mdot hma selection guidelines

**If in line crushing and/or screening is being used 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 a RAP scalper screen may not be required. Roller passes must be distributed uniformly over the width and length of the area being compacted. }szvn?w -L7C#qV_?[tp}Ts E[3M;oW|90}!v$z3* Refer to Figure 502-9. Flexible Pavement: When rigid extensions are being used in conjunction with the main screed, the crown can usually be altered at any of the points where the extensions are joined. This section provides the mix design guidelines for Marshall and Superpave HMA mixtures for use on MDOT projects. 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. Plan Approval. 309 0 obj <> endobj The grade sensor usually rides directly on the beam at its midpoint. Pavement Type Selection Process; Ride Specification . Regional Bridge Councils Contact Information There are many common myths and misconceptions about transportation in Michigan. Grey goos vodka - Der Gewinner . Samples shall be taken if visual observations show significant variations in existing pavement mat. Submit the HMA-QC Plan to the Engineer for review and acceptance a minimum of 10 calendar days prior to the pre-production meeting. The weigh bridges on the cold feed and RAP charging conveyors must be calibrated. Public Notice of Bay Region Bridge Council Meeting for October 3, 2022 To exceed this one impact or more per inch of travel may produce small ripples in the mat when laying HMA. A vibratory compactor should never exceed a rolling speed that will provide less than one impact of the drum per inch of travel. This page was last edited on 19 January 2022, at 13:44. Ensure sufficient compaction capacity is available. Before overlaying the old pavement, it should be inspected. Sampling frequency required is based on the percentage/tonnage of RAP that will be utilized on the project. Rollers are used to compact the mixture to the required density. It is very important to know what special provisions are contained in the proposal. Aggregate is generally sized by means of a screen deck into two to four of these hot bins. Can speed be locked in on vibratory rollers? When the inspector sees an improper bond coat application, the operation should be stopped. 2022 Selected Projects for FY 2025 Determine the length of one pavement representing a sublot of material, the width of the pavement and the number of samples, (n), needed for each sublot. The aggregate base must provide a firm foundation before paving commences. This is a certified product and the suppliers must be on the Certified Products List. Breakdowns and bad weather can create problems with large areas of bond coat that are left unsurfaced. Depending on the material and job conditions, this can be quite dramatic. Plan the width of application to ensure having bond coat under the matching longitudinal joint. Yield = 93920 pounds/561.33 square yards= 167.3 lbs/square yard. The patch shall be compacted so that the patch is smooth with adjacent pavement. Mixture types to be used and the sampling and testing procedures vary depending on the specifications used. This article returns the responsibility for these tasks to MDOT for all concrete paving projects, including those that contain special provisions 03SP602A and/or 03SP602E. 115 0 obj <<4c7790beb010dcdd18f2ce7848bb2f38>]>>stream Projects constructed under a warranty special provision still require inspection staffing and complete documentation prior to payment, including MDOT materials certifications, MDOT yield checks, MDOT quantity measurement, and MDOT Inspectors Daily Reports. It is generally the responsibility of the Engineer to outline the scope of the project and to discuss the information provided in the contract documents. The office is responsible for media relations, social media, and website development. Vegetation and debris should be removed from joints and cracks. If distortion of the base course occurs during the paving operation, the mixture placement should be stopped until the condition of the base course is corrected. At a minimum, all repairs shown on the plans shall be completed. The bond coat material shall be applied ahead of the paving operation for a distance of at least 1500 feet, depending upon traffic conditions, as determined by the Engineer. As the first load of mixture is being spread, the texture of the unrolled surface should be checked to determine uniformity. Further, the extension must be set at the same elevation and angle as the basic screed to prevent the presence of a transition line, or ridge, at the intersection of the main screed and the extension. Long and short waves can be caused by a fluctuating head of material in front of the screed. See Figure 502-2. {7:r!> -)t=:NuL5oqba5q]oe`0jC A mean average is thus obtained over the entire span. The rollers vibratory frequency should match its travel speed. Fuel oil is not permitted for use on tapered joint rollers and mobile mat reference wheels. Are circulating systems working properly? These are notes from meetings between MDOT SHA and industry about improving the quality of materials used on State highways. The roller pattern should be set up as soon as paving starts. Keeping the hopper at least half full between truckloads of mix keeps the head of mix in front of the screed constant and this will reduce mat problems. Functioning equipment parts, high temperatures, noise and moving delivery and haul trucks all add to the possibility of an accident occurring. The top size of the top scalping screen shall be 1.5 for top and leveling courses and 2 for base courses. If the extensions on the extendable portion of the screed are not properly aligned with the main screed, a longitudinal mark, or ridge, will occur in the surface of the mix at the junction between the two screeds. The Contractors representative should be familiar with the project and be able to speak with authority about what is to be accomplished. If two pavers running in echelon are used, the construction of the joint is similar to the building of a joint against a cold compacted pavement. A properly heated screed, particularly at the start of the days paving operations, or after any extended shutdown of the paving process, provides a more uniform mat surface texture. This article returns the responsibility for these tasks to MDOT for all HMA paving projects, including those that contain special provisions 03SP502D and/or 03SP502E. A rule of thumb is that the proper level of air voids should be obtained before the mixture cools to a temperature of 176F. To reach the required density, the quickest initial compaction should occur directly behind the lay down machine. Two factors within the screed itself can contribute to the degree of compaction. Maintain and document these certifications in the project files. endobj The incline of a paving surface in the direction of travel, expressed by stating the rise or fall as a percentage of horizontal distance. Very short waves, or a washboard effect, can be caused by improper operation of the vibratory roller. %PDF-1.7 The tractor unit receives the asphalt mixture from the haul trucks, carries that mixture back to the spreading augers, distributes the mixture across the width of the screed and pulls the screed over that mixture. At MDOT, safety is paramount. Forms Everyone, regardless of title or job function, must be aware of the need for safe work practices. Secondary Route Bridge Design Plan Guides The tire pressure used depends, in part, upon the number of plies used in the tires. The top course will then be placed at a uniform rate. The base surface (road bed) over which paving is being performed. FY 2023 Project Planning Guide FY 2024 Time of Return (TOR) spreadsheet Does paver have properly working screed heaters? Does the paver have reverse pitch augers or paddles at center of paver? The screed is continually attempting to keep in balance all the forces acting on it. MDOT should not rely on the contractors daily report for quantities or as a replacement for the MDOT Inspectors Daily Report. Again, the temperature should be checked immediately. As the layer thickness increases, it may help to increase the amplitude applied to the mix as recommended by the manufacturer. This section serves to provide guidance for utilizing Reclaimed Asphalt Pavement (RAP) millings from the same project when using a portable Hot Mix Asphalt (HMA) plant. A list of MDOT personnel who will be assigned to the project should be provided to the Contractor. 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. Advisories Communication cannot stop once the pre-production meeting is concluded. 4643 0 obj <>stream The JMF is prepared and signed by the TMI. If the wedging course is 3 inches or less, the inspector should string line the area to be wedged to determine the limits of wedging. Once the truck bed has been emptied of mix, the truck hitch is withdrawn and the truck is able to pull away from the paver. Hand raking and shaping around the cover must be completed before the material cools. Real Estate Guidance The finished mat should be smooth and free of blemishes. The mix may also foam so that it appears to have too much asphalt. This type of reference device is used only when the grade being sensed is relatively smooth. Slow and steady is the key to good vibratory compaction procedures. All existing pavements, including newly-constructed HMA surfaces, which are to be surfaced with HMA, will receive a bond coat application. 2.5 HMA or WMA, HT (19 mm MIXTURE) Polymer Modified (1 @ 2.5) 3 HMA or WMA, HT (19 mm MIXTURE) (1 @ 3) 6 Lime Fly Ash Treated Granular Material (9/C) 13.5 Structure Thickness 6 Chemically Treated Subgrade 7 Shoulder Granular Material (5/C) Multiple lifts of 9.5 mm HMA/WMA should be avoided. Further, whenever rigid extensions are employed, the strike off, or pre-strike off, assembly must be added to the extension and set at the same location as the strike off on the main screed. See Figure 502-4. The faster the paver moves, the less time the screed sits over any particular point in the new mat, thus the amount of compactive effort applied by the screed decreases. Be extremely careful when an asphalt surface is being placed on an aggregate base adjoining a slab or curb. Pressure distributors are used to apply a uniform application of the asphalt emulsions, normally referred to as the tack or bond coat. The auger and the slat conveyor on the same side must be operated together. For this system, a feed control sensor is used to determine the amount of mix in the auger chamber. @c0M8;\ r)]-f3E|r ZVu~[ The Contractor must provide all equipment required to prepare the base and place the HMA in accordance with the plans and specifications. Another type of grade referencing device is the joint matching shoe. In addition, the spray bar should be set at the proper height above the pavement surface to provide for a double or triple lap of the liquid asphalt materials. Once the proper yield has been obtained, only periodic checks will be required each day. Adjustments to the JMF will not be allowed outside the mixture limits shown in Tables 501-1 and 501-2 of the Standard Specifications for Construction. Samples to be taken a minimum of every mile in each lane by milling or coring. It is the Contractors responsibility to obtain the proper pavement density. Nonuniform mixing shows up as spots of lean, brown, and dull appearing material within areas of rich and shiny appearance. See Figure 502-3. The outcome of each conversation must be recorded; who told whom to do what, and what was the reply? If the automatic controls are being used, the screed operator should not try to change the screed manually by turning the thickness control crank. While the paver is operating, laborers may work, or rework, a portion of the mix to fit the paving around objects and to fill in areas that the paver does not pave adequately, or cannot reach. Excess Moisture. The paver screed is a leveling device attached to the tractor unit at only one point on each side of the paver; it is able to float on the asphalt mixture and to provide initial mat texture and compaction to the material as it passes over it. 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