INFLUENCE OF CALCIUM SULFATE ON DEVELOPMENT OF EARLY-AGE RHEOLOGICAL PROPERTIES IN SELF-LEVELING UNDERLAYMENTS BASED ON ETTRINGITE BINDER

Abstract

The aim of this study is to evaluate the effect of the types and the amount of calcium sulfate (C$Hx) replacing calcium aluminate cement (CAC) in ettringite binder on the early-age rheological properties of self - leveling underlayment. The evolution of rheological properties such as yield stress, plastic viscosity, rheological dynamic modulus (storage modulus and loss modulus) was determined by a rheometer with the rotation mode and the oscillation mode. The use of these technics is considered as a method to monitor the development of structure in cementitious materials. Increasing the yield stress, plastic viscosity and dynamic modulus of the self - leveling underlayment during hydration was identified from just 5 minutes after mixing to the period where the transition from a fluid state to a solid state where the development of elastic properties in the self - leveling underlayment takes place. The result shows that the structuration of compositions based on anhydrite (C$ - CaSO₄) or compositions containing 90CAC/10C$Hx is faster than that of the composition 75CAC/25C$Hx or the compositions based on hemihydrate (C$H_0.5 or CaSO₄0.5H₂O).

Keywords: Self - leveling underlayment; calcium aluminate cement; calcium sulfate; ettringite binder; rheological properties.

Received: August 24^th, 2016, revised: September 5^th, 2016, accepted: October 13^th, 2016