The contractor may employ any of the standard methods in common use for impregnating the blocks, provided that uniform results are attained, complying with the following requirements:
The wood shall not be heated during any part of the process to a temperature exceeding two hundred and sixty degrees Fahrenheit (260° F.).
All parts of every block shall be reached and penetrated by the oil. The quantity of oil found in the blocks after treatment shall average not less than ... pounds per cubic foot of wood.
The oil in the treating tanks during the process of impregnation shall not become diluted with water to the extent of more than five per cent. (5%) and if the percentage of water in the oil during the process of treatment shall exceed two per cent. (2%) the quantity of the oil to be injected in the wood as stipulated hereinbefore shall be increased in a like ratio; for example, if the oil in the treating tanks shall be found to contain four per cent. (4%) of water the quantity required to be found in the blocks after treatment shall be four per cent. (4%) greater than herein specified.
The quantity of oil injected shall be determined primarily by tank measurements, but shall be verified by actual determination of the quantity of oil in the treated blocks by the following method: representative treated sample blocks shall be selected and an auger hole one inch in diameter bored entirely through the block parallel to the fiber, the borings all collected, thoroughly mixed, and the quantity and ratio of oil to wood in the borings determined by extracting the oil completely with carbon di-sulphide. The center of the auger hole shall be located midway between the sides of the block and at a distance from the end of the block equal to one-third (⅓) of the length of the block. At the time of treatment the blocks shall not be green or saturated with water, but they shall, preferably, not be thoroughly seasoned. After treatment, and until used, the blocks shall, during dry weather, be frequently well drenched with water to prevent excessive drying out and cracking.
97. Laying the Wood-Blocks.—The concrete foundation shall be cleaned and swept to remove all dirt and débris and shall be thoroughly dampened immediately in advance of the setting of the blocks. Upon the concrete foundation shall be spread a layer of mortar about one-half inch thick, made of one part Portland cement and two parts sand with sufficient water to make a moderately stiff paste.[[54]] The mortar shall be thoroughly mixed and shall be spread in place over the concrete foundation immediately in advance of setting the blocks to such a thickness that when the blocks are set and properly tamped their tops shall conform accurately to the pavement datum.
Upon this mortar bed the blocks shall be set with their fiber vertical, in straight, parallel courses at right angles to the axis of the street, except at street intersections where they shall be set at an angle of forty-five degrees with the axis of the street. The blocks shall be set as close together as practicable. Blocks in adjoining courses shall break joint at least three inches. Blocks of such lengths shall be selected as to make as little splitting as practicable in filling out ends of courses. Where splitting is necessary, no fractional block shall be used whose length is not at least equal to its width.
After the blocks are thus set the whole surface of the pavement shall be rammed with a rammer weighing not less than twenty pounds, a plank ten (10) inches wide, two (2) inches thick and four feet long being interposed between the rammer and the pavement and moved about as the ramming progresses until the blocks are forced into a firm seat in the mortar bed and their tops brought accurately to the pavement datum. The ramming shall be completed before the mortar under them has begun to set, but no ramming shall be done, during the progress of the work, nearer than three feet to the edge of the block setting, except where the block setting may be suspended, as at the end of the day’s work, when all the blocks then set shall be rammed.
The top surface of the pavement when completed shall conform so truly to the pavement datum that correctly formed templates twelve (12) feet long applied to the surface shall show at no place a departure of more than three-sixteenths (³⁄₁₆) inch therefrom.
98. Filling the Joints.—After the block setting is completed, perfectly dry, fine sand shall be spread over the pavement surface and swept about until every joint into which the sand will penetrate shall be completely filled. The remaining sand shall be left upon the pavement for such time as the Engineer may direct, when it shall be removed by the Contractor.[[55]]