Category:401 Bituminous Base and Pavement

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AC Price Index Adjustments
Guidance for Asphalt Cement Price Index Adjustments

Contents

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 AADT is less than or equal to 3500. Such a substitution should be limited and requires approval by the District Construction and Materials Engineer. A PMBB mixture cannot be placed in lifts of less than 3 in. (75 mm). Mineral aggregate-gradation requirements are set forth in the standard specifications. An approved commercial mixture may be used in lieu of PMBB mixtures for minor roads with low traffic in accordance with guidance in Thickness Determination 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 minor road pavements, resurfacing or contract leveling projects. Guidance for using PMBP mixes are given in EPG 450 Bituminous Pavement Design. 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, for normal applications, it is recommended to use 4 in. (100 mm) of PMBB. An SP125 mixture should not be used in lieu of a PMBP mixture, unless approved by the District Construction and Materials Engineer. An approved commercial mixture may be used in lieu of PMBP mixtures for minor roads with low traffic in accordance with guidance in Thickness Determination 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 in. BP-1
  • 1 ¾ in. BP-1 over 2 in. BP-1
  • 1 ¾ in. BP-1 over 3 in. or greater PMBB

401.2 Construction Inspection for Sec 401

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. See also Reclaimed Asphalt Pavement (RAP)

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. The cold feed and hot feed settings may be adjusted by the contractor in the field, provided that the mixture is checked for compliance with;

1) Sec 401.2.2 concerning the contribution from recycled materials,
2) Sec 401.4.4.1 ensuring that the minimum VMA and VFA are maintained with the corrected Gsb and
3) Sec 401.4.4.2 concerning non-carbonate material if using a NC mix.

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 tolerances shown below. QC should determine the gradation of the RAP, if used, at a minimum of onceevery 10,000 tons, in order 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 ToleranceAction
# 8 sieve ±5.0% ± 10.0%
# 200 sieve ±2.0% ± 4.0%
Binder Content ±0.3%-0.3% to +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 Reclaimed Asphalt Pavement (RAP) 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)

See Bituminous Mixing Plants.

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 quantities. 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 8 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 if no deficient cores are found in the first 25 percent of production 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 shall be determined by coring. 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 a, deleterious content, or asphalt content test result falls outside of the specification tolerances, a review or adjustment of the plant settings and production shall be made and another sample shall be immediately taken. If the second test falls outside of the specification tolerances, production shall be immediately ceased until the mixture can be brought back into specification. If a gradation test falls between the Tolerance and Action Limits, adjustments to plant shall be made and another gradation shall be taken immediately. Plant production for the following day shall not resume until the mixture is brought back into specification when the final gradation for the day is not within tolerance. If a gradation test falls outside the Action Limit, production shall cease until the mixture is brought back into specification. 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 random number can be selected for each mat 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. A mat core sould be taken for each 500 tons of production in order to determine acceptance of the inplace material. A joint core should be taken along with the mat core, particularly during the first quarter of the production. If no deficient joint cores are found, meaning all joint densities are found to be above 90%, in the first 25 percent of production the established rolling procedure may be used at the direction of the Resident Engineer in lieu of joint density tests provided no changes in the material, typical location or temperatures are made. The joint core shall be centered at an offset of 6 inches from the longitutinal joint, and be taken from the same transverse cross section, generally meaning the same station or logmile, as the mat core. QA will determine the locations of all cores. QC will perform the testing on all cores. The specific gravity of the joint cores can be determined as a whole, or the specific gravity of each joint 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)

QA will independently sample and test the mix for the combined aggregate gradation, deleterious content and binder content at a frequency of 1 per every 4 QC samples. A favorable comparison will be considered when the QA test is within the tolerances given in Gradation Control (Sec 401.5) above. An independent QA sample of each fraction will be procured during the first week of production to determine the plasticity index (PI) on the fine fraction passing the #30 sieve. A PI greater than 2 percentage points above the value shown on the mix design will require tensile strength ratio (TSR) testing in accordance with Sec 401.4.5. If the PI is within 2 percentage points of the mix design no other QA PI testing will be required during the project.

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. The engineer will retain one half of the plasticity index test and moisture susceptibility test for 7 days after testing is complete. All QA test results will be furnished to the contractor within 24 hours of sampling, with the exception of TSR testing.

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 for Sec 401

401.3.1 Scope

Ingredients for use in plant mix bituminous pavement are to be inspected in accordance with the applicable sections of the EPG. Trial mix aggregate samples shall be submitted in accordance with EPG 1001 General Requirements for Material. Plant calibrations, if requested, shall be performed in accordance with EPG 106.4 Plant Inspections.

401.3.2 Procedure

Mix design procedures are identical to those shown in 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 EPG 403.3 Laboratory Procedures for Sec 403.

401.4 Laboratory Procedures for Sec 401 Plant Mix Bituminous Pavement

This guidance establishes procedures for Laboratory testing and reporting of plant mix bituminous pavement trial mixtures.

401.4.1 Procedures

Trial mixture test results and calculations required for plant mix bituminous pavement will be determined as shown in Laboratory Procedures for Sec 403. No field compacted density samples are required.

401.4.2 Sample Record

The sample record shall be completed in SiteManager, as described in Automation Sec. Test results shall be reported on the appropriate templates under the Tests tab.

401.5 Laboratory Procedures for Sec 401 Plant Mix Bituminous Base

401.5.1 Scope

To establish procedures for Laboratory testing and reporting of plant mix bituminous base trial mixtures and field compacted density samples.

401.5.2 Procedure

401.5.2.1 Trial Mixtures

Test results and calculations required for plant mix bituminous base trial mixtures are as shown in paragraphs 1 through 7 below. Test results and calculations are to be recorded on work Forms "Trial Mix Batch Sheet", "Asphaltic Concrete Trial Mix", and "Immersion-Compression Tests".

1. Compressive strength of bituminous mixtures shall be determined according to AASHTO T 167.

2. When requested, the effect of water on cohesion of compacted bituminous mixtures shall be determined, according to AASHTO T 283.

3. Specific gravity of Laboratory compacted samples (d) shall be determined according to AASHTO T 166.

4. Theoretical maximum specific gravity (D) shall be calculated as follows:

D = \frac{100 + Percent\;Asphalt\;Cement}{A+B+C}
Where:
A=\frac{Percent\;of\;trial\;mix\;aggregate\;A\;in\;mix}{Combined\;specific\;gravity\;of\;trial\;mix\;aggregate\;A}


B=\frac{Percent\;of\;trial\;mix\;aggregate\;B\;in\;mix}{Combined\;specific\;gravity\;of\;trial\;mix\;aggregate\;B}


C=\frac{Percent\;of\;asphalt\;cement\;in\;mix}{Specific\;gravity\;of\;asphalt\;cement}


5. Percent of voids of the mixture (V) shall be calculated as follows:


V=\frac{D-d}{D}\times100


6. Percent voids in mineral aggregate (VMA) shall be calculated as follows:


VMA=\frac{D_1-d_1}{D_1}\times100


Where:
Dl = Theoretical maximum specific gravity of aggregate in a voidless mixture
=\frac{100}{A+B}
dl = Specific Gravity of Compacted Aggregate
=\frac{d}{\frac{100+Percent\;Asphalt\;Cement}{100}}


=d\times\frac{100}{100 + Percent\;Asphalt\;Cement}


7. Percent aggregate voids filled with asphalt cement (VFAC) shall be calculated as follows:


VFAC=\frac{(VMA - V)\times100}{VMA}


401.5.2.2 Field Compacted Density Samples

Samples, as submitted from the field, may be routine or Independent Assurance Samples. Tests and calculations shall consist of specific gravity and percent compaction. Test results and calculations shall be recorded on work Forms "Asphaltic Concrete (Field Sample)" and "Report of Tests on Sample of Bituminous Base".

1. Specific gravity of the field compacted sample shall be determined in accordance with AASHTO T166 except cores, when submitted, shall be tested as one sample rather than individually.

2. Percent compaction of the compacted sample shall be calculated as follows:

Percent Compaction=\frac{Specific\;gravity\;of\;sample}{d}\times100
Where:
d=Specific gravity of Laboratory compacted trial mix sample as in number 3 under Trial Mixtures above.

401.5.3 Sample Record

401.5.3.1 Trial Mixtures

The sample record shall be completed in SiteManager, as described in Automation Sec, and shall indicate acceptance, qualified acceptance, or rejection. Appropriate remarks, as described in EPG 106.20 Reporting, are to be included in the remarks to clarify conditions of acceptance or rejection. Test results shall be reported on the appropriate templates under the Tests tab.

401.5.3.2 Field Compacted Density Samples

The sample record shall be completed in SiteManager, as described in Automation Sec, and shall include a notation in the remarks, "Material submitted for the determinations indicated". Test results shall be reported on the appropriate templates under the Tests tab.

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