掺合料裹骨料工艺对再生骨料混凝土性能的影响

采用一种掺合料裹骨料搅拌工艺,在水泥裹骨料工艺基础上,进一步改善再生骨料-水泥石界面过渡区,提高再生混凝土性能,研究了搅拌工艺、新拌混凝土坍落度、掺合料品种对再生混凝土强度和抗氯离子渗透性的影响.结果表明,采用掺合料裹骨料工艺,可在水泥裹骨料工艺基础上进一步大幅度提高早龄期强度和抗氯离子渗透性能,对后期强度和抗氯离子渗透性也有提高,但幅度较小;提高新拌混凝土坍落度有助于提高强度,但对抗氯离子渗透性能略有影响,采用掺合料裹骨料工艺可减小坍落度对再生混凝土性能的影响;采用矿渣掺合料更有助于提高再生混凝土强度和抗氯离子渗透性能.

Effect of surface coating of aggregate by admixture on properties of recycled aggregate concrete

A novel mixing method was applied to realize surface coating of aggregate by admixture for further improving microstructure of interfacial transition zone(ITZ) and properties of recycled aggregate concrete(RAC).Effects of mixing methods,slump of the fresh concrete and coating by various admixtures on compressive strength and chloride ions penetration resistance of RAC were investigated.The results show that compressive strength and chloride ions penetration resistance of the concrete can be further enhanced through surface coating of admixture around the aggregates during mixing,as compared to that by the surface-coating-by-cement mixing method,especially at early ages.Increasing slump of the fresh concrete helps enhance compressive strength but weakly harm the chloride ions penetration resistance of the hardened RAC for both mixing methods.However,the negative effects of increasing slump on properties of RAC can be reduced by using the surface-coating-by-admixture mixing method.Using slag as admixture helps improving properties of RAC as compared by using fly ash.