Effect of Bentonite Content and Hydration Time on Mechanical Properties of Sand–Bentonite Mixture

Yue Qin,Dongsheng Xu,Borana Lalit

doi:10.3390/app112412001

Yue Qin, Dongsheng Xu + Show 1 more

Open Access

https://doi.org/10.3390/app112412001

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Abstract

The bentonite is commonly used mixed with soils for groundwater retention and waste contaminant facilities. The incorporation of bentonite could significantly reduce hydraulic conductivity. In this study, the effects of bentonite content, hydration time and effective confining pressure on the static properties of a sand–bentonite mixture were studied using experimental and numerical methods. Firstly, a large number of drainage static triaxial tests on the sand–bentonite mixture with various bentonite contents were conducted. The test results show that the increase in bentonite content and hydration time leads to a slight decrease in shear strength and initial tangent modulus of the sand–bentonite mixture. The presence of bentonite reduces the shear shrinkage and dilatancy trend of the mixture. The cohesion of the mixture increases with the increase in bentonite content and hydration time, but the internal friction angle decreases correspondingly. The hydration of bentonite on the surface of sand particles changes the contact form between particles. The bentonite slurry between pores of the sand skeleton also affects the mechanical behavior of the sand–bentonite mixture. Then, a series of 3D discrete element models were established for numerical simulations of drainage static triaxial tests. The numerical model parameters were calibrated by experimental results. The meso-mechanism of bentonite content affecting the mechanical behavior was revealed according to the contact force distribution between particles. The research results are helpful to understand further the mechanism of bentonite on the mechanical properties of the sand–bentonite mixture.

Highlights

Bentonite is a kind of soft clay produced by weathering and erosion of volcanic ash with the major mineral composition of montmorillonite [1]
The results indicate that the peak shear strength of the mixture specimen decreases with the increase in bentonite content, and the shear strength of the sand–bentonite mixture remains more than
The hydration and expansion of bentonite in the pores of sand make the direct contact of sand–sand interface change to the contact of sand–bentonite pore grout, which was thought to be the reason for the slight decrease in shear strength with the increase in bentonite content

Summary

Introduction

Bentonite is a kind of soft clay produced by weathering and erosion of volcanic ash with the major mineral composition of montmorillonite [1]. It is a type of clay composed of two tetrahedral and one octahedral flake in a ratio of 2:1. The bentonite particles are in the shape of thin circular disks with diameters of the order of. The surface of the thin circular disks is negatively charged, while the edges have positive charges. The total charge of the entire particle is negative [2,3,4,5]

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