(A) It shall be thoroughly homogeneous and the various bituminous ingredients contained in it shall be in a state of complete solution. It shall not be oily to the touch.

(B) It shall have a penetration of from 40 to 75 at 77° F. The Engineer will fix the penetration to be used upon any particular street, basing his judgment upon the traffic conditions and upon the character of the mineral aggregate and the asphalt cement.

(C) When 50 grams are heated in a tin box, 2 1/4" in diameter and 1 1/2" in height for 5 hours, at a temperature of 350° F., it shall lose by volatilization, not more than 3 per cent. The residue, after heating, must have a penetration at least 50 per cent. of the penetration of the original sample.

(D) It shall not flash at less than 300° F. when tested in a New York State closed oil tester.

(E) Either the asphalt cement or its pure bitumen when made into a briquette (Dow mold) shall at 50 penetration (77° F.), have a ductility of not less than 20 centimeters at 77° F.; the two ends of the briquette should be pulled apart at the uniform rate of 5 centimeters per minute.

Note. - When the asphalt cement as used has a penetration greater than 50 at 77° F., an increased ductility of 2 cms. shall be required for every 5 points in penetration above 50 penetration.

Sand. - The sand used in the mineral aggregate shall be silicious, hard, moderately sharp, and free from clay, loam and mica, or other foreign matter. The sand shall not contain more than 5% of material which will pass a 200-mesh sieve, and it shall all pass an 8-mesh sieve. The grading and size of the sand shall be such that the sand, or sands, can be mixed so as to produce a mineral aggregate of the composition specified elsewhere herein. In the event that one sand will not give a grading suitable for the mineral aggregate, two or more sands shall be mixed in such proportions as are designated by the Engineer.

Filler. - The filler shall be a Portland cement or stone dust of sufficient density to weigh at least 90 pounds per cubic foot. At least 70% of the filler shall pass a 200-mesh sieve, and shall all pass a 50-mesh sieve. When five grams of the filler are thoroughly agitated with distilled water at 68°, by means of an air blast, not more than 40% shall subside on standing 15 seconds.

Crushed Stone. - The crushed stone used in the binder shall be a hard limestone, trap rock, or other approved rock, free from weathered or dirty particles and foreign matter. The stone shall crush with a cubical fracture. If the stone does not contain the proper amount of material passing the one-half-inch screen, the deficiency may be made up by the addition of gravel or sand. Ninety-five per cent. of the binder aggregate shall pass a screen having circular openings, whose diameter shall be three-quarters the thickness of the binder course to be laid. The remaining five per cent. shall not exceed in their largest dimensions the thickness of the binder course to be laid.

Binder. - The binder shall be composed of stone and sand, and asphalt cement of the character elsewhere herein specified and mixed in proper proportions. The stone, or stone and sand, and the asphalt cement shall be heated separately to such a temperature as will give, after mixing, a binder mixture of the proper temperature for the materials employed. The stone when used must be at a temperature between 225° and 350° F. The asphalt cement and stone shall be thoroughly mixed by machinery until a homogeneous mixture is produced, in which all the particles are thoroughly coated with asphalt cement.

Proportions. - The finished binder shall show upon analysis a bitumen content and mesh composition within the following limits:

Bitumen .............................................................................................................

4.5

to

7.0%

Passing

10-mesh

sieve

....................................................................................

15.0

to

30.0%

,,

4- "

,,

..........................................

20.0

to

35.0%

,,

2- "

,,

....................................................

35.0

to

50.0%

,,

3/4-inch

mesh

................................................

5.0

to

15.0%

Laying. - The binder mixture prepared in the manner above described shall be brought to the work in dump wagons covered with canvas or other suitable material, and upon reaching the street shall have a temperature between 200o F. and 325° F. The temperature of the binder mixture within these limits shall be regulated according to the temperature of the atmosphere and the working of the binder. On reaching the street it shall at once be dumped on the concrete and then be deposited roughly in place by means of hot shovels, after which it shall be uniformly spread by means of hot rakes, and then at once be thoroughly compacted with an 8-ton roller. The thickness of the finished binder shall average 1 1/2 inches and not more than a 30% variation from the average thickness specified will be permitted at any spot. The upper surface of the finished binder shall be parallel to the established grade for the finished pavement. The surface after compression shall show at no place an excess of asphalt cement, and any spot showing such excess shall be cut out and replaced with other material. All binder that shows lack of bond or that is in any way defective, or which may become broken up before it is covered with wearing surface, must be taken up and removed from the street and replaced by good material, properly made and laid in accordance with these specifications, at the expense of the Contractor. No more binder shall be laid at any one time than can be covered by one day's run of the paving plant on surface mixture. The binder,, when laid, shall be followed and covered with wearing surface as soon as it is practicable in order to effect the most thorough bond between the binder and the wearing course. The binder course shall be kept as clean and as free from traffic as possible under working conditions. If necessary, it must be swept off immediately before laying the wearing surface on it.

No binder shall be laid when in the opinion of the Engineer the weather conditions are unsuitable or unless the concrete on which it is to be laid is dry and has set a sufficient length of time. The concrete base shall be swept thoroughly immediately before binder is laid.