What is the primary reason for adding water to the drum before dry materials?

Adding water to the drum before dry materials is primarily done to ensure proper hydration of cement. When creating concrete, the hydration process is essential for the chemical reaction between water and cement to take place, ultimately leading to the hardening and strength development of the concrete mix. If water is added after the dry materials, there is a risk that the cement may not hydrate evenly, leading to weak spots and inconsistencies within the concrete.

This method of adding water first helps to create a more uniform mixture and enhances the overall quality of the concrete by allowing the cement particles to be fully surrounded by water from the outset. It sets the foundation for effective mixing and prevents issues that could arise later on in the mixing process.