Title: Self-Leveling Geopolymer Concrete Using Alkali-Activated Fly Ash
Author(s): Anvit Gadkar and Kolluru V. L. Subramaniam
Publication: Materials Journal
Appears on pages(s): 21-30
Keywords: alkali-activated fly ash; particle packing; rheology; viscosity; yield stress
Self-leveling concrete is developed with low-calcium alkali-activated fly ash (AAF) binder paste. The rheological behavior of AAF pastes with different compositions is evaluated. AAF pastes are proportioned with alkali-silicate activating solutions to ensure specific reactive oxide ratios for comparable geopolymer strength. The yield stress and the viscosity of the AAF binder paste vary with the silica content and the silica modulus (SiO2/Na2O mass ratio) in the alkali-silicate activating solution. The slump and flow behaviors of concrete mixtures made with AAF paste are evaluated. The requirements of the AAF binder characteristics, paste content, and aggregate packing for achieving self-leveling flow characteristics under gravity-induced flow are assessed. The transition from a frictional to a flow-type behavior in concrete mixtures depends on the AAF binder paste content. Self-leveling is achieved without the use of admixtures with an AAF binder paste of low yield stress and at a paste content of 45%. Improving the aggregate packing using the Fuller-Thompson curve and reducing the yield stress of the AAF
binder paste increase the flow achieved in concrete mixtures. The specifications for cement-based self-consolidating concrete (SCC) are closely applicable for self-leveling AAF-based concrete.