FIBRE-REINFORCED SHOTCRETE GAINS TRACTION IN MINING

Caption: Fibre reinforced shotcrete application in underground tunnel.

In recent years, the mining industry in South Africa has become a major user of fibre-reinforced shotcrete for underground support. In line with this trend, CHRYSO Southern Africa reports growing demand for its market-leading CHRYSO CSF 6000 high performance macro-synthetic fibres.

Fall of ground (FOG) – one of the leading causes of injuries and fatalities in underground mines – remains one of the biggest obstacles to the industry’s quest for Zero Harm in South Africa. The fight to eliminate FOG incidents is therefore one of the main reasons for the escalating use of fibre reinforcement in shotcrete, says Willie Nel, Technical Sales Consultant at CHRYSO Southern Africa.

Having traditionally used reinforced shotcrete with wire mesh or welded mesh, the industry then moved over to fibres. These were initially steel fibres and then rigid polypropylene ‘broombrissel’ fibres took centre stage. However, the past decade has seen an accelerated switch to polypropylene homo-polymer fibres – a soft tape fibre.

“The move to soft tape fibres gained traction from around 2012,” explains Nel. “During that period, we have experienced growing demand for our CHRYSO CSF 6000 high performance macro-synthetic fibres which are specifically designed to satisfy the demanding requirements for modern day shotcrete reinforcement technology. In our experience, the trend is largely being driven by new mining projects.”

A major advantage of the CHRYSO CSF 6000 is its flat, flexible nature which leads to better tensile strength than, for example, the rigid ‘broombrissel’ counterparts. In addition, it combats the formation of plastic shrinkage and plastic settlement cracking, while still providing high impact-, abrasion- and shatter-resistance. The technology, adds Nel, boasts greater ductility, which allows it to deform under tensile stress, as well as enables greater energy absorption.

This was proven at one of the biggest copper mines in South Africa, where the client stipulated a 45 MPa shotcrete mix design. CHRYSO Southern Africa went on to achieve over 1000 joules of energy absorption by using the CHRYSO CSF 6000 macro-synthetic fibres.

“Traditional reinforcement practices such as wire mesh and welded mesh are not conducive to high productivity and are costly due to the labour intensive process of mesh installation. In contrast, macro-synthetic fibre-reinforced shotcrete is a system capable of supporting rapid application and semi-automation,” says Nel.