摘要
机制砂中较高的石粉含量会影响新拌混凝土的工作性能以及硬化混凝土的力学性能和耐久性能。本文研究不同砂体系中高石粉含量对不同强度等级混凝土和易性、含气量、抗压强度、碳化深度、抗渗以及收缩性能的影响。结果表明:当天然砂和机制砂混合比例为7∶3时,混合砂的孔隙率最低,为37%;高石粉含量显著增加了高强度等级混凝土的粘度,不利于混凝土的泵送浇筑;通过破碎得到的机制砂,颗粒边缘碎化,相对于天然砂体系混凝土的气泡保有性能差别较大,含气量经时损失较大;混合砂体系混凝土早期抗压强度优于机制砂体系,与天然砂体系相差不大,且混合砂体系混凝土的后期抗压强度较大,这也表明石粉能更好地填充至体系中,填充效应显著;高石粉含量增加了混凝土碳化的发生概率,机制砂体系混凝土不同龄期的碳化深度最大,混合砂体系混凝土的碳化深度与天然砂体系基本保持一致;混合砂体系混凝土的渗水高度最小,其抗渗性能最优;混合砂体系混凝土的早期收缩低于机制砂体系,与天然砂体系保持一致。
The higher content of stone powder in machine-made sand can affect the workability of fresh concrete and the mechanical and durability properties of hardened concrete.This article studies the effects of high stone powder content in different sand systerms on the workability,air content,compressive strength,carbonation depth,impermeability,and shrinkage performance of different strength grades of concrete.The results show that when the mixing ratio of natural sand and machine-made sand is 7:3,the porosity of the mixed sand is the lowest,at 37%;the high content of stone powder significantly increases the viscosity of high-strength grade concrete,which is not conducive to the pumping and pouring of concrete;the machinemade sand obtained through crushing has fragmented particle edges,resulting in a significant difference in bubble retention performance compared to natural sand,and a considerable loss of gas content over time;the early compressive strength of concrete prepared with mixed sand is better than that of pure machine-made sand system concrete,and is not significantly different from natural sand.Moreover,the later compressive strength of concrete prepared with a mixed sand system is larger,indicating that stone powder can be better filled into the system and the filling effect is significant;the high content of stone powder increases the probability of concrete carbonation.The carbonation depth of a pure machine-made sand system is the highest at different ages,while the carbonation depth of mixed sand system concrete is consistent with that of the natural sand system;the infiltration height of the mixed sand system is the smallest,and the impermeability performance of concrete is the best;the early shrinkage of concrete in the mixed sand system is lower than that in the pure machine-made sand system,which is consistent with the natural sand system.
出处
《混凝土世界》
2024年第5期36-42,共7页
China Concrete
关键词
高石粉含量
机制砂
天然砂
工作性能
力学性能
耐久性能
High stone powder content
machine-made sand
natural sand
working performance
mechanical properties
durability performance
