Concrete structures that are subject to freezing and thawing are likely to corrode earlier. The structures which are mostly affected due to freezing and thawing under similar climatic conditions are exposed surface of top 60 cm walls, piers, parapets, cornices etc. The durability of such structures can be improved by adopting certain weather proofing measures. It has been observed that concrete surface lasts longer if applied with curing compounds, linseed oil, epoxy etc.
Protective measures against weathering are generally not adopted for new concrete surfaces unless they show some signs of deterioration, which is evident from the formation of fine cracks close and parallel to the edges and corners. It is better to treat such surfaces at an earlier stage to avoid uneconomical and difficult repairs later. Concrete must be made waterproof to make it durable against freezing and thawing. The following methods of protection against weathering are known to give good results.
- Oil and paint application
- application of varnish
- Application of chemical solutions
1. Oil and paint application
After curing is complete, new concrete surfaces should be allowed to dry for 1 or 2 weeks before waterproofing treatments are applied. Such new surfaces are brushed with a solution of 40 g of phosphoric acid and 16 g of zinc chloride in one liter of water. This is done to prevent saponification of linseed oil. This treatment is not necessary for older concrete surfaces. The surface must be made clean and dry before waterproofing measures are adopted. After this, apply two layers of linseed oil as mentioned below.
- A mixture of 50% crude linseed oil and 50% turpentine is mixed with 80. is heated to a temperature of0C is applied with a simple brush as a first coat
- Crude linseed oil 80. is heated to0C is applied as a second coat with a normal brush 24 hours after the first coat is applied.
Second Coat After the waterproofing coat is completely dry, the entire treated surface is given standard white lead and two coats of oil paint. Application of paint is essential otherwise the oil treatment already applied will be spoiled. The color of the oil paint should match the color of the concrete surface, for this lamp black or burnt sienna is added to the paint.
If any open cracks in the surface area are to be treated, they should be repaired by first filling the cracks and then brushing the surface with oil.
2. application of varnish
Varnishes are sometimes applied to concrete surfaces that are effective against attacks caused by mineral and vegetable oils. There are various bituminous paints, pitches and mastic available these days. They protect the surface against acid attacks.
3. Application of chemical solutions
Magnesium or Zinc Fluosilicate Solution
Treatment consists of applying two or more coats of compound. For the first coat, a solution of 1 kg of the compound per 10 liters of water is used. For subsequent coats, about 2 kg of compound is used per 10 liters of water. The solution is painted onto the surface and each coat is allowed to dry before the next coat is applied. Finally, the surface is brushed and rinsed with water. This treatment hardens the surface and makes it impervious to chemical action. It protects the concrete against the onslaught of all mineral and vegetable oils, salts and alkalis.
sodium silicate solution
It is a viscous liquid and must be diluted with three times the volume of water. This should also be implemented as above. It is better to rinse with water after each coat has hardened before applying the next coat. Subsequent coats belong to a stronger solution. It also protects the concrete from attacks similar to that of fluosilicate.