Creep Response of Rubberized Alkali-Activated Concrete

This study examines the creep deformations and long-term strength properties of rubberized one-part alkali-activated concrete with relatively high rubber content, which have not been previously reported. The aluminosilicate precursors used in the mix design are blast furnace slag and fly ash at a ratio of 4-to-1, while anhydrous sodium metasilicate is used as the solid activator. Crumb rubber particles are used to replace 30% and 60% by volume of the total natural aggregates, and a nonrubberized one-part alkali-activated concrete mix is also prepared for comparison purposes. The creep specimens are subjected to two levels of sustained loads, representing 10% and 20% of the 28-day compressive strength. The creep loads are applied after 28 days of ambient curing, and creep deformations are monitored for a period of 1 year. The results clearly show a deterioration in mechanical properties with higher rubber content, regardless of the testing age. The compressive strength and elastic modulus of the unloaded and loaded creep specimens, tested at an age of 393 days, are generally lower than that observed for similar specimens tested at 28 days. The axial and lateral crushing strains of the specimens tested at 393 days are significantly higher than their counterparts tested at 28 days. The creep strains, measured over 365 days, increase as the applied stress level increases, but reduce with higher rubber content. The creep coefficients and specific creep values of the tested specimens over 365 days experience a reduction as the applied stress level increases, while the opposite is seen as the rubber content increases. The creep coefficients of rubberized one-part alkali-activated concrete are generally higher than those given by prediction models in various codes for conventional concrete. The rate of creep development is also more significant than conventional concrete and does not show signs of slowing down after 365 days of sustained loading.