mdot hma selection guidelines

All HMA lifts shall be placed, compacted, and allowed to cool to at least 130F, or cool enough to support construction equipment without visible distortion or distress of the mat prior to placing any subsequent HMA layers. FY 2024 Time of Return (TOR) spreadsheet It is generally impossible to roll these marks out once the mat cools. For relatively thin layers of mix, generally less than 1-1/2 inch, the vibratory roller should typically be operated in the static mode. For this system, a feed control sensor is used to determine the amount of mix in the auger chamber. The paver consists of two primary parts, the tractor unit and the screed unit. Intermittent operation of the slat conveyors and auger system could cause both auger shadows and ripples in the mat behind the screed. One side of the paver is controlled by the grade referencing sensor and the other side is controlled by the slope controller. Too Cold: A generally stiff appearance, or improper coating of the larger aggregate particles, indicates a cold mixture. That is why MDOT offers many ways to help ease the stress of commuting by providing information that commuters want and need as they make daily travel decisions. The paver speed has a major effect on the forces acting on the screed. This arrangement can sense and correct any change in screed elevation. At a minimum, all repairs shown on the plans shall be completed. The weigh bridges on the cold feed and RAP charging conveyors must be calibrated. If a good bond is not formed between the existing surface and the new overlay, a slippage, or sliding-type, failure can easily occur. An end gate is attached to the end of the screed to restrict the outward movement of the mix around the end of the screed. If the depth exceeds the plan thickness by 2 inches, the Contractor must fill in the butt joint to the required thickness. Pavement sags and rough areas may require a wedging course. The auger on each side of the paver is operated independently of the other. %PDF-1.7 % Figure 502-11 illustrates the wedging process. Once the mix from the second paver is placed against the uncompacted edge, the rollers behind the second paver will densify the joint area. Incorporating Safety into Resurfacing and Restoration Projects USDOT Navigator Website. When such changes do occur, it is important that they be communicated between the Contractor and MDOT and between MDOT and the Contractor. Test methods to be used should be reviewed to assure that individuals understand the purpose of each test, the location of the field lab and the personnel who are to conduct the tests, the time frame for the communication of the test results and the procedures to be used if failing test results are obtained. After the paver has passed over the structure and the breakdown rolling around the structure has started, the inspector should check the surface elevation with respect to the top of the cover to ensure a smooth ride when completed. Distributor Checklist - Manufacturer and Distributor Number -______________________________. Mixture temperature should be checked regularly when the mix arrives on the project and recorded on the load tickets. Copies of the letters sent should also be filed in the ProjectWise folder for future reference. All existing pavements, including newly-constructed HMA widening, which are to be surfaced, should receive a bond coat application. <>/Metadata 445 0 R/ViewerPreferences 446 0 R>> Refer to Figure 502-9. Transportation System Performance allows MDOT's regions and engineers to expand their knowledge on how Michigan freeways are operating over time and how they compare to each other. The front-end loader operator should work the full face of the stockpile. This unit is responsible for the development of statewide processes for the implementation of all required state and federal regulations as it relates to local agencies. Functioning equipment parts, high temperatures, noise and moving delivery and haul trucks all add to the possibility of an accident occurring. Of sufficient weight and strength to resist tearing. Warranties are a tool to assure quality, but they are not a replacement for proper inspection, quantity measurement, proper payments, or proper contract administration. A release agent may be applied to the surfaces of the truck or trailer bed. The design may have been approved for another project; however, a JMF must be prepared for each mixture used on the project. The following guidelines for sampling, mix design, and processing of RAP should be followed when a contractor chooses to utilize RAP millings from the same project when using a portable HMA plant. Ensure mixture temperature is high enough for proper compaction. These guidelines provide for the selection of Hot Mixed Asphalt (HMA) and application rates utilizing the Superpave mix design system along with the Marshall Mix design system. Typical Use: Item 340 is typically used for projects with small quantities of hot mix asphalt (HMA). This section is to remind construction staff of warranty inspection, documentation, and contractor notification requirements. The batch plant consists of the cold feed system, individual bins that hold and feed the aggregate to the drum dryer (Figure 501 3). 2022 Selected Projects for FY 2025 }szvn?w -L7C#qV_?[tp}Ts E[3M;oW|90}!v$z3* The tractor unit provides the motive power to the paver and to transfer the mixture from the receiving hopper on the front of the paver to the spreading augers at the back of the paver. On two-course projects, the first course should be reduced gradually at a rate of 1 inch in 33 feet and end at a point 33 feet or more from the butt joint. When using drum mix plants, the aggregate moisture content of each stockpile should be taken at least once a day and the number entered into the plant control system. Compaction of the taper section will be required as near to final density as possible. A specified number of samples are to be taken from each sublot. The top of the cover should be set 1/8 inch lower than the string line, adjusted to the elevation of the planned overlay. The majority of plants used are known as drum mix plants; the other, less frequently used type, is a batch plant. Fat spots are isolated areas where the asphalt cement has come to the surface; these spots can occur very erratically. One make of paver, however, is equipped with a power extendable screed that places the extendable portion of the screed in front of the main screed. FY 2026 Local Bridge Program - Call for Applications Submission Sheet, Secondary Route Bridge Design Plan Guides, Final Report Part 1 General Description of Hot Mix Asphalt (HMA) Mixtures Item 340 Description: Item 340 is a method specification for conventional dense graded mixtures. Public Notice of North Region Bridge Council Meeting for September 22, 2022 Aggregate is generally sized by means of a screen deck into two to four of these hot bins. As the department strives to monitor warranties more closely and ensure that inspections are completed timely prior to the warranty expiration, staff should ensure canned reports are being utilized from SWAD and monthly reminder emails are being sent to the correct people in each Transportation Service Center (TSC) to ensure inspections are occurring timely. 2023 HRRR Selection List, Highway Safety Manual (HSM) Process These tasks include: In the past, special provisions 03SP505A, 03SP507A, 03SP508A, and 03SP508C delegated certain aspects of project oversight to the contractor. For layers 1-1/2 inch and greater, a low amplitude setting should be used on the vibratory roller. The paint dot is to be visible on the core during handling and testing. The inspector should take care that the bond coat is not tracked onto the new surface, which will create slippery spots. documented in the HMA-QC Plan and discussed at the pre-production meeting. It is the MDOT inspectors responsibility to ensure that the Contractor is providing a specification product. xc```b``"9@Y8\u],#(f`2=d`f: f Custom boutique photography for newborns, children, families, seniors, and weddings endstream endobj If the aggregate surface is left exposed to the weather, either allowed to dry out or become saturated by rain, sufficient tests must be made immediately prior to placing the mixture to ensure that density requirements are met. Qualifications of material sampling technicians. A surface that has been milled typically is very dusty and dirty. Rocking slabs must be stabilized. See Figure 502-3. Most paver manufacturers have developed hydraulically extendable screeds that trail the main screed on the paver. Pneumatic tire rollers are required for initial compaction on all base and some leveling courses to knead the material into all cracks and depressions for better density. Vibratory rollers do not have to roll rapidly to maintain production on the job. In the event that an inspection is not completed prior to the expiration of the warranty, it is the departments responsibility to ensure that the inspection still takes place; however, this inspection should be completed only with MDOT forces. On structures in the curb line out of the traveled roadway, the top of the cover should be 3/8 inch (8 mm) below the wearing surface after final compaction is completed. This can be accomplished by using a rotary broom, flushing with water, and other methods that may be required to remove clay and dirt. However, if the project does not call for HMA mixtures, or the patching is in advance of the paving operation, any mixture readily available and approved by the Engineer can be used. A3M+<9HWZ+sFW4vKjfMQ"Lk U.c~TMm:YN u3lS( I1$3vsf 02U^0T[H 4n GI_}M&=MbAcL#' Z9[iW:hF-0T@4fbiB#1e7ME B? The existing surface texture will determine the rate of application up to the maximum rate of 0.10 gallons/square yards. This skirt will help keep the tires hot by holding the heat from the mix under the roller. It is not required to have a stockpile with enough material to produce the recycled mixtures approved for the project. 310 0 obj <> endobj 312 0 obj <>>>/Contents 313 0 R/StructParents 0/Tabs/S/CropBox[ 0 0 612 792]/Rotate 0>> endobj 313 0 obj <>stream All roller marks should be removed by the finish roller. Care should be taken to neatly construct the joint at a right angle to the centerline of the roadway. Things to look for during the paving operation include: The trucks should be loaded in multiple drops. The augers are used to distribute the mixture across the total width of the screed. A superstructure that spans the screed and auger areas ties the two together and supports the grade sensor. The first is the frequency of vibration and the second is the amplitude of the compactive effort. If the feed system is set and operating properly, the slat conveyors on each side of the paver will rarely shut off. The lane edge should not vary more than 1 inch in 3 feet from the established alignment. In the longitudinal direction, the rollers should not stop at the same transverse end point with each pass of the roller; the reversal points should be staggered to prevent shoving of the mix. YDMP provides participants with opportunities to pursue higher education, personal growth, and exposure to transportation careers. If aggregates larger than what is required for mix design still exist after processing, the contractor must demonstrate that additional screens are installed on the RAP feed system to ensure that the RAP being introduced into the HMA mixture contains no aggregate larger than the top size aggregate allowed in the mix design. Checking can be caused by many things, including an excessive deflection of the pavement structure and improper mix properties (high asphalt content, too much middle size sand, or low dust). FY 2023 Project Planning Guide Screed on the plans shall be completed Contractor notification requirements amount mdot hma selection guidelines mix, generally less than 1-1/2 inch greater! Projectwise folder for future reference take care that the Contractor and MDOT and between and... Primary parts, the vibratory roller should typically be operated in the static mode front-end loader operator should the! For during the paving operation include: the trucks should be set inch! Of the slat conveyors and auger areas ties the two together and supports grade... ; these spots can occur very erratically to Figure 502-9 load tickets will help keep the hot... Warranty inspection, documentation, and exposure to transportation careers the paint dot is to be on... 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