Category:401 Bituminous Base and Pavement
401.1 Design
401.1.1 Plant Mix Bituminous Base (PMBB) Course
Use of PMBB courses should be limited to bituminous bases beneath Plant Mix Bituminous Pavement (PMBP) surface mixtures on full depth light duty pavements, as base widening on routes designated as light duty corridors, or on any bypasses or temporary roadways, regardless of the corridor designation. A SP250 mixture may be used in lieu of a PMBB mixture when ADT is less than or equal to 3500. Such a substitution should be limited and requires approval by the District Operations Engineer. A PMBB mixture cannot be placed in lifts of less than 3 in. (75 mm) or greater than 6 in. (150 mm) in thickness (six times the maximum aggregate diameter). Mineral aggregate-gradation requirements are set forth in the standard specifications. An approved commercial mixture may be used in lieu of PMBB mixtures for work that is considered temporary construction, primarily defined as work that is to be removed prior to completion of the contract, pavement that will become non-mainline pavement, or pavement that will not remain in MoDOT inventory. The Construction and Materials Division Pavment Team should be contacted to determine whether commercial mixture would be an appropriate substitution. After concurrence from Pavement Team, the designer should note on the 2B sheets in the “Remarks” section where a commercial mixture may be substituted for a PMBB mixture and on the typical section.
401.1.2 Plant Mix Bituminous Pavement (PMBP)
Use of mineral aggregate-gradation, BP-1, should be limited to a surface mixture for full-depth construction of light duty pavements, resurfacing or contract leveling projects. Guidance for using this mix is given in Mix Selection. The thickness of the PMBP mixture should be 1 ¾ in. (45 mm) to 3 in. (75 mm). It may also be used as an underlying lift when the PMBB cannot be used because of thickness limitations, i.e., total overlay thickness is 3 ¾ in. [95 mm] or less. Where it is desirable to eliminate edge drop off treatment, BP-1 may be used in lieu of the 4" (100 mm) PMBB. However, it is recommended for normal applications, use the 4" (100 mm) PMBB. An SP125 mixture should not be used in lieu of a PMBP mixture, unless approved by the District Operations Engineer. An approved commercial mixture may be used in lieu of PMBP mixtures for work that is considered temporary construction, primarily defined as work that is to be removed prior to completion of the contract, pavement that will become non-mainline pavement, or pavement that will not remain in MoDOT inventory. The Construction and Materials Division Pavement Team should be contacted to determine whether commercial mixture would be an appropriate substitution. After concurrence from the Pavement Team, the designer should note on the 2B sheets in the “Remarks” section where a commercial mixture may be substituted for a PMBP mixture and on the typical section.
The designer may use any reasonable combination of lifts, but the normal lift thicknesses should be:
- 1 ¾" BP-1
- 3 ¾" = 1 ¾" BP-1 over 2" BP-1
- 5 ¾" = 1 ¾" BP-1 over 4 " PMBB
- 7 ¾" = 1 ¾" BP-1 over 6" PMBB
401.2 Construction Inspection
401.2.1 Material (Sec 401.2)
See Processing Reclaimed Asphalt
401.2.2 Composition of Mixtures (Sec 401.3)
The aggregate sources used in the mix must be the same as those required by the JMF. The combined aggregate gradation of PMBB and PMBP mixes shall be in accordance with Standard Specification Section 401.3.1. See also Processing Reclaimed Asphalt
401.2.3 Job Mix Formula (Sec 401.4)
Mixture Approval (Sec 401.4.3)
No mix shall be produced or placed by the contractor or accepted for use by an inspector without an approved JMF. Construction and Materials will give written approval. In some extreme cases, approval may be verbal with written approval to follow. A new JMF may be required if a material source is changed or if an unsatisfactory mix is produced. Mixes that require an adjustment in the cold feed settings in excess of ±5.0% may be redesigned in the field based on the characteristics of the mix actually produced by the plant. These new field mix designs must meet the requirements of Standard Specification Section 401 and will be verified by Construction and Materials. A new combined Gsb must be calculated since the overall composition of the mix has been changed.
Moisture Susceptibility (Sec 401.4.5)
Moisture susceptibility of BB and BP mixes is mainly an issue during the mix design process. However, if conditions in the field arise that may warrant TSR testing, a sample (roughly 75 lbs. of loose mix) should be sent to the Central Laboratory. Reasons to sample the mix for TSR testing are evidence of binder separation from the mix, if the PI of the fine aggregate fractions has significantly increased, or if the overall quality of the aggregate has changed.
Time Limit (Sec 401.4.6)
A satisfactory mix may be transferred from one project to another for a maximum of three years from the original approval date. A mix may be transferred for a number of reasons. The mix originally approved for the project can no longer be used after another mix has been transferred.
401.2.4 Gradation Control (Sec 401.5)
The combined aggregate gradation must be within the master range specified in Standard Specification Section 401.3.1 at all times. QC should determine the gradation of the RAP, if used, at a minimum of once a day and the results used to determine the combined aggregate gradation. During production, the combined aggregate gradation can vary from the JMF by the maximum tolerances shown in the table below. The mix shall be produced at the binder content shown on the JMF. However, the binder content of the mix, as determined by sampling and testing, must be within the following maximum tolerance from the JMF:
| Property | Tolerance |
|---|---|
| # 8 sieve | ±5.0% |
| # 200 sieve | ±2.0% |
| Binder Content | ±0.5% |
The binder content, as shown on the JMF, cannot be changed during production without written approval from Construction and Materials, even if the resulting binder content is within the tolerance from the JMF. If a new binder content is approved, the tolerance will apply to the new target.
Sample Location (Sec 401.5.1)
See Processing Reclaimed Asphalt and Asphalt Binder Content and Sieve Analysis in Plant Inspection
Substitutions (Sec 401.5.2)
Any mix with a smaller size aggregate may be substituted for any PMBB or PMBP mix. A Superpave mix with the same or smaller size aggregate, except design level B mixes, may also be substituted for any PMBB or PMBP mix. For example, a BP, SP190, or SP125 mix may be substituted for a PMBB mix. An SP125 mix may be substituted for a PMBP mix. Regardless of the type of mix substituted, the lift thickness and density requirements of Standard Specification Section 401 apply. Substitutions require a no-cost change order.
Moisture Content (Sec 401.5.4)
See Asphalt Binder Content in Plant Inspection.
Contamination (Sec 401.5.5)
See Material Acceptance in Paving Operations.
401.2.5 Field Laboratory (Sec 401.6)
See Field Laboratory in Plant Inspection.
401.2.6 Construction Requirements (Sec 401.7)
Weather Limitations (Sec 401.7.1)
See Weather Conditions in Paving Operations.
Bituminous Mixing Plants (Sec 401.7.2)
Subgrade Preparation (Sec 401.7.3)
See Surface Preparation in Paving Operations.
Hauling Equipment (Sec 401.7.4)
See Substitutions in Paving Equipment.
Spreading (Sec 401.7.5)
See Spreading and Hand Spreading in Paving Operations.
The compacted thickness and the cross section shown on the plans must be obtained by placing the mix in the required number of layers and quantity. If the pavement consists of multiple lifts with varying thicknesses, the thickest lift must be placed first. The maximum compacted thickness of a single lift of BP is 2 in. for the surface course and 4 in. for the leveling course.
Irregularities (Sec 401.7.5.1)
See Spreading and Material Acceptance in Paving Operations.
Base Widening (Sec 401.7.5.3)
See Surface Preparation in Paving Operations.
Joints (Sec 401.7.6)
See Transverse Joints and Longitudinal Joints in Paving Operations.
The minimum density requirement of all traveled way pavement within 6 in. of a longitudinal joint is 90.0%. This includes the pavement on the traveled way side of a shoulder joint. Once the contractor establishes a roller pattern that produces the required density, testing may be waived with approval from the RE. Density testing will again be required at any time that changes in the material, mix temperatures, or roller pattern are made. Pay adjustments due to longitudinal joint density apply to the production period from which the cores are obtained and to the full width of the lane.
'Compaction (Sec 401.7.8)
See Density in Plant Inspection Compaction in Paving Operations.
The minimum density requirement is 92.0%. The density may be determined by coring or by the direct transmission nuclear method in accordance with MoDOT Test Method TM-41. However, coring is the preferred method as the nuclear method is only a correlation. Also, the correlation may take a significant amount of time to develop. Mixes with no density requirements are compacted in accordance with Standard Specification Section 401.7.8.
401.2.7 Quality Control (Sec 401.8)
The applicable portions of Standard Specification Section 403.17 apply, except that a QC Plan will not be required.
Mixture Testing (Sec 401.8.1)
If production is greater than 1000 tons per day, the contractor is required to determine the gradation and the binder content of the mix at a minimum of once every 1000 tons. If production is less than 1000 tons per day, the contractor is required to test the mix at least once. Testing may be waived, with the RE’s approval and the contractor’s certification of the mix, when less than 200 tons are produced per day.
Failing Test (Sec 401.8.2)
If the gradation or binder content test results fall outside of the tolerances, the contractor shall review the plant settings and make any necessary adjustments. As soon as any adjustments are completed, QC shall take another sample. If the test results are still outside of the tolerances, production shall stop. Further adjustments or revisions shall be made until acceptable test results are obtained. At this time, production can resume. The cold feed percentages can be adjusted by a maximum of ±5.0% from the JMF. Aggregate from different formations or from different ledges within the same formation can be adjusted by a maximum of ±2.0%. Adjustments in the cold feed percentages greater than ±5.0% require a new JMF. Construction and Materials must be notified of any change in the cold feed percentages from the JMF.
Retained Samples (Sec 401.8.3)
The contractor is required to retain a split (of proper testing size) of all samples for a minimum of 7 days. This includes binder content samples, virgin aggregate and RAP gradation samples, and cores.
Pavement Testing (Sec 401.8.4)
See Density Samples in Paving Operations.
A daily sample, consisting of 4 cores taken at stratified random locations, will be used to determine the mat density. The production area is divided into 4 equal increments and a random number is generated for each increment. Joint samples will consist of 4 cores taken within 6 in. of the joint and from alternating sides of the joint. Shoulder joint samples may consist of 2 to 4 cores taken on the traveled way side of the joint. A random number can be selected for each joint core or a random number can be selected for the first joint core and the remaining cores in the sample can be located by moving down the mat some distance. The distance between the joint cores should be equal. In lieu of coring all joints, a shoulder joint sample can be taken from the shoulder side of the traveled way. If this sample meets the density requirements (90.0%) and no changes are made to the roller pattern, mix composition, or mix temperatures during production, the remainder of the joint coring may be waived with approval from the Resident Engineer. QA will determine the locations of all cores. QC will perform the testing on all cores. The specific gravity of the sample can be determined as a whole, or the specific gravity of each core can be determined and the results averaged. If there is any reason to suspect that density is not being achieved, the inspector should have more cores taken within these guidelines.
Density Adjustment (Sec 401.8.5)
For mix placed at or below the minimum required density, payment will be adjusted in accordance with the table in Standard Specification Sec 401.8.5. Use the following table for pay adjustments due to longitudinal joint density.
| Field Density Percent of Maximum Theoretical Density | Percent of Contract Unit
Price |
|---|---|
| 89.5 or above | 100% |
| 89.0 to 89.4, inclusive | 97% |
| 88.5 to 88.9, inclusive | 94% |
| 88.0 to 88.4, inclusive | 90% |
| 87.5 to 87.9, inclusive | 80% |
| Below 87.5 | Remove and Replace |
The lower percent of the contract unit price of either the pavement or joint density adjustment will be used to determine pay.
401.2.8 Quality Assurance (Sec 401.9)
When production exceeds 500 tons per day, QA will independently sample and test the mix for the combined aggregate gradation and the binder content at a minimum of once per day. A favorable comparison will be considered when the QA test is within the tolerances given in #401.2.4 Gradation Control (Sec 401.5) above. A split of the contractor’s sample will be tested at a minimum of once every 5 days. The split sample tolerances are given in the following table:
| Property | Tolerance |
|---|---|
| All sieves above the #200 | ±5.0% |
| #200 sieve | ±2.0% |
| Binder Content | ±0.5% |
| Density | ≥92.0% |
If the results of the split sample are not within these tolerances, a sample will be taken jointly with QC and tested. QC and QA will each test a split of the sample. If the results of the joint sample are not within these tolerances, production shall stop until the conflict is resolved. If the results of the joint sample are within these tolerances, production may continue. All QA test results will be furnished to the contractor within 24 hours of sampling.
401.2.9 Defective Mixture (Sec 401.11)
See Material Acceptance in Paving Operations
401.2.10 Method of Measurement (Sec 401.13)
Measurement will be in accordance with Standard Specification Section 403.22.
401.2.11 Basis of Payment (Sec 401.14)
The accepted quantities of PMBB and PMBP mix will be paid for at the contract unit price. The contract unit price is set up as total mix (mineral aggregate and asphalt binder are no longer paid for separately). Cores will be paid for as a sample (usually 4 cores).
401.3 Materials Inspection
401.3.1 Scope
Ingredients for use in plant mix bituminous pavement are to be inspected in accordance with the applicable sections of this Manual. Trial mix aggregate samples shall be submitted in accordance with 1001 General Requirements for Materials. Plant calibrations, if requested, shall be performed in accordance with 106.4 Calibration.
401.3.2 Procedure
Mix design procedures are identical to those shown in 403 Asphaltic Concrete Pavement except that the Gmm from the JMF is used for calculation of roadway density. If the Gmm from the JMF does not appear to be representative of the mixture being produced, the Gmm should be determined in accordance with AASHTO T 209. If it becomes necessary to calculate a mix, the formulae, procedure and reporting shall be performed as described in Section 403 Laboratory Testing Guide of the Materials Manual.