Small oscillatory rheology and cementitious particle interactions

Oscillatory rheology has proved a promising method to measure the nature of interactions between inorganic particles in suspension. In this work, small oscillatory rheology (SAOS) is used to compare the nature of interactions in an ordinary Portland cement (OPC) and a more sustainable alkali-activated binder (AAB). The interstitial solution of the AAB is varied by adding calcium chloride. The linear elastic regime is characterized as a function of volume concentration, in a range for which an attractive gel-like behavior is observed. SAOS measurements show that the nature of interactions in AAB is different from those in OPC and changes with calcium concentration. The influence of calcium over the surface properties of AAB is further proven by the fluidifying effect of polycarboxylether (PCE) when [Ca2+] is increased. The results obtained confirm the relevance of SAOS to qualitatively assess the state of aggregation in cementitious slurries and select candidates for cement substitution.