The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
First Aid For The Ailing Houses
FAILURES IN CONCRETE
Concrete will fail when too much sand is used in proportion to the cement, when the same is mixed with clay, loam, or other impurity, when mixing is not complete, when so much time elapses after mixing that the concrete begins to set before it is poured or placed, when the mixture freezes before it sets, or when the concrete is allowed to dry before the chemical action of setting has taken place.
Concrete will fail by dusting or brushing off in sand and powder and by chipping and flaking. A common fault in a floor is the continued appearance of dust when sweeping. This can be prevented by a chemical treatment to harden the concrete and bind the particles. Dusting can be prevented by soaking the concrete with 1 part water glass (sodium silicate) and 4 parts water. Enough should be made so that it can be poured on liberally; it should be spread with a broom, and the floor allowed to take up all that it will. Puddles that remain after soaking tor an hour or two should be wiped up. It may be necessary to apply a second treatment 24 hours later.
A floor treated with water glass, however, cannot subsequently be painted; for the paint will not penetrate suificiently to secure a good bond. For this purpose a prepared liquidcement hardener can be used instead. (Conq-R-Dust is very good.) It a dusting floor is to be painted, use should be made of one of the limeproof paints already mentioned. Waxing will also prevent dusting. A liquid wax should be used, as it will penetrate more deeply than paste wax; after a period for drying, rubbing should follow.
When chips and sand fall from the face of a wall, or when cement stucco washes off in a rain, the surface should be brushed or picked to learn whether the fault is shallow or goes through. If the concrete is sandy and loose for the entire thickness, it cannot be given strength; the best remedy is to replace it with new. Usually the fault will be shallow. In making a repair, the loose particles should be removed with a wire brush; the surface so exposed is roughed with a chisel or pointed hammer if necessary. Then the old concrete is soaked with water, brushed with a mixture of cement and water to the consistency of thick paint, and a 1/4-inch coat of mortar immediately applied, the mixture being 1 part of cement and 3 parts of sand. When set, but before there has been time for drying out, a second, and then a third coat of the same mixture are applied.
