800 m超长盘管泵送前后混凝土性能变化及其机理

Change of Concrete Performance and Its Mechanism before and after 800 m Super-long Coil Pumping

为研究实际泵送条件下混凝土的性能变化,测试了800 m超长盘管泵送前后C30、C60及C80混凝土的工作性能、力学性能及收缩性能,并利用压汞仪(MIP)、扫描电镜(SEM)及化学结合水等微观测试方法分析了泵送前后混凝土的微观结构及特性变化.结果表明:与泵送前相比,泵送后混凝土的工作性能下降、含气量增加、孔隙率增加,对混凝土的力学性能造成不利影响,但泵送后混凝土的化学结合水含量增加,胶凝材料水化度提升,益于混凝土强度发展,因而出泵前后混凝土抗压强度无明显变化;混凝土含气量的增加使得浆体中的孔向着较大毛细孔发展,弱化了泵送后混凝土的干燥收缩现象.

In order to study the effect of actual pumping on concrete performance,the workability,mechanical and shrinkage properties of C30,C60 and C80 concrete before and after 800 m super-long coil pumping were tested. The mercury intrusion porosimetry(MIP),scanning electron microscops(SEM)and chemically bound water and other microscopic test methods were used to analyze the changes in the microstructure and characteristics of the concrete before and after pumping. The results show that the workability of concrete decreases and the air content increases after pumping. The porosity of the mortars increases after pumping,results in adversely affecting the mechanical properties of the concrete. However,after the concrete is pumped,the chemically bound water increases and the hydration degree of the cementitious material increases,favors to the development of concrete strength. Therefore,the compressive strength of concrete after pumping is basically the same as before pumping. In addition,increase in air content after the concrete is pumped makes the pore diameter of the mortars larger,and weakens the drying shrinkage of the concrete.