155 – ASPHALT SURFACING AND ASPHALT RECYCLING EQUIPMENT
150-14 (6) Use of Storage Bins and Batchers. When used with a storage bin, design and operate these plants so the
transfer of HMA from the drum to the storage bin shall not cause segregation of the mix, and the batcher can be operated according to subsection 602.4a.(3)(d) . Equip all storage bins with controls capable of maintaining a specified minimum level or amount of HMA in the bin at all times during production. If the amount of HMA in the bin can be determined by reading the output of load cells or other approved sensors, the Engineer shall specify the minimum amount of material in tons. Otherwise, the minimum level of HMA is the top of the tapered portion of the bin or at the point designated by the Engineer on special designed bins. Set the controls to close and lock the bin gate when the specified minimum amount or level is reached. Override of the lock is permitted only to clean out the bin at the end of a production run. Equip every storage bin with a batcher at the top, located so the HMA is discharged vertically from the batcher into the center of the bin. The Engineer may approve other equipment such as a rotating chute. Do not load the storage bin directly from a belt or other conveyor. Cover the belts carrying HMA to prevent excess heat loss. Establish control of the batcher gates so the batcher shall operate as specified in subsection 602.4a.(3)(d) throughout the output range of the plant. (7) Dust Collectors. Equip the plant with an approved dust collector, bag house or other type of collector that complies with limit particulate emissions standards. Dispose of all waste mate rial in a suitable manner. Equip the plant to prevent particulate leakage.
8.Air Emission Permit. Provide a copy of an Air Emission Permit issued by the Kansas Department of Health and Environment (KDHE) to the Engineer before installing a hot mix plant. It is the Contractor’s responsibility and expense to satisfy the KDHE requirements.
9.Safety Requirements. Provide adequate and sa fe access to sampling points and other locations where checking of plant operations is necessa ry. Thoroughly guard and protect all gears, pulleys, chains, sprockets and other dangerous moving parts. When required by the Engineer, provide access to the top of truck bodies by a platform or other suitable device to enable the En gineer to obtain samples and temperature data.
b.Requirements for Drum Mix Plants.
1.General. Specifically design the plant for drum mixing and to be capable of satisfactorily heating, drying and mixing the HMA. (2) Cold Aggregate Feed System. Use belt scales for positive weight measurement of the combined cold aggregates. Continuously record the am ount of cold aggregate using a non-se t-back recorder. The belt scale shall be accurate within 2% by weight of th e material being measured over any give n period of time. Calibrate the belt scales at intervals as directed by th e Engineer. Provide a weight system automatically coupled with the asphalt flow to maintain the required proportions.
a.Sampling. Provide safe, adequate and conveni ent facilities for obtaining representative samples of the combined cold aggregate. Provide a sampling device capable of producing a sample of proper size (large enough to be representative, but small enough to be carried safely by 2 people) from the full width of the combined aggregate flow, while the plant is operating at regular production rate.
b.Recycled Material Conveyor. If the plant is used for recycling, a weighing system is required to control delivery of virgin aggregate and recycled material components to the drum. Equip the system with interlocking mechanisms that shall accurately deliver virgin aggregates, Reclaimed Asphalt Pavement (RAP) and Recycl ed Asphalt Shingles (RAS) in proper proportions. Belt scales for the RAP and RAS shall comply with subsection 155.6b.(2) .
c.Moisture Compensation. Include a moisture compensation device in the cold feed system to correct for the moisture in the aggr egate passing over the belt scales.
d.Weather Protection. Prot ect belt scales from the effect of wind and weather.
3.Asphalt Material Feed System. Supply asphalt material to the mixing drum through a continuously registering cumulative indicating meter by a pump specifically designed for drum mix plants. Locate the meter in the asphalt material so it shall register the discharge to the drum. Provide a means to divert the flow into a container for calibration. Supply the meter with a non-set-back re gister accurate within 2% by weight of the material measured in any given period of time. The register shall record only material delivered to the drum.
4.Mineral Filler Feed System. Introduce and uniform ly disperse fly ash and similar mineral fillers into the drum mixer at the point of introduction of the asphalt without loss to the dust collector system. Use a non-set-back register to record the quantity of mineral filler disc harged into the mixer. Equip the delivery system with 155 – ASPHALT SURFACING AND ASPHALT RECYCLING EQUIPMENT
150-15 variable speed to interlock with the aggregate weigh belt so the total aggregate weight including the mineral filler is
indicated to the asphalt proportioning system. Provide a device to indicate that mineral filler is being delivered uniformly to the drum that shall activate a visible or audible signal to the plant operator if the flow is reduced or interrupted. (5) Calibration of Feed Systems. Enable easy calibra tion of the aggregate weighing system and the asphalt material meter system. The calibration methods are subj ect to approval by the Engineer, who may require a schematic diagram of the system. (6) Mixing Drum. Equip the drum with automatic burner controls to prevent damage to the aggregate or asphalt material. Keep the discharge temperatur e of the mixture within the range specified in DIVISION 600 for the type of asphalt material being used. Install the activating unit for recording the asphalt mixture temperature in the discharge chute of the drum mixer. Use a rate of flow through the drum such that the aggregate and asphalt material form a homogeneous mixture with all particles unifo rmly coated. Do not exceed th e manufacturer’s rated capacity.
c.Requirements for Hot Mix Batch Plants.
1.Dryer. Include one or more dryers in the plan t that continuously agitate the aggregate during the heating and drying process. Use dryers that dry and heat all aggregate to specified requirements.
2.Aggregate Temperature. Install the actuating un it for recording the aggreg ate temperature where the hot materials flow over it during the proportioning operation.
3.Hot Aggregate Storage Unit. Configure the unit so the aggregate shall not be segregated and can be discharged into the weigh hopper in a manner th at shall not affect the accuracy of weighing.
4.Weigh Box or Hopper. Include a means for acc urately weighing the aggregate in a weigh box or hopper suspended on scales, and of ample size to hold a full batch without running over. The gate shall close tightly so no material is allowed to leak into the mixer while a batch is being weighed.
5.Asphalt Control. The weigh bucket shall be non-tilting with a loose sheet metal cover. Make the length of the discharge opening or spray bar greater than ¾ the length of the mixer, and make it discharge directly into the mixer. Heat the asphalt material bucket, its discharge valv e or valves and spray bar. Provide an asphalt material bucket with a capacity a minimum of 15% in excess of the weight of asphalt material required in any batch. Have a heated quick-acting, non-drip, charging valve located directly over the asphalt material bucket. Locate a scale dial with a capacity of a minimum of 15% in excess of the quantity of asphalt material used in a batch in full view of the mixer operator. Automatically control the flow of asphalt material to begin when the dry mixing period is over, and all of the asphalt material required for one batch shall be discharged in less than 15 seconds after the flow has started. If an approved metering device is used to control the amount of asphalt material, provide a valve and outlet for checking the meter in the sec tion of line between the charging valve and the spray bar.
6.Scales. Scales may be of the beam, spring less dial or electronic type that complies with subsection 152.2 . Equip beam scales with a Tel-Tale dial that shall st art to function when the load being applied is within 100 pounds of that required. The dials shall be compounding , with full complements of index pointers. Do not place dials to give excessive parallax errors. Locate all dials to be plainly visible to the operator at all times. (7) Control of Mixing Time. Equip the mixer: with an accurate time lock to control th e operations of a complete mixing cycle; to lock the weigh box gate after charging the mixer until the mixer gate closes at completion of the cycle; and to lock the asphalt material bucket throughout the dry mixing period and lock the mixer gate throughout the dry and wet mixing periods. The dry mixing period is defined as the interval of time between the opening of the weigh box gate and the start of introduction of asphalt material. The wet mixing period is the interval of time between the start of introduction of asphalt material and the opening of the mixer gate. Perform the setting of time intervals in the presence of the Engineer. The Engineer will then lock the case covering the timing device until such time as a change is to be made in the timing device.
8.Mixer. Use an approved type of batch mixer capable of producing a uniform mixture. If not enclosed, equip the mixer box with a dust hood to prevent loss of dust. The clearance of blades from all fixed or moving part s may not exceed 1 inch, if the maximum size of the aggregate is less or equal to 1 inch. The clearance may not exceed 1 ¼ inches, if the maximum size of the aggregate in the mix exceeds 1 inch. 155 – ASPHALT SURFACING AND ASPHALT RECYCLING EQUIPMENT
150-16 155.7 Self-Propelled Aggregate Spreader
Use a spreader that is supported by a minimum of 4 wheels with pneumatic tires on 2 axles. Equip the spreader with a means of applying the larger cover coat materials to the surface ahead of the smaller cover coat material so that the required amount of material is deposited uniformly over the full width of the asphalt material. 155.8 SURFACE RECYCLE EQUIPMENT
a.Pre-Heating Unit. Use a self-propelled heating unit, adjustable in width, with ports permitting fuel and forced air injection for proper combustion without excessive smoke. The unit shall be under a closed or shielded hood, capable of heating asphalt pavement to a temperature th at allows milling or scarifyi ng to the specified depths. Equip each unit with a water spray system used to wet the adjacent vegetation.
b.Heating Milling Unit. Use a self-propelled unit capable of milling, heating and windrowing the asphalt pavement that is being processed, and meeting subsection 155.8a . In addition, equip this unit with automatic grade controls to mill the desired depth of material to be processed.
c.Heating Scarifying Unit. Use a self-propelled unit capable of heating and scarifying the asphalt pavement that is being processed, and meeting subsection 155.8a .
d.Tunnel Heater. Use a self-propelled unit capable of heating the underlying pavement while shielding the previously milled material from direct flame, prev enting the material from catching on fire and meeting subsection 155.8a . The tunnel heater may be equipp ed with a milling unit. In this case, the tunnel heater shall also meet subsection 155.8b .
e.Distributor-Paving Unit. Use a single unit that uniformly distributes the rejuvenator at the stipulated rate onto the scarified or milled material and mixes them together using a minimum of 2 telescopic milling heads. This equipment also screeds and finishes the scarified or milled material simi lar to an asphalt paver specified in subsection 155.4 .
f.Milling-Mixing-Paving Unit. Use a unit complying with subsection 155.8b . The rejuvenator shall be added uniformly at the stipulated rate onto the scarif ied or milled material and mixed with a minimum of 2 telescopic milling heads. Alternatively, the rejuvenator ma y be added directly to the milling heads provided the applied rate is uniform across the width of the HIR materi al. This equipment shall also screed and finish the scarified or milled material similar to an asphalt paver specified in subsection 155.4 . Alternatively, a self propelled independent paver complying with the asphalt paver specification in subsection 155.4 may be used after the mixing operation. 155.9 COLD RECYCLED ASPHALT PAVEMENT EQUIPMENT (LIME SLURRY/FLY ASH)
a.General. Provide a self-propelled machine capable of cutting and removing the asphalt pavement (to the dimensions specified in the Contract Documents) in one pass. Equip the cutting machine with automatic controls capable of maintaining a unif orm grade and cross slope. Equip to pulverize the reclaimed asphalt pavement (RAP) material to specified requirements without contamination from the subgrade material. The RAP material processing unit shall consist of a closed loop system with a crusher and a scalper screen, or other approved devices capable of reducing the RA P material to the specified gradation. Provide the mixing unit with a continuous weighing system for the processed RAP material, and be coupled with meters to maintain the proper proportion of RAP mate rial, liquid binder, set retarder (used only with fly ash) and water. Meter all water (including water added by the milling machine) introduced into the mix. If delivery of RAP material is stopped, automatically shut off the liquid binder, set retarder (used only with fly ash) and water pumps. Provide positive means for calibrating the weight measurement device and the additive metering devices. Apply the additives in a mixing chamber that is capable of mixing the pulverized pavement material and additive to a homogeneous mixture. Equip the additive syst em to maintain the binder amount within plus or minus 0.2% of the specified application rate an d to shut off automatically if delivery of RAP material is stopped. Place the mixture in a windrow or load it into trucks so segregation does not occur. 155 – ASPHALT SURFACING AND ASPHALT RECYCLING EQUIPMENT
150-17 Place the recycled mixture without segregation usi ng a self-propelled aspha lt paver complying with
subsection 155.4 . If a pick-up machine is used to feed the windrow into the paver hopper, provide one capable of picking up the entire windrow down to the underlying materials. Provide self-propelled vibratory steel and pneumatic rollers to establish the rolling procedure. The vibratory steel roller may also be used as a static steel roller.
b.Lime Slurry. Equip the milling chamber with spray bars to incorporate hydrated lime slurry and water into the RAP. The metering device for the spray bars is calibrated to, and controlled by the continuous weighing system for the RAP. Provide slaking equipment specifically manufactured for th is purpose. Equip transport, tank trucks or trailers with mechanical agitators.
c.Fly Ash. Provide equipment to introduce set retarder and water into the mix independent of one another. 155.10 HOT POUR CRACK SEALANT EQUIPMENT Provide a machine used for pouring cracks, capable of mixing the asphalt and rubber or other specified material in the specified proportions into a homogeneous mi xture at the specified temper atures. Use a double boiler melter with a permanently attached temp erature gauge to continuously verify sealant temperature in the material tank. Do not use units with a solvent flush system for clean out, due to the risk of solvent contamination to the sealant. Use a melter with a heat chamber for hose storage and valve heating, or an air flush system to eliminate the need for a solvent flush clean-up system. Provide material tank mixing with a reversible paddle agitator in a vertical tank configuration. Use units similar to those purchased by KDOT Maintenance under Spec: MS 168, latest version. 155.11 MODIFIED SLURRY SEAL EQUIPMENT
a.Mixing Equipment. Use a self-propelled mixing machine capable of delivering and proportioning the aggregate, mineral filler, water, additives and emulsifi ed asphalt to a revolving multi-blade dual mixer, and discharging the thoroughly mixed product. Provide storage capacity for all components to maintain a supply in the proportioning controls. Operate the machine continuously while loading, to eliminate unnecessary construction joints. Provide individual volume or weight controls for proportioning each material to be added to the mix. Calibrate and properly mark each material control devi ce. Provide controls accessible for ready calibration and placed so the Engineer may determine the am ount of each material used at any time. Equip the mixing machine with a water pressure sy stem and nozzle spray bar to provide a water spray immediately ahead of and outside the spreader box as required. Equip the machine with opposite side driving stations to optimize longitudinal alignment. Equip the machine to allow the mix operator to have full control of the forward and reverse speed during application of the material.
b.Spreading Equipment. Equip the machine with opposite side dr iving stations to optimize longitudinal alignment. Configure the machine to allow the mix operator to have full control of the forward and reverse speed during application of the material. Spread the paving mixture uniformly by means of a mechanical laydown box attached to the mixer and equipped with paddles to agitate and spread the materials th rough the box. Design and operate the paddles so all the fresh mix shall be agitated to prevent the mixture from setting up in the box or causing side buildup and lumps. Flexible seals in the front and rear shall be in contac t with the road to prevent loss of mixture from the box. Equip the box with lateral movement controls. The rear flexible strike-off shall be adjustable. Rut filling equipment requires adjustable steel strike-off plates. De sign and operate the spreader box and rear strike-off so a uniform consistency is achieved to produce a free flow of material to the rear strike-off without causing skips, lumps or tears in the finished surface. When directed by the Engin eer, provide a secondary strike-o ff to improve surface texture. Use a secondary strike-off with the same adjustments as the rear flexible strike-off. Spread the mixture to fill cracks and minor surface irregularities and leav e a uniform application of slurry on the surface. When directed by the Engineer, provide a secondary strike-off to improve surface texture. The secondary strike-off shall have the same adjustments as the rear flexible strike-off. Operate the spreader to prevent the loss of the paving mixture when surfacing super-elevated curves. Keep the box clean and free of build up of asphalt and aggregate.
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 110–113 of 978.