Synergistic effect of aluminum sulfate and triethanolamine on the hydration of metakaolin blended cement

Shotcrete is regarded as an indispensable component in the construction of tunnels and mines, which can stabilize the tunnel wall and prevent groundwater infiltration. Along with the massive railway construction in China's mountainous region, it is unavoidable to build more tunnels, and then the used amount of shotcrete increases dramatically. Calcined clay blended cement is one promising low‐carbon cementitious material and metakaolin (MK) is the main reactive component in calcined clay. Considering the high demand for shotcrete and the urgently needed carbon neutrality in China, it is necessary to contain more MK in the cement of shotcrete.

Beside the cement, accelerator is also necessary for the production of shotcrete. Aluminum sulfate (AS) and triethanolamine (TEA) are two representative components in the alkali‐free liquid accelerator. However, limited researches were conducted regarding the synergistic effect of AS and TEA on the setting and hardening performance of the metakaolin blended cement (OPC‐MK).

Hence, in order to clarify the effect of TEA and AS on the hydration of OPC‐MK, different dosages of TEA were added to AS solution and their effects on setting performance, compressive strength and hydration kinetics of OPC‐MK were investigated. It is found that, with the presence of both AS and TEA, a high dosage of TEA facilitates the reaction of the aluminate phase while greatly retards the silicate reaction. More importantly, TEA can promote the dissolution and pozzolanic reaction of MK. Thereby a dense structure can be formed and the compressive strength of pastes at 28 d is enhanced. At last, the interactions between TEA, AS and OPC‐MK is thoroughly analyzed, which could provide a theoretical basis for the wide application of low‐carbon cement in shotcrete.