WOOD-BLOCK PAVEMENT
66. Foundation.—The instructions relating to the preparation of the sub-foundation and the concrete foundation already given apply to wood-block pavement.
67. Inspection of Blocks.—However carefully the lumber may have been inspected before its manufacture into blocks, the subsequent seasoning, treatment, handling and exposure to the weather will develop many defects and you will need to observe the delivered blocks closely, either before or after they are set, and reject those that do not comply with the specifications. The principal defects that you will be able to detect after the blocks are treated are the following: Southern pine blocks made of second-growth or inferior wood, partly shown by the number of annual growth rings per inch. Blocks having a less number of these annual growth rings per inch than is permitted by the specifications should be rejected. The treated blocks, especially when they are exposed to the weather for some time, are likely to develop seasoning cracks, “shakes” and loose knots, not observable in the lumber, and blocks showing these to an injurious extent should be rejected, though in many cases the defective part may be split off and the remainder of the block used for closers. If the blocks have become very dry and thoroughly seasoned out, they should be well sprinkled with water about twenty-four hours before they are to be set, to forestall excessive swelling and “humping” when a rain storm comes upon the new pavement.
68. Mortar Bed.—It is the common practice in preparing the mortar for the mortar bed under the blocks to simply dampen the mixed sand and cement so that it may still be spread and handled like damp sand. See that sufficient water is used to make a moderately stiff mortar, suitable for being worked with a trowel. This mortar should be prepared in sufficiently small quantities at a time to insure that it will not begin to set before the blocks be placed in it and rammed.
69. Setting the Blocks.—The setting of the wooden blocks is a comparatively simple operation and the specifications are sufficiently full and clear for your guidance. See that the blocks are so set that their tops, after the ramming is completed, shall be truly in the pavement datum, without humps or depressions.
70. Filling the Joints.—See that the sand used is perfectly dry, fine and clean, and that it is swept about on the pavement until the joints are completely filled.
BITUMINOUS CONCRETE PAVEMENT
71. Preparation of Foundation.—Where a bituminous concrete wearing surface is to be placed upon an old pavement or Macadam road the specifications must be closely followed. A good foundation is as necessary, if good results are to be attained, as in the case of other pavements. The dressing down of high points and the filling up of depressions in the old pavement should be carefully done, so that the bituminous wearing surface shall be of uniform thickness, and shall be rigidly supported at all points.
72. Bituminous Concrete Surface.—The instructions given for the manufacture and laying of sheet asphalt pavement should be followed here insofar as they are applicable.