Topic
Silica fume
About: Silica fume is a research topic. Over the lifetime, 10177 publications have been published within this topic receiving 173857 citations.
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TL;DR: In this article, the effect of different levels of cement replacement by silica fume (SF) or rice husk ash (RHA) on the expansion of mortar bars containing two types of reactive aggregates was investigated.
Abstract: The alkali-silica reaction (ASR), which occurs between the alkaline hydroxides in cement paste and reactive minerals in the aggregate, produces an expansive gel that may cause cracking and displacement in concrete structures. Currently, pozzolanic materials are used to prevent or minimize this cracking. An experimental program was undertaken to study the effect of different levels of cement replacement by silica fume (SF) or rice husk ash (RHA) on the expansion of mortar bars containing two types of reactive aggregates. The morphology and composition of the ASR gel were determined using scanning electron microscopy and energy-dispersive x-ray. The results indicate that it is possible to significantly reduce the mortar bar expansion for both types of aggregate using either SF or RHA. As predicted by double-layer models, the expansion of the mortar bars was highly correlated to the gel composition. The experimental results were also analyzed using the Kruskal-Wallis nonparametric method to validate the effect of these pozzolanic replacements on ASR gel composition.
79 citations
TL;DR: The Marsh cone test is a simple approach for obtaining a practical measure of the fluidity of cement pastes containing superplasticizer and silica fume as discussed by the authors, which can be used for the selection of super-plasticizers type and dosage.
Abstract: The Marsh cone test is a simple approach for obtaining a practical measure of the fluidity of cement pastes containing superplasticizer and silica fume. Using this method, a study of the effect of water/cement ratio, type and dosage of mineral admixture, and superplasticizer type on cement pastes with different superplasticizer dosages is presented here. Results are presented for cement pastes with silica fume and micronized diatomites as mineral admixtures. In all cases, there is a superplasticizer saturation dosage beyond which there is no significant increase in fluidity and, therefore, can be used for the selection of superplasticizer type and dosage. The data obtained indicate that the relative fluidity generally decreases with an increase in the silica fume content. The Marsh cone approach is also used to compare the effects of the mixing sequence used in the preparation of the pastes. A study of the loss of fluidity over time as a function of the superplasticizer type shows that the trends can vary considerably from one product to another.
79 citations
TL;DR: In this paper, the effect of lime and silica fume on the properties of geopolymer concrete cured at ambient conditions was investigated and the results showed that the slump and setting times of the concrete increases with increasing silica content and reduces with increasing lime content.
Abstract: The need to cure fly ash-based geopolymer at elevated temperatures has limited the practicability and sustainability of the composite. Hence, there is an imminent need to find ways at which fly ash-based geopolymers can be cured at ambient conditions. This paper presents the results from the experimental investigation of the effect of lime and silica fume on the properties of geopolymer concrete cured at ambient conditions. Lime and silica fume were used as the partial replacement of fly ash as an aluminosilicate precursor and the corresponding effects on the fresh, strength and microstructure of the geopolymer concrete were investigated. The findings from this study showed that the slump and setting times of the geopolymer concrete increases with increasing silica fume content and reduces with increasing lime content. Also, the use of lime and silica fume as 7.5% and 2% respectively, replacement of fly ash yielded the highest compressive strength. Microstructural investigation showed that the combined use of lime as silica fume in GPC resulted in a densified microstructure.
79 citations
TL;DR: In this article, the effects of silica fume and fly ash on the hydration process and microstructure of ultra-high performance cementitious composite (UHPCC) were investigated via different characterization methods.
79 citations
TL;DR: In this article, the effects of air-entraining agent (AEA) and silica fume on the air-void characteristics of wet-mix shotcrete (WMS) before and after shot-cleaning process were evaluated.
Abstract: It is well known that the air-void structure of hardened concrete has substantial effects on the mechanical properties and durability of concrete. In this study, laboratory evaluations were conducted to quantify the effects of air-entraining agent (AEA) and silica fume on the air-void characteristics of wet-mix shotcrete (WMS) before and after shotcreting process. For this purpose, a high-resolution image analyzer capturing elaborate graphical layouts of air-void structure using the linear transverse method was employed. Also, this study examined the effects of air-void characteristics, such as air content and spacing factor, on the strength and permeability of WMS. Based on the findings of this study, it can be concluded that: (1) shotcreting process considerably reduces overall air contents in WMS; (2) incorporating AEA with a 4.5% silica fume replacement ensures both satisfactory spacing factor and good retention of small entrained air bubbles even after shotcreting, which may improve the freeze-thaw and scaling resistance; (3) the compressive and flexural strengths of WMS were reduced as the air content increased and average spacing factor decreased; and (4) the air content affected the permeability of WMS, but no consistent correlation was found between spacing factor and permeability.
79 citations