A Study on method of controlling dry shrinkage crack of Recycled Aggregate Concrete

再生骨料作为骨料资源的有效性和适用性已被许多研究者所证实。另一方面，日本从未采用含有这种类型骨料的再生骨料混凝土作为结构混凝土的实际应用。为了促进再生骨料混凝土的实际应用，再生骨料的质量与再生骨料混凝土性能之间的关系是亟待解决的问题。研究了再生骨料混凝土干缩裂缝的控制方法。再生骨料混凝土中再生骨料吸水率大，容易出现干缩裂缝。结果表明：(1)用普通骨料替代再生骨料后，再生骨料混凝土的干缩率减小，干缩裂缝也随之减小。(2)在钢筋混凝土墙体配筋率相同的情况下，双配筋比单配筋更能减少干缩裂缝。(3)再生骨料混凝土由于其杨氏模量低、干收缩大，使钢筋混凝土楼盖挠度增大。

The availability and applicability of recycled aggregate as aggregate resources have already proved by many researchers. The other hand, practical application of recycled aggregate concrete containing this type of aggregate for structural concrete has never adopted in Japan.To promote practical application of recycled aggregate concrete, there are many points that must be solved concerning the correlation between qualities of recycled aggregate and properties of recycled aggregate concrete.In this study, the method of controlling dry shrinkage crack of recycled aggregate concrete was investigated. Since the rate of water absorption of recycled aggregate in recycled aggregate concrete is large, dry shrinkage cracks tend to occur. The results are summarized as follows : (1)The drying shrinkage of recycled aggregate concrete becomes small by replace the recycled aggregate with the normal aggregate, and the drying shrinkage cracks can be reduced along with it. (2) In case of the same reinforcement ratio in reinforced concrete wall, the double reinforcement is better than single reinforcement to reduce the dry shrinkage cracks. (3) The deflextion of reinforced concrete floor slab with recycled aggregates increases because of the recycled aggregate concrete with low Young's modulus and large dry shrinkage.