Experimental Study for the Comparison between Core, Schmidt and Cubic Concrete Compressive Strength After Durability Test

Abstract

Estimating the compressive strength of concrete exposed to different environmental conditions is an essential parameter in judging the quality of concrete and proving its ability to perform as planned. There are various destructive (DT) and non-destructive (NDT) methods for estimating compressive strength. Some NDT and DT procedures, such as Schmidt hammer and core testing, have been used for estimating concrete strength for a long time. These methods consider indirect and predicted tests to evaluate concrete strength in existing structures. Various factors influence these tests, so it is difficult to precisely assess the hardened concrete strength. Thus, this research aims to identify a coherent relationship that connects the results of these tests and correlates them with the results of cube compressive strength by assessing data from laboratory tests conducted under control and durability conditions using statistical techniques. To achieve this purpose, three grades of concrete were considered C250, C450, and C600 Kg/cm2. Six concrete cubes of size (15x15x15 cm) and four concrete columns of size (30x15x50 cm) were cast for each grade and tested to assess the cube, Schmidt hammer, and core compressive strength of concrete. Half of the columns and cubes were cured in drinking water (control condition) and the other half of the samples were subjected to durability cycles for 92 days (durability condition). In the durability condition, the samples were exposed to 10% sodium sulfate solution for a day, placed in a water tank for a day, heated to 100°C at a laboratory furnace for a day and then left at average laboratory temperature for a day to finish one cycle. The results were tabulated and graphed to notice any differences between DT, NDT and cube compressive strength tests. The results showed that the cube strength is higher than the core strength for all grades of concrete under control and durability conditions. The cube test indicates a lower compressive strength than the Schmidt hammer test method at grade C250 under control condition and greater compressive strength in the rest of the grades.