Why Concrete Cubes shows greater strength than cylinder?

Concrete cubes typically exhibit higher compressive strength compared to cylinders at 28 days due to a few factors:

Shape Effect: Cubes tend to distribute stress more evenly than cylinders. The corners of cubes experience higher stress concentrations, which can lead to higher ultimate strength compared to cylinders. Additionally, the failure plane in cubes is often through the center, which is a more direct path compared to the inclined failure plane in cylinders.

Sample Preparation: Cubes are easier to manufacture and handle during casting and curing, resulting in more consistent and uniform specimens. Cylinders, on the other hand, are more prone to variations in casting and curing conditions, leading to potential differences in strength.

Concrete cube and cylinders

Surface Area-to-Volume Ratio: Cubes have a smaller surface area-to-volume ratio compared to cylinders of the same volume. This means cubes lose less moisture during curing, resulting in better hydration and potentially higher strength development.

End Conditions: The end conditions of cubes and cylinders can affect their strength. Cubes usually have smoother and more uniform end surfaces, while the ends of cylinders may not be perfectly flat. This can lead to differences in stress distribution during testing.

However, it's essential to note that the difference in strength between cubes and cylinders is not always significant and can vary depending on various factors such as mix design, curing conditions, testing procedures, and the specific characteristics of the concrete mixture used.