SEBS-Polymer-Modified Slag–Cement–Bentonite for Resilient Slurry Walls

Benyi Cao,Abir Al-Tabbaa,Yunhui Zhang

doi:10.3390/su14042093

Abstract

In spite of the well-established design and construction approaches of slag–cement–bentonite slurry walls, the materials deteriorate inevitably in contaminated land. The development of effective materials which are sustainable, resilient and self-healing over the lifetime of slurry walls becomes essential. This study, for the first time, adopts a styrene–ethylene/butylene–styrene (SEBS) polymer to modify slag–cement–bentonite materials to enhance mechanical and self-healing performance. The results show that the increase in SEBS dosage results in significantly increased strain at failure, indicating the enhanced ductility thanks to the modification by the deformable polymer. The increased ductility is beneficial as the slurry wall could deform to a greater extent without cracks. After the permeation of liquid paraffin, the SEBS exposed on the crack surface swells and seals the crack, with the post-healing permeability only slightly higher than the undamaged values, which exhibits good self-healing performance. Scanning electron microscopy and micro-computed tomography analyses innovatively reveal the good bonding and homogeneous distribution of SEBS in slag–cement–bentonite. SEBS acts as a binder to protect the slag–cement–bentonite sample from disintegration, and the swollen SEBS particles effectively seal and heal the cracks. These results demonstrate that the SEBS-modified slag–cement–bentonite could provide slurry walls with resilient mechanical properties and enhanced self-healing performance.

Highlights

The in situ treatment of contaminated land has usually involved either source removal or pathway management, and the installation of physical barriers to contain the contaminants is becoming more widespread
The microstructure and morphology of SEBS in the cementitious matrix were revealed using scanning electron microscopy energydispersive X-Ray (SEM-EDX) and micro-computed tomography techniques. These results demonstrate that the SEBS-modified slag–cement–bentonite could provide slurry walls with resilient mechanical properties and enhanced self-healing performance
This study used liquid paraffin as the permeation liquid in the permeability tests because it is highly stable and less toxic compared to other organic liquids

Summary

Introduction

The in situ treatment of contaminated land has usually involved either source removal or pathway management, and the installation of physical barriers to contain the contaminants is becoming more widespread. The cement–bentonite slurry trench wall is one of the most common ground barrier systems for underground water and contaminant containment [1]. The technology has developed from cut-off walls for dams and is resistant to high hydraulic gradients [2]. The cement–bentonite slurry is produced by hydrating bentonite slurry and mixing it with cement before discharging it into a 0.5–1 m wide trench. The water-to-cement ratios are typically in the range of. Without bentonite such high water-to-cement ratios would lead to rapid settlement of cement particles to produce free water and a sediment. In cement–bentonite slurry it is the structure of hydrated bentonite gel that limits bleeding. The traditional composition of the slurry consists of Portland ordinary cement (OPC) and sodium bentonite [3,4]. Improved workability, increased strength, reduced permeability, alkali silica reaction mitigation and improved

Methods

Results

Conclusion