沙漠砂+机制砂混凝土力学性能及碳排放研究

当前，机制砂是代替天然河砂最普遍的材料，但机制砂存在级配不均匀、石粉含量过高、生产过程消耗能源和污染环境等问题。该文结合我国西部地区沙漠砂资源丰富的情况，开展了沙漠砂+机制砂混凝土(Desert sand + Machine-made sand Concrete, DMC)的力学性能试验，分析了不同沙漠砂替代率对混凝土强度和弹性模量的影响规律：DMC的强度与弹性模量随龄期逐渐增长，养护14d和28d时DMC轴心抗压强度随着沙漠砂替代率的增加呈现出先增大后减小的趋势，当沙漠砂替代率为20%时达到峰值。试验发现，DMC抗压强度受沙漠砂替代率的影响要大于弹性模量的影响。基于混凝土可压缩堆积理论，考虑沙漠砂和机制砂混合后堆积密度的变化及机制砂与沙漠砂在外观几何形状上的差异，并将混凝土二元混合料堆积模型扩展到细骨料堆积物理参数的分析中，建立了DMC抗压强度预测模型，模型精度较高。通过案例分析，在保证车站结构材料具有较好的力学性能前提下，当采用20%DMC时，由于减少了细骨料中机制砂的使用，案例的材料碳排放较低。

Study on mechanical properties and carbon emissions of desert sand and machine-made sand concrete

Nowadays, machine-made sand is the most common material of replacing river sand, but machine-made sand has some problems including uneven gradation, excessively high stone powder content, energy consumption during production and environmental pollution. In view of the abundant desert sand resources in the western region of China, the mechanical test on Desert sand and Machine-made sand Concrete (DMC) was carried out here, and the influences of different desert sand replacement rates on the strength and elastic modulus of concrete were analyzed. The strength and elastic modulus of DMC gradually increased with its age, and the axial compressive strength of DMC at 14 and 28 days of curing showed a trend of increasing at first and then decreasing with the increase of desert sand replacement rate, with the peak value of the trend corresponding to the desert sand replacement rate of 20%. It was found experimentally that the desert sand replacement rate had a greater influence on the compressive strength of DMC than the elastic modulus of DMC. Based on the compressible bulk theory of concrete and considering the changes in the bulk density of desert sand and machine-made sand as well as the difference in geometric appearance between machine-made sand and desert sand, the concrete binary mixture bulk model was extended to the physical parameters of fine aggregate bulk, and the prediction model of DMC compressive strength with good model accuracy was established. Through case study, on the premise of ensuring that the station structural material had good mechanical properties, when 20% of DMC was used, the carbon emissions studied were relatively low due to the reduced use of machine-made sand for fine aggregate.