Stone. - The stone to be used for macadam shall be clean, sound, hard limestone or other stone deemed equally acceptable, broken or crushed, to the sizes specified.

All rolling shall be done as directed with a roller weighing not less than 250 pounds per inch of width of rollers.

Bituminous Binders. - The bituminous binder to be used shall be an asphaltic binder or a refined coal tar. The Contractor will be required to submit for testing a sample of the binder to be used. This sample shall contain one (1) pint and shall be labeled with the name of the street and the name of the manufacturer. It shall be submitted at least two weeks before any material is used and after approval all material furnished must be in strict accordance with the sample and the specifications below.

Asphaltic Binder. - The asphaltic binder shall have the following characteristics:

(1) It shall be free from water.

(2) The various hydrocarbons composing it shall be present in a homogeneous solution.

(3) It shall have a specific gravity at 77 degrees F. of not less than 0.97.

(4) The penetration shall be between 14 and 19 millimeters when tested for 5 seconds at 77 degrees F. with a No. 2 needle, weighted with 100 grains.

(5) Fifty grams of it, upon being maintained at a uniform temperature of 325 degrees F. for 5 hours in a cylindrical vessel, 5 1/2 centimeters in diameter by 3 1/2 centimeters high, shall not lose more than 5% in weight. The penetration (5 seconds. 77 degrees F., No. 2 needle, 100 grams weight) of this residue shall be at least 50% of the original penetration.

(6) Its solubility at air temperature in chemically pure carbon disulphide for the following named materials, or materials similar thereto, shall be at least 99.5% for pure bitumen products, 96% for Bermudez products, 81% for Cuban products and 66% for Trinidad products.

(7) It shall show an open flash point not less than 375 degrees F.

(8) It shall have a ductility at 77 degrees F. of not less than 40 centimeters (Dow mold).

Refined Coal Tar. - The coal tar shall be a residue of the distillation of coal tar only, and shall be refined for the special purpose of making pavement. No mixture of hard pitch with the lighter oils of coal tar will be permitted. The specific gravity of the coal tar shall not be less than 1.15 nor more than 1.26 at 60 degrees F. Its viscosity, determined by Engler Standard Viscosimeter, shall be not less than 100 nor more than 200 seconds for 100 c. c. at 212 degrees F. It shall contain not less than 20% nor more than 30% free carbon insoluble in benzol.

The melting point shall be between 100 and 110 degrees F.

The coal tar shall be free from water as determined by distillation, and shall show upon ignition not more than 1/2% of inorganic matter. No distillate shall be obtained lower than 338 degrees F.; and up to 600 degrees F., not less than 10% nor more than 25% of distillate shall be obtained. This distillate shall have a specific gravity of not less than 1.02 at 60 degrees F. The residue shall have a melting point of not more than 165 degrees F. In making the distillation an eight-ounce glass retort shall be used, and the thermometer suspended so that before applying the heat, the bulb of the thermometer is one-half inch above the surface of the liquid. The melting point shall be obtained by suspending a one-half inch cube in a beaker of water one inch above the bottom. The temperature shall be raised nine degrees per minute from 60 degrees F. The temperature at the instant the pitch touches the bottom shall be considered the melting point of the pitch.

Subgrade. - The subgrade, prepared under "Grading," Item 1, shall be parallel to the finished roadway and at a depth below same equal to the total thickness of the proposed pavement.

Thickness of Pavements. - Bituminous macadam shall be constructed of either nine (9) or twelve (12) inches thickness, depending on the character of soil, drainage, traffic, etc. The type to be used on each particular street will be noted on the drawing, and also specified under the heading of "Special Requirements." If the pavement is to be of the nine (9) inch thickness, it will be constructed of two courses: the first course six (6) inches, and the top course three (3) inches. If the pavement is to be of the twelve (12) inch thickness, it will be constructed in three courses: the first course five (5) inches, the second course four (4) inches, and the top course three (3) inches.

First Course, Nine (9) Inch Pavement. - Upon the prepared subgrade a layer of stone varying from 2 to 4 inches in maximum dimensions shall be evenly spread between the gutters. This course shall be thoroughly rolled until it does not appreciably creep or wave ahead of the rollers. Stone screenings or sand shall then be uniformly spread over the surface in small quantities by shovels from carts or piles alongside the road and the rolling continued, sweeping in the screenings meanwhile until no more will go in dry, when the surface shall be well sprinkled by an approved sprinkler, screenings being added where necessary and the rolling continued until the surface is satisfactorily finished. The surface shall be left with the clean stone projecting for a bond, leaving no loose material on the surface. When compacted the first course shall be at a uniform depth of three (3) inches below the proposed finished surface of the completed pavement.

First and Second Courses, Twelve (12) Inch Pavement. - The character of the stone for the first and second courses of the 12-inch pavement shall be exactly similar to that above specified, and the top of the second course shall be finished as specified for the top of the first course of the nine (9) inch pavement. The stone, however, shall be put on in two layers, one of five (5) inches after compaction and the other of four (4) inches after compaction, so that the top of the second course after rolling shall be at a uniform depth of three (3) inches below the proposed finished surface of the completed pavement.

Top Course. - Upon the surface, as previously specified, shall be evenly spread a layer of stone varying from 1 1/2 to 2 l/2 inches in maximum dimensions. This course shall be thoroughly rolled until the individual fragments have keyed together, the surface, while even and conforming to the required crown, shall be left open or porous in order to allow the penetration of the hot bituminous binder. When completed this course shall have a thickness of three inches.

Application of Binder. - The binder shall be heated in an approved heater equipped with a fixed or portable thermometer which will clearly and accurately indicate the temperature of the binder. The bituminous binder, if asphalt, shall bo heated to a temperature between 250 and 350 degrees F.; if tar, between 250 and 300 degrees F., and shall be uniformly distributed over the macadam by suitable appliances at a rate of between one and three-quarters (1%) and two (2) gallons to the square yard. Directly after application, clean chips from crushed bowlders, gravel or granite or equally satisfactory stone chips free from dust and consisting of fragments which will pass a five-eighth (5/8) inch ring, but be retained upon a one-quarter (1/4) inch screen shall be spread over the surface in sufficient quantities to fill the surface voids and prevent the binder from sticking to the wheels of the roller. Care shall be exercised not to apply more stone chips than will just fill the interstices, and any surplus material shall be swept from the surface, as directed. The road shall then be rolled until solid, more stone chips or screenings being applied as required in order to maintain satisfactory conditions.

A seal, flush or squeegee coat of the hot binder shall be uniformly distributed over the surface at a rate of at least one-half (1/2) gallon to the square yard. Clean, dry stone chips or screenings such as previously described or washed torpedo sand shall then be spread over this seal coat in just sufficient quantity to take up all excess of binder and form a smooth, well-bonded surface when rolled. The road shall be rolled until smooth and firm and to the proper line and grade.

The stone must be dry and free from dirt or dust at the time of applying the bituminous binder. The application of binder shall not be made when the atmospheric temperature is below 40 degrees F., unless specially permitted by the Engineer.

Surface Treatment. - Previous to the final acceptance of the street at the expiration of the guarantee period, the Contractor will be required to thoroughly clean the roadway and give the entire surface a flush coat of distilled tar or emulsified asphalt of such consistency as will allow its being applied cold. The. surface treatment will be followed by a light coat of torpedo sand evenly distributed.

The amount of tar to be applied will be such as to thoroughly cover the entire roadway, but without any excess. All material and method of work must be satisfactory to the Engineer.

The Contractor will be required to do the above work at such time as the weather is suitable for such work, and it is thoroughly understood that this work is an integral part of the contract, that the Contractor has allowed for the cost thereof in making his bid for bituminous macadam, and that he is not entitled to the retained ten (10%) per cent. until the work has been done to the satisfaction of the Engineer.

Crossings and Gutters for bituminous macadam streets shall be the same as specified for water-bound macadam.

Payment. - The price bid per square yard for this item shall include furnishing all materials and doing all the work necessary to complete the pavement as herein specified above the subgrade. In case no separate item appears for grading, the price bid shall also include the work provided for under "Grading," Item 1.

Crossing and gutters will be paid for as specified for water-bound macadam.

resurfacing with bituminous macadam - item 71

The work consists in resurfacing the existing macadam roadway with a three (3) inch wearing course corresponding to the top course as specified for Bituminous Macadam. The work will conform in all respects to the requirements for the above pavement, except that the existing roadway will supply the place of the first course of stone. Before commencing work on the wearing course the old roadway shall be thoroughly cleaned, all places shall be trimmed off which project above a grade three (3) inches below and parallel to the proposed finished roadway, and all holes and depressions below the bottom grade of the wearing course shall be filled with broken stone of sizes from one (1) to two and one-half (2l/2) inches. All such places shall be well rolled and covered with screenings as required for the first course of Bituminous Macadam.

Surface Treatment. - Streets resurfaced with Bituminous Macadam will be given a surface treatment exactly as previously specified before final acceptance at the end of the guarantee period.

Payment. - The broken stone and screenings below the grade of three (3) inches wearing course, will be paid for by the cubic yard wagon measure, as delivered on the work. The price bid per square yard for resurfacing with bituminous macadam will include all other work and material necessary to complete the pavement specified.