机制砂钢筋混凝土梁受弯与受剪性能试验研究

为了从机制砂骨料的细观指标出发，研究机制砂混凝土梁的受弯与受剪性能，选取了天然砂和3种机制砂，对比了不同骨料的颗粒级配、细度模数、石粉含量、MB值等材性指标，利用图像分析处理技术获取不同骨料的形状参数，通过试验对比了不同细骨料混凝土的工作性能、抗压强度和体积稳定性能;分别设计了受弯和受剪天然砂及机制砂钢筋混凝土梁，通过荷载试验，比较不同细骨料混凝土梁的开裂荷载、挠度曲线和承载力等受力性能指标。研究结果表明：采用延性参数与圆度参数可以反映不同类型骨料间的颗粒形状差异，颗粒级配合理、形状参数良好的机制砂混凝土的强度和长期干缩性能可以达到甚至超过天然砂混凝土的，机制砂和天然砂钢筋混凝土梁的受弯、受剪破坏形态相似，承载力与其混凝土强度相关，可采用现行设计方法对机制砂混凝土梁进行承载力设计。天然砂钢筋混凝土梁抗裂能力略优于机制砂钢筋混凝土梁的，为此，采用现行开裂荷载计算方法会高估机制砂混凝土梁的开裂荷载，建议对机制砂钢筋混凝土梁的开裂荷载设计进行适度调整。

Experimental study on flexural and shear behaviors of reinforced concrete beams made with manufactured sands

In order to explain the macro flexural behavior and shear behavior of concrete beams made with manufactured sand from the meso-index of manufactured sands, natural sand and three kinds of manufactured sands were selected in this research. The material indexes of gradation, fineness modulus, powder content, MB value and so on were compared. The digital image process method was used to obtain the shape parameters of different aggregates. The concrete workability, compressive strength and shrinkage were studied and compared through experiment. Finally, the flexural and shear beams were designed and the static tests were conducted to compare the cracking load, deflection curve and ultimate strength of the beams made with different kinds of sand aggregates. The results show that the shape parameters of ellipse ratio and circularity can be used to separate different kinds of aggregates. The strength and long-term dry shrinkage performance of manufactured sand concrete with reasonable gradation and shape parameter can reach or even exceed that of concrete made with natural sand. The failure patterns of the beams made of manufactured sands and natural sands are very similar for both flexural and shear failure mechanism. The bearing capacity of the beams made with manufactured sands exhibits a positive correlation with the concrete strength. The current concrete design method can well meet the engineering requirement. However, the concrete made with natural sand has a higher cracking load than the concrete made with manufactured sand. The current calculation method overestimates the cracking load of the concrete beam made with manufactured sand. Therefore, the cracking load of reinforced concrete beam made with manufactured sand obtained by current calculation method needs to be adjusted accordingly.