New approach to calculate water film thickness and the correlation to the rheology of mortar and concrete containing reactive MgO

This study proposes a new method to calculate the water film thickness of the finest particles in a blend, which is based on the close-packing of equal spheres. A series of fluidity and rheological measurements, including flow test, slump test and rheometer test, is conducted on fresh mortar and concrete blends containing different replacement levels of reactive MgO. The results reveal that: (1) water film thicknesses obtained from the new method are better correlated with fluidity/rheological properties of mortar and concrete, compared to the results calculated based on the particle packing density approach; (2) there are three regressions of correlation between fluidity/rheological properties and the water film thickness of finest particles in blends according to the levels of fine particle replacement (0%-10%, 10%-30% and 30%-100%); and (3) the microstructural change of the fresh blends as the incorporation of MgO is the main cause impacting the fluidity/rheological properties.