In the construction of cement sidewalks, the following specifications shall be observed and complied with:
   (a)   Foundation.  The foundation of all cement sidewalks shall consist of a layer of gravel or cinders of an approved quality eight inches thick which shall be thoroughly rolled or tamped in place to an even, smooth surface and shall extend three inches on each side of such walk.  Such thickness of eight inches shall be the thickness of the foundation after it has been thoroughly rolled or tamped.
   (b)   Kind of Cement.  All cement used must be Portland cement of known brand, not slag, freshly burned and finely ground, of sufficient strength to stand the required tests, and which shall meet the requirements of the standard specifications for Portland cement, as adopted by the American Society for Testing Materials.
   (c)   Sand.  All sand used shall be the best clean, hard, sharp sand, free from dust, clay, loam, vegetable or other deleterious matter.
   (d)   Gravel or Limestone.  Gravel or limestone screenings must be small enough to permit them to pass through a one-inch ring and shall be free from dirt or other foreign substances.
   (e)   Concrete Base.  The concrete base shall be not less than four inches thick and shall consist of one part cement, two parts sand and five parts gravel or limestone screenings.  The cement, sand and gravel or limestone screenings shall be thoroughly mixed dry; clean water shall then be added and the whole mass shall be turned over not less than four times.  The concrete shall be mixed in boxes prepared specially for the purpose, and each batch shall be carefully put in place and rammed thoroughly until the mortar flushes to the surface.
Before the concrete base is laid, the foundation shall be thoroughly sprinkled or wet and shall be in such condition when the concrete base is laid, but no concrete shall be allowed to be deposited in pools of water on the foundation.
   (f)   Wearing Surface and Finishing.  The top finish or wearing surface shall not be less than one inch in thickness, shall be placed on top of the concrete base as prepared above, and shall be applied within one hour after completion of the bottom.  Such surface shall consist of one part cement and two parts clean, sharp sand.  The sand and cement shall be thoroughly mixed dry and then sufficient water added so that when tampered into mortar and well tamped upon the base water will rise to the surface, after which it shall be "struck off" with a straight edge and floated and troweled to a true finished surface exactly to grade and slope.
   (g)   Roughened Surface.  The top or surface coat of all cement sidewalks shall be finished with a properly roughened surface by using a wooden float or other suitable means upon the same.
   (h)   How Laid.  The sidewalk shall be laid between guide strips securely fastened to grade and line and laid in blocks or sections not more than six feet nor less than four feet square, with a vertical joint between sections extending through the entire thickness of the walk.  The joint shall be made by a strip of paper or equivalent means.  The edges of such blocks at the joints shall be finished and rounded to a radius of one-half inch with the proper type of edging tool.
   (i)   Surface on Certain Grades.  Wherever cement sidewalks are laid on a street having a grade of six percent or more, the wearing surface, after the same has sufficiently set or hardened, shall be broomed over with a wire tooth broom or brush to roughen the surface, and the marking shall be done in straight lines across each slab or block in a workmanlike manner.
   (j)   Name of Contractor.  All sidewalks must bear at least one imprint or name plate of the contractor doing the work.
   (k)   Protection.  As soon as the concrete has hardened sufficiently to prevent being pitted, the surface of the sidewalk shall be sprinkled with clean water, and as soon thereafter as it can be done without damaging the concrete, the surface of the walk shall be covered with not less than two inches of sand or other material which will afford equally good protection.  Such covering shall be kept wet for at least five days thereafter and closed to travel for at least twelve days.
When deemed necessary or advisable, freshly laid concrete shall be protected by a canvas covering.
   (l)   When not to be Mixed.  Concrete shall not be mixed or deposited when the temperature is below freezing, nor in any case upon a frozen foundation.
If, at any time during the progress of the work, the temperature is or may drop to forty degrees Fahrenheit, the water and other materials, as required, shall be heated and precaution taken to protect the work from freezing  for at least ten days.
   (m)   Contractor to Erect Barriers.  The contractor shall erect and maintain suitable barricades and barriers to protect the concrete sidewalk from traffic or travel, and before such sidewalk is open to travel the covering of sand or other material shall be removed by the contractor at his expense.
   (n)   Machine-Mixed Concrete.  If any cement for a sidewalk is mixed by machine, it shall be with the type of machine known as a "batch mixer", and no make of continuous mixer shall be allowed on any work.  The mixing shall continue until the cement is uniformly distributed and the concrete is uniform in color and homogeneous.
   (o)   Removal of Refuse.  Upon completion of the above work and the opening of the cement sidewalk to travel, all watercourses or gutters of streets shall be left free from any excavated material, forms or other refuse incident to the above work and in as good condition as before the work was done.
      (1967 Code 909.02)