A reinforced concrete water-tank, 10 feet inside diameter and 43 feet high, designed and constructed by W. B. Fuller at Little Falls, N. J., has some remarkable features. It is 15 inches thick at the bottom and 10 inches thick at the top. The tank was built in eight hours, and is a perfect monolith, all concrete being dropped from the top, or 43 feet at the beginning of the work. The concrete was mixed very wet, the mixture being 1 part cement, 3 parts sand, and 7 parts broken stone. No plastering or waterproofing of any kind was used, but the tank was found to be absolutely water-tight. although the mixture used has not generally been found or considered water-tight.
At Attleboro, Mass., a large reinforced concrete star• Ipipe, 50 feet in diameter, 10G feet high from the inside of the bottom to the top of the cornice, and with a capacity of 1,500,000 gallons, has been constructed, and is in the service of the water works of that city. The walls of the standpipe are 18 inches thick at the bottom, and 8 inches thick at the top. A mixture of 1 part cement, 2 parts sand, and 4 parts broken stone, the stone varying from f inch to 12 inches, was used. The forms were constructed, and the concrete placed, in sections of 7 feet. When the walls of the tank had been completed, there was some leakage at the bottom with a head of water of 100 feet. The inside walls were then thoroughly cleaned and picked, and four coats of plaster applied. The first coat contained 2 per cent of lime to 1 part of cement and 1 part of sand; the remaining lirec coats were composed of 1 part sand to 1 part cement. Each coat was floated until a hard, dense surface was produced; ;then it was scratched to receive the succeeding coat.
On filling the standpipe after the four coats of plaster had been applied, the standpipe was found to be not absolutely water-tight. The water was drawn out; and four coats of a solution of castile soap, and one of alum, were applied alternately; and, under a 100-foot head, only a few leaks then appeared. Practically no leakage occurred at the joints; but in several instances a mixture somewhat wetter than usual was used, with the result that the spading and ramming served to drive the stone to the bottom of the batch being placed, and, as a consequence, in these places porous spots occurred. The joints were obtained by inserting beveled tonguing pieces, and by thoroughly washing the joint and covering it with a layer of thin grout before placing additional concrete.
In the construction of the filter plant at Lancaster, Pa., in 1905, a pure-water basin and several circular tanks were constructed of reinforced concrete. The pure-water basin is 100 feet wide by 200 feet long and 14 feet deep, with buttresses spaced 12 feet 6 inches center to center. The walls at the bottom are 15 inches thick, and 12 inches thick at the top. Four circular tanks are 50 feet in diameter and 10 feet high, and eight tanks are 10 feet in diameter and 10 feet high. The walls are 10 inches thick at the bottom, and 6 inches at the top. A wet mixture of 1 part cement, 3 parts sand, and 5 parts stone, was used. No waterproofing material was used, in the construction of the tanks; and when tested, two of them were found to be water-tight, and the other two had a few leaks where wires which had been used to hold the forms together had pulled out when the forms were taken down. These holes were stopped up and no furthur trouble was experienced. In constructing the floor of the pure-water basin, a thin layer of asphalt was used, as shown in Fig. 10; but no waterproofing material was used in the walls, and both were found to be water-tight.
116. Sylvester Process. The alternate application of washes of castile soap and alum, each being dissolved in water, is known as the Sylvester process of waterproofing. Castile soap is dissolved in water, 4 of a pound of soap in a gallon of water, and applied boiling hot to the concrete surface with a flat brush, care being taken not to form a froth. The alum dissolved in water-1 pound pure alum in 8 gallons of water— is applied 24 hours later, the soap having had time to become dry and hard. The second wash is applied in the same manner as the first, at a temperature of 60° to 70° F. The alternate coats of soap and alum are repeated every 24 hours.
Usually four make an impervious coating. The soap and alum combine and form an insoluble compound, filling the pores of the concrete and prevent ing the seepage of water. The walls should be clean and dry, and the temperature of the air not lower than 50° F., when the composi tion is applied. The composition should be applied while the con crete is still green. This method of waterproofing has been used extensively for years, and has generally given satisfactory results for moderate pressures.