New Generation Amphoteric Comb-like Copolymer Superplasticizer and Its Properties

Abstract

The incorporation of high performance superplasticizers in concrete is one of the most effective and economic technological methods for achieving sustainable development in the concrete industry. Conventional polyelectrolyte-type superplasticizers have some defects, e.g. poor dispersibility, large slump loss, increasing the shrinkage of concrete and pollution when being manufactured. Although the new generation of comb-like polycarboxylate superplasticizers has remarkable benefits in practice, it also has the shortcoming of low saturation dosage. In this study, based on adsorption-dispersion mechanism of dispersant and polyampholyte solution theory, a new class of amphoteric comb-like copolymer superplasticizer (PACP) was designed and synthesized. The effects of PACP on water reduction, setting, compressive strength, hydration and pore structure were investigated systematically. Results show that PACP can be dosed in small amounts to obtain a water reduction up to 45%. The addition of PACP also does not retard cement hydration and significantly increases the compressive strength of hardened concrete at early and ultimate stages. Moreover, PACP can further improve the rate of heat evolution, delays the time to reach the highest hydration temperature and refines the pore structure of hardened cement paste markedly, leading to decreases of porosity and average pore size.