Environmental Protection with HDPE Geomembranes in Mining Facility Constructions

Marcelo Kobelnik,Jefferson Lins Da Silva,Maria De Lurdes Lopes,Fernando Luiz Lavoie,Clever Aparecido Valentin,Érica Fernanda Da Silva Tirelli

doi:10.3390/constrmater1020009

Abstract

The present work evaluated two high-density polyethylene (HDPE) geomembranes exhumed from mining facility constructions in Brazil. The MIN sample was exhumed from a pond for water use for the iron ore process after 7.92 years of exposure. The MIN2 sample was exhumed from a spillway channel of a ferronickel tailing dam after 10.08 years of service. The physical evaluations showed high depletion for antioxidants that work in the temperature range of 200 °C. The samples presented brittle tensile behavior and had similar behaviors between stress cracking and tensile. Low tensile elongation values and low-stress crack resistance were noted. The MIN2 sample presented a higher melt flow index (MFI) value and lower stress crack resistance. Thermogravimetric curves (TG) under synthetic air purge gas evaluation showed that both samples presented a similar behavior during the evaluation but had several mass losses. The results showed that exothermic and endothermic events occurred with loss of mass and showed no combustion events in the differential thermal analysis (DTA) curve evaluation. Differential scanning calorimetry (DSC) analysis showed no changes in the samples’ behavior. Thus, the results of tensile, stress cracking, and viscosity properties can demonstrate that changes in polymer structure occurred after field exposures.

Highlights

A geomembrane is a polymeric or bituminous sheet manufactured by industry with a very low permeability coefficient that is applied as a barrier or separation element [1,2]
The geomembrane samples were able to experience the exposure of environmental agents in the field, such as ultraviolet radiation and thermal variations
The criteria utilized as a reference to compare the physical characterization of highdensity polyethylene geomembranes are determined by the American standard GRIGM13 [26], which specify the minimum property values for the product’s manufacturing quality control

Summary

Introduction

A geomembrane is a polymeric or bituminous sheet manufactured by industry with a very low permeability coefficient that is applied as a barrier or separation element [1,2]. The high-density polyethylene (HDPE) geomembrane is the most widely used geosynthetic, and is used as a liner in liquid and waste containment facilities [3,4]. The degradation mechanisms can occur due to UV radiation, thermal exposure, oxidative degradation, or chemical degradation. These mechanisms can act in isolation or work simultaneously, changing the polymer’s morphology [5,6]. The formulation of high-density polyethylene geomembranes comprises 96–98% of resin, 2–3% of carbon black, and 0.25–1.0% of additives as antioxidants and stabilizers. Additives and carbon black are used in the blend to protect the resin, retarding the polymer degradation to UV radiation and thermal degradation [7,8]

Methods

Results

Discussion

Conclusion