干湿循环下再生细骨料混凝土的氯离子渗透性能

Chloride Ion Permeability of Recycled Fine Aggregate Concrete under Dry-Wet Cycles

考虑到天然砂的日益短缺和废弃混凝土造成的环境危机,采用不同取代率的再生细骨料(RFA)制备再生细骨料混凝土(RFAC),分析其在干湿循环下的性能演化规律,研究其抗氯离子侵蚀性能。结果表明:RFA的加入降低了混凝土的抗压强度,当RFA质量取代率为100%时,RFAC的28 d抗压强度是普通混凝土的77.0%;在干湿循环作用下,RFAC自由氯离子含量随着侵蚀深度的增加先增加后减小最后趋于稳定,并出现明显的氯离子对流区和扩散区,对流区深度约为5 mm,且随着干湿循环次数和RFA取代率的增加,对流区深度也不断增大;随着干湿循环次数增加,RFAC的孔隙率呈指数增大;在干湿循环作用下,RFA取代率高的混凝土孔隙率增大更明显,此为其抗氯离子侵蚀能力变差的原因。

Considering the shortage of natural sand and the environmental crisis caused by waste concrete,recycled fine aggregate(RFA)with different replacement rates was used to prepare recycled fine aggregate concrete(RFAC),the evolution law of RFAC performance under dry-wet cycle was analyzed,and chloride ion erosion resistance of RFAC was studied.The results show that the compressive strength of concrete is reduced by the addition of RFA.The 28 d compressive strength of RFAC with RFA mass replacement rate of 100%is 77.0%of ordinary concrete.The free chloride ion content of RFAC increases first and then decreases and finally stabilizes with the increase of erosion depth under the dry-wet cycle.The convection zone and diffusion zone of chloride ion appeares obviously,and the depth of the convection zone is about 5 mm,and the depth of the convection zone also increases with the increase of the dry-wet cycles times and the RFA replacement rate.The porosity of RFAC increases exponentially with the increase of dry-wet cycles times.The porosity of concrete with high RFA replacement rate increases more obviously under dry-wet cycle,which is the reason why its chloride ion erosion resistance becomes worse.