Effect of synergistic action of C-S-H seeds and liquid accelerator on early hydration of Portland cement
Zhihong Wu, Jin Wang, Jiawei Wang, Yuexin Pan, Jingzhi Peng, Rui Li, Huafeng Zhou
Abstract
At present, the requirements for liquid accelerators in shotcrete construction were getting more stringent. A major problem was the poor early-age strength of the mortar, caused by the limited levels of hydration products . Recent research showed that introducing C-S-H seeds enriched hydration products and enhanced early-age strength without affecting later-age strength in cement. However, preparing C-S-H seeds was costly and difficult to apply widely. Thus, fly ash (FA) and carbide slag (CS) were used to synthesize C-S-H seeds via hydrothermal methods , which were combined with liquid accelerators to promote the early age strength development of cement and decrease the costs of C-S-H seeds. The research demonstrated that 1 % C-S-H seeds and 7 % liquid accelerator make compressive strengths of 9.73 MPa and 44.39 MPa at 1 d and 28 d, respectively. The analysis showed that the C-S-H seeds promoted the formation of ettringite (AFt) and its uniform dispersion in the cement matrix . They also facilitated tricalcium silicate (C 3 S) hydration, which not only enriched the hydration products but also reduced porosity and significantly enhanced the compressive strength of the mortar. Cost estimates indicated that the synergistic use of C-S-H seeds with a liquid accelerator could save about 8.96 CNY/m 3 construction, providing significant economic benefits for engineering applications .