Study on the influence mechanism of water reducing agent on the properties of anhydrite-based self-leveling mortar

Abstract

Gypsum-based self-leveling has been widely used for its good construction performance and economy. This paper investigated the influence mechanisms of three kinds of water-reducing agents (WRAs) on the properties of anhydrite-based self-leveling floor screeds (ASLF) through macroscopic performance characterization, rheological model fitting, TG-DSC, MIP, SEM, et al. The outcomes conducted that the types, densities, and lengths of the side chain groups of the WRAs had diverse effects on the hardening, rheological parameters, and crystal morphology of ASLF. In descending order, the influence was PCE > SMF > SNF. The anionic groups of PCE affected the crystal growth by adsorbing on the dominant surface of CaSO4·2H2O and reducing the crystal length-diameter ratio. Simultaneously, with the increase of PCE content, the steric resistance effect increased, and the thickness of the surface water film layer increased, resulting in a decrease in the final viscosity and yield strength. ASLF is a power-law fluid that fits the Hershel-Bulkle (H-B) model well. Compared with PCE, the hydration and hardening characteristics of ASLF mixed with SMF and SNF were similar, and the influence was smaller, but a larger amount was required to ensure flowability. The pore size distribution of ASLF-hardened bodies mixed with various superplasticizers was similar. The hardening properties of ASLF were investigated using a variety of methods in this study. Various types of WRAs were investigated for their effects on the hydration and hardening of anhydrite, providing important reference information for ASLF preparation and production.