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binder ratio and nano-silica dosage on the fresh and hardened properties of self-compacting concrete
Construction and Building Materials 165 (2018) 504–513
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
The effect of different water/binder ratio and nano-silica dosage on the fresh and hardened properties of self-compacting concrete Nadine Hani a,⇑, Omar Nawawy a, Khaled S. Ragab b, Mohamed Kohail a a b
Structural Engineering Department, Ain Shams University, Cairo, Egypt Concrete Structures Department, Housing and Building National Research Center, Cairo, Egypt
h i g h l i g h t s Studying the effect of increasing w/b on properties of SCC with nano-silica. Different effect of nano-silica on hardened properties of low and high w/b SCC. Nano-silica dosage is critical for SCC fresh properties.
a r t i c l e
i n f o
Article history: Received 21 September 2017 Received in revised form 3 January 2018 Accepted 6 January 2018
Keywords: Nano-silica Self-compacting concrete Durability Fresh properties Mechanical properties Filler effect
a b s t r a c t This paper aims to study the effect of increasing water/binder ratio on the fresh and hardened properties of self-compacting concrete containing nano-silica with different dosages, focusing on the mixes with high w/b ratios that are produced in the field in places with hot weather. 12 mixes were designed with a total binder content of 350 kg/m3, three different water/binder (w/b) ratios of 0.41, 0.45 and 0.5 and 0%, 0.25%, 0.5% and 0.75% (by weight) replacement of cement by nano-silica. Self-compacting concrete was examined concerning fresh state properties and hardened state properties (mechanical and durability properties). Also, the densification of the microstructure of hardened concrete was verified by SEM examinations. The results showed that the effect of a certain nano-silica dosage on compressive strength of concrete with high w/b is greater than that on concrete with low w/b. While concerning durability, the results proved that the influence of a certain nano-silica dosage on low w/b mixes is greater than that on high w/b mixes. Also, the results showed that for mixes with high w/b, the nano-silica cannot compensate the significant decrease in durability caused by increasing w/b but can compensate only the strength reduction and segregation. Ó 2018 Elsevier Ltd. All rights reserved.
1. Introduction Concrete is a porous material; this makes it susceptible to the entrance of water or other liquids which cause durability problems. Many concrete structures built decades ago were often designed with little attention to durability issues, and have therefore suffered severe structural degradation [1]. Nanotechnology has become widely spread in the field of construction because it can improve construction materials performance since it can modify or cater the microstructures at nano- and micro-levels. As such, there is an increasing number of studies on using nanoparticles to enhance concrete properties among which nano-silica (NS) is quite ⇑ Corresponding author. E-mail addresses: [email protected] (N. Hani), [email protected]. edu.eg (O. Nawawy), [email protected] (K.S. Ragab), [email protected] (M. Kohail). https://doi.org/10.1016/j.conbuildmat.2018.01.045 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved.
outstanding. According to previous studies, it has been reported that the addition of NS decreases the permeability and increases the compressive strength of concrete because it has not only filler effect in which it fills the voids in the C-S-H gel, but also form nanostructured C-S-H gel material and thus improving the microstructure [2–14]. Also, NS possesses a special pozzolanic reaction due to its small particle size which provides larger surface area so accelerates the rate of hydration of cement thus increases the density of the internal transition zone between paste and aggregate [2–4,15]. One of the most significant problems in placing concrete is compaction especially in confined zones due to the shortage of skilled labour. Lack of compaction has a negative effect on durability, and, hence, causes poor durability performance of reinforced concrete. For this purpose, self-compacting concrete (SCC) was first developed in Japan in 1988 [16]. SCC is concrete that can flow under its weight and fill the formwork, even in the presence of
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dense reinforcement, without the need of any vibration, while maintaining homogeneity [17]. It is characterised by its filling ability, passing ability and segregation resistance [17]. The high flowability of SCC is achieved by using superplasticisers or high range water reducing admixtures, high amounts of fines, and, sometimes viscosity modifying agents (to decrease bleeding and segregation). According to Audenaert et al. [18], the presence of high amount of fines makes the pore structure of SCC different from that of ordinary concrete; therefore, the application of SCC might be slightly risky due to the lack of knowledge concerning its durability. In hot weather such as in Egypt, if the rate of evaporation is greater than the rate of bleeding, plastic shrinkage occurs causing concrete cracking [19–21]. Therefore, in spite of using superplasticiser to achieve the desired flowability, there is still a need for high water/cement ratio, especially in hot weather. Yakoubi et al. [21] found that increasing W/C of SCC in hot weather may provide some protection at least in early age. He explained that by using high W/ C, bleeding occurs which ensures the necessary moisture for hardening and it can be the natural self-cure of the surface, especially during the first hours. The influence of hot weather on the properties of fresh cement pastes was also reported by others [22,23]. Presently, only a few studies on the effect of NS on the durability of SCC are available [24–26]. Also, the effect of increasing w/b on SCC containing NS has not been previously reported. The objective of this study is to investigate the effect of increasing water/binder ratio on the fresh and hardened properties of selfcompacting concrete containing nano-silica with different dosages, focusing on the mixes with high w/b ratios that are produced in the field in places with hot weather such as Egypt. Self-compacting concrete was examined concerning fresh state properties and hardened state properties (mechanical and durability properties). Also, the densification of the microstructure of hardened concrete was verified by SEM examinations. 2. Materials and experimental procedure 2.1. Materials This study used an ASTM type I Portland cement (CEM I/42.5 R) to produce SCC mixtures. Commercial nano-silica (NS) particles were used in powder form as a partial replacement for cement admixtures. Chemical analysis and physical properties of cement and NS are shown in Tables 1 and 2 respectively. Transmission electron microscopy (TEM) of NS particles is shown in Fig. 1; NS particles are represented by highly agglomerated clusters. Fig. 2 shows the XRD pattern which indicated that NS is a highly amorphous material. Crushed limestone was used as coarse aggregate with a nominal maximum size of 10 mm with bulk density and specific gravity of 1493 kg/m3 and 2.67 respectively. The fine aggregate used was a mixture of limestone powder (as a filler)
Table 1 Chemical composition of cement and nano-silica (NS). Chemical analysis (%)
Cement
NS
SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 CL Tio2 In residue Loss of ignition
22.74 3.22 3.72 63.1 1.56 0.62 0.39 0.37 1.88 – 0.33 1.9
90.9 0.29 0.1 0.19 0.15 – 1.1 1.16 – 0.29 – 5.71
Table 2 Physical properties of cement and nano-silica (NS). Physical property
Cement
NS
Specific gravity Soundness (mm) Initial setting time (min) Compressive strength (Mpa) (2days) Compressive strength (Mpa) (28 days) Diameter (nm) Surface area (m2/g)
3.15 7 70 21.3 54.1 – 0.323
– – – – – 7–25 240
and sand with a maximum size of 4.75 mm. The bulk density and fineness modulus of sand used were 1636 kg/m3 and 2.632 respectively. The particle size distribution of filler, coarse and fine aggregates is shown in Fig. 3. To obtain the required workability in all concrete mixes, an aqueous solution of modified polycarboxylates superplasticiser (SP) (meeting the requirements for superplasticisers according to ASTM C 494 [27] Types G and F) with a specific gravity 1.08 was used at a constant dosage 2% by weight of cement. 2.2. Mix design proportions In this study, twelve SCC mixes were designed with a total binder content of 350 kg/m3 and three different water/binder (w/b) ratios of 0.41, 0.45 and 0.5 named series A, B and C respectively. Samples of each series were prepared with 0%, 0.25%, 0.5% and 0.75% (by weight) replacement of cement by NS. Table 3 shows the concrete mix designs for the samples. 2.3. Mixing procedure SCC mixtures were prepared by mixing coarse aggregates, fine aggregates, and powder materials (cement and nano-silica) in a laboratory drum mixer. The powder materials and the aggregates were mixed in dry form for 2 min. Then the whole amount of superplasticiser dissolved in half of the water was poured and mixed for 3 min. After that, about 1 min rest was enabled and finally the rest of the water was added and mixed for 1 min [26,28]. 2.4. Preparation of the specimens, curing and test methods Once the mixing process was completed, tests were performed on the fresh concrete to determine the workability of SCC. The workability of SCC can be characterised by Filling ability (flowability), Passing ability and Segregation resistance. Self-compacting Concrete must meet the requirements of the three characteristics. In this study, fresh properties of SCC mixtures were examined through the slump flow test, V-funnel test, J-Ring test, and L-box test according to EFNARC [17] standards. The slump flow time ( T₅₀₀), slump flow diameter (D) and V-funnel flow time were measured to represent the filling ability. During the slump flow test, segregation was checked by visual inspection. The passing ability was determined by J-Ring flow time (T₅₀₀j), J-Ring blocking step (BJ), and L-box height ratio. Then all required specimens for hardened concrete tests were poured and cured according to EFNARC and The European Guidelines for Self-Compacting Concrete standards [17,29]. All specimens were cast in one layer without any compaction. Compressive strengths at 7 and 28 days and splitting tensile strengths at 28 days were determined on Ø100 200 mm cylindrical specimens from each mixture according to ASTM C 39 [30] and ASTM C 496 [31] respectively. The effect of NS on the durability of SCC was investigated by conducting many tests including; water penetration depth, abrasion resistance, water sorptivity, volume of permeable voids (VPV), water absorption and sulphate attack.
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Fig. 1. TEM photographs of NS. (a) NS particles as received. (b) High magnification of NS particles.
to DIN 52108 [34]. The water absorption and VPV tests were conducted on Ø100 50 mm specimens following ASTM C 642 standard [35]. Finally, the sulphate attack for 100 100 100 mm cubic specimens was determined by immersing in 5% sulfuric acid solution for 28 days. The mass loss every 7 days and the loss in compressive strength after 28 days were reported [36,37]. For each test, the mean value of testing three specimens per mix was reported. The fracture surfaces of the cylindrical specimens after the compressive strength test were collected for microstructural analysis.
SiO2
Counts/s
SiO2
20
10
3. Results and discussion 0
3.1. Fresh concrete tests 20
30
40
Position [°2Theta] Fig. 2. XRD pattern of NS.
Fig. 3. Particle size distribution of filler, coarse and fine aggregates.
The rate of capillary absorption (sorptivity) besides the water penetration depth was used to investigate the permeability of tested SCC mixes. Sorptivity test was conducted on Ø100 50 m m specimens according to ASTM C 1585 [32]. According to DIN 1048 part 5 [33], the penetration depth for 150 150 150 mm cubic specimens exposed from below to a water pressure of 0.5 N/mm2 for 3 days was measured. Prepared 70 70 70 mm specimens were tested to determine the abrasion resistance according
The test results performed on fresh concrete are listed in Table 4. The control mix A-0% fulfil the EFNARC requirements for SCC. The mixes with higher w/b ratio B-0% and C-0% have as expected rheological properties out of the range of SCC as shown in Fig. 4 and Table 4. Also, little bleeding and segregation were observed for these mixes. NS as all fine materials decreases the flowability of mixes [14,38]. Addition of 0.75% NS decreased the slump flow of SCC with w/b = 0.41, w/b = 0.45 and w/b = 0.5 by 15.2%, 15.5% and 14.1 respectively. The mix A-0.75% with a high dosage of NS could not be considered as SCC as shown in Table 4. The NS with its large surface area can compensate the decrease of viscosity, bleeding and segregation in mixes with high w/b such as B and C mixes and returns them to the range of SCC. According to EFNARC [17] if a mix cannot be considered as SCC because it has too high viscosity it is suggested to increase water content in the mix or increase the dosage of superplasticiser or increase the paste volume. The decrease in SCC workability due to replacement by NS was also reported by previous studies [39,40]. The first approach for solving the workability problem is to increase w/b. Quercia et al. [41] found that for one SCC mix with a NS type of higher specific surface area than other types used in that study, more water was needed to have workability in the specific range and W/C ratio was increased from 0.45 to 0.5. Zaki et al. [14] found that concrete containing NS requires an additional amount of water or superplasticiser to maintain the same workability level. Others [5,42–44] studied the viscosity of cement pastes and mortars containing NS and it was found that they needed more water in order to maintain the workability of mixtures constant. However, NS dosage has to be optimized with w/b to produce
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N. Hani et al. / Construction and Building Materials 165 (2018) 504–513 Table 3 Mix designs of SCC mixtures. kg/m3
Series
Concrete ID
W/b
NS (%)
Cement
Fine aggregate
Coarse aggregate
Limestone
NS
Water
Sp
A
A-0% A-0.25% A-0.5% A-0.75% B-0% B-0.25% B-0.5% B-0.75% C-0% C-0.25% C-0.5% C-0.75%
0.41
0 0.25 0.5 0.75 0 0.25 0.5 0.75 0 0.25 0.5 0.75
350 349.1 348.3 347.4 350 349.1 348.3 347.4 350 349.1 348.3 347.4
755 755 755 755 740 740 740 740 720 720 720 720
940 940 940 940 922 922 922 922 900 900 900 900
219 219 219 219 215 215 215 215 210 210 210 210
0 0.9 1.7 2.6 0 0.9 1.7 2.6 0 0.9 1.7 2.6
143.5 143.5 143.5 143.5 157.5 157.5 157.5 157.5 175 175 175 175
2% by weight of cement
Slump flow
J-Ring
T500 (s)
D (mm)
T500j (s)
Dj (mm)
Bj (mm)
B
C
0.45
0.5
Table 4 Fresh properties of SCC. Series
Concrete ID
V-funnel flow time (s)
V-funnel flow time (s) at 5 min
L-box H₂/H1
Visual inspection Bleeding
Segregation
1 0.92 0.87 0.88
U
U
5 8 9.5 10.6
1 1 1 0.9
U U
U U
0 +3
0.8 1
A
A-0% A-0.25% A-0.5% A-0.75%
1.6 2.8 5.5 6.3
790 775 720 670
3.1 3.3 6.3 7.6
775 765 690 660
10 10 10 11.25
6.6 10.7 12.2 16.9
8.2 15.6 17.2 28.6
0.91 0.88 0.83 0.67
B
B-0% B-0.25% B-0.5% B-0.75%
1.2 2 4 4.7
805 770 730 680
1.9 3.5 4.8 5.3
800 760 700 670
6.75 8 10 9
4.9 6.3 8.8 9.5
8 10 12 13.3
C
C-0% C-0.25% C-0.5% C-0.75% Acceptance criteria of SCC suggested by EFNARC
1 1.2 1.4 2.6
885 855 800 760
1.1 1.7 2.1 2.9
850 835 790 730
10 10 7.5 8
3.9 5 7.3 8
Min Max
2 5
650 800
0 10
6 12
Fig. 5. Limitations of w/b with different NS dosage. Fig. 4. Relation between slump flow and w/b.
SCC. In this study, more slump flow and L-box tests were conducted on various mixes to find out the limitations of w/b with different NS dosage (0%, 0.25%, 0.5%, 0.75%). For each NS dosage, the mix was made by very low water content then the water was increased gradually to find out the w/b that makes the mix fulfil SCC limits of EFNARC. Then the water content was increased again until bleeding and segregation happen and the slump flow diameter exceeds the limits of EFNARC. The test results are shown in Fig. 5. From this figure, there are 3 zones. In zone A, considering slump flow, concrete has excess water content in which bleeding
and segregation occur and NS content will not help improving the workability. In zone B, NS can improve the effect of increasing water in SCC. In zone C, NS will decrease the flowability of concrete and highly increase its viscosity in which this mix cannot be considered as SCC. The second approach is to increase superplasticiser dosage. Sobolev et al. [45] found that for each 1% of nano-silica added to a standard concrete composition, 0.21% additional superplasticiser is needed. Veerendrakumar et al. found that when NS was added to self-compacting mortar, superplasticiser required was increased as
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the NS addition rises. However, in this study the maximum dosage of superplasticiser was used for all mixes. The third approach is to increase paste volume by increasing cement or increasing the volume of fine aggregate to coarse aggregate. However, this is a new mix design, which requires a comprehensive study. 3.2. Hardened concrete: mechanical properties The average compressive strength of SCC specimens at 7, 28 days and the average splitting tensile strength at 28 days are given in Figs. 6–8. Adding NS for all mixes increased both compressive and tensile strength regardless of NS dosage and w/b. Adding NS can compensate the reduction in compressive strength caused by high w/b in series B and C mixes. The 28 days strength of B0.25% and C-0.5% are 29.2 MPa and 29.9 MPa respectively which is close to reference SCC A-0% (i.e., 29 MPa). This means that we can obtain the same strength by increasing w/b (needed in places with hot weather) and by adding NS. The influence of NS on compressive strength of weak concrete is greater than that on concrete with lower w/b as it increases compressive strength by 26.9%, 32.7% and 48.8% for w/b of 0.41, 0.45 and 0.5 respectively by 0.75% replacement of cement. The tensile to compressive strength ratio still almost the same in all mixes regardless the percentage of NS added. Therefore, it can be concluded that the NS particles have no special effect on the tensile strength that may be because of its rounded shape. The average ratio between compressive strength at 7 days to that of 28 days for mixes with 0% NS for all series is 77.5%, while that for mixes with 0.75% NS is 74%. The ratio in case of using NS is smaller because NS continuous its pozzolanic reaction as age increase. Strength improvement due to replacement by NS may be attributed to the fine particles, which filled the voids in cement paste and thus making the microstructure denser (filler effect). Also, the pozzolanic reaction of nanoparticles with free Ca(OH)2 which is formed during hydration of cement forming more C-S-H gel resulting in the improvement of mechanical properties. Others also reported enhancement of SCC due to NS addition [26,28,39]. 3.3. Hardened concrete: durability tests
Fig. 7. Compressive strengths at 28 days.
Fig. 8. Splitting tensile strengths.
0.75% NS for A-0.75%, B-0.75%, and C-0.75% samples. Du et al. [15] found that using 0.3% NS decreased water penetration depth of ordinary concrete by 56% at 28 days. Quercia et al. [25] found that the addition of 3.8% nano-silica reduced water penetration depth of SCC by about 88%.
3.3.1. Water penetration depth Fig. 9 shows water penetration depths of all SCC mixes. Adding NS for all mixes decreases the water penetration depth regardless of its dosage and w/b. The decrease for series A concretes is greater than that for series B and the decrease for series B concretes is greater than that for series C. The water penetration depth decreased by 43.5%, 37.8% and 29.5% due to replacement by
3.3.2. Abrasion resistance The mean loss in the thickness of the specimens is shown in Fig. 10. The abrasion resistance is determined as the mean loss in specimen thickness. Adding NS increases the abrasion resistance and decreases the thickness loss regardless of its dosage and w/b. The influence of a particular NS dosage on the abrasion resistance of SCC as increasing w/b is not consistent. Addition of 0.75% NS decreased abrasion resistance of SCC with w/b = 0.41, w/b = 0.45 and w//b = 0.5 by 46.2%, 38.3%, and 43.3%. The enhancement in
Fig. 6. Compressive strengths at 7 days.
Fig. 9. Water penetration depth of SCC at different w/b.
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abrasion resistance may be due to the formation of C-S-H that fills the pores, so concrete becomes denser.
3.3.3. Water sorptivity The rate of initial absorption (initial sorptivity) of all concrete mixes is shown in Figs. 11–13. The initial sorptivity is calculated as the slope of the line that is the best fit in the figures (R2 < 0.98). The rate of secondary absorption (secondary sorptivity) for all mixes could not be determined (R2 < 0.98). Fig. 14 shows summarised initial sorptivity values. The results are showing that incorporating NS in SCC decreases sorptivity values of SCC with low w/b. The decrease for series A concretes is greater than that for series B while for concretes with high w/b (series C) sorptivity showed a marginal decrease even with high NS dosage. For SCC with low w/b and high NS dosage like A-0.75% sample, the sorptivity decreased by large value reached to 48.5% due to replacement by 0.75% NS. The increase of w/b from 0.41 to 0.5 increased sorptivity by about 17.4%, which was not significantly decreased by using NS. The effect of incorporating NS on sorptivity is more significant in concrete with lower w/b than that with higher w/b. It seems because concretes with low w/b have pores that NS can fill, and the formed C-S-H gel can subdivide large pores into small pores thus the pore structure is refined or partially blocked. While concretes with high w/b have a high void content, so even if NS fills some of the voids they will still be weak and porous. This could be clear in the microstructure analysis, which is discussed later in the text. The reduced sorptivity due to incorporating NS was also reported by other findings [15,40,46].
Fig. 11. Water absorption of series A concretes (w/b = 0.41).
Fig. 12. Water absorption of series B concretes (w/b = 0.45).
3.3.4. Volume of permeable voids (VPV) and water absorption tests The total water absorption and volume of permeable voids are shown in Figs. 15 and 16. From the figures, it is clear that NS decreases the total absorption and volume of voids of SCC with low w/b (series A) while for concretes with high w/b (series B and C), the effect of NS on water absorption and volume of voids is insignificant. This may be because they contain large pores, which only subdivide into small pores by adding NS but the total pore volume is not changed [47]. For SCC with low w/b and high NS dosage like A-0.75% sample, the total absorption and volume of voids decreased again by large value reached to 16.2% and 13% respectively due to replacement by 0.75% NS. Du et al. [15] also found that by the addition of 0.3% and 0.9% nano-silica, the total absorption and water accessible porosity remained constant. Quercia et al. [25] also found that the addition of 3.8% nano-silica did not change the water permeable porosity, while the durability performances could be enhanced.
Fig. 10. Thickness loss due to abrasion for different w/b.
Fig. 13. Water absorption of series C concretes (w/b = 0.5).
Fig. 14. Sorptivity values of SCC at different w/b.
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Fig. 15. Total water absorption for different w/b.
Fig. 18. Compressive strength loss due to sulphate attack for different w/b.
sulphate hydrate, Afm) forming ettringite [48–51] which leads to expansion and deterioration of concrete. Replacement by NS improves the resistance to sulphate attack due to its pozzolanic activity reacting with Ca(OH)2 (so decreasing Ca(OH)2) forming a more C-S-H gel [6]. 3.4. Microstructural analysis
Fig. 16. Volume of permeable voids for different w/b.
3.3.5. Sulphate attack The mean loss of the compressive strength and mass of specimens after being in the sulfuric acid solution for 28 days are shown in Figs. 17and 18. It can be seen that for specimens with NS, the loss of strength and mass is lower than that without NS but with small values. Adding NS decreases the loss of strength and mass (which indicates an improvement of sulphate attack resistance) regardless of its dosage and w/b. Addition of 0.75% NS decreased the compressive strength loss of SCC with w/b = 0.41, w/b = 0.45 and w/b = 0.5 by 19.5%, 21.9% and 8.6%. The loss in mass may be misleading because it may be a loss in aggregate mass. It seems that the resistance to sulphate attack depends not only on the microstructure, the voids in the cement paste but also on the chemical composition. Ca(OH)2 reacts with sulphate ions forming gypsum, which reacts with calcium aluminates hydrates (mono-
Fig. 17. Mass loss due to sulphate attack for different w/b.
The objective of this analysis is to support findings in this research. Scanning Electron Microscopy (SEM) examinations were carried out to investigate the microstructure of A-0%, A-0.5%, A0.75%, C-0% and C-0.5% mixes. Fig. 19 shows the microstructure at interfacial transition zone and paste of mixes. For A-0% and C0% samples with no NS, It can be seen that the transition zone is very weak and porous, CH crystals and voids are noticed in the paste structure, C-S-H gel existed in isolation and also large voids are present in C-0% mix. Otherwise, the SEM of samples A-0.5% and A-0.75% showed a more dense and compact transition zone, the paste structure contains more homogeneous C-S-H gel, because of the pozzolanic reaction which turned CH into C-S-H, no pores were easily found. For C-0.5% mix, small pores were found and fewer CH crystals. 4. Conclusion This study experimentally determined durability, mechanical and rheological properties of self-compacting concrete using various NS dosages and w/b. The conclusions obtained from this study are summarised as follows: The positive effect of NS on compressive strength of SCC should not be taken as evidence of a similar effect on durability properties. The effect of NS addition on mechanical and durability properties of SCC with high w/b is different from that on SCC with low w/b. The influence of NS on compressive strength of high w/b concrete is greater than that on concrete with lower w/b. The test results proved that the influence of NS on the durability of low w/b mixes is greater than that on high w/b mixes except for abrasion resistance and sulphate attack, which showed that the effect of a certain NS dosage on SCC as increasing w/b is not consistent. NS improves mechanical properties of SCC with a significant loss in fresh properties. The addition of NS decreases the flowability, improves the consistency of SCC mixtures and makes SCC more viscous with no bleeding and segregation because of its large specific surface area.
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(1)
(a)
(2)
(3)
Weak ITZ Voids Aggregate CH Paste
(b)
CH
C-S-H
Weak ITZ C-S-H Aggregate
CH
CH
Large Void
Paste
CH CH C-S-H
Voids C-S-H
(c) Dense ITZ Homogeneous C-S-H
Paste
Aggregate
(d)
Homogeneous C-S-H
Dense ITZ
Paste
Homogeneous C-S-H
Aggregate
(e)
CH
Dense ITZ
Small pores
CH Small pores
Paste
C-S-H
Aggregate
C-S-H
CH
Fig. 19. Microstructure of SCC mixtures (a) A-0% mix, (b) C-0% mix, (c) A-0.5% mix, (d) A-0.75% mix, (e) C-0.5% mix at interfacial transition zone (series 1) and paste (series 2 and 3).
The NS dosage is critical for SCC. The high dose may decrease flowability under the SCC limits. Mechanical properties of SCC increase by increasing NS dosage, especially at later ages. For mixes with 0.75% NS, Compressive strength improved by 26.9%, 32.7% and 48.8% for w/b of 0.41, 0.45 and 0.5 respectively.
NS rounded particles have no special effect on tensile strength regardless the dosage. The durability of SCC enhanced in general by increasing NS dosage. Sorptivity, water absorption and volume of permeable voids for mixes with high w/b showed a marginal decrease even with 0.75% NS dosage.
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SEM analysis supports the findings of test results. It showed that NS significantly densified the microstructure of SCC with low w/b leading to a compact ITZ. For high w/b mixes, the NS cannot densify the microstructure the same way as low w/b mixes leading to a weak ITZ. Generally, for concrete with high w/b, NS can compensate deterioration of fresh and mechanical properties caused by high w/b but cannot compensate deterioration caused for durability. In comparison with previous works, the NS content concerning agglomeration is given which was not studied in this work. The NS content concerning agglomeration is critical, however it was not studied in this work. This is ongoing research study by the authors. Acknowledgements The authors would like to thank the technical staff of the Material Research Center (MRC) at the faculty of engineering Ain Shams University for help and hard work during the experimental phase of the research. The authors also appreciate the working team at Housing and Building National Research Center (HBRC). This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. References [1] L.C. Hollaway, Key issues in the use of fibre reinforced polymer (FRP) composites in the rehabilitation and retrofitting of concrete structures, Woodhead Publ. Ser. Civ. Struct. Eng. (2011) 3–74, https://doi.org/10.1533/ 9780857090928.1.3. [2] H. Li, H.G. Xiao, J. Yuan, J. Ou, Microstructure of cement mortar with nanoparticles, Compos. Part B: Eng. 35 (2004) 185–189, https://doi.org/10.1016/ S1359-8368(03)00052-0. [3] T. Ji, Preliminary study on the water permeability and microstructure of concrete incorporating nano-SiO2, Cem. Concr. Res. 35 (2005) 1943–1947, https://doi.org/10.1016/j.cemconres.2005.07.004. [4] H. Bahadori, P. Hosseini, Reduction of cement consumption by the aid of silica nano-particles (investigation on concrete properties), J. Civ. Eng. Manage. 18 (2012) 416–425, https://doi.org/10.3846/13923730.2012.698912. [5] Y. Qing, Z. Zenan, K. Deyu, C. Rongshen, Influence of nano-SiO2 addition on properties of hardened cement paste as compared with silica fume, Constr. Build. Mater. 21 (2007) 539–545, https://doi.org/10.1016/ j.conbuildmat.2005.09.001. [6] M. Heikal, S. Abd El Aleem, W.M. Morsid, Durability of composite cements containing granulated blast-furnace slag and silica nano-particles, Indian J. Eng. Mater. Sci. 23 (2016) 88–100. [7] M. Heikal, N.S. Ibrahim, Hydration, microstructure and phase composition of composite cements containing nano-clay, Constr. Build. Mater. 112 (2016) 19– 27, https://doi.org/10.1016/j.conbuildmat.2016.02.177. [8] M. Heikal, O.K. Al-Duaij, N.S. Ibrahim, Microstructure of composite cements containing blast-furnace slag and silica nano-particles subjected to elevated thermally treatment temperature, Constr. Build. Mater. 93 (2015) 1067–1077, https://doi.org/10.1016/j.conbuildmat.2015.05.042. [9] M. Heikal, M.N. Ismail, N.S. Ibrahim, Physico-mechanical, microstructure characteristics and fire resistance of cement pastes containing Al2O3 nanoparticles, Constr. Build. Mater. 91 (2015) 232–242, https://doi.org/10.1016/ j.conbuildmat.2015.05.036. [10] H. El-Didamony, M. Heikal, T.M. El-Sokkary, K.A. Khalil, I.A. Ahmed, Active belite b-C2S and the hydration of calcium sulfoaluminates prepared from nano-materials, Ceramics – Silikaty 58 (2014) 165–171. [11] M. Heikal, A.I. Ali, M.N. Ismail, S.A.N.S. Ibrahim, Behavior of composite cement pastes containing silica nano-particles at elevated temperature, Constr. Build. Mater. 70 (2014) 339–350, https://doi.org/10.1016/ j.conbuildmat.2014.07.078. [12] S.A. El Aleem, W.M. Morsi, M. Heikal, Hydration characteristics, thermal expansion and microstructure of cement pastes and mortars containing nanoSiO2, Constr. Build. Mater. 59 (2014) 151–160, https://doi.org/10.1016/ j.conbuildmat.2014.02.039. [13] M. Heikal, S. Abd El Aleem, W.M. Morsi, Characteristics of blended cements containing nano-silica, HBRC J. 9 (2013) 243–255, https://doi.org/10.1016/j. hbrcj.2013.09.001. [14] S.I. Zaki, Khaled S. Ragab, How nanotechnology can change concrete, in: 1st Int. Conf. Sustain. Built Environ. Infrastructures Dev. Ctries, 2009, pp. 407–414. [15] H. Du, S. Du, X. Liu, Durability performances of concrete with nano-silica, Constr. Build. Mater. 73 (2014) 705–712, https://doi.org/10.1016/ j.conbuildmat.2014.10.014. [16] H. Okamura, K. Ozawa, Self-compacting high performance concrete, Struct. Eng. Int. 6 (1996) 269–270, https://doi.org/10.2749/101686696780496292.
[17] EFNARC, in: Specification and Guidelines for Self-Compacting Concrete, Rep. from Eur. Fed. Spec. Constr. Chem. Concr. Syst., 2002, pp. 1–32. doi: 0 9539733 4 4. [18] K. Audenaert, V. Boel, G. De Schutter, Chloride migration in self compacting concrete, in: Proc. Fifth Int. Conf. Concr. under Sev. Cond. Environ. Load. (CONSEC’07), Tours, 4–6 June, 2007, pp. 291–298. [19] F.H. Wittmann, On the action of capillary pressure in fresh concrete, Cem. Concr. Res. 6 (1976) 49–56. [20] M. Al-Fadhala, K.C. Hover, Rapid evaporation from freshly cast concrete and the Gulf environment, Constr. Build. Mater. 15 (2001) 1–7, https://doi.org/ 10.1016/S0950-0618(00)00064-7. [21] I. Yakoubi, S. Aggoun, H. Ait Aider, H. Houari, The influence of bleeding, extra water and superplasticizer on the SCC plastic shrinkage cracking: case of hot weather, J. Adhes. Sci. Technol. 30 (2016), https://doi.org/10.1080/ 01694243.2016.1189869. [22] M. Heikal, M.S. Morsy, I. Aiad, Effect of treatment temperature on the early hydration characteristics of superplasticized silica fume blended cement pastes, Cem. Concr. Res. 35 (2005) 680–687, https://doi.org/10.1016/j. cemconres.2004.06.012. [23] M. Heikal, M. Morsy, Effect of Curing Temperature on the Electrical Resistivity and Rheological Properties of Superplastized Blended Cement Pastes, 2004. [24] A. Nazari, S. Riahi, The effects of SiO2 nanoparticles on physical and mechanical properties of high strength compacting concrete, Compos. Part B: Eng. 42 (2011) 570–578, https://doi.org/10.1016/j.compositesb.2010.09.025. [25] G. Quercia, P. Spiesz, G. Hüsken, H.J.H. Brouwers, SCC modification by use of amorphous nano-silica, Cem. Concr. Compos. 45 (2014) 69–81, https://doi.org/ 10.1016/j.cemconcomp.2013.09.001. [26] M. Jalal, E. Mansouri, M. Sharifipour, A.R. Pouladkhan, Mechanical, rheological, durability and microstructural properties of high performance selfcompacting concrete containing SiO2 micro and nanoparticles, Mater. Des. 34 (2012) 389–400, https://doi.org/10.1016/j.matdes.2011.08.037. [27] ASTM C 494, Standard Specification for Chemical Admixtures for Concrete, Am. Soc. Test. Mater., 2004. [28] M. Jalal, A. Pouladkhan, O.F. Harandi, D. Jafari, Comparative study on effects of Class F fly ash, nano silica and silica fume on properties of high performance self compacting concrete, Constr. Build. Mater. 94 (2015) 90–104, https://doi. org/10.1016/j.conbuildmat.2015.07.001. [29] The European Guidelines for Self Compacting Concrete, Specification, Production and Use, 2005, p. 68. [30] ASTM C 39, in: Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, Annu. B. ASTM Stand. Vol 04.02., 2003, pp. 1–5, https:// doi.org/10.1520/C0039. [31] ASTM C 496, in: Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimen, Annu. B. ASTM Stand. Vol 04.02., 2004, pp. 1–5. [32] ASTM C 1585, in: Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes, Annu. B. ASTM Stand. Vol 04.02., 2004, pp. 1–6, https://doi.org/10.1520/C1585-11.2. [33] DIN 1048 (Part-5), German Standard for Determination of Permeability of Concrete, 1991. [34] DIN 52108, Wear Test Using the Grinding Wheel According to Böhme, 2010. [35] ASTM C 642, in: Standard Test Method for Density, Absorption, and Voids in Hardened Concrete, Annu. B. ASTM Stand. Vol 04.02., 1997, pp. 1–3. [36] M. Nehdi, M.T. Bassuoni, M. Amin, Self-compacting concrete: using limestone to resist sulfuric acid, Proc. ICE – Constr. Mater. 160 (2007) 113–123, https:// doi.org/10.1680/coma.2007.160.3.113. [37] Z. Makhloufi, E.H. Kadri, M. Bouhicha, A. Benaissa, Resistance of limestone mortars with quaternary binders to sulfuric acid solution, Constr. Build. Mater. 26 (2012) 497–504, https://doi.org/10.1016/j.conbuildmat.2011. 06.050. [38] T. Bahaa, Effect of utilizing nano and micro silica on early properties of cement mortar, World Appl. Sci. J. 29 (2014) 370–382, https://doi.org/10.5829/idosi. wasj.2014.29.03.13862. [39] M.H. Beigi, J. Berenjian, O. Lotfi Omran, A. Sadeghi Nik, I.M. Nikbin, An experimental survey on combined effects of fibers and nanosilica on the mechanical, rheological, and durability properties of self-compacting concrete, Mater. Des. 50 (2013) 1019–1029, https://doi.org/10.1016/ j.matdes.2013.03.046. [40] S.W.M. Supit, F.U.A. Shaikh, Durability properties of high volume fly ash concrete containing nano-silica, Mater. Struct. (2014) 2431–2445, https://doi. org/10.1617/s11527-014-0329-0. [41] P. Spiesz, H.J.H. Brouwers, in: Effects of Nano-silica (NS) Additions on Durability of SCC Mixture, 2015, pp. 169–178, https://doi.org/10.1007/9783-319-09921-7. [42] L. Senff, J.A. Labrincha, V.M. Ferreira, D. Hotza, W.L. Repette, Effect of nanosilica on rheology and fresh properties of cement pastes and mortars, Constr. Build. Mater. 23 (2009) 2487–2491, https://doi.org/10.1016/ j.conbuildmat.2009.02.005. [43] K.L. Lin, W.C. Chang, D.F. Lin, H.L. Luo, M.C. Tsai, Effects of nano-SiO2 and different ash particle sizes on sludge ash-cement mortar, J. Environ. Manage. 88 (2008) 708–714, https://doi.org/10.1016/j.jenvman.2007.03.036. [44] J. Björnström, A. Martinelli, A. Matic, L. Börjesson, I. Panas, Accelerating effects of colloidal nano-silica for beneficial calcium-silicate-hydrate formation in cement, Chem. Phys. Lett. 392 (2004) 242–248, https://doi.org/10.1016/j. cplett.2004.05.071. [45] K. Sobolev, I. Flores, R. Hermosillo, L.M. Torres-Martínez, Nanomaterials and Nanotechnology for High-Performance Cement Composites, 2008.
N. Hani et al. / Construction and Building Materials 165 (2018) 504–513 [46] A. Najigivi, S. Abdul Rashid, F. Nora, A. Aziz, M.A. Mohd Salleh, Water absorption control of ternary blended concrete with nano-SiO2 in presence of rice husk ash, Mater. Struct. 45 (2012) 1007–1017, https://doi.org/10.1617/ s11527-011-9813-y. [47] V. Yogendran, B. Langan, Utilization of silica fume in high strength concrete, Util. High Strength Concr. Stavanger, Tapir Publ., Trondheim, 1987. [48] M. Abd, S. Abd, M. Heikal, H. El Didamony, Hydration and durability of sulphate-resisting and slag cement blends in Caron’s Lake water, Cem. Concr. Res. 35 (2005) 1592–1600, https://doi.org/10.1016/j.cemconres.2004.06.038. [49] H. El-Didamony, M. Heikal, S. Al-Masry, Effect of delaying addition time of SMF superplasticizer on hydration characteristics of blended cement pastes, Constr.
513
Build. Mater. 35 (2012) 261–269, https://doi.org/10.1016/ j.conbuildmat.2012.02.068. [50] I. Aiad, H. El-Didamony, M. Heikal, S. Al-Masry, Effect of delayed addition time of synthesized SSPF condensate on the durability of sulphate resisting cement pastes incorporating micro-silica, Constr. Build. Mater. 48 (2013) 1092–1103, https://doi.org/10.1016/j.conbuildmat.2013.07.067. [51] H.N. Atahan, D. Dikme, Use of mineral admixtures for enhanced resistance against sulfate attack, Constr. Build. Mater. 25 (2011) 3450–3457, https://doi. org/10.1016/j.conbuildmat.2011.03.036.
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The effect of different water/binder ratio and nano-silica dosage on the fresh and hardened properties of self-compacting concrete Nadine Hani a,⇑, Omar Nawawy a, Khaled S. Ragab b, Mohamed Kohail a a b
Structural Engineering Department, Ain Shams University, Cairo, Egypt Concrete Structures Department, Housing and Building National Research Center, Cairo, Egypt
h i g h l i g h t s Studying the effect of increasing w/b on properties of SCC with nano-silica. Different effect of nano-silica on hardened properties of low and high w/b SCC. Nano-silica dosage is critical for SCC fresh properties.
a r t i c l e
i n f o
Article history: Received 21 September 2017 Received in revised form 3 January 2018 Accepted 6 January 2018
Keywords: Nano-silica Self-compacting concrete Durability Fresh properties Mechanical properties Filler effect
a b s t r a c t This paper aims to study the effect of increasing water/binder ratio on the fresh and hardened properties of self-compacting concrete containing nano-silica with different dosages, focusing on the mixes with high w/b ratios that are produced in the field in places with hot weather. 12 mixes were designed with a total binder content of 350 kg/m3, three different water/binder (w/b) ratios of 0.41, 0.45 and 0.5 and 0%, 0.25%, 0.5% and 0.75% (by weight) replacement of cement by nano-silica. Self-compacting concrete was examined concerning fresh state properties and hardened state properties (mechanical and durability properties). Also, the densification of the microstructure of hardened concrete was verified by SEM examinations. The results showed that the effect of a certain nano-silica dosage on compressive strength of concrete with high w/b is greater than that on concrete with low w/b. While concerning durability, the results proved that the influence of a certain nano-silica dosage on low w/b mixes is greater than that on high w/b mixes. Also, the results showed that for mixes with high w/b, the nano-silica cannot compensate the significant decrease in durability caused by increasing w/b but can compensate only the strength reduction and segregation. Ó 2018 Elsevier Ltd. All rights reserved.
1. Introduction Concrete is a porous material; this makes it susceptible to the entrance of water or other liquids which cause durability problems. Many concrete structures built decades ago were often designed with little attention to durability issues, and have therefore suffered severe structural degradation [1]. Nanotechnology has become widely spread in the field of construction because it can improve construction materials performance since it can modify or cater the microstructures at nano- and micro-levels. As such, there is an increasing number of studies on using nanoparticles to enhance concrete properties among which nano-silica (NS) is quite ⇑ Corresponding author. E-mail addresses: [email protected] (N. Hani), [email protected]. edu.eg (O. Nawawy), [email protected] (K.S. Ragab), [email protected] (M. Kohail). https://doi.org/10.1016/j.conbuildmat.2018.01.045 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved.
outstanding. According to previous studies, it has been reported that the addition of NS decreases the permeability and increases the compressive strength of concrete because it has not only filler effect in which it fills the voids in the C-S-H gel, but also form nanostructured C-S-H gel material and thus improving the microstructure [2–14]. Also, NS possesses a special pozzolanic reaction due to its small particle size which provides larger surface area so accelerates the rate of hydration of cement thus increases the density of the internal transition zone between paste and aggregate [2–4,15]. One of the most significant problems in placing concrete is compaction especially in confined zones due to the shortage of skilled labour. Lack of compaction has a negative effect on durability, and, hence, causes poor durability performance of reinforced concrete. For this purpose, self-compacting concrete (SCC) was first developed in Japan in 1988 [16]. SCC is concrete that can flow under its weight and fill the formwork, even in the presence of
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dense reinforcement, without the need of any vibration, while maintaining homogeneity [17]. It is characterised by its filling ability, passing ability and segregation resistance [17]. The high flowability of SCC is achieved by using superplasticisers or high range water reducing admixtures, high amounts of fines, and, sometimes viscosity modifying agents (to decrease bleeding and segregation). According to Audenaert et al. [18], the presence of high amount of fines makes the pore structure of SCC different from that of ordinary concrete; therefore, the application of SCC might be slightly risky due to the lack of knowledge concerning its durability. In hot weather such as in Egypt, if the rate of evaporation is greater than the rate of bleeding, plastic shrinkage occurs causing concrete cracking [19–21]. Therefore, in spite of using superplasticiser to achieve the desired flowability, there is still a need for high water/cement ratio, especially in hot weather. Yakoubi et al. [21] found that increasing W/C of SCC in hot weather may provide some protection at least in early age. He explained that by using high W/ C, bleeding occurs which ensures the necessary moisture for hardening and it can be the natural self-cure of the surface, especially during the first hours. The influence of hot weather on the properties of fresh cement pastes was also reported by others [22,23]. Presently, only a few studies on the effect of NS on the durability of SCC are available [24–26]. Also, the effect of increasing w/b on SCC containing NS has not been previously reported. The objective of this study is to investigate the effect of increasing water/binder ratio on the fresh and hardened properties of selfcompacting concrete containing nano-silica with different dosages, focusing on the mixes with high w/b ratios that are produced in the field in places with hot weather such as Egypt. Self-compacting concrete was examined concerning fresh state properties and hardened state properties (mechanical and durability properties). Also, the densification of the microstructure of hardened concrete was verified by SEM examinations. 2. Materials and experimental procedure 2.1. Materials This study used an ASTM type I Portland cement (CEM I/42.5 R) to produce SCC mixtures. Commercial nano-silica (NS) particles were used in powder form as a partial replacement for cement admixtures. Chemical analysis and physical properties of cement and NS are shown in Tables 1 and 2 respectively. Transmission electron microscopy (TEM) of NS particles is shown in Fig. 1; NS particles are represented by highly agglomerated clusters. Fig. 2 shows the XRD pattern which indicated that NS is a highly amorphous material. Crushed limestone was used as coarse aggregate with a nominal maximum size of 10 mm with bulk density and specific gravity of 1493 kg/m3 and 2.67 respectively. The fine aggregate used was a mixture of limestone powder (as a filler)
Table 1 Chemical composition of cement and nano-silica (NS). Chemical analysis (%)
Cement
NS
SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 CL Tio2 In residue Loss of ignition
22.74 3.22 3.72 63.1 1.56 0.62 0.39 0.37 1.88 – 0.33 1.9
90.9 0.29 0.1 0.19 0.15 – 1.1 1.16 – 0.29 – 5.71
Table 2 Physical properties of cement and nano-silica (NS). Physical property
Cement
NS
Specific gravity Soundness (mm) Initial setting time (min) Compressive strength (Mpa) (2days) Compressive strength (Mpa) (28 days) Diameter (nm) Surface area (m2/g)
3.15 7 70 21.3 54.1 – 0.323
– – – – – 7–25 240
and sand with a maximum size of 4.75 mm. The bulk density and fineness modulus of sand used were 1636 kg/m3 and 2.632 respectively. The particle size distribution of filler, coarse and fine aggregates is shown in Fig. 3. To obtain the required workability in all concrete mixes, an aqueous solution of modified polycarboxylates superplasticiser (SP) (meeting the requirements for superplasticisers according to ASTM C 494 [27] Types G and F) with a specific gravity 1.08 was used at a constant dosage 2% by weight of cement. 2.2. Mix design proportions In this study, twelve SCC mixes were designed with a total binder content of 350 kg/m3 and three different water/binder (w/b) ratios of 0.41, 0.45 and 0.5 named series A, B and C respectively. Samples of each series were prepared with 0%, 0.25%, 0.5% and 0.75% (by weight) replacement of cement by NS. Table 3 shows the concrete mix designs for the samples. 2.3. Mixing procedure SCC mixtures were prepared by mixing coarse aggregates, fine aggregates, and powder materials (cement and nano-silica) in a laboratory drum mixer. The powder materials and the aggregates were mixed in dry form for 2 min. Then the whole amount of superplasticiser dissolved in half of the water was poured and mixed for 3 min. After that, about 1 min rest was enabled and finally the rest of the water was added and mixed for 1 min [26,28]. 2.4. Preparation of the specimens, curing and test methods Once the mixing process was completed, tests were performed on the fresh concrete to determine the workability of SCC. The workability of SCC can be characterised by Filling ability (flowability), Passing ability and Segregation resistance. Self-compacting Concrete must meet the requirements of the three characteristics. In this study, fresh properties of SCC mixtures were examined through the slump flow test, V-funnel test, J-Ring test, and L-box test according to EFNARC [17] standards. The slump flow time ( T₅₀₀), slump flow diameter (D) and V-funnel flow time were measured to represent the filling ability. During the slump flow test, segregation was checked by visual inspection. The passing ability was determined by J-Ring flow time (T₅₀₀j), J-Ring blocking step (BJ), and L-box height ratio. Then all required specimens for hardened concrete tests were poured and cured according to EFNARC and The European Guidelines for Self-Compacting Concrete standards [17,29]. All specimens were cast in one layer without any compaction. Compressive strengths at 7 and 28 days and splitting tensile strengths at 28 days were determined on Ø100 200 mm cylindrical specimens from each mixture according to ASTM C 39 [30] and ASTM C 496 [31] respectively. The effect of NS on the durability of SCC was investigated by conducting many tests including; water penetration depth, abrasion resistance, water sorptivity, volume of permeable voids (VPV), water absorption and sulphate attack.
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Fig. 1. TEM photographs of NS. (a) NS particles as received. (b) High magnification of NS particles.
to DIN 52108 [34]. The water absorption and VPV tests were conducted on Ø100 50 mm specimens following ASTM C 642 standard [35]. Finally, the sulphate attack for 100 100 100 mm cubic specimens was determined by immersing in 5% sulfuric acid solution for 28 days. The mass loss every 7 days and the loss in compressive strength after 28 days were reported [36,37]. For each test, the mean value of testing three specimens per mix was reported. The fracture surfaces of the cylindrical specimens after the compressive strength test were collected for microstructural analysis.
SiO2
Counts/s
SiO2
20
10
3. Results and discussion 0
3.1. Fresh concrete tests 20
30
40
Position [°2Theta] Fig. 2. XRD pattern of NS.
Fig. 3. Particle size distribution of filler, coarse and fine aggregates.
The rate of capillary absorption (sorptivity) besides the water penetration depth was used to investigate the permeability of tested SCC mixes. Sorptivity test was conducted on Ø100 50 m m specimens according to ASTM C 1585 [32]. According to DIN 1048 part 5 [33], the penetration depth for 150 150 150 mm cubic specimens exposed from below to a water pressure of 0.5 N/mm2 for 3 days was measured. Prepared 70 70 70 mm specimens were tested to determine the abrasion resistance according
The test results performed on fresh concrete are listed in Table 4. The control mix A-0% fulfil the EFNARC requirements for SCC. The mixes with higher w/b ratio B-0% and C-0% have as expected rheological properties out of the range of SCC as shown in Fig. 4 and Table 4. Also, little bleeding and segregation were observed for these mixes. NS as all fine materials decreases the flowability of mixes [14,38]. Addition of 0.75% NS decreased the slump flow of SCC with w/b = 0.41, w/b = 0.45 and w/b = 0.5 by 15.2%, 15.5% and 14.1 respectively. The mix A-0.75% with a high dosage of NS could not be considered as SCC as shown in Table 4. The NS with its large surface area can compensate the decrease of viscosity, bleeding and segregation in mixes with high w/b such as B and C mixes and returns them to the range of SCC. According to EFNARC [17] if a mix cannot be considered as SCC because it has too high viscosity it is suggested to increase water content in the mix or increase the dosage of superplasticiser or increase the paste volume. The decrease in SCC workability due to replacement by NS was also reported by previous studies [39,40]. The first approach for solving the workability problem is to increase w/b. Quercia et al. [41] found that for one SCC mix with a NS type of higher specific surface area than other types used in that study, more water was needed to have workability in the specific range and W/C ratio was increased from 0.45 to 0.5. Zaki et al. [14] found that concrete containing NS requires an additional amount of water or superplasticiser to maintain the same workability level. Others [5,42–44] studied the viscosity of cement pastes and mortars containing NS and it was found that they needed more water in order to maintain the workability of mixtures constant. However, NS dosage has to be optimized with w/b to produce
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N. Hani et al. / Construction and Building Materials 165 (2018) 504–513 Table 3 Mix designs of SCC mixtures. kg/m3
Series
Concrete ID
W/b
NS (%)
Cement
Fine aggregate
Coarse aggregate
Limestone
NS
Water
Sp
A
A-0% A-0.25% A-0.5% A-0.75% B-0% B-0.25% B-0.5% B-0.75% C-0% C-0.25% C-0.5% C-0.75%
0.41
0 0.25 0.5 0.75 0 0.25 0.5 0.75 0 0.25 0.5 0.75
350 349.1 348.3 347.4 350 349.1 348.3 347.4 350 349.1 348.3 347.4
755 755 755 755 740 740 740 740 720 720 720 720
940 940 940 940 922 922 922 922 900 900 900 900
219 219 219 219 215 215 215 215 210 210 210 210
0 0.9 1.7 2.6 0 0.9 1.7 2.6 0 0.9 1.7 2.6
143.5 143.5 143.5 143.5 157.5 157.5 157.5 157.5 175 175 175 175
2% by weight of cement
Slump flow
J-Ring
T500 (s)
D (mm)
T500j (s)
Dj (mm)
Bj (mm)
B
C
0.45
0.5
Table 4 Fresh properties of SCC. Series
Concrete ID
V-funnel flow time (s)
V-funnel flow time (s) at 5 min
L-box H₂/H1
Visual inspection Bleeding
Segregation
1 0.92 0.87 0.88
U
U
5 8 9.5 10.6
1 1 1 0.9
U U
U U
0 +3
0.8 1
A
A-0% A-0.25% A-0.5% A-0.75%
1.6 2.8 5.5 6.3
790 775 720 670
3.1 3.3 6.3 7.6
775 765 690 660
10 10 10 11.25
6.6 10.7 12.2 16.9
8.2 15.6 17.2 28.6
0.91 0.88 0.83 0.67
B
B-0% B-0.25% B-0.5% B-0.75%
1.2 2 4 4.7
805 770 730 680
1.9 3.5 4.8 5.3
800 760 700 670
6.75 8 10 9
4.9 6.3 8.8 9.5
8 10 12 13.3
C
C-0% C-0.25% C-0.5% C-0.75% Acceptance criteria of SCC suggested by EFNARC
1 1.2 1.4 2.6
885 855 800 760
1.1 1.7 2.1 2.9
850 835 790 730
10 10 7.5 8
3.9 5 7.3 8
Min Max
2 5
650 800
0 10
6 12
Fig. 5. Limitations of w/b with different NS dosage. Fig. 4. Relation between slump flow and w/b.
SCC. In this study, more slump flow and L-box tests were conducted on various mixes to find out the limitations of w/b with different NS dosage (0%, 0.25%, 0.5%, 0.75%). For each NS dosage, the mix was made by very low water content then the water was increased gradually to find out the w/b that makes the mix fulfil SCC limits of EFNARC. Then the water content was increased again until bleeding and segregation happen and the slump flow diameter exceeds the limits of EFNARC. The test results are shown in Fig. 5. From this figure, there are 3 zones. In zone A, considering slump flow, concrete has excess water content in which bleeding
and segregation occur and NS content will not help improving the workability. In zone B, NS can improve the effect of increasing water in SCC. In zone C, NS will decrease the flowability of concrete and highly increase its viscosity in which this mix cannot be considered as SCC. The second approach is to increase superplasticiser dosage. Sobolev et al. [45] found that for each 1% of nano-silica added to a standard concrete composition, 0.21% additional superplasticiser is needed. Veerendrakumar et al. found that when NS was added to self-compacting mortar, superplasticiser required was increased as
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the NS addition rises. However, in this study the maximum dosage of superplasticiser was used for all mixes. The third approach is to increase paste volume by increasing cement or increasing the volume of fine aggregate to coarse aggregate. However, this is a new mix design, which requires a comprehensive study. 3.2. Hardened concrete: mechanical properties The average compressive strength of SCC specimens at 7, 28 days and the average splitting tensile strength at 28 days are given in Figs. 6–8. Adding NS for all mixes increased both compressive and tensile strength regardless of NS dosage and w/b. Adding NS can compensate the reduction in compressive strength caused by high w/b in series B and C mixes. The 28 days strength of B0.25% and C-0.5% are 29.2 MPa and 29.9 MPa respectively which is close to reference SCC A-0% (i.e., 29 MPa). This means that we can obtain the same strength by increasing w/b (needed in places with hot weather) and by adding NS. The influence of NS on compressive strength of weak concrete is greater than that on concrete with lower w/b as it increases compressive strength by 26.9%, 32.7% and 48.8% for w/b of 0.41, 0.45 and 0.5 respectively by 0.75% replacement of cement. The tensile to compressive strength ratio still almost the same in all mixes regardless the percentage of NS added. Therefore, it can be concluded that the NS particles have no special effect on the tensile strength that may be because of its rounded shape. The average ratio between compressive strength at 7 days to that of 28 days for mixes with 0% NS for all series is 77.5%, while that for mixes with 0.75% NS is 74%. The ratio in case of using NS is smaller because NS continuous its pozzolanic reaction as age increase. Strength improvement due to replacement by NS may be attributed to the fine particles, which filled the voids in cement paste and thus making the microstructure denser (filler effect). Also, the pozzolanic reaction of nanoparticles with free Ca(OH)2 which is formed during hydration of cement forming more C-S-H gel resulting in the improvement of mechanical properties. Others also reported enhancement of SCC due to NS addition [26,28,39]. 3.3. Hardened concrete: durability tests
Fig. 7. Compressive strengths at 28 days.
Fig. 8. Splitting tensile strengths.
0.75% NS for A-0.75%, B-0.75%, and C-0.75% samples. Du et al. [15] found that using 0.3% NS decreased water penetration depth of ordinary concrete by 56% at 28 days. Quercia et al. [25] found that the addition of 3.8% nano-silica reduced water penetration depth of SCC by about 88%.
3.3.1. Water penetration depth Fig. 9 shows water penetration depths of all SCC mixes. Adding NS for all mixes decreases the water penetration depth regardless of its dosage and w/b. The decrease for series A concretes is greater than that for series B and the decrease for series B concretes is greater than that for series C. The water penetration depth decreased by 43.5%, 37.8% and 29.5% due to replacement by
3.3.2. Abrasion resistance The mean loss in the thickness of the specimens is shown in Fig. 10. The abrasion resistance is determined as the mean loss in specimen thickness. Adding NS increases the abrasion resistance and decreases the thickness loss regardless of its dosage and w/b. The influence of a particular NS dosage on the abrasion resistance of SCC as increasing w/b is not consistent. Addition of 0.75% NS decreased abrasion resistance of SCC with w/b = 0.41, w/b = 0.45 and w//b = 0.5 by 46.2%, 38.3%, and 43.3%. The enhancement in
Fig. 6. Compressive strengths at 7 days.
Fig. 9. Water penetration depth of SCC at different w/b.
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abrasion resistance may be due to the formation of C-S-H that fills the pores, so concrete becomes denser.
3.3.3. Water sorptivity The rate of initial absorption (initial sorptivity) of all concrete mixes is shown in Figs. 11–13. The initial sorptivity is calculated as the slope of the line that is the best fit in the figures (R2 < 0.98). The rate of secondary absorption (secondary sorptivity) for all mixes could not be determined (R2 < 0.98). Fig. 14 shows summarised initial sorptivity values. The results are showing that incorporating NS in SCC decreases sorptivity values of SCC with low w/b. The decrease for series A concretes is greater than that for series B while for concretes with high w/b (series C) sorptivity showed a marginal decrease even with high NS dosage. For SCC with low w/b and high NS dosage like A-0.75% sample, the sorptivity decreased by large value reached to 48.5% due to replacement by 0.75% NS. The increase of w/b from 0.41 to 0.5 increased sorptivity by about 17.4%, which was not significantly decreased by using NS. The effect of incorporating NS on sorptivity is more significant in concrete with lower w/b than that with higher w/b. It seems because concretes with low w/b have pores that NS can fill, and the formed C-S-H gel can subdivide large pores into small pores thus the pore structure is refined or partially blocked. While concretes with high w/b have a high void content, so even if NS fills some of the voids they will still be weak and porous. This could be clear in the microstructure analysis, which is discussed later in the text. The reduced sorptivity due to incorporating NS was also reported by other findings [15,40,46].
Fig. 11. Water absorption of series A concretes (w/b = 0.41).
Fig. 12. Water absorption of series B concretes (w/b = 0.45).
3.3.4. Volume of permeable voids (VPV) and water absorption tests The total water absorption and volume of permeable voids are shown in Figs. 15 and 16. From the figures, it is clear that NS decreases the total absorption and volume of voids of SCC with low w/b (series A) while for concretes with high w/b (series B and C), the effect of NS on water absorption and volume of voids is insignificant. This may be because they contain large pores, which only subdivide into small pores by adding NS but the total pore volume is not changed [47]. For SCC with low w/b and high NS dosage like A-0.75% sample, the total absorption and volume of voids decreased again by large value reached to 16.2% and 13% respectively due to replacement by 0.75% NS. Du et al. [15] also found that by the addition of 0.3% and 0.9% nano-silica, the total absorption and water accessible porosity remained constant. Quercia et al. [25] also found that the addition of 3.8% nano-silica did not change the water permeable porosity, while the durability performances could be enhanced.
Fig. 10. Thickness loss due to abrasion for different w/b.
Fig. 13. Water absorption of series C concretes (w/b = 0.5).
Fig. 14. Sorptivity values of SCC at different w/b.
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Fig. 15. Total water absorption for different w/b.
Fig. 18. Compressive strength loss due to sulphate attack for different w/b.
sulphate hydrate, Afm) forming ettringite [48–51] which leads to expansion and deterioration of concrete. Replacement by NS improves the resistance to sulphate attack due to its pozzolanic activity reacting with Ca(OH)2 (so decreasing Ca(OH)2) forming a more C-S-H gel [6]. 3.4. Microstructural analysis
Fig. 16. Volume of permeable voids for different w/b.
3.3.5. Sulphate attack The mean loss of the compressive strength and mass of specimens after being in the sulfuric acid solution for 28 days are shown in Figs. 17and 18. It can be seen that for specimens with NS, the loss of strength and mass is lower than that without NS but with small values. Adding NS decreases the loss of strength and mass (which indicates an improvement of sulphate attack resistance) regardless of its dosage and w/b. Addition of 0.75% NS decreased the compressive strength loss of SCC with w/b = 0.41, w/b = 0.45 and w/b = 0.5 by 19.5%, 21.9% and 8.6%. The loss in mass may be misleading because it may be a loss in aggregate mass. It seems that the resistance to sulphate attack depends not only on the microstructure, the voids in the cement paste but also on the chemical composition. Ca(OH)2 reacts with sulphate ions forming gypsum, which reacts with calcium aluminates hydrates (mono-
Fig. 17. Mass loss due to sulphate attack for different w/b.
The objective of this analysis is to support findings in this research. Scanning Electron Microscopy (SEM) examinations were carried out to investigate the microstructure of A-0%, A-0.5%, A0.75%, C-0% and C-0.5% mixes. Fig. 19 shows the microstructure at interfacial transition zone and paste of mixes. For A-0% and C0% samples with no NS, It can be seen that the transition zone is very weak and porous, CH crystals and voids are noticed in the paste structure, C-S-H gel existed in isolation and also large voids are present in C-0% mix. Otherwise, the SEM of samples A-0.5% and A-0.75% showed a more dense and compact transition zone, the paste structure contains more homogeneous C-S-H gel, because of the pozzolanic reaction which turned CH into C-S-H, no pores were easily found. For C-0.5% mix, small pores were found and fewer CH crystals. 4. Conclusion This study experimentally determined durability, mechanical and rheological properties of self-compacting concrete using various NS dosages and w/b. The conclusions obtained from this study are summarised as follows: The positive effect of NS on compressive strength of SCC should not be taken as evidence of a similar effect on durability properties. The effect of NS addition on mechanical and durability properties of SCC with high w/b is different from that on SCC with low w/b. The influence of NS on compressive strength of high w/b concrete is greater than that on concrete with lower w/b. The test results proved that the influence of NS on the durability of low w/b mixes is greater than that on high w/b mixes except for abrasion resistance and sulphate attack, which showed that the effect of a certain NS dosage on SCC as increasing w/b is not consistent. NS improves mechanical properties of SCC with a significant loss in fresh properties. The addition of NS decreases the flowability, improves the consistency of SCC mixtures and makes SCC more viscous with no bleeding and segregation because of its large specific surface area.
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(1)
(a)
(2)
(3)
Weak ITZ Voids Aggregate CH Paste
(b)
CH
C-S-H
Weak ITZ C-S-H Aggregate
CH
CH
Large Void
Paste
CH CH C-S-H
Voids C-S-H
(c) Dense ITZ Homogeneous C-S-H
Paste
Aggregate
(d)
Homogeneous C-S-H
Dense ITZ
Paste
Homogeneous C-S-H
Aggregate
(e)
CH
Dense ITZ
Small pores
CH Small pores
Paste
C-S-H
Aggregate
C-S-H
CH
Fig. 19. Microstructure of SCC mixtures (a) A-0% mix, (b) C-0% mix, (c) A-0.5% mix, (d) A-0.75% mix, (e) C-0.5% mix at interfacial transition zone (series 1) and paste (series 2 and 3).
The NS dosage is critical for SCC. The high dose may decrease flowability under the SCC limits. Mechanical properties of SCC increase by increasing NS dosage, especially at later ages. For mixes with 0.75% NS, Compressive strength improved by 26.9%, 32.7% and 48.8% for w/b of 0.41, 0.45 and 0.5 respectively.
NS rounded particles have no special effect on tensile strength regardless the dosage. The durability of SCC enhanced in general by increasing NS dosage. Sorptivity, water absorption and volume of permeable voids for mixes with high w/b showed a marginal decrease even with 0.75% NS dosage.
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SEM analysis supports the findings of test results. It showed that NS significantly densified the microstructure of SCC with low w/b leading to a compact ITZ. For high w/b mixes, the NS cannot densify the microstructure the same way as low w/b mixes leading to a weak ITZ. Generally, for concrete with high w/b, NS can compensate deterioration of fresh and mechanical properties caused by high w/b but cannot compensate deterioration caused for durability. In comparison with previous works, the NS content concerning agglomeration is given which was not studied in this work. The NS content concerning agglomeration is critical, however it was not studied in this work. This is ongoing research study by the authors. Acknowledgements The authors would like to thank the technical staff of the Material Research Center (MRC) at the faculty of engineering Ain Shams University for help and hard work during the experimental phase of the research. The authors also appreciate the working team at Housing and Building National Research Center (HBRC). This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. References [1] L.C. Hollaway, Key issues in the use of fibre reinforced polymer (FRP) composites in the rehabilitation and retrofitting of concrete structures, Woodhead Publ. Ser. Civ. Struct. Eng. (2011) 3–74, https://doi.org/10.1533/ 9780857090928.1.3. [2] H. Li, H.G. Xiao, J. Yuan, J. Ou, Microstructure of cement mortar with nanoparticles, Compos. Part B: Eng. 35 (2004) 185–189, https://doi.org/10.1016/ S1359-8368(03)00052-0. [3] T. Ji, Preliminary study on the water permeability and microstructure of concrete incorporating nano-SiO2, Cem. Concr. Res. 35 (2005) 1943–1947, https://doi.org/10.1016/j.cemconres.2005.07.004. [4] H. Bahadori, P. Hosseini, Reduction of cement consumption by the aid of silica nano-particles (investigation on concrete properties), J. Civ. Eng. Manage. 18 (2012) 416–425, https://doi.org/10.3846/13923730.2012.698912. [5] Y. Qing, Z. Zenan, K. Deyu, C. Rongshen, Influence of nano-SiO2 addition on properties of hardened cement paste as compared with silica fume, Constr. Build. Mater. 21 (2007) 539–545, https://doi.org/10.1016/ j.conbuildmat.2005.09.001. [6] M. Heikal, S. Abd El Aleem, W.M. Morsid, Durability of composite cements containing granulated blast-furnace slag and silica nano-particles, Indian J. Eng. Mater. Sci. 23 (2016) 88–100. [7] M. Heikal, N.S. Ibrahim, Hydration, microstructure and phase composition of composite cements containing nano-clay, Constr. Build. Mater. 112 (2016) 19– 27, https://doi.org/10.1016/j.conbuildmat.2016.02.177. [8] M. Heikal, O.K. Al-Duaij, N.S. Ibrahim, Microstructure of composite cements containing blast-furnace slag and silica nano-particles subjected to elevated thermally treatment temperature, Constr. Build. Mater. 93 (2015) 1067–1077, https://doi.org/10.1016/j.conbuildmat.2015.05.042. [9] M. Heikal, M.N. Ismail, N.S. Ibrahim, Physico-mechanical, microstructure characteristics and fire resistance of cement pastes containing Al2O3 nanoparticles, Constr. Build. Mater. 91 (2015) 232–242, https://doi.org/10.1016/ j.conbuildmat.2015.05.036. [10] H. El-Didamony, M. Heikal, T.M. El-Sokkary, K.A. Khalil, I.A. Ahmed, Active belite b-C2S and the hydration of calcium sulfoaluminates prepared from nano-materials, Ceramics – Silikaty 58 (2014) 165–171. [11] M. Heikal, A.I. Ali, M.N. Ismail, S.A.N.S. Ibrahim, Behavior of composite cement pastes containing silica nano-particles at elevated temperature, Constr. Build. Mater. 70 (2014) 339–350, https://doi.org/10.1016/ j.conbuildmat.2014.07.078. [12] S.A. El Aleem, W.M. Morsi, M. Heikal, Hydration characteristics, thermal expansion and microstructure of cement pastes and mortars containing nanoSiO2, Constr. Build. Mater. 59 (2014) 151–160, https://doi.org/10.1016/ j.conbuildmat.2014.02.039. [13] M. Heikal, S. Abd El Aleem, W.M. Morsi, Characteristics of blended cements containing nano-silica, HBRC J. 9 (2013) 243–255, https://doi.org/10.1016/j. hbrcj.2013.09.001. [14] S.I. Zaki, Khaled S. Ragab, How nanotechnology can change concrete, in: 1st Int. Conf. Sustain. Built Environ. Infrastructures Dev. Ctries, 2009, pp. 407–414. [15] H. Du, S. Du, X. Liu, Durability performances of concrete with nano-silica, Constr. Build. Mater. 73 (2014) 705–712, https://doi.org/10.1016/ j.conbuildmat.2014.10.014. [16] H. Okamura, K. Ozawa, Self-compacting high performance concrete, Struct. Eng. Int. 6 (1996) 269–270, https://doi.org/10.2749/101686696780496292.
[17] EFNARC, in: Specification and Guidelines for Self-Compacting Concrete, Rep. from Eur. Fed. Spec. Constr. Chem. Concr. Syst., 2002, pp. 1–32. doi: 0 9539733 4 4. [18] K. Audenaert, V. Boel, G. De Schutter, Chloride migration in self compacting concrete, in: Proc. Fifth Int. Conf. Concr. under Sev. Cond. Environ. Load. (CONSEC’07), Tours, 4–6 June, 2007, pp. 291–298. [19] F.H. Wittmann, On the action of capillary pressure in fresh concrete, Cem. Concr. Res. 6 (1976) 49–56. [20] M. Al-Fadhala, K.C. Hover, Rapid evaporation from freshly cast concrete and the Gulf environment, Constr. Build. Mater. 15 (2001) 1–7, https://doi.org/ 10.1016/S0950-0618(00)00064-7. [21] I. Yakoubi, S. Aggoun, H. Ait Aider, H. Houari, The influence of bleeding, extra water and superplasticizer on the SCC plastic shrinkage cracking: case of hot weather, J. Adhes. Sci. Technol. 30 (2016), https://doi.org/10.1080/ 01694243.2016.1189869. [22] M. Heikal, M.S. Morsy, I. Aiad, Effect of treatment temperature on the early hydration characteristics of superplasticized silica fume blended cement pastes, Cem. Concr. Res. 35 (2005) 680–687, https://doi.org/10.1016/j. cemconres.2004.06.012. [23] M. Heikal, M. Morsy, Effect of Curing Temperature on the Electrical Resistivity and Rheological Properties of Superplastized Blended Cement Pastes, 2004. [24] A. Nazari, S. Riahi, The effects of SiO2 nanoparticles on physical and mechanical properties of high strength compacting concrete, Compos. Part B: Eng. 42 (2011) 570–578, https://doi.org/10.1016/j.compositesb.2010.09.025. [25] G. Quercia, P. Spiesz, G. Hüsken, H.J.H. Brouwers, SCC modification by use of amorphous nano-silica, Cem. Concr. Compos. 45 (2014) 69–81, https://doi.org/ 10.1016/j.cemconcomp.2013.09.001. [26] M. Jalal, E. Mansouri, M. Sharifipour, A.R. Pouladkhan, Mechanical, rheological, durability and microstructural properties of high performance selfcompacting concrete containing SiO2 micro and nanoparticles, Mater. Des. 34 (2012) 389–400, https://doi.org/10.1016/j.matdes.2011.08.037. [27] ASTM C 494, Standard Specification for Chemical Admixtures for Concrete, Am. Soc. Test. Mater., 2004. [28] M. Jalal, A. Pouladkhan, O.F. Harandi, D. Jafari, Comparative study on effects of Class F fly ash, nano silica and silica fume on properties of high performance self compacting concrete, Constr. Build. Mater. 94 (2015) 90–104, https://doi. org/10.1016/j.conbuildmat.2015.07.001. [29] The European Guidelines for Self Compacting Concrete, Specification, Production and Use, 2005, p. 68. [30] ASTM C 39, in: Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, Annu. B. ASTM Stand. Vol 04.02., 2003, pp. 1–5, https:// doi.org/10.1520/C0039. [31] ASTM C 496, in: Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimen, Annu. B. ASTM Stand. Vol 04.02., 2004, pp. 1–5. [32] ASTM C 1585, in: Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes, Annu. B. ASTM Stand. Vol 04.02., 2004, pp. 1–6, https://doi.org/10.1520/C1585-11.2. [33] DIN 1048 (Part-5), German Standard for Determination of Permeability of Concrete, 1991. [34] DIN 52108, Wear Test Using the Grinding Wheel According to Böhme, 2010. [35] ASTM C 642, in: Standard Test Method for Density, Absorption, and Voids in Hardened Concrete, Annu. B. ASTM Stand. Vol 04.02., 1997, pp. 1–3. [36] M. Nehdi, M.T. Bassuoni, M. Amin, Self-compacting concrete: using limestone to resist sulfuric acid, Proc. ICE – Constr. Mater. 160 (2007) 113–123, https:// doi.org/10.1680/coma.2007.160.3.113. [37] Z. Makhloufi, E.H. Kadri, M. Bouhicha, A. Benaissa, Resistance of limestone mortars with quaternary binders to sulfuric acid solution, Constr. Build. Mater. 26 (2012) 497–504, https://doi.org/10.1016/j.conbuildmat.2011. 06.050. [38] T. Bahaa, Effect of utilizing nano and micro silica on early properties of cement mortar, World Appl. Sci. J. 29 (2014) 370–382, https://doi.org/10.5829/idosi. wasj.2014.29.03.13862. [39] M.H. Beigi, J. Berenjian, O. Lotfi Omran, A. Sadeghi Nik, I.M. Nikbin, An experimental survey on combined effects of fibers and nanosilica on the mechanical, rheological, and durability properties of self-compacting concrete, Mater. Des. 50 (2013) 1019–1029, https://doi.org/10.1016/ j.matdes.2013.03.046. [40] S.W.M. Supit, F.U.A. Shaikh, Durability properties of high volume fly ash concrete containing nano-silica, Mater. Struct. (2014) 2431–2445, https://doi. org/10.1617/s11527-014-0329-0. [41] P. Spiesz, H.J.H. Brouwers, in: Effects of Nano-silica (NS) Additions on Durability of SCC Mixture, 2015, pp. 169–178, https://doi.org/10.1007/9783-319-09921-7. [42] L. Senff, J.A. Labrincha, V.M. Ferreira, D. Hotza, W.L. Repette, Effect of nanosilica on rheology and fresh properties of cement pastes and mortars, Constr. Build. Mater. 23 (2009) 2487–2491, https://doi.org/10.1016/ j.conbuildmat.2009.02.005. [43] K.L. Lin, W.C. Chang, D.F. Lin, H.L. Luo, M.C. Tsai, Effects of nano-SiO2 and different ash particle sizes on sludge ash-cement mortar, J. Environ. Manage. 88 (2008) 708–714, https://doi.org/10.1016/j.jenvman.2007.03.036. [44] J. Björnström, A. Martinelli, A. Matic, L. Börjesson, I. Panas, Accelerating effects of colloidal nano-silica for beneficial calcium-silicate-hydrate formation in cement, Chem. Phys. Lett. 392 (2004) 242–248, https://doi.org/10.1016/j. cplett.2004.05.071. [45] K. Sobolev, I. Flores, R. Hermosillo, L.M. Torres-Martínez, Nanomaterials and Nanotechnology for High-Performance Cement Composites, 2008.
N. Hani et al. / Construction and Building Materials 165 (2018) 504–513 [46] A. Najigivi, S. Abdul Rashid, F. Nora, A. Aziz, M.A. Mohd Salleh, Water absorption control of ternary blended concrete with nano-SiO2 in presence of rice husk ash, Mater. Struct. 45 (2012) 1007–1017, https://doi.org/10.1617/ s11527-011-9813-y. [47] V. Yogendran, B. Langan, Utilization of silica fume in high strength concrete, Util. High Strength Concr. Stavanger, Tapir Publ., Trondheim, 1987. [48] M. Abd, S. Abd, M. Heikal, H. El Didamony, Hydration and durability of sulphate-resisting and slag cement blends in Caron’s Lake water, Cem. Concr. Res. 35 (2005) 1592–1600, https://doi.org/10.1016/j.cemconres.2004.06.038. [49] H. El-Didamony, M. Heikal, S. Al-Masry, Effect of delaying addition time of SMF superplasticizer on hydration characteristics of blended cement pastes, Constr.
513
Build. Mater. 35 (2012) 261–269, https://doi.org/10.1016/ j.conbuildmat.2012.02.068. [50] I. Aiad, H. El-Didamony, M. Heikal, S. Al-Masry, Effect of delayed addition time of synthesized SSPF condensate on the durability of sulphate resisting cement pastes incorporating micro-silica, Constr. Build. Mater. 48 (2013) 1092–1103, https://doi.org/10.1016/j.conbuildmat.2013.07.067. [51] H.N. Atahan, D. Dikme, Use of mineral admixtures for enhanced resistance against sulfate attack, Constr. Build. Mater. 25 (2011) 3450–3457, https://doi. org/10.1016/j.conbuildmat.2011.03.036.