再生骨料混凝土早期强度的影响因素研究

Study on influencing factors of early strength of recycled aggregate concrete

系统分析服役20余年的废弃混凝土破碎制作再生骨料大比例取代天然骨料制作再生混凝土的早期强度影响因素。选取再生骨料替代率、砂率、胶凝材料用量和养护方式四个因素,通过正交试验设计,测试6、12、24 h的抗压强度。试验结果的极差和方差分析显示:再生骨料替代率对早期抗压强度影响显著,替代率高则强度低;砂率和胶凝材料用量会影响早期强度,但影响并不显著;养护方式可以显著影响再生骨料混凝土的早期强度,水浴养护最利于早期强度的产生,但影响程度会随养护时间的延长而逐渐弱化,微观试验分析揭示出弱化机理。优化配合比后的再生骨料混凝土,6 h满足脱模要求,24 h达到堆砌标准,可以明显提高生产效率。

The large proportion of natural aggregates are replaced with the recycled aggregates which made of the waste concrete that in service for more than 20 years,and the early strength of recycled concrete are analyzed systematically.The factor of RCA replacement rate,sand rate,amount of cementing material and curing method are selected for orthogonal test design,the compress strength of the test results of 6,12 and 24 h are obtained.The results of range and variance analysis showed that the replacement rate of recycled aggregate has a significant effect on the early compressive strength,the higher the substitution rate the lower the strength.The sand rate and cementitious material dosage can affect the early strength,but it is not significant.The curing method can affect the early strength of recycled aggregate concrete significantly,and the early strength is most conducive when water bath curing is adopted,but this effect of water bath curing will gradually weaken with the extension of curing time,and the weakening mechanism is revealed by microscopic test analysis.The optimized mix ratio of recycled aggregate concrete can meet the demolding requirement within 6 h and the stacking standard within 24 h,which can improve the production efficiency significantly.