12

CHAPTER 2

LITERATURE REVIEW

2.1 GENERAL

This chapter presents an extensive review of the recent research

works conducted on the use of self-curing and expansive agents in concrete
and their significant outcomes. Some pieces of literature related to the use of
admixtures and supplementary cementitious materials in concrete are also
presented.

2.1.1 Expansive Agents in Concrete

Carballora et al. (2015) studied the self-stressing behaviour of the

elements in self-compacting concrete, resulting from the effects of cement
and expansive agents. The work explained the effects of expansive additives
on compacting and compressive strength. Higher expansion was caused by
the un-watered type G additives. The efficiency of type K additives was
highly affected by the mixture composition. A lot of microstructural
procedures caused the expansion. An appropriate mixture of cement with type
G and type K additives was suitable for compacting and stressing on its own.
Small bubbles formed in the fresh state increased the slump flow, which was
due to the mixture of cementitious material. Expansion caused by expansion
can reduce the compressive strength of the concrete. The additive dosages do
not affect the concrete strength. Expansions were caused in both free and
restrained mixtures and were found to be high in free concrete.

The properties and microstructure of expansive self-compacting

concrete were influenced by the dosage of expansive calcium sulfo-aluminate
 13

as studied by Carballosa et al. (2019). Concretes that were made of ettringite

of calcium sulfo-aluminate sorted the early age problems of the concrete. The
study evaluated the dosage of concrete in three stages. In the fresh state, free
expansion of compressive strength and magnitude with curing by two
methods based on the mixture of SCC were studied. From the observations, it
was derived that the formed amorphous ettringite was involved in the
expansion. Thus, the influence of W/C cementitious material and the curing
methodologies on the mechanical specification and expansion was identified.
The three mixtures with type K agents did not affect the workability of SCC.
The decreased W/C ratio with type K agent resulted in the expansion of
concrete, which might lead to the collapse of the concrete when not
monitored. The decreased W/C ratio with increased expansive agents resulted
in the expansion and compromised mechanical properties of the SCC. XRD
and DTG did not detect the magnitude of expansion, and the use of an
expansive agent resulted in the removal of calcium mono-sulfoaluminate as a
hydration product. Despite the curing of concrete at 28 days, anhydrous
compounds led to the expansion when water was supplied.

The study on achieving well-durable self-compacting concrete

through the combined influence of expansive, shrinkage-reducing, and
hydrophobic admixtures was performed by Valeria Corinaldesi (2012). The
white self-compacting concrete was analyzed for the usage of its architectural
structures. Rheological specifications of cement paste and fresh SCC were
analyzed. Shrinkage reduction agents and CaO-based expansive agents are
used for reduced shrinkage in SCC. The SCC was effectively obtained by
using SRA with expansive agents and hydrophobic admixtures. Yield stress
was reduced with the use of SRA and the CaO with hydrophobic admixture
caused an increase even if limestone was replaced. The Bingham line was
achieved when the values obtained were low with regard to plastic viscosity.
Cement pastes showed anti-thixotropic behaviour, whereas CaO and SRA
 14

showed opposite hydrophobic admixtures when added. Paste flow velocity

was easily accessible at maintained shear stress and sufficient mobility was
obtained without any internal or flow segregation in the self-compacted
concrete. As per the test results, the concrete used showed good flowability
with no segregation caused.

Dong Rong Zhen et al. (2014) analysed the compensation of

expansive agents on self-compacting concrete and the apparent shrinkage.
The analysis of the quantitative and qualitative analysis was handled by XRD,
whereas the concrete comparator analyzed the fracture of the concrete. The
expansive agents were greatly affected by the mineral admixtures and curing
agents. These SCC mixtures expanded with the test time, watering, and
natural curing because of shrinkage, but the usage of mineral admixtures
reduced the shrinkage of SCC. Reduced alkalinity of SCC caused by the
addition of mineral admixtures leads to reduced ettringite formation, which
was evident by the microstructure analysis of SCC. Increased humidity causes
ettringite content to be higher with the use of mineral additives. Thus, curing
becomes an important factor for the expansion of SCC with added expansive
agent mineral admixtures. They showed remarkable effects on the SCC
expansion. The expansive agents under water curing conditions were
extremely effective in shrinkage control. Expansive agents showed effects on
the alkalinity and humidity and were also affected by curing and mineral
admixtures. The curing conditions had slight effects on the ettringite
compared to the mineral admixtures.

Jia Li-Li et al. (2016) studied the preparation and expansion

specifications of C60-expansive self-compacting concrete. Appropriate
expansion properties were also required, along with self-compacting in the
case of a concrete design. The self-compacting and expansion specifications
were made to meet performance and strength requirements. The expansive
 15

admixtures should be in control or else the work and strength would be

restrained. The mechanism of expansive concrete was based on the related
values of restrained and free-expansion concrete. The study revealed that the
self-compacting and expansion specifications should meet the property
designs. Free expansion reflected the ability to expand, and the correlation
between restrained and non-restrained expansion showed the capability of
SCC to expand. Early hydration due to the hydrastine agents present in the
SCC was observed in the cement specimens. Expansive agents applied to C60
self-compacting concrete recommended the use of expansive agents and their
specifications determine the volume stability and mechanical abilities. The
microstructure was dependent on the CSA for ettringite expansion. CSA
expansive agent and 0.32 as the water-cement ratio controlled the shrinkage
that appeared in the concrete. The higher dosage of CSA caused the lower
strength of C60 at early stages. Low binder ratio and hydrated cement paste
were shown using the SEM results. Any layer inside was framed out of the
crystal-like ettringite, and the formation after hardening showed compactness
in the concrete. The strength of C60 self-compacting concrete was caused by
the mixture of CSA, whereas reduced and increased strength at early and later
stages resulted in the required strength. The concrete strength was relatively
small and showed good coordination with the expansion properties as
obtained through 8% of CSA. Concrete expansion gets reduced with the
higher content of CSA and also resulted in the reduction of the shrinkage with
8–10% of expansive agent, at which the crack removal proved to be excellent.

Fang Liu et al. (2016) investigated the intensifying behaviour of a

concrete structure using expansive agents. A large volume of underground
concrete was tested, and expansive agents were used to create stress in this
large volume of concrete. Underground concrete exhibited shrinkage during
hydration, which resulted in water leakage. The shrinkage was compensated
for with the use of expansive agents. The expansion showed a rapid increase
 16

in the ratio between the concrete and expansive agent in the laboratory. The
field measurements showed 0.030% even after 28 days. The field test results
showed that the expansive strain of concrete can be increased, and the
expansive agents can enhance crack prevention. The difference between the
expansive strain required to reach the peak value and the restrained expansion
ratio showed that a long-term restrained condition could be maintained in the
expansion. The post-powered strips and the post-powered expansions
integrated with the bands of expansive agents show that the concrete structure
cannot be defensive of cracks.

The influence of combined expansive agents and the

supplementary cementitious materials on the mechanical, shrinkage
properties, and chloride penetration of the self-compacting concrete was
investigated by Kiazhi Liu et al. (2019). The partial replacements used were
fly ash, blast furnace slag, and metakaolin in place of cement. Three different
compositions of expansive agents were used in this study. Based on the
pozzolanic activity, longevity and improved mechanical specifications were
shown. The autogenous shrinkage caused due to dryness was greatly reduced
due to the magnesia expansive agents and the liquid expansive agents added
to the concrete, which improved the quality of the resisting chloride ions.
Highly effective shrinkage reduction was observed with the refined porosity
and the auto-desiccation. The V funnel time was reduced due to the usage of
the three expansive agents, which increased slump flow with the usage of
sulpho-aluminate expansive agent, polycarboxylate ether, and magnesium
expansive agent. The magnesium content in the expansive agent increased the
elasticity modulus and compressibility due to the dense and optimized
microstructure of SCC. Usage of three agents showed shrinkage at initial
stages, later corrected by magnesium and polycarbonate agents that resulted
in the improved expansion at 28 days.
 17

Maruyama et al. (2016) investigated the precast quality of

concrete products and the effects of expansive agents at various temperatures.
Precast concrete requires early strength development to enhance production
and also requires steam curing for use in de-moulding. The early strength
development was accompanied by crack formation due to temperature, and
the autogenous shrinkage was formed due to the expansive agent added. The
investigation was based on the large precast concrete affected by cracks and
the comparison of one supply per day with two supplies per day. The results
obtained stated that two cycles per day with high expansive agents and early
de-moulding created more thermal stress cracking. Inappropriate curing
caused excessive expansion and a large size of pre-cast concrete with
expansive agents at early de-moulding produced the best results. System
curing at a high temperature for the products manufactured in two cycles per
day, and their early curing had resulted in successive and magnified cracks.
Free expansion due to expansive agents was also generated due to internal
restraint. It was observed that the tensile strength and the elasticity modulus
registered the same cracking time. Thus, the results obtained indicated the
control of cracking by the regulation of mixing, curing, and restraining
conditions.

Precast concrete products manufactured in two cycles were steam

cured at an increased temperature to reduce the cost and increase productivity
by ensuring the strength as required. Takayoshi Maruyamma et al. (2017)
analyzed the steam-cured concrete, hardening properties, and effects of the
type of cement and expansive agents on it. Blast furnace slag powder and
other expansive agents were dependent on high temperatures. Two types of
expansive agents that were ettringite-based and lime-based agents were used
with the cement of precast strength and were investigated for their
compressibility and expansion. High precast cement and ordinary cement
were added with expansive agents to derive strength expressions. The
 18

prevented lime-based expansive agent showed higher expansion than the

ettringite-based expansive agent, whereas the lowered expansion fell to
reduced levels in ordinary cement. Adding expansive agents to increase the
strength showed the same strength results for both agents. The increase in
restrained expansions was higher by limestone than by ettringite when the
adding ratio was similar. It was observed that the early-stage portland cement
with expansive agent showed more expansion than ordinary cement.

Reza et al. (2013) studied the mechanical specifications of Nano

MgO when added to non-shrinking cement-based elements and its mechanical
properties. This study discussed the effects of the appliance of nano MgO on
the nanostructure of the mixture. The porous and mechanical specifications of
the cement-based elements in the presence nano MgO have been
experimented with, and their results were compared to plain cement
ingredients. The mechanical and flexural strengths registered were higher
along with the nano MgO binder when compared to plain composites.
According to the results obtained from SEM, the microstructure of the
mixture was more compact and similar than plain composites due to the
presence of nano MgO. The tests for compression and flexural strength
resulted in an increase in the presence of nano MgO compared to the control
mixture. The Nano MgO raised to 1% of the binder weight resulted in
decreased compressive and flexural strength. Porosity has been greatly
influenced by nano MgO addition and is used as a replacement for Mg with
Ca and C-S-H cationic exchange. Surface resistance was recorded as high
with the usage of nano MgO, whereas it was reduced due to excess addition.

The expansion mechanisms of calcium-sulfoaluminates-CaO-based

expansive agents in ultra high performance concrete were studied by Peiliang
Shen et al. (2019). Factors that affected the expansion were the exchange
between water solids, the low W/b ratio, and the closely packed structure. An
 19

expansive WHPC was obtained by using CaO as an expansive agent with a

reduced water level and a high recessive nature. The structural, hydration,
mechanical, and volume specifications were analyzed in this study. It was
observed that the addition of CSA CaO reduced auto shrinkage between 24
hours and 28 hours. It was recorded that improved mechanical specifications
by adding EA were diminished if added at an early stage. Reduced internal
RH resulted in high strains and segregation, as well as accelerated hydration
and overall shrinkage. The addition of EA reduced the RH and increased
dryness, resulting in shrinkage of the concrete. Insufficient expansion was
recorded if EA was added at an early stage to reduce shrinkage. A closely
packed structure and silica fume hinder the hydration process, whereas the
high reactive CaO added at low water consumption forms an effective UHPC
with reduced shrinkage.

2.1.2 Self Curing Agents in Concrete

Shrinkage and reduced tensile strength were resolved by the use of

expansive concrete through the formation of ettringite from calcium sulfo-
aluminate agents. The influence of various dosages on the cementitious
material and the curing ability, which altered the mechanical specifications of
SCC, was investigated by Carballosa et al. (2019). The expansive self-
compacting concrete made from the microstructural expansion of calcium
sulfo-aluminate was observed for its compressibility and its curing capacity.
The three proportions did not alter anything except for the fresh air alteration
of the excess dosage requirement. The flexibility and compression strength
were found to be increased with the expansion in magnitude. Initially, the
expansion mechanism formed small cracks in a disorderly manner, but this
was alleviated by self-curing.The expansive agent required an increase with
the lowered level of W/c ratio that resulted in micro-cracks that were not
completely cured, so that the expected micro integrity was not obtained. A
 20

microcrystalline characteristic was obtained through the hydration

mechanism. This study recorded the XRD diffract grams with no change in
intensity in the ettringite and the same was expected for 28 days.

However, binder concrete using higher cementitious materials and

low water, investigated by Kuruva Venkatesvaralu et al. (2020), enhanced
the durable properties, but the higher rate of hydration formed desiccation,
which resulted in increased permeability. The study highlighted that
conventional curing cannot achieve hydration and does not use any wastage.
But the usage of these waste products like fly ash and rice husk helped in
producing SCC with 100% hydration and at the same time removed the
environmental threat. The durability and strength are increased by the usage
of internal curing agents like lightweight aggregates with less than 0.36% W/b
ratio. The study also revealed the cost-effectiveness of SAP over other IC
agents. The decreased workability due to the increased dosage was
compensated for by prior wetting of agents, and the high particle size of SAP
helped in achieving increased workability. A higher rate of LWA dosage was
required to eliminate shrinkage, whereas low dosages of Super Absorbent
Polymer (SAP) proved efficient. The inclusion of fly ash in cementitious
materials was said to have increased workability but was affected by the
usage of internal curing agents. This study reviewed the effects of IC agents
on the specifications of concrete, and among all the IC agents, SAP proved to
be the most economical.

Curving becomes a problem in concrete when used at heights and

in areas of water inadequacy. This was eliminated only through the inclusion
of self-curing or internal curing. This helped in supplying redundant moisture
that helped in hydration and self-desiccation removal. This investigation by
Gopala Krishna Sastry et al. (2018) explained the impacts of self-curing
agents like Poly Ethylene Glycol (PEG), Super Absorbent Polymer (SAP),
 21

and Polyvinyl Alcohol (PVA) on the concrete mix of M25 grade. The results
improved the compressive strength, flexural strength, and tensile strength, and
PEG 4000 was considered to be more effective than other agents. Workability
was registered to be increasing with the increase in the percentage of self-
curing agents. The usage of PEG 6000 was found to achieve the maximum
tensile strength among all the other agents. Thus, PEG 4000 and PEG 6000
were recommended for maximum compressive strength, flexural strength, and
split tensile strength.

This investigation carried out by Udhayan and Rajamane was on

the preparation of SCC with increased compressive strength and tensile
strength that were obtained using the admixtures like fly ash, silica fume, and
superplasticizers at 2% of the cement usage. Self-compacting and self-curing
concrete were produced using polyethylene glycol at 0%, 1% and 2% rates.
Temperature variations were also studied, which further helped with air
curing. The study revealed that 1% of PEG in the mixture yielded higher
strength and lower compressive strength was observed when PEG dosage was
increased. The inclusion of 1% of PEG provided higher compressibility than
the normal mixture of water-cured mixtures without adding any self-element.
Temperature variations showed changes like the outside temperature, whereas
the effective results were studied inside the lab. A controlled environment
supported the working of PEG self-curing agents on the self-compacting
concrete.

A comparison of conventional concrete to that of self-compacting,

self-curing concrete of M20 and M25 grade was carried out in this
investigation by Mohan, 2016. Requisite moisture content was obtained with
designed properties using self-curing agents and the water evaporation was
reduced, which made SCC better than conventional concrete. The chemical
admixtures used in this study were cast into the specimens in different
 22

proportions. Better hydration was achieved by self-compacting concrete that

controlled evaporation and tended to absorb water from the atmosphere to
meet certain properties of the concrete. The self-curing agents absorb the
atmospheric moisture for the concrete and don’t need any external water
supply. The L-Box, V funnel, Slump flow, and fill box tests proved that
glycol 600 was passive for usage as a self-curing agent and provided
considerable satisfaction in the mechanical properties. The 30% replacement
of fly ash in SCSCC was better than compacting and curing concrete. It was
observed that the compressive strength improved with increasing age,
whereas the flexural behavior seemed to be comparatively low.

An endless prominence in the growth of concrete had resulted in

the development of self-compacting, self-curing concrete, which was termed
the most innovative of all developments in the construction field. Anisha and
Elba (2018) presented a review of self-compacting self-curing concrete.Self-
curing concrete has the added advantage of absorbing water content from the
atmosphere to achieve better hydration. Both curing and compacting could be
achieved by using the two types together. Recent studies were used to analyze
the physical and mechanical behaviors of self-compacting, self-curing
concrete. Higher compressive and tensile strengths were recorded when
compared to conventional concrete. Low water ratio and traditionally cured
specimens had the same compressive strength as SC-SCC but not with a
higher water-cement ratio. SC-SCC proved to be better than conventional,
self-curing, and self-compacting concrete. The results showed satisfactory
results, and the optimum results were obtained using 20% of fly ash PEG with
a lower molecular weight. Polyethylene glycol prevented the excess use of
water in the curing process.

The study of using lightweight aggregates in self-compacting, self-

curing concrete was carried out by Gopi and Revathi (2014). Partial
 23

replacement of fine aggregates with light-expanded clay and fly ash was
discussed in this paper. Mechanical specifications and fresh concrete
properties were analyzed with a 25% fine aggregate replacement, which
indicated positive specifications of self-compacting properties. Self-curing
conditions with 15% replacements showed greater strength than that of the
other mixtures. The ability to fill, pass, and resist segregation of concrete with
light-expanded clay and fly ash has shown improved rheological
specifications in the concrete mix. The compressive strength of concrete at the
initial stages was comparatively lower than the control mixtures, and
increased compressive strength has been recorded at the later stages. Thus, the
study reveals that the 15% replacement with light-expanded clay and fly ash
in SCSCC provided excess tensile strength, flexibility, compressive strength,
and durability.

Kamal et al. (2018) investigated the strength of self-compacting,

self-curing concrete at high and normal levels. This study used different
curing agents to understand the normal and high strength of the self-
compacting, self-curing concrete. The concrete grade, dosage, and curing
agents were taken into account to analyze the strength to normal and high
extents at the first stage. In the second stage, two concrete types were
reinforced in the concrete beam casts. Crack patterns, cracking loads, and
ultimate loads were brought into consideration, and the results obtained
suggested that both the mixtures were efficient in structural elements but that
curing and compacting lags. The water retention property of SCC was
increased with the hardened specifications of concrete by the curing methods.
Considering the ability to flow and work, self-curing and self-compacting
depend on the curing agent. PEG 6000 proved to be better than PEG 4000 at
attaining the strength of self-curing and self-compacting concrete.
 24

The investigation by Hajime Okamura and Masahiro Ouchi (2003)

was aimed at the investigation of self-compacting concrete to establish a
rational mix design to make SCC a standard concrete mix. The study
recommended rapid diffusion to support construction using self-compacting
concrete, to fluid a rational mixture and an efficient system for testing. It
highlighted the introduction of new constructional methodologies and design
systems for the SCC to be used. Very little maintenance work was required in
case SCC turned out to be a "standard mix" rather than a "special mix". The
focus of this investigation was on the curing and transportation properties of
the healing agents. The flow of curing agents, their dynamic flow, healing
through cracked areas, and the progress of curing adjacent to the concrete
were to be noted. These parameters helped to analyze the behavioural trends
in the capillary flow characteristics. The flow was easier on smooth cracks
than on capillary cracks. The experiment proved to be helpful and provided
useful information for the development and validation of the study on self-
healing agents.

The investigation carried out by Sri Ramachand et al. (2016)

studied the re-integration of structures by the usage of self-curing chemicals
in the production of self-compacting mortars using the appropriate self-curing
chemicals to enhance water retention and water withholding capacity. The
performance of the mortar was analyzed with the various dosages of self-
curing agents to analyze the effects of the acid attack on the specimens. The
study concluded that usage of self-curing agents at optimum levels in the self-
compacting concrete provided beneficial results in its efficiency. The loss of
moisture was reduced by adding self-curing agents. The compressive strength
obtained by adding self-curing mortar was the same as the wet-cured
mixtures. Minimized weight loss was registered with a decrease in sorptivity
values accompanied by a dense pore structure and low porosity.
 25

The inclusion of hydrophilic and hydrophobic chemicals in self-

compacting concrete was studied by Sri Rama Chand Madduru et al. (2019).
The study dealt with the curing of concrete that would help with the water
retention capacity. This study evaluated the effects of self-compacting
concrete when the self-curing agents were hydrophilic and hydrophobic
chemicals. The variables used in the study included the different dosages of
curing chemicals, dosage, and temperature. Compressive, split, and flexural
strength under different temperature conditions have been carried out. The
results suggested the addition of 1% of polyethylene glycol and 0.1% of
liquid paraffin wax to cement as the optimum. The types of curing agents
determined the specifications of the concrete that showed the concrete to be
workable and flowable. In this way, the EFNARC properties were matched by
the fresh specifications of SCC and in the absence of self-curing agents.
Elevated temperatures recorded higher weight loss than curing at room
temperatures. SCC with the proper proportion of PEG and LPW showed
better curing results. Compressive strength was recorded as high with
elevated temperature curing at early stages; however, the 28-day room curing
mixtures had better performance.

The autogenous shrinkage that appeared with the usage of self-

compacting concrete was presented in the study by Miguel Jose Oliveira et al.
(2013). The shrinkage controlling products have been evaluated and a mixture
of two shrinkage products at lower ratios and one expensive binder mixture
has been studied. The obtained results were potential enough to achieve pre-
planned shrinkage with the usage of the shrinkage control mixtures when used
alone and in combination with the binder material. This study dealt with the
shrinkage reducing agents and expansive products in controlling the shrinkage
formed in self-compacting concrete. The results proved that shrinkage can
even be eliminated with the use of shrinkage-reducing agents and binders.
The expansive products when used in controlled dosage avoided detrimental
 26

expansion and reduced shrinkage, which suggested the use of the expansive
binders and shrinkage reducing agents to come up with a mixture that showed
reduced shrinkage.

Garcia Calvo et al. (2017) investigated the factors by comparing

the expansion and curing of expansive self-compacted concrete and expansive
conventional concrete. Their specifications based on physical, mechanical,
and microstructure has been evaluated. The reports clarify that the retaining
capacity of the concrete had an impact on the structure and morphology of the
ettringite. The receptiveness of the expansive agents was influenced by the
curing and composition of the concrete. The usage of limestone was
suggested in expansive mixtures rather than using fly ash. High-expansion
agents were also feasible to use in the mixture. A lot of air content was
observed in the mixture of SCC when compared to the conventional mix. This
can be due to the superplasticizer based on polycarbonate and expansive
agents. Due to the difference in composition, Type G content shows higher
compressibility than Type K content. In the fresh state, high compressibility
was common due to its retaining strength better than self-cured samples
underwater. The high porosity and change in mechanical and morphological
specifications suggest the use of limestone and fly ash with type K agent in
the SCC mixture. The study on internal curing of high-performance concrete
using coal bottom ash materials as water reservoirs and with the inclusion of
magnesium-based expensive agents also showed that the cracks appeared due
to excessive tension due to the change in volume. Using fly ash as a binder in
the mixture of cement, coal bottom ash for internal curing and magnesium
oxide as an expansive agent was recommended. The study proved that the
expansive agent and the internal curing have collaborative effects on high-
performance concrete. The shrinkage was reduced due to the internal curing
that enhanced the expansion of magnesium oxide. Compressive strength was
affected by a small amount of magnesium oxide and coal bottom ash curing.
 27

Coal bottom ash curing created reduced shrinkage and better stability in
volume and compressibility was attained through the blended mixture.

High-strength self-curing SCC with mineral admixtures was

studied by Selvamony et al. (2019). The durability of fresh concrete was
enhanced by the admixtures in various percentages. The effectiveness of these
admixtures was studied in this observation, which included the replacement of
cement and aggregates by limestone powder, silica fume, quarry dust, and
clinkers, and their properties were compared. The use of silica fume in
concrete requires a higher dosage of superplasticizer. The results of this study
showed that using quarry dust, limestone powder, and silica fume enhanced
the workability of SCC more than using it alone. The self-compatibility
remained unaffected with 8% of limestone, silica fume, quarry dust, and
clinkers. Limestone with quarry dust altered the mechanical specifications of
SCC, whereas silica fume improved the durability of SCC.

2.1.3 Metakaolin in SCC

Nano-metakaolin has been widely used as a concrete ingredient in

recent years. Nano-metakaolin has been shown to be a better cement
substitute than other nanomaterials, with a greater impact on modifying
concrete properties. As a result, several studies on the use of nano Mk in
concrete have been conducted, and several conclusions have been reached.
However, from the systematic review of literature conducted, no study has
been attempted utilizing nMk in SCC, and hence it becomes necessary to
understand the behavior of nMk in SCC with and without other additions of
SCM and chemical admixtures. No study is available using nMk in self-
curing SCC, and this study is one of its kinds. The literature pertaining to the
use of metakaolin in SCC is as follows:
 28

Showkry et al. (2016) proposed a study on lightweight vermiculite

cement composites and reported the physico-mechanical properties of the
composites incorporated with nano-metakaolin. They replaced the white
Portland cement with 70% of expanded vermiculite and nano-metakaolin as a
partial replacement at 2, 4, 6, 8, and 10% by mass of expanded vermiculite.
The microstructural behaviour of the cement composites was measured
through scanning electron microscopy. The improved crack resistance and
tight bonding were achieved in the matrix through the nano metakaolin
platelets, which bridged the micro cracks. Through the usage of nano-
metakaolin, 10% replacement level showed enhanced compressive and
flexural strength. Since nano metakaolin had a high amount of amorphous
silica, they showed active participation in the pozzolanic reaction by
producing more CSH. The matrix capillary pores were reduced by filling the
voids with ultrafine-sized nano metakaolin. They also reported that the nano-
metakaolin does not show any significant effect on density and thermal
conductivity. From this study, it is clear that the usage of nano metakaolin
results in the improved physico-mechanical and microstructural behavior of
cement composites.

Rashad and Sadek (2016) investigated the relative strength

properties of concrete with high volume GGBS and micro metakaolin
exposed to elevated temperature conditions. They produced a high volume of
GGBS paste by partially replacing the cement with 70% GGBS. Also, the
micro metakaolin was substituted as a replacement for GGBS at 2, 4, 6, 8, and
10% by weight. The testing was carried out on the specimens subjected to
4000C, 6000C, 8000C, and 10000C and it was also reported that the highest
value of residual compressive strength was achieved for 4000C treated
specimens. The increased micro metakaolin substitution resulted in improved
compressive strength for both normal and elevated temperature-subjected
concrete specimens. Although the increased micro metakaolin results in
 29

greater weight loss, the higher pozzolanic action and filling ability of micro
metakaolin helped in achieving reduced porosity and enhanced compressive
strength.

Norhasri et al. (2016) conducted a comparative study between

normal and nano metakaolin incorporating ultra-high-performance concrete
mixes. The workability and strength development of concrete with nano
metakaolin were analysed. The ultra-fine size and clay properties of nano
metakaolin resulted in low workability and enhanced compressive strength at
later ages when compared with normal ultra-high-performance concrete. It
was clearly evident that the formation of additional CSH gels due to nano
metakaolin resulted in the strength increment of the concrete. They reported
that the nano metakaolin content helped in refining and densifying the
microstructure at the initial stages (3 and 7 days) and achieved better strength
at later ages (28 days). The achievement of the densified surface of normal
concrete was mainly due to the homogenous surface structure formed. The
various morphological formations were identified by scanning electron
microscopy. A thin and sharp crystal indicated the combined effect of ultra
filler and the pozzolanic nature of nano metakaolin.

The effect of nano metakaolin on cement mortars at various

temperatures was examined by Morsy et al. (2012). They carried out various
tests on nano metakaolin cement mortars, such as compressive and flexural
strength, to understand the mechanical behaviour, whereas their
microstructural behaviour was analysed through XRD and SEM. In this study,
the nano metakaolin-made mortar specimens were subjected to 2500C, 4500C,
6000C, and 8000C. The nano metakaolin was used as a replacement for
ordinary Portland cement, and its replacement levels were chosen as 5, 10 and
15%. The improved compressive and flexural strength were observed for the
mortar specimens exposed to 2500C, whereas at the higher temperatures the
 30

strength values dropped. They reported that the increased amount of hydration
products and pozzolanic reaction caused by the nano metakaolin substitution
was the primary factor in the improved strength of mortar specimens. When
the mortars were exposed to temperatures above 2500C, micro and macro
cracks developed, which resulted in reduced strength attainment. When
thermally treated mortar specimens were subjected to 2500C, a well-
crystalline CH was developed.

Pei-min Zhan et al. (2020) provided a review of the various

properties of nano metakaolin incorporated concrete, including fresh state,
mechanical, and durability characterization. The dispersibility of nano
metakaolin and their large specific surface area reduced concrete workability
by promoting cement hydration. They suggested that the improved strength
was attained at early ages due to nucleation and bridging effects. Through
their comparison between various pieces of literature, it was found that
increasing the content of nano metakaolin reduced the water absorption and
also showed better resistance to chloride attack. In this review study, they also
suggested future work be performed for the better usage of nano metakaolin
in concrete, such as determination of creep, shrinkage, and usage of CT and
nano-indentation scan.

Jun Xie et al. (2020) modified the recycled aggregate concrete

with nano-metakaolin and its influence on various concrete properties was
examined by Jun Xie et al. (2020). The nano metakaolin, being a material
with a better pozzolanic effect, helped in promoting the secondary cement
hydration process. Using the scanning electron microscope and the BET and
BJH methods, the internal microstructure, specific surface area, and pore
volume of the recycled concrete were determined, respectively. The strength
properties of recycled concrete with nano metakaolin content showed gradual
improvement at increased substitution levels. It was reported that the fully
 31

recycled aggregate concrete containing nano metakaolin exhibited higher

compressive strength. The refined pore structure and reduced pore volume
were made possible by finer grain-sized nano-metakaolin. A larger number of
C-S-H gels were generated during the secondary hydration reaction by nano
metakaolin, which had a strong volcanic ash effect.

Al-Jabri and Shoukry (2018) studied the influence of ferrochrome

slag in combination with nano metakaolin on various properties of mortar. In
this study, they focused on the impact of using nano-metakaolin on the
mechanical, thermo-physical, and microstructural properties of mortar. The
fine sand was replaced by 50% of waste ferrochrome slag, whereas the
cement was replaced by nano metakaolin at different proportions (2 to 14%)
by weight. Even though the inclusion of ferrochrome slag showed improved
strength, thermal conductivity, and better resistance to drying shrinkage, the
usage of nano metakaolin played a major role in providing additional
enhancements to the properties of the mortar. The reduced capillary water
absorption was mainly due to the refined pore structure of nano metakaolin.
The presence of nano-metakaolin in the mortar created a better bond between
the ferrochrome slag and the mortar. From the study, they made the
suggestion that improved physico-mechanical behavior can be achieved by
using nano-modified ferrochrome slag.

The impact of using nano-scale metakaolin on the compressive

strength, pore structure, and microstructural behavior of mortar was examined
by Morsy et al. (2018). They performed BET analysis to determine the
specific surface area and SEM analysis to confirm the nano-plate formation.
The mortar specimens were prepared by substituting the nano metakaolin and
exfoliated nano metakaolin separately from 1 to 5% by weight. It was found
that the exfoliated nano metakaolin with enhanced surface area improved the
mortar compressive strength at 3% substitution. The strength increment
 32

percentage of exfoliated nano metakaolin was reported as 24% and 54% when
compared with un-exfoliated nano metakaolin and normal mortar. It was
evident from the BET analysis that the refinement of the pore structure was
achieved to a greater extent for exfoliated nano metakaolin mortars than the
others. This was mainly due to the filling ability of nano metakaolin that
helped in promoting the pozzolanic reaction and hydration as confirmed
through TGA and SEM analysis. They came to the conclusion that the
implementation of exfoliation treatment for nano metakaolin proved to be
better than the normal addition of nano metakaolin in mortar.

The role of nano metakaolin in developing the fly ash-based geo-

polymer mortar was presented by Mandeepkaur et al. (2018). The change in
compressive and microstructural behaviour of the mortar was examined by
using an alkali activator solution, which was a mixture of sodium silicate and
sodium hydroxide. They replaced the fly ash content with the nano
metakaolin at various percentages from 0 to 10%, with an increment of 2%. It
was found that the inclusion of nano metakaolin helps in achieving improved
compressive strength of the mortar. The increased strength was mainly due to
the dispersion mechanism of nano metakaolin, which was responsible for the
nucleation material development. The microstructural study revealed that the
greater ratio of Si/Al results in decreased mortar compressive strength.

2.1.4 Copper Slag in SCC

A number of research studies have been conducted using copper

slag as a fine aggregate replacement in conventional and self-compacting
concrete. The use of copper slag significantly improved the long-term
performance and durability of concrete. A review of the literature on copper
slag revealed that the majority of work has been done in other countries, but
only a few studies have been done in India using copper slag as a replacement
 33

for fine aggregate in concrete. The use of copper slag as fine aggregate in
self-compacting concrete has been attempted by very few researchers.
Therefore, the potential use of copper slag in self-compacting concrete had to
be assessed experimentally to attain confidence in the usage of copper slag as
a construction material.

The abundant availability of copper slag from copper industries

paved the way for utilizing the slag wastes in concrete to attain better
performance. In this study, Nikita Gupta and Rafat Siddique (2019) developed
a self-compacting concrete through partial replacement of copper slag with
fine aggregate and constant replacement of fly ash with cement. The
substitution ratio of fly ash was fixed at 20% for cement replacement and
copper slag replacement, up to 60% for fine aggregate. Due to the improved
workability of the SCC mixes due to the reduced water-absorbing behavior of
copper slag, the increased cohesion of the matrix was obtained through the
angular edges of the slag grains, which resulted in strength enhancement. The
strong behavior was supported by the dense nature of the concrete matrix,
which was evident from the microstructure studies. They also reported that
the usage of copper slag above 30% showed a significant reduction in their
strength, which was mainly due to the pore and microcrack formation.

Yasser Sharifi et al. (2020) utilized waste copper slag instead of

natural coarse aggregate in the SCC. The copper slag replacement level was
increased from 0% to 100% for coarse aggregate. The increased flowability
was achieved for all the self-compacting concrete mixes at constant w/c
content. The smooth surface of the copper slag aggregates helped in achieving
less water absorption of the SCC mix. The obtained consistency of SCC
supported the enhanced compressive strength achievement on increasing
substitution levels of copper slag. The relevant bonding between the cement
paste and copper slag grains resulted in improved split tensile strength of the
 34

SCC. The main cause of the formation of the dense structure of the aggregates
was the angular-shaped copper slag aggregates, which further contributed to
the significant enhancement of the flexural strength of the SCC. The broken
pieces of angular copper slag aggregates get well involved with cement paste,
thus improving the drying shrinkage of the SCC mixes. The reduced surface
water absorption was observed for SCC mixes up to 40% copper slag, and
beyond that, the water absorption starts increasing but within the control limit
absorption value. They also reported that the use of waste copper slag in SCC
showed economic benefits and had a vital impact on the environment.

Iman Afshoon and Yasser Sharifi (2020) presented the

performance of micro copper slag incorporated SCC at increased percentage
levels. The substitution level of copper slag for cement replacement was
chosen as 0 to 30%, with an increment of 5%. They evaluated the fresh and
hardened properties of SCC before and after exposure to high temperatures
ranging from 1000 °C to 8000 °C. Better flowability and filling capacity were
observed for SCC at all replacement levels. It was found that up to 15%
replacement of copper slag showed improved mechanical strength, beyond
which there was considerable strength declination. During the temperature
study, the 5% copper slag substituted SCC mix yielded a better result in all
aspects, whereas at increased replacement level, the SCC behaved in an
inappropriate manner. They also confirmed the performance of SCC through
polynomial regression, which held a better correlation among various
concrete properties.

The durability study on SCC with copper slag was carried out by
Rahul Sharma and Rizwan Khan (2017a).The copper slag was replaced with
the fine aggregate at various percentages from 0 to 100% with an increment
of 20%. The SCC mixes showed better filling behavior and passing ability at
incremental replacement of copper slag, which was mainly due to the non-
 35

porous nature and reduced absorption behavior of copper slag. The SCC mix
with 20% copper slag yielded a maximum compressive strength greater than
the other mixes. At higher replacement levels of copper slag above 20%, the
content of free water was increased, which resulted in a declination of
concrete strength. The SCC mixes showed reduced carbonation depth because
of the greater iron content in copper slag. It was also found that when the
concrete was exposed to a sulfate attack, the concrete strength was reduced
and the weight was increased. This was mainly due to the formation of
ettringite, which resulted in micro cracks and expansion in concrete. Good
results can be observed in concrete mixes with up to 60% CS substitution for
both electrical resistivity and UPV. The reduced values beyond 60% CS
addition for electrical resistivity were caused mainly by the increased porosity
of the concrete. They also reported that the concrete behaves well and
excellently at early and later ages, respectively. They concluded their research
by suggesting that 60% CS substituted SCC has good durability properties.

Rahul Sharma and Rizwan Khan (2017b) addressed the behavior

of copper slag incorporated into SCC containing fly ash and silica fume.
Copper slag was replaced with fine aggregates, whereas fly ash and silica
fume were used as partial cement replacement materials. The utilization of
copper slag in concrete greatly reduced the requirement for superplasticizer,
which in turn resulted in the attainment of better fluidity for SCC mixes.
Improved compressive strength was obtained for the ternary blend with 20%
silica fume, which was evident from their micro-filling behaviour, resulting in
a densified interfacial zone. The angular copper slag aggregates improved the
concrete matrix cohesion by interlocking particles, which enhanced the tensile
strength of SCC mixes. They reported that the use of silica fume decreased
the sorptivity of concrete, which was compensated for by the addition of fly
ash, which helps in increasing the capillary pores of the concrete. All the SCC
mixes showed the presence of CSH gels, but when 100% copper slag was
 36

used, some micro cracks were visible, and this was due to the availability of
excess water in the concrete mix. They concluded that the utilization of
copper slag can form a low-cost concrete since the superplasticizer dosage
and energy requirements were reduced.

2.2 INFERENCE FROM THE LITERATURE

 Shrinkage compensating materials can prevent crack formation and

enhance the volume changing characteristics of the cement based
composites.

 Expansive agents can enhance the behavior of concrete with low

w/b ratio and high shrinkage.

 CaO and MgO based expansive agents can enhance the expansion
behavior of the cement matrix at later and early ages.

 Higher contents of expansive agents in concrete can exhibit a

promising effect on the shrinkage mitigation (both autogenous and
drying shrinkage) but can adversely affect the strength.

 Nano metakaolin also facilitates the hydration of the cement matrix

through their nucleation effect by forming additional hydrates from
the pore solution.

 The use of nano based expansive agents can also reduce the
porosity of the concrete composites by enhancing their
microstructure and surface resistance properties.
 37

 Expansion in concrete is mainly affected by the w/b ratio,

reactivity of the materials used and specific surface area of the
ingredients.

 The involvement of copper slag in drying shrinkage mitigation can

be seen through the angular grains of copper slag which shows
better attachment with the cement matrix.

2.3 SCOPE FOR THE STUDY

The use of waste materials in the production of self-compacting

concrete has benefits in not only reducing the number of waste materials
requiring disposal but can provide construction materials with significant
savings over new materials. This study is oriented towards utilizing
supplementary cementitious materials and industrial wastes in the production
of self-compacting concrete. There were only a handful of pieces of literature
on the use of expansive agents and self-curing agents in the production of
self-compacting concrete. Literature on the combined use of self-curing and
expansive agents on the self-compacting concrete containing the wastes of the
industry is also not extensive. A few studies have reported on the use of silica
fume and metakaolin as materials in self-compacting construction. Little
research was reported on copper slag for its use as a fine aggregate in self-
compacting concrete. Therefore, the present study is important and its
findings will be useful in concrete technology wherein natural fine aggregate
using copper slag and cement is to be replaced partially with metakaolin.