131 SECTION 302 DESCRIPTION
302.01.01 General. This work consists of constructing aggregate base courses on a prepared surface.
MATERIALS
302.02.01 General. Material shall conform to the following Subsections:
Type 1 Class A Aggregate Base ............................................................................................................................. Subsection 704.03.02 Type 2 Class A Aggregate Base ............................................................................................................................. Subsection 704.03.04 Type 3 Class A Aggregate Base ............................................................................................................................... Subsection 704.03.06 Type 1 Class B Aggregate Base ............................................................................................................................. Subsection 704.03.03 Type 2 Class B Aggregate Base ............................................................................................................................. Subsection 704.03.05 Type 3 Class B Aggregate Base ............................................................................................................................. Subsection 704.03.07 CONSTRUCTION
302.03.01 Subgrade Preparation. Correct and compact any ruts, holes, defects, or soft yielding places which
occur in the subgrade or subbase to required density and stability before placing an aggregate base course thereon. Make the above mentioned repairs at own expense, except as provided for in Subsection 203.03.02.
302.03.02 Spreading Class A Aggregates. Spread the aggregate in one operation ready for compaction
without further shaping except for trimming to correct minor deficiencies as hereinafter specified. Use a self-propelled spreader with a screed that strikes off and distributes the material to the required width and to the surface tolerances hereinafter set forth. The screed shall be adjustable to the required cross section and capable of spreading 3.6 m (12 ft) in width. Screed action includes any cutting, oscillating, or other practical motion that produces a finished surface texture of uniform appearance. Equipment not propelled by the unloading vehicle will be considered self-propelled. In narrow trench widenings, aggregate base course may be placed with self-propelled trench widening spreaders. If the spreader leaves ridges, indentations, or other objectionable marks that cannot be prevented by adjustments or eliminated by rolling, discontinue its use. Equip the spreader with a control system which will automatically control the trimming of the base material to the specified transverse slope and established longitudinal grade. The control system shall be automatically actuated from an independent line and grade control reference through a system of electronically controlled mechanical sensors which will maintain the trimmer screed at the proper transverse slope and at the proper elevation to obtain the required surface. In case of failure of the control system, operate the trimmer by mechanical control only until the material on the roadbed at the time of breakdown is place d. Motor graders will not be considered to be self-propelled mechanical spreaders unless they are equipped with end wings on the blade, have the blade locked in a position normal to the direction of travel, and are equipped with cross slope and automatic grade controls that are capable of picking up grade from a wire control, and from an external sensing wheel. When motor graders are used, control the initial pass for final grade elevation by the wire line. Control subsequent passes by an electronic sensing device capable of maintaining grade. Reference points will be established on one side of the roadway at reasonable intervals. Furnish, place, maintain, remove, and dispose of all materials required to provide continuous line and grade control to the placing machine. Aggregate bases, placed on road approaches and connections, street intersection areas, median strip areas, shoulder areas, and at locations which are inaccessible to the spreading equipment, may be spread in one or more layers by any means to obtain the specified results. Other than previously provided in this Subsection, the use of motor graders will not be permitted during depositing, spreading and compacting operations, except as follows:
a.Motor graders may be used to correct unavoidable segregation at edges and to trim the surface of the aggregate base after compaction in order to finish the base within the tolerances specified. 302 AGGREGATE BASE COURSES 132 (b) When the area of the base is small or irregular, and it is impractical to use self -propelled spreadin g equipment, the base material may be spread by motor grader or other approved methods.
302.03.03 Spreading Class B Aggregates. Deposit the aggregate uniformly on the approved subgrade by
means of the hauling vehicle with or without spreading devices. Tho roughly blade -mix the deposited base course material to full depth of the layer by alternately blading the entire layer to the center and back to the edges of the road. Spread and finish to the required cross section by means of a self -propelled pneumatic -tired motor grader. The aggregate may be spread with a self -propelled spreader subject to the requirements of Subsections
302.03 02, and 302.03.04.
302.03.04 Watering and Mixing Class A Aggregates. Mix the base course material and water in a mixer. Add
water during the mixing operation by means of spray bars in the amount necessary to provide the optimum m oisture content for compacting. Transport after mixing to a uniform homogeneous appearance. Place the base material on the roadbed as provided for in S ubsection 302.03.02. If the material has dried appreciably before final compacting, add additional water by means of a pressurized water truck to assist in compaction and to prevent raveling.
302.03.05 Watering Class B Aggregates. Apply water before and d uring all blading and processing
operations to moisten the material sufficiently to prevent segregation of the fine and coarse particles. Apply water during the compaction and maintenance stages in sufficient amounts to assist in compaction and prevent rav eling.
302.03.06 Compaction. Compact immediately following the spreading operation. Do not place the mixture in a
layer exceeding 150 mm (6 in.) in compacted thickness. If vibratory compaction equipment is used, the compacted thickness of any one layer ma y be increased to 200 mm (8 in.). Aggregate bases, placed on road approaches and connections, street intersection areas, median strip areas, shoulder areas, and at locations which are inaccessible to the spreading equipment, may be spread in one or more la yers by any means. Compact each layer to not less than 95% of the maximum density as determined by Test Method No. Nev. T10 8. The in -place density will be determined by Test Method No. Nev. T102 or T103. Recompaction to the specified density may be requir ed before placement of any subsequent course and no additional compensation will be allowed for such recompaction.
302.03.07 Tolerance for Aggregate Base Courses. When a 3.6 m (12 ft) straightedge is laid in any direction,
the finished surface shall not d eviate at any point more than 12 mm (0.04 ft) from the bottom thereof. METHOD OF MEASUREMENT
302.04.01 Measurement. Aggregate base will be measured by the cubic meter (cubic yard) or metric ton (ton).
The mass of material will be determined by deductin g from the mass of material delivered to the work, the mass of water in excess of optimum plus one percentage point. Optimum moisture will be determined by Test Method No. Nev. T10 8. Moisture content will be determined by Test Method No. Nev. T112. The mas s of water thus deducted will not be measured for payment. BASIS OF PAYMENT
302.05.01 Payment. The accepted quantities, measured as provided above, will be paid for at the contract
price per unit of measurement for the pay items listed below that are sho wn in the proposal. Payment will be full compensation for the work prescribed in this Section. Payment will be made under: Pay Item Pay Unit (type) Class A Aggregate Base ................................ ................................ ............................. Cubic Meter (Cubic Yard), Metric Ton (Ton) (type) Class B Aggregate Base ................................ ................................ ............................. Cubic Meter (Cubic Yard), Metric Ton (Ton) 133 SECTION 304 PORTLAND CEMENT TREATED BASE DESCRIPTION
304.01.01 General. This work consists of constructing one or more courses of a mixture of aggregate and
Portland cement on a prepared surface. MATERIALS
304.02.01 General. Material shall conform to the following Sections and Subsections:
Portland Cement .................................................................................................................................................................... Section 701 Cutback Asphalt ...................................................................................................................................................... Subsection 703.03.03 Emulsified Asphalt ................................................................................................................................................... Subsection 703.03.04 Aggregate for Portland Cement Treated Base ......................................................................................................... Subsection 704.03.08 Water ..................................................................................................................................................................................... Section 722 Portland cement may be either Type I, Type IP “blended,” Type II, or Type V. The limitation on the amount of alkali in cements is hereby waived. CONSTRUCTION
304.03.01 Proportioning. Apply Portland cement to the mineral aggregate at a rate of 2% to 4.5% by mass of
the dry mineral aggregate. Any allowable variations hereinafter set forth are to be inclusive of the above stated percentages. The exact rate of application of cement will be determined. The cement content will be determined by testing the fresh, moist cement aggregate mixture, by Test Method No. Nev. T239. Add sufficient cement to provide a minimum compressive strength of 5.2 MPa (750 psi) at 7 days as determined by Test Method No. Nev. T236. The method of mixing to be used, either plantmix or roadmix, shall be designated in the contract documents.
304.03.02 Mixing —Roadmix Method. (a) Depositing Untreated Aggregate. Deposit untreated aggregate on
the prepared area by means of spreader boxes equipped with a readily adjustable strike-off device. Do not mix aggregate with roadbed material that is not to be treated.
b.Mixing. Mix the components either on the roadbed or at a location off the roadbed by the roadmix method or the plantmix method. For the plantmix method, all the requirements in Subsection 304.03.03, will apply, with the following exceptions: 1.The separation of aggregates into two sizes and storing in separate stockpiles will not be required. 2.The 0.4 of a percentage point variation in the cement content will be increased to 0.6 of a percentage point. For the roadmix method, use an approved roadmixing machine of the pugmill, auger, or other type. Design the machine to pick up the material to be mixed from the windrow or blanket so that during at least 50% of the mixing cycle all the material is picked up and mixed while separated from the mixing table. Furnish cement in bulk. Flatten or slightly trench the tops of windrowed aggregate to receive the cement. Distribute cement, by mechanical equipment, on the aggregate in a layer of uniform thickness. Calibrate each load in the spreading equipment so the average rate of spread can be determined. Do not vary the rate of cement spread per linear meter (linear foot) of windrow or blanket more than 10% from the designated rate. Spread the cement upon the aggregate an acceptable distance ahead of the roadmixing operations. Use a roadmixing machine with provisions for introducing water at the time of mixing, through a metering device or by other approved methods. Apply the water by controls that will supply the approved quantity of water to produce a completed mixture with a uniform moisture content. Leakage of water from equipment will not be permitted. Where the material is to be spread and compacted in two or more layers, mix material for each layer separately.
Source: Nevada Standard Specifications for Road and Bridge Construction, 2014 Edition. Pages 137–138 of 610.