 This videotape will focus on base and sub-base repair. This repair must be performed when water has thoroughly saturated the road base. Surface repairs alone will not correct a road base weakened by saturation. The entire part of the damaged pavement structure must then be replaced. These weakened areas can be located by critical surface defects, such as soft, spongy areas and severe area cracks in the pavement, and many potholes in a small area. Water enters the wide cracks in the surface, saturating the layers. Before starting this repair, the maintenance supervisor or engineer must inspect the work site to determine how to prevent further water damage to the base and sub-base. For this repair, you will need the proper equipment to do the job correctly. You will need an air compressor with the appropriate tools to cut the pavement. A motor grater or tractor with a scarifier attachment to break up the pavement over the weakened road base. A front-end loader to remove the damaged pavement surface, base, sub-base and sub-grade. Dump trucks to haul materials to and from the work site. A water truck to carry water needed for the repair to the work site. A rubber-tired roller, a vibratory roller or a tandem steel-wheeled roller to compact the material. An asphalt distributor and an aggregate spreader for replacing the wearing surface of a surface treatment pavement or an asphalt paver for replacing asphalt concrete pavement. And brooms and shovels to clean up loose aggregate at the work site. You will also need the proper materials to make a successful base and sub-base repair. You will need granular base material, which has been properly graded. Low-viscosity liquid asphalt cutback to prime the granular base. High-viscosity liquid asphalt cutback, rapid or medium curing, or asphalt emulsion for a surface treatment pavement. Hot by 2-minus concrete mixture for an asphalt concrete pavement. And water to assure proper moisture for the granular base material. The water source should be adequate and near the work site. We can now look at nine steps for base and sub-base repair. Step one, place the traffic control devices. Step two, mark the limits of repair and cut the pavement. Step three, remove all unsuitable material. Step four, install any required sub-drainage. Step five, restore the sub-grade. Step six, replace the base. Step seven, replace the pavement surface. Step eight, clean the work site. Step nine, remove the traffic control devices. We will now look at each step in more detail. Step one, place the traffic control devices. If the work site extends beyond the driver's view, you will need several flagmen to control one-way traffic. If it takes more than one day to complete the repair, make sure the signs will be quickly visible to motorists at night. For further information, refer to the IRF videotape traffic control during maintenance. Also, safeguard your equipment during non-working hours. Follow your approved procedures to protect the equipment. Step two, mark the limits of repair and cut the pavement. Examine the area immediately adjacent to the defect and determine where the pavement surface is supported by a firm base. Use chalk, paint, or markers to identify the limit of the repair. The repair limit must be in the area of firm pavement. Make sure the marks are straight and perpendicular across the road. Next, use the pavement cutting tool to cut the pavement along the mark. Make sure the cut is straight and vertical. Step three, remove all unsuitable material. This includes damaged pavement and weakened base, sub-base, and sub-grade. To begin, scarify the damaged pavement within one meter of the marked limit. Be careful not to damage good pavement. Remove the damaged pavement, then load it into the dump trucks. You must check with your engineer to see if the broken pavement should be saved for future use or properly discarded away from the road and drainage ditches. Next, remove all weakened base and sub-base. If the sub-grade has been saturated, remove it as well. When you reach a firm bottom, make it level before you proceed to the following steps. Step four, install any required sub-drainage. The maintenance supervisor or engineer will determine if sub-drainage is required and specify the type to be used. Sub-drainage will help prevent the base and sub-base from becoming weakened by saturation again. When installing sub-drainage, follow the engineer's instructions. Step five, restore the sub-grade. Make sure you use approved material for the sub-grade that is the same quality as existing sub-grade. Restore the sub-grade to its original line and grade before the pavement structure is replaced. Spread the sub-grade in a loose layer about 20 centimeters thick. This is about the same distance as from the tip of your finger to your wrist. Test its moisture content. Squeeze a sample in your hand. If it crumbles, it is too dry. Water must then be added to increase the moisture of the sub-grade material. If the sample remains in a ball, the sub-grade material has the proper moisture. This will help obtain good compaction. If the sample runs out between your fingers when you squeeze, it is too wet. It must be allowed to dry before it is placed. Next, compact the sub-grade material using the rubber-tired roller, a vibratory roller, or a tandem steel-wheeled roller. Additional layers may be needed to bring the sub-grade to its original line and grade. Be sure to fully compact each layer before another layer is added. For repairs covering a large surface area, the surveying team should set control stakes outside the pavement to check the final elevation. Also, your maintenance supervisor or maintenance engineer should test the sub-grade's compaction before the base and sub-base are replaced. Step 6. Replace the base. Spread the approved granular material in loose layers, approximately 20 centimeters thick. Check the moisture of the granular material the same way you checked the sub-grade material. If you have to add water, do not add too much. Excessive moisture will make the base too soft. Next, compact each layer thoroughly. Start at the outside edge of the granular base for the first pass, then overlap each additional pass one-third the width of the roller. Cover the entire surface several times to make sure each layer is well compacted to a thickness of approximately 15 centimeters. Your maintenance supervisor or maintenance engineer should test the compaction of each base layer before the pavement surface is replaced. Make sure the final elevation of the restored granular base is the same as the surrounding granular base. Your maintenance supervisor or engineer should inspect it before you proceed. After the granular base has been approved, prime it with the asphalt cutback at the rate specified by the engineer. Keep traffic off the primed base until it has set properly. Step 7. Replace the pavement surface. For surface treatment, you start by spraying the asphalt, then spread the aggregate evenly and compact each layer. For further information, refer to the IRF videotape, single and multiple surface treatments. If you replace asphalt concrete pavement, you start by placing the bituminous concrete mixture over the surface with an asphalt paver. Then you compact it with a rubber-tired roller and a steel-wield roller or a vibratory roller. For further information, refer to the IRF videotape on overlaying with an asphalt paver. Step 8. Clean the worksite. Sweep the area clean of any loose aggregate and other unwanted debris. Make a record of where the striping needs to be replaced. Then notify your maintenance supervisor so it can be scheduled. Step 9. Remove the traffic control devices. Pick them up in the reverse order of their placement. Refer to your approved procedures. Also, do not block traffic when moving your equipment to the next worksite. This repair has been completed. But before they go, remember there are nine steps for base and sub-base repair. Step 1. Place the traffic control devices. Be sure the signs, cones and barricades are placed correctly. Step 2. Mark the limits of repair and cut the pavement. Make sure the limits are marked well within the area of firm pavement and the cut is straight and vertical. Step 3. Remove all unsuitable material. This includes damaged pavement as well as weakened base, sub-base and sub-grade. Step 4. Install any required sub-drainage. Follow the engineer's instructions to help prevent future saturation problems. Step 5. Restore the sub-grade. Use approved material and compact each layer. Step 6. Replace the base. Use approved material and compact each layer to the same elevation as the surrounding granular base. Step 7. Replace the pavement surface as originally constructed. Step 8. Clean the worksite. Sweep the area clean of any loose aggregate and other unwanted debris. Step 9. Remove the traffic control devices. Pick them up in the reverse order of their placement. This repair is a major operation to correct the very serious problem of a weakened road base. It requires proper planning and coordination. You must closely coordinate this work with your maintenance supervisor or maintenance engineer several times during the repair. Also, your instructions to the workers must be clearly understood. Your carefully coordinated efforts will make this important repair last a long time.