Steel/basalt rebar reinforced Ultra-High Performance Concrete components against methane-air explosion loads

Ultra-High Performance Concrete (UHPC) is a relatively new construction material, which has been investigated over the past few decades. Despite its exceptional mechanical strength, UHPC still requires passive steel reinforcement to maximise its bending capacity and the overall material cost will be high. The basalt fibre rebar has a higher mechanical strength than steel rebar with lower cost. In addition, it also has better alkali resistance and good cost-effectiveness. The basalt fibre rebar is therefore considered as a potential alternative reinforcement in the structural member. In this study, a recently developed UHPC formula was adopted, the conventional steel rebar and basalt fibre rebar were used as reinforcement. The developed components were tested against static flexural and methane-air explosion loads. In the four-point flexural tests, the basalt fibre rebar reinforced specimen (400 mm × 100 mm × 100 mm) performed more ductile structural behaviour with higher flexural strength. Two large scale methane-air explosion tests were conducted in buried utility tunnels with different length (i.e., 12000 mm × 1800 mm × 600 mm and 20000 mm × 1800 mm × 600 mm). The experimental test in shorter tunnel yielded lower explosion pressure [1] with marginal structural response. The test in longer tunnel achieved a higher explosion pressure on concrete elements. The C30 and UHPC specimens (1800 mm × 400 mm × 90 mm) with steel/basalt fibre rebar reinforcement were tested. The pressure and deflection data revealed that basalt fibre rebar reinforced UHPC component had a more ductile structural behaviour against accidental gas explosion.