Study on the Influence of Vibration Mixing on the Properties of Concrete Mixed with Precast Beams
The slump,slump loss over time,air content,apparent density,compressive strength and frost resistance of concrete under two mixing methods were tested.The content of hydration prod-ucts,micro-morphology and pore size distribution of concrete were tested by thermogravimetric analy-zer,scanning electron microscope and mercury intrusion meter respectively.The results show that,compared with forced mixing,vibration mixing has an adverse effect on the slump and slump loss of precast beam concrete mixed with cementitious system,but it has a significant effect on improving the air content,apparent density,compressive strength and frost resistance of concrete.Vibration and stirring can increase the CH content of precast beam concrete mixed with cementitious system by 22.4％at 3d age,and reduce the contents of few harmful holes,harmful holes,many harmful holes and total porosity by 16.1％,42.3％,37.9％and 27.6％respectively.There are no obvious micro-cracks in the interface transition zone and the structure is compact.Vibration mixing can improve the compactness,frost resistance and compressive strength of concrete by increasing the number of hydra-tion products of precast beam concrete mixed with cementitious system,improving the micro-morphol-ogy of interface transition zone and refining the pore size distribution.
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