BUNDREX is a Glued Steel Fibre product from Kosteel Ltd, made available in India by their Indian partner Onward Chemicals Pvt Ltd. CE-certified and conforming to ASTM A 820 and EN 14889-1: 2006 standards Bundrex, when added to conventional concrete, gives the resulting product – Steel Fibres Reinforced Concrete (SFRC) – many advantages over conventional concrete. It is able to absorb and dissipate energy more efficiently than normal concrete. Hence, it is ductile whereas normal concrete is brittle. It improves concrete’s wear resistance by 50% and fatigue resistance by 100%. The steel fibres impede crack formation and development of hairline cracks into major cracks by acting as tiny bridges.
SFRC offers improved compressive & flexural strength and resistance to abrasion, erosion and formation of cavitations. While conventional concrete fails at loads of 12.5kN, concrete added with Bundrex has a higher failure threshold of 20kN. The average modulus of rupture also is higher at 5.8Mpa compared to 3.5Mpa in normal concrete due to the higher energy required to pull out fibers from the matrix. Bundrex can be mixed with concrete in low dosages of less than 1%, moderate dosages of between 1 to 2 % or high dosages of above 2%. At low dosages, Bundrex reduces shrinkage cracking, and is used in slabs and floorings that have large exposed surfaces leading to high shrinkage cracks. At moderate dosages, it increases the modulus of rupture, fracture toughness and impact resistance, and finds applications in shotcrete, and in structures that require energy absorption capability, improved capacity against delaminating, spalling and fatigue. At high dosages, Bundrex leads to strain hardening of composites, and the resulting product is termed as high performance fibre reinforced concrete (HPFRC). These are used in structures demanding high performance – structures of strategic importance.
The use of SRFC with Bundrex in roads, highways and airstrips eliminates re-bars, ensures longer life with little maintenance, enables to take on high traffic and axle loads, even surface good finish and avoids distress cracking. The use of Bundrex in shotcrete eliminates the use of mesh and problems associated with it such as irregular positioning, creation of voids, shadowing, stone rebounds from mesh and concrete overuse. Some of the applications of shotcrete are in tunnels, mines, slope stabilisation on hilly terrains, and structural repairs.