Measurement of pore volume, connectivity and clogging of pervious concrete reactive barrier used to treat acid mine drainage

It has recently been shown that pervious concrete is a promising, effective technology as a permeable reactive barrier system for treatment of acid mine drainage (AMD). However, pore clogging also occurs simultaneously during AMD treatment. In the present study, mixtures of pervious concrete were made and used in a column experiment during which pore clogging occurred in the samples. Pore volume, connectivity and other parameters of pervious concrete were evaluated using five (5) different methods comprising the volumetric method (VM), linear-traverse method (LTM), image analysis (IA), falling head permeability test and X-ray microcomputed tomography. It was found that pervious concrete effectively removed from AMD, about 90 to 99% of various heavy metals including Al, Fe, Zn, Mn and Mg. Cr concentration significantly increased in the treated effluent, owing to leaching from cementitious materials used in mixtures. The VM and LTM gave statistically similar pore volume results, while IA's values were 20 to 30% higher than those of the conventional methods. The falling head permeability test and IA were found to be effective in quantifying pore clogging effects. Pervious concrete exhibited high pore connectivity of 95.0 to 99.7%, which underlies its efficacious hydraulic conductivity.

Automated summary

Pervious concrete is a promising technology for treatment of acid mine drainage (AMD) due to its ability to effectively remove heavy metals. However, pore clogging is a common issue during AMD treatment. This study evaluated the pore volume, connectivity, and other parameters of pervious concrete using different methods and found that it can remove 90-99% of various heavy metals from AMD. However, leaching from cementitious materials in the concrete caused an increase in chromium concentration in the treated effluent. Image analysis was found to be a more accurate method for evaluating pore volume, and the falling head permeability test and image analysis were effective in quantifying pore clogging effects. The high pore connectivity of pervious concrete contributes to its efficient hydraulic conductivity.