Effect of concrete strength configuration on the structural behaviour of reinforced graded concrete beams

Earlier experimental studies of graded concrete mentioned that by combining 2 (two) concrete mixes with distinguished strength, it created an advanced material with a higher modulus of elasticity. Research related to the application of graded concrete on beam elements has been conducted several times by researchers and produced numerous important findings. Research using finite element has been conducted to analyse the extensive use of graded concrete when applied to reinforced concrete beams with various configurations. This research aims to validate the findings of previous research in experimental works. Graded concrete beams made of 2 (two) layers of concrete mixes were tested. The difference between the two types of testing beams is in the configuration of concrete placement. The beams were tested under four-point bending procedure to obtain load-deflection data. The results show that the placement of higher concrete strength in the tensile fibres provides a better beam resistance to cracks indicated by an increase in the point at which the steel reinforcement experiences yielding. The greater the tensile strength of the concrete, the concrete will provide a better bonding to the steel reinforcement so that cracks can be minimized. A concave pattern is found in the transition area after the first crack. A noticeable curve pattern becomes apparent at beams composed of low concrete strength, whereas in the beam with high concrete strength only created a linear pattern. In terms of stability and structural strength, GBA has superior performance when compared to GAB. GBA tends to be able to continue to maintain the value of structural rigidity until the beam reaches the ultimate condition. Meanwhile, the GAB instantly loses its stiffness and to experience a sudden collapse.