An experimental and mesoseopic lattice simulation study of styrene-butadiene latex-cement composites properties

The consequences of styrene-butadiene rubber (SBR) latex addition on the hardness and structural properties of a cement matrix have been investigated. The results show that the primary effect of latex addition is the decrease in the so-called capillary porosity and a shift of the pore-size distribution towards the nanometer range. In spite of this, addition of latex significantly alters the hardness of the polymer-cement compound as compared to pure cement, due to the intrinsically smaller modulus of the polymer and the lack of strong interaction with cement phases. It is shown that the properties depend both on the Polymer/Cement (P/C) and Water/Cement (W/C) ratios. This study confirms that the butadiene-styrene copolymer is confined to the capillary porosity only and interacts but weakly with the different cement phases. In agreement with this, a simple mesoscopic lattice model, much inspired from Powers pioneering model for cement hydration, was shown to account for the porosity and composition dependence of hardness and modulus. A criterion for the activity of fillers is proposed. (c) 2004 RILEM. All rights reserved.