When Council has caused curbing to be set on any street or alley, Council may cause to be ascertained the owners of all lots or parts of lots abutting on the sidewalk so curbed, together with the number of feet each lot so abuts, and thereupon may by resolution require each of the owners of such lots or parts of lots to pave the sidewalks abutting upon his lot or part of lot, upon the grade which has been established according to law, and in conformity with and according to the following specifications, except as may be otherwise provided by Council by resolution:
(a) Sampling and Testing Materials. Before delivery upon the job, and at such other times as the engineer deems necessary, the contractor shall furnish any required samples of the materials hereinafter mentioned. Materials shall pass the requirements set forth in this section.
(b) Cement. The cement shall meet the requirements of the current standard specifications for Portland cement of the American Society for Testing Materials. A sack containing ninety-four pounds of cement shall be considered one cubic foot.
(c) Fine Aggregate. The fine aggregate shall consist of clean, hard, durable, uncoated particles of sand or stone, free from all organic material. One hundred percent (100%) of such aggregate shall pass a one-quarter inch screen and ninety-five percent (95%) shall be retained on a 100 mesh screen. Not more than twenty-five percent (25%) shall pass a fifty mesh screen. It shall be well graded from coarse to fine, and shall not contain more than five percent (5%) by weight of clay or loam, none of which shall be in lumps. When the fine aggregate is mixed with Portland cement in the proportion of one part cement to three parts fine aggregate by weight, according to the standard method of making briquets, the resulting mortar at the age of seven and twenty-eight days shall have a tensile strength of at least equal to that developed in the same time by mortar of the same proportions and consistency made of the same cement and standard Ottawa sand.
(d) Coarse Aggregate. Coarse aggregate may be broken stone, gravel or blast furnace slag. The broken stone or gravel shall be clean, hard, durable, uncoated rock. It shall contain no vegetable or other deleterious matter and shall be free from soft, thin, elongated or laminated pieces.
(1) Slag shall be of a quality which has been successfully used in local concrete work. It shall be air cooled, non-glassy and shall have been exposed to the weather at least one year.
(2) One hundred percent (100%) of the coarse aggregate shall pass a one and one-half inch screen and at least ninety-five percent (95%) shall be retained on a one-fourth inch screen, with all intermediate sizes retained.
(e) Water. Water shall be clean and free from alkali, oils or acids.
(f) Joint Filler. Joint filler shall be premolded strips of asphalt or pitch, and fiber or mineral aggregate passing an eighty mesh screen, one-half inch thick, as wide as the thickness of the concrete slab and at least two feet long. It shall have such a consistency that it will not run in summer or chip out in winter.
(g) Forms. Forms shall be of lumber two inches thick, or steel of equal strength, except on curves, where flexible stakes or braces with top edges at true line and grade given by the engineer. Ends of adjoining forms shall be flush. Where sidewalks fill the space between the curb and building lines, forms shall be set to give the walk a slope toward the curb of one-fourth inch per foot of width. If there is an intervening space between the back of the curb and the walk, the edge of the walk shall be set on elevation sufficient to give a slope or pitch of one-half inch per foot.
(h) Division Plates. Where division plates are used they shall be of one-eighth inch steel, as wide as the depth of the slab and as long as the width of the walk. Forms and division plates shall be thoroughly cleaned and oiled each time before they are used.
(i) Subgrade. That portion of the ground surface directly beneath the slab shall be called the subgrade.
(1) All soft and spongy material in the subgrade shall be removed and replaced with suitable material. Fills shall be compacted in layers not exceeding six inches in thickness. Spots previously compacted by traffic shall be loosened to a depth of six inches. The whole subgrade shall be thoroughly and uniformly compacted so a firm surface having as nearly as possible a uniform bearing power.
(2) A template, resting upon the side forms and having its lower edge at the exact elevation of the subgrade, shall be drawn along the forms before any concrete is laid. Any high places in the subgrade shall be removed so that the template will pass over without being raised off the side forms or being tipped at an angle to the sidewalk surface. The subgrade shall be damp, but not muddy, when concrete is placed upon it.
(j) Drains. Where in the opinion of the engineer it is considered necessary to save the walk from damage by frost action, four-inch drain tile shall be laid on the lines given by the engineer, and four-inch Vit tile for downspouts.
(k) Subbase. When drains are impracticable and the soil is poorly drained, colloidal clay or adobe, a five-inch subbase shall be constructed of cinders, gravel or other porous material approved by the engineer. The subbase shall be thoroughly tamped until the surface is firm and shall be drained into the street gutter.
(l) Thickness and Proportions. The sidewalks shall consist of one five-inch course of concrete in the proportion of one part of Portland cement, two parts of fine aggregate and four parts of coarse aggregate. All material shall be accurately measured in a manner approved by the engineer.
(m) Mixing.
(1) The ingredients of the concrete shall be thoroughly mixed until each particle of fine aggregate is coated with cement and each particle of coarse aggregate is coated with mortar. Where a mechanical mixer is used it shall be of an approved batch type. Each batch shall be mixed at least one minute from the time all materials including water are in the drum until the beginning of the discharge.
(2) The consistency of the mixed concrete shall be such that no separation of the ingredients takes place and some tamping is necessary to bring the mortar to the surface.
(n) Placing and Finishing.
(1) The freshly mixed concrete shall be placed immediately on the prepared subgrade. It shall then be struck off and tamped with a straightedge, and having a slope of one-quarter inch per foot resting upon the side forms and advanced with a crosswise sawing motion.
(2) The placing of concrete shall not be suspended for forty-five minutes or longer except at end of slab. No concrete shall be placed on a frozen subgrade when the temperature is, or is liable to be within twenty-four hours, below thirty-five degrees Fahrenheit, except when the written permission of the engineer has been obtained.
(o) Jointing.
(1) The walk shall be cut into separate slabs. No plain concrete slab shall be longer than six feet on any one side. Where division plates have been used they shall be removed when the concrete has hardened sufficiently to avoid breaking the edges or corners of the slab. Where division plates have not been used the partially set concrete shall be cut through to the subgrade. Care should be taken to make the cut at right angles to the surface of the sidewalk.
(2) The surface edges of each slab shall be rounded to a radius of about one- fourth inch. Markings shall be exactly at cuts between slabs.
(p) Expansion Joints. Expansion joints shall extend from the surface to the subgrade, be truly at right angles to the sidewalk surface and made by putting the specified joint filler in place before the concrete. They shall be placed as follows:
(1) At or near all places where the sidewalk line intersected a curb line or other sidewalk, a half-inch expansion joint shall be made at right angles to the center line of the walk.
(2) When the sidewalk fills the space between the curb and the building line a one-half inch expansion joint shall be placed between the curb and the sidewalk and between the sidewalk and the building. A one-half inch expansion joint shall be made across the walk at approximately fifty feet intervals.
(q) Curing.
(1) As soon as the concrete has set sufficiently, it shall be sprinkled and kept moist until covered. As soon as it can be done without damage to the walk, it shall be covered with two inches of earth or sand which shall be kept wet for seven days. The walk shall then be cleaned and opened to traffic.
(2) The contractor shall protect the concrete from damage by rain, pedestrians and animals with suitable covers and barricades and by red lights at night.
(Passed 4-2-63.)