NFLUENCE OF SHEAR STRENGTH TRANSFER BETWEEN THE ADDED CONCRETE TOPPING AND EXISTING CONCRETE BY PUSH-OFF TEST METHOD
This paper investigates the influence of interface shear strength transfer between the added concrete topping and the existing concrete with different surface textures. The interface shear strength transfer between two layers of concrete is important to maintain the monolithic behavior of composite concrete. The surface textures at concrete base plays an important role to the interface shear strength. The cube compressive strength for the existing concrete as a concrete base is 40 N/mm2 while for added concrete topping is 25 N/mm2. There were three types of surface textures at the concrete base.The surface textures were treated with smooth as-cast, longitudinal groove line by using rod steel and wire-brushing roughened. The roughness surface was measured by roughness instrument to correlate it with the interface shear strength. A total of 36 concrete composite specimens of 300 x 300 x 75 mm deep were cast on precast unit of 300 x 300 x 100 mm deep and were tested by push-off test method under 0 N/mm2, 0.5 N/mm2, 1.0 N/mm2 and 1.5 N/mm2 to determine the shear strength between concrete layers. The friction coefficient was determined from the test and compared with the theoretical based on equation in Eurocode 2. Throughout this experiment, the surface roughness was quantified and correlated with the interface shear strength. Selected roughness parameters were suggested based on high correlation coefficient. According to the findings, roughened by wire brush produced the highest interface shear strength which can develop shear resistance more compare to other different surfaces.