Effect of lime water on the properties of silica fume ...nopr.niscair.res.in/bitstream/123456789/43705/1/IJEMS 24(6) 491-49… · This study is to investigate the setting time and

Indian Journal of Engineering & Materials Sciences

Vol. 24, December 2017, pp. 491-498

Effect of lime water on the properties of silica fume blended

cementitious composite

S Maheswarana*, V Ramesh Kumar

a, Mohammed Saffiq Reheman

a, Smitha Gopinath

a,

A Ramachandra Murthya & Nagesh R Iyer

b

aCSIR-Structural Engineering Research Centre, Taramani, Chennai 600 113, India bAcademy of Scientific and Innovative Research, CSIR Campus, Taramani, Chennai 600 113, India

Received 5 August 2017; accepted 16 May 2017

This study is to investigate the setting time and strength properties of cementitious composite mortars blended with silica

fume by the replacement of 10, 20 and 30% of cement with two types of lime water. Concurrently, cement pastes for each of

the above mix proportion are prepared to study the hydration kinetics by using XRD analysis. The ordinary potable water

has been completely replaced with two types of lime water for all the samples except control samples. The results of setting

time experiments show that there is a considerable reduction in the initial and final setting times for both the cases of lime

water and silica fume blended cement pastes compared to control sample. The lime water with ionic level suspension tends

to increase the compaction and early strength of the mortars. Though the lime waters without silica fume reduces the

strength of mortars, the specimens with silica fume and lime water tends to show increase in compressive and split tensile

strengths, influenced by the binary blended cementitious composites which improves both early strength and later strengths.

Keywords: Saturated lime water, Natural lime water, Silica fume, Cementitious composite, XRD, Strength properties

Concrete is a highly heterogeneous material produced

by mixture of finely powdered cement, aggregates of

various sizes and water with inherent physical, chemical

and mechanical properties. A reaction between the

cement and water yields calcium silicate hydrate, which

gives concrete strength and other mechanical properties,

as well as some more by-products including calcium

hydroxide (CH), ‘gel pores’, Aft (Ettringite), Afm

(Monosulfates) etc. Despite the hydrated cement and

their by-product materials are available everywhere in

the concrete, the reactions within the concrete during

setting (fresh state) and hardening (gain strength) are

difficult to control and this is an ongoing problem in the

concrete industry. The American Society of Testing and

Materials (ASTM) defines1 pozzolan as a siliceous or

alumino-siliceous material that in itself possesses little or

no cementitious value, but in finely divided form and in

the presence of moisture will chemically react with

alkali and alkaline earth hydroxides at ordinary

temperatures to form or assist in forming compounds

possessing cementitious properties1.

Hence, it is imperative for the evolution of new

materials for improved performance for engineering

applications. Newer materials are obtained by

innovative and intermixing of existing materials at

component level. It is well known that the concrete, in

a 2-phase system comprises of cement paste and

aggregates (fine and coarse), the aggregates are inert.

The amorphous phase calcium–silicate–hydrate

(C–S–H) is the ‘‘glue” that holds concrete together.

1/3 of the pore space is comprised of gel pores and the

rest are capillary pores. Interfacial transition zone

(ITZ) is the zone of bonding between cement paste

and aggregates. Porosity of the paste as well as the

proportion of CH in this zone is considerably higher

than in the bulk paste. This zone forms the weak link

in the concrete, and is usually the site of first

occurrence of cracking in concrete.

The concrete is the most widely used construction

materials due to its low cost and long durability.

Generally, the production of every ton of Portland

cement releases about the same quantity of CO2, a

greenhouse gas in to the atmosphere, which is

accounted for 7-8 % of total CO2 emission2,3

. Hence,

the need for the cement replacement is a primary

factor in construction industry. With the advent of

various supplementary cementitious materials

(SCMs), construction field has achieved enormous

potential applications by the way of reduction in

cement consumption, enhanced properties and

reduced carbon foot print. Utilization of these

__________

*Corresponding author (E-mail: [email protected];

[email protected])

INDIAN J. ENG. MATER. SCI., DECEMBER 2017

492

industrial by-products and/or wastes are either as

cement replacement materials or as aggregates in

concrete presents environmental benefits. For the past

three decades, pozzolanic materials showed much

interest in construction for their influence on the

higher performance of the concrete4,5

. The concrete in

fresh as well as in the hardened state, the

supplementary cementitious materials (SCMs) such as

silica fume (SF), fly ash (FA), ground granulated blast

furnace slag (GGBS), rice husk ash (RHA),

metakaoline (MK) etc improve the pozzolanic activity

and also densifying the concrete by means of packing

of the solid materials in the system (filler effect) by

occupying some of the spaces/pores between the

aggregate particles. Also, different SCMs have been

replaced in certain percentages for cement to get new

or improved properties of concrete in addition to

reduction in carbon foot print and achieved

great success.

The pozzolanic activity of SF enhanced the

hydration activity in cement pastes, because of its

amorphous form with high specific surface area. But

it is reported in the literature6-9

that the early age

strength cement paste is very low. Beyond 90 days,

SF is consumed by CH resulting in improvement of

later day strength9. Apart from pozzolanic activity of

SF, it also acts as filler in concrete, which fills the

pores and voids between the cement paste and

aggregates leading to more compaction of concrete10

.

The guideline for the use of SF and its beneficial

influence in concrete has been reported by many

researchers11

. ACI committee11

also suggested the use

of SF up to 12% of replacement of cement. Oner

et al.12

reported that the fly ash reaction needs calcium

hydroxide (CH) crystals to improve concrete

properties, they have added lime powder with fly ash.

Mira et al.13

observed that the above stated reaction

exhibits significant improvement in concrete

durability rather than any influence in the

development of concrete strength. The treatment of

concrete with lime is assured by ASTM14

, but it

should be used as curing water for mortar cubes.

Barbhuiya et al.15

observed that the incorporation

of hydrated lime with silica fume in fly ash concrete,

there was an improvement in early age compressive

strength. It was concluded that both the strength and

durability of the fly ash concretes could be improved

by the addition of either hydrated lime or silica fume,

however, the quantification of the hydrated lime and

SF on the long-term strength development and

durability are not reported. It has been studied earlier

by some researchers that a high degree of silica fume

agglomeration in cement pastes or mortars due to

inadequate dispersion. This agglomeration of silica

fume can reduce its effectiveness on properties of

cement paste and mortar, because of the existence of

SF particle clusters and a lower pozzolanic reactivity.

Slurried silica fume is a liquid mixture composed of

un-densified powder and water in equal proportions

by weight, which promises a better dispersion into the

concrete mix and which has rarely been studied in

literature. Rossen et al.16

have studied the

composition of C-S-H in slurried SF cement pastes,

and found that the reduction of portlandite and

increase in C-S-H quantity. Zhang et al.17

have

compared the compressive strength of materials made

of slurried and densified SF (DSF) and noticed that

the non-evaporable water content and compressive

strength of paste containing DSF are lower than that

containing undensified silica fume. Grist et al.18

showed interest in natural lime-based hydraulic binder

with 25% SF by mass of cement and observed that the

continual increment of compressive strength up to 90

days of curing. Recently, the strength development of

lime–pozzolana pastes with silica fume and fly ash has

been studied by Koteng et al.19

and they observed that

lime based pozzolana pastes can reduce the weight of

the structural elements and the overall cost of structures.

Other than conventional SCMs of micro-sized

materials, a series of research studies20-26

were

conducted by using various nano-sized particles such

as nano-SiO221,22

, nano-Al2O323,27,28

, nano-TiO225

,

nano-Fe2O326

etc towards their effects in the

mechanical properties of concrete. Senff et al.21

investigated the effects on various properties of

mortar with nano-silica and micro-silica (SF) at

different proportions. The effects of lime water on the

mechanical and setting properties of nano- Al2O3 up

to 2% blended cement had higher split strength

compared to that of the concrete without nano- Al2O3,

when the specimen cured in saturated lime water for

28 days. At the same time, it was observed that the

workability has decreased for fresh concrete

especially cured in lime water27,28

. The effect of lime

water on the properties of non-traditional materials

like nano-Zr2O3 incorporated concrete has been

studied by Nazari and Riahi29

and observed that

optimum level of nano- Zr2O3 with 2% replacement

of cement in concrete cured in lime water for 28 days

showed the enhancement in strength, but there was

MAHESWARAN et al.: SILICA FUME BLENDED CEMENTITIOUS COMPOSITE

493

reduction in the setting times as the replacement level

increases.

There is hardly any study which clarifies optimum

use and/or consumption of SF in the concrete system

at early or later stage. Generally, the pozzolanic

activity (the chemical reaction of CH crystal with

SCMs) starts only after the formation of hydrated

product of cement. That is, the formation of CH

crystals occurred after the hydration of C3S and C2S

in the cement. It is well known that the hydration of

C3S is shorter than C2S hydration; hence there is a

delay in pozzolanic activity. The early pozzolanic

activity could be achieved by using hydrated lime of

lime water solution in place of ordinary potable water.

Therefore, this study is planned to investigate the

influence of two sources of lime water in the binary

blended cementitious composites in the paste and

mortar level. It is also aimed at to find the consistency

level, setting time properties, hydration process and

mechanical properties of Portland cement based

composite containing SF and mixed with lime water.

Materials and Methods The cement used for pastes/mortar is 53 grade

ordinary Portland cement (OPC) conforming to

IS: 12269 – 198730

and the physical and chemical

properties are given in Table 1. The locally available

grade 2 sand conforming to IS: 383-197031

is used.

For determination of appropriate water to cement

ratio, standard consistency test has been conducted

and water to cement ratio of 0.41 is arrived at.

Ordinary potable water is used for control pastes and

mortar cubes and cylinders. Two types of lime are

used in lime water filtrate preparation. First lime

water filtrate is obtained by slaking of lime obtained

from calcinations of natural seashells (labeled, LW)

and the second lime water is obtained by dissolving

commercial calcium hydroxide (Ca(OH)2) (labeled,

LD) received from Merck Millipore, Division of

Merck with high purity. The lime water filtrates for

calcium hydroxide is obtained from full saturation

(~1 g/L) of calcium hydroxide in water. The pH and

conductivity of the prepared solutions along with

potable water are given in Table 2. The increased

conductivity value of the slaked lime water may be

due to the mobility of more ions in this particular

case. Moreover, the alkalinity (higher pH) level of

lime waters is more than that of potable water and this

will be useful when reacting with SCMs such as SF.

The chemical composition of the raw materials is

analyzed using X-ray fluorescence spectrometer

(Bruker S4 Pioneer). Bruker’s D2 PHASER X-ray

diffraction (XRD) system, equipped with 1-D

LynxEye detector is used in the present study and it

employs Cu-Kα radiation (30 kV, 10 mA) with Nickel

filters. A continuous scan of 2θ from 10° to 60° in

step width of 0.020 and counting time of 0.5 s per step

is performed on less than 25 µm size powder samples.

Experiments are designed to evaluate the

performance of Portland cement based materials

containing silica fume mixed with W, LW and LD

(Table 3). The mix design for binder to sand for

mortars is 1:3. Total of 15 mortar cubes for each

mixes are cast to test the compressive strength for

different days, viz., 3, 28 and 90 days (each 5 cubes)

of curing. The cement pastes for each of the above are

also mixed to study the hydration kinetics of different

days of curing using XRD analysis. Concurrently, the

mortar cylinders (50 mm × 100 mm) for each mix are

cast for the similar proportions to study the split

tensile strengths for different days, viz., 7 and 28 days

(each mix 6 cylinders) of curing. The polycarboxylate

based high range water reducing admixture

(HRWRA) is used as superplasticizer (SP) by weight

of cementitious materials to get the uniform

flowability in cube mortars / cylinder mortars. The

water to binder (cement + SF) ratio for all mixtures is

fixed as 0.4.

Table 1 — Physical and chemical properties of cement and SF

Chemicals Oxide Constituents (%)

Cement Silica fume

SiO2 20.24 94.73

Al2O3 5.64 -

Fe2O3 4.07 -

CaO 63.42 -

SO3 3.48 0.2

Na2O 0.19 0.51

K2O 0.56 -

MgO + MnO 0.88 -

LOI 1.52 1.5

Physical properties

Color Dark gray Gray

Specific gravity 3.162 2.15

Bulk density, g/cm3 1.561 0.13-0.6

Fineness passing 40 µm sieve, % 85 92-95

Moisture content, % <1-2 <1

Table 2 — pH and conductivity measurements of lime waters

Solution pH

Value

Conductivity,

mS/cm

Potable water 7.678 1.431

Slaked, Natural lime water, LW 9.733 5.142

Saturated calcium hydroxide

solution, LD

10.719 1.286


494

To prepare the mortars containing silica fume, first

the binders such as cement and silica fume are added to

river sand and placed in mixer machine resuming dry

mix for about 2 min. Then the water, which is premixed

with the superplasticizer, is added and mixing is carried

out for 5 min. Finally, the freshly prepared mortar is

poured into cube moulds of size 70.6 × 70.6 × 70.6 mm.

Similarly, the mortar cylinders of size 50 × 100 mm are

cast. After pouring, an external table vibrator is used to

facilitate compaction and decrease the amount of air

bubbles. The specimens are de-molded after a lapse of

24 h for moist curing and then cured in water till for the

testing periods 3, 28 and 90 days. Concurrently, to study

the hydration kinetics by using XRD analysis of the

above mixes in the paste form are also prepared. The

compression test is carried out on 100t UTM under load

control. The tensile strength of concrete is evaluated

using a split cylinder test, in which a cylindrical

specimen is placed on its side and loaded in diametrical

compression, so as to induce transverse tension.

Result and Discussion

The following sections present the properties of

cementitious composites mixed with potable water

(W), saturated lime water (LD) and natural lime water

(LW) solution. Consistency level, setting times,

hydration process and mechanical properties such as

compressive and split tensile strengths are evaluated.

Initial and final setting times

The results of the setting times studied for the

cement composite pastes with partial replacement of

silica fume and with two types of lime waters by

using Vicat apparatus are provided in Fig. 1. It has

been found that there is a reduction in both the initial

and final setting timings (IST and FST) for the

samples with replacement of silica fume by 10, 20

and 30% and with ordinary potable water compared to

control samples. This may be due to the acceleration

of hydration process by silica fume with cement. In

the case of control with saturated lime water, the

initial setting time is slightly higher because of more

availability of the calcium hydroxide to react. This

trend has changed with addition of silica fume, that is,

the IST and FST are reduced considerably because of

consumption of calcium hydroxide by silica fume at

the early stages as well as later stages. Sellevold

et al.32

observed that SF accelerates the hydration of

cement during the early stages by providing

nucleation sites where the products of cement

hydration can more readily precipitate from solution.

Semi-quantitative XRD analysis of composite pastes

Figures 2-5 show the XRD patterns of pastes of all

compositions at 3 and 28 days of curing and the

quantification of the various phases are given in Tables

4-7. The main crystalline phases of calcite

Table 3 — Mix proportions of specimens for mortars

Code of mix Cement

(kg/m3)

Silica Fume

(kg/m3)

Sand

(kg/m3)

Water

(kg/m3)

Lime water

(kg/m3)

Superplasticizer, (%)

Control 455 0 1364 181 - 0

CLD 455 0 1364 - 181 0

CLW 455 0 1364 - 181 0

CSF-10 410 45 1364 181 - 0

CSF-20 364 91 1364 181 - 0

CSF-30 319 136 1364 181 - 0

CLDSF-10 410 45 1364 - 181 1.0

CLDSF-20 364 91 1364 - 181 1.5

CLDSF-30 319 136 1364 - 181 2.0

CLWSF-10 410 45 1364 - 181 1.0

CLWSF-20 364 91 1364 - 181 1.5

CLWSF-30 319 136 1364 - 181 2.0

Fig. 1 — Initial and final setting times


495

(C- calcium carbonate, CaCO3), Portlandite

(P-calcium hydroxide, Ca(OH)2), ettringite (E), gypsum

(G), quartz (Q) are identified. The hydration reaction

products of cement such as calcium silicates/aluminates

such as C-S-H, C-A-S-H (gehlenite hydrate) including

tobermorite type C-S-H are also evidenced; since the

C-S-H, which is an amorphous phase, its structure

cannot be identified exclusively by XRD33

, hence it is

mentioned in the quantitative analysis tables (Tables

4-7) as ‘total amorphous contents’ by using TOPAS

academic software (Bruker AXS, Karlsruhe, Germany).

The semi-quantitative analyses of XRD of composites

show that the reduction in Portlandite peaks (CH

crystals), hence the improvement in the C-S-H quantities

in the presence of silica fume at different ages.

The XRD patterns and S-Q analysis of hydration of

cement pastes of control, CLD and CLW samples are

shown in Fig. 2 and Table 4 gives their quantification

values. It is found that the amounts of crystalline

portlandite contents are almost same in all the mixes. It

shows that the availability of portlandite crystals is

more to react with cementitious additives, if any.

Similarly, the total quantity of amorphous contents

such as C-S-H, C-A-H and C-A-S-H etc are equal in all

the cases of mixes. But in the case of samples CSF-10,

CSF-20 and CSF-30, wherein potable water is used, it

is noticed that the consumption of CH crystal

(Table 5 and Fig. 3) and accordingly observed the

incremental quantity of amorphous contents in these

cases and reduction of CH peaks in the XRD spectrum.

In these cases, there are existence of CH peaks with

Fig. 2 — XRD patterns of Control, CLD and CLW samples for 3

and 28 days

Fig. 3 — XRD patterns of Control, CSF-10, CSF-20 and CSF-30

samples for 3 and 28 days

Fig. 4 — XRD patterns of CLDSF-10, CLDSF-20and CLDSF-

30samples for 3 and 28 days

Fig. 5 — XRD patterns of CLWSF-10, CLWSF-20 and CLWSF-

30 samples for 3 and 28 days


496

10% and 20% of SF, but complete consumption is

found in 30% SF replacement in 3 days and 28 days of

curing. These results are supported by those of Ono

et al.34

, studied the cement-silica fume system in pastes

and the amounts of CH present after various periods of

hydration with different dosages of silica fume. At very

high dosages, almost all CH is consumed by 28 days,

but at 10% replacement of silica fume, CH is reduced

only by about 50% at 28 days, because of less

availability of SF to react with CH solution. Similar

result has also been observed by Hooton35

that with

20% by volume silica fume replacement, no CH was

detectable after 91 days of moist curing at 23°C, while

10% silica fume reduced CH by 50% at the same age.

In the case of saturated lime water, it is found that

the CH crystals for 3 days and 28 days of curing

samples, because of less dosage of SF, its consumption

also less. Whereas 20% and 30% SF replacement, the

consumption of CH is almost completed and there are

no CH crystal for further reaction (Fig. 4 and Table 6).

Simultaneously, the incremental quantity of amorphous

contents is also found in the case of CLWSF series too

(Table 7 and Fig. 5).

Hence, it is concluded from the XRD analysis,

there are two stages of CH crystal consumption and

enhancement in quantity of C-S-H and the like

materials, which lead to enhancement of strength of

mortar/concrete with similar composition. In the XRD

Table 4 — S-Q analysis for hydration of paste composites CON,

CLD and CLW series

Compounds 3 days 28 days

Control CLD CLW Control CLD CLW

Calcite (C) 16.69 11.51 11.19 11.91 12.19 15.12

Ettringite (E) 1.11 2.05 1.26 0.92 1.13 0.364

Gypsum (G) 3.69 3.69 3.39 3.61 4.39 4.12

Portlandite (P) 12.57 11.51 12.58 19.09 17.97 15.11

Quartz (Q) 1.37 0.84 1.03 0.65 1.22 1.1

Other amorphous

contents including

C-S-H, C-A-S-H etc

64.57 70.42 70.55 63.82 63.1 64.19

Table 5 — S-Q analysis for hydration of paste composites Control and CSF series


Control CSF-10 CSF-20 CSF-30 Control CSF-10 CSF-20 CSF-30

Calcite (C) 16.69 12.06 6.83 11.79 11.91 9.67 11.89 12.55

Ettringite (E) 1.11 2.04 3.57 0 0.92 3.13 4.89 4.38

Gypsum (G) 3.69 3.35 0 0 3.61 2.39 0 0

Portlandite (P) 12.57 7.22 2.39 1.1 19.09 7.11 4.54 0

Quartz (Q) 1.37 0.61 0.44 0.55 0.65 1.47 0 0

Other amorphous contents including

C-S-H, C-A-S-H etc

64.57 75.72 86.77 86.56 63.82 76.23 78.68 83.07

Table 6 — S-Q analysis for hydration of paste composites CLDSF series


CLDSF-10 CLDSF-20 CLDSF-30 CLDSF-10 CLDSF-20 CLDSF-30

Calcite (C) 24.95 11.43 9.58 12.27 9.76 12.33

Ettringite (E) 1.02 3.36 2.52 0.64 4.02 2.09

Gypsum (G) 3.43 3.04 0 4.15 4.18 0

Portlandite (P) 5.15 1.86 0 9.15 0 0

Quartz (Q) 1.89 0.47 0 0.52 0.24 0.29


C-S-H, C-A-S-H etc

63.565 77.84 87.9 73.28 81.8 85.29

Table 7 — S-Q analysis for hydration of paste composites CLWSF series


CLWSF-10 CLWSF-20 CLWSF-30 CLWSF-10 CLWSF-20 CLWSF-30

Calcite (C) 12.65 6.99 8.54 10.44 9.79 15.37

Ettringite (E) 3.35 3.59 3.15 3.69 3.1 2.51

Gypsum (G) 3.45 1.02 0.64 4.01 2.64 1.88

Portlandite (P) 9.51 5.51 0.55 9.27 4.02 0.64

Quartz (Q) 0.64 0.25 0.2 0.17 0.95 0.2


C-S-H, C-A-S-H etc

68.4 79.66 88.31 71.42 79.14 82.75


497

analysis of all the mixes shown that the quantity of

calcite throughout equally, which act as an inert filler

material and mere presence of numerous fine

particles-whether pozzolanic or not, it has an

accelerating effect on the cement hydration.

Compressive strength development for mortar mixes

It is observed that there is no change in the

compressive strength while using lime waters (CLD

and CLW) alone, whereas there is a considerable

strength gain for the samples CSF10, 20 and 30 with

potable water (W) than control for all the days, viz., 3,

28 and 90 days of curing. The early strength gain for

the cases of CLDSF and CLWSF series is observed

over control mortars, particularly a strength gain in

the range of 13-34% for the samples CLDSF-30 and

CLWSF-30. This trend is continuing up to 28 days of

curing. This is evident that the increase in percentage

addition of SF attributes to increase the early strength

of the cement mortar cubes when compared to 3rd day

strengths of control mortars.

As predicted by the Nazari and Riahi25

, the reduction

in the strength of cementitious composites with lime

water curing is observed in this study due to more

availability of Ca(OH)2 presence. The increase of

compressive strength is noticed in two stages, viz., early

(3-day) and later day strength (90-day) compared to

control mortars. This is due to the early consumption of

added calcium hydroxide solution by silica fume to form

additional C-S-H. This has been confirmed by semi-

quantitative analysis of XRD of cement composite

pastes of similar mix proportions. There is a continual

improvement of compressive strength observed for 28

days cured samples. After 28 days, the hydration

reaction of cementitious composites are almost

saturated, the subsequent strength gain is observed to be

generally low. But in the second stage, that is 90 days

cured samples, the further strength increments observed

because of consumption of the by-product of cement

hydration, namely the calcium hydroxide by silica fume.

It is also noted that the saturated lime water (CLDSF

series) with 20% silica fume (strength gain of 17% over

control) and natural lime water (CLWDSF series) with

30% silica fume replacements (strength gain of 16%)

provided higher compressive strength compared to

control mortars (Fig. 6). This incremental effect could be

due to the additional formation of C-S-H in the cement

moiety during subsequent hydration.

Split strength development for mortar mixes

Development of split tensile strengths of cylinder

mortars incorporating lime water and SF are higher

than the samples without SF and lime water. The split

tensile strength enhancement for lime water influenced

binary blended cementitious composite show 21-28%

over control samples after 28 days curing. That is, for

both the types of composites, as the compressive

strength increases, the tensile strength also increases

(Fig. 7). It is observed from this study, the early

strength gain is almost similar to the control samples,

whereas 28 days split tensile strength, increment in

strength is observed. This shows a clear indication of

improved binding properties between the blended

composites such as cement-SF-lime water.

Conclusions

This work is a preliminary investigation to study the

effect of two different lime water on the properties of

silica fume blended cementitious composites. The use of

lime water with silica fume mixed Portland cement

based composites affects both setting time and

compressive and split strengths of the mortar specimens.

Fig. 6 — Comparison of compressive strength of various

composite mortars for 3, 28 and 90 days

Fig. 7 — Comparison of split tensile strength of composite

mortars for 7 and 28 days


498

Based on the experimental results and S-Q analysis of

XRD analysis, the following conclusions can be drawn:

(i) Lime waters mixed with silica fume blended

cementitious composites enhances both initial and

final setting times due to the faster hydration in the

composite system than control mixes.

(ii) Portland cement based mixes with lime water

and SF consume more quantity of calcium hydroxide

compared with ordinary potable water as per the

XRD analysis.

(iii) The qualitative and quantitative S-Q analysis

of lime water influenced cementitious composite

pastes have been carried out. The results revealed that

the reduction in CH because of its consumption by

silica fume and additional formation of strength

giving amorphous phases including C-S-H.

(iv) The combined use of both lime water and

partial replacement of cement by silica fume

improves the compressive strength in two stages, viz.,

at early age and at latter age.

(v) 13-17% on 3 days, 23-25% on 28 days and 15-

17% on 90 days increase of compressive strength is

observed over control mixes of 30% replacement of cement

by SF when replacing potable water with lime waters.

(vi) 21-28 % increased split tensile strength at 28

days of curing gives the samples for CLDSF and

CLWSF series compared to control samples, which

are due to the improved binding properties between

the composite materials.

(vii) The results showed that the complete

consumption of SF by excess lime water when blended

with cement and enhancement of compressive and split

strength of the composite mortars.

Acknowledgements

The researchers of CSMG, AML and STL of

CSIR-SERC are greatly acknowledged for the useful

discussion and suggestions provided during the course

of the investigations.

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for use with Lime. ASTM C593-95, 1995, West Conshohocken,

PA: American Society of Testing and Materials.

2 Malhotra V M, Concr Int, 21(1999) 61-66.

3 Malhotra V M, Concr Int, 24 (2002) 22.

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Effect of lime water on the properties of silica fume ...nopr.niscair.res.in/bitstream/123456789/43705/1/IJEMS 24(6) 491-49… · This study is to investigate the setting time and

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