Category:403 Asphaltic Concrete Pavement
| Forms |
| QA/QC Checklist |
403.1 Design
403.1.1 Superpave Mixtures
For full depth flexible pavements, the Superpave cross sections should consist of a 1-3/4 in. (45 mm) SP125 surface course over a SP250 course as needed for the total thickness. For overlays, the Superpave cross section should consist of 1-3/4 in. (45 mm) SP125 surface course over a SP190 course as needed for the total thickness.
The Superpave mixture names have a technical background and specific meaning. The "SP" designates a Superpave mixture; the "125", "190" and "250" represent the nominal aggregate size contained in the mixture. The maximum aggregate size is 12.5 mm (1/2 in.) for "125", 19.0 mm (3/4 in.) for "190" and 25.0 mm (1 in.) for "250". The "B", "C" or "E" indicates a Superpave mixture design in the Superpave specifications; the "LP" indicates if the mixture contains limestone/porphyry or limestone/steel slag, and the “SM” indicates a stone matrix asphalt mix.
403.1.2 Superpave Selection Criteria
The Superpave Selection Criteria Table provides the Superpave mixtures to be specified for the different applications discussed above.
| Location of Misture | Type of Corridor | ||
|---|---|---|---|
| Heavy Duty | Medium Duty | Light Duty | |
| Surface | SP125B, SP125BLP or SP125BSM | SP125C, SP125CLP or SP125BSM | SP125C or SP125CLP |
| Underlying Course for Overlays | SP190 B or SP250B* | SP190C or SP250C* | SP190C or SP250C* |
| First Underlying Lift for Full Depth Pavements | SP250B | SP250C | SP250C |
| Remaining Underlying Lifts for Full Depth Pavements | SP250C | SP250C | SP250E |
| *An SP250 mixture may be substituted for a SP190 mixture to prevent drop-off and a trough section caused by coldmilling operations. | |||
403.1.3 Special Superpave Mixtures
Special 403 surfacing mixtures, e.g. Superpave limestone-porphyry (SP125xLP), should be substituted for the SP125 mixture when a mixture with higher friction properties is needed, such as in high speed urban congested areas or where the project accident rate exceeds the statewide accident rate for the last 5-year period and the wet to dry accident ratio is 1:3 or greater.
Superpave Stone Matrix Asphalt (SP125xSM) should be used as the surface mixture on all interstates, including ramps, and all medium and heavy duty routes shown within the “COMMERCIAL ZONE LIMITS FOR ALL ROUTES OTHER THAN INTERSTATE” on the MISSOURI VEHICLE ROUTE MAP. The designer should show SP125xSM on the plans.
403.1.4 Leveling Course
Milling is the preferred method of leveling, however PMBP or SP125 asphaltic concrete may be used for spot wedging and for leveling course as per the standard specifications, providing the minimum thickness is 1 in. (25 mm). The grade of asphalt binder to be specified in the contract should be the same as that for the surface mixture.
403.2 Construction Inspection
403.2.1 Description (Sec 403.1)
There will be no commentary for sections in which the intent of the specifications, as written, is clear.
Design Levels (Sec 403.1.2)
At the contractor’s expense, a mix with the same size aggregate and one design level higher can be substituted for the mix required by the contract. Substitutions typically require a change order to pay for the higher quality mix at the price of the lower mix. Care should be taken to assure that the material product codes reflect the mix actually placed on the roadway. The substitutions must be done uniformly and various design levels in the same lift will not be allowed.
403.2.2 Material (Sec 403.2)
See also Aggregate for Asphaltic Concrete, Bituminous Material and Asphalt Release Agents, Fiber Additives and Liquid Anti-Strip Additives for Materials information.
Fine Aggregate Angularity (FAA) (Sec 403.2.1)
Fine Aggregate Angularity (FAA) ensures a high degree of fine aggregate internal friction and rutting resistance. FAA provides an indication of the particle shape and is defined as the percent voids in loose, uncompacted fine aggregates. More fractured faces results in a higher void content in the aggregate. FAA is determined on the fine portion of the blended aggregate (passing the #8 sieve) in accordance with AASHTO T304 (Level 2 Aggregate Training). The minimum requirements, based on the design level of the mix, are given in Standard Specification Section 403.2.1.
Coarse Aggregate Angularity (CAA) (Sec 403.2.2)
Coarse Aggregate Angularity (CAA) ensures a high degree of coarse aggregate internal friction and rutting resistance. CAA is defined as the percent of coarse aggregates with one or more fractured faces. CAA is determined on the coarse portion of the blended aggregate (retained on the #4 sieve) in accordance with ASTM D5821 (Level 2 Aggregate Training). The minimum requirements, based on the design level of the mix, are given in Standard Specification Section 403.2.2.
Clay Content (Sec 403.2.3)
Clay content, or sand equivalency, is the percentage of clay-like material present in the aggregate. The higher the sand equivalent value, the less clay-like material present in the aggregate. Clay-like material can coat the aggregate surfaces and prevent the binder from adhering to the aggregate particles. Sand equivalency is determined on the fine portion of the blended aggregate (passing the #4 sieve) in accordance with AASHTO T176 (Level 2 Aggregate Training). The minimum requirements, based on the design level of the mix, are given in Standard Specification Section 403.2.3.
Thin, Elongated Particles (Sec 403.2.4)
This property, also known as flat and elongated, is the percentage of coarse aggregates that have a maximum to minimum dimension ratio of 5:1 or greater. Flat and elongated particles are undesirable because they have a tendency to break more easily than other aggregate particles. When an aggregate particle breaks, it creates a face that is not coated with binder, increasing the potential of the mix to strip or ravel. Also, the gradation of the mix becomes finer, which may be detrimental to the mix properties. Finally, a mix that contains flat and elongated particles may be difficult to place and compact. The percentage of flat and elongated particles is determined on the coarse portion of the blended aggregate (retained on the #4 sieve) in accordance with ASTM D4791 (Level 2 Aggregate Training). The maximum allowable percentage of flat and elongated particles for all mixes other than SP125xSM is given in Standard Specification Section 403.2.4.
SP125xSM Requirements (Sec 403.2.5)
In a Stone Matrix Asphalt (SMA) mix, the coarse aggregate will consist of crushed limestone and either porphyry or steel slag. SMA mixes have flat and elongated requirements for ratios of 5:1 and 3:1. The maximum allowable percentages of flat and elongated particles based on these ratios are given in Standard Specification Section 403.2.5.
Filler Restriction (Sec 403.2.5.1)
See Mineral Filler, Hydrated Lime, and Baghouse Fines in Plant Inspection.
Fibers (403.2.5.2)
Cellulose or mineral fibers, in accordance with Standard Specification Section 1071.4, must be used as a stabilizer in SMA mixes. Because the aggregate gradation of an SMA mix is gap-graded, fibers are used to increase the surface area of the mix and hold the binder in the mix. The fibers do not absorb the binder. The manufacturer, brand name, and dosage rate will be shown on the JMF. Fibers are proportioned by weight in both batch and drum plants. If an SMA mix is produced in a batch plant, the fibers can be added to the aggregate in the weigh hopper or in the pugmill. This can be done manually or mechanically with a metering device. If the fibers are added in the weigh hopper, aggregate from at least one hot bin must be discharged into the hopper before the fibers are added. If the fibers are added in the pugmill, the fibers must be added after the aggregate and before the binder. In either case, the dry mixing time shall be a minimum of 20 seconds and the wet mixing time shall be a minimum of 35 seconds. The mixing times and/or temperatures should be adjusted if a uniform mix is not produced. If an SMA mix is produced in a drum plant, the fibers can be added to the drum in loose or pelletized form. The fibers shall be uniformly and continuously metered into the mix. The metering system must be interlocked with the blending system. Pelletized fibers are added to the drum through the RAP inlet. Record all fiber shipments in the corresponding APIW. The inspector should verify that the manufacturer and brand name are included on the Pre-Acceptance List (PAL) and that the dosagerate meets the minimum requirements of Standard Specification Section 403.2.5.2. Fibers will be sampled in accordance with the PAL requirements and shipped to the Central Laboratory for testing. More information on the PAL requirements can be found in Standard Specification Section 106.12 and Control of Material.
403.2.3 Composition of Mixtures (Sec 403.3)
Gradation (Sec 403.3.1)
The master range for the combined aggregate gradation of each mix type is given in Standard Specification Section 403.3.1. These master ranges apply to the final gradation of the aggregate, including filler materials, before the binder is added. During production, the combined aggregate gradation may be outside of the master range when the tolerances of Standard Specification Section 403.5.1 are applied.
Anti-Strip Agent (403.3.2)
See Liquid Anti-Strip Additives in Plant Inspection.
403.2.4 Job Mix Formula
The mix design procedure will be in accordance with Materials Inspection.
Approval (Sec 403.4.3)
No mix shall be produced or placed by the contractor or accepted for use by an inspector without an approved JMF. This includes mix transfers. The Materials Field Office (MFO) will give written approval. In some extreme cases, approval may be verbal with written approval to follow. Occasionally, a contractor may elect to place mix while the request is still pending. In this situation, the contractor is proceeding at his own risk and should be so advised by an order record.
Job Mix Formula Modifications (Sec 403.4.4)
A new JMF will be required if a material source is changed or if unsatisfactory results are obtained. Unsatisfactory results may include a mix that fails to meet specifications (binder content, volumetrics, and/or density) or if the visual appearance of the mix is unacceptable. If a new JMF is required, the procedures outlined in Standard Specification Section 403.11 should be followed.
403.2.5 Mixture Production Specification Limits (Sec 403.5)
Intentional deviations from the JMF will not be permitted. The plant shall be operated in such a manner that the mix is produced as shown on the JMF. The specification tolerances are developed in an attempt to keep the mix as consistent as possible and to allow for some variation during production. However, these tolerances are not production limits. For example, if the target binder content is 5.0%, the binder content of the mix can range from 4.7% to 5.3% when the tolerances are applied. The contractor will not be allowed to produce the mix at 4.7% to save money.
Both QC and QA will use the following procedures to determine volumetrics of the mix and compliance with Standard Specification Sections 403.5.3 through 403.5.5. These procedures are discussed in greater detail in the Levels 1 and 2 Bituminous Training.
A loose mix sample consisting of roughly 100 lbs. will be taken from the roadway behind the paver, in accordance with AASHTO T168, at the required frequency. The sample will be thoroughly mixed and quartered in accordance with AASHTO T 328, or with an approved splitting/quartering device. Two opposite quarters will be retained for testing during the dispute resolution process, if necessary. The remaining two quarters will be mixed together and quartered again.
The required weight of mix, as listed on the JMF, will be taken from one quarter and used to compact a specimen in accordance with AASHTO T312. The mix will be compacted to Ndes gyrations while the mix temperature is within the molding range listed on the JMF. Using the opposite quarter, follow the same procedure for the second specimen. The Gmb of each specimen will be determined and the average will be used to calculate the air voids Va and the voids in the mineral aggregate (VMA). By specification, a minimum of two compacted specimens must be used to calculate these properties.
A third quarter will be used to determine the Gmm of the mix in accordance with AASHTO T209. The minimum sample size for each type of mix can be found in the training manual. This property is used to calculate the Va and density. The volume of the sample, which is needed in the calculation, can be determined by either the weigh-in-air method or the weigh-in-water method. The weigh-in-air method consists of weighing the sample and container (with the lid) completely filled with water in air. The weigh-in-water method consists of weighing the sample and container (without the lid) completely submerged in water.
The remaining mix should be mixed together and quartered again. To determine the binder content using the nuclear gauge, enough mix should be taken from opposite quarters. The required weight of mix is listed on the JMF. A moisture content sample should be taken from the same quarters. To determine the binder content using the binder ignition oven, enough mix should be taken from one quarter. The minimum sample size for each type of mix can be found in the training manual. A moisture content sample should be taken from the same quarter. Sometimes the ignition oven may not shut itself off. The oven may be shut off manually as long as 3 consecutive readings show less than 0.01% loss. The sample should be examined to assure that a complete burn has been achieved. This will be considered a valid test.
In situations where a retained sample must be tested, the following procedure should be used to reheat the sample. Heat the sample in an oven until the mix is workable. Take the mix out of the sample container (box, bucket, etc.) and spread it in a large pan or several smaller pans. Using this procedure, the mix will reach the molding temperature much quicker than it would if it were left in a mass in the sample container. Also, less aging of the mix occurs since the mix is in the oven for a shorter period of time. Once the mix has reached an acceptable temperature, the sample must be quartered using the procedures discussed above. The entire suite of tests must be performed on a retained sample.
Gradation (Sec 403.5.1)
See Sieve Analysis in Plant Inspection. The gradation of the mix is not a pay factor item. However, it does have a significant influence on the volumetrics of the mix. Samples may be taken from the hot bins at a batch plant or from the combined cold feed at a drum plant. It is acceptable to determine gradation from the binder ignition sample according to AASHTO Standard Test Method T 308. Contractors should be allowed the option provided that the chosen method is spelled out in the Quality Control Plan. Gradations of extracted samples would be satisfactory as well. QC is required to sample the aggregate and perform a sieve analysis twice per lot. QA is required to independently sample the aggregate and perform a sieve analysis once per lot. These testing requirements are minimums and should be increased as necessary. Minor deviations outside the tolerances given in Standard Specification Sections 403.5.1.1 or 403.5.1.2, whichever is applicable, may be allowed if the test results indicate that the binder content, volumetrics, and density of the mix are satisfactory. If the test results are unsatisfactory, adjustments of the JMF, in accordance with Standard Specification Section 403.11, are necessary.
Stone Matrix Asphalt Tolerances (Sec 403.5.1.1)
The tolerances from the JMF for SMA mixes are given in Standard Specification Section 403.5.1.1.
Mixture Tolerance (Sec 403.5.1.2)
During production, the combined aggregate gradation must be within the following limits:
| Percent Passing by Weight | |||
|---|---|---|---|
| Sieve Size | SP250 | SP190 | SP125 |
| 1 ½ in. | 100 | -- | -- |
| 1 in. | 90-100 | 100 | -- |
| ¾ in. | 92 Max. | 90-100 | 100 |
| ½ in. | -- | 92 Max. | 90-100 |
| 3/8 in. | -- | -- | 92 Max. |
| #4 | -- | -- | -- |
| #8 | 17-47 | 21-51 | 26-60 |
| #16 | -- | -- | -- |
| #30 | -- | -- | -- |
| #50 | -- | -- | -- |
| #100 | -- | -- | -- |
| #200 | 1-7 | 2-8 | 2-10 |
Density (Sec 403.5.2)
See also Density in Plant Inspection Density Samples in 460.6 Paving Operations. One sample per sublot will be taken for QC testing. QA will randomly test one of the samples from each lot to verify that a favorable comparison is obtained. These testing requirements are minimums and should be increased as necessary. SMA mixes shall have a minimum density of 94.0% with no upper limit. All other mixes shall have a density of 94.0 ±2.0%.
Shoulder Density (Sec 403.5.2.1) and Integral Shoulder (Sec 403.5.2.2). If the shoulders and the traveled way are placed in the same pass (integrally), the cores will be taken on the traveled way. No cores will be taken on the shoulder. For example, if the paving width is 16’ with a 12’ travel lane and a 4’ shoulder, the shoulder will not be subject to density testing.
Asphalt Content (Sec 403.5.3)
QC is required to sample and test the mix for the binder content once per sublot and QA is required to independently sample and test the mix once per lot. These testing requirements are minimums and should be increased as necessary. During production, the binder content of the mix, as determined by sampling and testing, shall be within ±0.3% of the target listed on the JMF.
Voids in the Mineral Aggregate (VMA) (Sec 403.5.4)
QC is required to sample and test the mix for the VMA once per sublot and QA is required to independently sample and test the mix once per lot. These testing requirements are minimums and should be increased as necessary. The VMA of the mix shall be within –0.5% and +2.0% of the minimum required for the corresponding mix type (see Standard Specification Section 403.4.6.2).
The following table gives the ranges for each mix type:
| Mix Type | VMA Limits (percent) |
|---|---|
| SP250 | 11.5-14.0 |
| SP190 | 12.5-15.0 |
| SP125 | 13.5-16.0 |
| SP125xSM | 16.5-19.0 |
Air Voids (Va) (Sec 403.5.5)
QC is required to sample and test the mix for the air voids once per sublot and QA is required to independently sample and test the mix once per lot. These testing requirements are minimums and should be increased as necessary. The Va for all mixes shall be 4.0 ±1.0%.
Tensile Strength Ratio (TSR) (Sec 403.5.6)
The TSR is used to evaluate the impact that water saturation and freeze-thaw cycles have on the strength of an asphalt mix. It can also be used to predict the susceptibility of the mix to stripping.
During production, loose mix samples will be taken and quartered as described in Mixture Production Specification Limits. TSR samples do not need to be located by random numbers. However, they should be taken whenever it is convenient to production, such as during a big gap between QC volumetric tests. QC has the option of taking the loose mix samples from any point in the production process. The recommended locations are from the roadway behind the paver or from the plant. The QA sample(s) should be taken from the same point as the QC sample(s). If QC takes their sample from the plant, QA should take their sample from the plant also. This does not mean that QA should be taking their samples at the same time as QC. Two opposite quarters will be retained and the remaining two quarters will be mixed together and tested in accordance with AASHTO T283.
QC should obtain enough mix to retain a sample. QC will sample and test each mix at a minimum of once every 10,000 tons, or fraction thereof. QA will independently sample and test each mix at a minimum of once every 50,000 tons. The TSR sampling requirements are best described with an example. Suppose that 112,960 tons of SP190 are to be placed on a project. By specification, QC is required to take twelve samples and QA is required to take three samples. There are two possible scenarios for sampling this mix. QC may take eleven samples representing 10,000 tons each and a twelfth sample that represents the remaining 2,960 tons. Or QC may take ten samples that represent 10,000 tons each and two samples that represent the remaining 12,960 tons (6,480 tons each). Either scenario is acceptable. Likewise, QA may take two samples representing 50,000 tons each and a third sample that represents the remaining 12,960 tons. Or QA may take one sample that represents 50,000 tons nd two samples that represent the remaining 62,960 tons (31,480 tons each). The contract quantity ay be used to approximate sample l locations.
QA will send approximately 125 lbs. of loose mix (approximately 4 – 13” x 13” x 4.5” boxes) to the Central Laboratory for testing. Each box must be labeled with the SiteManager ID Mix Type VMA Limits (percent) number and the mix number. A SiteManager record must be created for each sample, which must include all required information, the mix number, lot, sublot, and the represented tonnage. The represented tonnage is explained in the example in the preceding paragraph.
Additional information that may be included in the SiteManager record is the Gmm from the sublot that the sample was taken in (QC or QA) and the specimen weight that QC has been using. The specimen weight may be different from that shown on the JMF because of bin percent changes, etc. This information is helpful because it results in less trial-and-error for the Central Laboratory.
In the laboratory, a minimum of six specimens are compacted to a height of approximately 95 mm. The air voids of the specimens are calculated. For all mixes other than SMA, the air voids must be within 7.0 ±0.5%. For SMA mixes, the air voids must be within 6.0 ±0.5%. Half of these specimens are saturated, frozen, and thawed. These are the conditioned specimens. The degree of saturation of the conditioned specimens is also calculated. The remaining specimens are unconditioned. Then, the indirect-tensile strength of all of the specimens is determined. Therefore, the TSR is the ratio of the average tensile strength of the conditioned specimens to the average tensile strength of the unconditioned specimens.
A favorable comparison will be obtained if the QC and QA test results are within 10% of each other. The contractor’s pay will be adjusted in accordance with Standard Specification Section 403.23.5 based on the QC test results. For example, if the QC TSR is 95% and the QA TSR is 93%, a favorable comparison has been obtained and the contractor will receive a 5% bonus. However, if the difference is between 5% and 10%, the Field Office should be consulted. The Field Office will evaluate the air voids and saturation levels. If the difference is greater than 10%, the dispute resolution process should be initiated. QC and QA retained samples should be kept for an extended period of time so that they may be used during dispute resolution if necessary.
Aggregate Properties (Sec 403.5.7)
The aggregate consensus tests (Fine and Coarse Aggregate Angularity, Clay Content, and Thin, Elongated Particles) are performed on the blended aggregate. Aggregate will be sampled from the combined cold feed at a drum-mix plant or the hot bins at a batch plant. If the aggregate is sampled at a batch plant, the hot bin samples must be blended together manually using the plant hot bin percentages.
For each mix that is produced, QC shall sample the aggregate and perform the consensus tests once every 10,000 tons with a minimum of one per mix per project. QA will independently sample the aggregate and perform the consensus tests once per project. QA should also test a minimum of one QC retained sample per project. For large projects, enough QC retained samples should be tested to ensure that QC is performing the tests correctly. These testing requirements are minimums and should be increased as necessary. During production, the following tolerances are applied (see Standard Specification Sections 403.2.1 through 403.2.5 and Consensus Testing).
| Property | Tolerance |
|---|---|
| FAA | 2% below the minimum |
| CAA | 5% below the minimum |
| Clay Content | 5% below the minimum |
| Thin, Elongated Particles | 2% below the minimum |
Moisture Content (Sec 403.5.9)
See also Asphalt Binder Content in Plant Inspection.
403.5.10 Contamination.
See Material Acceptance in Paving Operations.
403.2.6 Field Laboratory (Sec 403.6)
See Field Laboratory in in Plant Inspection.
403.2.7 Bituminous Mixing Plants (Sec 403.7)
See Batch Plants and Drum-mix Plants in Plant Inspection.
403.2.8 Hauling Equipment (Sec 403.8)
See Haul Trucks in Paving Equipment.
403.2.9 Pavers (Sec 403.9)
See Pavers in Paving Equipment.
403.2.10 Construction Requirements (Sec 403.10)
Weather Limitations (Sec 403.10.1)
See Weather Conditions in Paving Operations.
Substitutions (Sec 403.10.2)
The intent of this specification is that there be no additional cost to MoDOT as a result of the allowed substitution. Payment should be made for the mixture originally set up in the contract. Material codes for the substitute mixture should be entered in SiteManager on the line for which payment is being made. For example: Assume that the contractor wishes to use SP125 in lieu of the SP190 that is set up in the plans and that the SP125 has a higher contract unit price. Payment for the substitute mix should be paid as SP190. Material codes for SP125 should be added to the line for SP190 so that material quantities can be tracked and documented.
403.2.11 Field Adjustments of Job Mix Formulas (Sec 403.11)
If an unsatisfactory mix is produced, the contractor may adjust the JMF in the field. When an adjustment is made to one bin, an equal but opposite adjustment must be made to the other bin(s). For example, suppose that the cold feed system consists of five bins. If one bin is increased by 5%, another bin, or a combination of the other four bins, must be decreased by 5%. Additional fractions of aggregates already included in the JMF or new aggregates not included in the original JMF will not be allowed. The binder content may be adjusted by a maximum of 0.3% from the original JMF. Any time that adjustments are made to the plant percentages, including the hot bin percentages, the inspector and RE must be notified immediately. The resulting combined aggregate gradation of the adjusted mix must be within the master range for that particular type of mix (see Standard Specification Section 403.3.1). During production of the adjusted mix, the combined aggregate gradation must be within the limits of Standard Specification Section 403.5.1.1 or 403.5.1.2, whichever is applicable. If the cold feed settings have been adjusted, the composition of the mix has been changed. Therefore, the new bulk specific gravity of the combined aggregate (Gsb) must be calculated using the adjusted cold feed percentages so that the VMA can be accurately calculated during production. If an adjustment from the job mix is made, the contractor should be required to recalculate the porphyry/Non-carbonate percentage to assure that is still meets the contract requirements. A spreadsheet has been developed to assist in checking the contractor’s calculation. The spreadsheet can be found in the same folder on the V drive as the SuperPave spreadsheet. The aggregate bulk specific gravity should also be recalculated.
Field Mix Redesign (Sec 403.11.1)
If a new mix design is required, the contractor may redesign the mix in the field. All requirements of Standard Specification Section 403.4 will apply. A representative sample of a minimum of 50 lbs. shall be submitted with the new mix design to the Central Laboratory for verification testing.
Approval (Sec 403.11.1.1)
Construction and Materials will grant approval and assign a new mix number to the mix upon successful verification.
Resume Production (Sec 403.11.1.2)
No mix shall be produced or placed by the contractor or accepted for use by an inspector without approval of the new field mix design from the Materials Field Office. Once the mix design has been approved, production can resume.
403.2.12 Application of Prime or Tack (Sec 403.12)
See Surface Preparation in Paving Operations
403.2.13 Spreading and Finishing (Sec 403.13)
Standard Specification Section 403.13 puts restrictions on the minimum compacted lift thickness. See also Spreading and Hand Spreading in Paving Operations.
Paving Widths (Sec 403.13.1)
Standard Specification Section 403.13.1 puts restrictions on the paving widths and lengths if the pavement is constructed under traffic.
Segregation (Sec 403.13.2)
See Material Acceptance in Paving Operations.
Release to Traffic (Sec 403.13.3)
Traffic must not be allowed on the pavement until its surface temperature is 140°F or less. Otherwise, the traffic will overconsolidate the mat while it is still hot and cause the pavement to be more susceptible to rutting during its early life.
Draindown (Sec 403.13.4)
See Material Acceptance in Paving Operations.
Shoulder Substitutions (Sec 403.13.5)
The same Superpave mix that was used on the travel lanes may also be used on the shoulders. The density shall be in accordance with Standard Specification Section 403.5.2.1 if nonintegral shoulders are placed or 403.5.2.2 if integral shoulders are placed.
403.2.14 Spot Wedging and Leveling Course (Sec 403.14)
See Surface Preparation in Paving Operations.
403.2.15 Compaction (Sec 403.15)
Vibratory rollers shall be operated in static mode when the mix temperature is below 225°F. Pneumatic tire rollers shall not be used on SMA mixes. See Compaction in Paving Operations.
Rolling (Sec 403.15.1)
Defective Mixture (Sec 403.15.2)
See Material Acceptance in Paving Operations.
Non-traffic Areas (Sec 403.15.3)
Mixes used for non-traffic areas (medians, shoulders, and similar areas) shall be compacted to the required density. Density testing for Superpave mixes placed on the shoulders may be waived, at the RE’s discretion, once the contractor has established a roller pattern that has been shown to produce the required density. This means that cores must be taken until the RE is confident that density will be obtained consistently with this roller pattern. If testing has been waived, density must still be obtained and coring may be necessary to ensure that it is. Density testing will again be required at any time that changes in the material, mix temperatures, or roller pattern are made. The intent of the specification is to attain the required density on the shoulders, particularly on full depth pavements. On resurfacing projects, the existing shoulders may not be able to withstand the compactive effort needed to attain density. In this situation, the RE can relax the density requirements, but only to the point that conditions will allow. In other words, get the most density possible without tearing up the shoulders.
Density Measurement (Sec 403.15.4)
See Density in Plant Inspection and Density Samples in Paving Operations.
403.2.16 Joints (Sec 403.16)
See Transverse Joints and Longitudinal Joints in Paving Operations.
Joint Composition (Sec 403.16.1)
The density requirements in this section apply to the traveled way pavement within 6 in. of the longitudinal joint, including the pavement on the traveled way side of the shoulder joint. All mixes, except for SMA, shall have a minimum unconfined joint density of 90.0%. SMA mixes shall have a minimum unconfined joint density of 92.0%. Confined joint densities will be evaluated with the remainder of the mat and must meet the density requirements of Standard Specification Section 403.5.2.
403.2.17 Quality Control (Sec 403.17)
Quality Control Operations (Sec 403.17.1)
See Quality Control/Quality Assurance.
Asphalt Test Results (Sec 403.17.1.1)
A copy of all QC test results shall be furnished to the QA inspector no later than the beginning of the day after testing has been performed. All raw data and printouts must be included with the testing records. Raw data consists of all weights, measurements,etc. used to arrive at the final test results. Printouts include the gyration/height data from the gyratory compactor and the asphalt content ticket from the binder ignition oven or nuclear gauge. The testing records must be available to the QA inspector at all times. A self-test is a test that QC may perform between random testing to determine whether or not the mix is within specifications. Self-testing is not required and may be performed at any time and at any frequency. Generally, self-testing will be performed early in the production period. The self-test may not be completed in full. For example, QC may only compact the gyratory specimens. Doing so will yield specimen heights and the contractor may or may not make production adjustments based on these heights. Self-test samples must be clearly marked as such if they are tested and stored in the field laboratory. Self-test data may be used to determine removal limits if it is adequately documented. It should not be used for QLA under any circumstances. To be considered adequately documented the following criteria should be met:
- The gyratory pucks should be clearly identified and labeled and made available for verification.
- The gyratory printout should be available.
- The printout from the AC test should be available.
If the preceding conditions are met and the gyratory specimens are used to troubleshoot the placement, the specimens can then be weighed and bulked to determine the volumetric properties. Data from self-tests is approximate. Its only legitimate use to the QA inspector is to help determine the point on the roadway where the mixture transitioned either above or below the removal limits. We don’t want to remove acceptable mix or leave unacceptable mix in place.
See the Figure Appropriate Use of Self Tests.
It is QC’s responsibility to take appropriate action if unsatisfactory mix is being produced. This may include making adjustments to the plant to bring the mix back into specification, sampling the mix from the roadway and performing complete testing, removing mix from the roadway, etc. QC is not required to provide the QA inspector with self-test results. Self-test results will never be used to determine pay factors. However, if the self-test is well documented, the results may be used to determine removal limits, if necessary. A self-test is considered well documented if the gyratory specimen(s), gyration/height printout, and asphalt content ticket are available for QA’s review. The compacted specimens should be clearly marked as self-test specimens and may be tested if necessary.
Profilograph Test Results (Sec 403.17.1.2)
Example profilograph reports are shown for a quality assurance report and profile measurement report.
Bituminous Quality Control Plan (Sec 403.17.2)
See Quality Control/Quality Assurance.
Plant Calibration (Sec 403.17.2.2)
Retained Samples (Sec 403.17.2.3)
QC must retain the portion of each sample that is not tested after the sample has been reduced to testing size. This includes gradation, consensus, TSR, and volumetrics samples. The retained samples must be clearly identified in accordance with Standard Specification Section 403.17.2.3 and stored in the field laboratory for a minimum of 7 days. Also, all cores must be retained for a minimum of 7 days.
Gradation Sample (Sec 403.17.2.3.1)
QC will retain the portion of their gradation sample that is not tested. This includes the sample of the combined cold feed from a drum plant and all hot bin samples from a batch plant.
Loose Mix Sample (Sec 403.17.2.3.2)
A companion sample for all loose mix samples shall be taken and retained. However, the contractor is encouraged to sample a large amount of mix from the roadway, thoroughly blend the mix together, and then reduce the sample down to the necessary testing size. The portion that is not tested will be retained for possible use in the dispute resolution process. This is the preferred method because both halves should yield similar results.
Quality Control Laboratory (Sec 403.17.3)
Calibration Schedule (Sec 403.17.3.1)
Calibrations and verifications of the testing equipment are very important. If the equipment has not been calibrated or verified as required, false test results may be obtained. The maximum intervals are given in Standard Specification Section 403.17.3.1. These frequencies are taken from the AASHTO test methods and/or the manufacturer’s recommendations.
Calibration Records (Sec 403.17.3.1.2)
Periodically, the QA inspector should check the QC calibration records to ensure that the equipment has been calibrated or verified in accordance with Standard Specification Section 403.17.3.1.
403.2.18 Quality Assurance
See Quality Control/Quality Assurance.
Assurance Testing (Sec 403.18.1)
All QA samples will be independent from QC. QA must sample enough material to retain a sample. This retained sample, as with the QC retained sample, may be used during dispute resolution. QA will randomly sample the mix from the roadway once per lot and perform volumetric testing. At the beginning of the project, QC and QA should be given the opportunity to witness each other’s sampling and testing procedures. Any discrepancies should be immediately resolved at the project level, if possible. QA should test a QC retained volumetric sample once per day to ensure that both QC and QA are testing correctly. These samples should also be chosen at random (do not consistently test the retained sample from the same sublot every lot or develop a pattern).
When both QC and QA are confident in each other’s testing procedures and favorable comparisons have been obtained on the retained samples, testing of the QC retained volumetric samples may be performed on days that an independent sample is not taken. QA should test a QC retained gradation sample at a minimum of once per week. A minimum of one QC retained consensus sample should be tested per project. Again, all of the testing requirements previously mentioned are minimums and should be increased as necessary. QA test results will be furnished to the contractor no later than the day after testing has been performed. A QA/QC Checklist is attached. For additional information see QA/QC Questions and Answers.
Aggregate Comparison (Sec 403.18.2)
A favorable comparison will be obtained when the independent QA sample(s) meets specifications. In addition, the QA test results of a QC retained sample must be within the following tolerances from the QC test results:
If a favorable comparison is not obtained, dispute resolution procedures should be initiated. 403.18.3 Federal Highway Administration Requirements. 403.19 Acceptance of Material. 403.19.1 Random Numbers. All random numbers will be generated by QA at least one lot in advance. This includes the random numbers for the core locations and loose mix sample locations. A copy of the random numbers will be sealed in an envelope and given to the contractor upon completion of the lot. QC samples that are used to determine the pay factors must be taken at the locations designated by the random numbers unless circumstances warrant relocation. This could include close proximity to another QC sample location in the same production period, areas where mix must be placed by hand, etc. If necessary, the random samples may be separated by 200 tons. QC should be notified of the core location after rolling has been completed. QC should be notified of the loose mix sample location approximately 100 to 150 tons before the test. The independent QA sample must be taken at the location designated by the random number unless circumstances warrant relocation. This could include close proximity to a QC sample location in the same production period, areas where mix must be placed by hand, etc. If necessary the random samples may be separated by 200 tons. The test results from the independent QA sample will be compared to the QC test results to determine whether or not the QC test results adequately define the characteristics of the entire lot. However, QA may take additional samples Property Percentage Points ¾” sieve and larger ±5.0 ½” sieve ±5.0 3/8” sieve ±4.0
- 4 sieve ±4.0
- 8 sieve ±3.0
- 16 sieve ±3.0
- 30 sieve ±3.0
- 50 sieve ±2.0
- 100 sieve ±2.0
- 200 sieve ±1.0
CAA ±5.0 FAA ±2.0 Clay Content ±5.0 Thin, Elongated Particles ±1.0 General Construction Manual © Missouri Department of Transportation 2006 400-65 to determine if an area of concern complies with the specifications. The test results of these additional samples will not be compared to any QC test results. 403.19.2 Lots. For the purposes of pay factor determination, the mat will be divided into lots with a minimum of 4 sublots per lot. The maximum sublot size is 1000 tons. If a full lot cannot be completed, the extra sublots will be added to the previous full lot and the pay factors will be determined on the large lot. If there is no previous lot, the mix will be treated as small quantities and Standard Specification Section 403.23.7.4.1 will apply. If the target binder content is adjusted from the original JMF, a new lot shall begin. This will ensure that the binder content pay factor will represent the population of the adjusted mix. If the cold feed settings are adjusted from the original JMF alone, a new lot is not required. Adjusting the cold feed settings will change the Gsb and, therefore, the VMA of the mix. However, the VMA specification limits are based on the type of mix (see GCM Section 403.5.4 “Voids in the Mineral Aggregate (VMA).” on page 55) and do not change. The VMA is required to be within this range, even if changes are made to the JMF. A new lot sequence shall begin when a new mix design is established. The limits of adjustment can be found in Standard Specification Section 403.11. 403.19.3 Test and Pay Factor Items. The minimum sampling and testing requirements for both QC and QA, as shown in the table in Standard Specification Section 403.19.3, have been modified as a result of the QC/QA Process Team. The guidelines set forth in this document should be followed. In regards to note b, one core equals one sample and the results will be used to determine the density pay factor for the corresponding sublot. However, if stated in the QC Plan, a maximum of two additional cores may be taken per sublot. This gives a maximum total of three cores per sublot. One core must be taken at the location selected by random numbers. The remaining cores must be taken at the same transverse offset within one foot longitudinally of the location selected by the random numbers. If more than one core is taken per sublot, all of the cores will be combined into one sample. This means that the average density of the cores will be used to determine the density pay factor for the corresponding sublot. 403.19.3.1 Test Method Modification. 403.19.3.1.1 Binder Ignition Modification. This specification adjusts the temperature of the binder ignition oven due to the breakdown of certain aggregate formations as a result of intense heat. 403.19.3.1.2 Rice Test. If the absorption of any aggregate fraction used in the mix is greater than 2.0%, AASHTO T209 must be modified in accordance with Standard Specification Section 403.19.3.1.2. This procedure is called the dry-back method. The final surface-dry weight will be recorded in the APIW as “A2”. If necessary, the dry-back method should be performed on all samples taken in the first lot of mix produced. If the initial Gmm and the dry-back Gmm of a sample are within 0.002 of each other in all sublots of the first lot, the dry-back may be reduced to every other sublot. Otherwise, the dry-back will be required every sublot. 403.19.3.2 Miscellaneous Applications. 403.19.3.2.1 Small Quantities. A mix that requires less than 3000 tons on a project is referred to as small quantities. Testing frequencies will be as stated in Standard Specification Section 403.19.3.2.1(b). If a project is initially setup with less than 3000 tons, pay factors will not Division of Construction and Materials 400-66 © Missouri Department of Transportation 2006 be determined unless an adjustment is made to the contract to before production begins. If a project is initially setup with more than 3000 tons but less than 3000 tons are placed, pay factor determination is not required and Standard Specification Section 403.23.7.4.1 will apply. 403.19.3.2.2 Base Widening and Entrances. 403.19.4 Dispute Resolution. See also GCM Section 400.2 “Quality Control/Quality Assurance (QC/QA).” on page 1. 403.19.4.1 Cease Work. 403.19.4.2 Third Party Resolution. 403.19.4.3 Third Party Payment. 403.19.4.4 Other Adjustments. 403.20 Surface Test. 403.20.1 Straightedging. 403.20.2 Profilographing. 403.21 General Requirements. 403.21.1 Sequence of Operations. 403.21.2 Pavement Marking. 403.21.3 Surfaced Approaches. 403.21.4 Filling Drain Basins. 403.21.5 Pavement Repairs (Blow-ups). 403.22 Method of Measurement. 403.22.1 Weight Determination. If a batch plant is used to produce the mix, the weight of the load will be determined by the batch weights. If the mix is produced in a drum plant, the weight of the load will be determined by weighing each load of mix. This can be accomplished with either a silo scale or a truck scale. These individual load weights will be added together for the total tonnage accepted for the project and rounded to the nearest 0.1 ton. 403.22.2 Full Depth. 403.22.2.1 The final driving surface area (length multiplied by width) of the pavement will be used as the area of all underlying lifts and courses. Any mix that is placed outside of this area, including the mix used to construct the 1:1 slope, will not be directly paid for. 403.22.2.2 Full depth pavements will be paid for by the square yard. If authorized changes are made to the contract quantity during construction or if errors are found in the contract quantity, the applicable completed pavement will be measured to the nearest 0.1 yd2. The reviGeneral Construction Manual © Missouri Department of Transportation 2006 400-67 sion or correction will be added to or deducted from the contract quantity. If no changes are made or errors found, the pavement will not be measured and the contractor will be paid for the quantity of mix as shown in the contract. 403.22.3 Alternate Overlay. An overlay project may be bid as Portland cement concrete or asphalt. 403.22.3.1 Field Established Quantity. The field established plan quantity is the tonnage of mix that is determined from the set or adjusted profile. This will be the contract quantity for an asphalt overlay. 403.22.3.2 Overlay Measurement. Overlays will be paid for by the ton. If authorized changes are made to the contract quantity during construction, the applicable completed pavement will be measured to the nearest 0.1 ton. The revision will be added to or deducted from the contract quantity. If no changes are made, the pavement will not be measured and the contractor will be paid for the quantity of mix as shown in the contract. 403.22.4 Pavement Testing. See also GCM Section 400.7.10 “Density Samples.” on page 34. 403.22.4.1 Pavement Thickness. 403.22.4.2 Surface Restoration. 403.23 Basis of Payment. 403.23.1 Aggregate Variation. The specific gravity of the aggregates used in the mix may fluctuate because of a variation in the quality of the rock within the quarry ledge. The gradation of the aggregate may also cause some fluctuation. However, this contribution is usually negligible. Because of such fluctuations, the quantity of aggregate used in the mix may vary from the quantity specified in the contract. Since this is expected and unavoidable, the contract unit price will not be adjusted. 403.23.2 Compacted Samples. The cost of cutting QC cores is included in the contract. Therefore, no direct payment will be made. QA samples will be paid for at $75.00 per sample, per Standard Specification Section 109.15. If one QA core is cut per location, that core is equal to one sample. If more than one QA core is cut per location, the test results will be averaged and those cores will equal one sample. 403.23.3 Payment for Pavement Repairs (Blow-ups). 403.23.4 Smoothness Adjustment. 403.23.4.1 Diamond Grinding. Areas of the final driving surface that must be corrected by diamond grinding will not be considered as a marred surface. However, a tack coat must be applied to these areas so that the surface is adequately sealed. The tack must be cut (diluted) with water so that the resulting mixture is at most 50% tack. The tack shall be applied at a rate near the lower limit of the range specified in Standard Specification Section 407.4.2. The inspector should ensure that the proper application procedures are used. Excess tack must be blotted with sand. No direct payment will be made for this application. 403.23.4.2 Testing Cost. Division of Construction and Materials 400-68 © Missouri Department of Transportation 2006 403.23.4.3 Width Limitation. 403.23.5 Tensile Strength Retained Adjustment. The tonnage represented by each QC TSR sample is subject to a pay adjustment that depends on the test results. The adjustments to the contract unit price are given in Standard Specification Section 403.23.5. Continuing with the sampling example in GCM Section 403.5.6, the contractor takes ten samples that represent 10,000 tons each. The last two samples represent 6,480 tons each. The contractor’s test results are shown in order in the table below. The price per ton is $35.00. The contract adjustment is calculated as follows: Contract Adjustment = ((Percent of Contract Price-100)/100) * Price/ton * Tons The Pay Factor Worksheet will automatically calculate the contract adjustment once the appropriate information has been entered. The contractor’s TSR results should be recorded in the Pay Factor Worksheet that corresponds with the lot that the sample was taken in. 403.23.6 Density Adjustment. QC will take one unconfined longitudinal joint core per sublot, if applicable. These cores will be taken within 6 in. of the unconfined longitudinal joint. Unconfined joint cores can either be located at the same longitudinal location as the corresponding mat density cores or separate random numbers can be generated. The test results for each lot will be averaged to determine compliance with the specifications. Pay adjustments will be in accordance with the following table and will be applied to the corresponding tonnage represented by the core(s): TSR Tonnage Percent of Contract Price Contract Adjustment (Bonus/Deduct), $ 84 10,000 100 0 87 10,000 102 7,000 88 10,000 102 7,000 92 10,000 103 10,500 86 10,000 102 7,000 83 10,000 100 0 81 10,000 100 0 76 10,000 100 0 74 10,000 98 -7,000 80 10,000 100 0 78 6,480 100 0 85 6,480 102 4,536 Total 112,960 29,036 General Construction Manual © Missouri Department of Transportation 2006 400-69 If pay reductions are necessary, the lower adjusted contract unit price of the PWL or the unconfined joint density adjustment will apply to the corresponding tonnage. For example, assume that the lot size is 4000 tons and that 1000 tons in the lot has an unconfined joint. The total pay factor for the lot due to volumetric testing is 105%. A longitudinal joint core is taken as required and the pay factor due to the unconfined joint density is 90%. As a result, a 10% reduction to the contract unit price will be applied to the 1000 tons represented by the unconfined joint and a 5% bonus will be paid for the remaining tonnage in the lot (3000 tons). On the other hand, if the pay factor due to the unconfined joint density were 100%, the 5% bonus would be paid for the entire lot. Longitudinal joint density is very important and this is an attempt to ensure that density is achieved. If it is not, the joint will ravel. 403.23.7 Percent Within Limits (PWL). The mean (xa), standard deviation (s), Upper Quality Index (Qu), Lower Quality Index (Ql), and total percent within limits (PWLt) are calculated for each pay factor item in each lot using the equations given in Standard Specification Section 403.23.7. The PWL for an item can be determined using Table III in Standard Specification Section 502.15.8. To use this table, calculate the Qu of the item and round the result to two digits (X.XX). Find the result in the left hand column of the table and move along the row to the right until reaching the column with the corresponding n-value. The n-value is the number of test results for the item in the lot. This process yields the upper percent within limits (PWLu) of the item. Repeat this process to determine the lower percent within limits (PWLl) of the item using the Ql. Finally, calculate the PWLt. If a QLongitudinal Joint Density (Percent of Gmm) Pay Factor (Percent of Contract Unit Price) For all SP mixtures other than SP125xSM: 90.0 to 96.0 inclusive 100 96.1 to 96.5 or 89.5 to 89.9 inclusive 90 96.6 to 97.0 or 89.0 to 89.4 inclusive 85 97.1 to 97.5 or 88.5 to 88.9 inclusive 80 97.6 to 98.0 or 88.0 to 88.4 inclusive 75 Above 98.0 or Below 88.0 Remove and Replace For SP125xSM mixtures: 92.0 100 91.5 to 91.9 inclusive 90 91.0 to 91.4 inclusive 85 90.5 to 90.9 inclusive 80 90.0 to 90.4 inclusive 75 Below 90.0 Remove and Replace ≥ Division of Construction and Materials 400-70 © Missouri Department of Transportation 2006 value is negative, subtract the PWL-value from 100. The Pay Factor Worksheet will automatically calculate the PWLt for each pay factor item in each lot. 403.23.7.1 Quality Level Analysis. 403.23.7.1.1 Acceptance. 403.23.7.1.1.1 The QC test results will be used to determine the PWL as long as QC and QA compare favorably. If a favorable comparison is not obtained, dispute resolution procedures should be initiated. If dispute resolution is carried out to independent third party testing and the QC test results have been determined to be correct by the third party, the QC test results will be used to calculate the PWL. If the QA test results have been determined to be correct by the third party, the QA test results will be included in the PWL calculation. 403.23.7.1.1.2 A favorable comparison is obtained when the QA test results of a random, independent sample are within two standard deviations of the average of the QC test results. This determination cannot be made until all random testing for the lot has been completed. If the QC test results vary within the specification tolerances, the standard deviation will be large. In fact, as the variability in the QC test results increases, the standard deviation also increases. This results in a wide comparison range and low pay factors. On the other hand, if there is little variability in the QC test results, the standard deviation will be small. The comparison range will be narrow and the pay factors will increase. In this case, a favorable comparison is obtained when the QA test results are within one-half of the specification tolerances of the QC average. For example, the specification tolerances for VMA are –0.5% to +2.0%. One-half of this range is 1.25%. Therefore, a favorable comparison is obtained if the QA test result is within ±0.6% of the QC average. If the comparison is not favorable, the first step is to review both QC and QA test results to see if there is any noticeable error. If no errors are found, testing of the retained samples may be performed. Judgment must be used in determining which retained sample(s) to test. When testing a retained sample, the entire suite of tests (%AC, Va, and VMA) should be performed to verify the validity of the original test results. If the test results of the retained sample confirm the original test results, the original test results are used to determine the PWL. If the test results of the retained sample verify that the original test results were incorrect, the test results of the retained sample are used to determine the PWL. If the QC and QA test results have been determined to be valid and the comparison is still unfavorable, the test results from the random, independent QA sample will be included in the PWL calculation. The QA test results of QC retained samples or the test results from any additional QA samples will not be used in the PWL calculation. As an example, lot 3 has been completed and consists of 4 sublots. A favorable comparison was not obtained but it was determined that the QC and QA test results are valid. Therefore, the PWL calculation will include the QC test results from all 4 of the sublots and the test results of the random, independent QA sample (n = 5). A favorable comparison is obtained when the QA test results of a QC retained volumetric sample are within 0.005 of the QC Gmm test results, within 0.010 of the QC Gmb test results, and within 0.1% of the QC asphalt content test results. If larger variances occur, both QC and QA should investigate the sampling and testing procedures to identify and rectify the cause of the discrepancy. 403.23.7.1.2 Outliers. If it is suspected that an individual QC test result is an outlier, the entire lot of QC test results may be checked in accordance with Standard Specification Section 403.23.7.1.2. The eligible measured test results are Gmb, Gmc, Gmm, and %AC. Gmb, Gmc, and General Construction Manual © Missouri Department of Transportation 2006 400-71 Gmm shall be carried out to three decimal places (X.XXX) and the %AC shall be carried out to two decimal places (X.XX). On the other hand, Va, VMA, and density are not eligible because these are calculated volumetric properties. If an outlier is found, QC may test the retained sample from the corresponding sublot. Again, the entire suite of tests (%AC, Gmb, and Gmm) must be performed. If the test results from the retained sample confirm the original test results, the original test results will be used to calculate the PWL. If the test results from the retained sample do not confirm the original test results, the test results from the retained sample will be used to calculate the PWL. When any change is made in the JMF, the previous test results cannot be used for future outlier calculations since the mix has changed. For example, if the contractor has made a change in sublot 2B and wants to check for an outlier in sublot 2D, the results from sublot 2A cannot be used since the mix is not the same. 403.23.7.1.3 Roadway/Shoulder Lots. 403.23.7.1.4 Random Sampling. See GCM Section 403.19.1 “Random Numbers.” on page 64. 403.23.7.2 Pay Factors. The density (PFdensity), asphalt content (PFAC), VMA (PFVMA), and air voids (PFVa) pay factors are calculated for each lot using the corresponding PWLt and the equations in Standard Specification Section 403.23.7.2. The total pay factor (PFT) is then calculated for each lot using the average of the individual pay factors. If coring is not required, such as on a leveling course or non-integral shoulders, the PFT will be calculated for each lot using the average of the PFAC, PFVMA, and PFVa. The contract adjustment is used to adjust the contractor’s pay to reflect the quality of the mix. The contractor may receive a bonus if the quality of the mix is good. On the other hand, if the quality of the mix is poor, a deduction will be applied. The contract adjustment is calculated by subtracting 100% from the PFT. The dollar amount of the bonus or deduction is determined by multiplying the unit bid price, the quantity of mix in the lot, and the contract adjustment (in decimal form) together. Mix is typically produced and measured by the ton. Therefore, in order to eliminate confusion and excessive conversions on square yard projects (full depth pavements), the lots will be tracked by tonnage. When the pay factors are calculated at the end of the lot, the “Square Yard Calculator” in the Pay Factor Worksheet can be used to determine the square yards in the lot. This is best explained with an example: On a full-depth paving project, the total thickness of the pavement is 12 in. and the contractor is placing two lifts of SP190, one 6 in. lift and one 4.25 in. lift. The final lift of SP125 is 1.75 in. thick. The lot size is 3000 tons. Suppose that one lot of SP190 has been completed. The total thickness of the pavement and the lift thicknesses are entered in the appropriate cells in the “Square Yard Calculator”. The length and width of the lot must be measured manually. The width of the lot is 12 ft., the length of the first lift is 4650 ft., and the length of the second lift is 3300 ft. Therefore, the area of the first lift is 6200.0 yd2 (12 ft. * 4650 ft. = 55800 ft2 * (1 yd2/9 ft2) = 6200 yd2) and is entered in the appropriate cell. The area of the second lift is 4400.0 yd2 (12 ft. * 3300 ft. = 39600 ft2 * (1 yd2/9ft2) = 4400 yd2) and is entered in the appropriate cell. The square yardage represented by each lift is calculated by multiplying the square yards by the lift thickness divided by the total pavement thickness. Therefore, the square yardage of the first lift is 3100.0 yd2 (6200 yd2 * (6 in./12 in.) = 3100 yd2) and the square yardage of the second lift is Division of Construction and Materials 400-72 © Missouri Department of Transportation 2006 1558.3 yd2 (4400 yd2 * (4.25 in./12 in.) = 1558.3 yd2). This lot represents 4658.3 square yards. This procedure is followed for the remaining lots. 403.23.7.2.1 Density Pay Factor. Density is calculated using the Gmc of the core and the Gmm of the mix. The PFdensity for each lot is calculated using the density test results of all of the sublots. Cores that are cut in half, as required by Standard Specification Section 403.15.4, will double the number of test results used to determine PFdensity. For example, suppose that the contractor is placing SP190 in 8” lifts and 4 cores are taken per lot, 1 per sublot. The lift is being placed thicker than 6 times the nominal maximum size aggregate used in the mix. By specification, the cores are to be cut in half and the density of each half determined separately. Therefore, 8 test results (as opposed to 4) will be used to determine the PFdensity for the lot. 403.23.7.2.2 Asphalt Content Pay Factor. The PFAC for each lot is calculated using the binder content test results of all of the sublots. 403.23.7.2.3 Voids in the Mineral Aggregate and Air Voids Pay Factor. The Va, VMA, and VFA are calculated using the average Gmb of the compacted gyratory specimens, the Gmm of the mix, the percent stone (Ps) of the mix, and the Gsb of the combined aggregate. The Ps is determined by subtracting the percent binder (Pb) from 100%. The Gsb will be that listed on the JMF. The PFVa and PFVMA for each lot are calculated using the Va and VMA test results of all of the sublots. 403.23.7.3 Removal of Material. If the PFT for a lot is less than 50.0, the entire lot must be removed and replaced at the contractor’s expense. If the QC test results for density and/or air voids fall below the removal limits in any sublot, the affected mix must be removed and replaced at the contractor’s expense. The specifications state that the entire sublot must be removed. However, in some cases only a portion of the affected sublot(s) may require removal. Therefore, the limits of removal will be left up to the RE’s discretion. QC self-test results may be used to help define the limits of removal as long as the self-test(s) are well documented (see GCM Section 403.17.1.1 for the documentation requirements). The replacement mix will be sampled and tested as required. These test results will be used to calculate the PWL for the lot. If the QA test results fall below the removal limits for density and/or air voids, the mix should stay in place if a favorable comparison has been obtained with the QC test results. Again, a favorable comparison signifies that the QC test results adequately define the characteristics of the lot and are, therefore, acceptable. If the QA test results fall below the removal limits and a favorable comparison has not been obtained, dispute resolution should be initiated to determine whether or not the mix should stay in place. 403.23.7.4 Miscellaneous Applications. 403.23.7.4.1 Small Quantities. For small quantity projects consisting of less than 3000 tons, the statistical analysis of the mix is not required. Therefore, pay factors will not be determined. However, the mix must meet density, binder content, VMA, and Va specifications. The testing frequencies are stated in Standard Specification Section 403.19.3.2.1(b). Density will be adjusted in accordance with the table in Standard Specification Section 403.23.7.4.1(b). TSR testing is also required. 403.23.7.4.2 Base Widening and Entrances. 403.23.7.4.3 Single Lift or Leveling Course Work. This specification does not apply to “mill and fill” projects.
403.3 Materials Inspection
403.1 Scope. To establish procedures for mix design of asphaltic concrete pavement, inspection and acceptance of bituminous mixture. Ingredients for use in asphaltic concrete pavement are to be inspected in accordance with the applicable sections of this Manual. Plant calibrations, if requested, will be performed in accordance with General Section 10 of this Manual.
403.2 Mix Design Procedure. In order for an asphaltic concrete mix formula to be approved, the contractor’s proposed job mix formula (JMF) shall be submitted as required in Section 403.3.1. The time for approval starts when the completed design is delivered to the District. This time restarts when the District receives information omitted from the original JMF or corrected by the contractor. Review times include District and Central Office processing, therefore, each mix should be processed as soon as possible. When the contractor is not accepted as a participant in the AASHTO Proficiency Sampling Program, material sampling is required for mixture verification. Trial mix samples must be obtained and submitted to the Central Laboratory in accordance with Field Sec 1001 of this Manual. When possible, the JMF and correspondence should be transmitted electronically. The Materials Field Office e-mail address is MFO. 403.2.1 District Procedure. When the District receives a proposed trial mix formula, as required by the Standard Specifications, the mixture properties, components and proportions should be checked to ensure compliance with Specifications and that they are approved for the intended use. It may be necessary for the District to advise the contractor to make changes in the proposed mixture in order to comply with Department policies. The District shall provide SiteManager ID’s and all pertinent information (gradation, deleterious, etc.) for each fraction of aggregate used in the mixture. A QC plan in accordance with Field Sec 1001 of this Manual covering each aggregate fraction should be on file in the District Office or received with the JMF. The target gradations shown on the QC plan and JMF must match. When the District is satisfied that the proposed mixture is acceptable, a copy of the JMF and the contractor's letter shall be submitted to the Materials Field Office, accompanied by a letter of transmittal with comments, any corrections made and recommendations. The transmittal letter shall contain the following information: Project information – Job Number, Route, County, Contract Number. Mixture Types Grade and Source of Asphalt Binder Letting Date Proposed Work – Type of Work, Job Location and Length Average Daily Traffic (ADT) Total Trucks Total Combination Trucks Mix Use – Mainline, Shoulders, Outer Roads, Entrances, etc. Quantity of Mix Included in the letter should be information regarding the approximate date on which the contractor intends to begin placing the mixture on the roadway, the type of mixture needed first and whether the JMF is submitted for a 7-day review or verification. Information concerning plant location, type of plant to be used, etc., is beneficial. 403.2.1.1 If the mixture design is performed by a laboratory participating in the AASHTO Proficiency Sampling Program with a rating of 3 or more on the applicable test methods, trial FS-403 (Page 2 of 4) (Rev 11-19-04) MATERIALS mix material does not need to be submitted to the Laboratory unless one or more of the following conditions apply: a. Nuclear calibration for MoDOT asphalt content gauges is needed. b. Material for full verification of the mixture is requested by the Field Office. c. District personnel have concerns over any aspect of the mix design. 403.2.1.2 Requests for previously approved mixes shall be submitted and will be approved in accordance with applicable portions of this Section. Mixtures approved under pre-2004 Standard Specifications may be transferred within the time limit of 3 years from the approval date. Transfer requests for mixtures that exhibited poor performance or field problems should be denied. 403.2.1.3 Upon request by the contractor, the District has authority to change the source of mineral filler, hydrated lime, natural sand from the Missouri and Mississippi Rivers or asphalt binder. However, constant changing throughout a project should not be allowed. The contractor must provide reasonable justification for changing sources during the course of a project. Any adjustments should be made to the JMF to reflect changed properties caused by the new source. (e.g. Change in Gsb, gradation, asphalt content, etc.) 403.2.1.4 Approval of a new mix design shall be obtained prior to changing the source of aggregates used in a mixture. 403.2.2 Field Office Procedure. The Materials Field Office is charged with the responsibility of processing the mix formula. General procedures for processing an asphaltic concrete mix formula are as follows: a. A letter from a District requesting a mix with a copy of the contractor's JMF and letter is received. b. Contract Special Provisions for the project are checked for necessary items. c. The urgency of the mix and the status of trial mix samples in the Central Laboratory are reviewed. d. Grade of asphalt as well as the refinery to be used and the percent asphalt recommended are reviewed. e. Gradations of the individual aggregates are checked for specification compliance and compared with the gradations determined by the Laboratory. f. All calculations on the proposed JMF are checked. g. For verification, a one-point trial is prepared and submitted to the Laboratory. h. When Central Laboratory tests are completed, the results are compared to the contractor’s and against the specifications. If the mixes tested cannot be used, the mixture will be rejected. i. Formulas to check aggregate and mixture properties are shown in LS 403. j. Absorption values obtained by AASHTO T85 or T85 Combined will be shown on the FS-403 (Page 3 of 4) (Rev 11-19-04) MATERIALS JMF for determining which mixtures require the optional dry-back procedure of AASHTO T209. 403.3 Field Adjustments of Superpave Mix Design. The specification criteria are to be used to determine whether or not the mixture meets the specifications. When a mixture is field adjusted, the contractor is to notify the inspector prior to making the adjustment. A new Gsb is required when cold feed adjustments are made. A new lot will begin with any change in asphalt content. Adjustments beyond the limits set in the specifications will require a new mix design. Field adjusted mixture changes are not required to be sent to the Field Office, however, the District will track the changes to ensure proper material quantities are inspected. 403.4 Field Superpave Mix Design. When a field mix design is needed, the contractor must first notify the engineer (the Materials Field Office is to be notified immediately). During the design and verification process, no mixture is to be placed on the project. A plan for producing, sampling and verifying the proposed field mix design is to be agreed on between the contractor and the engineer. One hundred (100) pounds of loose mixture will be required in the Central Laboratory and the Materials Field Office will approve or deny the field mix design. In order to be accepted for use, the test results must meet all of the following: a. Minimum VMA for the mixture type, i.e., 12.0 minimum for 250 mixes, 13.0 for 190 mixes, 14.0 for 125 mixes, and 17.0 for 125 SMA mixes. b. Asphalt content within 0.3 % of the adjusted target. For example, if the contractor chose to lower the asphalt content from 5.0 percent to 4.8 percent for a field adjustment, the initial test results must be within 0.3 % of 4.8 percent. c. Air voids of 4.0 +/- 0.5 d. TSR result is equal to or greater than 80%. The contractor and Central Laboratory may run the moisture sensitivity test simultaneously. If the contractor’s test results meet the above criteria, and the results are verified by the Central Laboratory, the target VMA will be set at the contractor's test result, the target AC content will be set at the target set for the field mix design, and the air voids target will be set at 4.0. 403.5 Report. A letter of transmittal will accompany the approved mixture to the district Operations Engineer with distribution as follows: Title (e-mail address) Copy of Letter of Transmittal & Approved Mix District Operations Engineer (D#MaContacts) 1 Construction and Materials Clerk 1 Resident Engineer (POorg) 1 Physical Laboratory Director (PLO) 1 Chemical Laboratory Director (Extraction) 1 Design Representative 1 Field Office File 1 Contractor 1 The letter of transmittal and the approved mixture will be sent by electronic mail to the individuals listed above. FS-403 (Page 4 of 4) (Rev 11-19-04) MATERIALS A copy of the approved formula accompanied by a letter of transmittal from the District Operations Engineer is to be forwarded to the contractor when an electronic mail address for the contractor has not been provided.