Effect of Rubber Powder on the Bond Strength of Cement-Based Materials
Release Time:
2021-09-17
Source:
Latex powder
The Influence of Rubber Powder on the Bond Strength of Cement-Based Materials
After film formation, emulsions and redispersible latex powders can develop high tensile strength and bond strength on various substrates. When incorporated into mortar as a secondary binder, they synergistically interact with the inorganic binder—cement—allowing each component to leverage its respective strengths and thereby enhancing the overall performance of the mortar. Microstructural analysis of polymer–cement composites indicates that the addition of redispersible latex powder enables the polymer to form a continuous film that becomes part of the pore walls; through internal cohesive forces, this film integrates the mortar into a monolithic structure, increasing its cohesive strength, raising its failure stress, and expanding its ultimate strain. Long-term performance studies of redispersible latex powder in mortar, conducted via SEM, reveal that even after 10 years, the polymer’s microstructural morphology within the mortar remains unchanged, maintaining stable bond strength, flexural and compressive strength, and excellent hydrophobic properties. Wang Ziming et al. [11] investigated the mechanism by which redispersible latex powder contributes to the development of bond strength in tile adhesives, finding that once the polymer dries and forms a film, the polymer film not only establishes a flexible interface between the mortar and the tile but also increases the air content of fresh mortar, thereby influencing surface texture and wettability. During setting, the polymer further exerts favorable effects on cement hydration and shrinkage within the adhesive matrix, all of which collectively enhance bond strength.
The addition of redispersible latex powder to mortar can significantly enhance bond strength with other materials. This is because the hydrophilic latex powder, together with the liquid phase of the cement slurry, penetrates into the pores and capillaries of the substrate; within these voids, the latex powder forms a film and adheres strongly to the substrate surface, thereby ensuring excellent bond strength between the binder and the substrate.
The optimization of the workability of mortar by latex powder stems from the fact that latex powder is a polymer with polar functional groups. When latex powder is mixed with EPS particles, the nonpolar segments of the latex polymer’s main chain undergo physical adsorption onto the nonpolar surface of the EPS particles. Meanwhile, the polar functional groups of the polymer orient themselves outward on the EPS particle surfaces, transforming the hydrophobic EPS particles into hydrophilic ones. This surface modification of the EPS particles effectively addresses the problems of EPS particles easily floating to the surface upon contact with water and excessive segregation in the mortar. Upon subsequent addition of cement and mixing, the polar functional groups adsorbed on the EPS particle surfaces interact with the cement particles, leading to strong interfacial bonding and thereby significantly improving the workability of the EPS-insulated mortar. This is manifested in the ease with which the EPS particles are wetted by the cement paste, resulting in a substantial increase in the bond strength between them.
