Master Builders (MBT) introduced its S-152 HPP (High Performance Polypropylene) concrete reinforcement product at MINExpo in October. The product is a polymer-based fibre material designed to add toughness and ductility to hardened concrete, or shotcrete. The fibre provides added resistance to dynamic loading, impact and flexural fatigue.
According to MBT, it has enormous advantages over traditional steel fibres, as it does not corrode in aggressive environments and comparable dose rates in kg m3 are one-fifth that of steel. The product reduces the risk of damage to trailing cables and operator injury from the batch plant to the final in-place underground jobsite.
MBT said the new product can be used to enhance the structural performance of sprayed concrete beyond the level that can be achieved using secondary reinforcement. Mixed into the concrete using conventional mixing techniques, this high-strength fibre allows for relatively high fibre volumes, eliminating the need for welded wire mesh and providing three-dimensional reinforcement.
HPP fibres are shaped to resist matrix pullout, and can improve the load deflection performance of highly deformed concrete. Additionally, the use of HPP fibres in the concrete mix has proven to inhibit cracking, reduce sag and sloughing in vertical and overhead applications, and reduce rebound in shotcrete applications.
Another new product is the Masterseal 840 sprayable membrane, which can be used to simplify rock support and reduce overall cost of underground projects. The Masterseal 840 series of ground support membranes are elastic, non-cementitious membranes recommended for use early in the excavation cycle to replace wire mesh (screen) traditionally used for ground support between rock bolts. In short, it is designed as a mesh replacement material, MBT said.
The Masterseal 840 membranes exhibit rapid strength gain and can achieve 90% of ultimate tensile strength of more than 2MPa within 15 minutes, depending on the temperature at the time of application. MBT claims the applied cost of these membranes is significantly less than installed wire mesh. Because of the very quick installation achieved with spray application at a rate of 160m2 per hour, labour savings and reduced downtime provide even greater economics.
The membranes can be used in conjunction with rockbolts, and can be installed directly onto rock or other properly prepared surfaces such as shotcrete or geotextile drain fabric using a small pump with a spray wand mounted on a boom or hand-held. No toxic or hazardous vapours are produced during spraying, and the material is self-extinguishing in a fire situation.
