Reliability of Non-Destructive Test Approach on Structural Strength Assessment

Abstract

Complaints regarding structural integrity of an existing concrete building aroused questions and safety concerns on the actual condition of the building. Non-Destructive test approach like Rebound Hammer test and Ultrasonic Pulse Velocity Test were conducted to assess the building’s in-situ compressive strength on 10 locations respectively. 5 core samples (100mm x 100mm) were collected to compare and validate both NDTs’ results. Compressive strength conversion obtained through conversion curve for rebound number ranges from 37.07N/mm² to 56.90N/mm². The highest recorded reading for UPV test was 3840m/s, while lowest was 2505m/s. The quality of concrete was classified as good for 8 points, 10 doubtful, and 2 poor. Highest core strength was 32.93N/mm² and lowest at 15.78N/mm². This suggested compressive strengths obtained through rebound hammer test via the conversion curved indicated an overestimation behaviour. Using SONREB method, conversion of compressive strength using formulations by showed a nearer value to the core specimen compressive strength with highest R2 at 0.0683. Results using SONREB method showed a more reliable estimation of in-situ compressive strength. However, conventional DT method using core test still outrun the reliability of NDT approach in terms of estimation accuracy of compressive strength of existing concrete.