Method for preparing concrete by use of multi-layer pan type mixer

A method for producing concrete in a multi-layer pan type mixer comprising upper and lower mixing tanks driven by separate motors and a discharge gate communicating the upper mixing tank with the lower mixing tank, said method comprising supplying sand, cement and primary mixing water into the upper mixing tank to perform primary mixing therein to obtain a mortar, said primary mixing water being in a quantity which is suitable for said primary mixing and necessary to ensure that said mortar has substantially predetermined properties, discharging said mortar into the lower mixing tank, simultaneously supplying gravel and secondary mixing water into the lower mixing tank to disperse the gravel in said mortar, said secondary mixing water being in a quantity which is equal to the quantity of water required to obtain desired properties, less that quantity primary mixing water introduced into the upper mixing tank, and performing secondary mixing in the lower mixing tank.