Effect of C–S–H seed/PCE nanocomposites and triisopropanolamine on portland cement properties: Hydration kinetic and strength

Abstract

The purpose of this study is to investigate the effectiveness of the addition of triisopropanolamine (TIPA) and C–S–H seed/PCE nanocomposites (CPNs) on the strength evolution and hydration kinetics of cement and the relative mechanism. The setting results and isothermal conductivity calorimetry (ICC) results reveal that the addition of CPNs and TIPA significantly shortened the setting time of the cement paste and accelerated the hydration process. Simulations from the kinetic model further demonstrates that the curves of each hydration process (KNG, KI and KD) in the cement paste were influenced by CPNs and TIPA, and the rate of hydration in NG, I and D process is elevated with the admixture. This suggests that the enhancement of hydration behavior and hydration kinetics is closely related to the accelerated nucleation of nanoparticles and the promotion of clinker phase dissolution. Hydrate analysis confirms that CPNs and TIPA ensure the sustained hydration of C4AF, which contributes to the conversion of AFt (ettringite) to AFm (monosulfate). The strength evolution results show that the presence of CPNs and TIPA enhanced the early age strength development at 12 h, 24 h and 72 h and ensured the stability of the strength at the end of 28 days. Although the air content elevates with increasing TIPA incorporation, the analysis of pore structure still reflects its refinement by the additives. Owing to the above, the mechanical strength develops steadily in the later stages and the negative impacts of the increased air content and AFm content are mitigated. These findings are expected to provide novel guidance for the application of CPNs and TIPA to facilitate the performance of the Portland cement at early and later stages.