Influences of Coarse Aggregate Replacement Ratios on High-Temperature Performance of Recycled Concrete with Manufactured Sand
To explore the influences of different coarse aggregate replacement ratios on the high-temperature performance of recycled concrete with manufactured sand(RCM),RCM specimens were prepared with varying coarse aggregate replacement ratios(0%,20%,40%,60%,80%,100%,mass fraction).The surface morphology,mass loss rate,compressive strength,load-deformation curve,and microscopic morphology of RCM were investigated after exposure to high temperatures.Results indicate that the RCM performs well in high-temperature tests below 600 ℃ when the coarse aggregate replacement ratio is between 40%and 60%.At 200 ℃,the specimens in each group show minimal morphological changes,small mass loss rate,and a slight increase in compressive strength.At 400 ℃,cracks begin to appear on the surface of the specimens,with mass loss rate ranging from 4.35%to 6.47%,and compressive strength starts to decline.At this point,the coarse aggregate replacement ratio has a minor impact.At 600 ℃,significant changes in surface morphology are observed,with mass loss rate increasing to 6.42%~8.70%,and compressive strength eventually decreasing to around 80%of the baseline strength.Specimens with coarse aggregate replacement ratio of 40%~60%perform well under these conditions.At 800 ℃,the surface morphology of specimens in all groups intensifies further.The impact becomes particularly pronounced for coarse aggregate replacement ratio exceeding 60%.Simultaneously,various performance parameters indicate that the concrete has experienced a complete loss of effectiveness at this temperature.