Subgrade. - The subgrade for Bitulithic Pavement will be --------- (---------) inches below and parallel to the finished grade of the roadway. On the sub-grade, prepared as specified under Grading Item 1, will be deposited ---------

(---------) inches of concrete as specified, the upper surface of which shall be compact and true, parallel to and two (2) inches below the finished roadway grade. If deemed necessary, the surface of the concrete shall be roughened by tamping with toothed rammers or by other satisfactory means.

Paving Mixture. - Before starting work, the contractor shall, at the request of the Engineer, submit a formula for the paving mixture to be used. This formula shall be subject to approval or rejection by the Engineer, and in the latter case a new formula shall be submitted. If the contractor is unable or unwilling to submit a formula such as the Engineer will approve, the latter shall prescribe the formula to be used for the proposed work. In any case, no change from the approved mixture can be made without written permission by the

Engineer.

Wearing Surface. - Either of the two following methods and apparatus shall be used in the preparation of the wearing surface:

1. The stone and sand shall be heated in a rotary drier and while still hot, separated into the desired number of different sizes by means of a rotary screen having a minimum screen opening of about 1/10 of an inch and a maximum opening of about one and one-half (1 1/2) inch. The openings in the successive screen sections up to one-half (1/2) inch size shall not vary more than one-quarter (1/4) of an inch and not more than three-quarters (3/4) of an inch for the sizes larger than one-half (1/2) inch. The aggregate thus separated shall pass into a bin having sections or compartments corresponding to the screen sections. From these compartments the aggregate shall pass into a weigh box, resting on a multi-beam scale. The desired amount of aggregate from each of the above compartments shall be accurately weighed separately on the scale and the batch dropped into a "twin-pug" mixer, where it shall be intimately associated and thoroughly commingled with a pre-determined quantity of Bitulithic Cement sufficient to coat all particles of the aggregate and to fill the voids in same.

2. The stone and sand shall first be carefully measured as to sizes and quantity of each size and then shall be fed into an elevator terminating in a hopper or bin which discharges into a rotary dryer or heater, both hopper and heater being so designed as to keep each batch by itself until heated. From the rotary heater the batch of mineral aggregate shall pass into a rotary cylindrical mixer containing blades, spirals or other devices for producing a uniform mixture of the mineral aggregate with a pre-determined quantity of the Bitulithic Cement, sufficient to coat all the particles of the aggregate and to fill the voids in same.

The different grades of stone and sand ranging in size from impalpable powder to about one-half the thickness of the wearing surface shall be combined in such proportions as to secure in the mineral aggregate inherent stability, that is density, or low percentage of voids, and stability or resistance to displacement, producing an aggregate which when combined with the Bitulithic Cement and laid in place and compacted will form a street paving structure consisting of mineral aggregate of different sizes and the Bitulithic Cement which permeates the entire mass, fills the voids and unites the various particles thereof. If the crushed stone and sand do not contain enough finely divided particles or impalpable powder to produce a low percentage of voids in the aggregate the deficiency shall be made up by the addition of any other suitable fine mineral matter.

The mixture and ingredients thereof, shall be maintained at a temperature consistent with good workmanship. The mixture when reaching the street shall be hot enough to allow of being easily spread and raked, and shall not be so hot as to injure the Bitulithic Cement.

Surface Finish. - Either of the following methods may be used for applying the seal coat:

(a) Immediately after the wearing surface mixture has been spread, but before compression, there shall be spread over it the seal coat mixture of approximately twenty-five (25) pounds per square yard of aggregate (all of which shall pass one-quarter [1/4] inch screen), mechanically combined with approximately twelve (12) to fourteen (14) per cent. by weight, of bitulithic cement. The seal coat and wearing surface mixtures shall then be immediately compressed by thorough rolling.

(b) Immediately after spreading the wearing surface mixture, it shall be thoroughly rolled and while it is still warm, there shall be evenly spread over it by means of a bitumen spreading machine, approximately one-quarter (1/4) gallon per square yard of hot Bitulithic Cement to flush the surface voids without leaving an excess. Immediately thereafter the surface shall be covered with approximately twenty-five (25) pounds of dry, clean, sharp sand, or stone chips not over one-quarter (1/4) inch in diameter, which shall be immediately rolled into the surface.

(c) On grades in excess of three (3) per cent. a coarser aggregate may be used with either method of applying the seal coat.

General. - Each layer of the work shall be kept as free as possible from dirt, so that it will unite with the succeeding layer.

The bituminous composition or cement shall in each case be free from water, and shall be especially refined to remove volatile and other matter susceptible to atmospheric influences.

Warren Bros. Company, owner of the patents used in the construction of the bitulithic pavement, shall file with the Director of Public Service a properly executed binding agreement to furnish to any contractor desiring to bid for the work all the necessary bitulithic surface material, mixed ready for use, and Bitulithic Cement and the sand, gravel, or stone screenings for the surface finish course, in accordance with the Sections "Wearing Surface" and "Surface Finish," at a definite reasonable price per square yard. Said price shall include a license to use all of the patents required in the construction of the bitulithic pavement as herein specified.

The acceptance of bids by the City of --------- and the letting of a contract for the same shall be deemed by Warren Bros. Company to be an acceptance of its proposal by the City of --------- and by the Contractor to whom such contract shall be awarded, and are all that shall be necessary to bind Warren Bros. Company to said agreement. The filing of a bid under these specifications will be construed as an acceptance of the terms of the licensed agreement filed by the Warren Bros. Company, at the price fixed in said agreement which is on file with the Director of Public Service.

Payment. - The price bid per square yard will include all labor and material necessary to complete the pavement above the concrete foundation; it will also include all work as specified under "Grading," Item 1, where no special bid is asked for the grading item.