REPAIR OF CONCRETE MEMBERS

Gohel Prithviraj K.

What is repair?What is repair?The main purpose of repair is to bring back the

architectural shape of the building so that all services start working and the functioning of building is resumed quickly.◦The repairing of concrete members done by following methods:

1. Grouting

2. Guniting or Shotcrete

3. Epoxy injection

4. Jacketing

Grouting Topic – 1

What is Grouting?What is Grouting?◦Grouting is the process of placing a material into cavities in concrete or masonry structure for the purpose of increasing the load bearing capacity of a structure, restoring the monolithic nature of a structural member, filling voids around pre cast connections steel base plates, providing fire stops, stopping leakages, placing adhesives and soil stabilization.

◦Grout is a mixture of water, cement and optional material like sand, water reducing admixtures, expansion agents and pozzolans. The water to cement ratio is around 0.5. Fine sand is used to avoid segregation.

Procedure of groutingProcedure of grouting◦A 1:2 cement-sand grout with a water-cement ratio between 0.6 and 0.8 is prepared using a mechanical mixer.

◦The mixture is then sent down under pressure (of about 120kg/cm²) through a 30-50 mm diameter pipe terminating into steel cages.

◦As the grouting proceeds the pipe is raised gradually upto a height of not more than 60 cm above its starting level after which it is withdrawn and placed into the next cage for further grouting by the same procedure.

◦After grouting the whole area for a height of about 60 cm , the same operation is repeated, if necessary , for the next layer of 60cm and so on.

Grout mixer:

Guniting Topic – 2

What is Guniting?What is Guniting?◦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 .

◦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/cm2.

Conti….Conti….◦Guniting is extensively used to rehabilitate concrete bridges, dams, spillways, buildings, marine structures, swimming pool, tanks, etc.

◦There are two different methods of spraying:◦Dry process spraying◦Wet process spraying

Gunite Mixer:Gunite Mixer:

Use of guniting:Use of guniting:

Use of guniting:

A well furnished guniting:A well furnished guniting:

Epoxy injection Topic – 3

Epoxy-Injection:Epoxy-Injection:◦Epoxy compounds are having very good compressive, tensile and bond

strength. They can be used for preparing repair mortars but if used as a bonding/binding material for concrete, the cost is prohibitic.

◦Due to bad temperature compatibility, they can not be used on concrete specially for external application. The use of epoxies on wet structures require special grade of epoxies, which are much costlier than the normal epoxy compounds.

◦The technique generally consists of establishing entry and venting ports and close intervals along the cracks, sealing the crack on exposed surfaces, and injecting the epoxy under pressure.

◦Epoxy injection has been successfully used in the repair of cracks in buildings, bridges, dam and other types of concrete structures.

Jacketing Topic – 4

Concept of Jacketing:Concept of Jacketing:◦Jacketing of RCC members increase its size significantly. This has

advantage of increasing the member stuffiness and is useful where deformations are to be controlled.

◦Jacketing of slender RCC column in a building provides a better solution for avoiding buckling problems.

◦Design for strengthening is based on composite action between the old and new work.

◦As the new jacket is to behave compositely with the parent member, the new jacket can take additional load only with the increase in the stresses and strains in the old concrete.

◦Jacketing is done to improve the load carrying capacity of the member.

Thank You.....