 This videotape will focus on single and multiple surface treatments. A single surface treatment consists of a layer of asphalt being sprayed over a prepared surface, and then a layer of aggregate being spread immediately over the asphalt. A multiple surface treatment repeats this process two or more times as needed. Surface treatments can be used to repair road surface defects such as pavement where aggregate has begun to loosen. Area cracks less than three millimeters wide, small holes, and slippery pavement surfaces caused by smooth, polished aggregate. Surface treatments can also be used to upgrade unpaved roads as well as paved roads, preventing further water damage to the road base. All single and multiple surface treatments will always make the roads safer by providing a skid resistant surface. At least one week to ten days before you start the surface treatments, prepare the surface to be treated by filling area cracks and repairing potholes and other depressions. Also, check the weather forecast. It must be hot and dry during this operation and for several days after it is completed. Dry weather will promote adhesion between the asphalt and aggregate. You will need the proper equipment in good working order, which includes an asphalt distributor for spraying asphalt. Make several test runs to determine the proper asphalt application for this operation. You will also need a mechanical sweeper, a front end loader to place aggregate on the dump trucks, enough dump trucks to haul aggregate to the work site, a mechanical or self-propelled aggregate spreader to place the aggregate over the asphalt. Take shovels and a lute to correct irregularities left by the spreader and a rubber-tired roller to compact the aggregate. To make a strong, long-lasting surface treatment, you will need two types of asphalt. The first type is a low-viscosity asphalt cutback to prime a granular base. The second type is a high-viscosity asphalt cutback, asphalt emulsion or asphalt cement to surface existing pavement or a granular base which has already been primed. The asphalt cutback can be rapid or medium curing. You will also need medium gravel aggregate, approximately 12 mm in size for the bottom layer of double surface treatments, and fine gravel aggregate, approximately 6 mm in size for the top layer. All aggregate must be clean and dry. We will now look at the eight basic steps for this operation. Step 1. Place the traffic control devices. Step 2. Clean the surface area. Step 3. Apply the asphalt. Step 4. Spread the aggregate. Step 5. Compact the aggregate. Step 6. Place additional layers for multiple surface treatments. Step 7. Sweep off loose aggregate. Step 8. Remove the traffic control devices. We will now look at each step more closely. Step 1. Place the traffic control devices. Follow correct procedures for proper placement of signs, cones and barricades. They are important for everyone's safety. If this repair reduces two lanes of traffic traveling in opposite directions to one open lane, you will need flagmen to direct traffic. For further instruction, refer to the IRF videotape traffic control during maintenance. Step 2. Clean the area. Sweep the area immediately before the asphalt is to be sprayed. Angle the broom so the dust will blow away from the area. The broom should extend about 30 centimeters beyond the edge of the pavement. Make sure the surface is clean and dry before you apply the asphalt. Step 3. Apply the asphalt. Before you start, make sure the nozzles are clean and set at the angle specified by the manufacturer. Also, set the spray bar height according to the manufacturer's specifications. Check with your maintenance engineer for the proper application rate before you start. To guide the asphalt distributor, place a string line or markers along the edge. Make sure they are placed about 60 centimeters beyond the outside edge to be sprayed. If the new surface treatment is over a granular base, prime this base one day before the surface treatment is applied. This allows the asphalt to penetrate as deep as possible, bond loose surface particles, fill small holes, waterproof and harden the base, and provide good adhesion between the base and surface treatment. Before you start spraying the asphalt, let us show you how to set up the spraying limits graphically. Place heavy paper at the beginning and end limits to obtain straight and sharp transverse joints. Make sure you have enough asphalt and aggregate to cover the road surface between the beginning and end limits in one pass. Apply the asphalt at the rate specified by the engineer. Start spraying on the paper to obtain a uniform application rate by the time the asphalt is sprayed over the road surface. If several runs are needed to cover the entire width of the roadway, make the runs for each layer in the same direction and overlap them approximately 20 centimeters. After each run, it is very important to adjust the spray bar height to maintain the same application rate. Step 4. Spread the aggregate. Use mechanical spreaders attached to each dump truck or self-propelled models. Spread the aggregate in a single layer immediately after the asphalt has been applied. Leave a 20 centimeter strip of asphalt uncovered along the inside edge for overlapping the next adjacent application of asphalt. It is important to maintain an even application of aggregate. Be sure to add small amounts of aggregate to areas which did not receive enough material. Remove any excess aggregate from the pavement. Step 5. Compact the aggregate. Use a rubber-tired roller because its tires force the aggregate firmly into the asphalt without crushing the particles. If you do not have a rubber-tired roller, use a tandem steel-wheeled roller, but the results will not be as good. Roll immediately after the aggregate is spread and before the asphalt hardens. Start at the edge of the pavement for the first pass, then slightly overlap each additional pass one-third the width of the roller. Continue rolling until the aggregate has become well embedded into the asphalt and a uniform surface has been obtained. To protect the new surface, limit traffic until sunset. Then place warning signs for reduced driving speed until the next morning. Step 6. Place additional layers for multiple surface treatments. Apply asphalt, spread aggregate and roll it as described in steps 3, 4 and 5. Allow at least one day for proper curing between each layer of surface treatment. Operate the asphalt distributor in the opposite direction used for the previous layer. This will correct too much or too little asphalt being sprayed over the same road surface. Also, reduce the application rate for the asphalt as determined by the engineer. Spread the aggregate in the same direction used for the asphalt binder. The aggregate should be one-half the size of aggregate used in the previous layer. Step 7. Sweep off loose aggregate. Use the mechanical sweeper to remove any loose aggregate. The best time to sweep is early the next day after the asphalt has hardened. Loose aggregate is a safety hazard to vehicles and people. Step 8. Remove the traffic control devices. Pick them up in the reverse order of their placement. This completes the operation. Remember, there are eight steps. Step 1. Place the traffic control devices. Be sure the signs, cones and barricades are placed correctly. Step 2. Clean the surface area. Sweep debris away from the area to be repaired. Step 3. Apply the asphalt. Be sure the application is uniform and complies with rates specified by the engineer. Step 4. Spread the aggregate. Place it in an even layer immediately after the asphalt has been applied. Step 5. Compact the aggregate. Continue until the aggregate has become well embedded into the asphalt. Step 6. Place additional layers for multiple surface treatments. Reduce the application rate and the size of the aggregate for each additional layer. Step 7. Sweep off loose aggregate. Do this after the asphalt has hardened. Step 8. Remove the traffic control devices. Pick them up in the reverse order of their placement. This major operation requires proper planning and coordination. You must closely coordinate this work with your maintenance supervisor or maintenance engineer several times during this operation. Also, your instructions to the workers must be clearly understood. Surface treatments provide a smoother riding surface and extend the useful life of the road. Your carefully coordinated efforts will help make surface treatments last a long time.