Study On Liquid Aluminate Accelerating Additive

In this paper, the types and characteristics of spray concrete accelerating additive, the actualities and development trends of its research and application in home and abroad were introduced in detail. The advantages and disadvantages of liquid aluminate accelerating additive were analyzed; and the necessity to further study the liquid aluminate accelerating additive was pointed out.Based on the mono-factor method, the influences of synthetic technology parameters on the setting time and stability of the liquid aluminate accelerating additive matrix were investigated, which include the mole ratio of NaOH to Al(0H)3, the consistency of matrix liquid, the synthetic temperature and time. The reasons of each parameter influencing on the matrix liquid were analyzed. Finally, the optimal synthetic technology parameters of the liquid aluminate accelerating additive matrix were obtained. The experiment results show that the liquid aluminate accelerating additive based on the optimal synthetic technology parameters are stable for long time without deposit; 1d compressive strength was increased by 40%; the loss ratio of 28d compressive strength was little than 20%; the adaptability of this accelerating additive with most of cement was satisfactory.For improving the adaptability of the liquid aluminate accelerating additive with cement, the promoting effects of some accessory ingredients added into the liquid aluminate accelerating additive were studied. It was found that triethanolamine. polyacrylamide and potassium dichromate can form an even and stable system with the liquid aluminate accelerating additive matrix; the adaptability of the accelerating additive with cement was improved obviously; and the comprehensive performances were enhanced.The influences of the dosage of accelerating additive, the time of the accelerating additive mixed to cement paste, the ratio of water to cement, the kinds and contents ofthe gypsums in the cement on the liquid aluminate accelerating additive were also studied.Finally, the accelerating mechanism of the liquid aluminate accelerating additive was explored by the means of XRD. The results show that the aluminate sodium reacts with the gypsums and Ca(OH)2 in cement to producing a lot of ettringite quickly, which accelerates the hydration of C3A; at the same time, the Ca2+ is largely consumed causing the shortering or disappearing of the induction period of C3S, which accelerates the hydration of C3S. For above all, the fresh cement mortar sets and hardens.