机制砂混凝土强度和工作性的正交法试验研究

纯机制砂混凝土的工作性和力学性能较差,而机制砂和天然细河砂复合配置是改善机制砂混凝土性能的一种普遍方法。文章通过机制砂混凝土四因素、四水平的正交法配合比试验,研究了机制砂掺量、砂率、石粉掺量和水灰比对机制砂混凝土强度、工作性的影响规律。结果表明:机制砂掺量对混凝土的强度和拌合物工作性影响显著,仅次于水灰比;以机制砂替代部分天然河砂可以提高混凝土的强度性能,机制砂掺量在33%~50%时,抗压强度和劈裂抗拉强度均较为理想,掺量超过80%以后,强度将低于纯天然砂混凝土;随着机制砂掺量的增大,拌合物工作性逐渐变差;石粉等量替代水泥在20%以内对抗压强度和劈裂抗拉强度无显著影响,而对工作性的影响显著;石粉的掺入明显增大了减水剂的用量;C35机制砂混凝土配合比的最佳组合是水灰比为0.45、机制砂掺量为50%、石粉含量为10%、砂率为41%、减水剂为1.5%。

Orthogonal experimental research on the strength and workability of machine-made sand concrete

An orthogonal experimental design method involving four factors and four factor levels is adopted for the mix design of machine-made sand concrete（ MSC）. The effect of each factor level on mix proportion of MSC and the difference between each factor levels were analyzed. The influence and mechanism of different experimental factor on the strength and workability of MSC,which includes percentage of machine-made sand and stone power,water-binder ratio,and sand percentage,was studied and compared with normal concrete. The experimental results indicate that the percentage of machine-made sand is the second important to strength and workability of MSC,only less than water-binder ratio. It can improve the strength of concrete to use machine-made to replace some nature sand . The best replacement rate is 33% -50%. But machine-made sand is adverse to the workability of concrete mixture. Stone power has no significant effect to strength when it is less than 20%,but it has significant effect to workability of concrete mixture. With the increase of stone power,the consuming amount of water reducer increases significantly. The best mix proportion of C35 in the experiment is that water-binder ratio is 0 . 45 ,percentage of machine-made sand is 50%,percentage of stone power is 10%,sand percentage is 41%,and water reducer is 1 . 5%.