Characterization of alkali activated slag–fly ash blends containing nano-silica
TL;DR: In this paper, the effects of nano-silica incorporation on an eco-friendly alkali activated slag-fly ash blends were investigated, and the results indicated that as the nano silica content increases, the slump flow is significantly reduced, and reaction process is slightly retarded according to the setting time and isothermal calorimetry results.
About: This article is published in Construction and Building Materials.The article was published on 2015-11-15. It has received 151 citations till now. The article focuses on the topics: Compressive strength & Fly ash.
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TL;DR: In this paper, a summary of developments in partially replaced cement composite and geopolymers by industrial by-products along with different nano-materials is presented along with the health related issues on using nano materials and methods can be used to overcome the risks of exposure.
188 citations
Cites background from "Characterization of alkali activate..."
...The authors [84] reported that flowability was reduced with the addition of NS and exhibited a major influence at even little amounts....
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...From another study, it was found that NS incorporation up to 2% showed a positive effect on compressive strength at various curing periods of 3, 7 and 28 days, but further addition confirmed negative effects [84]....
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TL;DR: In this article, the effects of nano-silica on flowability, strength development, sorptivity and acid resistance properties of fly ash geopolymer mortars cured at 20°C were investigated.
Abstract: This study investigated the effects of nano-silica on flowability, strength development, sorptivity and acid resistance properties of fly ash geopolymer mortars cured at 20 °C. The changes in mass, compressive strength and microstructure of the specimens after immersion in acid solutions for different durations were determined. The microstructures were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. It was found that addition of nano-silica in geopolymer mortars based on fly ash alone or fly ash blended with 15% GGBFS or 10% OPC improved the compactness of microstructure by reducing porosity. Thus, the nano-silica reduced sorptivity and increased compressive strength of the mixes. The average mass loss after 90 days of immersion in acid solutions reduced from 6.0% to 1.9% by addition of 2% nano-silica. Similarly, significant reduction in strength loss after immersion in acid solution was observed in the specimens by using nano-silica.
149 citations
Cites background from "Characterization of alkali activate..."
...[17] 51 showed that nano-silica increased the strength of alkali activated slags....
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...[17] noted that lower slag content provided a better 149 flowability due to their morphological differences....
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TL;DR: In this paper, the effects of steel fiber and silica fume on the mechanical and fracture properties of ultra-high performance geopolymer concrete (UHPGC) were investigated.
Abstract: This study investigates the effects of steel fiber and silica fume on the mechanical and fracture properties of ultra-high performance geopolymer concrete (UHPGC). Four volume fractions of steel fiber (0%, 1%, 2% and 3%) and four contents of silica fume by the mass of total binders (5%, 10%, 20% and 30%) were used. The mechanical and fracture properties evaluated include the compressive, splitting tensile and ultimate flexural strengths, modulus of elasticity, flexural behavior, fracture energy and stress intensity factor. In addition, the correlations among the compressive and splitting tensile strengths, and compressive strength and elastic modulus were studied. The results indicated the increase of steel fiber dosage resulted in the decrease of the workability, but the continuous improvement of mechanical and fracture performance of UHPGC. The empirical equations for predicting elastic modulus of conventional ultra-high performance concrete overestimated the elastic modulus of UHPGC, however some prediction formulas for the splitting tensile strength of PC-based concretes could be applied for UHPGC. Silica fume had a complicated influence on workability and hardened properties of UHPGC, which is strongly dependent on its amount. The inclusion of 10% silica fume induced the increase of the flowability, but the sharp degradation of the mechanical performance, while the specimens with 20% and 30% silica fume possessed the superior mechanical characteristic to that with 5% silica fume. The steel fiber dosage could be decreased without sacrificing the mechanical and fracture performance of UHPGC, via the increase of silica fume content.
141 citations
TL;DR: In this paper, a fly ash based geopolymer concrete was developed using 6% nano silica replacing fly ash, which showed an appreciable improvement in structural behaviour at different ages without any heat activation.
138 citations
TL;DR: In this paper, the effect of various mineral additives on the mechanical, durability and microstructure properties of concrete and geopolymer mixtures was summarized and the results advocate that mixtures with desired properties can be designed for ambient temperature curing condition with minerals additives which may further promote them as an environmentally friendly construction material.
125 citations
References
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TL;DR: Aluminosilicate-based alkaline cements have been classified into five categories as discussed by the authors, and the key advances made in the understanding of synthetic gels are discussed, which ultimately finds hybrid cements to be technologically viable materials for contemporary construction.
1,104 citations
"Characterization of alkali activate..." refers background in this paper
...This type of material generally exhibits superior mechanical properties [1], durability [2,3], thermal resistance [4] together with significantly reduced energy costs and carbon emissions [5,6]....
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TL;DR: In this paper, the influence of nano-SiO 2 (NS) addition on properties of hardened cement paste (hcp) as compared with silica fume (SF) has been studied through measurement of compressive and bond strengths of hcp, and by XRD and SEM analysis.
1,039 citations
"Characterization of alkali activate..." refers background in this paper
...Compared to the effect of nano-silica on strength in cement based system, the nano-silica exhibits a less significant influence in alkali activated systems [47,64,65]....
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TL;DR: In this paper, the mid-, near-, and far-infrared (IR) spectra of synthetic, single-phase calcium silicate hydrates (C-S-H) with Ca/Si ratios (C/S) of 0.41-1.2 were analyzed.
Abstract: The mid-, near-, and far-infrared (IR) spectra of synthetic, single-phase calcium silicate hydrates (C-S-H) with Ca/Si ratios (C/S) of 0.41–1.85, 1.4 nm tobermorite, 1.1 nm tobermorite, and jennite confirm the similarity of the structure of these phases and provide important new insight into their H2O and OH environments. The main mid-IR bands occur at 950–1100, 810–830, 660–670, and 440–450 cm−1, consistent with single silicate chain structures. For the C-S-H samples, the mid-IR bands change systematically with increasing C/S ratio, consistent with decreasing silicate polymerization and with an increasing content of jennite-like structural environments of C/S ratios >1.2. The 950–1100 cm−1 group of bands due to Si-O stretching shifts first to lower wave number due to decreasing polymerization and then to higher wave numbers, possibly reflecting an increase in jennite-like structural environments. Because IR spectroscopy is a local structural probe, the spatial distribution of the jennite-like domains cannot be determined from these data. A shoulder at ∼1200 cm−1 due to Si-O stretching vibrations in Q3 sites occurs only at C/S lessthan equal to 0.7. The 660–670 cm−1 band due to Si-O-Si bending broadens and decreases in intensity for samples with C/S > 0.88, consistent with depolymerization and decreased structural order. In the near-IR region, the combination band at 4567 cm−1 due to Si-OH stretching plus O-H stretching decreases in intensity and is absent at C/S greater than ∼1.2, indicating the absence of Si-OH linkages at C/S ratios greater than this. The primary Si-OH band at 3740 cm-1 decreases in a similar way. In the far-IR region, C-S-H samples with C/S ratio greater than ∼1.3 have increased absorption intensity at ∼300 cm−1, indicating the presence of CaOH environments, even though portlandite cannot be detected by X-ray diffraction for C/S ratios <1.5. These results, in combination with our previous NMR and Raman spectroscopic studies of the same samples, provide the basis for a more complete structural model for this type of C-S-H, which is described.
1,034 citations
TL;DR: In this paper, the effects of ground granulated blast furnace slag (GGBFS) on the microstructure and mechanical properties of metakaolin (MK) based geopolymers were studied.
922 citations
TL;DR: In this paper, the properties of cement mortars with nano-SiO 2 were experimentally studied, and the results showed that the compressive strength of mortars containing nano SiO 2 particles was significantly higher than those of those containing silica fume at 7 and 28 days.
867 citations