What are the benefits of adding polycarboxylate superplasticizer to mortar?
Release Time:
2015-08-01
Source:
What are the benefits of adding polycarboxylate superplasticizer to mortar?
Polycarboxylate superplasticizer The effects of polycarboxylate superplasticizer on the workability of cement mortar, its compressive and flexural strengths at different ages, bond strength, impermeability pressure, and volumetric shrinkage behavior at various ages were investigated. The results indicate that the polycarboxylate superplasticizer can effectively enhance the workability and plastic retention of waterproof mortar while also improving its mechanical properties. It enhances workability and impermeability, reduces volumetric shrinkage of waterproof mortar, and improves its durability.
Waterproofing and leakage in building structures have long been a persistent challenge for the construction industry; therefore, the development of waterproofing technologies and materials has become a critical research topic in the field and an urgent issue that researchers must address. Polymer-modified cement-based waterproofing mortar is primarily composed of cement, fine aggregate, and fillers, with polymer additives incorporated. A composite system is formulated by modifying mortar with waterproof emulsions or redispersible latex powders and incorporating appropriate admixtures such as dispersants and defoamers. Unlike traditional rigid waterproof mortars, polymer-modified cement waterproof mortars contain both inorganic hydraulically setting binders and organic polymeric polymers. The inorganic binder (e.g., cement) primarily serves as the skeletal framework, providing bond strength to the substrate and contributing to the long-term durability and strength development of the waterproof mortar; meanwhile, the polymer emulsion forms a film that is uniformly dispersed throughout the mortar matrix, enhancing internal cohesion and compactness upon curing, thereby significantly improving the mortar’s impermeability, bond strength, crack resistance, and corrosion resistance. Polymer-modified cement waterproof mortars eliminate the drawback of flexible waterproofing materials—namely, their low inherent strength requiring the application of a protective layer—and offer a simple construction process: no leveling or protective layers are needed, and they can be applied directly onto damp substrates. After hardening, these mortars exhibit excellent compatibility with the substrate, high bond strength, superior durability, and low cost, which has led to their widespread promotion and application.
The addition of polycarboxylate superplasticizer can impart superior performance to mortar, specifically as follows:
1) After the addition of polycarboxylate superplasticizer, the workability and plastic retention of the waterproof mortar are improved, allowing for a construction window of up to 1 hour.
2) The addition of a dispersant containing amine groups with early-strength-enhancing effects can promote the early hydration of cement and increase the early compressive strength of waterproof mortar.
3) Polycarboxylate superplasticizers can enhance the workability of waterproof mortar and reduce the amount of mixing water, thereby decreasing the porosity of the mortar, increasing the mechanical interlock between the mortar and the coating, blocking moisture transmission pathways, and increasing resistance to water penetration, ultimately improving the waterproofing performance of the mortar.
4) Waterproof mortar incorporating a water-reducing admixture exhibits fewer internal pores and a denser microstructure, resulting in lower early-age chemical shrinkage and later-stage drying shrinkage compared with the other control specimens.
