WOOD-BLOCK PAVEMENT
92. Sub-grade.—The sub-grade for wood-block pavement shall be prepared as specified in Section 26, and shall be finished to a surface ... inches below the pavement datum.
93. Foundation.—The foundation for wood-block pavement shall be Portland cement concrete ... inches thick, prepared as specified in Sections 28, 29, 30, 31, 32, 33, 34, 35, 36 and 37. The upper surface of the concrete foundation, when completed, shall be at a distance below the pavement datum equal to the depth of the blocks to be laid, plus one-half (½) inch, and must not vary more than one-fourth (¼) inch above or below that depth.
MATERIALS
94. Wood-blocks.—The wood-blocks may be made of Long-leaved yellow pine (Pinus palustrus), Lob-lolly pine (Pinus tæda), Short-leaved pine (Pinus echinata), Cuba pine (Pinus heterophylla), Black gum (Nyssa sylvatica), Red gum (Liquidambar styraciflua), Norway pine (Pinus resinosa), or Tamarack (Larix laricina), or of other species of wood of equal strength and toughness and of a texture permitting as satisfactory preservative treatment as those herein named. But, as far as practicable, only one species of wood shall be used on any one contract.[[51]]
Only wood from live, sound trees shall be used. The lumber from which the blocks are cut shall be properly manufactured, free from bark, and with full square corners. It shall be free from decay, dottiness, brashness, shakes, large season cracks, loose or unsound knots over three-fourths (¾) inch in diameter, and all other imperfections which may, in the opinion of the Engineer, be detrimental. “Fat” pine containing so much resin that it will not take up the specified quantity of creosote oil in treatment may be rejected. Second-growth timber, and Southern pine showing, outside of a radius of three (3) inches from the heart, nine (9) or less annual growth rings to the inch, will not be accepted.
The paving blocks made from the lumber hereinbefore specified shall be well manufactured and truly rectangular and square edged. Their depth (parallel to the fiber) shall be ... inches,[[52]] their length shall not be less than six inches nor more than three times their depth, and their width shall be from two and one-half (2½) to three and one-half (3½) inches, but at least one-fourth inch less than their depth.
All the blocks for any one contract shall be of the same standard depth and width, and the individual blocks shall not vary more than one-eighth inch from the designated depth and width.
95. Creosote Oil.[[53]]—The oil used for the preservative treatment of the paving blocks shall be coal-tar creosote oil, commonly known as dead oil of coal-tar, without admixture or adulteration with other oils or tars. Oils produced or resulting from the distillation of water-gas tar, blast-furnace tar, producer-tar, lignite-tar, petroleum-oil tar, or wood-tar, or, containing an admixture of any of these will not be accepted. The creosote oil shall not contain more than five per cent. (5%) of tarry matter nor more than two per cent. (2%) of water. Its specific gravity at a temperature of 100° F. shall be not below 1.03 nor above 1.08. Not less than ninety-nine per cent. (99%) shall be soluble in hot benzol. It shall not contain more than eight per cent. (8%) of tar acids. When two hundred (200) grams are subjected to distillation at gradually increasing temperatures, not more than five per cent. (5%) of distillate shall distil over up to a temperature of four hundred degrees F. (400° F.), nor more than thirty-five per cent. (35%) shall distil over up to a temperature of four hundred and fifty-five degrees F. (455° F.), and not more than eighty per cent. (80%) shall distil over up to a temperature of six hundred degrees F. (600° F.). After complete distillation there shall not remain more than two per cent. of coke. The residue remaining, upon sulphonating a portion of the total distillate, shall not exceed one per cent. (1%). The above tests shall be made in accordance with the methods prescribed in the “Report of the Committee on Preservative Treatment of Poles and Cross-arms” of the National Electric Light Association, 1911.
96. Preservative Treatment.—The paving blocks shall, after they are cut to the proper dimensions, be subjected to preservative treatment with the creosote oil specified in Section 95.