改性氯氧镁水泥砂石混凝土强度的试验研究

基于不同的MgO/MgCl2 、H2O/MgCl2物质的量比,试验中混合不同量的氧化镁、砂子、石子、抗水剂以及三种传统矿物掺合料拌制氯氧镁水泥混凝土,并测定其早期(7～28 d)和后期(28 ～ 128 d)抗压强度.试验证明,添加不同矿物掺合科(硅灰,矿粉,粉煤灰)镁水泥强度发展趋势相同但强度发展程度不同,其中以粉煤灰混凝土强度最高.由于复合抗水剂的存在,早期吸潮返卤被抑制,强度发展良好.后期混凝土强度发生下降,随着养护进行,强度又恢复发展.通过微观手段(X射线衍射、扫描电镜和能谱图)发现,含有粉煤灰的镁水泥混凝土样品微观结构存在致密凝胶相.

Experimental Investigation on Strength Development of Modified Magnesium Oxychloride Cement Concrete

Basing on different MgO/MgCl2 and H2O/MgCl2 molar ratios,the magnesium oxychloride cement(MOC) concrete was formed by adding the mixture of MgO,gravel,sand,water-resisting admixture and three kinds of mineral admixtures(fly ash,silica fume and mineral powder) into magnesium chloride solution(MCS).The test blocks were demoulded and tested at 7 d,14 d,28 d,56 d,90 d and 128 d aging time.The rules of strength develop was summarized as early and late strength development.The patterns of compressive strength development showed the same trend,but the numerical value varied with different mineral admixtures,as the concrete with fly ash performed the highest,while that with mineral powder showed the lowest.The late development of all mixture proportions fluctuated.That was,the strength dropped at a certain aging time,and then the development was resumed as the curing proceeded.XRD,SEM and EDS was used to analyze the micro-mechanism,and the dense gel phase was found in MOC concrete with fly ash.The strength loss,as the result of the active magnesia,was overall controllable due to the existence of WRA.