Experimental and mesoscale simulation studies of micro-mechanical properties of alite mixed with NaCl solutions

Abstract

To conserve freshwater resources, seawater may be used for concrete production. As sodium chloride (NaCl) is the most abundant mineral found in seawater, in this study, we focused on the effects of NaCl on the hydration of alite, which is the major clinker phase in Portland cement, and its hydration dominates the mechanical behaviour of cement pastes. NaCl solutions with varying concentrations were mixed with alite at a solution-to-binder ratio of 0.5. Then, a combination of experiments and mesoscale simulation was utilized to study the influence of NaCl on the micro-mechanical properties of alite pastes. The nanoindentation test showed the improving micro-mechanical properties of alite pastes with increasing NaCl concentration. The pore size distribution analysis agreed with mesoscale simulation on the reduced porosity, and the latter showed increased cohesion. The porosity and cohesion changes were initiated by the ionic effects of Na+ and Cl− that modify the Debye length of C-S-Hparticle and dielectric constant of the C-S-Hgel pore solution.