Effects of Carboxymethyl Cellulose (CMC) in Dry Mortar in Construction


Molecular Formula of CMC: [C6H7O2(OH)2och2COONa]n


It is an ionic cellulose ether made through a series of reaction treatment from natural fibers (such as cotton) after the alkali treatment and with the use of a sodium monochloroacetic acid as the etherifying agent.


1. Carboxymethyl cellulose has larger hygroscopicity, and will contain a larger amount of water at storage under general conditions.


2. The aqueous solution of carboxymethyl cellulose will not produce gels. The viscosity decreases with increasing temperature. When the temperature exceeds 50℃, the viscosity is irreversible.


3. Its stability is greatly affected by the pH value. Generally it can be used in the gypsum-based mortar but can not be used in the cement-based mortar. In high alkaline, it will lose viscosity.


4. Its water-holding capacity is much lower than that of methyl cellulose. It has a  retarding effect on the gypsum-based mortar and helps to reduce its strength. But the price of carboxymethyl cellulose is significantly lower than that of methyl cellulose.