How can you physically identify the grade of cement after casting?

To physically identify the grade of cement after casting, you can perform a simple compression test on the cured concrete samples. Each grade of cement has a specific compressive strength, typically measured at 28 days. By applying a load to the sample until it fails, you can compare the measured strength to standard values for different cement grades. Additionally, observing the consistency, color, and texture of the cured concrete can provide some qualitative insights, but the compressive strength test is the most definitive measure.