The cellulose ether can be used as the water-retaining agent. The water retention effects of cellulose ether can prevent the substrate from absorbing moisture too much and too fast, and can prevent the evaporation of water, in order to ensure sufficient water during hydration of cement.
Generally speaking, the water-holding capacity of cement slurry will be improved with the increase of the content of cellulose ether. The higher the viscosity (molecular weight) of cellulose ether added is, the better the water-holding capacity will be. The cellulose ether can increase the viscosity of the liquid and therefore, can be used as a thickener. It has played an important role in the coating, latex paint and cement grouting material. In fact, HPMC has served as a protective colloid, and has overcome the flocculation of solid particles. The cement slurry with the addition of HPMC has higher viscosity, and the slurry is not easy for layering. The total time needed for the the mixing process and construction operation will be less, which helps to improve the workability of mortar.
The smaller the powder particles are, the better the solubility of cellulose ether fully dispersed in water will be and the shorter the time needed to achieve the desired final viscosity will be, so that the standing and curing time can be shortened. In addition, the temperature and pH value also have an impact on the role of cellulose ether.
The cellulose ether has the characteristic, not easily soluble in hot water but easily soluble in cold water. For most of cellulose ethers, when the temperature of aqueous solution is below the gel point, the lower the solution temperature is, the higher the viscosity will be and the more obvious the water retention and thickening effects will be. For some varieties, there is no gel point. For example, carboxymethyl cellulose and hydroxy ethyl cellulose ethers can be dissolved in both cold and hot water.