if necessary. The mixing shall continue until the mixture is uniform throughout. Areas of segregated material shall be corrected by the addition of binder or filler material and by thorough remixing. Water in the amount and as directed by the engineer shall be uniformly applied prior to and during the mixing operations if necessary, to maintain the material at the proper moisture content. When the mixing and blending has been completed, the material shall be spread in a uniform layer which, when compacted, will meet the requirements of thickness and typical cross section.

213-3.8 GENERAL METHODS FOR PLACING. The base course shall be constructed in a layer of not less than four (4) inches nor more than six (6) inches of compacted thickness. Each layer shall be tested for depth. The material as spread shall be of uniform gradation, with no pockets of fine or coarse materials. The base, unless otherwise permitted by the engineer, shall not be spread more than 2,000 square yards in advance of the rolling. Any necessary sprinkling shall be kept within this limit. No material shall be placed in snow or on a soft, muddy, or frozen course.

When more than one layer is required, the construction procedure described herein shall apply similarly to each layer.

The engineer will make tests to determine the maximum density and the proper moisture content of the base material, and this information will be available to the contractor. The base material shall be brought to a satisfactory moisture content before rolling is started, either by sprinkling and mixing or by aeration.

During the placing and spreading, sufficient caution shall be exercised to prevent the incorporation of subgrade, subbase, or shoulder material in the base course mixture.

213-3.9 FINISHING AND COMPACTING.

After spreading

or mixing, the base material shall be thoroughly compacted by rolling and sprinkling when necessary. The initial rolling of the course shall be done with tamping rollers. A single roller shall perform the rolling for not more than twenty-five (25) cubic yards per hour, and additional rollers shall be provided when the spreading is greater than this

rate.

Rolling shall progress gradually from the sides to the center of the lane under construction or from one side toward previously placed material, by lapping uniformly each preceding track by at least twelve (12) inches. The rolling shall continue until the base material is thoroughly set and bonded and there is no creeping ahead of the roller. Rolling shall continue until the base material has been compacted to not less than ninety-five (95) percent density, as determined by the CAA compaction-control tests T-611 for the class of airport involved. Blading and rolling shall be done alternately as required or directed to obtain a smooth, even, and uniformly compacted base. For final rolling the ten-ton three-wheel roller shall be used.

The course shall not be rolled when the underlying course is soft or yielding or when the rolling causes a wavelike motion in the base course. When the rolling develops irregularities that exceed three

eighths (%) of an inch when tested with a sixteen (16) foot straightedge, the irregular surface shall be loosened and then refilled with the same kind of material as that used in constructing the course, and again rolled as required above.

Along places inaccessible to rollers, the base course material shall be tamped thoroughly with mechanical or hand tampers. Each hand tamper shall weigh not less than fifty (50) pounds and have a face area of not more than one hundred (100) square inches.

The sprinkling during rolling, if necessary, shall be in the amount and by equipment approved by the engineer.

213-3.10 SURFACE TEST. After the course is completely compacted, the surface shall be tested for smoothness and accuracy of grade and crown, and if any portions are found to lack the required smoothness or to fail in accuracy of grade or crown, such portions shall be scarified, reshaped, recompacted, and otherwise manipulated as the engineer may direct until the required smoothness and accuracy is obtained. The finished surface shall be such that it will not vary more than three-eighths (%) of an inch from the sixteen (16) foot straightedge applied to the surface parallel to the centerline and at right angles.

213-3.11 THICKNESS. The thickness of the base course shall be determined by depth tests or cores taken at intervals in such manner that each test shall represent no more than 300 square yards. When the base deficiency is more than one-half (2) inch, the contractor shall correct such areas by scarifying, adding satisfactory base mixture, rolling, sprinkling, reshaping, and finishing in accordance with these specifications. The contractor shall replace, at his expense, the base material where borings are taken for test purposes.

213-3.12 PROTECTION. Work on base course shall not be prosecuted during freezing temperature nor when the subgrade is wet. When the base material contains frozen material or the underlying course is frozen, the construction shall be stopped.

In general, hauling equipment may be routed over completed portions of the base course, provided no excessive damage results and provided that such equipment is routed over the full width of the base course to avoid rutting or uneven compaction. However, the engineer in charge shall have full and specific authority to stop all hauling over completed or partially completed base course when, in his opinion, such hauling is causing excessive damage. Any damage resulting to the base course from routing equipment over the base course shall be repaired by the contractor at his own expense.

213-3.13 MAINTENANCE. Following the final shaping of the material, the base shall be maintained throughout its entire length by the use of a standard road machine or motor grader and rollers until such time as, in the judgment of the engineer, the base meets the required density, is properly bonded, and is suitable for priming. After the mixing and shaping are completed, the base shall be confined to the specified width by banking enough shoulder material against the edges to prevent it from spreading under traffic. The

base shall be properly drained at all times. During this maintenance period, any deficiencies in thickness, composition, smoothness, or density shall be corrected in a satisfactory manner.

Before preparations have started for the application of a surface treatment or for a surface course, the base course shall be allowed to partially dry until the average moisture content of the full depth of base is less than eighty (80) percent of the optimum moisture of the base mixture. The drying shall not continue to the extent that the surface of the base becomes dusty with a consequent loss of binder. If during the curing period the surface of the base dries too fast, it shall be kept moist by sprinkling until such time as the prime coat shall be applied as directed.

METHOD OF MEASUREMENT

213-4.1 The yardage of sand-clay base course to be paid for shall be the number of cubic yards of base course material placed, bonded, and accepted in the completed base course. The quantity of base course material shall be measured in final position based upon depth tests or cores taken as directed by the engineer, or at the rate of one depth test for each 300 square yards of base course, or by means of average end areas on the complete work computed from elevations to the nearest 0.01 foot. On individual depth measurements, thicknesses more than one-half (1⁄2) inch in excess of that shown on the plans shall be considered as the specified thickness plus one-half inch in computing the yardage for payment. Base materials shall not be included in any other excavation quantities.

BASIS OF PAYMENT

213-5.1 The yardage of sand-clay base course measured as provided above shall be paid for at the contract unit price bid per cubic yard for sand-clay base course, which price and payment shall constitute full compensation for furnishing, loading, hauling, and placing the materials; for mixing, blading, sprinkling, shaping, and compacting; for reconditioning the underlying course and shoulders; for reconstruction of irregular surface, or deficient thickness, and for maintenance; for refilling test holes; for any required construction, repair, and obliteration of access roads; for all pit moves; for clearing, stripping, drainage, and clean-up of pits; for handling and disposal of unsuitable materials encountered in pit operations; and for all labor, equipment, tools, water, and incidentals necessary to complete the work.

Payment will be made under:

Item P-213-5.1 Sand-Clay Base Course-per cubic yard.

ITEM P-214 PENETRATION MACADAM BASE COURSE

(Emulsified Asphalt Type)

DESCRIPTION

214-1.1 This item shall consist of a base course composed of macadam, asphalt-bonded, constructed on a prepared underlying layer in accordance with these specifications and in conformity with the dimensions and typical cross section shown on the plans, and with lines and grades established by the engineer.

214-1.2 QUANTITIES OF MATERIALS PER SQUARE YARD. The finished thickness of the penetration macadam base shall be as specified or as shown on the plans. The quantities of aggregate and emulsified asphalt shall be as given in Table 1, opposite the particular thickness shown on the plans for the base. At the beginning of construction and during its progress, the individual weights of the various aggregates shall be varied and adjusted as directed by the engineer in accordance with field requirements.

TABLE 1.-Quantities of Materials per Square Yard

The weights given in Table 1 are approximate and are for aggregates having a bulk specific gravity of 2.65, as determined by the A. A. S. H. O. Method T-85. Proportionate corrections shall be made when the aggregates furnished have bulk specific gravities above 2.75 or below 2.55. In such cases the corrected amount shall be the product of the number of pounds shown in Table 1 multiplied by the ratio of the bulk specific gravity of the aggregate to 2.65.

In Table 1 the amounts of emulsion given are for stone aggregates. If the total aggregate is composed of slag, the gallons of emulsion shall be increased from fifteen (15) to twenty (20) percent.

MATERIALS

214-2.1 AGGREGATE. The coarse aggregate, key stone, and screenings shall be either crushed stone or crushed slag.

The crushed stone shall consist of hard, durable particles or fragments of stone, free from an excess of flat, elongated, soft or disintegrated pieces, dirt, or other objectionable matter, and shall have a percent of wear of not more than 45 at 500 revolutions, as determined by A. A. S. H. O. Method T-96 (Los Angeles Rattler Test).

The crushed slag shall be air-cooled blast furnace slag, and shall consist of angular fragments, reasonably uniform in density and quality, and reasonably free from thin, elongated, or soft pieces, dirt, and other objectionable matter. It shall weigh not less than sixty-five (65) pounds per cubic foot, and shall have a percent of wear of not more than 45 at 500 revolutions, as determined by A. A. S. H. O. Method T-96 (Los Angeles Rattler Test).

The crushed aggregate shall not show evidence of disintegration nor show a total loss greater than twelve (12) percent when subjected to five (5) cycles of the sodium sulphate accelerated soundness test using A. A. S. H. O. Method T-104.

Crushed stone and crushed slag for coarse aggregate, key stone, and screenings shall meet the requirements for gradation given in Table 2, using A. A. S. H. O. Method T-27.

TABLE 2.-Requirements for Gradation of Aggregate

Prior to final acceptance of the proposed aggregate to be used, the inherent characteristics of said aggregate relative to stripping shall be determined. This shall be done by preparing a test sample by immersing at least two (2) pounds of the aggregate in the emulsified asphalt for a period of approximately ten (10) minutes. After the sample has been prepared, it shall be spread out in a loose thin layer and placed in a constant temperature oven-controlled to 140° F. for a period of twenty-four (24) hours before testing. A suitable size sample (approximately one-half contents of container)