KORELASI BENTUK SPESIMEN TERHADAP KEKUATAN TEKAN BETON THE CORRELATION OF SPECIMEN SHAPE ON COMPRESSIVE STRENGTH OF CONCRETE

Abstract

The standard testing procedure of concrete compression strength is by the use of cylinders or cubes, tested at an age of 28 days. According to the PBI 1971-NI-2 Code for Reinforced Concrete (Peraturan Beton Bertulang Indonesia) the specimens are 150 x 150 x 150 mm in size, while SNI uses the 150 x 300 mm cylinders. These two approaches results in a different characterizing of concrete compression strength. Cubes give a K value, and cylinders results in a f’c value. In practice, the concrete industries frequently make us of non-standardized molts. Cubes ranging from 100 x 100 x 100 mm to 200 x 200 x 200 mm are detected, while cylinders can have various dimensions, especially when originating from onthe- field sample taking with a core-drill. The question then arises, how the dimension and specimens shape is influencing the measured compressive strength. This research work was conducted to give a better understanding to the influence of variations in both dimension and shape to the standard specimens described by the code. For experimental use, cylinders of 110 x 220 mm were tested and compared to standard cylinders, and cubes 100 x 100 x 100 mm were compared to standard cubes. The test results were also evaluated against former research results. Generally, it can be concluded that the measured compression strength of cubes increase as a function of size decrease. For cylinders however, the opposite hold, and the compression strength of the smaller cylinders tent to be lower then the standard specimens. Shape correlation between cylinder and cube showed that compression strength values of cubes were higher than cylinders strength values. Keyword : mold size, mold material, l/d ratio, h/a ratio, compressive strength.