|Major Topics on this Page|
|4.1||Joint and Crack Sealing|
Pavement maintenance describes all the methods and techniques used to prolong pavement life by slowing its deterioration rate. Thus, the performance of a pavement is directly tied to the timing, type and quality of the maintenance it receives. This section, taken largely from Roberts et al. (1996), describes the more common U.S. preventative and corrective maintenance options for rigid pavement. The timing of these maintenance items is discussed in Module 11, Pavement Management.
Sealant products are used to fill joints (see Figures 10.20 and 10.21) and cracks in order to prevent entry of water or other non-compressible substances. Although most rigid pavement joints are sealed at the time of new construction, the useful sealant life is limited as stated by the ACPA (2001) on their web site:
"A typical hot-pour sealant provides an average of 3 to 5 years of life after proper installation. Some low-modulus or PVC coal-tars can perform well past 8 years. Silicone sealants have performed well for periods exceeding 8 to 10 years on roadways. This type of performance hinges on joint preparation and installation. Of extreme importance is that the joint be clean and dry. Compression seals provide service for periods often exceeding 15 years and sometimes 20 years."
Crack sealant is typically used on early stage, isolated panel cracks; extensive or advanced panel cracking is a symptom of larger problem (e.g., lack of panel support, inadequate structural design or poor construction) that cannot be addressed by simple crack sealing.
|Purpose:||Preventive maintenance. Joint and crack filling to prevent entry of water or other non-compressible substances into the pavement.|
|Materials:||Hot-pour seals, compression seals, silicone seals|
performance is dependent upon proper joint design and cleanliness.
|Figure 10.20: Joint Sealing||Figure 10.21: Joint Sealing Close-Up|
Slab stabilization seeks to fill voids beneath the slab caused by pumping, consolidation or other means. If left untreated, these voids, which are often quite small (on the order of 3 mm (0.125 inches) deep), may cause other problems such as faulting, corner breaks or cracking (ACPA, 1995). Voids are typically filled by pumping grout through holes drilled through the slab.
|Purpose:||Preventive and corrective maintenance. Restores proper base/subgrade slab support to prevent more serious distresses such as faulting, corner breaks and cracking.|
|Other Info:||Slab stabilization only fills the voids under a slab, it should not be confused with slab jacking, which is used to raise the elevation of a depressed slab.|
Diamond grinding (see Figure 10.22) refers to a process where gang-mounted diamond saw blades (see Figures 10.23 and 10.24) are used to shave off a thin, 1.5 - 19 mm (0.06 - 0.75 inch) top layer of an existing PCC surface in order to restore smoothness and friction characteristics. Most often, it is used to restore roadway friction or remove roughness caused by faulting, studded tire wear, and slab warping and curling.
Diamond grinding can reduce the IRI of an older pavement to 1.0 - 2.0 m/km (63 - 126 inches/mile).
|Purpose:||Corrective maintenance. Restores pavement smoothness and frictional characteristics. Can also be used in new construction to attain initial specified smoothness, although properly constructed PCC pavements should not require any diamond grinding.|
|Materials:||Gang-mounted diamond saw blades.|
|Other Info:||Diamond grinding addresses serviceability problems
but not their root cause. For example, diamond grinding can
substantially reduce the roughness on a faulted rigid pavement, but it will
not address the cause of faulting, nor will it prevent roughness in the
future as a result of additional faulting.
Because the grinding head is cooled with water, a byproduct of diamond grinding is a slurry of ground PCC particles and water. Most of this slurry is picked up by vacuums within the grinding machine and either deposited along the highway shoulder (in some rural areas) or collected in trucks for disposal.
|Figure 10.23: Diamond Saw Blades||Figure 10.24: Gang-Mounted Diamond
Rigid pavement patches are used to treat localized slab problems such as spalling, scaling (e.g., reactive aggregate distress, over-finishing the surface), joint deterioration, corner breaks or punchouts. If the problem is limited in depth, then a partial depth patch may be appropriate, otherwise a full depth patch is recommended. A high quality patch can be considered a permanent repair, although all patches are treated as a form of pavement distress. Although HMA is sometimes used for emergency patches, PCC should be used for permanent patches. Fast-setting PCC is often used to minimize setting time.
Partial depth patches (see Figure 10.25) are used to restore localized areas of slab damage that are confined to the upper one-third of slab depth. Generally, this includes light to moderate spalling and localized areas of severe scaling (ACPA, 1995). Partial depth patches are usually small, often only 50 - 75 mm (2 - 3 inches) deep and covering an area less than 1 m2 (10.8 ft2) (ACPA, 1995). The generally partial depth patching process proceeds as follows (ACPA, 1995):
Full depth patches (see Figure 10.26) are used to restore localized areas of slab damage that extend beyond the upper one-third of slab depth or originate from the slab bottom. Generally, this includes spalling, punchouts, corner breaks, moderate to severe slab cracking and localized areas of severe scaling (e.g., reactive aggregate distress, over-finishing the surface) (ACPA, 1995). Corner breaks and punchouts should almost always be patched to full depth. When deciding between a partial and full depth patch for spalling and slab cracking, realize that joint spalls extending more than about 75 - 150 mm (3 - 6 inches) from the joint are indicative of possible slab bottom spalling. Corner breaks and slab cracking are indicative of structural inadequacies that cannot be addressed with partial depth patching. These problems should be addressed using a full depth patch. Figure 10.27 shows a full depth patch pour.
|Figure 10.26: Full-Depth Patch Preparation||Figure 10.27: Pouring a Small Full Depth PCC Patch on a Residential Street|
A PCC full depth patching process proceeds as follows (ACPA, 1995):
|Figure 10.28: Base Preparation||Figure 10.29: Drilling Holes for
Tie Bar Placement
Pavement maintenance prolongs pavement life by slowing its deterioration rate. This section has described some of the more common maintenance options in the U.S. Each option's effectiveness is dependent upon a multitude of local conditions. For most smaller agencies, the best advice when considering pavement maintenance options is to talk to local contractors and nearby agencies about what types of maintenance options have worked best in your local area.