复合改性再生粗骨料对混凝土性能的影响

Effect of composite modified recycled coarse aggregates on performance of concrete

通过加热和颗粒整形对再生粗骨料进行了复合改性处理,对比分析了未改性和改性再生粗骨料的性能,研究了再生粗骨料的掺量对混凝土工作性和抗压强度的影响,优选出了最佳再生粗骨料类型和掺量,并在此基础上,研究了粉煤灰掺量对再生混凝土耐久性能的影响。结果表明:经过复合改性处理后,再生粗骨料的性能得到了强化。随着再生粗骨料掺量的增加,混凝土的坍落度、扩展度和抗压强度基本呈减小趋势;掺改性再生粗骨料混凝土(MRAC)的工作性和抗压强度整体上比掺未改性再生粗骨料混凝土(RAC)的好;综合考虑工作性和抗压强度,改性再生粗骨料的最佳掺量为30%;随着粉煤灰掺量的增加,MRAC的氯离子迁移系数和碳化深度均先减小后增大,推荐粉煤灰掺量为20%~30%。

The composite modification treatment of recycled coarse aggregate was carried out through heating and particle shaping,and the performance of unmodified and modified recycled coarse aggregate was compared and analyzed.The influence of the content of recycled coarse aggregate on the workability and compressive strength of concrete was studied,and the optimal type and content of recycled coarse aggregate were selected.On this basis,the effect of fly ash content on the durability of recycled concrete was studied.The results show that the performance of recycled coarse aggregate has been strengthened after composite modification.With the increase of recycled coarse aggregate content,the slump,slump-flow and compressive strength of concrete show a decreasing trend generally.The workability and compressive strength of modified recycled coarse aggregate concrete(MRAC)are generally better than those of unmodified recycled coarse aggregate concrete(RAC).Considering workability and compressive strength comprehensively,the optimal content of modified recycled coarse aggregate is 30%.With the increase of fly ash content,the chloride ion migration coefficient and carbonization depth of MRAC first decrease and then increase,and the recommended fly ash content is 20%~30%.