Rheological properties of fresh cement pastes and clinker reactivity

This paper presents research results concerning the influence of clinker reactivity on rheological properties of cement pastes at early stages of hydration (lasting less than one hour). The research was carried out on clinkers synthesized in a laboratory, on non-alkaline cements and cements containing in-built alkalis (sodium, potassium) in the clinker phase.The clinker reactivity was estimated from the flow curves and stress changes in time occurring in clinker pastes while maintaining constant measurement parameters. It was found that the effectiveness of gypsum as a setting controller depends on clinker reactivity. Increased clinker reactivity is accompanied by a decreased consistency of a cement paste.The research results indicate that decreased reactivity of clinkers containing inbuilt alkalis is connected with decreased setting controlling effectiveness of added gypsum. This is manifested by a consistency increase of such system at early stages of hydration.