Wang Hailong, Sun Xiaoyan, Wang Junjie, Monteiro Paulo J M
Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China.
Department of Civil and Environmental Engineering, University of California Berkeley, Berkeley, CA 94720, USA.
Materials (Basel). 2016 Mar 30;9(4):252. doi: 10.3390/ma9040252.
The research reported herein studied the permeability of concrete containing recycled-concrete aggregate (RA), superfine phosphorous slag (PHS), and ground granulated blast-furnace slag (GGBS) with and without stress. Test results showed that the chloride diffusion coefficient of RA concrete (RAC) without external loads decreased with time, and the permeability of RAC is much lower than that of the reference concrete due to the on-going hydration and the pozzolanic reaction provided by the PHS and GGBS additives in the RAC mixture. The permeability of chloride under flexural load is much more sensitive than that under compressive load due to the differences in porosity and cracking pattern. At low compressive stress levels, the permeability of chloride decreased by the closing of pores and microcracks within RAC specimens. However, in a relatively short time the chloride diffusion coefficient and the chloride content increased rapidly with the increase of compressive stress when it exceeded a threshold stress level of approximate 35% of the ultimate compressive strength. Under flexural stress, the chloride transport capability increased with the increase of stress level and time. At high compressive and flexural stress levels, creep had a significant effect on the permeability of chloride in the RAC specimens due to the damage from the nucleation and propagation of microcracks over time. It is apparent that mortar cracking has more of a significant effect on the chloride transport in concrete than cracking in the interfacial transition zone (ITZ).
本文报道的研究探讨了含再生混凝土骨料（RA）、超细磷渣（PHS）和磨细粒化高炉矿渣（GGBS）的混凝土在有无应力情况下的渗透性。试验结果表明，无外部荷载时，再生混凝土（RAC）的氯离子扩散系数随时间降低，且由于RAC混合料中PHS和GGBS添加剂持续的水化作用和火山灰反应，RAC的渗透性远低于基准混凝土。由于孔隙率和开裂模式的差异，弯曲荷载下的氯离子渗透性比压缩荷载下的更敏感。在低压缩应力水平下，RAC试件内的孔隙和微裂纹闭合，使氯离子渗透性降低。然而，当压缩应力超过极限抗压强度的约35%这一阈值应力水平时，在相对较短的时间内，氯离子扩散系数和氯离子含量会随着压缩应力的增加而迅速增加。在弯曲应力作用下，氯离子传输能力随应力水平和时间的增加而增强。在高压缩和弯曲应力水平下，由于微裂纹随时间的形核和扩展造成损伤，徐变对RAC试件中氯离子的渗透性有显著影响。显然，砂浆开裂对混凝土中氯离子传输的影响比界面过渡区（ITZ）开裂的影响更大。
