Production of gold mine tailings based concrete pavers by substitution of natural river sand in Misisi, Eastern Congo

Abstract

For nearly a decade, the artisanal and small-scale gold mining (ASGM) in Misisi, eastern Congo, has been storing piles of gold mining tailings (GMT) from cyanide leaching. These tailings are stored carelessly in the nature without respect for environmental and sanitary standards, leading to soil and underground pollution risks. In order to valorize the GMT of Misisi, they were incorporated in concrete and from this concrete, pavers were produced. In addition to GMT, these pavers are made of gravel, cement and water. The compressive strength of the GMT-based pavers was compared with that of the natural river sand (NRS)-based pavers made up of NRS, gravel, cement and water. Both types of pavers were produced under the same drying conditions (7 days) with different dosages of gravels, cement and water for each type. More gravel and water were used for the GMT-based pavers with the same amount of cement for both types of pavers. The compressive strength was similar between GMT and NRS pavers with a breaking stress of 27 N/mm2. It was found that the use of a specific dosage for GMT-based pavers that differs from the dosage of NRS-based pavers had a positive impact on their compressive strength, specifically due to the larger amount of gravel used for GMT-based pavers. This paper shows that the production process of pavers also had an impact on their compressive strength. The particle size, elemental chemical characteristics and organic content were favorable for GMT to substitute NRS. The GMT consist of 75% sandy aggregate with an organic matter content of 4.49% and 52% of silica. This study consists of a first global vision of the possibility of total substitution of NRS by GMT in concrete pavers. The study's aims is to provide a perspective of the substitution of NRS by GMT in concrete paver production. Further studies of mechanical properties and durability will be necessary before considering a large scale adoption.