Estimating the Effect of Vibration Mixing Process on Air Pore Size Distributions in Concrete Using Digital Image Analysis

Abstract

Concrete is a typical porous material, in which the air voids entrained or entrapped during the mixing process have a significant impact on the material’s strength and durability. An automatic methodology based on digital image analysis was used to examine the influence of a novel mixing process with vibration on the entrapped air pore size and distribution of concrete in this paper. The volume of permeable spaces and porosity in hardened concrete are found to be greatly reduced when using the vibration mixing process compared to the reference concrete. Meanwhile, the quantity of air pores and their specific surface area are positively associated with the vibration acceleration, while the average equivalent pore diameter decreases. The findings of the analysis of variance (ANOVA) reveal that the population means for porosity, quantity, and pore size are significantly different when utilizing the vibration or non-vibration mixing processes. Furthermore, the pore size distribution curves show that the vibration mixing process significantly modified the pore structure by reducing the number of larger size pores and increasing the amount of small size pores. This may be attributed to a series of changes in the bubbles during the vibration mixing process. In addition, the findings of freeze-thaw resistance and water penetration resistance reveal that, owing to the vibration mixing process, the impermeability and durability of the concrete are significantly improved.