Influence Of Viscosity Enhancing Agent On Bubble Parameters And Freezing Resistance Of Conrete

The annual winter in northern China is 3-6 months.The actual engineering concrete is damaged by freezing and thawing,which causes the structure to fail prematurely or even collapse.Due to the long-term transportation,pumping and vibrating operation of the fresh concrete during the construction process,a certain degree of segregation and bleeding will cause the original bubble system to be destroyed,resulting in serious frost resistance of the concrete structure in the actual project.Below the laboratory design level.Therefore,it is important to study how to improve the frost resistance of concrete in actual projects in severe cold regions.This paper analyzes the mechanism of bubble motion and stability in concrete,and studies the effects of different thickener types and dosages on the properties of fresh concrete,as well as the upper,middle and lower concrete under vertical casting.The effect of bubble parameters and frost resistance on the height range.Research indicates:With the increase of the three thickeners HPMC,PAM and xanthan gum,the yield shear stress first decreases and then increases,while the plastic viscosity increases.The surface tension value of the slurry depends on the amount of the air entraining agent,the amount of the water reducing agent,and the molecular structure and the amount of the thickener.There is a critical dimension of the bubble radius in the slurry,which depends mainly on the ultimate shear stress of the slurry.The maximum velocity of the bubble is inversely proportional to the viscosity of the slurry.There is a reasonable threshold for the slurry rheological parameters.The proper viscosity can slow the liquid film drainage,enhance the surface film strength,and improve the bubble stability.Under the appropriate amount of HPMC,PAM and xanthan gum,the bubble spacing coefficient is reduced by 30%-50%,and the average radius of the bubbles is reduced to some extent.The suitable thickener dosage is related to concrete water-togel ratio,cementitious material,the amount and molecular structure of the thickener.HPMC has the most obvious reduction in the bubble spacing coefficient,and the bubble stabilization effect is the best.When the concrete strength grade is C35,the anti-freezing grade of the test piece is obviously improved under the appropriate amount of HPMC,PAM and xanthan gum,and the salt-freezing performance of the upper,middle and lower parts of the test piece is better.HPMC and PAM have better anti-freezing effect.