Flexural behaviour of graded concrete beams on maximum reinforcement ratio

The use of graded concrete (GC) is expected to reduce cement consumption and increase the rigidity of the structure. The absence of relevant works of literature discussing the use of maximum reinforcement on GC structures motivated the researchers to study this case. Previous research only concentrated on the behaviour of reinforced concrete (RC) beams with a minimum reinforcement design. The possibility to use maximum reinforcement is always open due to the limitation of the cross-sectional dimensions of the building elements due to architectural considerations. For further applications, GC beams with maximum reinforcement are expected to be more ductile than conventional RC beams using high-strength concrete. This study used two significantly different concrete strength as the concrete mix to cast beam specimens, namely the 20 MPa and 40 MPa. The beam specimens were grouped into two types, namely control beam and GC beam, both of which were designed with the use of maximum reinforcement. All beams were tested in flexure using four-point bending. The results show that: GC beams experienced a reduction in concrete strength in the tensile fibre resulted in the decrease of rupture resistance at the first crack, the presence of higher strength concrete layer increase the load-carrying capacity of GC beams and decrease the resulting deflection at yield and ultimate phase so it improves the structural performance.