Bond properties of polymer-modified lightweight self-consolidating concrete containing expanded polystyrene

Abstract

Limited studies addressed the effect of styrene-butadiene rubber (SBR) latexes on bond properties of lightweight self-consolidating concrete (LWSCC) containing expanded polystyrene (EPS). Different concrete series containing up to 20 % EPS are tested in this program; the resulting density ranged from 1,870 to 2,350 kg/m3. The SBR was incorporated at various rates, whereas the water-to-binder ratio (w/b) was adjusted depending on EPS additions to maintain a fixed compressive strength of 42 ±4 MPa. The high-range water reducer and viscositymodifier were regulated to secure the desired LWSCC workability and stability requirements. Test results showed that the incorporation of EPS decreases the pull-off bond strength to existing substrates as well as the ultimate bond strength to embedded steel bars, given the weaker concrete skeleton and stiffness that favor microcrack propagation during tensile loading. The reduction in w/b was efficient to strengthen the matrix and improve the pull-off bond, particularly for mixtures incorporating SBR additions. The improved ultimate bond strength that was due to decreased w/b was attributed to less bleed water and fewer shrinkage cracks at the vicinity of the reinforcing bars as well as higher concrete crushing strength between the steel ribs. A series of regression statistical models are developed to simplify predicting mechanical and bond properties of SBR-modified EPS-based LWSCC mixtures.