<p>This study investigates the reliability estimation of the compressive strength of brick, conventional concrete, and geopolymer concrete cubes through the application of non-destructive tests (NDTs). Non-destructive testing methods, such as rebound hammer and ultrasonic pulse velocity (UPV) tests, offer a rapid and practical approach for assessing the structural integrity and strength of materials without causing damage. The research evaluates the effectiveness of these methods in estimating the compressive strength of the three different materials brick, conventional concrete, and geopolymer concrete and compares the results with conventional destructive testing (CDT) methods like the compressive strength test on cube specimens. Statistical analysis is employed to establish correlations between NDT results and actual compressive strength values, providing insight into the reliability and accuracy of NDT techniques for different materials. The findings demonstrate that NDTs can serve as reliable alternatives to CDTs, though the level of accuracy varies depending on the material type. The study concludes that while NDT methods are highly effective for preliminary evaluations and in-situ assessments, further calibration may be required for different materials to ensure precise compressive strength estimation.</p>