Surface Treatments of Concrete

Treatment of porous concrete with sodium silicate (water glass):  Surfaces of porous concrete or concrete of poor quality produce harmful dust due to abrading action. Treatment with silicate of soda hardens the surface by forming a glassy substance and increases wear existing properties. It is the cheapest, simplest, and most effective method. Sodium silicate is a colorless liquid. It is diluted with four times its own volume of water, well stirred, and the solution sprayed over the surface with watering can and brushed evenly with a soft broom. 

The solution may be applied in three or more coats, each coat is allowed to dry for 24 hours before the next coat is applied.  Scrubbing each coat with water after it had hardened  provides a better condition for the application of succeeding coats. If the surface is very porous, or for water retaining structures where greater protection is required, stronger solutions may be used with 1 to 3 (silicate to water) for the second coat and 1 to 2 for the third coat. For average concrete, 25 litres of the diluted solution will be sufficient for about 100 sq. metres.  The surface of concrete to be treated must be thoroughly cleaned of any grease or dirt and dried after completion of the curing period before the solution is applied. 

In 41 cases where surface treatment is to be applied the concrete must be hard, dense and water-height since the destructive effect will be much greater if corrosive liquids are able to penetrate the concrete. The following materials may also be used. 

Boiled Linseed Oil: Best results are obtained when the oil is applied hot. Two or three coats should be given and each coat must be dry before the next is applied. Raw linseed oil should not be used. 

Varnishes: Any vanish can be applied to dry concrete.  Two or more coats should be applied. 

Bituminous or coal tar paints, tar and pitches-various  proprietary brands are available for cold application like ordinary paint.  The concrete must be absolutely dry, clean and dust free.  Such paints arc usually applied in two coats, a thin priming coat to ensure bond and a thicker finish coat.