公路工程

为研究机制砂材料特性对机制砂混凝土强度与工作性能的影响，分别制备了细砂(FS)、中砂(MS)和粗砂(CS)的混凝土配合比，进行了混凝土砌块强度试验和胶砂流动性试验，通过调节水灰比(0.29～0.37)分析强度和流动性的变化规律；随后，用特制筛筛出机制砂的片状颗粒，制备不同片状颗粒含量(0%～30%)的混凝土，研究片状颗粒含量对混凝土强度和流动性的影响；最后，进行了石粉含量(3%～12%)对强度与和易性影响的试验。研究表明，与CS和FS相比，MS因为较低的空隙率和较高的密度与细度，有助于生产高密实度且均匀的混合物，在实际工程中应尽可能使用中砂，且水灰比应>0.31,片状颗粒含量应≤5%,这归因于片状颗粒易使内部缺陷增多从而加大比表面积与空隙率。在不添加粉煤灰的情况下，石粉含量增加提高了强度，这是由于石粉通过填充效应优化了颗粒级配、降低空隙率，并加速水化作用(生成C-S-H及碳铝酸钙),但随着粉煤灰含量增加，石粉对强度的增益效果降低。当石粉含量≤9%时，掺入矿渣粉提高了混凝土的强度，但石粉含量过高反而对强度产生不利影响。综上，成功制备C60机制砂混凝土关键在于选用中砂(细度模数≈2.9)、控制水灰比>0.31、限制片状颗粒含量≤5%,以及优化石粉含量与掺合料(粉煤灰/矿渣粉)的协同配比。研究为C60等高标号机制砂混凝土应用提供了科学试验依据。

To investigate the influence of manufactured sand characteristics on the strength and workability of concrete, concrete mix proportions were prepared using Fine Sand(FS), Medium Sand(MS), and Coarse Sand(CS).Concrete block strength tests and mortar fluidity tests were conducted, analyzing the variation patterns of strength and fluidity by adjusting the water-cement ratio(0.29～0.37).Subsequently, flaky particles in manufactured sand were sieved using a specialized screen, and concrete with different flaky particle contents(0%～30%) was prepared to study their effect on strength and fluidity. Finally, the influence of stone powder content(3%～12%) on strength and workability was examined.The study indicates that, compared to CS and FS, MS exhibits lower void ratio, higher density, and finer gradation, contributing to a denser and more homogeneous mixture. Hence, medium sand should be prioritized in practical engineering applications, with a water-cement ratio exceeding 0.31 and flaky particle content limited to≤5%. This is attributed to flaky particles increasing internal defects, thereby enlarging specific surface area and void ratio. Without fly ash, increasing stone powder content significantly enhances strength due to its filling effect, optimizing particle gradation, reducing voids, and accelerating hydration(forming C-S-H and calcium carboaluminate).However, the strength-enhancing effect of stone powder diminishes as fly ash content rises. When stone powder content is≤9%, the simultaneous incorporation of slag powder improves strength, but excessive stone powder adversely affects performance.In conclusion, the key to successfully preparing C60 manufactured sand concrete lies in selecting medium sand(fineness modulus≈2.9), controlling the water-cement ratio>0.31, limiting flaky particle content to≤5%, and optimizing the synergistic ratio of stone powder and supplementary cementitious materials(fly ash/slag powder).This study provides experimental evidence for the application of high-strength manufactured sand concrete, such as C60.