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Geomechanics and Engineering
  Volume 22, Number 4, August25 2020, pages 329-337
DOI: http://dx.doi.org/10.12989/gae.2020.22.4.329
 


Compressibility and hydraulic conductivity of calcium bentonite treated with pH-responsive polymer
Hyunwook Choo, Youngmin Choi, Young-Uk Kim, Woojin Lee and Changho Lee

 
Abstract
    Polyacrylamide (PAM) possesses high water absorption capacity and a unique pH-dependent behavior that confer large potential to enhance the engineering performance of clays. In this study, calcium bentonite was treated with a nonionic PAM. Flexible-wall permeability test and the consolidation test were performed at different pH values to evaluate the effects of PAM treatment on the hydraulic and consolidation properties. Test results demonstrate that index properties are affected by the adsorbed PAM on clay surface: a decrease in specific gravity, a decrease in net zeta potential, and an increase in liquid limit are observed due to the PAM treatment. At a given pH, the compressibility of the treated clay is greater than that of the untreated clay. However, the compression indices of untreated and treated clays can be expressed as a single function of the initial void ratio, regardless of pH. Hydraulic conductivity is reduced by PAM treatment about 5 times at both neutral and alkaline pH conditions under similar void ratios, because of the reduction in size of the water flow channel by PAM expansion. However, at acidic pH, the hydraulic conductivity of the treated clay is slightly higher than the untreated clay. This reflects that the treated bentonite with PAM can be beneficially used in barrier system for highly alkaline residues.
 
Key Words
    polyacrylamide; calcium bentonite; hydraulic conductivity; compression index
 
Address
Hyunwook Choo: Department of Civil Engineering, Kyung Hee University, Yongin, South Korea 17104

Youngmin Choi: SK Engineering & Construction Co., Ltd., Seoul, South Korea

Young-Uk Kim: Department of Civil and Environmental Engineering, Myongji University, Yongin, South Korea 17058

Woojin Lee: School of Civil, Environmental, and Architectural Engineering, Korea University, Seoul, South Korea 02841

Changho Lee: Department of Civil Engineering, Chonnam National University, Gwangju, South Korea 61186
 

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