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 mixture of aggregate, cement and water has been obtained. Mixed material shall be spread on a moistened subgrade or base in a uniform layer by approved equipment. 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 a density of not less than 95 percent of the maximum density determined in the field on a sample of cement-aggregate mixture obtained from the area being processed at the time compaction begins, in accordance with AASHTO T 134. Inplace field density determinations will be made in accordance with AASHTO T 191, T 205, or other approved method. The use of AASHTO T 224 to correct for oversize particles may be required. 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 be in a range from the optimum moisture content of the mixture to ±2 percentage points, as determined by AASHTO T 134. The compaction and finishing shall be completed within 2 hours of the time water is added to the mixture. The compacted surface shall be at proper cross section, smooth, dense, and free of compaction planes, ridges or loose material. 308.06 Protection and Curing. The completed cement-treated base shall be cured with a bituminous curing seal applied as soon as possible after the completion of final rolling. The surface shall be kept moist until the seal is applied. Curing seal shall be applied at a rate between 0.10 and 0.25 gallon per square yard of surface. The exact rate will be determined by the Engineer. The curing seal will be applied in sufficient quantity to provide a continuous film over the base. The film shall be maintained at least 7 days unless the treated base is protected by a subsequent course. All cement-treated base shall be protected from freezing for a period of 5 days after placing, whenever the atmospheric temperature falls below, or is expected to fall below, 32°F. The Contractor shall be responsible for adequate maintenance of the base at all times, whether constructed under traffic or not. 308.07 Weather Limitations. Cement-treated base shall not be mixed or placed while the atmospheric temperature is below 35°F or when conditions indicate that the temperatures may fall below 35°F within 24 hours. Cement-treated base shall not be placed on frozen subgrade or mixed when the aggregate is frozen. 308.08 Surface Tolerance. Surface requirements shall be as specified in subsection 301.05. 308.09 Method of Measurement. Portland cement treated base will be measured by the square yard or as follows: Portland cement by the ton or hundredweight. Water by the M.G. (1,000 gallons) unit in tanks or tank trucks or by means of accurate meters. Only that water which is used in the mix will be measured. Water will be paid for under Section 207. Imported aggregate by the ton or cubic yard. 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 308.10 The accepted quantities of portland cement treated base, determined as provided above, will be paid for at the contract unit price per unit of measurement, respectively, for each of the particular pay items listed below and shown in the bid schedule. These prices and payments shall be full compensation for furnishing and placing all materials, including all labor, equipment, tools and incidentals necessary to complete the work prescribed in this section. 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: Fly ash may be substituted for a portion of the portland cement at the option of the Government based on laboratory tests to determine the optimum amount. Construction Requirements 309.03 Proportioning. Proportions for concrete mix will be based on a predetermined cement content of 564 pounds per cubic yard, in accordance with subsection 501.03. 309.04 Equipment. The equipment shall meet the requirements of subsection 501.04. 309.05 Construction Requirements. The construction methods used shall meet the applicable requirements of subsection 501.03B through 501.17. 309.06 Surface Finishing. The surface of the concrete shall be broomed and slightly roughened. The surface shall be finished so that there will be no deviation of more than 3% inch between any two contact points when tested with a 10-foot straight edge placed parallel to the center line. 309.07 Tolerance in Base Thickness. The procedures for concrete base thickness determination will be in accordance with subsection 501.19. Method of Measurement 309.08 Portland cement concrete base will be measured by the square yard complete in place. The width for measurement will be the width of the payment shown on the plans and additional widening where called for, or as otherwise directed and measured horizontally. The length will be measured horizontally along the centerline of each roadway or ramp. Basis of Payment 309.09 (a) General.-The accepted quantities of Portland Cement Concrete Base, determined as provided above, will be paid for at the contract unit price per square yard for portland cement concrete base, which payment will be full compensation for furnishing and placing all materials, including any reinforcing except as provided in subsection 309.09(c), dowels and joint material; provided, however, for any base found deficient in thickness by more than 0.2 inch but not more than 1.0 inch, only the reduced price stipulated below will be paid. No additional payment over the unit contract bid price will be made for any base which has an average thickness in excess of that shown on the plans. Payment will be made under: Pay item 309(1) Plain portland cement concrete base 309(2) Reinforced portland cement concrete base . Pay unit Square yard. (b) Price adjustment.-Price adjustments for concrete base found to be deficient in thickness will be made in accordance with subsection 501.19(c). (c) Reinforcement.- Payment for a bottom layer of reinforcement, if called for in approach slabs at structures, will not be considered included in the foregoing price and payments but the weight of such reinforcement will be included in the weight to be paid for under Section 554. Section 310.-AGGREGATE SURFACE COURSE Description 310.01 This work shall consist of gravel or crushed aggregate, placed 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. Materials 310.02 Aggregate. Aggregate shall meet the requirements of subsection 703.06 for the type and grading designated in the bid schedule. Aggregates will be tested for acceptance based on samples taken in accordance with subsection 304.02. 310.03 Chemical Additives. Chemical additives if required, shall meet the applicable requirements of the following subsections: 310.04 Construction, acceptance, and payment shall be in accordance with subsections 304.05 through 304.08. Method of Measurement 310.05 Aggregate surface course will be measured by the ton or cubic yard. 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 differences in the specific gravity of the material actually used. Chemical additives will be measured by the number of tons furnished and actually applied. Basis of Payment 310.06 The accepted quantities of aggregate surface course, of the size and type specified, determined as provided above, will be paid for at the contract prices per ton or cubic yard for aggregate, per ton for chemical additives, 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, except pay factors will be applied in accordance with 304.04. 311.01 Section 311.-STOCKPILED AGGREGATES Description This work shall consist of furnishing and placing aggregates in stockpiles in reasonably close conformity with these specifications at the locations shown on the plans or in the special provisions or as directed and approved by the Engineer. Materials 311.02 Stockpiled aggregates shall conform to the requirements of the section indicated in the pay item in the bid schedule. The aggregate will be tested for acceptance at the crushing plant. Construction Requirements 311.03 The stockpile sites, as staked by the Engineer, shall be prepared by clearing and disposing of all trees, stumps, brush, and debris as provided in Section 201. The entire stockpile site shall be graded, shaped, and compacted to a reasonably uniform cross section that will drain satisfactorily. Approved compaction equipment shall compact the floor full width with a minimum of three complete passes. Only when ordered by the Engineer shall the height of the piles or their average depth be less than 20 feet. The side slopes shall not be flatter than 12:1. Stockpiling of aggregates shall be in accordance with subsection 106.06. Method of Measurement 311.04 The quantity of aggregate to be paid for will be the number of cubic yards or tons as ordered and placed in authorized stockpiles. When payment by the cubic yard is called for in the bid schedule, completed stockpiles will be measured and computed by the average end area method. No allowance will be made for settlement or shrinkage. 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 differences in the specific gravity of the material actually used. Preparation of stockpile sites will be measured on an area basis and will be the number of acres and fractions thereof acceptably constructed within the limits shown on the plans or as staked by the Engineer. Basis of Payment 311.05 The accepted quantities, determined as provided above, will be paid for at the contract price per unit of measurement for each pay item that is shown in the bid schedule. The cost of constructing, stabilizing or surfacing, and maintaining the approach roads to any stockpile site will not be paid for but shall be a subsidiary obligation of the Contractor. When the bid schedule does not contain an estimated quantity for "Preparation of Stockpile Site", the work will not be paid for directly but will be considered as a subsidiary obligation of the Contractor. Payment will be made under: 311(1) Stockpiled aggregate, section grading... Pay unit Ton. Acre |