掺粉煤灰再生混凝土反向湿度响应规律与预测模型研究

Study on Reverse Humidity Response Law and Forecast Model of Recycled Concrete Mixed with Fly Ash

在模拟人工气候环境条件下,开展了再生粗骨料取代率和粉煤灰掺量对再生混凝土力学性能及其在干燥过程中反向湿度响应的影响研究。基于传质学的相关理论,提出了粉煤灰再生混凝土反向湿度响应的预测模型并验证了其可行性。试验结果表明:混凝土28 d抗压强度随着再生粗骨料取代率和粉煤灰掺量的增大均呈现先增大后减小的趋势;粉煤灰掺量一定时,再生粗骨料取代率为25%的混凝土抗压强度达到最大;再生粗骨料取代率一定时,粉煤灰掺量(质量分数)为10%的抗压强度最大;在同一反向湿度响应时刻,再生粗骨料取代率为25%时混凝土反向湿度响应速率最低,取代率为0%,50%,75%,100%的混凝土湿度响应速率依次增大;粉煤灰掺量为10%的混凝土反向湿度响应速率最低,掺量为0%,20%和30%的湿度响应速率依次增大;在反向湿度响应的早期,2种影响因素对混凝土的反向响应速率影响更大;随着湿度响应的进行,影响逐渐减小,且随着粉煤灰掺量的增大,不同时间段的反向湿度响应速率差距逐渐增大。

The effects of the replacement rate of recycled coarse aggregate and fly ash content on the mechanical properties of recycled concrete and its reverse humidity response in the drying process were studied under simulated artificial climate conditions.Based on the relevant theories of mass transfer,a prediction model of the reverse humidity response of fly ash recycled concrete was proposed and its feasibility was verified.The test results show that the 28 d compressive strength of concrete increases firstly and then decreases with the increase of the replacement rate of recycled coarse aggregate and the content of fly ash.When the fly ash content is constant,the compressive strength of concrete with the replacement rate of recycled coarse aggregate of 25%reaches the maximum.When the replacement rate of recycled coarse aggregate is constant,the compressive strength of fly ash content of 10%is the maximum.At the same time of reverse humidity response,when the replacement rate of recycled coarse aggregate is 25%,the concrete reverse humidity response rate is the lowest,and the replacement rate of 0%,50%,75%and 100%increases successively.Concrete with fly ash content of 10%has the lowest humidity response rate,while those with content of 0%,20%and 30%increase in turn.In the early stage of the reverse humidity response,the two influencing factors have greater influence on the reverse response rate of concrete.With the development of humidity response,the influence is gradually smaller.In addition,with the increase of fly ash content,the difference of the reverse humidity response rate in different time periods gradually increases.