Viscosity-enhancing admixtures and the rheology of concrete

Viscosity-enhancing admixtures (VEAs) are water-soluble polymers that increase viscosity and cohesion of cement-based materials. Such enhancement is essential in highly flowable concrete, including self-consolidating concrete (SCC), to control the risk of segregation and to maintain a homogenous suspension in the plastic stage until the onset of hardening. For a given mixture composition, the VEA’s ability to enhance stability can vary widely with the type and dosage rate of the admixture as well as that of the high-range water reducer often needed to maintain the targeted fluidity. This chapter discusses the mode of action of various types of VEAs and their effect on the rheological properties and workability of various types of cement-based materials.