粗骨料全替代再生混凝土的孔结构与力学性能分析

Analysis of Pore Structure and Mechanical Properties of Recycled Concrete with Full Replacement of Coarse Aggregate

为提高建筑垃圾利用率,采用两种来源不同且性质差异较大的再生粗骨料来制备满足工程需求的大流动性再生混凝土,在粗骨料全替代下研究不同品质再生粗骨料及不同矿物掺合料对再生混凝土工作性、力学性能及孔结构的影响,并确定其最优配合比。结果表明:与天然粗骨料相比,再生粗骨料内部含有较多裂缝,掺入粉煤灰和矿粉后,部分颗粒填充于骨料内部缝隙之间,有利于改善混凝土和易性,但不利于混凝土强度发展。孔结构分析表明气泡体积占比越小,有益气泡占比越大,对混凝土越有利。综合考虑各项性能,推荐最优配合比为双掺粉煤灰10%(质量分数,下同)、矿粉5%,此时再生混凝土工作性满足大流动性的要求,强度满足C30强度等级要求。

In order to improve the utilization rate of construction waste,large liquidity recycled concrete was prepared using recycled coarse aggregates with significant differences in properties from two sources to meet engineering needs.The effects of different quality recycled coarse aggregates and mineral admixtures on workability,mechanical properties and pore structure of recycled concrete were studied under the full replacement of coarse aggregates,and the optimal ratio was determined.The results show that recycled coarse aggregates contain more cracks than natural aggregates.After adding fly ash and mineral powder,some particles fill the gaps inside aggregates,which is beneficial for improving workability of concrete,but not conducive to development of concrete strength.The analysis of pore structure shows that the smaller percentage of bubble volume and the larger percentage of beneficial bubbles,the more favorable it is for concrete.Taking into account various performance factors,it is recommended that the optimal mix ratio is 10%(mass fraction,the same below)fly ash and 5%mineral powder.The workability of recycled concrete meets the requirements of large liquidity and the strength meets the requirements of C30 strength grade.