Stability and bond properties of latex-modified semi-lightweight flowable concrete

Abstract

The effect of styrene-butadiene rubber (SBR) latexes on stability of semi-lightweight self-consolidating concrete and bond to embedded steel bars is not well understood. Five mixture series prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project; the free water content was adjusted to secure compressive strength of 40 ± 3.5 MPa (5.8 ± 0.5 ksi). Test results have shown that SBR additions lead to reduced concrete flow velocity and passing ability; however, improved static stability such as bleeding and segregation. The bond properties to steel bars, particularly the initial stiffness of load versus slip curves, remarkably increased with SBR additions. This was related to the coupled effect of reduced concrete bleeding that promotes creation of hydration compounds at the steel-concrete transition zone and presence of SBR polymers that help relaxing stresses during loading. A series of regression statistical models was developed to predict the combined effect of free water, viscosity modifier, LWA, and SBR on stability and bond properties.