Effect of silica fume particle size on mechanical properties of short carbon fiber reinforced concrete

The addition of short carbon fibers (CF) in concrete leads to changes of both the mechanical and electrical properties of the hardened product. The addition of silica fume (SF) to concrete mixtures with CF facilitates an even distribution of fibers within the mixture volume and improves the strength and multifunctional properties of the product. In this work the influence of the particle size distribution of commercial SF on the strength properties of CF reinforced concrete has been studied. Also the influence of the addition of methyl-cellulose as a fiber dispersing agent that improves the homogeneity of the mixture has been studied. The results show a different behavior of concrete depending of the average SF particle size (between 1 μm and 60 μm). The evolution of the elastic compressive modulus of carbon fiber reinforced concrete (CFRC) is linked to the one of the compressive strength, with a good coincidence with the CEB (Comité Euro-International du Béton) formula values. This parameter is only slightly decreased by the addition of methyl-cellulose.