Difference between revisions of "505 - Chip Seals"

Revision as of 16:02, 26 March 2026

505 Chip seal

GENERAL DESCRIPTION

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Chip sealing is a common preventive maintenance activity across the State of Michigan. It involves spraying asphalt cement on the surface of an existing pavement followed by the application of a cover aggregate. The asphalt cement is emulsified (suspended in water) to allow for it to be applied without the addition of extreme heat. The cover aggregate is typically either naturally occurring gravel or crushed aggregate such as granite, quartzite, or trap rock (basalt), or limestone. Steel blast furnace slag is also used with great success.

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 ==[[#EQUIPMENT|'''EQUIPMENT''']]==
+===[[#Asphalt Distributor|Asphalt Distributor]]===
+Asphalt Distributor - the role of the asphalt distributor is to apply the binder uniformly and in specified quantities. The distributor consists of a truck- or trailer-mounted insulated tank ranging in capacity from 800 to 5,500 gallons (3,000-20,800 liters).
+Distributors must be equipped with a heating system that will maintain the binder at the proper spraying temperature and has a system of spray bars with nozzles that apply the binder to the roadway surface.  These spray bars cover widths up to 30 feet (10 meters) in one pass.
+The major components of a distributor are:
+*Asphalt tank - a distributor can consist of a truck- or trailer-mounted insulated tank ranging in capacity from 800 to 5,500 gallons (3,000-20,800 liters).  The tank should also have baffle or surge plates to stabilize the load while in motion.
+*Heating system - the tank should have one or two propane or diesel fired burners that direct heat into flues that pass through the tank. This allows the contents of the tank to be heated to the correct application temperature. A thermometer must be mounted in the side of the tank so that the correct temperature can be observed.
+*Circulating and pumping system - the asphalt pump, radar, control valve and strainer are important parts of the circulating and pumping system.  These parts must be checked to ensure they are set properly and there are no leaks.
+*Spray bar and nozzles - ensure that the spray bar is at the correct height and that the proper sized nozzles are installed and at the correct angle.
+*Distributor controls and gauges - the distributor operator must be familar with the following controls and gauges to ensure that a uniform and precise amount of asphalt binder is applied onto the roadway.  They include: thermometer, volume gauge, strap stick pump pressure; and the control panel.
+Aggregate Spreader - the role of the aggregate spreader is to apply a uniform aggregate cover at a specified rate over the freshly sprayed binder. Aggregate spreaders must be self propelled and have a continuous feed feature. The major components of the aggregate spreader are:
+*Truck Hitch - visual check for anything broken or bent.  Ensure the locking mechanism is working properly.
+*Receiving Hopper - the role of the receiving hopper is to receive the aggregate from the haul truck. The receiving hopper must be visually checked for overall condition.
+**There should not be any holes or significant gaps that would allow aggregate to fall through to the road surface;
+**The conveyor belt system should have rubber, neoprene, or fabric cowling around it to prevent aggregate loss; and
+**There must be a flap on top of the receiving hopper to ensure tight fit against haul trucks as aggregate is being dumped into the receiving hopper.
+**A rubber shield prevents aggregate from piling up on the belt, being carried ahead of the receiving hopper and being spilled onto the ground. The rubber shield must be inspected to ensure it is not torn or missing.
+*Conveyor Belts - check to ensure they are in good condition and not frayed enough to allow aggregate to spill over the sides onto the roadway. Check to ensure belts are tight.  Excessive amount of slack will cause sagging and loss of aggregate off the sides.
+*Spreading Hopper - ensure the spreading hopper has no cracks or holes.
+*Discharge Gates and Roller - ensure that the discharge gates open and close correctly and that the roller is not warped.
+{{top}}
+Rollers - the functions of the roller are to:
+•	Orient the aggregate to their flattest side
+•	Embed the aggregate into the binder
+•	Achieve mechanical interlock between the pieces of aggregate.
+MDOT requires the use of three rollers on chip seal projects.
+Sweeping Equipment - the functions of the sweeping equipment are to:
+•	Clean the existing roadway of dust and/or foreign materials before chip seal construction
+•	Removing excess aggregate from constructed chip seals
+There are three different types of sweeping equipment typically used in chip seal construction:
+.	Rotary Brooms - the commonly used type of broom on chip seal construction projects.  The downward pressure must be kept to a minimum to not dislodge the embedded aggregate.  The brush must be inspected to see that it can be raised/lowered and rotated horizontally.  Rotary brooms do generate dust, which can affect visibility for traffic.
+.	Pickup sweepers - generally used wherever dust must be minimized and it is desirable to remove all excess aggregate from the project limits.  A pickup sweeper features a broom that sweeps the aggregate to a suction head that deposits the material in a storage tank. Pickup sweepers are particularly useful in urban areas where aggregate accumulation in gutters or along the edge of the roadway is undesirable.
+.	Vacuum sweepers -  equipment that removes the excess aggregate through suction only. The lack of contact with the chip seal’s surface minimizes damage.
 <span style="color: red"> -Reserved- </span>

Difference between revisions of "505 - Chip Seals"

Revision as of 16:02, 26 March 2026

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