Specifications for street roadway pavements with instructions to inspectors on street paving work (eBook)

HYDRAULIC CONCRETE FOUNDATION

28. Concrete.—Concrete shall be composed of Portland cement, sand, broken stone and water.

29. Portland Cement.[7]—Portland cement shall be defined as the pulverized product resulting from the calcination to incipient fusion of an intimate mixture of properly proportioned argillaceous and calcareous materials, and to which no addition greater than three per cent. has been made subsequent to calcination.

Specific Gravity.—The specific gravity of the dry cement at a temperature of two hundred and twelve (212) degrees F. shall not be less than 3.10.

Fineness.—It shall be pulverized to such fineness that not more than eight (8) per cent. shall fail to pass a number one hundred (100) sieve and not more than twenty-five (25) per cent. shall fail to pass a number two hundred (200) sieve.

Time of Setting.—At the temperature of sixty (60) degrees F. mortar made of neat cement shall not begin to set in less than thirty (30) minutes, nor set hard in less than one hour, but must set hard within ten (10) hours.

Strength.—When thoroughly mixed dry with clean, sharp, moderately coarse sand, in the ratio by weight of one part cement to three parts of sand, and then made into stiff mortar, briquets made from this mortar and exposed for one day to moist air and immersed in water for the balance of the periods named below, shall develop a tensile strength per square inch not less than the following:

Constancy of Volume.—When subjected to standard tests for constancy of volume, the cement shall show no tendency to swell or crack.

Composition.—The cement shall not contain more than one and three-fourths (1.75) per cent. of anhydrous sulphuric acid, nor more than four (4) per cent. of magnesia.

Tests.—Cement tests shall be conducted in accordance with the methods recommended by the “Committee on Uniform Tests of Cement” of the American Society of Civil Engineers.

Conditions.—All cement shall be supplied in original packages with the brand of the manufacturer marked on each package. It shall be protected during transportation from rain and moisture. It shall be delivered upon the work at least ten (10) days (exclusive of Sundays and holidays) before it is to be used, in order to allow of proper inspection, and the contractor shall furnish all necessary facilities for such inspection. Brands of cement without established good reputation, or not heretofore used in the City of... may be rejected; or they will be accepted only after they satisfactorily pass the 28–day test. Rejected cement must be at once removed from the street.

30. Sand.—Sand for concrete shall be composed of grains not softer than hard limestone. It shall be moderately coarse and preferably made up of grains of varying size producing a mass with low percentage of voids. It shall not contain, in all, more than seven (7) per cent. by volume of clay, loam, mica scales, silt, or other objectionable inorganic matter, nor more than one (1) per cent. of organic matter.

31. Broken Stone.—Broken stone for concrete shall be of hard and sound limestone or other stone equally hard and durable, broken to a roughly cubical form. It shall be screened through efficient revolving screens, and only such fragments as have passed through circular screen openings two and one-half (2½) inches in diameter, shall be used. If the crushed dust and fine fragments be not screened out, the stone must be so handled that the fine material will be evenly distributed through the mass when it reaches the concrete platform or mixer.[8]

32. Water.—Water used for concrete shall be fresh, and reasonably clean.

33. Care and Handling of Concrete Material.—Cement must not be allowed to become wet or damp. It shall be stored until used, whether in storehouses or on the street, so that no part of the packages shall be nearer than four (4) inches to the ground or pavement, and shall be effectually covered so that rain cannot reach it. Sand and stone, if stored on the street, shall be on lumber floors.[9] The stone shall be thoroughly wetted a sufficient time before being placed in the concrete to allow any surplus water to drain away, but shall remain moist where it reaches the concrete platform or mixer.

34. Ratio of Concrete Materials.—Concrete will be composed of one part Portland cement,... parts of sand and... parts of broken stone, and the proper quantity of water, all measured by volume.[10] The unit of measurement shall be the barrel of cement which shall be considered as containing four (4) cubic feet. The materials shall each be measured in such manner and with such accuracy that the quantities used will not vary more than seven (7) per cent. from the quantities required in the ratio named above for each batch of concrete.

35. Mixing Concrete.—If mixed by hand, concrete shall be mixed on platforms of iron or wood of sufficient size to admit of proper manipulation of the concrete. The sand shall be first spread evenly over the platform and the cement evenly distributed over the sand. These two materials shall then be mixed dry until a uniform and homogeneous mixture is secured. Sufficient water shall then be added and the mixing resumed and continued until a mortar of uniform consistency and texture is produced and distributed in an even layer over the platform. The stone shall then be distributed over the mortar and mixed therewith until the mortar is evenly distributed through the mass and every fragment of stone is well coated with mortar, sufficient additional water being added as the mixing progresses to produce a rather wet, but not sloppy, concrete.[11] Machine mixing of concrete will be preferred, provided the machine used secures equal accuracy in the ratios of materials and equally as good mixing as prescribed above for hand-mixing. Machine-mixed concrete must be delivered from the machine upon a wood or metal platform, or directly into barrows.

36. Placing the Concrete.—Concrete shall be placed on the sub-grade in such a manner as to prevent as far as possible the separation of the mortar from the stone. It shall be evenly distributed in a single horizontal layer of such depth that, after ramming, it will be not less than... inches thick. Immediately after being so placed it shall be well rammed until a compact mass is produced with its upper surface parallel to and... inches below the pavement datum. Depressions that may appear during the ramming may be filled with concrete of the same composition as used for the foundation, except that smaller-sized stone shall be used; mortar alone must not be used for this purpose, nor shall the upper surface of the concrete be plastered with mortar. The surface of the concrete shall not be broomed or troweled.[12]

37. Setting of Concrete.—After the concrete is completed it shall remain undisturbed until it be firmly set. The time allowed for setting shall not be less than five days, and as much longer as, in the judgment of the Engineer, may be necessary, depending upon the temperature of the weather and the setting qualities of the cement. During this period no hauling or traveling over the concrete must be permitted unless its surface be first protected by a covering of plank. The Contractor shall, if necessary, keep the concrete moist by wetting it, with hose, or otherwise, until twenty-four (24) hours before it is to be covered with the pavement surface.

38. Measurement of Concrete.—Concrete will be measured and computed in cubic yards as found completed on the street, the thickness being taken as... inches. The contract price for concrete foundation covers the cost of providing all the materials required, making, placing and ramming the concrete, and keeping it moist for the necessary period.

FOUNDATION OF OLD PAVING STONE

39. Foundations made of old stone paving blocks shall be constructed as follows:

Upon the sub-grade prepared as specified in Section 26, shall be spread a layer of good sand to an even depth of one and one-half (1½) inches. The paving blocks, whether taken up from the street to be paved, or brought from other streets or storage yards, shall be cleaned of all adhering earth, dirt and street refuse. The blocks shall then be set on the bed of sand, on edge, perpendicular to the grade, with their long dimension at right angles to the line of the street, in courses composed of stones of the same width, extending entirely across and at right angles to the axis of the street. Stones in adjoining courses shall break joint at least two inches. Joints between courses or stones, or along the curbstones, shall not exceed one inch in width. The stone shall be fitted closely around manholes or other structures in the street. The stones shall be so set in the bed of sand that after being rammed as hereafter specified, their tops shall be at the proper grade. After being thus set in place the stone shall be rammed with paving rammers having wooden faces and weighing not less than thirty (30) pounds, so as to force each stone to a good bearing in the sand below, and to bring its top to a uniform grade, parallel to and... inches below the pavement datum. No stone shall project more than one-fourth (¼) inch above the proper grade, and...