ISSN 2320 – 6020
IJBSTR RESEARCH PAPER VOL 1 [ISSUE 6] JUNE 2013
Comparison of Core and Cube Compressive Strength of Hardened Concrete Rohit Rai1, Ambareesh Kumar2, Ashish Singh3, Kanhaiya Lal Pandey4 and R D Patel* ABSTRACT- This paper presents the result of core and cube compressive strength of hardened concrete. Non-destructive test methods are used to investigate the properties and strength of hardened concrete. In existing concrete structures there was no direct relation between the results of non-destructive tests. This paper describes the relation between core compressive strength and cube compressive strength of hardened concrete in existing structures. Sixteen cores (diameter 75mm) were extracted from the hardened concrete of 15- years’ old building. Fifteen cores (48mm diameter) were also extracted from the same hardened concrete building. Two sizes of cubes (150mm x 150 x 150mm) and (100mm x 100mm x 100mm) were made from the hardened concrete from stone pieces which were taken from the structural members of building with help of stone cutting machine. The cores and cubes compressive strength was determined in compression testing machine. It was found that smaller size cubes (100mm x 100mm x 100mm) and cores (48mm diameter) show greater strength as compared to larger size cubes (150mm x 150 x 150mm) and cores (diameter 75mm). It was also found that the cubes (150mm x 150 x 150mm) compressive strength is 74% the cubes (100mm x 100mm x 100mm) compressive strength. The 75mm diameter cores compressive strength is 65% the compressive strength of cubes (150mm x 150 x 150mm). KEY WORDS: Compressive Strength, flexure Strength, Core.
INTRODUCTION Once concrete has hardened it can be subjected to wide range of tests to prove its ability to perform as planned or to discover its characteristics if its history is unknown. For new concrete this usually involves casting specimens from fresh concrete and testing them for various properties as the concrete matures. The concrete cube tests, concrete cylinder tests are the most familiar tests and are used as the standard method of measuring compressive strength for quality control purposes. Concrete beam specimens are cast to test for flexural strength and cast cylinder cone be used for tensile strength. Specimens for many other tests can be made at the same time to assess other properties. For existing concrete samples will need to be taken from the structure. Non-destructive testing methods are useful in some instances and can help identify areas from which samples should be taken. The normal method of concrete sampling is by coring although same chemical analysis techniques can be carried out on drilling dust samples.
*
Associate Professor, Civil Engineering Department, MMM Engineering College, Gorakhpur-273010 1,2,3,4
Research Scholar, “structural engineering” (Civil Engineering Department) MMM Engineering College, Gorakhpur-273010
In laboratory many techniques can be used to examine and test hardened concrete to assess a wide Varity of properties. Nondestructive and semi-destructive methods play an important role in evaluating the existing structure conditions. Nondestructive test methods are used to indicate properties other than strength. British Standard defined non-destructive testing as a test that does not impair the intended performance of the element or member under investigation. The non-destructive evaluation techniques are used to assess the condition of concrete structures, to predict future performance and allow minor repair system. The best known non-destructive evaluation techniques use ultrasonic waves, core testing, Schmidt hammer test. The estimation of in place concrete strength requires that a known relationship between the results of in-situ testing and the strength of concrete. For existing construction the relationship has to be assessed on site correlating non-destructive test results to strength of core. There was no any relation between core strength and cube strength of hardened concrete. In this research work a relationship between core strength and cube strength was developed. This paper also describes the effect of diameter of core on compressive strength of concrete and effect of size of cube on compressive strength of concrete. Cubes The compression text is carried out on specimens cubical and cylindrical in shape. The cube specimen is of the size 150mm. If the largest nominal size of the aggregate does not exceed 20cm and 10cm size cubes may also be used as an alternative. For each mix 15 cube specimens of size 150 x 150 x 150mm
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