Educational Book-132-138
Educational Book-132-138
Educational Book-132-138
9
INVESTIGATION OF BUILDING MORTARS
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ρ
Sm = c , (9.5)
C
where: ρc – is bulk density of cement in kg/m3;
C – is the amount of cement required for 1 m3 of sand in kg.
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9.2. Calculation of the composition of composite mortar
The propose of the test. To calculate the composition of
composite mortar according to the data provided.
Procedure. The data for the calculation of composition of
composite mortar are entered in Table 9.6 and according to the
provided formulae the composition of composite mortar is
calculated.
The amount of cement (C) required for 1 m3 of sand and the
volumetric portion of sand (S) is calculated according to the formula
provided in Section 5.3.
The volume of lime paste amount K corresponds to the unit
volume of cement:
K = (0,25 ⋅ S) – 0,3. (9.9)
The volumetric composition of composite mortar is expressed as
1 : K : S.
The selected composition: 1: ... : ...
Table 9.6. Initial data for calculation of composition of composite mortar
Mark and units of
Parameter Data
measurement
Mark of mortar S in MPa
Compressive strength of cement fc in MPa
Bulk density of cement ρc in kg/m3
Bulk density of sand ρs in kg/m3
Density of lime paste ρl in kg/m3
Coarseness of sand Ms
Resilience of mortar Sk in cm
After that the composition of cement mortar is calculated. For
the volume of sand used for testing VSl = 0,0025 m3, the amount of
sand S1 is calculated according to the formula:
S1 = VSl ⋅ ρs in kg. (9.10)
The volume of cement (VC1) and the amount of cement (C1) used
for testing is calculated according to the formula:
0,0025
VC1 = in m3, (9.11)
S
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C1 = VC1 ⋅ ρc in kg. (9.12)
The volume of lime paste used for testing (VK1) and the amount
of lime paste (K1) are calculated according to the formula:
0,0025
VK 1 = ⋅ K in m3, (9.13)
S
K1 = VK1 ⋅ ρk in kg, (9.14)
where: ρs, ρc, ρk – bulk densities of sand, cement and lime paste
in kg/m3;
S and K – amounts of sand and lime paste, expressed in
volume and corresponding to the volume of cement in parts of the
unit;
S1, C1, K1 – amounts of sand, cement, lime paste in kg;
VS1, VC1, VK – volumes of sand, cement and lime paste in m3.
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related to the behavior of fresh mortar when it is used for building
work.
Usually there is a linear relationship between the value of rod-
sticking determined by this test method and the value of mortar
spreadability determined for the mortar of the same type while
increasing water amount. However, the angle of line inclination will
vary with mortars of different types.
The purpose of the test: by testing a sample of fresh mortar, the
value of rod-sticking is determined according to the depth of vertical
sticking of a certain rod after its free fall from a definite height into
the sample of fresh mortar. The method suits for mortars with
mineral binders and aggregates of normal or of light weight density
when consistence is estimated by a rod-sticking value.
Apparatus: the device with a rod (Fig. 9.1) made of rod stand
with base plate, frame, fastening element with guiding bushes and
fixing screw; cylinder vessel centrally fixed at recessed place for
positioning; sticking rod with scale at the top and fixed plastic rod of
circle section at the base and semispherical end of the same diameter.
The total mass of a sticking rod and plastic rod makes 90 ± 2 g. The
initial position of a sticking rod is fixed at 100 mm above mortar
surface measuring from the bottom of semispherical end of a rod.
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A rammer is made of a rigid waterproof rod, approximately
40 mm in diameter and 200 mm long. The ramming surface at the
end of the rammer should be flat and perpendicular to longitudinal
axis of the rammer. The mass of the rammer should be
0,250 ± 0,015 kg.
Procedure. For this test the volume of fresh mortar should be
not less than 1.5 l. Two samples should be tested. The duration of
mixing is measured from the moment of pouring all components into
the mixer.
To avoid false binding before testing, the test mixture should be
slightly stirred manually by a spatula or a smoothing knife for 5–10 s
without any further mixing.
The sticking rod is fixed in its initial position by a fixing screw.
Before measurement the plastic rod is thoroughly cleaned by moist
textile and dried.
The vessel is filled by two layers of mortar and each layer is
compacted by 10 strikes of a rammer to top up the vessel evenly.
The excess of mortar is swept by a knife to make the mortar surface
flush with the top edge of a vessel. Afterwards the surface is no
longer levelled.
The filled vessel is put on the base plate and the fixing screw is
unscrewed to let the rod fall freely from its initial position.
The depth of rod-sticking into mortar is read from the scale,
counting from the lower par of a top guiding bush, correct to a
millimeter.
When the individual values of each tested mortar sample are
received, the average value of rod-sticking is calculated to a
millimeter. If two individual values differ from the average by less
than 10%, this average is considered to be the value of rod-sticking.
If two individual rod-sticking values differ from the average by more
than 10%, the test should be repeated.
The received results of the determination for the consistence of
fresh mortar are entered in Table 9.8.
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Table 9.8. Determination results of fresh mortar consistence (by the method
of rod-sticking)
Mark and units Tests
Parameter
of measurement 1 2
Depth of rod-sticking St in mm
Average value of Stav in mm
rod-sticking
Conclusion. …………………………………………………... .
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