Silica fume

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

Evaluation of rapid chloride permeability test (rcpt) results for concrete containing mineral admixtures

Abstract: The correlation between the charge passed data derived from rapid chloride permeability test (RCPT) and the chloride penetration coefficient K derived through 90-day soaking test for the concrete containing mineral admixture is elucidated. For this purpose, concrete specimens containing varying proportions and fineness of mineral admixtures, such as ground granulated blast-furnace slag (GGBFS) and silica fume (SF), and moist-cured for different periods, were subjected to a 90-day soaking test and a RCPT. To supplement the results, the electrical resistivity and compressive strengths of concrete mixtures were also evaluated. For the majority of mixtures containing SF and GGBFS, the chloride penetration coefficient K and the charge passed data were following different trends. This suggests that the charge passed and K are the independent properties of concrete controlled by different factors. The charge passed depends on the microstructure and the pore fluid conductivity (especially OH-negative ions) of the concrete, while K depends primarily on the microstructure of the concrete. Furthermore, the charge passed through SF and GGBFS concrete was shown decreasing exponentially with increasing electrical resistivity of the mixture. Thus, the charge passed through the concrete mixture containing SF and GGBFS can be used as a measure of the overall conductivity of concrete, rather than as a measure of the resistance of chloride penetration. The charge passed was shown to be related to the compressive strength of SF and GGBFS concrete; the compressive strength increases linearly with the charge passed decreasing.

Strength development and chloride penetration in rubberized concretes with and without silica fume

Abstract: The study presented herein has been carried out in order to investigate the strength development and chloride permeability characteristics of plain and rubberized concretes with and without silica fume. For this purpose, two types of tire rubber, namely crumb rubber and tire chips, were used as fine and coarse aggregate, respectively, in the production of rubberized concrete mixtures which were obtained by partially replacing the aggregate with rubber. Two water-cementitious material (w/cm) ratios (0.60 and 0.40), three moist curing periods (3, 7, and 28 days), four designated rubber contents (0, 5, 15, and 25 by total aggregate volume), two silica fume content (0 and 10% by weight of cement), and five different testing ages (3, 7, 28, 56, and 90 days) were considered as experimental parameters. The results indicated that for a given w/cm ratio and moist curing period, the use of rubber significantly aggravated the chloride ion penetration through concrete but the degree of the rate of the increment of the chloride permeability depended on the amount of the rubber used. When the curing period was extended from 3 to 28 days, the reduction in the magnitude of chloride penetration depth was notably higher for the rubberized concretes, even at a rubber content of as high as 25%. It was also observed that silica fume may be considered as a remedy to enhance the chloride penetration resistance of the rubberized concretes.