OCR Text |
Show WATER ESSENTIAL IN CURING ROADS While as little water as possible should be used for the mis in highway construction, it Is essential that a sufficient suf-ficient quantity be used for curing. An important Item therefore in the construction of good quality pavements Is water In quantities to meet the needs of the contractor. That this supply may' always be available, It Is advisable for the inspector to satisfy himself that the pumping equipment and pipe line Is adequate for all requirements. re-quirements. Water is needed for three primary purposes: Wetting the subgrade, mixing mix-ing the material, and curing the pavement. pave-ment. The quantity required naturally natural-ly varies with the progress made, weather conditions and other factors peculiar to each job. In general, a supply of from 12,000 to 15,000 gallons per day for each 100 lineal feet of 1S-foot 1S-foot pavement constructed will be sufficient. suf-ficient. This is assuming an equivalent equiv-alent depth of about one inch for curing and wetting the subgrade and a maximum amount for mixing water of eight gallons for each bag of cement ce-ment used. The total quantity required re-quired for each 100 lineal feet of 18-foot 18-foot pavement will, therefore, be approximately ap-proximately 300 gallons for wetting subgrade, 2,200 gallons for mixing, and 10,000 gallons for curing (assuming a specified curing period of 14 'days). For each additional 100 feet of progress prog-ress an equal amount will be needed. The rate at which the supply is to be delivered depends upon the speed with which the pavement is being placed. Few contractors require more than 50 gallons per minute and this amount is usually "ample for the average job. The size and length of the pipe line is as much a factor in determining the rate at which water will be delivered as Is the pumping equipment. A table of friction heads for various size pipes will show, for example, that a new 2-inch pipe delivering 50 gallons per minute has a friction head of 5.6 feet for each 100 feet of length, while a 2-inch pipe delivering the same amount of water has a friction head of only 1.S6 feet' per 100 feet of length. For old, rusted pipe, from 25 to 50 per cent should be added to the friction loss and allowance must be made for fittings and angles. Generally, a pipe line having a friction fric-tion head of more than 5 feet per 100 feet of length will be uneconomical and a larger pipe should be substituted. A long pipe line with a high friction head imposes a heavy duty on the pumps and it is frequently necessary to install a booster pump along the line when the available pipe line is of small diameter. By making a study of this important subject of water supply for a job, the inspector can often render valuable assistance to the contractor and guard against delays and unpleasantness due to lack of water for curing. |