MAINTENANCE OF STONEWORK

Maintenance of stonework involves in removing efflorescence and stains, repair of cracks and waterproofing.

Removal of Efflorescence in Stonework

Appearance of efflorescence occurs commonly due to use of certain type of mortars. Removal of efflorescence has to be done as done in brickwork. Stones are to be kept saturated with water to remove the action of acids.

Removal of Stains in Stonework

Removal of stains can be done easily if its origin is known. Iron stains show rusty appearance which can be removed by rinsing the area with a solution of ½ kg oxalic acid in 5 l of water. After 2–3 hours, the surface should then be scrubbed with brush and clean water.

Darker stains may be removed with six parts of water, one part of sodium citrate and one part of glycerine, made into a paste with adequate whiting. This paste is applied on the surface and then kept for a few days.

For very deep and dark stains, one part of sodium citrate is mixed with six parts of water. This solution is applied on the surface of stains. This is followed by covering the surface with a thin layer of sodium hydro-sulphite crystals and removed after an hour. This may be repeated if needed.

Repair of Cracks in Stonework

Repairing of cracks has to be attended by ensuring that the settlement causing the crack has ceased. This generally takes about one year for the complete settlement.

Small cracks are cleaned with a wire brush and a thick paste of cement mix is forced into the crack. In order to get a firm key for the mortar, large cracks should be raked. An inverted V groove is made with a minimum of 1 cm depth. A cement mortar of 1 : 2 ratio is applied with less water. The mixture is forced into the crack to get a firm bond. Along with this mixture expansive agents are added to improve the bond.

Waterproofing of Stonework

In order to keep the stone masonry free from damp, efflorescence, frost action, etc., colourless waterproofing materials is applied waterproofing materials obtained from heavy petroleum distillates, oils or in soluble soaps are best. It is difficult to waterproof very closely textured stones. Waterproofing materials substances containing resins are not suitable for fine-textured stonework. Waterproofing causes some dislocation which goes from the stones in course of time.