A design concept with the use of RUHTCC beam to improve crack control and durability of concrete structures

Aiming at design issues of strictly anti-cracking structures or aseismic design in crucial locations of structures when using ultra high toughness cementitious composite (UHTCC), investigations on flexural behavior of reinforced ultra high toughness cementitious composite (RUHTCC) members are carried out due to excellent crack dispersion and strain energy absorption abilities of UHTCC. According to elastic theory, a calculation model of strain-hardening composites flexural members including theoretical calculation of moment, deflection and curvature, as well as critical reinforcement ratio is proposed in detail. Then experiment on RUHTCC beams without web reinforcement is performed to verify theoretical equations. For RUHTCC beams, there is a good agreement between test results and theoretical calculation. The safe calculated ductility indices can be used to predict ductility of structures. Compared with reinforced concrete beams, UHTCC delays yielding of reinforcements and improves load bearing capacity and ductility of structures, then steel reinforcement is saved; low reinforcement ratio is propitious to exert advantages of UHTCC. Under service load conditions, crack width in RUHTCC beams is limited to 0.05 mm and can be considered without negative influence on durability. Durability of structures will be significantly improved by using UHTCC instead of concrete.