Study on the pores characteristics and permeability simulation of pervious concrete based on 2D/3D CT images

Abstract

The pores characteristics such as pores size, distribution and specific surface areas play a dominant role in the permeability of pervious concrete. The aim of this research was to identify the pores characteristics in pervious concrete by 2D/3D CT images and investigate the relationship between pores characteristics and permeability. Eight groups of pervious concrete specimens with almost the same porosity but different aggregate size were prepared. Based on CT imaging technology, the 2D/3D pores characteristics were extracted and analyzed. It was found that the pores in pervious concrete were usually surrounded by three to seven aggregates. Most of pores were close to an ellipse with the ratio between major axis and minor axis varied from 1 to 6. According to the influence of pores size on permeability, pores were artificially classified into three groups, small (<20 mm2), medium (20 mm2–50 mm2) and large pores (>50 mm2). With the aggregate size increased, the content of small pores decreased and the proportion of large pores increased, while the content of medium pores had no significant change. Whatever the aggregate size was, lots of (>14%) “small pores (<2 mm2)” existed in pervious concrete. Subsequently, the absolute permeability experiment simulation of pervious concrete was conducted by the software of Avizo. The results of permeability simulations showed the permeability increased with the increase of 2D/3D pores size and decreased with the increase of the total pore surface area. Permeability is more sensitive to the content of small pores compared to large pores and medium pores. With aggregate size increases, the number of seepage flow lines increases and the seepage flow paths become thicker, which contribute to water permeation. The permeability simulations results corresponded to the laboratory results.