粉煤灰掺量对再生混凝土力学性能和抗冻性的影响研究

Influence of Fly Ash Content on Mechanical Properties and Frost Resistance of Recycled Concrete

研究粉煤灰掺量、再生粗骨料取代率对再生混凝土抗压强度和抗折强度的影响,并对再生混凝土在不同冻融循环次数下的抗压强度和质量损失率进行了研究。结果表明:随着粉煤灰掺量的增加,再生混凝土抗压强度呈先增大后降低的趋势,当粉煤灰掺量为15%,再生粗骨料取代率为30%时,再生混凝土的抗压强度达到最大;粉煤灰掺量对抗折强度提高幅度较小;在冻融循环低于50次时,试块抗压强度下降速度较缓,此后下降速度加快,当冻融循环达到150次时,强度损失最大;再生粗骨料取代率对试块的抗冻性影响高于粉煤灰掺量。建立了考虑再生粗骨料取代率、粉煤灰掺量因素的冻融循环作用下再生混凝土抗压强度指数衰减规律预测模型。

Effect of fly ash admixture amount and recycled coarse aggregate substitution rate on the flexural strength and compressive strength of recycled concrete was studied,and compressive strength and mass loss rate of recycled concrete under 4 stages of freeze-thaw cycle were measured. It＇s shown that with the increase of fly ash content,the compressive strength of recycled concrete firstly increases and then decreases. The maximum compressive strength of recycled concrete is reached when the fly ash content is15% and the replacement ratio of recycled coarse aggregate is 30%. The flexural strength is increased,but lightly when the fly ash is included. When the freeze-thaw cycle is lower than 50 times,the compressive strength of the test block decreases slowly,and then the rate of decline is accelerated. When the freeze-thaw cycle reaches 150 times,the strength loss is the largest. The substitution rate of recycled coarse aggregate is higher than that of fly ash content. The prediction model of compressive strength of recycled concrete under freezing and thawing cycles is established considering the replacement ratio of recycled coarse aggregate and the amount of fly ash.