mdot hma selection guidelines
When the basic width of the paver screed needs to be changed to accommodate increased paving widths, rigid or hydraulic screed extensions can be employed. The aggregate used to make the mix can be a single aggregate, but it is generally different sizes blended together through the cold feed bins to produce proper gradation. The desired degree of cross slope is dialed into the slope controller. The primary compaction variables that can be controlled during the rolling process are: number of rollers, type of rollers, roller speed, number of roller passes and roller pattern. (Example: 6 percent grade - 6 inches (6 m) of elevation change in 100 feet (100 m) of horizontal longitudinal run). The Office of Procurement and Contract Management (OPCM) Consultant Services Division (CSD) procures all Maryland Department of Transportation State Highway Administration (MDOT SHA) A/E contracts using Qualifications-Based Selection (QBS), as defined in Code of Maryland Regulations (COMAR) Title 21, Subtitle 12, "Procurement of Architectural Services and Engineering Services" and 23 CFR . This process is typically used for superelevation corrections, placing a wedging course so that the leveling and top courses can be placed at a uniform thickness. Our goal is to keep Michigan's motorists safe, informed, and mobile. The flow gates should be adjusted to provide a uniform head of material in front of the screed. Typical Use: Item 340 is typically used for projects with small quantities of hot mix asphalt (HMA). Qualifications of material sampling technicians. If the mix is tender, a lower tire pressure will displace the mix less than a higher pressure. Refer to the AASHTO Roadside Design Guide and the MDOT SHA Guidelines for Traffic Barrier Placement and End Treatment Design for additional . All personnel involved in the project must be required to comply with all safety standards applicable to the type of construction and asphalt paving work to be carried out. The slat conveyors in the bottom of the hopper should not be visible when the wings are emptied. Is heating system in good working condition? Included are examples of calculations, documentation requirements, and . A scalping screen should be placed in the aggregate cold feed charging system and the RAP feed system to remove any oversize material. Is distributor tachometer working properly? 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. There are four basic types of grade references that can be employed to maintain the elevation of the screed pull point: the erected string line, the mobile mat reference, 30 foot floating ski, and the joint matching shoe. A Contractors payment could range from 105 percent to 50 percent of the bid price; he could be required to remove any sublot, a total lot, or even the total mixture. Additionally, a 301 Moved Permanently error was encountered while trying to use an ErrorDocument to handle the request. It is our goal to improve overall safety for all road users, internal staff, contractors performing work on roads, and emergency responders. 309 0 obj <> endobj Plan the width of application to ensure having bond coat under the matching longitudinal joint. Resources for local governmental agencies that regularly require access to state right of way. Open texture areas in the joint should be filled using the HMA mixture with the large stones removed. The proposal and plans should be reviewed to see if the cold-milling will be for profiling, or for a specified depth. stream Permits and Utility Coordination endobj When the paver stops, do it as fast as possible. Pavement ride quality is affected by all phases of the construction process; to ensure a smooth finished product, good construction practices must be followed throughout the entire paving process. }szvn?w -L7C#qV_?[tp}Ts E[3M;oW|90}!v$z3* The length of the auger extensions should, in general, be the same length as the screed extensions. &[a);8fUcK@=fCW ?Qdo Highway Safety Manual (HSM) Analysis Spreadsheet ]Rt~cv!G(F5@QFJFIN$@>, Phone: 443-572-5045 Fax: 410-787-0483 Email: TDavis5@mdot.maryland.gov Admixtures for Concrete Admixtures for Concrete Product Qualification Procedures (PDF, 200 KB) Qualified Products Air Entraining Agents (PDF, 200 KB) Drycast Admixtures (PDF, 200 KB) Precast Admixture (PDF, 200 KB) Type A - Water Reducing (PDF, 200 KB) 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. The mobile reference system, illustrated in Figure 502-8, combines the front mounted 30 foot floating beam with a 20 foot mat reference beam. This information must be detailed and complete. The temperature should be checked immediately. Be extremely careful when an asphalt surface is being placed on an aggregate base adjoining a slab or curb. Adequate hand tools, and proper equipment for cleaning and heating them, should be available for the paving operation. <>/Metadata 445 0 R/ViewerPreferences 446 0 R>> An asphalt mix that has all the desirable mix design characteristics will perform poorly, if not compacted to the proper density. The importance of staying within the surface tolerance for smoothness cannot be overemphasized. It is composed of several major components including the truck push rollers, the mixture receiving hopper, material flow gates, two slat conveyors and a pair of augers. Changes occur because of material supply, equipment breakdown, Contractor and Subcontractor schedules and weather conditions. Following is a list of things that can cause a rough riding surface: A special provision for pavement ride quality measurement is included in many paving contracts. A sufficient amount of millings or cores shall be taken at each test location to ensure an adequate amount of RAP is obtained to perform a full mix design. These documents help people to design, build, and maintain roads and bridges. 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. The augers must be extended if the screed is extended. Agreement is needed on the methods to be employed to complete the project on schedule, within specification and with minimum delays. If this yield is found to be high or low from that specified on the plans, a slight adjustment of the thickness controls should be made and the yield rechecked. An approved grade referencing attachment, not less than 30 feet in length, may be used. The completed centerline joint should be uniform, closed and flush with adjacent lanes. Fuel oil is not permitted for use on tapered joint rollers and mobile mat reference wheels. 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. x\YoF~A4 M!"Gcy-3_}TA(z #*v}Ow>~_c~y}On}]mvy}Rc*UQ]n/?]v./8:~o?Q`Sv;WE]f_MAuOF}@,c?uQUYcmEEPuB',~WMQsE$XF-,V-g6mMa%[+ndv6>%T&G/fQx&[0{Rm z5WB3^sha!QBk`LB#D1V'iuZtDW}} . Communication is one of the keys to a safe work environment. Whenever a rigid screed extension is employed on the basic screed, auger extensions and the accompanying auger tunnel extensions should also be added. Does the Contractor have proper number of rollers? Adjust catch basins after the leveling course has been placed. Ensure the bond coat has broken before paving starts. The Internship Program offers undergraduate and graduate students interested in civil engineering and construction management careers, valuable experience by working with professional field staff. Plan Approval. Steam rising from the mix as it is dumped into the hopper of the spreader indicates moisture in the mix. The existing surface texture will determine the rate of application up to the maximum rate of 0.10 gallons/square yards. Bleeding can be caused by too much asphalt cement in the mixture, or by allowing traffic onto the paved surface before the surface has cooled sufficiently. It may be necessary for the Contractor to make adjustments of the screed, vibrators, hopper flow gates, or the screed augers, to ensure a uniform surface texture. Are circulating systems working properly? If the random core location falls over a tapered joint, it should be moved to the first point that the mat is full depth. There should be enough trucks to provide a continuous flow of mix to the paver. All nozzles should be turned at the same angle to the spray bar: approximately 30 degrees, depending upon the manufacturers recommendations. This nonuniform texture can be caused by many factors: screed extensions not level with each other, running the hopper empty between trucks, unevenly worn screeds, cold mix, or improperly emptying the paver wings. 26.65 (b) is still subject to the 3-year gross receipts average. Ensure sufficient compaction capacity is available. NEPA Guidance For a stiff mix, a higher tire pressure should be used. One of the greatest contributors to a poor ride on an urban project is the improper adjustment of manholes. 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. Roller Checklist - Manufacturer and Roller Number -______________________________________. See Figure 502-4. Bulletin include test data for all coarse and fine Aggregate used in Maryland Highway construction. The office is responsible for media relations, social media, and website development. 3 0 obj When one truck is emptied, it should pull away from the paver. Never empty the paver hopper while paving. Project mixture and testing Special Provisions. The TSCs are designed to respond to the transportation needs of local communities for the highest level customer service. The use of a tapered, overlapping longitudinal joint eliminates the requirement that all lanes be resurfaced to within one truckload of the same point of ending. This page was last edited on 19 January 2022, at 13:44. Mixture temperature should be checked regularly when the mix arrives on the project and recorded on the load tickets. If the inspector observes the Contractor not providing a specification product, the paving process should be stopped until the Contractor makes the corrections needed before being allowed to continue. The asphalt cement delivery system must be calibrated. The incline of a paving surface in the direction of travel, expressed by stating the rise or fall as a percentage of horizontal distance. endstream endobj Final Report Part 2 The MDOT plant inspector should follow the sampling and testing procedures explained in the Special Provision 20SP501(R) Superpave Hot Mix Asphalt Percent Within Limits (PWL) or 20SP501(S) Superpave Hot Mix Asphalt Percent Within Limits (PWL) For Capital Preventive Maintenance (CPM) Mill & Resurface Projects and CPM One Course Overlay Projects. Any severely spalled areas at joints should be repaired using partial-depth repair methods. 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. At a minimum, the failed areas should be removed and replaced, the potholes properly patched, the cracks cleaned out and the ruts filled, or preferably removed by cold-milling. In addition, the screed imparts a level of compaction with the vibratory action of the screed. The certification is normally completed by the Region Traveling Mixture Inspector (TMI) before the Contractor starts his first project in the spring. See Figure 502-6. Three types of self-propelled rollers are currently being used: static steel wheel, pneumatic tire rollers and vibratory rollers. 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. The batch plant consists of the cold feed system, individual bins that hold and feed the aggregate to the drum dryer (Figure 501 3). MDOT provides technologies and partnerships in order to make the transportation system safer and less congested. Ensure the surface is cleaned of all dust, dirt and other debris. 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. Refer to Figure 502-10. Are the king bolts in good condition on steel wheeled rollers? FY 2024 Safety (HSIP and HRRR) Call Letter A multi-unit culvert is considered a bridge if the total length, as measured along the centerline of the roadway, is greater than 20 feet and the distance between the culvert units is less than half the diameter of the smallest unit. Obviously the higher the frequency, the faster the vibratory compactor may roll. 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. Asphalt cement is the material that holds the aggregate together. Samples shall be taken if visual observations show significant variations in existing pavement mat. Ride Specification provides guidance to using the Pavement Surface Profile. Ensure the paver speed matches mixture delivery. Thus, the samples will be taken at 1985 and 6.3 feet from the beginning of the pavement. Only enough bond coat should be applied that can be covered the same day. Easy method to calculate roller speeds for proper Impact Spacing, VPM / Impacts per foot = feet per minute, 2500 / 10 = 250 fpm, 2500 / 12 = 208 fpm, 2500 / 14 = 179 fpm, fpm x 0.01136 = fpm / 88 = mph, 208 fpm x 0.01136 = 208 fpm / 88 = 2.36 mph. This device consists of a short 12 inch shoe or ski that is used to reference the grade of an adjacent piece of pavement or curb. The inspector should also check the structure to determine that the casting is firmly set in place. Figure 502-11 illustrates the wedging process. It is the Contractors responsibility to ensure that the mixture temperature is adequate for placement and compaction; however, if the inspector observes mixture that is either too cold or too hot, the problem should be pointed out to the Contractor and the Engineer. It is important for the screed extension to be attached securely to the main screed. These are notes from meetings between MDOT SHA and industry about improving the quality of materials used on State highways. Bond coat, also referred to as tack coat, is an asphalt emulsion. Are guards placed on end of spray bar to protect over spray where necessary? Are the water sprinklers in good operating condition? 2 0 obj HMA mixtures consist of a blend of asphalt binder and aggregates mixed in an asphalt plant. Experience has shown that these sections generally settle after a short period of time. Rakes, shovels and lutes are frequently used by personnel around the paver. The final step before the bond coat is applied is to thoroughly clean the existing surface by brooming and/or other methods; all vegetation and debris must be removed from pavement joints and cracks. Typically, the string is supported on metal posts at 25 foot intervals. Attach copies of the qualification documentation for the sampling technician to the preproduction meeting minutes for each HMA paving project where HMA sampling is required. It is also possible to require the Contractor to remove a sublot of leveling course mixture that has already had the top course mixture placed upon it. The elevation of a fresh mat in relation to the base. The roller pattern should be set up as soon as paving starts. The front-end loader operator should work the full face of the stockpile. A vibratory compactor should never exceed a rolling speed that will provide less than one impact of the drum per inch of travel. <> If it is below the specification limit, 250F, it should be discarded. 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. See Figure 502-3. 2024 HRRR Selection List During this meeting, the overall goals and expectations are set for the project. This system spans a distance greater than three wire reference stakes spaced at 25 foot intervals to produce a better average reference and eliminates potential errors inducted into the mat by an improperly maintained wire reference. Be in good condition with no holes or tears. The patch shall be compacted so that the patch is smooth with adjacent pavement. This dryer heats the aggregate to the desired temperature and delivers the material to the hot bins in the tower unit. Roller passes must be distributed uniformly over the width and length of the area being compacted. 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That millions of people visit the Great Lakes State every year careful when asphalt. Be caused by improper operation of the vibratory action of the drum per inch of travel enough coat! The matching longitudinal joint into the hopper should not be visible when the mix less than a higher pressure,. Rc * UQ ] n/ them, should be turned at the same to... Shovels and lutes are frequently used by personnel around the paver stops do... Manufacturers recommendations be repaired using partial-depth repair methods of application to ensure having bond coat has broken paving. Guards placed on an aggregate base adjoining a slab or curb Region Traveling mixture Inspector ( TMI before... The leveling course has been placed uniformly over the width of application up to the maximum rate of 0.10 yards... Vibratory roller course has been placed surface is being placed on an urban project is the adjustment! 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