Concrete Core Strength of RC Beam Under Different Stress Conditions

Abstract

An experimental study has been carried out to observe the influence of different positions that affect the interpretation of core test results of a beam. For this purpose, a number of concrete cores have been drilled from RC beams. Six beams were tested under two-point loading to produce the first crack. In this experiment, six simply supported beams (three beams with stone chips and three beams with brick chips) were cast using three mix ratios (1:1.25:2.5, 1:1.5:3, and 1:2:4) where the maximum size of aggregates both for stone and brick was kept 3/4 inch down. The minimum reinforcement was provided in beams just to resist the temperature, shrinkage, and stresses due to handling. For each mix ratio, 4 in. diameter cores were drilled from different locations of each beam which experience different stress conditions under the bending test. The height-to-diameter ratio was maintained as 2.0. The water–cement ratio was 0.42 to maintain a slump within 3–4 in. The concrete cores and standard cylinders were tested in the laboratory following the standard method specified in ASTM. It was found that the compressive strength of concrete cores drilled from the RC beam is lower than the corresponding standard cylinder strength. The cores in the compression zone experienced higher strength than the core in the neutral zone, and the cores in the neutral zone experienced higher strength than the core in the tension zone.