Setting retardation of cellulose ethers

The retardation of cellulose ether: The third function of cellulose ether is to delay the hydration process of cement. Cellulose ether imparts various beneficial properties to the mortar, and also reduces the early hydration heat release of cement and delays the hydration kinetic process of cement. This is unfavorable for mortar use in cold regions. This retardation is caused by the adsorption of cellulose ether molecules on hydration products such as C-S-H and ca(OH)2. Due to the increase in the viscosity of the pore solution, the cellulose ether reduces the mobility of ions in the solution, thereby delaying the hydration process.

The higher the concentration of cellulose ether in the mineral gel material, the more pronounced the effect of hydration delay. Cellulose ethers not only retard setting, but also retard the hardening process of cement mortar systems. The retardation effect of cellulose ether depends not only on its concentration in the mineral gel system, but also on the chemical structure. The higher the degree of methylation of HEMC, the better the retardation effect of cellulose ether. The retardation effect is stronger. However, the viscosity of cellulose ether has little effect on the hydration kinetics of cement.

With the increase of cellulose ether content, the setting time of mortar increases significantly. There is a good nonlinear correlation between the initial setting time of mortar and the content of cellulose ether, and the final setting time has a good linear correlation with the content of cellulose ether. We can control the operational time of the mortar by changing the amount of cellulose ether.