Preparation of high performance composites strength accelerator for cement containing fly ash and ground granulated blast-furnace slag

The strength enhancing efficiency and mechanism of five kinds of strength accelerator in cement containing fly ash and ground granulated blast-furnace slag were compared, then the optimum compositions were developed by means of progressing composition with them. Further researches were carried out about the effects of three kinds of retarder on the strength accelerating efficiency of those optium compositions. In the end, a high performance composite strength accelerator was developed. The results indicate that there exists obvious additive strength accelerating effects among triethanolamine, inorganic salt A, sodium formate and calcium chloride, which will accelerate the hydration of C 3A and C 3S in the cementing system, but the additive hydration accelerating effects on C 3A will influence their inherent acceleration for the hydration of C 3S and consequently have adverse function to the development of later age strength of the system. Such retarders as sucrose, sodium tripolyphosphate, organic acid B can efficiently reduce the acceleration effects of hydration of C 3A from the former composite strength accelerators and enhance the hydration of C 3S, which can make the composite strength accelerator act nearly in a balanced state. The final formula of the high performance composite strength accelerator obtained from the research is: triethanolamine 0.02% + inorganic salt A 0.06% + sodium formate 0.06% + organic acid B 0.01%, the mixing content accounts for 0.15% of the total cementing materials. It can improve 3 d compressive strength 78.3% and 7 d compressive strength 46.1% with little change of fluidity and setting time.