Mixture optimisation of polymer-modified lightweight SCC

The use of styrene-butadiene rubber (SBR) polymeric latexes is common in cementitious materials intended for repair and precast works to improve bond to existing substrates and durability of structures. Limited information exists regarding the feasibility of structural grade lightweight self-consolidating concrete (LWSCC) containing such additions, including the altered stability and bond properties. Four series of LWSCC mixtures prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project; the free water was adjusted to secure compressive strength of 40 +/- 3.5 MPa. The resulting unit weight varied from 1790 to 2280 kg/m(3). Test results have shown that SBR additions reduced concrete flowability and passing ability; however, they led to improved static stability, for example in terms of bleeding, segregation and floating of LWA. Special emphasis was placed on highlighting the altered stability responses with respect to the European guidelines for SCC. Remarkable improvement in splitting tensile strength and bond to existing concrete substrates was noticed with SBR additions. A.-factor was developed to predict the combined effect of free water, viscosity modifier, LWA and SBR on the stability and hardened properties of polymer-modified LWSCC.