凝灰岩机制砂混凝土性能及开裂风险评估

为提高凝灰岩机制砂混凝土的抗开裂性能,以机制砂掺配比例和石粉含量为主要影响因素,提出了基于钢环约束试验的混凝土开裂风险量化评估方法。同时,对凝灰岩机制砂混凝土的工作性能、力学性能、抗渗性能以及抗硫酸盐侵蚀性能进行了系统研究。试验结果表明:对于全机制砂混凝土,在5%石粉含量（质量分数）时其工作性和强度最佳；随着石粉含量的增加,抗硫酸盐侵蚀性能、抗渗性能逐渐降低,且干缩和开裂的可能性增大。对于天然砂与机制砂混掺的混凝土,随着天然砂掺配比例的增大,混凝土的力学性能逐渐降低；在30%天然砂质量掺配比例下,具有较好的抗硫酸盐侵蚀性能、抗渗性能。全机制砂混凝土虽然在工作性方面不如全天然砂混凝土,但在强度和抗裂性能上都更优异,用机制砂去取代天然砂能得到更好的效益,但同时应当严格控制石粉含量的限值(质量分数不宜大于7%)。30%天然砂质量掺配比例下,天然砂与凝灰岩机制砂混合使用时,混凝土综合性能最佳。

Quantitative assessment on performance and cracking potential of tuff manufactured sand concrete

In order to improve the anti-cracking performance of tuff manufactured sand concrete, the mixing ratio of manufactured sand and stone powder content were taken as the main influencing factors, and the quantitative evaluation method of concrete cracking risk based on tubular cracking test was proposed. At the same time, the working performance, mechanical properties, impermeability and sulfate corrosion resistance of tuff manufactured sand concrete were systematically studied. The test results indicated that the workability and strength of all machine-made sand concrete were the best when the content of stone powder is 5%(mass fraction). The sulfate resistance and impermeability gradually were decreased with the increase of stone powder content, and the possibility of dry shrinkage and cracking were greater. For the concrete mixed with natural sand and manufactured sand, the mechanical properties of concrete decreased gradually with the increase of the proportion of natural sand; Under the proportion of 30% natural sand, it has good sulfate resistance and permeability resistance. Although the fully manufactured sand concrete is not as good as the natural sand concrete in terms of workability, it is superior in strength and crack resistance. Using manufactured sand to replace natural sand can get better benefits, but at the same time, the limit of stone powder content should be strictly controlled (the mass fraction not more than 7%). When natural sand and tuff machine-made sand are mixed, the comprehensive performance of concrete is the best under the mixing ratio of 30% natural sand.