低碳复合胶凝材料对水泥和混凝土性能的影响

Effect of low-carbon composite cementitious materials on properties of cement and concrete

将粉煤灰和矿粉按不同质量比(m_(粉煤灰)∶m_(矿粉)=7∶3、6∶4、5∶5)制备成了低碳复合辅助性胶凝材料,研究了其等质量替代15%、30%的水泥对胶凝材料需水量比、流动度比和活性指数的影响,优选出了最佳m_(粉煤灰)∶m_(矿粉)。在此基础上,研究了低碳复合辅助性胶凝材料等质量替代0、10%、15%、20%、30%的水泥对胶凝材料标准稠度用水量和凝结时间的影响,以及等质量替代0、10%、20%、30%、40%的水泥对C50混凝土工作性和力学性能的影响。结果表明:在水泥中掺入适量低碳复合辅助性胶凝材料有效改善了胶凝材料体系的工作性,延缓了早期(3 d)水化速度,提高了胶砂7 d、28 d抗压强度,最佳m_(粉煤灰)∶m_(矿粉)为5∶5;随着低碳复合辅助性胶凝材料掺量的增加,胶凝材料的标准稠度用水量变化很小,凝结时间延长;C50混凝土的坍落度随着低碳复合辅助性胶凝材料掺量的增加而增大,7 d和28 d抗压强度先增大后减小,最佳掺量为30%。

Low-carbon composite auxiliary cementitious materials were prepared by using fly ash and mineral powder in different mass ratios(m_(fly ash)∶m_(mineral powder)=7:3,6:4,5:5),and the effects of replacing 15%and 30%of cement with equal mass ratios on the water demand ratio,flowability ratio,and activity index of the cementitious materials were studied,and the optimal m_(fly ash)∶m_(mineral powder) was selected.On this basis,the influence of replacing 0,10%,15%,20%,and 30%of cement with low-carbon composite auxiliary cementitious materials on the standard consistency water consumption and setting time of cementitious materials was studied,and the effects of replacing 0,10%,20%,30%,and 40%of cement on the workability and mechanical properties of C50 concrete were studied.The results show that adding an appropriate content of low-carbon composite auxiliary cementitious materials to cement effectively improves the workability of the cementitious materials system,delays the early(3 d)hydration rate,and increases the compressive strength of the mortar at 7 d and 28 d,and the optimal m_(fly ash)∶m_(mineral powder) is 5:5.With the increase of low-carbon composite auxiliary cementitious materials content,the standard consistency water consumption of cementitious materials changes very little,and the setting time is extended.With the increase of low-carbon composite auxiliary cementitious materials content,the slump of C50 concrete gradually increases,and the compressive strength at 7 d and 28 d first increases and then decreases,and the optimal content is 30%.