Russian Engineers Workshop Russian Engineers Training March 2011 Russian Engineers Workshop HMA Delivery Delivery is the start of the HMA construction process. Like any process, if it is planned properly, it will go smoothly. The smoother the process, the better the product. The key elements of this module are presented (in detail) under Section 13: “Mix Delivery” of the Hot-Mix Asphalt Paving Handbook 2000, pp. 115-121. HMA Delivery

Russian Engineers Training March 2011 Learning Objectives Discuss key issues related to haul trucks Describe proper truck operation (loading and unloading) techniques Present the five primary learning objectives of this module. The theme to this module is looking at HMA construction as a process, and how keeping the process running smoothly lessens problems and improves the product. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 HMA Delivery What is the objective? Truck drivers are a key component,… Make them a part of the team! Have the participants identify what the objective of HMA delivery is by asking questions such as: Are we just trying to pick up and deliver a material from point A to point B? Do we care how long it takes to deliver the material? Do we care what condition the material is in when we deliver it? 2. Ultimately, the objective we are looking for is one that involves picking up and delivering the HMA material in a timely fashion without seriously affecting its desirable properties (i.e., temperature uniformity and aggregate gradation). 3. Drivers must be made part of the paving team from the beginning. They should understand their role and purpose in the team. Safety is paramount around the jobsite. Drivers must act responsibly, and adequate traffic control must be available to ensure safe passage. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 General Rules – Mix delivered to the screed must be a free flowing homogeneous mass in which there is no segregation, crusts, lumps, or migration of the asphalt rubber If not then the Engineer will order the work to stop and may require: Covering the trucks Changes to plant mechanical parts Use of Materials Transfer Vehicle or remixing device HMA Delivery HMA Delivery

Three Basic Types of Haul Trucks Russian Engineers Training March 2011 Three Basic Types of Haul Trucks End dump Belly (bottom) dump Horizontal discharge There are 3 primary types of HMA haul trucks. Each is loaded at the plant in the same manner from the silo or pug mill. The difference is in how they unload the mix at the paver. HMA Delivery HMA Delivery

Standard End Dump Truck Russian Engineers Training March 2011 Standard End Dump Truck Capacity: 11-18 Mg (12-20 tons) 3 to 6 axles Advantage: Maneuverability Disadvantage: Limited capacity Shown here are the basic characteristics, advantages and disadvantages of the standard end dump truck. Note: This slide provides answers to one of the questions at the end of the module. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 End Dump Trucks Standard Shown here are two types of end dump trucks, the standard “10 wheeler” and a typical tractor semi-trailer. Semi-trailer HMA Delivery HMA Delivery

Semi-trailer End Dump Truck Russian Engineers Training March 2011 Semi-trailer End Dump Truck Capacity: 18-23 Mg (20-25 tons) 5 to 6 axles Advantage: Capacity Disadvantages: Overhead clearance Poor maneuverability Potential conflicts with paver Shown here are the basic characteristics, advantages and disadvantages of the semi-trailer end dump truck. The photo inset highlights one of its disadvantages during operation. HMA Delivery HMA Delivery

Double Trailer Combinations Russian Engineers Training March 2011 Double Trailer Combinations Double trailer combinations are used in some locations. Must drop the pup to discharge the second load. Ask: What types of trucks are used here for hauling HMA? HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Belly Dump Truck Capacity: 18-23 Mg (20-25 tons) Advantages: Capacity No contact with paver Disadvantages: Requires attention to sizing the windrow Need for windrow elevator Potential for aggregate segregation Shown here are the basic characteristics, advantages and disadvantages of the typical belly dump truck. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Belly Dump Truck The belly (or bottom) dump truck drops HMA in a windrow just ahead of the paver. A separate device (windrow elevator or pick-up machine) is used to pick up and load the HMA into the paver hopper. HMA Delivery HMA Delivery

Horizontal Discharge Truck Russian Engineers Training March 2011 Horizontal Discharge Truck Capacity: 18-45 Mg (20-50 tons) 5+ axles Advantages Capacity Limited segregation during unloading Disadvantages Poor maneuverability Availability Shown here are the basic characteristics, advantages and disadvantages of the horizontal discharge truck. HMA Delivery HMA Delivery

Horizontal Discharge Truck Russian Engineers Training March 2011 Horizontal Discharge Truck Horizontal discharge (or live bottom) truck. Shown here is the “Michigan Special” with a capacity upwards of 45 Mg (50 tons) Conveyor belt or slat conveyor discharges mix from back, without raising bed, directly into paver. HMA Delivery HMA Delivery

Horizontal Discharge Conveyor Russian Engineers Training March 2011 Horizontal Discharge Conveyor Conveyor moves mix out the back end, directly into the paver hopper. HMA Delivery HMA Delivery

Tarp for Protection Against Heat Loss and Inclement Weather Russian Engineers Training March 2011 Tarp for Protection Against Heat Loss and Inclement Weather Are there any potential problems with this tarp configuration? Haul trucks should be equipped with tarps as they protect the mix during inclement weather and help retain heat. Tarps should be water-repellent, resist tearing, without holes. Mechanically extendable tarps are preferred (to keep the driver off the side of the truck). Note that some tarps (such as the one shown in this photo) can do more to create temperature segregation than retaining heat. If they do not completely cover the bed, they can funnel air into the mix as the truck travels down the road. Ask: What are local requirements for tarps? Must have? Used when? HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Side Insulation Where necessary, insulation should be added to keep the mix hot. Insulation should be tight against the truck body, with no gaps. HMA Delivery HMA Delivery

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Transportation Guidelines Russian Engineers Training March 2011 Transportation Guidelines Truck Beds Must Be Kept Clean - Modified Mixes tend to Stick More Than Conventional Mixes in the Hauling Unit - Use an Approved Release Agent Trucks Loaded Properly to Minimize Segregation Some basic “Rules of the Road!” for the Truck Drivers. There are many different types of hauling units used today. Tandem, dump trailers, horizontal discharge, bottom dump and pups (trailers). Each must be kept clean, use devices to retain the specified temperature and operated properly if we are to accomplish our stated mission. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Keep Truck Bed Clean The haul truck bed should be kept clean and free of deleterious materials. Also, the bed should be smooth and free from major dents or depressions where release agent and HMA can accumulate. HMA Delivery

Use Only Approved Release Agents Russian Engineers Training March 2011 Use Only Approved Release Agents Non-petroleum materials sprayed uniformly on the sides and bottom–just enough to coat the bed without runoff. Diesel fuel can cause problems with the mix, and is hazardous to the environment. Ask: What type of release agents are normally used locally? Note: This slide provides an answer to a later question. HMA Delivery HMA Delivery

Keep Outside of Bed Clean Too Russian Engineers Training March 2011 Keep Outside of Bed Clean Too The outside of the truck should also be kept clean and free of extraneous materials. Look for loose rock and dirt near the truck’s tail lights. Ask: Why is exterior cleaning necessary? There are two primary reasons: 1) debris can shake loose and break a windshield and 2) excess mix can drop in front of the paver and affect the quality of the mix. HMA Delivery HMA Delivery

Truck Loading Practices Russian Engineers Training March 2011 Truck Loading Practices Next we are going to look at truck loading practices. This photo shows silo gates discharging mix into the truck. This subject may seem to be fairly simple, but improper loading is a prime source for mix segregation. Proper loading can help eliminate a segregation problem. The loading plan should be discussed and agreed upon at the preconstruction conference. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 WANT TO AVOID THIS ! HMA Delivery HMA Delivery

REDUCE THE DISTANCE THE COARSE AGGREGATE CAN ROLL Russian Engineers Training March 2011 REDUCE THE DISTANCE THE COARSE AGGREGATE CAN ROLL HMA Delivery

Russian Engineers Training March 2011 Batchers drop a large mass of material at one time to reduce segregation. Batchers, or “gob hoppers” minimize segregation by dropping the mix into the silo in one mass. This is a proven equipment technique that reduces the tendency of the mix to segregate. HMA Delivery HMA Delivery

Best Management Practices Storage Silos Russian Engineers Training March 2011 Best Management Practices Storage Silos To reduce the opportunity for segregation: Feed all batchers in center and in-line with splitter if fitted with splitter Adjust timer-style batchers for full discharge (varies with production rate) Adjust close timers to leave some material in batcher on closing Follow proper truck loadout procedures The reduce the possibility of segregation, the following best management practices are universally accepted. Feed all batchers in center. Feed split-feed type batcher in-line with splitter. Adjust timer-style batchers for a full batch with each discharge. On these style batchers, the “open” timer must be changed with the production rate. Adjust “close” timers to leave some material in batcher on closing. All batchers are equipped with “close” timers. These are the timers that close the batcher gates after it initiates an “open” cycle. Follow recommended truck loadout procedures. HMA Delivery HMA Delivery

Must Avoid Segregation! Russian Engineers Training March 2011 Must Avoid Segregation! The segregation shown here in the hopper can pass through he paver and end up in the mat. The segregation seen here resulted from a segregated load. HMA Delivery

Russian Engineers Training March 2011 Single Dump Front & Rear Segregation Here is a prime example of HMA being allowed to “Break and Run!” As the HMA cascades from the discharge point to the front and rear of the truck bed, the larger aggregate flushes to the surface and accumulates and will stay in this segregated mass unless it is corrected it will show up in the pavement as “Load to Load Segregation.” Single Dump Loading HMA Delivery HMA Delivery

Segregation in Corners & Pockets Russian Engineers Training March 2011 Segregation in Corners & Pockets Large Aggregate Accumulation Another picture of “Break and Run” in the hopper of a machine being charged by a pick up machine. Segregated HMA has accumulated in the corner of the hopper ready to slide into the paving mainstream and continue under the screed as streaks. HMA Delivery HMA Delivery

Proper Loading Techniques Russian Engineers Training March 2011 Proper Loading Techniques Use Multi Dump Loading Procedures For Sensitive Mixes! When the mix design you use is sensitive toward segregation you should take every precaution to minimize segregation. The multi dump method will help in most instances. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Third Dump First Dump Second Dump Multidump Truck loading procedures minimizes the distance the material can break and run during the loading process. The first dump is made either at the front or rear of the hauling unit. The second dump is then made at the opposite end with the third and final dump made in the center of the truck bed. Multidump Truck Loading Procedures HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Minimize Segregation in Corners Third Dump First Dump Second Dump Looking from the top you can see how we have minimized the distance the HMA can break and run on the first two dumps. The bulkhead at the front and tailgate to the rear. The the final drop completes the loading process and again the break and run distance is held to a minimum and reduces the chance of segregation at both front and rear of the hauling unit. Should your hauling unit be long enough to require more than three drops divide it equaling and load each truck accordingly. Multi Dump Loading Procedures Minimizing Toward the Center HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Simple Solution When Loading Trucks Wood Board Paint Line (First Dump) Paint Line (Third Dump) Paint Line (Second Dump) An inexpensive way of taking the guess work out of loading your hauling units is to incorporate the use of a wooden board of sufficient length to mark each of the dumping position for the hauling units being loaded. Attach the board to the superstructure of the plant aligned with the truck rear view mirror and paint a mark where each dump is to be made. Every truck that is of the same demonstrations can align their mirror making the same drops. Each load can be loaded fairly identical using this process. Should the various trucks have different lengths use a different color of paint indicating how they should load their individual trucks. Longer trucks or trailers make first and second drop and fill in the remaining with equally spaced drops or drop and pull through the balance of the loads. Board to be of Sufficient Length to Fasten Along Side the Truck on the Silo Structure. Position the Board so the Rear View Mirrors of the Truck Align at Each Position for Dumping. (Different Trucks Use Different Colors.) HMA Delivery

Other Loading Practices to Avoid Russian Engineers Training March 2011 Other Loading Practices to Avoid Topping off Overloading Plant operators may want to top-off the truck to legal limits to reduce haul costs, especially if truck is sitting on the scale under the silo. While good economics, it should not occur by dribbling mix into a nearly full truck. Discharging small amounts of mix into the truck greatly increases the chance for mix segregation. Overloading is not recommended as it is illegal and dangerous. Modern electronic scales and printed tickets have helped eliminate this practice. HMA Delivery HMA Delivery

Russian Engineers Training March 2011 The Rules Care must be taken to avoid jarring the paving machine No vertical load shall be exerted Trucks, when dumping shall be securely attached to paving machine When a windrow paving operation is used it shall not be dumped at a distance greater than 150 feet in front of paving machine HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Mix Delivery Sequence If trucking is balanced and the drivers are experienced… Paver should rarely stop for any extended periods Trucks should flow in and out of paver Mat quality should improve. Rollers will operate in a steady fashion. The following sequence of slides shows a typical delivery sequence of trucks interacting with the paver. HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Positioning in front of paver This slide is the first in a series that describes the unloading sequence for a standard end dump truck operation. They may be used as a setup for a video clip that shows the unloading operation in real time. Positioning the truck in front of the paver: The truck brakes to a halt in front of paver, ready to be picked up on the fly. It is important that the truck be centered on the paver before the paver makes contact. Damage to the mat and the paver can result from off-center positioning. The area between the truck and paver is off limits to personnel. Too many accidents occur in this area. Ask: Has anyone ever had a close call? (If so, possibly have them relate the story.) HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Once the truck has stopped, the driver releases the brakes and the paver “picks up” the stopped truck. In this photo, the truck is also beginning to lift the bed. The key is that the truck does not back into the paver and bump it. Bumping the paver can leave a screed mark and roughen the mat. Once the paver picks up the truck, it pushes the truck forward. A light touch on the brakes keep the truck against the paver. Ask: What should happen before the tailgate is released? First contact with paver,… avoid bump! HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation With end dump trucks, the proper procedure for dumping the mix into the hopper is to raise the truck bed slightly and allow the mix to slide against the tailgate before it is released. This procedure will allow the mix to flood the hopper–not allowing mix to dribble from the truck into the hopper before the bed is raised. Raise bed, but keep tailgate closed until mix slides against it HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation After the hopper is filled, the truck bed is gradually raised, continually charging the hopper and maintaining a smooth operation. Open gate and continue to raise bed HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Empty mix in one smooth, continuous discharge What are baffles for? As the truck empties, the driver follows signals from the dump signaler to raise the bed and discharge all of the mix. This truck has baffles just inside the tailgate. Ask: Why? Direct mix to the middle of the hopper. Force mix from the trucks sides to the middle. Ultimately–to help reduce segregation. HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Once the truck is empty, the bed has to be lowered before pulling away. Lowering the bed will allow the truck apron to clear the hopper guards and avoid ‘bumping” the paver. Note: This slide provides an answer to a later question. Lower bed before pulling away HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Aside from catching the paver hopper, another problem with not lowering the truck bed before pulling away is spilling mix onto the paving surface. Any practice that spills mix onto the paving surface should be discouraged. Note: This slide provides one of the answers to a later question. Problem with pulling away with bed up HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Once the truck has cleared the paver, it should immediately depart from the area to a clean up station, and let the next truck back up. Emphasize the continuous nature of the exchanges, another truck waiting as the finished one departs. Move out and make room HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation There should be a designated clean up area for the drivers to clean any remaining mix from the rear of the truck, the apron, and the tailgate. The clean up area is not the paving site. Again, modified asphalt can make this a more troublesome task. Proceed to the designated clean-up area HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation Ever have to shovel 1.8 Mg (2 tons) of mix out in front of the paver because the truck driver didn’t keep his foot on the brake? What is the truck driver’s penance? What happened here? HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation “Banging the gate” (leaving the truck bed up, speeding up, and then stopping quickly to allow the tail gate to bang the truck) should be discouraged. What probably caused this? HMA Delivery HMA Delivery

End Dump Truck Operation Russian Engineers Training March 2011 End Dump Truck Operation If this does occur, the mix must be cleaned off the surface, not just paved over. Ask: What could happen if this mix is allowed to stay on the pavement? Why can’t this be paved over? HMA Delivery HMA Delivery

Material Transfer Vehicle Russian Engineers Training March 2011 Material Transfer Vehicle Aggregate segregation can also be minimized through the use of MTVs. Essentially a rolling surge bin, MTVs receive the mix from the trucks, and then feed the paver. This vehicle allows the paver to be operated almost continuously, as long as the mix is coming continuously from the plant. This equipment also eliminates the exchange between the truck and paver, preventing any truck bumping or braking problems. Truck dumps into MTV (rather than paver) HMA Delivery HMA Delivery

Material Transfer Vehicle Russian Engineers Training March 2011 Material Transfer Vehicle MTV conveys mix into surge bin inserted into paver hopper On the other end of the material transfer vehicle, a conveyor discharges mix into the paver hopper. Note the oversized hopper insert used with this equipment. Ask: Who has used a material transfer vehicle? Good experiences? Types of projects? HMA Delivery HMA Delivery

Tips from Best Practice Russian Engineers Training March 2011 Tips from Best Practice Truck bed should be free of all contaminants Insulation should be used if required Truck should be loaded in multiple drops Truck should be equipped with a tarpaulin that is in good condition; without tears and holes. Should be large enough to cover the bed and wrap over the sides and end of truck HMA Delivery HMA Delivery

Tips from Best Practice (cont) Russian Engineers Training March 2011 Tips from Best Practice (cont) End dump and live bottom trucks shold stop short of the paver and allow the machine to pick up the truck. The bed on an end dump truck should be raised a short distance and mix allowed to slide against the tailgate before the tailgate is opened HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Questions – does it all make sense? HMA Delivery HMA Delivery

Russian Engineers Training March 2011 Summary HMA Delivery HMA Delivery 54

Russian Engineers Training March 2011 www.ncat.us HMA Delivery 55 HMA Delivery 55