrop areas, where the overburden is very thin. These areas are often the refuge of
various animals and specific plants.
What can be done do to minimise, divert or correct such disruptive effects of quarrying
activities?
Compacting was regular and there were no problems with the drainage installation.
For many years, this quarry was backfilled without any control of the quality of the materials
being dumped. With the result that the waste materials consisted of building rubble and other
disallowed products. For example :
domestic waste and detritus
scories of two chemical plants
excavation materials contaminated by acetate and acids
inert materials of demolition
However, in 1986 at the end of the landfill, groundwater investigations in the valley
confirmed that as a result of the migration of contaminated water out of Brengraben the
groundwater in the main valley was contaminated. Hazardous wastes are lixiviated by the
clean groundwater flowing thorough the overburden and limestone. This drainage water, or
deposition juice, flows into a small basin of decantation on the site before permeating back
into the groundwater system. This contaminated water contains heavy metals, which are
very dangerous to the health.
The groundwater is the potable water source for many villages in the area. Fig. 2 shows the
situation of the groundwater circulation. It was estimated that 45 l/minute of contaminated
water, which is not successfully collected in the drainage pipes, flowed into the valley.
A project to collect all the contaminated water was implemented. This involved construction
of a collection tunnel behind as well as an impermeable barrier in front of the repositry, in
order to prevent contaminated water flowing into the groundwater. The cost estimation
amounted to CHF40 - 60 Mio.
Early in 1990, signifcant gas emissions coming from the decomposition of organic materials
incommoded the people of the village near the old quarry. In order to collect this gas a
system of boreholes and pipes was installed. This consisted of a flow system for the gas
equipped with a ventilator, an analyser (continuous analysis of the gas) and a gas burner.
The quality of gas was not sufficiently good enough for commercial use (low methane).
Fig. 66 Development of costs, time, reliability and risk during raw material
investigations.
The above figures include drilling costs, geological surveying costs etc., although it is difficult
to make any general cost estimates, particularly of drilling costs, because the total length of
drilling, the characteristics of the material to be drilled, the anticipated depth of the drill holes,
water and power supply, transport and catering of drilling equipment and crew vary from one
case to the other. The drilling costs also differ between the various countries as Table 66 a
shows.
Volume of drilling required for exploration activities depends on the level of detail required.
On average the following drilling quantities should normally be considered:
Case Study
The resulting block model is an accurate inventory of the deposit, which describes the
expected quality and quantity for each point (block). It now represents one of the most
effective instruments for raw material evaluation.
In addition to the optimum raw mix composition, some technical design features for the
quarry have to be determined. These are bench height, berm width, general mining strategy
(e.g. top to bottom) and mining method (e.g. truck haulage, in-pit crushing or glory hole
system).
QED also includes the integration of these technical features in the quarry plans, such as
haul roads, ramps, dewatering ponds, waste dumps etc. In this way, the optimum long-term
mining strategy is transferred into detailed technical quarry plans.
In order to obtain a mining permit for a deposit, it is of utmost importance to show what the
future appearance of the quarry will be. Therefore, mine plans representing the future quarry
development are elaborated with QSO. These plans are then transformed into photo-realistic
3D-views using the technique of digital terrain modelling, whereby the appearance of the
quarry at any given time can be realistically shown, refer the proposed quarrying plan (Fig.
4). For this task, special commercial CAD programmes and animation software are used.
With such detailed representations of the quarry, it is possible for the authorities, and more
important for the public, to visualise the quarry development in an easily understandable
way.
The same technique can also be used to analyse the visual impact of the quarry on the
surroundings. The aim of such a visibility analysis is to achieve the increasing objective of
blending the quarry as inconspicuously as possible into the landscape.
23.5 Applicability
From a mathematical point of view, the calculation of optimum excavation plans is a
demanding task. Calculation of the block models is also a computationally intensive
undertaking, which is not at all simple. Twenty years ago, it was necessary to have large and
expensive scientific computers and well-trained personnel.
Nowadays, with the powerful low-cost PCs, most of these tasks can be carried out in close
proximity to the operation by the quarry personnel themselves. The drill hole databank, the
block model, and the excavation planning are prepared by experts, and QSO-Expert and the
QuarryMaster are implemented on-site. After a relatively short training phase (1 2 weeks)
the quarry personnel can operate and use the tools to their full extent.
It is important to remember that in addition to the high level of appropriate software products,
one of the success factors in implementing raw material planning systems is experience.
Proof of Holcim's expertise in this field is given with the successful completion of more than
150 projects, which have been carried out using computer aided raw material planning. The
present software system can be described as having been developed "by a cement
manufacturer for a cement manufacturer".
1. OBJECTIVES .................................................................................................................213
2. THE METHODS BEHIND QSO-EXPERT ......................................................................213
3. QSO-EXPERT IN PRACTICE ........................................................................................214
3.1 Graphical User Interface .........................................................................................214
4. EXPLANATION OF FIGURES 1 TO 4 ...........................................................................215
5. HARDWARE REQUIREMENTS ....................................................................................219
Figure 1:
A certain level of the deposit is represented as a coloured block map. Each square
symbolises in this case a block of 60 x 60 x 10 m3. The colours display the lime saturation.
Reddish and yellowish colours represent high grades, greenish and bluish ones low grades.
Any variable which is contained in the block model can be shown. Thus, the deposit
inventory is displayed in an impressive and easily understandable way.
The "Planning" menu is opened and allows the selection of various activities such as:
definition of product (raw mix) requirements, specification of mining rules and constraints,
checking mining feasibility, computing optimal deposit utilisation strategies, planning actual
quarry schedules and doing short-term production scheduling by building-up a pre-blending
bed.
This figure shows the results of a scheduling run. The window "mix offered" describes the
geological reserves on level 6 (left window). The right window "optimiser" describes
chemistry and maximum quantity of the raw mix achieved. Quantities of the required
correctives (clay, iron-ore and sand, etc.) are reported as well. The dotted blocks (left
window) are the blocks which have to be mined to achieve the reported raw mix.
Each column in the left window represents a mining face, each red block represents blasted
material, known in quality and quantity. There are 50 blasts with 355'000 tons of material
(window "mix offered"). The four blocks marked with a black dot plus some correctives result
in 33'000 t of raw mix in the desired quality, corresponding to the capacity of one
preblending bed.
5. HARDWARE REQUIREMENTS
QSO-Expert runs on PCs with Intel 386 or 486 processors (with arithmetic coprocessor), 4
MB RAM, colour display (VGA) and an A4 colour plotter. Operating system is MS-
WINDOWS 3.1 or higher.
1. Introduction...................................................................................................................222
2. QUARRY DESIGN .........................................................................................................222
2.1 Maximum Final Depth .............................................................................................223
2.2 Overall Slope Angle for Final Pit walls ....................................................................223
2.3 Bench Height...........................................................................................................224
3. Quarry Engineering ......................................................................................................225
3.1 Quarry System ........................................................................................................225
3.1.1 Ripping .............................................................................................................225
3.1.2 Dozing ..............................................................................................................226
3.1.3 In-Pit Crushing .................................................................................................227
3.1.4 Glory hole.........................................................................................................228
3.2 Haul road design .....................................................................................................228
3.2.1 Grade ...............................................................................................................229
3.2.2 Width ................................................................................................................229
3.2.3 Location............................................................................................................229
3.2.4 Safety ...............................................................................................................229
3.2.5 Calculation of truck capacity ............................................................................229
3.3 Dewatering ..............................................................................................................229
4. Visualisation of quarry development..........................................................................230
5. Conclusion ....................................................................................................................231
6. REFERENCES ...............................................................................................................232
The quarry plans show the future development of the quarry in all necessary detail. They are
used for
strategic decisions (acquisition of property, location of crushers, construction of haul
roads and waste dumps, investment for mobile equipment).
control of exploitation progress
environmental related planning (rehabilitation, visibility analysis, etc.) and
the mining permission procedure.
2. QUARRY DESIGN
Before starting with the development of long-term mine plans, some basic design features
for the quarry have to be set up. The design features determine the geometrical shape of the
quarry. The main parameters are:
quarry limits
maximum final depth
overall slope angle
bench height
From the aspect of mining cost, the final depth is often limited down to:
the level of the crusher location to avoid up-hill haulage with the loaded trucks or
the level of the dewatering drain to avoid pumping.
The final pit depth can also be limited by the authorities (protection of ground water
horizons).
The resisting forces depend on the friction angle and the cohesion of the material. As a first
estimation, we calculate, for the final pit walls in limestone quarries, an overall slope angle in
the range of 50 to 60. Depending on the exact geological conditions (joints and fissures)
and the influence of water, the maximum angle can be lower or higher. Different types of
rock have different stabilities. Therefore, a severe geotechnical study is recommended to
determine the overall slope angle. This is also most relevant for the waste dump.
Slope angle for a bench system during quarry operation is normally much lower than the
final angle because a certain bench width is required for the manoeuvrability of the mobile
equipment.
3. QUARRY ENGINEERING
QED also includes engineering work for quarry planning such as
selection of a quarry system
haul road design
dewatering concept
3.1.1 Ripping
As an alternative to a drilling/blasting operation ripping can be used in soft rock (Fig.2).
Ripping has the advantages of
no permit, transport, storage and handling of explosives are necessary
no ground vibrations, no air blast occur
no specially trained personnel required and
a continuous operation
The main question is: Can the rock be ripped? As a rule of thumb it can be stated that
material up to a seismic velocity of 2.000 m/s is rippable, but other factors such as fractures
and weaknesses, weathering, stratification and brittleness are also very important.
A rock mechanic analysis, a geological site investigation and a seismic analysis may give
good indications, but only a site test can prove the rippability of the rock. Finally, a cost
comparison has to show whether ripping provides cost benefits.
3.1.2 Dozing
Normally the haul road leads to all benches, so that the rock can be loaded and transported
from each bench. As an alternative, the muckpile is pushed by a dozer over the crest of the
bench and then loaded at the pit bottom into trucks.
The advantages of this method are that the haulage distances and the required number of
trucks are reduced, and the construction of a wide haul road to the upper benches is not
necessary. This results in low mining costs. The disadvantages are: reduced safety, poor
quality control by segregation, selective mining is difficult, less flexibility in face advance,
more dust and more fines.
3.2.2 Width
The width of the haul road should be 3 - 3.5 times that of the truck width to allow safe two
lane truck traffic. The space required for the installation of protection berms and drains must
also be added to the total width of the haul road.
3.2.3 Location
Location of the haul road is perhaps the most difficult part. The final haul road should be
established as soon as possible to avoid construction of temporary roads, and the line of the
haul road should result in short haulage distances. A good practice is to align the haul road
along a final slope, because the haul road design influences the long-term planning, both of
which must be made in accordance with each other.
When deciding on the location of the haul road, it is also important to position the road
relative to the usable / waste contact. The haul road width normally exceeds final berm
width, and consequently if the haul road is positioned in such a way that no reserves are to
be lost, then additional waste has to be removed. The alternative is to select a location on
usable reserves so that no additional waste removal is required. The positioning of the road
will be a compromise that balances additional costs for waste removal against losses on
reserves.
Sharp and steep curves on the road should be avoided as they reduce the travelling speed
and increase wear and tear on tyres and chassis. Curves should be designed with a super-
elevation to counter balance the centrifugal force.
3.2.4 Safety
Safety is an important factor on haul road design. When planning curves and hills, emphasis
has to be laid on good visibility along the haulage route. The trucks should be able to stop
within the range of visibility (Fig. 11). On long, steep haul roads break failures have to be
reckoned with, leading the down-hill traffic lane on the hill side of the road. Middle berms or
emergency exits are preventative measures against fatal accidents.
3.3 Dewatering
In areas with significant rainfall, dewatering is important for a safe and efficient quarry
operation. Therefore, a good quarry design has to include a dewatering concept. That
means the benches need a slight inclination in such a way that the water runs off in a certain
direction from where it can be drained off to the quarry sump.
The drains and the sump must be designed with sufficient capacity to handle maximum
expected rainfall.
Fig. 5 Aerial view of a quarry. Clearly visible are the position of the crusher
(small quarry, top left), the access road and the quarry wall with a height
of up to 250m.
Fig. 6 Quarry at ground-level view. The main issues and the camouflage wall
are visible.
Figure 5 Shows an aerial view of a quarry. This perspective is particularly suited for the
clarification of excavation concepts, from an operational viewpoint. Clearly visible in the
figure are the position of the crusher ('small quarry' top left), the access road and, in
particular, the impressive quarry wall with a height of up to 250m.
Figure 6: Shows another quarry. Unlike the first example, this is a normal ground-level view.
Here the main issues are visibility and the camouflage wall. These topics chiefly interest
authorities and the general public.
It must be emphasised that all visual presentations are based on exact plans, which are
accurate in every detail. These plans are based on CADE (Computer Aided Deposit
Evaluation) and QSO (Quarry Scheduling Optimisation)'. They optimally satisfy long and
short-term objectives. The objectives are steady supply of good-quality raw materials, with
maximum deposit utilisation and lowest possible production cost.
QED as a further technique allows 3-D modelling and visualisation of the quarry
development. With the method of QED, the planning becomes clear and easily
understandable - clear and understandable for both the expert and the general public.
The final decision on further investments (for example for a detailed drilling campaign) will
not be reached until later, after the prospects for an excavation licence are positive.
5. CONCLUSION
To bring raw materials management into operation the following steps have to carried out:
The general layout of the quarry and a suitable mining procedure has to be determined.
A long-term strategy for the quarry development has to be defined, which is guided by
the optimum use of the deposit.
More detailed periodical quarry plans have to be developed and transferred into detailed
technical quarry maps.
6. REFERENCES
BAUMGARTNER W., Computerised raw materials management - developments and
progress. World Cement, Vol. 21, no. 5, pp. 207-213 (1990).
1. Introduction...................................................................................................................234
2. The tasks of a Quarry Manager ...................................................................................234
3. Requirements for the new planning tool ....................................................................234
4. Holcim's QuarryMaster ................................................................................................235
5. Benefits .........................................................................................................................239
6. QuarryMaster and Cross-Belt- Analyser ....................................................................240
The ultimate aim of production scheduling in the quarry is to produce a raw mix, which fulfills
perfectly the requirements of the process. Due to the generally very complex nature of our
natural deposits, this is a difficult task. But how can an integrated computerised planning tool
help us to get closer to this target?
The essential factor required to achieve all of these objectives at the same time, is proper
production planning.
Furthermore, we require that the tool be easy-to-use in order to avoid additional working
time.
The user defines the blasts interactively with the mouse on the screen in the same way as
he would do with a pen on a map (Fig. 2). After blasting, the topography is automatically
updated, and so the model always shows the actual state of the quarry. Quality data from
blastholes or other samples are automatically imported from the laboratory. They can be
assigned to the blast simply with a click of the mouse, the tonnages and the chemistry of the
blasts are calculated automatically (Fig. 3).
QuarryMaster enables you to produce a uniform and correct raw mix at the best point -
right in the quarry.
Complex raw mix composition can be produced because the system is able to control
multiple quality parameters simultaneously as well as the use of several correctives.
With an accurate, computer controlled crusher feed, the correctives consumption can be
reduced, which results in significant cost savings.
Due to the fact that the working hours required to fill a preblending pile can be
minimised, there is more flexibility in the quarry operation.
However, a Cross-Belt-Analyser provides very accurate and reliable information about the
quality of the material already mined. So the Cross-Belt-Analyser can be used as an on-line
control instrument for production plans developed by the QuarryMaster. When QuarryMaster
is combined with a Cross-Belt-Analyser they work together as a rapid control loop and allow
the production of preblending piles right on the set point (Fig. 5).
7. CHEMICAL FORMULAE
The chemical formula indicates the elements occurring in a chemical compound:
for a molecular compound, type and absolute number of elements in a molecule are
given
H2O O2 C6H6
water oxygen benzene
for a mineralogical compound, type and relative number of elements are given
SiO2 CaO CaCO3 Ca3SiO5
quartz lime calcite alite
Note: In mineralogical compounds, the elements need not necessarily occur in simple
numerical ratios (impurities, solid solution)
in the cement chemistry, shorthands are often used:
CaO SiO2 Al2O3 Fe2O3 SO3 H2O
C S A F S H
8. MINERALOGICAL COMPOSITION
Clinker
Alite C3S 58%
Belite C2S 23%
Aluminate C3A 9%
Ferrite C4AF 7%
Periclase MgO 1%
Arcanite K2SO4 1%
Free lime CaO 1%
9.1 Titration
Content of carbonates as determined by acid-base titration, expressed as CaCO3
% Titration = 1.786 CaO + 2.48 MgO
Applied for:
Limestone
Marl
Raw Meal
CaO x100
LS=
2.80SiO2 + 1.18Al 2O3 + 0.65Fe2O3
or
CaO
LSF =
2.8SiO2 + 1.2 Al 2O3 + 0.65Fe2O3
The LS is a measure to which extent the CaO-richest compounds C3S, C3A and C4AF can
be formed without the necessary presence of free lime. At LS > 100, free lime will
unavoidably be present after burning.
Applied for:
Raw meal
Clinker
Cement: neat OPC only
CaO = CaOtotal - 0 7 SO3
Usual range in clinker: 85 - 100
Note: The influence of MgO can be accounted for
(CaO + 0.75MgO )x100
LS=
2.80SiO2 + 1.18 Al 2O3 + 0.65Fe2O3
max. 2 % MgO may be introduced in formula (not applied in cement specifications)
9.5 Na2O-equivalent
Total alkali content, expressed as Na2O
Na2O-equivalent = Na2O ~ 0.658 K2O
Note: Limit for low alkali cement
Na2O-equiv. s 0.6 %
Applied for Clinker
Cement
Type I Portland
no restrictions regarding clinker minerals
Type II Portland with moderate sulphate resistance
C3A max. 8 %
Type III Portland with high early strength
C3A max. 15 %
Type IV Portland with low heat of hydration
C3S max. 35 %
C2S min 40%
C3A max. 7 %
Type V Portland with high sulphate resistance
C3A max. 5.0 %
C4AF + 2 C3A max. 25 %
or
C4AF + C2F max. 25 %
Titration ..........
LS .......... ..........
SR .......... ..........
AR .......... ..........
Na2O-equiv. ..........
C3S ..........
C2S ..........
C3A ..........
C4AF ..........
Mix Design
1. MIX DESIGN ................................................................................................................ 252
2. Program for Optimal Raw Mix Design...................................................................... 270
1. GENERAL ......................................................................................................................253
2. DEFINITION OF CRITERIA FOR MIX CALCULATION.................................................253
3. PRINCIPLES AND METHODS OF MIX PROPORTIONING..........................................256
3.1 X-Pattern .................................................................................................................256
3.2 Manual Calculation..................................................................................................257
3.3 Graphical Methods ..................................................................................................257
3.4 Programmable Calculator........................................................................................257
3.5 Computer Optimisation............................................................................................257
4. PRINCIPLES OF RAW MIX ASSESSMENT .................................................................262
4.1 Mix Type..................................................................................................................263
4.2 Comparison of Raw Mix with Standard Specifications ............................................263
4.3 Assessment of the Mineralogical Composition of Cement Raw Mixes. ..................265
4.4 Assessment of Raw Mixes with regard to Cement Production and Choice of Process
266
4.5 Evaluation of Laboratory Test Results ....................................................................267
Table 41 shows the influence of chemical requirements on the choice of raw materials.
The proportioning of raw mixes for ordinary Portland cement is mostly based on the following
specific criteria:
MgO
Lime standard or lime or saturation factor (or C3S)
Silica ratio
Alumina ratio
17.1 X-Pattern
The x-pattern represents a linear estimation of two raw material components by selecting the
anticipated titration value (total carbonate content) of the potential raw mix as basis.
or as a numerical example.
Table 43
These limits should not be regarded as isolated figures but rather as part of a multi-
component system (including contributions from the fuel). Particular attention should be
given to the systems of:
K2O ----- Na2O ----- SO3
K2O ----- Na2O ----- Cl
whereby an effort should be made to achieve equalised alkali sulphur balance in order to
prevent problems in the kiln system.
Only a few deleterious constituents are limited by specifications, e.g. the MgO and the total
alkali-content (for low-alkali clinker). The others are not specified (limited) but practical
experience with processing and quality requirements of the product (clinker/cement) dictate
their quantitative limits.
18.4 Assessment of Raw Mixes with regard to Cement Production and Choice of
Process
As discussed previously, the properties of the raw materials, i.e. raw mixes, largely influence
the choice of process in general, and the various stages of production. Tables 51 and 52
indicate the most significant relations and functions.
It becomes obvious that the clay mineral content is of paramount importance form many
aspects of production.
Table 52 Summarises the most important raw mix properties influencing the
choice of process.
Table 52 only summarises raw mix aspects. However, other factors, e.g.
seasonal fluctuations of moisture content
transport, haulage etc.
are, of course, also determining factors in the choice of process.
1. MIXOPT..........................................................................................................................271
1.1 OPTIMAL RAW MIX DESIGN ON PERSONAL COMPUTER.................................271
2. PROGRAM FOR OPTIMAL RAW MIX DESIGN............................................................271
2.1 FACILITIES .............................................................................................................271
2.1 FACILITIES
BLENDING OF COMPONENTS
DETERMINATION OF PRODUCT CHARACTERISTICS
Raw Max
Clinker
Cement
Slurry Preparation
1. Rheology 'Slurry preparation' ....................................................................................... 279
2. Materials Technology Slurry preparation ..................................................................... 300
1. INTRODUCTION ............................................................................................................280
1.1 Ideal solids ..............................................................................................................281
1.2 Liquids .....................................................................................................................281
2. LAW OF VISCOSITY .....................................................................................................283
2.1 Shear stress ............................................................................................................283
2.2 Shear rate................................................................................................................283
2.3 Dynamic viscosity....................................................................................................284
2.4 Kinematic viscosity ..................................................................................................284
3. FLOW AND VISCOSITY CURVES ................................................................................285
3.1 Viscosity parameters ...............................................................................................285
3.2 Flow Curve ..............................................................................................................285
3.3 Viscosity Curve........................................................................................................287
4. SUBSTANCES ...............................................................................................................288
4.1 Newtonian liquids ....................................................................................................288
4.2 Non-Newtonian liquids ............................................................................................288
4.3 Rheonexy ................................................................................................................294
5. BOUNDARY CONDITIONS ...........................................................................................295
5.1 Laminar flow ............................................................................................................295
5.2 Steady state flow .....................................................................................................295
5.3 No slippage .............................................................................................................295
5.4 Samples must be homogeneous.............................................................................295
5.5 No chemical or physical changes in the sample during testing...............................295
5.6 No elasticity .............................................................................................................295
6. ROTATIONAL VISCOMETERS .....................................................................................297
6.1 Indication of different models ..................................................................................297
3. INTRODUCTION
Several aspects to describe the slurry properties are known, some of them are mentioned
below:
Flow behaviour
Granulometry
GrindabiIity
Chemistry
Pumpability
Slump
In this paper the aspects of rheology are considered. Rheology describes the deformation of
a body under the influence of stresses.
Ideal solids deform elastically. The energy of deformation is fully recovered when the
stresses are removed.
Ideal fluids deform irreversibly - they flow. The energy of deformation is dissipated into the
fluids in the form of heat, and it cannot be recovered just by releasing stresses.
The Youngs modulus in this equation is a correlating factor linked mainly to the chemical-
physical nature of the solid involved. It defines the resistance of the solid against
deformation.
3.2 Liquids
The resistance of a fluid against any irreversible positional change of its volume elements is
called viscosity. To maintain flow in a fluid, energy must be added continuously.
Viscometry deals specifically with the measurement of the flow behaviour of liquids including
those showing a viscoelastic behaviour.
3.2.1.4 Flow between tow parallel plates or between a come and a plate
When one of the two is stationary and the other rotates. This model resembles twisting a roll
of coins causing coins to be displaced by a small angle with respect to adjacent coins. This
type of flow is realised in rotational viscometers with plate/plate or cone/Plate sensor
systems.
The parallel plate model helps to define both shear stress and shear rate:
Viscosity Curve
Viscosity measurements lead always first to the flow curve. Its results can then be
rearranged mathematically to allow plotting the corresponding viscosity curve. The different
types of flow curves have their counterparts in types of viscosity curves.
6.2.1 Pseudoasticity
Very many liquids show drastic viscosity decreases when the shear rates are increased from
low to high levels.
Technically this can mean that for a given force or pressure more material can be made to
flow, or the energy can be reduced to sustain a given flow rate. Materials which are thinning
due to increasing shear rates are called "pseudoplastic". Very many substances such as
emulsions, suspensions, or dispersions belong to this group.
6.2.1.1.2 Disintegration
Shear can also induce irregular lumps of aggregated primary filler particles to break up and
this also helps a material with such a filler to flow faster at a given shear stress.
6.2.1.1.3 Reversibility
For most liquid materials the shear thinning effect is reversible - often with some time lag -
i.e. the liquids regain their original high viscosity when the shearing is slowed down or is
even terminated: the chain-type molecules return to their natural state of non-orientation,
deformed droplets return to ball-shape and the aggregates reform due to the Brownian
motion.
At the low shear rate range the Brownian movement of molecules keeps all molecules or
particles at random in spite of initial effects of shear orientation. At very low shear rates
pseudoplastic liquids behave similarly to Newtonian liquids having a defined viscosity
independent of shear rate. Then follows a shear rate change when the shear rate induced
molecular or particle orientation by far exceeds the randomising effect of the Brownian
movement: the viscosity drops drastically. Finally the viscosity approaches a finite level.
Going to even higher shear rates cannot cause further shear thinning: The optimum of
perfect orientation has already been reached. In the low and in the high shear rate ranges -
called the first and second Newtonian ranges - the viscosity even of non-Newtonian liquids is
more or less independent of shear rate.
6.2.2 Dilatancy
There is one other type of material characterised by a shear rate dependent viscosity:
"dilatant" substances increase their viscosity whenever shear rates increase.
6.2.3 Plasticity
It describes pseudoplastic liquids which additionally feature a yield point. Plastic liquids can
be classified with good reasoning to belong to both liquids and solids. They are mostly
dispersions which at rest can build up an intermolecular/interparticle network of binding
forces (polar forces, van der Waals forces, etc.). These forces restrict positional change of
volume elements and give the substance a solid character with an infinitely high viscosity.
Forces acting from outside, if smaller than those forming the network, will deform the shape
of this solid substance elastically. Only when the outside forces become so big that they can
overcome the network forces - surpass the threshold shear stress calls "yield point" - does
the network collapse. Volume elements can now change positions irreversibly: the solid
turns into a flowing liquid.
Typical substances showing yield points: oil well drilling muds, greases, lipstick masses,
toothpastes. Plastic liquids have flow curves which intercept the ordinate not at the origin,
but the yield point level of 0.
6.2.4 Thixotropy
This term describes a rheological phenomenon of great industrial importance. It calls for
some explanations in simplified terms of an otherwise often very complex molecular of
particle interaction:
In pseudoplastic liquids thinning under the influence of increasing shear depended mainly on
the particle/molecular orientation or alignment in the direction of flow. This orientation will
again be lost just as fast as orientation came about in the first place.
Plotting a flow curve with a uniformly increasing shear rate - the "up curve" - one will find that
the "down-curve" plotted with uniformly decreasing shear rates will just be superimposed on
the "up-curve".
In the flow curve the "up-curve" is no longer directly underneath the "down-curve".
The hysteresis now encountered between these two curves surrounds an area "A" that
defines the magnitude of this property called thixotropy. This area has the dimension of
"energy" related to the volume of the sample sheared which indicates that energy is required
to break down the thixotropic structure.
6.2.4.1 Mechanism
It is typical for many dispersions that they not only show this potential for orientation but
additionally for a particle/molecule-inter-action. This will lead to bonds creating a three-
dimensional network structure which is often calls a "gel". In comparison to the forces within
particles or molecules, these bonds - they are often hydrogen or ionic bonds - are relatively
weak: they rupture easily, when the dispersions is subjected to shear over an extended
period of time.
When the network is disrupted the viscosity drops until it asymptotically reaches the lowest
possible level for a given constant shear rate. This minimum viscosity level describes the
"sol"-status of the dispersion. A thixotropic liquid is defined by its potential to have its
structure reformed, when the substance is allowed to rest for an extended period of time.
The change of a gel to a sol and of a sol to a gel is reproducible any number of times.
6.3 Rheonexy
Rheopective liquids are characterised by a viscosity increase related to the duration of
shear. When these liquids are allowed to rest they will recover the original - i.e. the low -
viscosity level. Rheopexy and thixotropy are opposite flow properties.
7.3 No slippage
The shear stress applied must be transmitted from the moving plate across the liquid
boundary layer into the liquid. In case that adherence between the moving plate and the
liquid is insufficient to transmit the shear stress - the moving plate slips above the non-
moving liquid sample - any test results will be meaningless. Problems with slippage often
arise with fats and greases.
7.6 No elasticity
Samples should be purely viscous. Very many samples such as polymer melts or polymer
solutions show a viscous and an elastic response to shear stresses or shear rates. When
the latter becomes sizable test results can no longer be evaluated in terms of viscosity.
In rotational viscometers with coaxial cylinder sensor systems for some samples the elastic
response to shear may be so great as to "suck" all the substance out of the annular gap.
Elasticity is a characteristic property of a sample which cannot be subdued by any means.
When measuring the viscosity of viscoelastic samples, the maximum of shear rate must be
limited to keep the normal stresses from becoming too large so that they ruin the test results.
Couette Viscometers
1. INTRODUCTION ............................................................................................................301
2. RHEOLOGY ...................................................................................................................303
2.1 Types of viscosity ....................................................................................................310
2.2 Slurry Thinners ........................................................................................................316
2.3 Viscosimetry ............................................................................................................319
3. PRODUCTION COST ANALYSIS .................................................................................322
3.1 Technical functions..................................................................................................323
3.2 Optimisation ............................................................................................................329
In a wet-process kiln, a reduction in slurry moisture results in a reduction in heat use, and
since both the amount of water vapour and the amount of combustion products are
Several aspects to describe the slurry properties are known, some important ones are
mentioned below:
Water content
Mineralogy
Cement Manufacturing Course Version 2005 Volume 1 - Page 302
Flow behaviour
Granulometry
Grindability
Chemistry
Pumpability
Slump
Specific grinding energy
10. RHEOLOGY
Rheology is the discipline describing the most important slurry property in a qualitative and
quantitative manner.
There are off-line (laboratory) and on-line (process control) methods available.
Rheology describes the deformation of a body under the influence of stresses.
Ideal solids deform elastically. The energy of deformation is fully recovered when the
stresses are removed.
Ideal fluids deform irreversibly - they flow. The energy of deformation is dissipated into the
fluids in the form of heat, and it cannot be recovered just by releasing stresses.
Isaac Newton was the first to find the basic law of viscosity describing the flow behaviour of
an ideal liquid:
The parallel plate model helps to define both shear stress and shear rate:
Shear stress
A force F applied to an area A being the interface between the upper plate and the liquid
underneath leads to a flow in the liquid layer. The velocity of flow that can be maintained for
a given force will be controlled by the internal resistance of the liquid, i.e. by its viscosity.
F (force ) N
= = =Pa(Pascal )
A(area ) m 2
Shear rate
The shear stress r causes the liquid to flow in a special pattern. A maximum flow speed Vmax
will be found at the upper boundary.
The speed drops across the gap size y down to Vmin = 0 at the lower boundary contacting the
stationary plate. Laminar flow means that infinitesimally thin liquid layers slide on top of each
other, similar to cards in a deck-of-cards. One laminar layer is then displaced with respect to
the adjacent ones by a fraction of the total displacement encountered in the liquid between
both plates.
In its general form the shear rate D is defined by a differential:
dv
D=
dx
m / s 1 1
D= = [s ]
m s
In case of a linear speed drop across the gap the differential in the equation above can be
approximated by
Generally it can be pointed out that the higher the water content, the lower the viscosity.
There are little restrictions with respect to the quality of the utilised water, i.e. water of many
origin/source and quality can be used, such as:
tap water
industrial water/industrial waste liquids
sewage water
slightly brackish water.
The only quality aspects which have to be controlled are:
content of corrosive elements (C1, 0 )
contents of harmful or poisoneous elements with regard to process, product and waste
gases (C1, F, B, organic substances, etc.)
content of smelling compounds in the waste water, etc.
B) Slurry Fineness
The fineness of slurry fluctuates in a wide range as demonstrated in the following diagram:
The replacement of clay minerals, for instance with fly ash of thermal power plants, can
reduce the water content significant by increased slurry flowability.
Other factors such as degree of fineness and grain size distribution of the raw mix, etc., also
influence the slurry water-content, but the plastic clay mineral-content seems to be
predominant.
Viscosity Diagrams
Flow Curve
Cement Manufacturing Course Version 2005 Volume 1 - Page 308
The correlation between shear stress and shear rate defining the flow behaviour of a liquid is
graphically displayed in a diagram of T on the ordinate and D on the abscissa. This diagram
is called the "Flow Curve".
The most simple type of a flow curve is shown below. The viscosity is assumed to be
constant and independent of D.
Viscosity Curve
Another diagram is very common: is plotted versus D. This diagram is cal-led the "
Viscosity Curve":
Viscosity measurements lead always first to the flow curve. Its results can then be
rearranged mathematically to allow plotting the corresponding viscosity curve. The different
types of flow curves have their counterparts in types of viscosity curves.
Non-Newtonian liquids
All other liquids not showing this simple "ideal" flow behaviour are called ''non-Newtonian.
They outnumber the ideal liquids by far.
A) Pseudoplasticity
Many liquids show drastic viscosity decreases when the shear rates are increased from low
to high levels.
Technically this can mean that for a given force or pressure, more material can be made to
flow or the energy can be reduced to sustain a given flow rate. Materials which are thinning
due to increasing shear rates are called "pseudoplastic. Substances such as emulsions,
suspensions, or dispersions belong to this group.
Shear thinning of pseudoplastic liquids is not uniform over the range of very low to very high
shear rates:
At the low shear rate range the Brownian movement of molecules keeps all molecules or
particles at random in spite of initial effects of shear orientation. At very low shear rates
pseudoplastic liquids behave similarly to Newtonian liquids having a defined viscosity
independent of shear rate. Then follows a shear rate change when the shear rate induced
molecular or particle orientation by far exceeds the randomising effect of the Brownian
movement: the viscosity drops drastically. Finally the viscosity approaches a finite level.
Going to even higher shear rates cannot cause further shear thinning: The optimum of
perfect orientation has already been reached. In the low and high shear rate ranges - called
the first and second Newtonian ranges - the viscosity even of non-Newtonian liquids is more
or less independent of shear rate.
B) Dilatancy
The hysteresis now encountered between these two curves surrounds an area A" that
defines the magnitude of this property called thixotropy. This area has the dimension of
"energy" related to the volume of the sample sheared, which indicates that energy is
required to break down the thixotropic structure.
Mechanism
It is typical for many dispersions that they not only show this potential for orientation but
additionally for a particle/molecule-inter-action. This will lead to bonds creating a three-
dimensional network structure which is often called a "gel". In comparison to the forces
within particles or molecules, these bonds - they are often hydrogen or ionic bonds - are
relatively weak: they rupture easily, when the dispersions are subjected to shear over an
extended period of time.
When the network is disrupted the viscosity drops until it asymptotically reaches the lowest
possible level for a given constant shear rate. This minimum viscosity level describes the
"sol"-status of the dispersion. A thixotropic liquid is defined by its potential to have its
structure reformed, when the substance is allowed to rest for an extended period of time.
The change of a gel to a sol and of a sol to a gel is reproducible any number of times.
E) Rheopexy
Rheopective liquids are characterised by a viscosity increase related to the duration of
shear. When these liquids are allowed to rest they will recover the original - i.e. the low -
viscosity level. Rheopexy and thixotropy are opposite flow properties.
Slurry Flow Curve
A typical cement raw slurry flow curve is shown below.
This curve clearly demonstrates the plastic thixotrope characteristics of a typical cement raw
slurry.
The slurry particles consists of small flat plates. The areas are occupied with negative
electronic change, the corners are positively charged. Stable electrostatic bridges between
areas and corners reduces the flowability of the slurry .
Negatively charged thinners (e.g. polyelectrolyts) forms a protective layer around the
positively charged particle corners and lowers the slurry viscosity. In case of overdossage or
wrong evaluated thinner the opposite effect can occur: the polyelectrolyte forms bridges
between the particles and increase the stickiness of the slurry (flocculation).
Carbon dioxide
Tensides
anion-active
non-ionogenic
cation-active
Combinations of thinning agents
Phosphates + sodium or calcium salts
phosphate + sodium carbonate
phosphate + sodium hydroxide
phosphate + calcium hydroxide
Water glass + soluble salts of humic or lignic acid
Citrate + tartrate
Carbon dioxide + sodium tripolyphosphate (STPP)
Triethanolamine + gallic acid
Sulfite lye + soda
Experience with Slurry Thinning
From tests on thinning of both industrial and laboratory raw slurries, the following conclusion
can be drawn :
A large number of thinning agents produce the desired effect.
Not every thinning agent is suited for every type of slurry.
Under certain conditions, a combination of thinning agents added as a mixture or
successively produce a better effect than one single thinning agent.
The actual effect of a thinning agent for specific conditions cannot be predicted in
advance so that tests in laboratory and in plant have to be conducted (synergism-effect,
non-linearity).
Cement Manufacturing Course Version 2005 Volume 1 - Page 318
The adding quantities vary from case to case.
The water reduction usually varies in absolute terms between 2 and 7%.
Slurries with an initial water content between 33 and 43% have been most frequently
treated with thinners.
The mineralogical composition of a raw slurry plays an important role.
The pH value may be a decisive factor determining the thinning effect.
Due to local availability and for economical reasons, the most frequently used thinners
are soda, water glass, STPP, sulfite lye and lignin-sulfonate.
The fineness of a raw slurry is of little or no importance as regards the action of the
thinners.
The existing kiln systems usually require no adaptations with regard to chains and filters
provided that the water content of the slurry remains above 33 - 35%. However, some
plant adaptations are usually necessary, if the water content of thinned industrial raw
slurries is low (30 - 33%).
Under certain conditions, piston pumps should be installed instead of centrifugal pumps
and as many bends as possible should be eliminated from the slurry piping, especially if
the cement raw slurry shows rheopexic behaviour.
For each % of water saved. 60 - 100 kJ are economised during the burning process.
A sequential addition is important for a combination of thinners. First of all, a thinner
must be added to adjust the pH and once this effect is reached, a second thinner can be
added; afterwards, a third thinning agent can be used if necessary. If all of the thinners
are added at the same time and place, generally the effect is not the same as with a
sequential addition.
The use of a thinner should be economical, that is, the price of a thinner plays a decisive role
(see also chapter "Cost Analysis). It also has to be taken into consideration that specific
thinners are, or should be preferred depending on the country or location of the plant
(molasses from the sugar industry, sulfite lye from the paper mills).
10.3 Viscosimetry
Laboratory methods
Target of the laboratory investigation is the reduction of the water content and/or the
reduction of the yield value (f1 to f2) and the viscosity (71 to 22). A target could also be to
decrease the slurry water content and to keep yield value and viscosity constant.
As mentioned before, reduction of the water content leads to lower thermal and mechanical
energy demand, reduction of yield value and viscosity to better pumpability and dewatering
property (half wet process).
For the purpose of optimizing the slurry viscosity it is indicated to make trials with different
thinner admixtures, concentrations, retention time and temperature levels in the laboratory.
Recent developed method of statistical experimental planning helps to minimise laboratory
work drastically.
The target is to find out a quantitative relationship between viscosity and above mentioned
parameters. The assumption of 3 experimental level of above 6 influencing parameters
means
36 = 729 experiments
The inner or the outer cylinder is subjected to a defined shear stress or a defined torque
while the other cylinder is held at rest. One can now measure the rate of rotation or shear
rate resulting.
b) Preselect D: look for
c) The inner or the outer cylinder rotates at a defined rotational speed while the other
cylinder is held at rest. One can now measure the resulting shear stress or torque. This
is the most common design for rotational viscometers.
The inner cylinder - often called the "rotor - rotates at a defined speed. The outer
cylinder - often called the "cup" is held at rest. The rotating inner cylinder forces
the slurry in the annular gap to flow. The resistance of the slurry being sheared
between the stationary and rotating boundaries results in a viscosity related
torque working on the inner cylinder which counteracts the torque provided by the
drive motor. A torque sensing element - normally a spring that twists as the result
of the torque - is placed between the drive motor and the shaft of the inner
cylinder. The twist of the torque spring is a direct measure of the viscosity of the
slurry tested.
Most viscometer models made world-wide are Searle types. One reason for this
tendency is that the good temperature control required for viscosity
measurements is more easily accomplished when the outer cylinder does not
rotate. Searle type viscometers are limited when low viscous samples have to be
Couette system
The outer cylinder rotates at a defined speed. It forces the slurry sample in the
annular gap to flow. The resistance of the slurry being sheard, transmits a
viscosity related torque onto the inner cylinder, which would induce it also to
rotate. This torque is measured by determining just what counteracting torque is
required to hold the inner cylinder at stand still. Couette type viscometers are
more stable with respect to centrifugal forces.
In the laminar flow zone no relation between pipe surface quality and resistivity number
exists, whereas the influence in the turbulent flow zone increase drastically.
In the laminar flow zone the simplified approach to evaluate the flow resistivity number is
possible by applying the "Hagen Poiseulle's low":
64
=
Re
With the flow resistivity number it is easily possible to compute the pressure drop of a
simplified piping system as follows:
1 v2
Pr essuredrop=
d 2g
Pressure drops results from flow resistivities, elevation differences (geodatical) and velocity
difference between input and output of the piping system.
L V2 v 2 V( ou ) V( IN )
d
p=
2g
+ 2g + 2g
With this relationship the function of "Pressure drop" depending on slurry viscosity (water
content) can be given quantitatively:
Viscosity and Velocity depends on water content of slurry, so the following relation can be
formed:
Q* production, pump efficiency and pump characteristic dictates the pump evaluation and
the power demand. The area "A" represents the pumping power demand, the value has to
be minimised.
This consideration leads to a complex, multivariable optimisation. It is worthwhile doing it in
face of the great saving potential of investment cost and mechanical energy.
11.1.3 Filtration
Filtration is defined as a "solid - liquid - separation - technique", i.e. separation of a cement
raw slurry into a liquid phase (the filtrate) and a solid phase (filter cake) with the aid of a filter
which can only be penetrated by liquids. This process is applied in the so called "semi-wet
process".
Kozeny - Carmans law
1 p E3 A
Q *= k 2
S (1 E ) e
2
k System constant
A Filtration Area
S Specific surface of solids
E Porosity
The equation demonstrates that - in order to achieve a short filtration time - the working
pressure (P) should be high (up to 25 bar uncle' industrial conditions), the total filter area
large (up to 100 plates per filter press), porosity as high as possible, but the viscosity low.
11.2 Optimisation
The given technical functions are now to be evaluated by the specific prices in order to get
"Cost-functions".
This means the multiplication of specific demands with the specific prices of
Pumping energy
Thermal energy
Exhaust fan energy
Filtration
Thinners
etc.
Qualitatively the Cost-Function" is shown in relation to the water content of the slurry
[H2O]%.
The addition of all specific cost functions leads to the "Total Cost Function". This function
has the minimum point (optimum operational point) of course on the lowest operation cost.
On this point of the function the economical best water content of the slurry is to find.