Where a hard and compact surface is encountered, whether or not previously bituminized or otherwise concreted, which, as determined by the Engineer, would be weakened or damaged by scarifying and blading, all depressions and breaks shall be corrected by patching and leveling to conform with the surrounding surface. The Engineer will direct the type of material to be used for patching from materials inIcluded in the contract. Any soft, unstable or other unsuitable materials in the roadbed shall be removed as directed and replaced with suitable material or stabilized by means of chemical additives shown in subsection 305.03 and included in the bid schedule, as directed by the Engineer. The material shall be placed in loose layers of not more than 8 inches in depth and each layer shall be thoroughly compacted as provided above. The surface shall be finished in reasonably close conformity to the grade and cross section of the adjoining undisturbed roadbed. Method of Measurement 306.03 Reconditioning will be measured by the station or by the mile as indicated on the plans and shall include all blading of ditches and shoulders if required, the scarifying and pulverizing of the existing roadbed, the preparation, incorporation, or conservation of existing bituminous materials, the compacting of the roadbed, the finishing of the surface, and the maintenance of the completed surface if applicable. Water will be measured by the M G. (1,000 gallons) by means of calibrated tanks or distributors or by means of accurate water meters furnished by the contractor. Only that water which is used in mixing materials or ordered by the Engineer to keep the surface moist will be measured for payment. Removal and replacement of unsuitable material in the roadbed will be measured for payment under section 203. Patching material will be measured for payment under the applicable sections. Chemical additives ordered by the Engineer and acceptably incorporated into the roadbed will be measured by the ton. Basis of Payment 306.04 The accepted quantities of reconditioning determined as provided above will be paid for at the contract unit price per station or mile for reconditioning and per M G. (1,000 gallons) for water, complete in place, which price and payment will be full compensation for the work of this section. 306(3) Water for reconditioning of roadbed_ M G. 306(4) Chemical additive(-) for recon ditioning of roadbed Section 307.-RESERVED Ton. Section 308.-PORTLAND CEMENT TREATED BASE Description 308.01 This work shall consist of constructing one or more courses of a mixture of aggregate and portland cement on a prepared surface in accordance with these specifications in reasonably close conformity with the lines, grades, thicknesses and typical cross sections shown on the plans or established by the Engineer. Unless otherwise provided, the Contractor may use either the travel plant or central plant method as described below. Materials 308.02 Imported aggregate, if required, shall meet the requirements of the special provisions. Other materials shall conform to the requirements specified in the following subsections: Construction Requirements 308.03 Travel Plant Method. The aggregate obtained from scarifying the existing roadway or from other sources shall be pulverized until at least 75 percent of all material other than stone or gravel will pass a No. 4 sieve prior to compaction. Any material retained on a 3-inch sieve and other unsuitable material shall be removed. If additional material is specified, it shall be blended with the existing material. All butt joints at existing pavement or other structures shall be cleaned prior to mixing. The subgrade shall support all equipment required in the construction of the base. Soft or yielding areas shall be corrected prior to mixing. The aggregate to be treated shall be placed in a uniform windrow or spread to a uniform thickness to the width required. The specified quantity of portland cement shall be applied uniformly in a trench on top of the windrow or spread uniformly over the aggregate. Spread cement that has been lost shall be replaced, without additional compensation, before mixing is started. Mixing shall be accomplished by means of a mixer that will thoroughly blend the aggregate with the cement and water. The mixer shall be equipped with a water metering device that will introduce the required quantity of water during the mixing cycle. If more than one pass of the mixer is required, at least one pass shall be made before water is added. Other mixing methods and equipment may be used for areas consisting of 10,000 square yards or less, when approved. 308.04 Central Plant Method. The aggregate shall be proportioned and mixed with cement and water in a central mixing plant. The plant shall be equipped with feeding and metering devices which will introduce the cement, aggregate, and water into the mixer in the quantities specified. Mixing shall continue until a uniform and intimate mixture of aggregate, cement and water has been obtained. Mixed material shall be transported to the roadway in suitable vehicles and spread on a moistened subgrade or base in a uniform layer by a self-propelled or other approved spreader. Not more than 60 minutes shall elapse between the start of mixing and the time of starting compaction of the cement treated mixture on the prepared subgrade. 308.05 Compaction and Finishing. After the cement treated mixture has been spread, the mixture shall be compacted to at least 95 percent of the maximum density determined in accordance with AASHO T 134. Compaction of the completed base will be determined in accordance with AASHO T 147, T 191, T 205, or other approved tests, including the use of properly calibrated nuclear testing devices. A correction for coarse particles may be made in accordance with AASHO T 224–671. Any mixture of aggregate, cement and water that has not been compacted shall not be left undisturbed for more than 30 minutes. The percentage of moisture in the completed mixture shall not vary from the optimum to plus 5 percentage points, as determined by AASHO T 134. The compaction shall be completed within two hours of the time water is added to the mixture. The compacted surface shall be brought to the required cross section. All irregularities shall be removed and the surface recompacted. 308.06 Protection and Curing. After the cement treated base has been finished it shall be kept moist continuously until sufficient bituminous curing material has been applied to provide a protective film over the treated base. This film shall be maintained until the treated base is protected by a subsequent course. 308.07 Weather Limitations. Mixing shall not be done when the aggregate or subgrade is frozen. The air temperature shall be at least 40° F. in the shade during all operations. The finished course shall be protected from freezing for 7 days after construction. Method of Measurement 308.08 Portland cement treated base will be measured as follows: Portland cement by the barrel (bbl.) of 376 pounds. Water by the M G. (1,000 gallons) by means of calibrated tank trucks or by means of accurate meters. Only that water which is used in the mix will be measured. Imported aggregate by the ton or cubic yard. Moisture present in the aggregate will be deducted. 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 gravity of available alternative materials. No adjustment in contract unit price will be made for variation in quantity due to differences in specific gravity of the material actually used. Processing the base by the station, mile, or square yard. Bituminous curing material by the ton or gallon. Basis of Payment 308.09 The accepted quantities of portland cement treated base, determined as provided above, will be paid for at the contract unit price per barrel (bbl.) for portland cement, per M G. for water, per ton or cubic yard for imported aggregate, per station, mile, or square yard for processing cement treated base and per ton or gallon for bituminous curing material complete in place. designate alternative types of aggregates to be bid on by weight. Section 309.-PORTLAND CEMENT CONCRETE BASE 309.01 This work shall consist of constructing a course of portland cement concrete base, with or without reinforcement as specified, on a prepared surface in accordance with these specifications, in reasonably close conformity with the established lines, grades and typical cross sections shown on the plans or established by the Engineer. Materials 309.02 Materials. Materials shall conform to the requirements specified in the following subsections: |