Permeability of polymer-modified kaolinite and fly ash–kaolinite mixtures

Abstract

With the goal of promoting the treatment and reuse of fly ash (FA), a series of permeability tests were conducted to investigate the hydraulic conductivity (K) of polymer (chitosan, polyethylene oxide (PEO) and xanthan gum)–FA—kaolinite (KA) systems under different confining pressures and overconsolidation ratios (OCRs). The addition of FA increased the K of KA due to changes in particle size and gradation, and the effect is not significant when the FA content is below 30%. PEO and xanthan gum increased the K of KA, with xanthan gum having a more significant effect, while chitosan reduces it. For FA–KA mixtures, chitosan and xanthan gum had negligible impact on the K, whereas PEO increased it by an order of magnitude. In addition, confining pressure restricts the flow channel while increasing the effective contact area between polymers and soil particles. The Koc/Knc of polymer-modified KA rapidly converges at high OCRs, while that of polymer-modified FA–KA converges at low OCRs. This study provides insight into the effects of polymer modification on the hydraulic conductivity of FA–clay mixtures and provides guidance for the application of polymer modification technology in soil improvement.