ITEM P-217 AGGREGATE-TURF PAVEMENT

DESCRIPTION

217-1.1 This item shall consist of an aggregate-turf pavement composed of a base course of soil-bound crushed stone, soil-bound gravel, or soil-bound sand, or fine aggregate, and a seed bed of suitable soil or combination of soil and aggregate, constructed on a prepared subgrade or a previously constructed underlying course in accordance with these specifications and in conformity with the dimensions and typical cross section shown on the plans and with the lines and grades established by the engineer.

This item may include the furnishing and applying of fertilizer, lime, top soil, or other plant nutrients; the furnishing and planting of seed; and the furnishing and spreading of mulch. When any of these turfing materials are required the quality, quantity, and construction methods shall be in accordance with applicable CAA Turf Specifications. When turf is to be established, the seed bed soil or topsoil shall be a natural friable loam, possessing characteristics of the best locally obtainable soils which can produce at least a fairly heavy growth of crops, grass, or other vegetation.

The prepared composite mixture of aggregates used for the base course shall be type A, type B, or stabilizer aggregate mixed with in-place materials, whichever is called for in the bid schedule, provided that when the type is not so fixed the type or types shall be selected by the engineer.

217-2.1

MATERIALS

STABILIZED MIXES. The type or types of base course stabilized mixtures designated shall conform to the following requirements:

Type A―The materials for this type shall be composed of natural or artificial mixtures of clay or soil binder and gravel, stone or sand, or other aggregate, as screenings proportioned to meet the requirements hereinafter specified. The aggregate retained on a No. 4 mesh sieve shall be composed of hard, durable, particles and shall be free from injurious or deleterious substances.

Type B-The material for this type shall consist of natural or artificial mixtures of gravel, stone, or slag and soil mortar so proportioned as to meet all the requirements hereinafter specified. The coarse aggregate shall consist of clean, hard, durable particles of crushed or uncrushed gravel, stone, or slag, free from soft, thin, elongated or laminated pieces, and vegetable or other deleterious substances. It

shall be hard and durable enough to resist weathering, traffic abrasion, and crushing. Shales and similar materials that break up and weather rapidly when alternately frozen and thawed, or wetted and dried, shall not be used. The soil mortar shall be that portion passing the No. 10 mesh sieve, and shall be composed of soil binder and granular material such as stone or slag screenings or sand.

The prepared composite mixture used shall meet the applicable gradation requirements as follows:

TABLE 1.-Requirements for Gradation of Mixture

In all cases the fraction passing the No. 200 mesh sieve shall be less than two-thirds of the fraction passing the No. 40 mesh sieve. The fraction passing the No. 40 mesh sieve shall have a liquid limit not greater than 30 and a plasticity index not greater than 8. The fine aggregate and any fine soil particles used as a binding material shall be such that they will produce the required plastic properties and characteristics necessary for a stable soil-aggregate course after mixing and compacting.

217-2.2 STABILIZER AGGREGATE. When called for in the bid proposal, stabilizer aggregate meeting the gradations as required herewith shall be placed upon the existing soil or base course in the quantity per square yard as specified. The aggregate shall be uniformly blended with the soil or base course material to the depth required or as shown on the plans. The aggregate shall consist of crushed stone, crushed or uncrushed gravel, or crushed slag, and shall have a percent of wear of not more than 60 at 500 revolutions as determined by A. A. S. H. O. Method T-96 (Los Angeles Rattler Test). The aggregate shall be free from soft, thin, elongated, or laminated pieces, disintegrated material, or other deleterious sub

stances.

When approved or included in the proposal, screenings or coarse sand may be used for stabilizer aggregate. The gradation shall be as shown in the table.

Where sands as existing subgrade or base require stabilization, this may be secured by the addition of clays or limerock. The operations

of spreading and mixing shall be handled as given under construction methods.

The stabilizer aggregate shall meet the gradation requirements as follows:

TABLE 2.-Requirements for Gradation of Stabilizer

Aggregate

If the aggregate becomes segregated prior to placing, it shall be remixed until gradation is as required.

217-2.3 MOISTURE CONTENT. The materials of Type A, B, or the mixture of stabilizer aggregate or binder with in-place materials shall have sufficient moisture at the time of rolling to insure the required compaction.

217-3.1

CONSTRUCTION METHODS

OPERATION IN PITS. All work involved in clearing and stripping pits including handling unsuitable material encountered shall be performed by the contractor at his own expense. The base or binder material shall be obtained from pits or sources that have been approved. The material in the pits shall be excavated and handled in a manner that a uniform and satisfactory product shall be secured.

217-3.2 EQUIPMENT. All equipment necessary for the proper construction of this work shall be on the project, in first-class working condition, and shall have been approved by the engineer before construction is permitted to start.

The powered roller shall be of the three-wheeled type, weighing not less than five (5) tons nor more than eight (8) tons. The roller shall have a rear-wheel compression of not less than 250 pounds per linear inch of tire width and shall be equipped with adjustable scrapers. The tamping roller shall consist of metal rollers, drums, or shells surmounted by metal studs with tamping feet projecting not less than six (6) inches from the surface of the roller, drum, or shell. The area of each tamping foot shall be from five (5) to nine

(9) square inches. Each roller shall consist of two sections and the length of each section shall be not less than four (4) feet. When empty, the roller shall produce at least 120 pounds per square inch of area of tamping feet in contact with the ground. The pneumatic roller shall consist of pneumatic tires arranged in a manner so as to provide a satisfactory compacting unit. The roller shall have an effective rolling width of at least sixty (60) inches, and shall give a compression of at least 275 pounds per inch of width of tread when fully loaded. The tires shall be uniformly inflated. The roller and operating power unit shall meet the approval of the engineer.

Other equipment may be used for compacting and consolidating the base course, upon approval of the engineer. Such equipment shall be routed over the area being compacted, and shall be operated until the required density is obtained.

Equipment for spreading and shaping shall consist of spreader boxes having strike-off templets, or screeds, or of other spreading devices which will place the required quantity of base material, stabilizer aggregate, or binder in a uniform layer with a minimum of segregation.

Provision shall be made by the contractor for furnishing water at the site of the work by equipment of ample capacity and of such design as to assure uniform application.

The processing equipment shall be designed, constructed, operated, and of such capacity so as to thoroughly mix all materials and water in the proportions as directed to produce a base course of the gradation and consistency required.

217-3.3 PREPARING SUBGRADE. Before any base course material is placed, the subgrade or underlying course shall be prepared and conditioned as specified for that course. The underlying course shall be checked and accepted by the engineer before placing and spreading operations are started.

Grade control between the edges of the runways shall be by means of grade stakes, steel pins, or forms placed in lanes parallel to the centerline of the runway and at intervals sufficiently close that string lines or check boards may be placed between the stakes, pins, or forms.

To protect the underlying course and to insure proper drainage, the spreading of the base shall begin along the centerline of the runway or taxiway on a crowned section or on the high side of the pavement with a one-way slope.

217-3.4 PLACING MATERIALS. (a) When all new material is called for, it shall be placed on the prepared course and compacted in layers of the thickness shown on the plans. The depositing and spreading of the material on the prepared and completed layer shall commence where designated and shall progress continuously without breaks. The material shall be deposited and spread in lanes in a uniform layer and without segregation of size to such loose depth that, when compacted, the layer will have the re

quired thickness. It shall be the charge of the contractor that the required amount of approved material is delivered in each 100-foot station. The material shall be spread with approved equipment. When combining materials from different sources is necessary, such combining may be done either at the pits in a processing plant prior to delivery of the material, or on the course by the proper proportions of each material being deposited in successive spreadings as will give the required gradation and thickness of layer. If the combining is done on the course, the mixing shall be as specified hereinafter.

(b) When blending of new material with material on the existing surface is called for, the existing surface shall first be scarified lightly and bladed to uniform grade and to cross section shown on the plans. After blading and when necessary, the existing surface shall be further scarified and/or pulverized to provide sufficient loose material of the required depth to be mixed with the added material. Over the prepared material in-place shall be spread the new material of the gradation called for and in the amounts as directed by the engineer.

217-3.5 SPREADING AND MIXING. (a) Materials that have been mixed and processed in a processing plant at the pits, or elsewhere, shall be delivered and spread by specified equipment to the required depth.

(b) Following the placing of the required quantities of materials being combined on the base course, the total base material shall be thoroughly pulverized and mixed by means of approved rotary-pulverizing mixers. The moisture content of the aggregate and soil binder shall be as directed by the engineer, and shall be that necessary to secure thorough mixing and the required compaction. The mixing shall produce a homogeneous mass of the specified gradation and soil characteristics to form a base course of the desired qualities. When the mixing is completed the material shall be spread in a uniform layer which, when compacted, will meet the requirements for thickness and typical cross section.

217-3.6 ROLLING. Immediately following final spreading, the material shall be compacted to full width by rolling with approved compacting equipment. Rolling shall progress gradually from the sides to the center of the lane under construction, or from one side toward previously placed material, and shall continue until all the surface has been rolled and compacted. Rolling shall continue until the base material has been compacted from seventy (70) to ninety (90) percent density as determined by the standard Proctor Density Test, A. A. S. H. O. Method T-99, and as designated in the proposal. Any irregularities or depressions that develop under rolling shall be corrected by loosening the material at these places and adding or removing materials until the surface is smooth and uniform. The base material shall be at a satisfactory moisture content at the time of rolling to secure the required compaction.