Effect of the sulphoaluminate cement clinker-anhydrite blend content on properties of Portland cement-sulphoaluminate cement clinker-anhydrite ternary binder mortar incorporating EVA redispersible polymer

In order to better understand the hydration and performance evolution of Portland cement-sulphoaluminate cement clinker-anhydrite (PC-CSA-CS) ternary binder, as well as its applications in polymer modified cement mortar to prepare special mortars, in this paper the effects of the sulphoaluminate cement clinker-anhydrite blend (CSA-CS blend) content on the properties, hydration characteristics, and microstructure of PC-CSA-CS ternary binder mortar incorporating EVA redispersible polymer were systematically studied. The results show that the addition of CSA-CS blend significantly decreases the fluidity,setting time and air content, while enhancing water retention rate and bulk density. The addition of CSA-CS blend also leads to a significant increase in both flexural and compressive strengths at different curing ages. The 28-d flexural and compressive strengths at 40 % CSA-CS blend increase by up to 53.3 % and 27.1 % respectively compared with the control sample. However, with its content increase, the addition of CSA-CS blend increases the capillary water absorption and drying shrinkage to some extent. The increase in the CSA-CS blend content speeds up the hydration process, encourages ettringite formation, and simultaneously reduces the amount of portlandite. After 28 d of hydration, the ettringite content increases by more than 5 times and the portlandite content decreases by over 90 % at 40 % CSA-CS blend compared with the control sample. Significantly, when the CSA-CS blend content exceeds 30 %, only minimal amounts of portlandite can be observed. The addition of the CSA-CS is capable of achieving pore structure optimization. With the increase in the CSA-CS blend content, a decrease trend exists in macro pores, pore volume and porosity, while the proportion of capillary pores first increases and then decreases. And the capillary water absorption variation corresponds to the content of capillary pores.