Chapter VII: Part I: Specifications for Street Roadway Pavements (4)

The sand shall be clean, sharp silicious sand made up of grains of such size that not more than fifteen per cent. (15%) will pass a number thirty (30) sieve. It shall not contain more than five per cent. (5%) of clay or loam nor more than two per cent. (2%) of organic matter or other refuse. The stone shall be sound, hard, durable, and freshly broken, free from clay, loam, organic matter, or other impurities. Trap rock or granite will be preferred, but limestone, if hard and sound, may be used with the approval of the engineer. Only those fragments of the crushed stone that pass a screen with openings three-fourths inch square and those that are held on a screen with openings one-fourth inch square shall be used in the concrete.

=131. Mixing and Placing Concrete.=—The concrete shall be mixed in accordance with Section 35 of these specifications. Very thorough mixing will be required.

The mixed concrete shall be handled so as to prevent as far as practicable any separation or segregation of the stone and mortar. When in place it shall be compacted by tamping and where placed against forms, forking or other effective means must be used to bring mortar to the surface and to secure complete contact between mortar and forms, so as to leave a solid, homogeneous and unbroken surface when the forms are removed. Where the concrete may not be laid against forms, all exposed surfaces must be troweled to a true surface conforming accurately to the lines shown by the plans, templates and straight-edges being used where necessary.

=132. Weather.=—Concrete in combined curb and gutter shall not be laid in freezing weather nor shall frozen materials be used in the work. Completed work must be securely protected from frost for at least seven days after it is laid. Any concrete curb and gutter that may become frozen within that period shall be wholly removed and replaced with new work.

=133. Expansion Joints.=—The combined curb and gutter shall be divided into blocks or panels not more than twelve feet long, by clear, open expansion joints perpendicular to the face of the curb, extending entirely and continuously through the whole mass of the concrete. These expansion joints shall be three-eighths inches wide and may be formed either by cutting through the completed curb and gutter with a suitable tool, or by the use of iron forms or partitions, but in either case the corners at the ends of the blocks must be made solid and dense and troweled with a suitable tool.

=134. Circular Corners.=—At the intersections of streets, circular corners, having a radius equal, generally, to one-fifth of the width of the roadway of the narrower street, shall be constructed of the same dimensions and quality as on the body of the street, and the curb and gutter will be extended along the line of the cross street back to the front lot-lines. Properly curved circular curb and gutter shall also be constructed at all angles exceeding five degrees in the line of the curbing.

=135. Corner Protection.=—Galvanized steel corner protectors or nose-pieces shall be used to protect the upper and outer corner of the curb at all circular corners and angles in the street. This steel protection may be of any pattern or section procurable in the market and approved by the engineer. It shall be firmly anchored and secured into the concrete.

=136. Finishing.=—After the forms have been removed and before the concrete has set up too hard to be affected by the brush, the face and top of the curb shall be lightly scrubbed by a suitable wire brush so as to completely remove any glazed surface and to produce a surface of uniform texture and appearance. Dry cement or neat cement mortar shall not be used for dressing up exposed surfaces.[77]

=137. Forms.=—The forms used may be of dressed lumber or of metal as the contractor may prefer. But they shall have sufficient strength and rigidity to hold the concrete firmly in place, and to preserve the correct dimensions, alignment and levels of the curb and gutter.

=138. Protection.=—The completed curb and gutter shall be protected from fracture, deformation or spalling until the concrete has fully set. The concrete must be kept moist for at least five days after it has been laid. Any part of the curb and gutter that shall have become injured before it is accepted or the street is opened for travel shall be taken up and replaced by the contractor.

=139. Payment.=—Concrete combined curb and gutter will be paid for by the linear foot in place, the measurement to be made along the upper and outer corner of the curb. The price per linear foot named in the contract will cover all the excavation or grading required and all the materials and labor, including all necessary forms, for constructing the curb and gutter complete. But the crushed stone used for drainage will be paid for by the cubic yard measured in place, and steel corner protection will be paid for by the linear foot in place, at the prices named in the contract.

HYDRAULIC CONCRETE SIDEWALKS

_Note._—These specifications conform to the common practice of laying the sidewalk in two courses.

In the author’s judgment this is neither necessary nor desirable. He believes that it would be better and somewhat cheaper to use a single course of concrete four inches in thickness. He suggests for this concrete the ratios of one cement, two sand, and three and one-half stone, the latter to be crushed to pass a screen with five-eighths inch square openings.

Tamping will bring a sufficient quantity of mortar to the surface to permit of satisfactory finishing. While the materials for such a single course of four inch concrete would cost somewhat more, the saving in cost of labor would, at usual prices of material and labor, make the single-course construction somewhat cheaper, while the solid four inches of richer concrete would make the walk much stronger. In fact, a single course of such concrete three inches thick would be sufficient in a great majority of cases. While the surface might not have the glazed appearance common in the two-course work it would be really better for use—a polished and slippery surface on sidewalks is not desirable.

SPECIFICATIONS[78]

=140.= The hydraulic concrete sidewalk shall be ... feet in width and its outer edge shall be ... feet from the outer face of the street curbing. It shall be constructed with two courses of Portland cement concrete as hereinafter specified.

=141. Excavation and Grading.=—The ground to be occupied by the sidewalk shall be excavated or filled to a sub-grade which after being compacted shall be ... inches[79] below the finished surface of the sidewalk. The sub-grade shall be neatly dressed to a plane surface sloping downward toward the street one-fourth inch in one foot horizontal, and to such longitudinal gradients as the engineer may prescribe. The completed sub-grade shall project four (4) inches in excavation and eighteen (18) inches in embankment on each side beyond the edges of the completed sidewalk. After the grading is completed the surface shall be compacted by rolling or ramming.

=142. Drainage Course.=—Upon the sub-grade prepared as specified in