The American Concrete Institute (ACI) has released a paper called Stability and Bond Properties of Latex-Modified Semi-Lightweight Flowable Concrete.
The study set out to understand the effect of styrene-butadiene rubber (SBR) latexes on stability of semi-lightweight self-consolidating concrete and bond to embedded steel bars.
Five mixtures prepared with various lightweight aggregate (LWA) and SBR concentrations were considered for the project. The free water content was adjusted to secure compressive strength of 40 ± 3.5 MPa (5.8 ± 0.5 ksi).
ACI says: “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 and the initial stiffness of load versus the slip curves increased with SBR additions.
According to ACI: “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 were developed to predict the combined effect of free water, viscosity modifier, LWA and SBR stability and bond properties.
