A specially designed Vibrating Machine is used for vibrating the mix in moulds according to strictly controlled programme at a frequency of 12,000 ± 400 cycles per minute. The vibrator is mounted over coiled springs and the vibrations are developed by means of a revolving eccentric shaft. The center of gravity of the vibrator, including the cube mould, is either at the center of eccentric shaft or within 25mm below it. The simple design of the machine facilitates easy assembly and dismantling of the cube moulds. The machine is suitable for operation on 220V, 50Hz, single phase, AC supply.