硅灰对高石粉含量机制砂制备混凝土的影响

摘要

In view of natural sand becoming scarce and the high stone powder content in manufactured sand resulting problems like poor workability and pumpability of concrete prepared,influence of silica fume on workability,mechanical and volume stability of manufactured sand concrete is studied,and the mechanism of the silica fume is analyzed.The results show that suitable amount of silica fume can improve the workability and stability of concrete,solve the high viscosity and bleeding of concrete caused by high stone powder content in manufactured sand,improve the slurry microstructure,and enhance the mechanical and durability performance of concrete,and its 28d dry shrinkage rate is below 400× 10-6.When stone powder content in manufactured sand is around 10％ and silica fume content is from 6％ to 9％,the prepared C50 manufactured sand concrete has good uniformity,and the slurry viscosity value is around 2.5 Pa.s,and bleeding rate is almost zero.Its practical application is satisfactory.%针对天然砂日渐匮乏,而机制砂中石粉含量偏高所制备的混凝土工作性、泵送性差等问题,研究硅灰对机制砂混凝土的工作性、力学和体积稳定性的影响,并分析硅灰的作用机理.结果表明:适量硅灰可以增加混凝土工作性和稳定性,解决机制砂高石粉含量引起的混凝土黏度大和泌水问题,改善浆体微观形貌,提高混凝土力学和耐久性能,且28 d干燥收缩率＜400x 10-.机制砂中石粉含量为10％左右时,硅灰掺量6％ ～ 9％,制备的C50机制砂混凝土匀质性好,浆体旋转黏度约2.5 Pa·s,泌水率为0,工程应用效果良好.