【摘要】 研究了机制砂亚甲蓝(MB)值与石粉、粘土含量及粘土特性的关系,试验分析了机制砂MB值在0.35~2.5范围变化对新拌混凝土的工作性、塑性收缩开裂特性以及硬化混凝土的力学性能、干缩和耐久性的影响。结果表明,MB值与机制砂中的石粉含量无关,而与粘土含量成正比,同时发现MB值也显著受粘土液限指数的影响。随机制砂MB值的提高,新拌混凝土的工作性下降,硬化混凝土抗折强度和7 d抗压强度降低明显,对28 d抗压强度影响不大。同时,机制砂MB值的提高,增大了混凝土的塑性开裂程度和干缩,显著加快了混凝土的冻融破坏速度,轻微降低了混凝土的抗氯离子渗透性能。对混凝土性能不产生明显劣化的机制砂MB临界值约为1.4。更多还原

【Abstract】 The relationship between the methylene blue(MB) value of manufactured sand and limestone powder content,clay content and clay characteristics is studied.The effect of MB value of the sand within the range from 0.35 to 2.5 on the workability of fresh concrete and the characteristics of plastic shrinking crack and the mechanical property,dry shrinkage as well as the durability of the harden concrete are.The tested results show that the MB value has no correlation with the limestone powder content of the manufactured sand,and that it is in proportion to clay content.It is found that the MB value is also significantly influenced by the liquid limit index of clay.Along with the increase of MB value,the workability of the fresh concrete is decreased,the flexural strength and 7 d compressive strength of the harden concrete are lowered significantly,but no any effect on the 28 d compressive strength of the concrete.Moreover,the increment of MB value increases the plastic cracking extent and dry shrinkage,remarkably accelerates the freeze-thaw damage of the manufactured sand concrete,and slightly decreases the resistance to chloride ion permeability of the concrete.It is concluded that the critical MB value is 1.4,that could not significantly deteriorates the performances of the manufactured sand concrete.更多还原