CHAPTER  1900.  Asphalt Surfaces and Base Courses.

 

 1901. General. This section covers the requirements for bituminous surface paving on roads.  As a minimum, all streets shall be surfaced in accordance with the following:

 

             (1)       Six inch sub grade compaction

             (2)       Eight inch pit run

             (3)       Four inch crushed base

             (4)       Two and one‑half inch asphalt

 

 1902. Base Course. Base for all streets shall consist of select material, either natural or crushed, and shall be graded as follows:

 

Sieve Size

Ideal Gradation

Ideal Gradation Tolerance

1 inch

100

0 % by weight

1/2 inch

85

+/‑ 6 % by weight

No. 4 Sieve

55

+/‑ 6 % by weight

No. 16 Sieve

31

+/‑ 4 % by weight

No. 200 Sieve

9

+/‑ 2 % by weight

 

            The material shall be deposited and spread in a uniform layer, without serration of size, with such depth that when compacted the layer will have the required thickness.

 

            Each layer shall be compacted for the full width and depth by rolling with a pneumatic roller weighing at least ten tons. Alternate blading and rolling will be required to provide a smooth even and uniformly compacted course true to cross section and grade.  Places inaccessible to rolling shall be compacted with mechanically operated hand tampers.  No layer shall exceed six(6) inches in compacted thickness.

 

            The gravel base shall be compacted to not less than ninety‑five (95%) maximum dry density as determined by AASHTO T‑180. Surfaces shall be true to established grade with thickness being not less than one‑half inch from the required layer thickness and with the surface elevation varying not more than one‑half inch in ten feet from the true profile and cross section.

 

            The base material shall be placed at or near optimum moisture content and the moisture content shall be maintained until paving is completed.

 

            Minimum on local roads as per truck traffic or heavier than local traffic.  Get CBR and design pavement section to be submitted and approved by City Council.

 

 1903. Bituminous Surface Course. The contractor shall place and compact a bituminous surface course over the dry dust‑free compacted base course.  The surface course shall consist of a mixture of mineral aggregate and binder.  Gradation of aggregate shall conform to the following:

 

Sieve Size

Ideal Gradation (Percent Passing)

Ideal Gradation Tolerance

1/2 inch

100

0 % by weight

No. 4

70

+/‑ 15 % by weight

No. 16

31

+/‑ 7 % by weight

No. 50

15

+/‑ 6 % by weight

No. 200

6

+/‑ 2 % by weight

 

            The contractor shall establish a job mix formula and the amount of bituminous material shall be subject to the approval of the Engineer and shall meet the requirements of the gradation selected.

 

            The bituminous material for the surface course shall be 70 penetration asphalt cement conforming to the requirements of AASHTO.  Designation M 226, Table 2, Viscosity Grade AC10.

 

            The bituminous surface course shall be mixed at a mixing plant and spread and compacted on the prepared base in conformance with the lines and dimensions shown on the plans and in accordance with these specifications.

 

 1904. Job Mix Formula and Testing.  The Contractor shall provide a job mix formula and testing as outlined in this section whenever the total development will require more than 500 tons of asphalt mix.  The formula shall be submitted to the city at least 15 days prior to the start of paving.  The formula shall indicate the definite percentage of each sieve fraction of aggregate and the percentage of bituminous mixture shall be designed using procedures outlined in ASTM D 1559 using a Marshall apparatus.  The mix shall conform to the following requirements:

 

            (a)        Marshall Stability                      1200 pound minimum

            (b)        Flow (0.01 in.)                                     10‑18

            (c)        Voids Content                         2% to 4%

            (d)        Number of Brows                     50

 

            Testing for gradation, bitumen content, and compaction shall be accomplished by an independent test laboratory.  Five samples shall be taken when the total asphalt mix quantity for the full development is between 500 and 1500 tons, eight samples for 1500 to 2500 tons, and as directed by City Engineer for more than 2500 tons.  Mat thickness shall be determined by core samples and construction inspection.  Compaction and moisture content shall be determined by AASHTO Designation T238‑76I (ASTM Designation D 2922 71)

 

            Penalties for deviation shall be assessed according to the schedules outlined in the State of Utah Standard Specifications for Road and Bridge Construction ‑ 1979.

 

            The penalty will be assessed to the developer and the amount retained will be paid to the city for future maintenance on the road.

 

 1905. Construction Methods and Equipment. The methods employed in performing the work, all equipment, tools and machinery and other appliances used in handling the materials and executing the work shall be the responsibility of the contractor. The contractor shall make such changes in the methods employed and in the equipment used as are necessary whenever the bituminous material produced does not meet the specifications herein established.

 

 1906. Spreading and Compacting. The bituminous mixtures shall spread with self‑propelled mechanical spreading and conditioning equipment capable of distributing at least a 12 foot width. The mixture shall be spread and struck off in such a manner that the finished surface shall result in a uniform smooth surface. The longitudinal joints in succeeding courses shall be offset at least six inches transversely to avoid a vertical joint through more than one course.

 

            The thickness of asphalt adjacent to a gutter shall be at least 1/2 inch thicker than that specified for the remainder of the street.

 

            The temperature of the bituminous mix shall be between 275 degrees Fahrenheit and 325 degrees Fahrenheit when placing. It is desirable to complete compaction of the material before the temperature or the mix drops below 180 degrees Fahrenheit.

 

            After the mixture has been spread, the surface shall be rolled in longitudinal direction commencing at the outside edge or lower side and proceeding to the higher side.  Each pass of the roller shall overlap the preceding pass at least one‑half the width of the roller.  Rolling shall continue until ninety‑five percent (95%) of the laboratory density, as determined in accordance with ASTM Designation D1559 for the bituminous mixture being used, has been obtained.

 

            Rolling operations shall be conducted in such a manner that shoving or distortion will not develop beneath the roller.

 

            The surface of the pavement, after compaction, shall be uniform and true to the established crown and grade.  When tested with a ten foot straight edge placed parallel to the center line of the pavement, the surface of the pavement at any point shall not deviate from the lower edge of the straight edge by more than one‑eighth of an inch.  All high and low spots shall be remedied immediately by removing the wearing course material over the affected areas and replacing it with fresh, hot wearing course and surface finish material and immediately compacting it to conform with surrounding area.

 

 1907.  All traffic shall be kept off the surface until rolling is completed and asphalt temperature lowers to 100 degrees Fahrenheit or less.

 

            Traffic shall be reinstated only after inspection and approval by the City Engineer.

 

 1908. Weather Limitations. No bituminous surface shall be placed when the temperature of the air or road bed is 50 degrees Fahrenheit or below, during rainy weather, when the base is wet or during other unfavorable weather conditions as determined by the Engineer.  The air temperature shall be measured in the shade.