Letter suffixes will be added to pay item numbers 404(1), 404(2), and 404 (3) to designate alternative types of materials to be bid on. Section 405.-ROAD MIX BITUMINOUS PAVEMENT Description 405.01 This work shall consist of constructing one or more courses of road mix bituminous pavement on a prepared base or road surface in accordance with these specifications and in reasonably close conformity with the lines, grades, thicknesses and typical cross sections shown on the plans or established by the Engineer. Materials 405.02 Bituminous Material. The bituminous material shall be of the type and grade called for in the bid schedule and shall conform to the following subsections: Slow curing liquid asphalt (SC) Medium curing liquid asphalt (MC) Tar Emulsified asphalt 702.03 702.03 702.03 702.02 702.04 Application temperatures of bituminous materials shall conform to subsection 702.05. Bituminous material may be conditionally accepted at the source, subject to the provisions of clause 10 of the General Provisions. 405.03 Aggregate. The aggregate will be tested for ac ceptance immediately preceding addition of bituminous material to the mix. This acceptance will be based on periodic samples of the windrow after all aggregates have been blended for each layer. (a) Case 1 (new aggregate).—New aggregate shall conform to subsection 703.09, for grading F of table 703-4. (b) Case 2 (aggregate salvaged from the existing surface). Where aggregate required for the road mix surface course is already in place, the Contractor shall not be responsible for its grading or quality except for removal of oversize pieces. In general, salvaged aggregate to be used for road mix surface course will consist of material meeting the requirements given above for new aggregate or may consist of selected granular material of other gradings. Any particles of salvaged aggregate appearing in the surface at the time of lay-down and finishing that will not pass a 11⁄2-inch sieve shall be removed by the Contractor as directed by the Engineer. Construction Requirements 405.04 Weather Limitations. The construction of road mix bituminous pavement shall be carried on only when the surface on which the material is to be placed is dry and when the atmospheric temperature is above 50° F. and has not been below 40° F. during the preceding 24 hours. 405.05 Equipment. The equipment used by the Contractor shall include scarifying, mixing, spreading, finishing and compacting equipment; a bituminous distributor; and equipment for heating bituminous material. The distributor shall be so designed, equipped, maintained and operated that bituminous material at even heat may be applied uniformly on variable widths of surface up to 15 feet at readily determined and controlled rates from 0.05 to 2.0 gallons per square yard, with uniform pressure, and with an allowable variation from any specified rate not to exceed 0.02 gallons per square yard. Distributor equipment shall include a tachometer, pressure gauges, accurate volume measuring devices or a calibrated tank, and a thermometer for measuring temperatures of tank contents. Distributors shall be equipped with a power unit for the pump, and full circulation spray bars adjustable laterally and vertically. Traveling or stationary mixing plants or other equipment of proven performance may be used by the Contractor in lieu of the specified equipment if approved. Rollers shall be self-propelled steel-wheel tandem or 3wheel rollers weighing not less than 8 tons each, and pneumatic-tire rollers having a total compacting width of not less than 60 inches and the gross weight adjustable within the range of 200 to 350 pounds per inch of compaction width. The operating weight shall be as directed. Tire pressure or contact pressure may be specified for pneumatictire rollers. 405.06 Preparation of Base. (a) Case 1 (new aggregate).—When new aggregate is to be used for the road mix surface course, the existing base shall be scarified lightly and bladed to uniform grade and to the cross section shown on the plans and shall then be rolled, or watered and rolled, as directed. If so ordered by the Engineer, depressions shall first be filled and weak portions of the base strengthened with new aggregate. (b) Case 2 (salvaged aggregate).—When material in the existing road surface is to be used for mixing, the surface shall first be scarified lightly and bladed to uniform grade and to the cross section shown on the plans. The reshaped surface shall then be scarified again to the depth ordered by the Engineer and in such manner as to leave a foundation of undisturbed material parallel, both in profile and cross section, to the proposed finished surface. The loosened material shall be bladed aside into a windrow at the side of the road, and the undisturbed material rolled, or watered and rolled, as directed. 405.07 Placing Aggregates. New aggregates, where required, shall be uniformly spread on the prepared surface by the use of spreader boxes, or other approved mechanical spreading devices. When two or more sizes of aggregates are used, each size of aggregate shall be placed in the proper amount to provide for surfacing of the required width and thickness. The proper amounts of the separate sizes of aggregate for each course shall be blended and shaped into a windrow of uniform cross section. At least one day shall then be allowed for measuring, sampling, and testing for approval of quantity and gradation before the windrow is spread for application of bituminous material. If the surface moisture of the aggregate is more than 2 per cent of the dry weight of the aggregate, except when the bituminous material is emulsified asphalt, the aggregate shall be turned by blades or disc harrows or otherwise aerated until the moisture content is reduced to 2 per cent or less. The aggregate shall then be spread smoothly and uniformly over half the road or other convenient width of the surface ready for the application of bituminous material, except that when a traveling mixing plant is used the aggregate shall be formed into a uniform cross section. In lieu of aerating and drying the aggregate, the Contractor may use an approved additive, which shall be sat isfactorily blended with the bituminous material. The additive shall permit suitable coating of the wet aggregate and shall prevent the bituminous coating from stripping in the presence of water. 405.08 Application of Bituminous Material. The bituminous material shall be uniformly distributed in successive applications, in such amounts and at such intervals as directed. The mixing equipment shall follow immediately behind the distributor, after each application of bituminous material, to partially mix the aggregate and the bituminous material. 405.09 Mixing. After the last application of bituminous material and partial mixing, the entire mass of bituminous material and aggregate shall be windrowed on the road surface and then mixed, by blading the mixture from side to side of the road, or by manipulations producing equivalent results, until all aggregate particles are coated with bituminous material and the whole mass has a uniform color and the mixture is free from fat or lean spots, balls or uncoated particles. During the mixing operations, care shall be taken to avoid cutting into the underlying course or contaminating the mixture with earth or other extraneous matter. When directed, the mixing process shall be confined to part of the width or area of the road so as to allow traffic to pass. Should the mixture show an excess, deficiency or uneven distribution of bituminous material, the condition shall be corrected by the addition of aggregate or bituminous material as required and re-mixing. If the mixture contains excessive amounts of moisture or volatile matter, it shall be bladed, aerated or otherwise manipulated until the moisture and volatile content are satisfactory. The spreading of the mix shall not be done when the surface to be covered is in an unsatisfactory condition. At the end of each day's work, or when the work is interrupted by weather conditions or otherwise, all loose material shall be bladed into a windrow, whether mixing is completed or not, and shall be retained in a windrow until operations are resumed. When the mixing operations have been satisfactorily completed, the mixture shall be formed into a windrow of uniform cross section. If the Contractor elects to use traveling or stationary mixing plants in lieu of the specified equipment, the same requirements regarding residual moisture and evaporation of volatiles given above shall apply. 405.10 Spreading, Compacting, and Finishing. The material shall be spread by a self-propelled, pneumatic-tire blade grader or a mechanical spreader of approved type. In spread ing from the windrow, care shall be taken to avoid cutting into the underlying base. After the material is spread, the surface shall be rolled. Rolling shall be parallel to the road center line and shall commence at the outer edges of the road, overlapping the shoulders and progress toward the center, overlapping on successive passes by at least one-half the width of the roller, except that on superelevated curves rolling shall progress from the lower to the upper edge. Each pass shall terminate at least 3 feet in advance or to the rear of the end of the preceding pass. During the compaction the surface shall be dragged or bladed as necessary to fill ruts and to remove incipient corrugations or other irregularities. Rolling shall continue until the surfacing is of uniform texture and satisfactory compaction is obtained. Initial rolling shall be performed with a pneumatic-tire roller and final rolling with a 3-wheel or tandem-type steel wheel roller. Rolling shall be discontinued whenever it begins to produce excessive pulverizing of the aggregate or displacement of the mixture. Where the compacted thickness of the road mix surface is to be more than 2 inches, the mixture shall be spread from the windrow and compacted in 2 layers, the first layer to be bladed and rolled before the second layer is spread. While the surface is being compacted and finished the Contractor shall trim the edges neatly to line. 405.11 Surface Requirements. The surface will be tested by the Engineer using a 10-foot straightedge at selected locations. The variation of the surface from the testing edge of the straightedge between any 2 contacts with the surface shall at no point exceed 3/16-inch. All humps or depressions exceeding the specified tolerance shall be corrected by removing defective work and replacing it with new material as specified. Method of Measurement 405.12 Aggregate and bituminous material furnished for road mix bituminous pavement will be measured by units shown in the bid schedule. The quantity of road mix acceptably completed will be measured by the mile or square yard, as shown in the bid schedule. When slag and stone (or gravel) are designated as alternative materials for pay items in the bid schedule and payment is by weight, the estimated quantities will be based on assumed average bulk specific gravities of available alternative materials. No adjustment in contract unit price will be made for variation in quantity due to difference in the specific gravity of the material actually used. |