Buttering the Mixer:

In machine mixing, a certain amount of cement mortar adheres to the inside of drum walls and remains adhered to after discharging the first batch of concrete mix. Thus, it is recommended that before mixing the first batch of concrete ingredients, a certain amount of cement mortar (i.e. cement, sand and water) is fed into the mixer and mixer is rotated. A quantity of mortar should be just enough to adhere to the walls. This procedure of mixing cement mortar prior to the mixing of first batch of concrete is called as buttering the mixer. In successive batches buttering is not required.