Silica fume

About: Silica fume is a research topic. Over the lifetime, 10177 publications have been published within this topic receiving 173857 citations.

Compressive strength, microstructure and thermal analysis of autoclaved and air cured structural lightweight concrete made with coal bottom ash and silica fume

Abstract: This research investigated the compressive strength, microstructure and thermal analysis of autoclaved and air cured structural lightweight concrete made with coal bottom ash and silica fume. The results show that bottom ash lightweight concrete autoclaved for 6 h gives compressive strength similar to the bottom ash lightweight concrete air cured for 28 days and found that the compressive strength of both bottom ash lightweight concrete increased when silica fume was added to the mix. The highest compressive strength obtained for all mixes was found when coal bottom ash was used at 20% with the addition of silica fume at 5% and that this strength value is significantly higher than that of Portland cement control. The thermal conductivity of all bottom ash lightweight concrete at 28 days and those autoclaved for 6 h were found to be slightly higher than that of Portland cement control concrete. Air cued hydration products such as ettringite, calcium silicate hydrate and gehlenite hydrate were detected using thermogravimetric analysis. The tobermorite phase detected in autoclaved bottom ash concrete with silica fume was found to give denser microstructure than the fibrous-like C–S–H phases detected in Portland cement control concrete.

Performance of self-compacting concrete containing different mineral admixtures

Abstract: Self-Compacting Concrete is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction, even in the presence of congested reinforcement. One of the disadvantages of self-compacting concrete is its cost, associated with the use of high volumes of Portland cement and use of chemical admixtures. One alternative to reduce the cost of self-compacting concrete is the use of mineral admixtures such as silica fume, ground granulated blast furnace slag and fly ash, which is finely, divided materials added to concrete during mixture procedure. When these mineral admixtures replace a part of the Portland cement, the cost of self-compacting concrete will be reduced especially if the mineral admixtures are waste or industrial by-product. Moreover, the use of mineral admixtures in the production of self-compacting concrete not only provides economical benefits but also reduces heat of hydration. The incorporation of mineral admixtures also eliminates the need for viscosity-enhancing chemical admixtures. The lower water content of the concrete leads to higher durability, in addition to better mechanical integrity of the structure. This paper presents an experimental investigation on strength aspects like compressive, flexural and split tensile strength of self compacting concrete containing different mineral admixtures and workability tests for different mineral admixtures (slump, L-box, U-box and T50) are carried out. The methodology adopted is that mineral admixtures are replaced by 30%, 40% and 50% for Portland cement and performance is measured and compared. The influence of mineral admixtures on the workability, compressive strength, splitting tensile strength and flexural strength of self-compacting concrete was investigated. The mix proportion is obtained as per the guidelines given by European Federation of producers and contractors of special products for structure. The following inferences were made; optimum dosage of super plasticizer enhanced the flow property of the concrete. As a result, overall improvements in the flow and filling ability of the self-compacting concrete were observed. It is observed that when mineral admixtures used in self-compacting concrete, can reduce the amount of super-plasticizer necessary to achieve a given fluidity. It should be noted that the effect of mineral admixtures on admixture requirements is significantly dependent on their particle size distribution as well as particle shape and surface characteristics. From this view point, a cost effective self-compacting concrete design can be obtained by incorporating reasonable amounts of silica fume, fly ash, and ground granulated blast furnace slag.

Comparison of ground waste glass with other supplementary cementitious materials

Abstract: Finely ground glass has pozzolanic properties that make attractive its recycling as supplementary cementitious material. This paper compares the behaviour of waste glass powders of different fineness with that of natural pozzolana, coal fly ash and silica fume. Chemical analysis, compressive strength measurements and durability tests were carried out to investigate the effect of ground glass on strength and durability performances of mortars. Blended both with Portland cement and lime, ground glass improved strength, resistance to chloride penetration and resistance to sulphate attack of mortars more than natural pozzolana and similarly to fly ash. Mortars with ground glass immersed in water for seven years did not show any sign of degradation and increased their compressive strength. The ranking of ground glass with respect to the other mineral additions was not affected by fineness.