Flexural behaviour of the functionally graded concrete beams using two-layers and three-layers configuration

Abstract

Studies related to the bending behaviour of functionally graded concrete (FGC) beams are still investigated to explore the possibility of the more cost-efficient casting techniques and to produce high-performance FGC beam elements simultaneously. Previous researches show that the manufacture of FGC beams by combining two concrete mixes in two layers can increase the stiffness of the elements but it reduces the beam ductility. Research concentrating on the FGC beams with additional numbers of concrete layers was analysed in this study. Four pieces of FGC beams measuring 120 x 240 x 2200 mm were prepared with concrete strength of 25 MPa (NA); 30 MPa(NB); 30-20 MPa (GBA); and 30-20-30 MPa (GBAB). The specimens were tested in the laboratory using a four-point bending method. The experimental data consisting of the load increments and the mid-span deflections are further analysed to compare the resulting (1) maximum load-carrying capacity; (2) maximum deflection; (3) beam stiffness; (4) moment-curvature; and (5) ductility. The result shows that (1) the GBAB exhibited 0.83% greater maximum loads than the GBA; (2) the GBAB deflected 29.52% lesser than the GBA; (3) the GBAB posses stiffness 12.03% greater than the GBA; (4) the GBAB exhibited higher resulting yield points and ultimate state than the GBA at the moment-curvature relationship; and (5) the GBAB was 20.06% less ductile than the GBA.