In mortar, cellulose ether plays the role of water retention, thickening, delaying cement hydration power, and improving construction performance. Good water retention capacity makes cement hydration more complete, can improve the wet viscosity of wet mortar, increase the bonding strength of mortar, and adjust the time. Adding cellulose ether to mechanical spraying mortar can improve the spraying or pumping performance and structural strength of the mortar. Cellulose is widely used as an important additive in ready-mixed mortar. Taking the field of building materials as an example, cellulose ether has excellent properties such as thickening, water retention, and retardation. Therefore, building material grade cellulose ether is widely used to improve the production of ready-mixed mortar (including wet-mixed mortar and dry-mixed mortar), PVC resin, etc. , latex paint, putty, etc., including the performance of building material products.
Cellulose can delay the hydration process of cement. Cellulose ether endows mortar with various beneficial properties, and also reduces the early hydration heat of cement and delays the hydration dynamic process of cement. This is unfavorable for the use of mortar in cold regions. This retardation effect 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 hydration process. The higher the concentration of cellulose ether in the mineral gel material, the more pronounced the effect of hydration delay. Cellulose ether not only delays setting, but also delays the hardening process of the cement mortar system. The retarding 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 retarding effect of cellulose ether. The ratio of hydrophilic substitution to water-increasing substitution The retarding effect is stronger. However, the viscosity of cellulose ether has little effect on cement hydration kinetics.
With the increase of the content of hydroxypropyl methylcellulose ether, the setting time of the mortar increased significantly. There is a good nonlinear correlation between the initial setting time of mortar and the content of cellulose ether, and a good linear correlation between the final setting time and the content of cellulose ether. We can control the operational time of the mortar by changing the amount of cellulose ether.
Post time: Mar-09-2023