133 SECTION 304 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. 304 PORTLAND CEMENT TREATED BASE 134 Mix the components with suitable equipment until a uniform mixture is obtained. If equipment is used that requires more than one pass of the mixer, make at least one pass before any water is added to the material. At the time mixing is comp leted, the moisture content of the mixture shall not be in excess of 1% over optimum as determined by Test Method No. Nev. T236. The cement content of samples from the product of the roadmixing machine, or from mixtures spread on the roadbed shall not vary above or below the required cement content of more than 0.6 of a percentage point based on the mass of the aggregate as determined by Test Method No. Nev. T239.
304.03.03 Mixing —Plantmix Meth od. (a) General. Mix the components at a central mixing plant by either
batch mixing, using revolving blade or rotary drum mixers, or continuous mixing. Proportion the aggregate and cement either by mass or volume. Separate aggregates into two sizes and st ockpile each size separately. One stockpile shall contain aggregate of which not more than 20% is finer than the 4.75 mm (No. 4) sieve. The other stockpile shall contain aggregate of which at least 80% is finer than the 4.75 mm (No. 4) sieve. If aggregates are separated into more than two sizes, combine approved sizes that will meet the grading and other test requirements. Proportion water by mass or volume. Provide means by which to readily verify the amount of water per batch or the rate of flow for cont inuous mixing. The time of addition and the points at which water is introduced into the mixer, shall be as directed. At the time mixing is completed, the moisture content of the mixture shall not exceed optimum as determined by Test Method No. Nev. T236. Uniformly distribute cement throughout the aggregates during the mixing operation. Completely mix all the material. Correct dead areas in the mixer, in which the material does not move or is not sufficiently agitated, by either a reduction in the volume of material or by other adjustment. Proportion materials within the following tolerances: Aggregate masses or rate of feed ................................ ................................ ................................ ................................ .................. ± 5.0% Cement content of the complete dry mixture ................................ ................................ ................................ ................................ .. ± 0.4% Moisture content of the completed mixture ................................ ................................ ................................ ................................ ..... ± 1.0% Furnish weighing equipment as specified in Subsection 109.01.
b.Batch Mixing. Equip the mixer with a timing device which will indicate by a definite audible or visual signal the expiration of the mixing period. Use a timing device accurate to within 2 seconds. Equip the plant with a suitable automatic device for counting the number of batches. Mix until a homogeneous mixture of uniformly distributed and properly coated aggregates of unchanging appearance is produced. Weigh cement for each batch on scales separate and distinct from the aggregate batching scales. If volumetric proportioning is used, provide means for accurately calibrating the amount of material in each measuring bin.
c.Continuous Mixing. Draw the correct proportion of each aggregate size into the mi xer by an approved type of feeder, which will continuously supply the correct amount of aggregate in proportion to the cement. Equip the plant with approved metering devices that will introduce the cement and water into the mixer in specified proportions. Interlock and synchronize the metering devices and feeder as to maintain a constant rate of cement, water, and aggregates in specified proportions. When storage bins are used, equip bins with overflow chutes for each compartment. Provide a positive signal system that will automatically close down the plant when the level of material in any bin approaches the strike -off capacity of the feed gate. Do not operate the plant unless the signal system is working. Use mechanically or electrically driven aggregate f eeders. Directly connect aggregate feeders that are mechanically driven with the drive on the cement feeder. Equip the plant with satisfactory facilities for calibrating gate openings and metering devices by weighing check samples. Actuate aggregate feeder s that are electrically driven from the same circuit that serves the motor driving the cement feeder. Mix until a homogeneous mixture of uniformly distributed and properly coated aggregates of unchanging appearance is produced. PORTLAND CEMENT TREATED BASE 304 135 Equip the cement feeder wit h a positive weighing device.
304.03.04 Spreading. (a) General. Prepare and compact the surface to be covered with cement treated base to
grade and cross section. Dispose any material cut away in trimming for such grade and cross section in a satisfactory manner. Suitably protect materials mixed at a location off the roadbed against moisture loss while being transported. Spread materials without segregation. Immediately before spreading, moisten the area to be covered and keep moist, but not excessively w et. Where the required thickness is 150 mm (6 in.) or less, spread and compact the mixture in one layer. Where the required thickness is more than 150 mm (6 in.), spread and compact the mixture in two or more layers of approximately equal thickness. Do no t exceed a maximum compacted thickness of 150 mm (6 in.) in any one layer. Perform work on each layer in a similar manner. Keep the surface of the compacted material moist or prevent from drying by some approved methods until covered with the next layer. Cement treated base to be placed in inaccessible areas may be spread in one course by approved methods. After spreading, compact the material to the required lines, grades, and cross section by means of pneumatic tampers or with other compacting equipment.
b.Plantmix Method. Uniformly deposit the mixture on the roadbed to provide the required compacted thickness without resorting to spotting, picking up, or otherwise shifting the mixture. When placing material on the mainline, use a wire line grade cont rol. On areas other than the mainline, wire line grade control is optional. Spread the mixture in one operation with a self -propelled mechanical spreader ready for compaction without further shaping. Prevent segregation of materials. Equipment not propell ed by the unloading vehicle will be considered self -propelled. Provide the spreader with a screed that strikes off and distributes the material to the required width and to the surface tolerances specified. The screed shall be adjustable to the required cr oss section. Produce a finished surface texture of uniform appearance. If the spreader leaves ridges, indentations, or other objectionable marks in the surface that cannot be eliminated by rolling, or prevented by adjustments in operation, discontinue its use. Equip the spreader with a control system which will automatically control the placing and trimming of the material to the specified transverse slope and established longitudinal grade. Use control system that is automatically actuated from an indepen dent line and grade control reference on one or both sides of the roadbed. In case of failure of the control system, cease spreading operations until the system is repaired. Except as otherwise provided in this Subsection, do not use motor graders during spreading and compacting operations. Motor graders may be used to trim the edges and surface of the cement treated base after compaction in order to finish the base within the tolerances specified. On areas other than the mainline, with wire line grade control, motor graders may be used as self -propelled mechanical spreaders. When motor graders are used as spreaders, equip them with end wings on the blade, and lock the blade in a position normal to the direction of travel. Provide motor graders with cro ss slope and automatic grade controls that are capable of picking up grade from a wire control and from an external sensing wheel. Control the initial pass for final grade elevation by the wire line. Control subsequent passes by an electronic sensing devi ce capable of maintaining grade. In case of failure of the control system, the motor grader may be operated manually but only until the material on the roadbed at the time of breakdown has been placed. Reference points will be established at reasonable in tervals on both sides of the mainline. Where wire control is used on other lines, reference points will be established on one side. Furnish, place, maintain, remove, and dispose of all materials required to provide continuous line and grade control. In areas of transitions, sharp curves, short runs, or miscellaneous areas where the above methods for control of line and grade are impractical, use an approved placement method. 304 PORTLAND CEMENT TREATED BASE 136 Spread the mixed materials for the full planned width, unless traffic conditions require part width construction. Spread either by one spreader or by several spreaders operating in a staggered position across the subgrade. For the use of one spreader operating alternately on contiguous lanes, not more than one hour shall elapse between the time of placing material in adjacent lanes. Locate any longitudinal construction joints on lane lines.
304.03.05 Compaction. Accomplish rolling with a two -axle tandem steel roller weighing not less than 9 metric
tons (10 tons), or single or dual drum vibratory roller, and pneumatic tired rollers conforming to Subsection
401.03.04 Use roller sequence as directed.
Perform rolling in such a manner to eliminate bumps and irregularities and finish surface to the required grade and cross section within th e surface tolerances specified. Apply water without driving equipment over the uncompacted material. Commence rolling from the outer edge of the material. Lap subsequent rolling at least 25% over previously compacted material. Use steel -wheeled rollers for the finish rolling of each layer. Commence finish rolling from the outer edge and progress to compact the entire surface. Compact areas inaccessible to rollers to the required compaction by other means. The density of compacted cement treated bases s hall not be less than 92% 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.
304.03.06 Finished Surface. The finished surface of cement treated base shall be uniform and shall not
deviate at any point more than 9 mm (0.03 ft) from the bottom of a 3.6 m (12 ft) straightedge laid in any direction. Do not vary the finished surface more than 15 mm (0.05 ft) above or below the grade established. When Portland cemen t concrete pavement is to be placed on cement treated base, do not extend the finished surface above the grade established. Trim off all high spots to within the specified tolerance. Immediately after trimming, remove and dispose of excess material in an approved manner. Leave no loose material on the base. Roll the trimmed areas again. Do not use cleated equipment on new cement treated base unless street pads are used on cleats.
304.03.07 Time Requirements. Do not leave any mixture of aggregate, cement, and water that has not been
compacted undisturbed for more than 30 minutes. Not more than 2 hours shall elapse between the time water is added to the aggregate and cement and the time of completion of initial rolling. Not more than 3 hours shall elapse between the time water is added to the aggregate and cement and the time of completion of final compaction after trimming.
304.03.08 Construction Joints. When cement treated base operations are delayed or stopped for more than 2
hours, make a transverse ver tical construction joint in compacted material. Do not place additional mixture until the construction joint has been approved. Construct longitudinal joints in cement treated base by cutting vertically along the edge of the existing surface to a depth of approximately 75 mm (3 in.). Do not construct joint for at least one hour after final compaction. The material cut away may be disposed of in the adjacent lane to be constructed. Moisten the face of the cut joints in advance of placing the adjacent base.
304.03.09 Protection and Curing. Keep the surface moist at all times until the curing seal is applied. Use water
equipment which will apply moisture in a fog or mist type application, free of pressure at the surface being treated. Apply curing seal to th e completed top layer of cement treated base. Apply the curing seal as soon as possible, but not later than 24 hours after the completion of final rolling. The curing seal shall be Cutback Asphalt , Type MC-250, applied at an approved rate. Apply the curing seal according to Section 407. At the time of application of the curing seal, the surface shall be tightly knit, free from all loose material and shall contain sufficient moisture to prevent excessive penetration of the asphalt. If necessary, apply water to fill the surface voids immediately before the asphalt is applied. PORTLAND CEMENT TREATED BASE 304 137 Do not permit equipment or traffic on the cement treated base during the first 3 days (4 days if Type IP cement is used) after applying the curing seal. Apply sand blotter as directed to prevent excessive surface abrasion from traffic. When equipment or traffic is permitted on the cement treated base for the sole convenience of the Contractor, protection of the curing seal will not be paid for. Remove all loose sand from the cement treat ed base before any surfacing material is placed thereon.
304.03.10 Weather Limitations. Do not mix or place cement treated base while the atmospheric temperature
is below 2 C (35 F), or when conditions indicate that the temperature will fall below 2 C (35 F) for a sustained period of 4 hours within the next 24 hours. Do not place cement treated base on frozen ground. Protect base material from freezing and frost for a period of 5 days after placing. METHOD OF MEASUREMENT
304.04.01 Roadmix Method Designated for Use. Roadmix cement treated base aggregate will be measured
by the metric ton (ton). When mixed at a central mixing plant, the quantity of aggregate will be determined by weighing the completed mixture of aggregate, cement and water, and deducting from this mass the mass of the cement and water. Meter water and calibrate meters for mass. Mixing, hauling, spreading, and compacting cement treated base will be measured by the square meter (square yard).
304.04.02 Plantmix Method Design ated for Use. Plantmix cement treated base aggregate will be measured
by the metric ton (ton), less the mass of cement. The quantity of aggregate will be determined by weighing the completed mixture of aggregate, cement, and water (in the hauling vehicle b efore delivery), and deducting from this mass the mass of cement.
304.04.03 General. Cutback asphalt used for curing seal and sand blotter will be measured under Section 407.
Portland cement will be measured by the metric ton (ton) by the following metho ds:
a.Certified package mass.
b.Certified scale masses.
c.Certified mass certificates indicating the truck and trailer number, tare mass, gross mass, net mass, and date. The following requirements shall also apply:
1.Loaded transporting vehicles shall be occasionally weighed by project personnel before discharge of any material. The frequency in which the loaded vehicles are weighed will be determined.
2.Every empty transporting vehicle shall be weighed by project personnel before the vehicle l eaves the project.
3.The quantity of Portland cement used will be determined should a discrepancy arise between project masses of the loaded or unloaded vehicles, or both, and the certified mass certificates. BASIS OF PAYMENT
304.05.01 Roadmix Method Designated for Use. 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 shown in the proposal. Payment will be full compensation for the work pr escribed in this Section. Payment will be made under: Pay Item Pay Unit Roadmix Cement Treated Base Aggregate (dry) ................................ ................................ ................................ ............. Metric Ton (Ton) Portland Cement for Cement Treated Base ................................ ................................ ................................ ..................... Metric Ton (Ton) Mixing Cement Treated Base ................................ ................................ ................................ ....................... Square Meter (Square Yard) 304 PORTLAND CEMENT TREATED BASE 138 304.05.02 Plantmix Method Designated for Use. 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 shown in the proposal. Payment will be full compensati on for the work prescribed in this Section. Payment will be made under: Pay Item Pay Unit Plantmix Cement Treated Base Aggregate (wet) ................................ ................................ ................................ ............. Metric Ton (Ton) Portland Cement for Cement Treated Base ................................ ................................ ................................ ..................... Metric Ton (Ton) 139 SECTION 305 ROADBED MODIFICATION DESCRIPTION
305.01.01 General. This work consists of pulverizing, blending with cement , and compacting an existing
roadway. MATERIALS
305.02.01 General. Material shall conform to the following Sections and Subsections:
Portland Cement ................................ ................................ ................................ ................................ ................................ .... Section 701 Cutback Asphalt ................................ ................................ ................................ ................................ ...................... Subsection 703.03.03 Sand Blotter ................................ ................................ ................................ ................................ ............................ Subsection 705.03.05 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.
305.02.02 Gradation Requirements. Loosen and pulverize the existing roadway to conform to the following
sieve sizes: Sieve Size Percent Passing by Mass 75 mm (3 in.) ................................ ................................ .............. 100 50 mm (2 in.) ................................ ................................ ............ 95-100 CONSTRUCTION
305.03.01 Weather Limitations. Do not process for roadbed modification while the atmospheric temperature is
below 2 °C (35 °F), or when conditions indicate that the temperature will fall below 2 °C (35 °F) for a sustained period of 4 hours within 24 hours after fina l compaction. Do not proceed with the pulverization operation when the temperatures will not permit the processing operation to follow. If atmospheric temperatures fall below 2 °C (35 °F) for a sustained period of 4 hours within 24 hours, the Engineer wi ll determine if the processed material may remain in place. If the material is allowed to remain in place, reprocess with an additional 0.5% cement by mass. Perform such work at no cost to the Department.
305.03.02 Preparation of Roadbed. Pulverize the ex isting roadway to the depth necessary to construct the
roadbed modification as shown on the plans. Roll as directed with pneu matic tired roller and pregrade the pulverized material to within 25 mm (1 in.) of grade. Maintain the pulverized surface in an a cceptable condition, until the processing for roadbed modification begins. Restrict the pulverization operation to half roadway width at a time. Relay the pulverized material by one of the following methods and place public traffic thereon at the end of each working day:
a.Relay and satisfactorily compact the unprocessed pulverized material.
b.Add cement, process, spread, and compact the material, according to the requirements for the finished product. Do not pulverize more than 5 km (3 mi) in advance of the completed roadbed modification process. Distribute only as much Portland cement on the pulverized surface material and base as can be mixed and compacted within the same working day.
Source: Nevada Standard Specifications for Road and Bridge Construction, 2014 Edition. Pages 139–144 of 610.