Effect of working method on the strength reduction of reinforced concrete beams

Abstract

Poor workmanship and improper construction methods often lead to the reduction of the concrete strength. This paper aims to investigate the effect of working methods on the strength reduction of concrete. Nine beams with the dimension of 150 mm wide, 200 mm depth and 3300 mm length were tested with the variation of compaction method and curing method. The variation of compaction methods was by using vibrator (V), tamping rod in the first layer only (1L), and tamping rod in all layers (3L). Meanwhile, the variation of curing methods was by using water (W), wet burlap (K), and room temperature (RT). The results indicated that the beam that was compacted using vibrator and cured in water (V-W) showed the highest flexural capacity. On the other hand, the beam that was compacted with the tamping rod in one layer and curing at the open space (1L-RT) showed the lowest flexural capacity. The experimental results were compared with analytical calculation to obtain strength reduction factor. According to Indonesian Code SNI 2847:2013, the strength reduction factor for the reinforced concrete beams is maximum 0.8. The V-W beam showed the smallest strength reduction factor of 0.93, while 1L-RT beam showed the highest strength reduction factor of 0.75. Therefore, the results indicated that working methods of using one layer tamping road was exceeded the maximum the strength reduction factor specified by Indonesia Code.