Development of Relation between Non-Destructive Test and Mechanical Properties of Concrete

Abstract

The NDT of concrete in today's scenario has received a great importance in terms of practical and engineering value. The subject has received a growing attention during recent years, especially the quality characterization of damaged structure made of concrete using NDT testing. Massive structure like tall building, bridges requires them continuous quality checking. For this purpose, many techniques are involved which causes damage to the structure such as extraction of cores for checking the strength. Extraction of core is not advisable as it would results in damaging the structure and also, very expensive procedure. In non-destructive testing, number of advantages reduction in nos. of labours, lesser structural damage, prediction of concrete strength without extraction of cores, lesser cost of testing etc. These techniques are used to predict the strength of the structure with acceptable approximation. Therefore, in order to and the strength of the concrete structure, investigations were carried out for generating the correlation between the NDT results and the mechanical properties of concrete. The aim of present investigation is to develop correlation curves between compressive strength and NDT testing for concrete of different grades (M20, M30, M40, M50, M60, M70 and M80). It is proposed to develop multiple regression curves from the results of UPV and Rebound Hammer in determining the compressive strength of concrete at different ages 7, 28 days for better assessment of structure. Total 168 Specimen are casted for the investigation. standard size of cubes, beams and cylinders as per IS provisions are used for evaluating the compressive strength, flexural strength and split tensile strength. Cube specimens have been tested at the age of 7, 28 days for both destructive and non-destructive testing. In non-destructive test Rebound Hammer and UPV by direct methods. Beam and cylinder specimens have been tested at the age of 28 days for both non-destructive and destructive testing. Beam test Direct indirect and semi direct method of UPV. Correlation carried out between compressive strength and NDT results i.e. rebound no. and UPV at 7and 28 days. Core test is carried out on cube specimen after 28 days. After core test cylindrical cut part is tested in CTM and apply correction factor according to Indian standard. Find correlation between Rebound Number and corrected Core strength is determined. After taking out cylindrical specimen from cube remaining hollow part fill by lean concrete having Mixing Proportion of (1: 3: 6). when this filled material reaches 28 days then taking Non-destructive test UPV and Rebound Hammer on this specimen. For other mechanical properties correlation with NDT carried out. From the Correlation curves indicated that, there is good linear correlation between mechanical properties and NDT results. Combination of both NDT methods gives reliable results than one method. NDT method is most suitable for predicting the strength results without disturbing the structure.