General requirements for mix production and construction of asphalt concrete pavement courses are included in Item 401. The Contractor responsibilities in supplying and placing a quality asphalt pavement are summarized in C&MS 401.01 paragraph 3.
Other specific requirements for flexible pavement production, quality control, and mix design are included in Item 402 Asphalt Concrete Mixing Plants, Item 403 Asphalt Concrete Quality Control and Acceptance, and Item 441 Contractor Mix Design and Quality Control - General. Requirements for the specific pavement courses are found in the specifications under the contract item designation (301, 442, 446, 448 etc.).
The quarterly posting of Supplemental Specification (SS) 800 on ODOT’s website is used to update the C&MS. Plan sets list the SS800 that is in effect for every project. Check the plan set to ensure you are using the correct SS800 posting since specifications change over time.
Asphalt concrete is a mixture of aggregate and asphalt material. The asphalt material used in these mixtures has a relatively high viscosity at normal temperatures. It is necessary to heat the aggregate and asphalt material to permit mixing, placing, and compacting.
Asphalt concrete may be used in new construction as the entire pavement structure or it may be used with other materials in a layered pavement structure. Extensive use of asphalt concrete is made for rehabilitating existing pavements by resurfacing or widening and resurfacing. Asphalt concrete is particularly adaptable to this type of work, where disruption of normal traffic flow must be kept to a minimum. Although written with reference to new construction, the instructions contained herein also apply to rehabilitation construction.
Asphalt concrete mixtures are produced in a central proportioning and mixing plant. At the plant, aggregate is dried and heated to the mixing temperature and combined with the specified asphalt material. On completion of mixing, the asphalt mixture is discharged directly into trucks, or conveyed to surge bins or silos, from which trucks are loaded for transport to the project.
Asphalt concrete is placed by mechanical pavers. After it is placed, the mixture must be compacted using the proper compaction equipment before it cools and becomes unworkable.
Item 403.03 requires the Contractor to provide a FQCS, who is a company employee who is at the paving site and is responsible for the quality of the asphalt being placed. The FQCS is responsible for identifying problems (see C&MS 401.01 paragraph 3) with the placement and immediately works to make corrections. Address all field quality issues with the FQCS and document all problems and all corrections. When the FQCS is not responsive, refer the problem to the Engineer for resolution. An FQCS can have his approval removed for failure to perform his duties. A list of approved FQCS personnel, by contractor, can be found on ODOT’s website.
The Inspector assigned to the placing of asphalt concrete should closely observe the placing of each type of mixture for indications of deficiencies in the mixture composition. If the mixture appears to be deficient in any of the following respects, notify the District plant monitor and the FQCS immediately, and note on the Inspector’s Daily Report. The Engineer should be consulted when there is mix deficiencies that need addressed. In some cases, production should cease immediately.
A Job Mix Formula (JMF) is submitted by the Contractor using the contract mix specifications for the contract asphalt concrete (446, 448, etc.). The Laboratory must provide conditional approval of all JMFs before production of any asphalt concrete. A JMF is not considered “approved” until it has been used successfully in the field. The JMF provides the proportions of the aggregates and Reclaimed Asphalt Pavement (RAP), Reclaimed Asphalt Shingles (RAS), and binder content, along with the optimal compaction temperature for the asphalt mix. This information is used in quality control for production and in field inspection. The Contractor quality control requirements for asphalt concrete are provided in Item 403.
Laboratory personnel must inspect and approve the mixing plant that will be used by the Contractor prior to the production of any asphalt concrete. Specification Item 402 and Supplement 1101 provides detailed requirements for asphalt mixing plants.
There are specific requirements for air and surface temperatures in Item 401.06 that must be met before paving can start. In all cases, the existing surface to be paved must be dry and with weather conditions that allow proper handling placement and compaction. Table 401.06-1 provides minimum surface temperature requirements based on the thickness of the course being placed.
This specification prohibits Contractors from scheduling placement of a surface course with a polymer modified asphalt binder after November 1, regardless of the pavement or air temperature. Although the Department, in certain circumstances, may allow the placement of a polymer modified surface course after November 1, this practice should be avoided if at all possible. Ensure the Engineer has concurred with any decisions that conflict with this prohibition. Where the Engineer does allow paving after November 1, ensure the Contractor is taking all precautions to ensure complete roller coverage before the mix cools below the laboratory, compaction temperature stated on the approved JMF.
· When taking a reading in the sun, place the thermometer on the pavement and then shade that area with a clipboard, cardboard, or other available shading material. Take the temperature reading after approximately 3 minutes. The intent is not to shade the area to allow it to cool, but to protect the thermometer from obtaining a false reading due to direct exposure to the sun.
· A new surface temperature should be taken when the existing pavement surface material changes (asphalt concrete to Portland cement concrete or vice versa) to ensure that the new surface meets the minimum temperature specification. If this specification is not met, paving operations must be discontinued until the surface reaches specification temperature. Paving operations may be moved to a different area of the project where the surface meets minimum specification temperature.
Placing thin, surface courses at temperatures near the applicable temperature limits may require the Contractor to employ special precautions to produce a satisfactory surface. These precautions include avoiding paver stops, keeping the rollers close to the paver, adding additional rollers, and providing proper insulation for the trucks hauling the material.
It is the Department’s responsibility to instruct the Contractor to stop paving operations in the event of rain. It is the Contractor’s responsibility to stop plant production. If the Contractor will not stop placement, notify the Engineer.
During a rain event, a load of material in the process of being dumped into the paver may be placed with the requirement that the rollers follow closely behind the paver and a construction joint is formed at the end of the run. Do not allow waiting trucks to be dumped and placed. The material in the waiting trucks will retain sufficient heat for proper placing and compacting for an hour or more depending on the ambient temperature. Water can be kept from accumulating on the covers of the trucks and draining into the asphalt mixture by raising the truck beds slightly. These loads may be placed when conditions improve if the asphalt temperature is acceptable and the surface being paved is in a reasonably dry condition.
The Contractor is required to notify the Engineer at least 24 hours before starting paving on a project. It is a recommended practice for the Engineer to call for a meeting to discuss the material and equipment to be used.
Notify the Contractor when deficiencies are found. When corrections are not satisfactory and difficulties persist, the vehicle in question should be removed from the project. Contact the testing office with any issues.
The Contractor is to provide a place off the project for cleaning trucks when hauling polymer modified asphalt binder mixes or when material is sticking to the truck bed. If the sticking to the truck bed is determined to be from excessive cooling of the mix, the Engineer will require an insulated bed.
Each load of asphalt is delivered to the project accompanied by a plant ticket with the load tonnage. The plant ticket must contain the date; project number; load gross, tare, and net weight; the JMF and material identification; producer name; producer location or plant number; and the time the truck left the plant. When the load is accepted at the paving site, the Inspector records the placement location and initials the ticket.
Asphalt pavers shall be self-propelled, mechanical spreading and finishing equipment, provided with a screed assembly capable of distributing the material to the full width of the lane being paved. The type of equipment suitable for spreading asphalt concrete depends on the particular paving operation to be performed: mainline, widening, berm, intersections, and whether the pavement course to be placed is base, intermediate, or surface. Spreading equipment requirements are stated in 401.12.
The Contractor should use means and methods approved by the asphalt spreader manufacturer consisting of, but not limited to, any combination of chain curtains, deflector plates, or other such devices that will eliminate segregation.
Certain pavers require modifications. C&MS Item 401.12 lists the pavers that require modification. The Contractor must submit a certification statement to the Engineer which states that the paver to be used is modified and approved as per 401.12.
Pavers that leave ridges, indentations, or other marks in the surface shall not be used. The Engineer shall determine whether a paver is providing an acceptable asphalt mat that is ready for compaction. See C&MS 401.01 Paragraph 3.
A standard asphalt paver consists of a tractor with a receiving hopper, a conveying and distributing system, and a floating screed. The screed is essentially a rectangular trowel which floats on the surface of the asphalt mixture. The tractor pulls the screed by means of two shafts, or arms, hinged to each side of the tractor. The thickness of placed material is regulated by adjusting the angle of the screed with respect to the arms. This adjustment causes the screed to rise or fall until a condition of equilibrium is reached. Vibrating or tamping devices on the screed maintain a uniform flow of mixture under the screed. A heating system is provided to bring the screed to operating temperature at the beginning of work and to maintain proper screed temperature in cool weather.
The paver must have an automatic control system that maintains the screed in a constant position relative to grade, profile, and cross-slope references. These references must be capable of controlling the screed position independent of irregularities in the underlying surface and the paver operation.
It is the Contractor’s responsibility to make any necessary adjustments in the paver operation. The Inspector, however, should be familiar with the working of the paver, the effect of wear on paver operation, and the effect of various paver adjustments on the placing operation.
Where the use of a standard paver cannot be used due to irregular areas or size, special paver types can be approved by the Engineer. One type is the offset blade strike-off paver. This type of paver has a receiving hopper that feeds asphalt to a side-mounted strike-off blade. The tractor to which the hopper is attached operates on the surface adjacent to the area being paved. The blade is attached to the tractor and can be adjusted for width, elevation, and cross-slope. These pavers are used to place asphalt concrete for pavement widening, berm paving, pavement repairs, and other applications where a relatively narrow width is to be placed.
Compaction of asphalt concrete is governed by 401.16, 446.05, or 448.03 depending on the contract item designation. Item 446 is accepted by density testing and the roller selection is at the discretion of the Contractor, not governed by 401.13. This is also the case for 448, when it is accepted by field density testing using Supplement 1055. Acceptance by density testing allows the Contractor to select the type and number of rollers needed to obtain proper compaction, and thus, receive full compensation. When compliance with 401.13 is not required, rollers must be inspected for general working condition, leaks, and suitability. The Department retains the right to reject the use of rollers which are not in good repair or are not designed to do the required work fully and satisfactorily.
Steel drums and rubber tires used for compaction should have the necessary accessories to prevent adhesion to the mixture. They should be kept moistened with water, water containing a detergent, or water containing an approved release agent. Excessive use of liquid should be prohibited.
Pneumatic tire rollers must be self-propelled, reversible units with vertical oscillation on all wheels, on at least one axle. The Contractor should determine the tire inflation pressure necessary to meet the specified minimum contact area and contact pressure requirements. The Contractor should furnish the tire manufacturer’s charts or tabulations to the Engineer for verification of the required inflation pressure. Tire inflation pressure should be maintained within 5 pounds per square inch (35 kPa) of the required pressure.
The surface on which an asphalt concrete course is to be placed must be free from material accumulations that would contaminate the mixture, prevent bonding, or interfere with placing operations. The surface of the existing pavement should be inspected before the paving operation begins, and should be cleaned of all foreign material, particularly dust, in accordance with 401.14. The surface should be checked a short distance in front of the paver to ensure that the surface has not become contaminated during the construction operation. A dirty or very dusty surface reduces the ability of the tack coat to bond, resulting in a potential slippage plane between the existing surface and the asphalt overlay.
Prior to placing asphalt concrete on a pavement course constructed under the same contract, the condition of this previously approved work should be inspected. Where the approved subgrade or pavement course has become loosened, rutted, or otherwise defective, the deficiency must be corrected before the placing of a subsequent course is permitted. Hauling of materials over an asphalt concrete base course, for example, may cause cracking when there is not sufficient pavement thickness to carry heavy loads or where excessive deflection occurs over soft areas developed in the subgrade. Where cracking of the pavement occurs in such a case, the strength due to slab action is destroyed, and the affected material must be removed and replaced after correcting the cause of the failure.
A tack coat is applied to an existing surface and to a new asphalt surface in preparation for the next course. Tack materials are asphalt emulsions conforming to C&MS Item 702. The following types are allowed 702.04 RS-1, SS-1, SS-1H, CRS-1, CSS-1 or CSS-1H, or 702.13.
The plans will indicate where tack is to be placed. In the case where the plans do not specify tack between an intermediate and surface course, this specification makes that application a requirement.
The specification requires all vertical faces that will be in contact with an asphalt course to be coated with asphalt material of a type specified in 401.03 in order to improve the bond to the new asphalt concrete course. This includes gutters, curbs, catch basin castings, etc., and the vertical face of an existing pavement. Due to the small quantity of material involved, approval of the asphalt material for this purpose may be based on field inspection. The results of this inspection are recorded on the Inspector’s Daily Report, with the material identified as to type, grade, manufacturer, and quantity used.
In some resurfacing contracts, a quantity of asphalt concrete may be specified in the plans for making spot corrections, or for placing a continuous intermediate course to correct the cross-slope and profile of the existing pavement, as directed by the Engineer. This operation should be controlled closely to ensure that the best possible riding quality is obtained in the completed pavement.
Spot corrections, when provided for in the plans, are made to correct irregularities such as cross-slope or profile problems. Spot corrections can include a leveling or “scratch” course. These corrections are made prior to placing the intermediate or surface course. Unless specifically detailed on the plans, the Engineer will locate deficiencies in the existing surface requiring spot correction and notify the Contractor of the required corrective measures. Interior edges of spot patching may be irregular, but outside edges must conform to the specified edge alignment. All spot corrective work must be completed to the satisfaction of the Engineer before the intermediate or surface course is placed.
Intermediate course of asphalt concrete can be specified to correct minor irregularities in the existing pavement surface. Spot correction may be needed prior to placing the intermediate course. The intermediate course should not be used to correct major deficiencies. Inspect the placing of the intermediate course to assure that all deficiencies have been corrected satisfactorily. For intermediate courses where the profile or cross-slope is not specified on the plans, the profile of the new course should provide for a smooth riding surface, and the cross-slope should be uniform on all tangent sections and should vary uniformly in transition sections into superelevated sections. For an intermediate course where the profile or cross-slope is specified, the new course should conform to the required profile and cross-slope, within the specified limits. The procedure for checking the profile and cross-slope is given in Section 401.19.
During asphalt paving, careful observation of the mat behind the paver and the rollers is required to ensure a quality and durable finished pavement. The Contractor’s FQCS is responsible for the entire paving operation from surface preparation to paving. The Contractor is required to control and take prompt corrective action when the mat being placed is not free of any defect within that Contractor’s control. Any deficiency in the mat should be brought to the attention of the FQCS. Record the deficiency and the action taken by the FQCS. If the FQCS does not make changes to remedy the defects, notify the Engineer. An FQCS can have his approval removed for failure to perform his duties. The following examples are defects or problems during pavement preparation or paving that should be observed and corrected.
Tack coats are used to bond asphalt layers together to create a monolithic pavement structure. All of the pavement layers need to act as one in order to effectively resist the shear and tensile stresses induced by traffic. The tack coat keeps the pavement layers from sliding over one another and prevents layer delamination. If the tack coat is insufficient, the pavement life will be reduced. The proper application of tack coat is often overlooked in the field.
Tack must be applied in a fine, even spray that covers the entire pavement. Tack application that appears “stringy,” spider-webbed,” streaked, or ridged is unacceptable and should not be included for pay. Refer to Item 407 in the MOP.
Pavements to be tacked must be properly cleaned using power brooming or street sweeping. Where surfaces have been milled, residual dust is a major problem, thus, creating a bond breaker between the existing asphalt and the tack coat. This leads to excessive truck tire pick-up. Additionally, the tack coat must be given time to “cure” so tire pick-up is minimized.
Segregation can be caused by asphalt plant processes, improper truck loading, hand placing and raking, and paver operation. Segregated areas are susceptible to raveling over time and rapid pavement deterioration. Only a dense, uniform surface texture is acceptable.
When an asphalt mat is segregated, the coated coarse and fine aggregate particles physically separate from each other. Segregation can appear in a cyclical pattern or randomly across the mat. The aggregate in the mat should appear to be uniformly graded in size from coarse to fine, behind the paver, in the finished mat.
End-of-load segregation occurs as cyclical V-shaped or chevron type patches in the mat. This type of segregation is a result of improper truck loading operation at the plant that results in the large aggregate separating from the fine aggregate in the truck bed. This generally can be controlled by changing loading operations at the plant.
Segregation must be controlled by the Contractor. The FQCS is responsible for making changes to eliminate segregation in the mat. If the FQCS does not make changes to remedy the defects, notify the Engineer. An FQCS can have his approval removed for failure to perform his duties.
The asphalt mixture should have sufficient cohesion to remain mounded in the vehicle during hauling, but should flow freely from the vehicle when the load is dumped. Bumping or stopping the paver between loads, as well as uneven flow of material into the paver hopper, will likely leave bumps in the finished mat. Trucks backing up to the paver hopper should never bump the paver; the paver should move to the truck and make contact with the rear tires. During paving, asphalt should flow uniformly from the truck into the hopper with the quantity in the hopper being maintained at a constant level. Sudden surges cause surface irregularities.
The mat should have a uniform appearance across the width placed. Streaks of differing texture and pulling or tearing of the mixture generally indicate the need for adjustments to the paver screed and extensions. Worn screed plates can also cause streaking behind the paver. Other causes can include low mix temperatures and mix problems. In all cases, the FQCS is required to make changes to correct deficiencies. If the FQCS does not make changes to remedy the defects, notify the Engineer. An FQCS can have his approval removed for failure to perform his duties.
The mixture should have sufficient stability under the rollers without excessive displacement and movement. A bow wave in front of a roller drum is indication that the material is not stable. Resultant small, transverse cracks after rolling are also indication that the material is tender. Roller marks may also be an indication of an unstable mix.
Asphalt binder is used to bind the aggregate particles together. The mixture should contain enough PG (asphalt) binder without producing a glazed or flushed appearance under the action of roller compaction. A flushed asphalt pavement may contain too much asphalt binder.
Another cause of a flushed or glazed surface can be a result of opening to traffic too soon, particularly on hot summer days. The action of traffic tires on the hot surface can draw the liquid asphalt binder to the surface causing a shiny, glazed appearance. Traffic should not be permitted on a completed surface course until the mixture has cooled sufficiently.
All asphalt paving compaction must be completed before the mixture cools below a workable temperature, generally 175 °F to 225 °F. During inspection, the temperature of the asphalt delivered to the paver, and immediately behind the paver, must be close to the optimal compaction temperature as listed on the approved JMF. In the case of foamed Warm Mix Asphalt this may be, in general, 0 to 30 °F less than the JMF compaction temperature. The breakdown roller (first roller) must compact the mat at, or near, this temperature. Complete coverage of the breakdown roller across the mat is required to obtain uniform density. Lower compaction temperatures are directly related to an increase in air void content, which increase the permeability of the pavement. A high permeability pavement will fail prematurely unless specifically designed to be permeable. Even with a perfect mix design, if the mix is not properly compacted in the field, the final product will not last for its intended length of time.
Asphalt delivery trucks are not allowed to clean out truck beds on the pavement that will be paved. The material that remains in truck beds is cold and will not compact correctly, often causing a bump in the pavement, and likely, a future pot hole. Spreading or broadcasting the cold material across the pavement prior to paving does not solve the problem. Always have the Contractor designate a cleanout area and ensure truck drivers are using it. If truck drivers continue to clean out on the road to be paved, have the FQCS address the issue.
Truck drivers use release agents to keep asphalt from sticking to truck beds. Diesel fuel is prohibited to be used as a release agent in truck beds, but its use still occurs on ODOT projects. ODOT allows the use of special asphalt release agents and maintains a list of approved products on its website. Diesel fuel dissolves the asphalt binder and causes a soft spot in the asphalt mat, which eventually becomes a pot hole. Any truck driver using diesel fuel must be removed from the project. Contact the testing office for assistance if needed. The FQCS is required to take action to prevent diesel fuel used as a release agent. Pavement areas affected by diesel fuel should be corrected by removing the contaminated material and replacing it with acceptable material. Note: the overuse of approved release agents can damage new pavement. Observe truck loading at the asphalt plant to ensure there is no free liquid draining from truck beds as a result of over application of any approved release agent.
Variations in the moisture content of the aggregate fed to the plant, or an erratic production rate, may result in an excess of moisture in the asphalt concrete mixture. This can cause slumped or flattened loads accompanied by considerable bubbling or steaming of the mixture. In extreme cases, the PG binder material may separate from the aggregate and collect in a film over the surface of the load. This condition is unacceptable and is sufficient cause for rejection of the load. Excess moisture may cause streaks of excess PG binder material to appear as the mixture is spread. Report moisture problems to the Plant Monitor and the FQCS.
An asphalt concrete mixture can become unsatisfactory due to contamination of the PG binder material, the aggregate, or the mixture itself. Contamination of the PG binder material, either in shipment or in storage at the plant, has the most serious effects. Contamination of the PG binder material may remain undetected until a quantity of mix is produced, at which time a marked change in the odor, consistency, or appearance of the mixture in the truck or in the paver hopper indicates that contamination has occurred. When these changes are noted, observe the mixture carefully as it is being placed and compacted. Report changes in the mixture to the FQCS and ensure there is follow-up.
When nighttime paving is required, no work can proceed without an approved and operating lighting system. This work consists of furnishing, installing, operating, maintaining, moving, and removing nighttime lighting to illuminate construction work areas for night work. Night work is defined as work performed from 30 minutes before sunset to 30 minutes after sunrise.
An illuminated zone of at least 5-foot-candles is required in the immediate vicinity of all paving equipment and at least 1-foot-candle at 25 feet. Item 401.15 provides these specific requirements. The Engineer must approve the lighting system based on measured luminance readings. The Contractor must provide a photometer that can measure the luminance levels at the specified foot-candles with measurements taken 20 inches above the roadway.
Luminance measurements can be required by the Contractor at any time as requested by the Engineer. The Contractor must provide luminance readings at any change in the approved lighting configuration. Any corrections and deficiencies must be made within 1 hour or the Engineer is required to shut down the construction.
Light sources shall be positioned so they do not interfere with, impede, or cause glare for motorists. Light cannot be pointed at adjacent properties. Luminaires must be kept clean and bulbs replaced immediately. Asphalt pavement placed during nighttime operations should be reviewed and inspected in the daylight for mat problems like segregation, smoothness, etc. The results and observations of daylight reviews should be used to make corrections and adjustments to the paving procedures in order to correct and prevent substandard operations and unacceptable asphalt pavement.
Many jobs require paving during night hours to avoid lane restrictions during peak traffic hours. The Department maintains a website that details those roadways that cannot have lane closures during daylight hours. It can be difficult to see mat deficiencies (e.g., segregation) during night paving due to limited lighting and shadowing. Undetected segregation has been known to be a problem; therefore, the Department requires the use of an MTV/MTD with paver hopper insert or remixing paver for night paving under the following conditions:
An MTV, MTD, or remixing paver must be a machine specifically made to eliminate segregation of asphalt mats. There are MTVs and MTDs that merely transfer material from the truck to the paver and do not mechanically remix the material prior to discharge to the paver hopper. These machines are not allowed. The Contractor must provide manufacturer’s information to prove that the MTV/MTD proposed for use on the project has a mixer/agitator mechanism that consists of either segmented, anti-segregation, re-mixing augers, or two full-length longitudinal paddle mixers specifically designed for the purpose of re-mixing. Longitudinal paddle mixers shall be located in the paver hopper insert.
Before the start of paving, the Contractor shall provide a method for measuring the mat temperature differentials, and a method of inspection for segregation, that will be used during paving operations. Measuring mat temperatures can be performed using an infrared thermometer or special equipment specifically designed for this purpose, such as the Pave IR system. There should be a regular daylight inspection of the mat placed the previous night to ensure there are no areas of segregation that could not be seen during night paving operations.
Equipment that that does not consistently eliminate physical segregation and/or does not meet the temperature differential requirement should not be used on the project. Notify the FQCS of deficiencies of the equipment and ensure a remedy is put in place.
Specification Item 401.15 requires the Contractor to, “Remove and replace, or otherwise correct, any portion of the pavement course found to be defective in surface texture or composition before or after compaction in a manner satisfactory to the Engineer.” The Engineer will make a determination about whether a defective pavement must be removed or can remain in place with some repairs. The following methods may produce satisfactory results when the work is properly performed by sufficiently skilled workers. All corrective methods must be approved by the Engineer.
Where removal of material is required or to correct a low area, saw the patch area to neat lines. Remove the asphalt to the full-depth of the defective course and coat the surface of the of the patch area and butt joints with approved tack coat material. Place the new mixture in the prepared patch area to the proper elevations and compact as required.
When material must be removed to correct high areas in the surface, use a diamond grinder. Removal and replacement of the surface course and a portion of the underlying material may be necessary in extreme cases.
Minor segregated areas in which there is insufficient fine aggregate at the surface can be corrected by a squeegee application of an asphalt binder, of the same type, used in the mixture. An emulsion of the asphalt material, along with added fine aggregate, is also effective. Careful use of the squeegee is necessary to fill the surface voids without leaving a surplus of the sealer on the surface.
The compaction of asphalt concrete mixes is currently governed by one of two types of specifications. A method specification is used for some asphalt concrete (301, 302, and 448 by 2005 specification and older), while most mix types (446 and 448 by 2008 specification and newer) are governed by a density requirement (446.05 and 448.03). Supplement 1055 details the requirements of density testing for 448 mixtures.
The Job Mix Formula (JMF) provides the optimal compaction temperature for the design. The mixture should be checked frequently to ensure the asphalt is being compacted at or near that temperature. For foamed Warm Mix Asphalt this the filed compaction temperature may be 0 to 30 °F less than that listed on the JMF. For asphalt concrete base pavements, refer to Items 301 and 302 for minimum allowed mix temperature. In all cases, the mixture should not be allowed to cool below a workable temperature for adequate compaction (175 °F to 275 °F) and the majority of compaction should be accomplished before the temperature reaches 225 °F.
This section applies to all mixes without a density specification. Compaction of an asphalt concrete mixture using the method specification is performed by using the rollers and methods specified in 401.13 and 401.16.
The number and type of rollers proposed for use by the Contractor should be checked for compliance with 401.13. The calculation for the roller capacity (tons per hour) should be made by the project personnel. Documentation of the calculations and the tire manufacturer’s charts or tabulations furnished by the Contractor should be kept in the project files. As the work progresses, the placement rate should be checked to ensure that it does not exceed the combined capacity of the rollers in use. If the placement rate does exceed the roller capacity, the Contractor must either reduce the rate or use additional rollers.
For compacting base mixtures, the specifications require at least one steel wheel and one Type 1 pneumatic tire roller. This requirement must be met even though the placing rate may indicate the need for only one roller. The intent is to ensure that each layer of base mixture will be subjected to the traffic conditioning effects of pneumatic tire rolling while the mixture has sufficient retained heat to respond without fracturing.
A contractor is using one 3-wheel roller, one vibratory roller with 66-inch drums (both vibrating), and one Type 2 pneumatic tire roller to compact a 3-inch thick mat using material with a Laboratory conversion factor of 2.0 tons per cubic yard (tons/yd3).
Item 446 mixtures require the Contractor to meet a specified density target. To determine the density, ten 4-inch cores are cut from the pavement for each day of paving. The District Test Lab determines the field density from the cores. The Contractor can receive a bonus or deduction to the pay item based on the field densities. Refer to Item 446 for detailed information on this process.
Supplement 1055 provides the procedure for density testing using a nuclear gauge for 448 mixtures. This process requires the cutting of cores only to establish the correlation between core density and gauge density. Refer to Item 448 and S1055 for details on determining density of 448 asphalt concrete.
This section pertains to the compaction of asphalt concrete mixes using either the method specification or the density acceptance specification (described above). The Inspector should refer to the last four paragraphs of 401.16 to review the common part of both compaction specifications.
The optimum compaction conditions are present immediately behind the paver, and the greatest increase in density per roller pass occurs in this area. It is important that the breakdown roller follows the paver as closely as possible and obtains full-coverage across the entire mat width being placed. In general, roller coverage should begin at the edge and move toward the centerline, moving longitudinally, and overlapping each roller pass by one-half of the prior pass. When a longitudinal joint is being made (i.e., matching a previous course), this joint should be rolled first and then preceded with the normal rolling pattern. The specified roller pattern should be repeated uniformly, without abrupt stops or changes in direction, and the reversing points at the end of the roller runs should be staggered to reduce the possibility of forming transverse bumps. Final rolling should remove all tire marks.
Asphalt pavement joints can be confined or unconfined. Confined joints occur when the asphalt mixture is placed directly against a previously placed asphalt pavement or an existing pavement. Unconfined joints are considered loose since they are not placed against any confining edge or structure. Unconfined edges of the mat should be rolled using a steel drum roller with the roller drum hanging out over the edge approximately 6 inches.
Longitudinal joints occur where two lanes are, or will be, joined together. For an unconfined or confined longitudinal joint, best results are obtained by using a drum vibratory roller operated in the vibratory mode with the frequency set at maximum. Pneumatic tire rollers should not be used to do the first pass of an unconfined longitudinal joint.
Longitudinal joints in the surface layer shall correspond with the edges of proposed traffic lanes. Longitudinal joints in lower layers shall be offset, as per Standard Construction Drawing BP-3.1, alternating each side of the edges of traffic lanes no less than 6 inches (150 mm).
Proper longitudinal joint construction requires the loose asphalt mixture to be placed at an extra 25 percent thickness above the confined joint material to allow for roll down and with a 1-inch to 1-1/2-inch overlap to permit proper compaction. If the joint is being made against a sawed or milled vertical edge, the overlap can be around 1/2 inch.
The height of the new asphalt mixture over the joint must be sufficient to permit full compaction of the material being placed before the weight of the roller begins to be carried on the adjacent construction. This pre-compaction height must be maintained uniformly, particularly on surface courses where raveling of an unsound joint is likely to occur. Height uniformity is achieved by continuous, automatic control of the strike off height.
The paver should be operated in a straight line to provide a mat with a straight edge that can be consistently overlapped. Excessive deviations of the edge line from a straight line are unacceptable and require trimming the edge before the adjacent material is placed. With a good edge and proper control of the placing operation, little or no hand work is needed to form a good longitudinal joint. The Contractor should not continuously rake the joint. On surface courses, the Inspector must be sure that when hand raking does occur, it does not produce an irregular surface texture.
On projects where traffic is maintained, the longitudinal joints between adjacent lanes of surface course pavement must be completed within 24 hours. Where this time limit is exceeded, the joint should be inspected, and if the joint appears to be excessively rounded or displaced, trim the face to vertical according to 401.17.
All cold longitudinal joints are required to be sealed, as specified in 401.17, using a certified PG binder or SBR Asphalt Emulsion to provide 100 percent coverage of the joint. Ensure the correct material is being used. Often tack is used instead of the required material; this is not acceptable.
Transverse joints occur at any time the paving operation is stopped for the day (or night). When placing the last load of asphalt for the day, the paver should move forward until all material is spread. This leaves an irregular end that should be squared off by hand to form the joint. This joint edge should be compacted thoroughly, with the rollers passing over the edge, even though this may cause some rounding or even displacement of the material in the process.
When the paving operation resumes, locate the point where the rounding or other departure from the profile begins, and continue the paving operation from that location in order to assure a smooth transition from one section to the other. In some cases, trimming the joint face may be necessary. For all surface courses, the transverse construction joint is required to be formed or cut to vertical. All cold, transverse, longitudinal joints are required to be sealed as specified in 401.17 using a certified PG binder, SBR Asphalt Emulsion to provide 100 percent coverage of the joint, or with a certified 702.04 asphalt material at a rate of 0.25 gallon per square yard (1 L/m2).
The Contractor must have workers and hot material available during construction of the transverse joint. Utilize alternate rolling, a 10-foot straightedge, and the addition or removal of material to produce a uniform profile. Paving operations should not be permitted to continue until a satisfactory joint has been obtained.
The specifications require the Contractor to maintain the rate of spreading of a uniform asphalt course to within ± 5 percent of what is required by the plan. For a given uniform course, the Required Placement Rate per Station (RPRS) is calculated in tons per station and checked against the Actual Placement Rate (APR). Determine the APR using the plant weight tickets, which accompany each load of material, and the area covered by a given number of loads. The area to be used for the check should not be greater than 500 feet (150 m) in length and should be measured from the start of a full load of asphalt concrete to the end of a full load. The results of these checks should be recorded on Form CA-FP-4, Bituminous Concrete Inspection.
To establish the RPRS, the laboratory conversion factor (tons/yd3) is multiplied by the required volume of the asphalt pavement per station. One station is equal to 100 feet. The placement rate, in tons per station, is given by the following equations:
A contractor is placing a 5-inch uniform mat of asphalt concrete pavement 12 feet wide, with a Laboratory conversion factor of 2.0 tons/cubic yard (tons/yd3). In 500 feet the Contractor used 188 tons of material (from the truck weight tickets). Is the APR within ± 5 percent of the RPRS?
When variations greater than ± 5 percent of the required rate are calculated, the Inspector should address the variance with the FQCS to determine a cause. The Contractor should adjust the paver operation accordingly to bring an unwarranted variation back into tolerance. The Inspector should immediately check the actual spreading rate when changes are made to the paving operation. All variations in tolerance should be recorded in the Inspector’s daily report.
Depending on the nature of the material being placed, and quality of the placing operation, one to four placement rate checks per day normally will represent the material placed with a given paver. When the work involves a series of small areas, the use of partial loads at each location makes the check impractical. In such cases, the Inspector should determine plan thickness is being obtained.
The placing of asphalt concrete should be closely controlled and kept as near as possible at the specified rate. Even for a well-controlled operation, both positive and negative variations will occur. The Contractor should not place the material at a rate greater than required since this would result in an overrun of plan quantity for which the Contractor would not be paid. As stated in 401.21, “Method of Measurement,” the pay quantity is limited to the total weight of the item placed, converted to cubic yards (cubic meters), with no payment made for the quantity of material placed which exceeds that calculated from plan lines and dimensions.
For all new construction, and some rehabilitation construction, the required profile grade and pavement elevations are given in the plans. Where a profile grade is not specified for rehabilitation construction, the profile of the finished pavement surface depends upon the profile of the existing pavement surface. The plans may require profile correction prior to placing an overlay pavement; however, profile elevations may or may not be specified.
For construction where a profile grade is specified, the Contractor is required to set grade stakes in order to provide a reference for controlling the elevation at which the asphalt concrete is placed. These grade stakes should be set at intervals of no more than 50 feet (15 m) on tangents and no more than 25 feet (7.5 m) on vertical curves and transition lengths of superelevated curves. The stakes should be placed on both sides of the pavement to permit easy checking of the grade; intermediate stakes should be provided in areas of greater than normal width.
The specifications require the completed pavement longitudinal profile does not deviate more than 1/2 inch from the plan elevation at any point. The difference in pavement elevation may be obtained by methods such as profile levels or differences in rod readings. Prior to placing the surface course, the Contractor must check the profile of the preceding course at 50-foot intervals and submit a tabulation of the results to the Engineer for approval. The results should be tabulated in a convenient form, which list the following:
The Engineer will evaluate the Contractor’s profile check. Approval of the profile and permission to place the surface course should be based on satisfactory completion of any corrective work needed for compliance with the profile requirement. The approved profile check will be part of the project record.
For all new construction, and some rehabilitation construction, the required cross- or transverse slope of the asphalt concrete pavement is given either as crown or as superelevation in the plans. Where a cross-slope is not specified for rehabilitation construction, the cross-slope of the finished pavement depends on the cross-slope of the existing pavement surface.
For construction where the cross-slope is specified, the pavement cannot vary more than 3/8 inch in 10 feet from the required slope. The Contractor should check the cross-slope of the pavement course being placed during the spreading operation with a 10-foot straightedge. The Inspector should observe this operation regularly to ensure that the pavement course is being constructed substantially within the specified cross-slope limits.
Particular attention should be given to the checking of the cross-slope on the asphalt concrete course preceding the surface course. Where observation of the Contractor’s checking or additional checking by the Inspector reveals substantial deviations from the specified limits, corrections must be made to bring the asphalt concrete course within the specified cross-slope limits before the surface course can be placed.
The plan specified the cross-slope as 0.016 foot per foot of pavement width (0.016 ft./ft.). For a 12-foot wide lane, the pavement drops from the crown to the edge based on the rate of slope. This vertical drop (in inches) is calculated:
The required smoothness of asphalt intermediate and surface course cannot exceed 1/4 inch from the testing edge of a 10-foot (3.0 m) straightedge. The Contractor is required to provide a straightedge that is satisfactory to the Engineer. The Contractor should check the course being placed while the Inspector observes. The frequency of checking depends on the nature of the work being done. The surface smoothness should be checked closely when a transverse joint is being made, when erratic paver operation occurs, or when hand placing is required in the construction of a transverse joint. This check is often done at the end of a paving project since many Contractors elect to use a non-contact profiler and software per ODOT Supplement 1058.
The project Inspector should determine at the beginning of the project which method the Contractor will use to check smoothness when PN 402 or PN 470 do not apply. In the case neither of these proposal notes apply, ensure that the Contractor is regularly checking the surface behind the paver with the 10-foot straightedge.
Asphalt mixture is delivered to the project based on weight in tons for each load. Payment is made in cubic yards for the specific item of work (e.g., 301, 448, or 446). A conversion from tons to cubic yards is required. The Laboratory provides a conversion factor (unit weight/volume) for the specific JMF being used in tons/cubic yard (tons/yd3).
The number of tons placed and accepted is converted to cubic yards and compared to the quantity calculated from the plan lines and dimensions. The Department will not pay for additional quantities over the plan calculated cubic yards.
After the total tonnage of material used in a pavement section has been determined, convert it to cubic yards (cubic meters) using the applicable conversion factor established in 401.21. The conversion factor of a mix is included on the JMF and can be obtained from the District test lab. The tonnage of material used in a pavement section is converted to cubic yards (cubic meters) as follows:
Keep a daily summary that includes Reference Number (Pay Item), Item Number, paving location, tons used (along with the conversion to cubic yards), and the calculated pay quantity. Add the asphalt plant tickets and keep with the daily summary. Use an adding machine with a paper printout. On the printout write the project number, date, Reference and Item Number, Participation Code, paving location (route, station to station, lane, etc.), and show the conversion to cubic yards. Initial the printout and keep with the daily summary sheet.
Complete a final summary of the total quantity placed for each Reference Number. The final summary should provide details for all separate pavement areas. In general, separate pavement areas include different contract parts, different participation codes, physically separate roadways, and pavement areas having differing design sections (e.g., ramps).
The pay quantity of asphalt concrete with a uniform plan depth is calculated using the plan width and measured distance along the centerline. Paving in excess of the plan width or plan length is not eligible for pay. Excess quantity can only be paid if approved by the Engineer.
Where one to two courses of asphalt concrete is placed on an existing pavement for the correction of the profile and cross-section, the depth is variable and the pay quantity is the quantity placed as directed by the Engineer in accordance with the intent of the plans. Placement rate checks, as described in Section 401.21, should be used to verify that the Contractor is meeting the intent of the plans.
This section contains general requirements for inspecting and documenting asphalt concrete pavement operations. The Inspector should record all observations regarding the placement of the asphalt mixture, in addition to the following requirements.
7. Document lift thickness, mat width, weather conditions, surface tolerance checks, equipment problems, mat problems (segregation, tearing, tenderness, etc.), spreading rate, roller coverage, and any other issues or observations made during paving operations.