Elucidating the Role of Supplementary Cementitious Materials on Shrinkage and Restrained-Shrinkage Cracking of Flowable Eco-Concrete

摘要

This study investigates the influence of composition and the resultant reaction of blended binders proportioned with a high volume of supplementary cementitious materials (SCMs) on shrinkage and restrained shrinkage cracking of flowable and ecologically friendly concrete (Eco-concrete). Concrete mixtures were designed using optimized particle packing of aggregate skeleton to secure relatively low binder content of 315 kg/m~3, containing 50% SCM replacement. Hydration kinetics using isothermal calorimetry, thermogravimetric analysis, autogenous and drying shrinkage, capillary water absorption, and development of mechanical properties were evaluated to characterize the effect of binder composition on shrinkage-induced cracking and tensile creep behavior of Eco-concrete. Test results indicate that mixtures provisioned with SCMs exhibited up to 60% longer time to cracking and developed 2.4-4.4 times larger tensile creep coefficient at the time of crack initiation compared to the control mixture without any SCM. Such spread can be attributed to (1) resultant reaction and pozzolanic activity, and (2) improved capillary porosity induced by SCMs, which can control the rate of elastic properties evolution and shrinkage at early and later age. Good correlations were established between hydration kinetics of the binders and shrinkage cracking tendency of Eco-concrete that can be applied for designing more sustainable binder systems with high shrinkage cracking resistance.