OIL-MIXED PORTLAND CEMENT CONCRETE. 11 



solution should be left on not longer than half an hour, 'when it 

 should be completely removed with clean water. The surface should 

 then be brushed with a wire or stiff scrubbing brush to remove any 

 particles of sand which may have become loosened because of the 

 dissolving of the cement. 



A mortar composed of 1 part of cement and 2 parts of sand and 

 containing 5 per cent of oil will be sufficiently nonabsorbent for the 

 new wearing coat. To strengthen the bond it will be well to apply a 

 wash of grout, made by mixing cement with water to the consistency 

 of cream, before laying the oil-mixed mortar coat. For the ordinary 

 basement floor a 1-inch layer of mortar will prove of sufficient thick- 

 ness. It will be necessary to keep the new mortar damp for at least 

 one week in order that it may attain its proper strength. 



CELLAR WALLS. 



The entrance of moisture through the walls is another common 

 source of damp basements. The water pressure in the soil adjacent 

 to the wall is very seldom of great magnitude, so that a material 

 nonporous and at the same time impermeable under moderate pres- 

 sures is the logical one to use for this type of construction. 



A concrete mixture in the proportions of 1 part of cement, 2\ 

 parts of sand, and 5 parts of gravel or broken stone, together with 10 

 per cent of oil based on the weight of cement in the mixture, should 

 prove amply rich for most situations. A wall of these proportions, 

 12 inches thick and provided with a spread footing, will withstand 

 a pressure of 6 feet of earth. When supported at the top by floor 

 joists, a much thinner wall may be used with safety. A 6-inch wall 

 7 feet high may be used to withstand 6 feet of earth pressure. Gen- 

 erally speaking, such a thin wall should be reinforced by deformed 

 steel rods spaced about 2 feet apart in both directions. Any of the 

 many types of deformed bars, made especially for reinforcing, may be 

 used with perfect results. Care should be taken that the earth is not 

 filled in against the back of the wall for at least four weeks after pour- 

 ing the concrete, unless the wall is braced on the inside by allowing 

 the inner forms to remain in place. 



Many basement walls now built of stone, brick, or concrete are 

 giving trouble through leakage. The application of a plaster coat 

 of oil-mixed mortar composed of 1 part of cement, 2 parts of sand, 5 

 per cent of oil, and enough water to form a rather stiff mortar, will 

 prove an efficient remedy for this trouble. The surface to which this 

 mortar is to be applied should be roughened with a stone hammer, if 

 the old wall is of concrete, or the mortar joints should be raked out to 

 a depth of half an inch from brick or masonry walls. The acid wash 

 previously described should be applied to cleanse the surface thor- 

 oughly, after which the loose particles must be removed with a wire 



