Effect of triethanolamine hydrochloride on the performance of cement paste

Triethanolamine (C6H15NO3, TEA) is one of the known organic amine accelerators for the cement-based materials. Triethanolamine hydrochloride (C6H15NO3 center dot HCl, TEA center dot HCl), part of whose molecular structure is the same as TEA, can also be regarded as chloride. Thus the water requirement for the normal consistency, setting time, strength, hydration heat liberation, calcium hydroxide (CH) and ettringite (AFt) contents in the hardened paste with TEA center dot HCl were analyzed and the effect of TEA center dot HCl on the performance of cement paste was studied to assess the feasibility of TEA center dot HCl used as an identical accelerator. The results indicate that moderate TEA center dot HCl decreases the water requirement for the normal consistency and this decline is related to the formation of the absorbed film on the cement particle. Zeta electric potential result also proves the appearance of the absorbed film. It also shortens the setting times and alters strengths. But the alterations of setting times and strengths depend on the TEA center dot HCl content. Heat liberation result implies that it delays the end time of the induction period and also postpones tricalcium silicate (3CaO center dot SiO2, C3S) hydration at early age, however moderate TEA center dot HCl increases the rate of C3S hydration in accelerated phase. Excessive TEA center dot HCl accelerates the AFt conversion to monosulfoaluminate (AFm) after several hours. The conversion product is the AFm with 14 H2O. TEA center dot HCl changes the total heat liberation, and these pastes with more TEA center dot HCl liberate more heat before about 12 h, but this case is reverse after about 12 h. X-ray powder diffraction (XRD) and differential thermal analysis (DTA) results conformably confirm that excessive TEA center dot HCl delays C3S hydration and decreases CH content in the hardened paste, but it increases the AFt content in the hardened paste. Hardened pastes with TEA center dot HCl provide the higher content of AFt than the control even at 28d. Heat liberation, CH and AFt contents are closely responsible for the results of the setting times and strengths. These results will provide a reference for the TEA center dot HCl application as an accelerator in the practice. (C) 2018 Elsevier Ltd. All rights reserved.