THE PREDICTION OF IN-SITU COMPRESSIVE STRENGTH WITH NON-DESTRUCTIVE METHOD USING REGRESSION ANALYSIS

This study focuses on evaluating the relationship between destructive and nondestructive testing methods for predicting the in-situ compressive strength of concrete. The main aim is to develop a reliable regression-based model capable of estimating concrete strength using non-destructive approaches. The study specifically examined Grade 20 (C20) and Grade 25 (C25) concrete to determine the correlation between rebound hammer results, and conventional compressive strength tests. The experimental procedure involved casting and curing concrete cubes and beams in the laboratory under controlled conditions. Both destructive tests (compressive and flexural strength) and non-destructive tests (rebound hammer) were carried out at curing ages of 7, 14, and 28 days, following BS EN 12390-3:2019, ASTM C39, and BS EN 12504- 2:2012 standards. Rebound hammer readings were taken before compression tests on each specimen to establish a correlation between rebound number and actual strength. The data obtained were analyzed statistically using regression techniques to develop predictive models capable of estimating compressive strength from non-destructive test results. The findings revealed that compressive and flexural strengths increased consistently with curing age for both concrete grades. At 28 days, C20 achieved an average compressive strength of 20.16 N/mm², while C25 reached 25.15 N/mm², aligning with their design targets. Rebound hammer values showed a strong positive correlation with destructive test results, with a prediction accuracy of about ±5%. The study concludes that properly calibrated non-destructive methods, particularly the rebound hammer tests, can effectively predict the in-situ compressive strength of concrete. This approach provides a cost-effective, rapid, and non-invasive means for quality control and structural assessment in modern construction practice.