Silica fume

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

Shrinkage cracking of high-strength concrete

Abstract: Pozzolanic materials and high-range water-reducing admixtures have improved the strength and durability of concrete construction. Since compressive strength is the most commonly used parameter to describe the quality of concrete, high-strength or high-performance concrete, has been used in many structures that are sensitive to shrinkage cracking. No systematic study has been conducted to evaluate the restrained shrinkage cracking behavior of high-strength concrete. This paper presents research on the restrained shrinkage cracking on several strength levels of concrete. Higher strength levels were derived by partial substitution of cement with silica fume and by reducing the water content. Ring-type specimens were used for restrained shrinkage cracking tests. Free shrinkage, creep, weight loss, compressive, and splitting tensile strength were also examined. Findings reveal that the free shrinkage for different concretes does not depend on the unit water content or weight loss and that high-strength silica fume concrete shows higher shrinkage and lower creep. Cracking for high-strength silica fume concrete develops much faster and is significantly wider than that of normal-strength concrete.

Elastic properties of high alumina cement castables from room temperature to 1600°C

Abstract: High-alumina refractory castables with compositions in the systems CaO–Al2O3 and CaO–Al2O3–SiO2 were studied using an ultrasonic technique. The technique allows in-situ, non-destructive measurement of Young's modulus from room temperature to 1600°C. Elastic and dilatometric properties were investigated in relation to phase changes (followed by XRD) and sintering phenomena. The conversion of CAH10, the hydration of still-anhydrous cement phases, and the dehydration of C3AH6 and AH3 are related with events in Young's modulus evolution. Addition of 1 wt% of silica fume strongly decreases the high-temperature mechanical properties.

Effect of supplementary cementing materials on the specific conductivity of pore solution and its implications on the rapid chloride permeability test (AASHTO T277 and ASTM C1202) results

Abstract: The American Association of States Highway and Transportation Officials (AASHTO) Test Method T277--Rapid Determination of the Chloride Permeability of Concrete and the American Society of Testing and Materials (ASTM) C1202--Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration have specified a rapid test method to rank the chloride penetration resistance of various concretes by applying a potential of 60 V DC to a concrete specimen and measuring the charge passed through the specimen during 6 hours of testing. The method is essentially a measurement of electrical conductivity of concrete, which depends on both the pore structure and the chemistry of the pore solution. Analyses based on published results have indicated that the replacement of portland cement with supplementary cementing materials, such as silica fume, can reduce the electrical conductivity of concrete more than 90% because of the change in pore solution composition in the concrete. Chemical composition of pore solution has little to do with the transport of chloride ions in the concrete; thus, it is not correct to use passed charge to rank the chloride penetration resistance of concrete made with supplementary cementing materials.