Sylvester Wash.—Waterproofing with Sylvester wash consists in applying alternately to the concrete surface a soap solution wash and an alum solution wash. The soap solution is applied first, and it must be applied hot and to a dry surface; the alum solution is applied second and 24 hours after the soap solution and is applied cold. This constitutes one treatment. After 24 hours a second treatment may be given, and as many treatments may be given as necessary. In some cases as many as six treatments have been employed. The proportions of the solutions used in practice vary. In waterproofing the standpipe described in Chapter XXII the soap solution consisted of 12 oz. pure Castile olive oil soap per gallon of water, and the alum solution consisted of 2 oz. of alum per gallon of water. In repairing the bottom of a reservoir lined with 4 to 6 ins. of concrete the following solutions were used: ¾ lb. Olean soap to 1 gallon of water and ½ lb. alum to 4 gallons of water. Both alum and soap were well dissolved and the soap solution was boiled. The boiling hot soap solution was applied on the clean, dry concrete; 24 hours later the alum wash was applied cold. This treatment was repeated after 24 hours. Two men applied the solutions, using whitewash brushes, while a third man carried pails of the solution. In making the soap solution two men attended four kettles, one man kept up fires, two men carried solution to men applying it. The alum solution required fewer men, being made cold in barrels. After applying the second soap wash to the concrete slopes, the men had to be held by ropes to keep from slipping. The rope was placed around two men, who started work at the top of the slope, a third man paying out the rope. The work was done in 8½ days and cost as follows:
| Labor: | |
| 1,140 hours labor at 15 cts. | $171.00 |
| 83 hours foreman at 30 cts. | 24.90 |
| 83 hours waterboy at 6 cts. | 4.98 |
| Add for superintendence 15% | 30.13 |
| ——— | |
| Total labor | $231.01 |
| Materials: | |
| 900 lbs. Olean soap at 4⅓ cts. | $ 39.00 |
| 210 lbs. alum at 3 cts. | 6.30 |
| 6 10-in. whitewash brushes at $2.25 | 13.50 |
| 6 stable brushes at $1.25 | 7.50 |
| ——— | |
| Total materials | $ 66.30 |
| Total labor and materials | $297.31 |
This covered 131,634 sq. ft., hence the cost of the two coats of soap and alum was $2.26 per 1,000 sq. ft., or 0.23 ct. per sq. ft.
The ordinary Sylvester wash, as described above, has been modified with success on Government fortification work as follows: To 2 gals. of water add 1 lb. concentrated lye and 5 lbs. alum and mix until completely dissolved. This is a concentrated stock solution. In use 1 pt. of solution and 10 lbs. of cement are mixed with enough water to make a mixture that will lather freely under the brush. Two coats of this wash are applied, the second at any time after the first is dry, and the first as soon as the forms are removed from the concrete. The wash should be applied to a wet surface, if the concrete is dry it should be wet down with a brush ahead of the wash.
Sylvester Mortars.—In this class of coatings the alum and soap are added to the mortar which is used for facing. A successful recipe for such a mortar is given as follows: To 1 part cement and 2 parts sand add ¾ lb. of pulverized alum for each cubic foot of sand and mix these ingredients dry; then add the proper quantity of water, in which has been dissolved ¾ lb. of soap to the gallon, and mix the mortar thoroughly. Such a mortar is but slightly inferior in strength to ordinary mortar of the same proportions. In plastering a clear water well to prevent leaking a 1-2 mortar was made as follows: 1¼ lbs. of soap were dissolved in 15 gallons of water and 3 lbs. of powdered alum were mixed with 1 bag of cement. Two coats of plaster of an aggregate thickness of ½ in. were applied and completely stopped the leaking. The cost of this treatment was as follows:
| 2 lbs. soap (with 24 gals. water) at 7½ cts. | $0.15 |
| 12 lbs. alum at 3½ cts. | 0.42 |
| ——— | |
| Total per barrel of cement | $0.57 |
In lining a new reservoir near Wilmerding, Pa., a mortar was made as follows: A stock solution of 2 lbs. caustic potash and 5 lbs. alum to 10 quarts of water was made in barrel lots, from which 3 quarts were taken for each batch of 2 bags of cement and 4 bags of sand. A batch of mortar covered an area 6×8 ft. with a 1-in. coat. The extra cost of the waterproofing was:
| 100 lbs. caustic potash at 10 cts. | $10.00 |
| 70 lbs. caustic potash at 9 cts. | 6.30 |
| 960 lbs. alum at 3½, 3¾ and 4 cts. | 34.38 |
| 60 hours mixing at 15 cts. | 9.00 |
| Freight, express and haulage | 11.50 |
| ——— | |
| Total for 74,800 sq. ft. | $71.18 |
This gives a cost of 95 cts. per 1,000 sq. ft., or less than 0.1 ct. per sq. ft. It was found that if less than 2 parts of sand to 1 part of cement was used the mortar cracked badly in setting. Clean sand was imperative, as any organic impurities soon decomposed, leaving soft spots. Do not use an excess of potash; a slight excess of alum, however, does not decrease the strength of the mortar.
Hydrolithic Coating.—This waterproofing is a dry mortar composed by mixing a cementing compound with sand, and sold dry in sacks containing 96 lbs. each. The dry mortar is mixed with water to proper consistency for plastering, and is applied as a plaster to the surfaces to be waterproofed. The dry mortar is mixed with water to a grout of the consistency of thick cream and then this grout is stiffened to the proper consistency by adding more dry mortar. Thoroughness of mixing is absolutely essential. The concrete surface is prepared by picking and scoring sufficiently to get a fresh surface and washing away all chips, dust and loose material, or instead of picking in new work the outer skin may be removed by a 1 to 9 muriatic acid solution and then washed free of all acid and scrubbed with wire brushes. After preparing the fresh surface it is well wetted; in fact water soaked, so that, while not oozing moisture it will absorb no more water. The mixed mortar is then applied with a trowel in a workmanlike manner. In mixing, no more than 8 gallons of water per barrel of mortar should be used. The coatings used are ⅜ to ⅝ in. for walls and ½ to ¾ in. for floors. The following estimate of cost is made by the manufacturers, the E. J. Winslow Co., Chicago, Ill. The figures are presented with the understanding that they are to be considered merely as average costs for waterproofing, without special construction, and subject to change in accordance with local conditions, and to the time of year when the work will need to be performed: