粉煤灰掺量对全再生自密实混凝土工作性能与力学性能的影响

Effect of Fly Ash Content on Workability and Mechanical Properties of Fully Recycled Self-Compacting Concrete

本文使用再生粗骨料全部替代天然粗骨料,用粉煤灰分别替代20%、30%、40%、50%和70%(质量分数)水泥,制备了不同水胶比(0.36、0.40和0.45)的全再生自密实混凝土,通过抗折强度试验和抗压强度试验,分析了粉煤灰掺量和水胶比对全再生自密实混凝土性能的影响规律,得到了粉煤灰的合理掺量,提出了适用于全再生自密实混凝土抗折强度的计算公式。结果表明:当粉煤灰掺量由20%增至40%时,所有全再生自密实混凝土拌合物的坍落扩展度呈先增加后降低趋势,且均表现出良好的间隙通过能力,但混凝土拌合物扩展时间T_(500)受粉煤灰的影响不显著;随着粉煤灰掺量增加,全再生自密实混凝土的抗压强度和抗折强度均呈先增加后降低趋势,抗折强度受粉煤灰掺量的影响程度要高于抗压强度;全再生自密实混凝土抗压强度和抗折强度受水胶比的影响程度相同;综合粉煤灰掺量对全再生自密实混凝土工作性能和力学性能的影响,建议粉煤灰对水泥的取代率为30%。

In this paper,recycled coarse aggregate was used to replace natural coarse aggregate,and fly ash was used to replace 20%,30%,40%,50%and 70%(mass fraction)of cement,respectively.The full recycled self-compacting concrete with different water-binder ratios(0.36,0.40 and 0.45)was prepared.Through flexural strength and compressive strength tests,the effects of fly ash content and water-binder ratio on the performance of full recycled self-compacting concrete were analyzed.The reasonable content of fly ash was obtained,and the calculation formula suitable for flexural strength of full recycled self-compacting concrete was proposed.The results show that when fly ash content increases from 20% to 40%,the slump expansion of all recycled self-compacting concrete mixtures increases first and then decreases,and all of them show good clearance capacity,but the expansion time T_(500) of concrete mixture is not significantly affected by fly ash.With the increase of fly ash content,the compressive strength and flexural strength of fully recycled self-compacting concrete increase first and then decrease,and the flexural strength is more affected by fly ash content than compressive strength.The compressive strength and flexural strength of fully recycled self-compacting concrete are affected by water-binder ratio to the same extent.Based on the effect of fly ash content on the workability and mechanical properties of fully recycled self-compacting concrete,it is suggested that the replacement rate of fly ash to cement is 30%.