Abstract:
Traditionally, the standard method used to assess the strength of concrete in compression in concrete structures under construction includes testing compressive strength, performed on specimens cast at the same time. But this method has many drawbacks that arise because: the results are not immediately available; the concrete specimens may be different from this of the structure, for the fact that the cure or compaction may be different. On the other hand, the strength properties of a specimen depend on its size and shape. The development of reliable methods for non-destructive evaluation of the properties of in situ concrete then became prove of particular importance. These methods are based on the fact that some physical properties of the concrete can be connected to the compressive strength and can be measured by nondestructive methods. - Ultrasound UPV ( ultrasonic pulse velocity) and - The rebound -hammer Are among the most popular and commonly used non-destructive methods to assess the compressive strength of concrete structures on-site because of their simplicity and their lower cost. The evaluation of the strength of concrete is then based on empirical relationships between the values of the parameters of non-destructive testing and the results obtained by destructive testing; crushing test tubes and cores. Therefore it is imperative to establish correlation equations by using multi-variable and developing algorithms in matlab environment. Given the variability of the parameters influencing the property of concrete such as : - the type and size of the aggregates, - the type and content of cement, - the implementation of the concrete and to account for these factors, both of the two tests are combined and their measurements are calibrated with the results of mechanical tests on cylindrical specimens cast on site and on cores taken from two existing structures in work progress at the new-city, Constantine in Algeria. In this study; the two tests cited above have been used to determine the concrete quality by applying regression analysis models between compressive strength of in situ concrete on existing structure and the nondestructive tests values, the combined method is used, equations are derived using statistical analysis (simple and multiple regression) to estimate compressive strength of concrete on site and the reliability of the technique for prediction of the strength is discussed for this case study.
