Compressive Strength Correlation of the Designed and As-Built Columns in Structures Using Non-Destructive Test Method- the Schmidt Rebound Hammer (Case Study: Kubwa, FCT-Abuja, Nigeria)

Abstract

Evaluating the compressive strength of concrete in new and existing buildings is important for assessing their structural integrity, for the early identification of structural issues, and for improving maintenance and safety measures. Columns in reinforced concrete buildings play a major role in load transfer and are most vulnerable to deficiencies in structural integrity, among other structural members. Consequently, this study analyzes the actual compressive strength (ACS) of columns in buildings in comparison to the designed compressive strength (DCS) through a non-destructive test (NDT) approach. The Data for this study was collected by carrying out the Schmidt Rebound Hammer (SRH) test on a sample size of 176 columns across 12 buildings in the study area. The rebound hammer type N was used as per BS EN 12504-2. This study established a power regression model, which was included in an MS Excel sheet to aid in the conversion of the rebound numbers. The highest, lowest, and average ACS were determined to be 20.035 MPa, 10.98 MPa, and 15.457 MPa, respectively; a significant variability in the compressive strength, with the average relative variation of -22.4%, was deduced, with building B11 indicating the strongest correlation with the DCS. Most building columns did not meet the DCS of 20 MPa, thus, it is recommended that the inadequate columns be recast under stringent supervision. For future projects in the study region, it was also recommended that concrete cubes be cast for laboratory checks of compressive strength.