偏高岭土对高强机制砂混凝土性能的影响

利用扫描电子显微镜(SEM)、压汞法(MIP)、快速氯离子迁移系数法(RCM)等手段,研究了偏高岭土(MK)掺量对高强机制砂混凝土抗压强度以及抗氯离子渗透性能的影响.研究发现: 掺入MK能够有效改善高强机制砂混凝土的力学性能和抗氯离子渗透性能:随MK掺量增加,抗压强度与抗氯离子渗透性能均呈先增大后减小的趋势,最佳MK掺量为8%,此时28 d抗压强度为98.5 MPa,较基准组增加13%,氯离子迁移系数为1.89×10^-12 m²/s,较基准组减小60%.微观结构试验表明适宜的偏高岭土掺量能够有效促进水泥水化;偏高岭土颗粒的晶核效应和微集料填充效应协同作用,使得机制砂混凝土的微观结构更加均匀密实,机制砂混凝土的多害孔、有害孔减少,少害孔增加,从而提高了机制砂混凝土抗压强度和抗氯离子渗透性能.

Effect of metakaolin content on performance of high strength manufactured sand concrete

The effects of metakaolin(MK)content on the compressive strength and resistance to chloride ion penetration of high strength manufactured sand concrete were studied by using scanning electron microscope(SEM), mercury intrusion method(MIP), and rapid chloride ion mobility coefficient(RCM)methods. The study finds that the addition of MK can effectively improve the mechanical pro-perties and resistance to chloride ion penetration of high strength manufactured sand concrete. With the increase of the amount of MK, both the compressive strength and the resistance to chloride ion pene-tration increase first and then decrease. The optimal MK content is 8%. At this time, the 28-day compressive strength is 98.5 MPa, which is increased by 13% compared with the benchmark group, and the chloride ion migration coefficient is 1.89×10^-12 m²/s, which is 60% lower than the benchmark group. The microstructure test shows that the appropriate amount of metakaolin can effectively promote cement hydration. The synergistic effect of MK particle nucleation effect and micro aggregate filling effect of metakaolin particles makes the microstructure of the machined sand concrete more uniform and dense. The number of harmful holes and harmful holes of manufactured sand concrete are reduced, and fewer harmful holes are increased, and thereby improving the compressive strength and resistance to chloride ion penetration of the sand concrete.