Silica fume

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

Microstructural and Mechanical Effects of Latex, Methylcellulose, and Silica Fume on Carbon Fiber Reinforced Cement

Abstract: The effect of methylcellulose, silica fume, and latex on the degree of dispersion of short carbon fibers in cement paste was assessed. This degree, as indicated by the ratio of the measured volume of electrical conductivity to the calculated value, and the effectiveness of the fibers in enhancing the tensile/flexural properties attained by using methylcellulose and silica fume were higher than those attained by using methylcellulose alone or latex. Methylcellulose was superior to latex in giving a high degree of fiber dispersion at fiber volume fractions < 1 percent, as measured by this technique. Latex resulted in superior tensile-flexural properties and lower content and size of air voids than methylcellulose. With the fiber content fixed at 0.53 vol. percent, the degree of fiber dispersion, as measured by this technique, decreased with increasing latex-cement ratio. As a result the flexural toughness decreased monotonically with increasing latex-cement ratio and the flexural strength attained a maximum at an intermediate latex-cement ratio of 0.15. In contrast, both flexural toughness and strength increased monotonically with increasing latex-cement ratio when fibers were absent.

Rheology of Cement Paste: Role of Excess Water to Solid Surface Area Ratio

Abstract: Although many attempts have been made in previous research to identify the various parameters governing the rheology of cement paste, there has been little progress in evaluating the combined effects of these parameters. In this paper, a new parameter, the excess water to solid surface area ratio, is proposed to evaluate the combined effects of water content, packing density, and solid surface area on the rheological properties of cement paste. For the purpose of determining the value of this new parameter, a new wet packing method has been developed to measure the packing density of cementitious materials so that the voids content of the cementitious materials and the amount of excess water in the cement paste can be quantified. A number of cement paste samples containing different proportions of cement, pulverized fuel ash and condensed silica fume, and different water contents have been tested and their rheological properties, as measured by a rheometer, correlated to the new parameter. The correlation revealed that the excess water to solid surface area ratio, which serves as an indicative measure of the average water film thickness, is the single most important factor governing the rheology of cement paste.

Determination of particle size, surface area, and shape of supplementary cementitious materials by different techniques

Abstract: The particle size distribution, surface area and shape are fundamental characteristics of supplementary cementitious materials (SCMs). Accurate measurement of these properties is required in computational efforts to model the hydration process, and the characterization of these parameters is also an important practical issue during the production and use of blended cements. Since there are no standard procedures specifically for the determination of physical properties of SCMs, the techniques that are currently used for characterizing Portland cement are applied to SCMs. Based on the fact that most of the techniques have been developed to measure cements, limitations occur when these methods are used for other materials than cement, particularly when these have lower fineness and different particle shape and mineralogical composition. Here, samples of fly ash, granulated blast furnace slag and silica fume were tested. Different results obtained using several methods for the determination of specific surface area are presented. Recommendations for testing SCMs using air permeability, sieving, laser diffraction, BET, image analysis and MIP are provided, which represent an output from the work of the RILEM Technical Committee on Hydration and Microstructure of Concrete with Supplementary Cementitious Materials (TC-238-SCM).