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All pavements require maintenance, due to deterioration caused by such things as traffic loads, temperature fluctuations, weather and changes in moisture content. The key to successful maintenance is careful planning and programming of the work to be done. The parking lot should be thoroughly inspected. Usually, this means that the inspection be made by walking. This enables the inspector to notice very small cracks and defects. In all cases of pavement deterioration, it is important to determine the cause of the difficulty. This will allow repairs that will correct the defect and prevent its recurrence. Time and money spent for such repairs are well invested, since the same repairs will not have to be repeated in the future. Pavements in need of maintenance or repair can exhibit any or all of the following conditions: This is the progressive separation of aggregate particles in a pavement from the surface downward. Usually, the fine aggregate comes off first and leaves little "pock marks" in the pavement surface. As the process continues, larger and larger particles are broken free, and pavement soon has the rough and jagged appearance typical of surface erosion. Raveling can result from lack of compaction during construction, construction during wet or cold weather, dirty or disintegrating aggregate, poor mix design, or extrinsic damage to the pavement. Shrinkage cracks are interconnected cracks forming a series of large blocks, usually with sharp corners and angles. They are caused by volume changes in the asphalt mix, in the base, or in the sub grade. These are interconnected cracks forming a series of small blocks resembling an alligator's skin or chicken wire. In most cases, alligator cracking is caused by excessive deflection of the surface over unstable sub grade or lower courses of the pavement. The unstable support usually is the result of saturated granular bases or sub grade. The affected areas inmost cases are not large; sometimes, however, they will cover entire sections of a pavement, and when this happens, it usually is due to repeated loadings exceeding the load-carrying capacity of the pavement. When areas of alligator cracking are left unrepaired, they will continue to grow, making the inevitable repair even more costly due to size and increased repair costs over time. Upheaval is the localized upward displacement of a pavement due to swelling of the sub grade or some portion of the pavement structure. In colder climates, upheaval is commonly caused by expansion of ice in the lower courses of the pavement or the sub grade. It may also be caused by the swelling effect of moisture on expansive soils. These are bowl-shaped holes of various sizes in the pavement, resulting from localized disintegration of the pavement under traffic. Contributory factors can be improper asphalt mix design, insufficient pavement thickness, or poor drainage. Also, potholes may simply be the result of neglecting other types of pavement distress. Poor drainage can be the result of a broken or partially blocked drainage line. This is usually the result of a deteriorated line that has collapsed. Another common problem is that the grouting in the bowl of the catch basin has let go, allowing dirt and debris to filter into the catch basin, plugging the drainage line. Often these types of problems are noticed when a sinkhole appears in the asphalt structure close to the catch basin or over the drainage line. Preventive maintenance means the early detection and repair of minor defects, before major repair or replacement is necessary; it is the only proper way to care for a parking lot. Preventive maintenance makes sense when one considers that cracks and other surface breaks, which in their first stages are almost unnoticeable, may develop into serious defects if not soon repaired. A parking lot is an investment, as is a building or any other capital structure. Just as a building must be maintained to ensure its maximum utility, so must a parking lot be properly cared for. When this care is taken, the parking lot users will be provided with an attractive and useful property. Proper maintenance will serve to preserve the facility for many years.
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