Insight into Saturated Hydraulic Conductivity of Cemented Paste Backfill Containing Polycarboxylate Ether-Based Superplasticizer

Sada Haruna,Mamadou Fall

doi:10.3390/min12010093

Abstract

Recycling of tailings in the form of cemented paste backfill (CPB) is a widely adopted practice in the mining industry. Environmental performance is an important design criterion of CPB structures. This environmental performance of CPB is strongly influenced by its saturated hydraulic conductivity (permeability). Superplasticizers are usually added to improve flowability, but there is a limited understanding of their influence on the hydraulic properties of the CPB. This paper presents new experimental results on the variations of the hydraulic conductivity of CPB containing polycarboxylate-based superplasticizer with different compositions and curing conditions. It is found that the hydraulic conductivity of the CPB decreases with the addition of superplasticizer, which is beneficial to its environmental performance. The reduction is largely attributable to the influence of the ether-based superplasticizer on particles mobility and cement hydration. Moreover, both curing temperature and time have correlations with the hydraulic conductivity of CPB containing superplasticizer. In addition, the presence of sulfate and partial replacement of PCI with blast furnace slag reduces the hydraulic conductivity. The variations are mainly due to the changes in the pore structure of the CPB. The new results discussed in this manuscript will contribute to the design of more environmental-friendly CPBs, which is essential for sustainable mining.

Highlights

Cemented paste backfill (CPB) offers an efficient means of mine waste valorization both environmentally and economically
The hydraulic conductivity of the CPB showed a consistent decrease for all samples over the curing period regardless of the tailings type and the superplasticizer content, as observed from Figure 2
The influence of curing time was largely dependent on the progression of cement hydration

Summary

Introduction

Cemented paste backfill (CPB) offers an efficient means of mine waste (i.e., tailings) valorization both environmentally and economically. The tailings, which is the waste from the milling process, are combined with a binder, water, and chemical admixtures, when applicable, and used to fill the voids created from the mining. To ensure optimum performance of CPB, its early-age and long-term behaviors have to be incorporated in the design [7,8,9,10]. Some of these properties are responsible for its environmental performance (e.g., leachability, susceptibility to acid mine drainage) and are largely associated with hydraulic conductivity [11,12]

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