Synergic effect of triethanolamine and C-S-H seeding on early hydration of the limestone calcined clay cement in UHPC

In order to significantly reduce the carbon emission of UHPC, limestone calcined clay cement (LC3) could be used to prepare ultra-high-performance concrete (UHPC). However, the low early strength of LC3-UHPC restricts its application. Herein, the synergic effect of triethanolamine (TEA) and C-S-H seeding on improving the early hydration of LC3-UHPC incorporated alite-rich cement was investigated. Results illustrated that TEA retarded the early hydration of alite-rich LC3 paste but accelerated the hydration after 1d. In contrast, C-S-H seeding directly provided nucleation sites, promoted the hydration of C3S, shorten the induction period, and advanced the exothermal peak by about 5 h. The synergic effect of the two admixtures could overcome the retard effect of TEA on paste and significantly improve the early hydration and strength of LC3-UHPC. Moreover, the synergic effect of C-S-H seeding and TEA promoted pozzolanic reaction of calcined clay, which decreased silicate phase content and increased the amorphous phase, the chain length of C-S-H gel, and the value of Al/Si, leading to the decrease of the porosity and increase of the compressive strength.