a professional metal flap disc

LEMAN metal cutting discs ,If it is not safe to use water for the electric power source of your angle grinder, you should cut the concrete dry. As dry cutting uses the air as the coolant, after a period of cutting you should release the pressure on the diamond blade and allow it to rotate freely to let the air cool it. The metal flap disc can be a few minutes to a few seconds depending on the hardness of the concrete being cut (the harder the concrete, the shorter the cutting period should be).
Throughout the cutting process, you should wear a professional respirator, for the dust can seriously hurt your health.