Effect of Rubber Powder on the Durability of Cement-Based Materials
Release Time:
2021-10-11
Source:
Effect of Rubber Powder on the Durability of Cement-Based Materials
The Influence of Rubber Powder on the Durability of Cement-Based Materials
The formation of a continuous polymer film is critically important for the performance of polymer-modified cement mortar. During the setting and hardening of cement paste, numerous voids develop within the matrix, creating weak points in the material. Upon addition of redispersible latex powder, the powder rapidly disperses into an emulsion upon contact with water and migrates to water-rich regions—namely, the voids. As the cement paste sets and hardens, the mobility of the polymer particles becomes increasingly constrained, and the interfacial tension between water and air drives the particles to gradually aggregate. Once the polymer particles begin to come into contact with one another, the network-like water content evaporates through capillary action, and the polymer forms a continuous thin film around the voids, thereby reinforcing these weak areas. At this stage, the polymer film provides hydrophobic protection without blocking the capillaries, resulting in a material that exhibits both excellent hydrophobicity and breathability.
Cement mortar without polymer additives exhibits a very loose internal structure, whereas polymer-modified cement mortar, owing to the presence of a polymer film, achieves a much more cohesive and uniform matrix, resulting in superior mechanical properties and weather resistance. In latex-powder-modified cement mortar, the latex powder increases the porosity of the cement paste while reducing the porosity of the interfacial transition zone between the cement paste and the aggregates, thereby keeping the overall porosity of the mortar essentially unchanged. Once the latex powder forms a continuous film, it effectively seals the pores within the mortar, leading to a denser microstructure in the interfacial transition zone between the cement paste and the aggregates. Consequently, the permeability resistance of the latex-powder-modified mortar is enhanced, improving its ability to resist attack by aggressive agents and thereby positively contributing to the durability of the mortar.
