矿物掺合料对再生混凝土抗氯离子渗透性研究

Research on Recycled Concrete Resistance to Penetration of Chloride Ion by Adding Mineral Admixtures

以掺加粉煤灰、硅灰、钢纤维、聚丙烯纤维等矿物掺合料为改性措施,制备C25、C30普通混凝土、再生混凝土和改性再生混凝土的圆柱体试件,直径（100±1）mm,高度（50±2）mm;分别通过快速氯离子（Cl-）迁移系数法（RCM法）测定无外荷载作用下40 dCl-渗透系数,研究了不同改性措施下再生混凝土的Cl-扩散系数.结果表明：未经改性处理的再生混凝土抗Cl-渗透性能差于普通混凝土,Cl-扩散系数相差较大;随着强度等级提高,普通混凝土、再生混凝土抗Cl-渗透性能均不同程度提高;粉煤灰和硅粉以1∶1的比例掺入再生混凝土,改性再生混凝土抗Cl-渗透性能较同强度等级再生混凝土有不同程度提高,但仍低于同强度等级普通混凝土;在掺入粉煤灰和硅粉的前提下,在0%-1.0%范围内,掺加钢纤维或聚丙烯纤维后,改性再生混凝土抗Cl-渗透性能较同强度等级再生混凝土有较大程度提高,且高于同强度等级普通混凝土;在此范围内,随着钢纤维或聚丙烯纤维掺量的增加,改性再生混凝土Cl-渗透系数不断降低;在掺入粉煤灰和硅粉的前提下,在0%-1.0%范围内,掺加聚丙烯纤维效果优于钢纤维.

The test begins with preparation of cylindrical specimens about 100±1mm in diameter and 50±2mm in height which are made of C25 normal concrete, C30 normal concrete, recycled concrete andmodified recycled concrete by adding some mineral admixtures such as fly ash, silicon ash, steel fiberand polypropylene fiber etc. as the modified measures. Then it measures Cl- permeability coefficients of40 days without external loads by RCM and studies Cl- diffusion coefficients of recycled concrete underdifferent modified measures. The results show that the resistance of unmodified recycled concrete to Clpermeabilityis poorer than that of normal concrete and there are pretty different Cl- diffusioncoefficients; the resistance of normal concrete and recycled concrete to Cl- permeability can beimproved with increase of strength grade; by adding fly ash and silicon ash in the proportion of 1：1 intorecycled concrete, the resistance of modified recycled concrete to Cl- permeability can be improved in comparison to recycled concrete of the same strength grade but is lower than that of normal concrete of the same strength grade; by adding steel fiber or polypropylene fiber within the range of 0~1.0% on the premise of mixing fly ash and silicon ash, the resistance of modified recycled concrete to Clpermeability can be improved a lot in comparison to recycled concrete of the same strength grade and is higher than that of normal concrete of the same strength grade; within the range, Cl- permeability coefficient of modified recycled concrete decreases rapidly as the amount of steel fiber or polypropylene fiber increases; adding polypropylene fiber is more effective than adding steel fiber within the range 0-1.0% on the premise of mixing fly ash and silicon ash.