Potential utilization of waste sludge and waste rock from Sin Quyen copper ore mining combined with coal fly ash for producing roller-compacted concrete for road subbase construction

Abstract

Currently, Vietnam is facing a shortage of natural sand supplies for construction purposes in several regions. Therefore, the research and development of alternative materials such as manufactured sand to replace natural sand is considered an effective solution not only in terms of economics and engineering but also in regard to environmental sustainability. In this study, mining sludge, manufactured sand and crushed aggregate derived from waste rock produced during copper ore extraction at the Sin Quyen mine (Lao Cai province) were combined with coal fly ash from the Son Dong thermal power plant (Bac Giang province) to produce roller-compacted concrete (RCC) under laboratory conditions. The research results indicate that with the replacement of Portland cement by 10% to 30% (by volume) of coal fly ash and mining sludge, the RCC mixtures exhibited a Vebe time of 20 - 40 seconds and, at 28 days of curing, achieved the following average mechanical properties: Flexural tensile strength ranging from 3.08 to 3.58 MPa, compressive strength from 24.5 to 28.5 MPa, abrasion loss between 0.300 and 0.334 g/cm2 and static compressive modulus of elasticity between 38.5 and 41.5 GPa. These findings suggest that the RCC developed in this study can be effectively used as a base layer material for high-grade pavement structures.

Keywords: Fly ash, mining sludge, waste rock, roller compacted concrete, hardness, compressive strength, abrasion.