GUNITING

A ppt on methods of curing dampness through GUNITING

1. GUNITING By: Aryan Gupta Rakshit Raman Mahendra Bisht

2. What is Guniting The guniting is the most effective process of repairing concrete work which has been damaged due to inferior work or other reasons. It is also used for providing an impervious layer. The gunite is a mixture of cement and sand, the usual proportion being 1:3. A cement gun is used to deposit this mixture on the concrete surface under a pressure of about 20 to 30 N/cm 2 .

3. Key points :- Gunite is also known as shotcrete or pneumatically applied mortar. It can be used on vertical and overhead, as well as on horizontal surfaces and is particularly useful for restoring surfaces spalled due to corrosion of reinforcement. Gunite is a mixture of Portland cement, sand and water, shot into the place by compressed air . Guniting is basically used in swimming pool, dams, tanks, etc.

4. Guniting been done in a house

5. Mixture: A cement-sand mixture in the ratio of 1:2 or 1:3 depending upon the requirement, is applied at high pressure over the surface with the help of specialized equipment. Guniting is extensively used to rehalibate concrete bridges, dams, spillways, buildings, etc.

6. Mixture for guniting being made.

7. what IS THE PROCEDURE OF GUNITINg ? The cement is mixed with slightly moist sand and then necessary water is added as the mixture comes out from the cement gun. A regulating valve is provided to regulate the quantity of water. The surface to be treated is cleaned and washed. The nozzle of gun is generally kept at a distance of about 750 mm to 850 mm from the surface to be treated and the velocity of nozzle varies from 120 to 160 m/sec. Sand and cement are mixed dry in a mixing chamber, and the dry mixture along a pipe or hose to a nozzle, where it is forcibly projected on to the surface to be coated . The flow of water at the nozzle can be controlled to give a mix of desired stiffness, which will adhere to the surface against which it is projected.

8. Flow chart

9. Spraying of concrete There are two different methods of spraying: - Dry process spraying - Wet process spraying Dry process spraying is the process in which the mixture of damp sand and cement is passed through the delivery hose to the nozzle and the water is mixed at that time. Water cement ratio should be between 0.33 and 0.50 This process is often used for repair work. It is because of its fast application process and restoration of structural strength at early stage The performance characteristics of dry sprayed concrete are they have good density and high strength. It has very good bond to a suitable substance. These advantage make it more variable than conventional concrete abd wet process sprayed concrete.

10. Guniting in tunnel Guniting in wall A guniting machine

11. Quality finish Distance of spraying should be about 0.6m to 1.5m from treatment surface. Angle of spraying should as far as possible perpendicular to treatment surface. Formed in successively from top down without gaps or slumps. Freshly gunite surface should be protected from rain or strong sunlight. Wet slope surface should be allowed to dry by covering with tarpaulin for a few days before guniting to ensure good bonding between gunite and slope surface,

12. A well furnished guniting

13. WHAT ARE THE ADVANTAGES OF GUNITING ? Following are the advantages of guniting The high compressive strength is obtained. Strength of about 56 to 70 n/mm 2  at 28 days is generally obtained. The high impermeability is achieved. The repairs are carried out in any situation in a short time