粉煤灰-矿渣再生混凝土抗压强度及尺寸效应研究

Study on compressive strength and size effect of recycled concrete with fly ash-slag

以粉煤灰和矿渣掺入方式和掺量为变量,设计24组C30再生粗骨料混凝土,对再生混凝土的抗压强度进行了研究。试验结果表明,粉煤灰或矿渣单掺时,再生混凝土的抗压强度随矿物掺料的掺量增加呈现先上升后下降趋势,同等掺量下矿渣单掺优于粉煤灰单掺;双掺时保持粉煤灰或矿渣掺量20%不变,再生混凝土立方体和轴心抗压强度随另一种微细矿物掺量的增加同样呈现先上升后下降趋势,双掺较单掺方式对再生混凝土抗压强度的提升效果更佳,且再生混凝土的抗压强度存在明显的尺寸效应。单掺粉煤灰或矿渣时再生混凝土轴心抗压强度和立方体抗压强度换算系数随其掺量增加而增大,双掺则稳定保持在0.85±0.02。此外,论文还建立了不同微细矿物掺料条件下再生混凝土抗压强度换算系数的修正公式,验证结果表明公式预测误差较小。建议实际工程再生混凝土配制采用粉煤灰和矿渣双掺方式,且掺量控制在25%以内。

In this study,the mixing mode and content of fly ash and slag were set as variables,and 24 groups of C30 recycled coarse aggregate concrete(RAC) were designed.The compressive strength of RAC was studied.The experimental results show that when adding fly ash or slag independently,the compressive strength of RAC increased firstly and then decreased with the mineral powder content,and the improvement of compressive strength of RAC of slag was significantly better than that of fly ash at the same content.If one of them was kept at 20% when added together,the cubic and axial compressive strength increased firstly with the other mineral powder content and then declined with its increase.Moreover,the compressive strength of RAC was higher when fly ash and slag were added together than independently.The compressive strength of RAC had an obvious size effect.The strength conversion coefficient(η) of cubic and axial compressive strength of RAC increased with the growth of fly ash or slag content when adding independently,while kept stable at 0.85 ± 0.02 when adding together.A modified formula for η of RAC under different conditions of fine mineral admixtures was established,and the verification showed good agreement.Therefore,in actual engineering,the content of fly ash and slag is recommended mixed and its content is suggested within 25%.