Hydration, mechanical properties, and microstructural characteristics of cement pastes with different ionic polyacrylamides: A comparative study

Abstract

Polyacrylamides (PAMs) have been widely used as chemical admixtures to modify the workability of cement-based materials. However, polymers possess variable molecular characteristics that have different effects on the macro- and micro-properties of cement, which need to be further explored. In this study, three different ionic PAMs, namely anionic PAM (APAM), cationic PAM (CPAM), and nonionic PAM (NPAM), were applied to investigate their effects on the hydration and mechanical properties of Portland cement. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) tests were carried out to reveal the evolution of cement phase compositions. The results indicate that APAM significantly delays the cement hydration, increases the cement drying shrinkage, and reduces the cement strength development. However, CPAM and NPAM promote total heat release from the cement. CPAM and NPAM have minor effects on the cement drying shrinkage and strength development compared with APAM. Phase composition analysis reveals that APAM inhibits the dissolution of C3S and promotes the formation of Ca(OH)2 after 1 d. In contrast, CPAM and NPAM mainly enhance the dissolution of C3S before 4 h.