To explore the influence of manufactured sand content on the flexural performance of self-compacting lightweight aggregate concrete (SCLC) beams, five SCLC beams with different manufactured sand dosage have been designed and fabricated for four-point bending tests. The workability and mechanical properties of the concrete mixture of each test beam are tested. It is observed that with the increase in the manufactured sand content, the workability of SCLC meets the standard requirements, and the mechanical properties are improved. The load–deflection curve, crack distribution pattern, and average strain of section are obtained through the four-point bending tests. The results reveal that the bending process of each test beam can be divided into three stages: uncracked stage, working stage with cracks, and failure stage. The average strain of section conforms to the assumption of plane section, and the load–deflection curve of each test beam is basically similar. With the increase in the manufactured sand content, the SCLC beam specimens exhibit more secondary cracks and more uniform crack distribution. Under the same level of load before yield, the maximum crack width decreases. The ultimate bearing capacity becomes maximum when the content of manufactured sand is 80%, which is 6.62% higher than that of SCLC beam with entire river sand. The plasticity coefficient of the resistance moment of the section is fitted by the experimental value, and the calculated value of cracking moment is in good agreement with the experimental value. Using the calculation formula for the maximum crack width of lightweight aggregate concrete and the fitting formula for the inhomogeneity coefficient of steel strain, the maximum crack width of each test beam is determined, which is in good agreement with the experimental value. Based on the test results and the calculated flexural bearing capacity, the optimal dosage of manufactured sand of SCLC concrete is obtained to be 60–80%.

为了探究机制砂掺量对自密实轻骨料混凝土梁抗弯性能的影响，设计并制作了5根不同机制砂掺量的SCLC梁，并进行了四点弯曲试验。对各试验梁的混凝土拌合料的和易性和力学性能进行了测试。观察发现，随着机制砂含量的增加，SCLC的和易性满足标准要求，力学性能得到改善。通过四点弯曲试验获得荷载-挠度曲线、裂纹分布模式和截面平均应变。结果表明，各试验梁的弯曲过程可分为三个阶段：未裂纹阶段、有裂纹阶段和失效阶段。截面平均应变符合平面截面假设，各试验梁的荷载-挠度曲线基本相似。随着机制砂含量的增加，SCLC梁试件表现出更多的二次裂纹和更均匀的裂纹分布。在屈服前相同水平的载荷下，最大裂缝宽度减小。当机制砂含量为80%时极限承载力达到最大，比全河砂SCLC梁的极限承载力提高了6.62%。用试验值拟合了截面抗弯矩的塑性系数，开裂弯矩的计算值与试验值吻合较好。利用轻骨料混凝土最大裂缝宽度计算公式和钢筋应变不均匀系数拟合公式，确定了各试验梁的最大裂缝宽度，与试验值吻合较好。根据试验结果和计算的抗弯承载力，得出SCLC混凝土的最佳机制砂掺量为60%~80%。