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 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, ten (10) ton three-wheel rollers 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 threeeighths (%) of an inch when tested with a sixteen (16) foot straightedge, the irregular surface shall be loosened 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. 210-3.6 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 are 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 center line and at right angles. 210-3.7 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 (1⁄2) 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. 210-3.8 PROTECTION. Work on the base course shall not be prosecuted during freezing temperatures nor when the subgrade is wet. When the aggregates contain frozen materials 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 763591°-48-11 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. 210-3.9 MAINTENANCE. Following the final shaping of the material, the base shall be maintained throughout its entire length and width 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 is 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 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 210-4.1 The quantity of caliche 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 (2) inch in excess of that shown on the plans shall be considered as specified thickness plus one-half (2) inch in computing the yardage for payment. Base material shall not be included in any other excavation quantities. BASIS OF PAYMENT 210-5.1 The quantity of caliche base course measured as provided above shall be paid for at the contract unit price per cubic yard for caliche base course, which price and payment shall constitute full compensation for furnishing, loading, hauling, and placing the ma terials; 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 the 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-210-5.1 Caliche Base Course-per cubic yard. ITEM P-211 LIME ROCK BASE COURSE DESCRIPTION 211-1.1 This item shall consist of a base course composed of lime rock constructed on the prepared 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. 211-2.1 MATERIALS. MATERIALS The lime rock base course material shall consist of fossiliferous limestone of uniform quality, and shall not contain hard or flinty pieces which will prevent attainment of a smooth surface free from pits and pockets. The rock shall show no tendency, to air slack or undergo chemical change when exposed to the weather. The material when watered and rolled shall be capable of being compacted into a dense and well-bonded base. The oölitic type of lime rock shall meet the following requirements: Carbonates of calcium and magnesium-not less than 80 percent. Oxides of iron and aluminum-not more than 2 percent. The combined amount of carbonates, oxides, and silica shall be at least 97 percent. All other types of lime rock shall contain not less than ninety-seven (97) percent of carbonates of calcium and magnesium. The chemical analysis of lime rock shall consist of determining the silica insoluble, iron oxide, and alumina by solution of the sample in hydrochloric (HCL) acid, evaporating, dehydrating, redissolving the residue and neutralizing with ammonium hydroxide, filtering, washing, and igniting the residue lime rock. The difference between this insoluble matter and one hundred (100) percent is reported as carbonates of calcium and magnesium. The lime rock shall not contain more than three (3) percent of roots, leaf mold, organic, or foreign matter, and shall be obtained from pits from which all overburden has been removed previous to blasting and quarrying. The gradation of the lime rock shall meet the following require ments: 31⁄2-inch... Sieve designation Percent by weight passing square mesh sieves 100 50-100 All fine material shall consist entirely of dust of fracture. CONSTRUCTION METHODS 211-3.1 SOURCES OF SUPPLY. All work involved in cleaning and stripping pits, including handling unsuitable material encountered, shall be performed by the contractor at his own expense. The lime rock shall be obtained from sources that have been approved. The pits as utilized shall be operated in such a manner that a clean and uniform material is secured. 211-3.2 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. Powered rollers shall be of the three-wheeled type, weighing not less than ten (10) tons. Rollers shall have a rear-wheel compression of not less than 330 pounds per linear inch of tire width and shall be equipped with adjustable scrapers. The roller shall be maintained in good condition and operated by an experienced rollerman. 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. Road machines shall weigh not less than three (3) tons and shall have a wheel base not less than fifteen (15) feet and a blade not less than ten (10) feet. Road machines shall not be pulled with rollers. 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. 211-3.3 PREPARING UNDERLYING COURSE. Before any rock base course material is placed, underlying course shall be prepared and conditioned as specified. The course shall be checked and accepted by the engineer before placing and spreading operations are started. Any ruts or soft, yielding places that appear by reason of improper drainage conditions, or hauling, or from any other cause, shall be corrected and rolled to the required compaction before the base course is placed thereon. 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 lime rock 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. |