The water-retaining and thickening material can play the following roles:
① To improve the water retention and operability of mortar. Operability includes fluidity, cohesiveness and thixotropic property. If the fluidity is not good, mortar cannot be plastered; if the cohesiveness is not good, mortar is more scattered during plastering, cannot cloud together and cannot maintain good continuity; if the thixotropic property is not good, it is not easy for spreading and leveling of mortar. The water-retaining and thickening material helps to increase the cohesiveness of mortar, make mortar soft and not scattered, and easy to operate.
② To increase the adhesion capacity. Since mortar becomes soft, it can have contact with the base and is not easy to fall off.
③ To prevent mortar from bleeding and segregation. The water-retaining and thickening material can make the mixing water uniformly distributed in the mortar and maintain long-term stability, without bleeding. Meanwhile, due to the increase in the viscosity of slurry, the particles such as aggregates are not easy to move, thereby effectively preventing segregation and making mortar always maintain good uniformity.
④ To make mortar maintain a certain amount of water over an extended period. The water has two roles. One is to ensure the normal hydration of cementitious materials. Without water, the hydration reaction cannot go on normally, while the performance of hardened mortar has a close relation with the hydration reaction. The other is to prevent cracking. One important reason for cracking of mortar is that too early loss of moisture in the mortar causes greater dry shrinkage deformation.
⑤ To improve the resistance to penetration and frost. It makes the moisture in the water adsorbed on the surface of particles and reduces the amount of free water in the mortar, thus reducing the pores left hence, improving the pore structure in the hardened mortar, and thereby improving the resistance to penetration and frost of mortar.
⑥ Easy for thin layer construction of mortar. Since the water-retaining and thickening material enables the mortar to become soft and sticky, it is better for plastering; due to the better water retention effect, it effectively prevents the moisture in the mortar from being sucked by base materials or evaporation.