Guniting 

It is used to form an impermeable layer using rich cement mortar (1 cement: 3 sand or fine aggregate mix) for waterproofing over exposed concrete surface or pipes, cisterns etc. to resist water pressure. contains

Gunite is a mixture of cement and sand or well-graded fine aggregate, the usual ratio being 1:3 or 1:4 (ie, 1 cement: (3 or 4) sand or fine aggregate). For this purpose a machine known as a cement gun, consisting of a nozzle for spraying the mixture and a drum of compressed air is used to force the mixture to the desired pressure. Any surface to be treated is first thoroughly cleaned of any dirt, grease or loose particles and then thoroughly wet. The mixture of cement and sand or aggregates is then shot at a pressure of 2-3 kg/cm2 by holding the toe nozzle of the cement gun at a distance of 75-90 cm from the surface of the wall. Immediately after the mixture comes out of the cement gun, the required amount of water is added through the regulating valve. Thus, a mixture of desired consistency and thickness can be sprayed or deposited to obtain an impermeable layer. This porous surface should be irrigated for at least 10 days.

By this technique, an impervious layer of high compressive strength (560–700 kg/cm2 after 28 days) is obtained and is therefore suitable for retrofitting or repairing old concrete works and brick or masonry works. Also very useful to do, which have either been damaged. Due to weather effects or inferior workmanship.