振动搅拌对复合胶凝材料混凝土性能的影响

Effect of vibratory mixing on properties of composite cementitious concrete

为研究振动搅拌对C50复合胶凝材料预制梁混凝土性能的影响,采用正交试验优化得到了混凝土最佳配合比,在最佳配合比下,对不同振动搅拌时间下混凝土的工作性、抗压强度和弹性模量进行了测试,并结合XRD、SEM分析了振动搅拌对混凝土力学性能的影响机理。结果表明:通过正交试验得到混凝土的最佳配合比为m_(水泥)∶m_(矿粉)∶m_(粉煤灰)∶m_(硅灰)∶m_(砂)∶m5~10 mm_(碎石)∶m10~20 mm_(碎石)∶m水∶m_(减水剂)=369∶27∶40.5∶13.5∶775∶214∶857∶144∶5.4;振动搅拌会使混凝土的流动性有所下降,当振动搅拌时间为90 s时,混凝土的出机坍落度和扩展度下降幅度最小;随着振动搅拌时间的增加,混凝土的抗压强度和弹性模量均呈先增加后降低的趋势,当振动搅拌时间为90 s时,混凝土的抗压强度和弹性模量达到最大;振动搅拌加快了水泥的水化速率,促进了C-S-H凝胶、Ca(OH)2晶体等水化产物的生成,水化产物能更充分地填充于混凝土界面过渡区的孔隙和裂缝处,增加了界面过渡区结构的致密性,从而提高了混凝土的强度。

To study the effect of vibration mixing on the performance of C50 composite cementitious material precast beams concrete,orthogonal experiments were used to optimize the optimal concrete mix proportion.Under the optimal mix proportion,the workability,compressive strength,and elastic modulus of concrete under different vibration mixing times were tested,and the influence mechanism of vibration mixing on the mechanical properties of concrete was analyzed by combining XRD and SEM.The results show that the optimal mix proportion of concrete obtained through orthogonal experiments is m_(cement)∶m_(mineral powder)∶m_(fly ash)∶m_(silica fume)∶m_(sand)∶m_(5~10 mm crushed stone)∶m_(10~20 mm crushed stone)∶m_(water)∶m_(polycarboxylate superplasticizer)=369∶27∶40.5∶13.5∶775∶214∶857∶144∶5.4.Vibration mixing can cause a decrease in the flowability of concrete.When the vibration mixing time is 90 s,the minimum decrease in the slump and expansion of concrete is achieved.With the increase of vibration mixing time,the compressive strength and elastic modulus of concrete show a trend of first increasing and then decreasing.When the vibration mixing time is 90 s,the compressive strength and elastic modulus of concrete reach their maximum.Vibratory mixing accelerates the hydration rate of cement,and promotes the generation of hydration products such as C-S-H gel and Ca(OH)_(2) crystal.The hydration products can more fully fill the pores and cracks in the interface transition zone of concrete,increase the compactness of the interface transition zone structure,thus improving the strength of concrete.