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There is no argument that all asphalt cement (AC) pavements crack. Cracks in asphalt pavements are inevitable. Neglect and lack of proper maintenance lead to accelerated cracking and/or potholing, further reducing the serviceability of the pavement.
There are numerous reasons for asphalt to crack which can be broadly categorized into four distinct classes.
Once cracks develop, water easily penetrates into the base and sub-base of the pavement and damages the structural integrity of the aggregate materials. Pavement joint and crack sealants are designed to protect the pavement by minimizing water infiltration and by preventing the accumulation of debris. It has been amply demonstrated and documented that sealing cracks in flexible pavements is a sound preventive maintenance procedure, which adds many years to the life of the pavement, especially when used in conjunction with seal coating.
The U. S. Army Corp of Engineers, CRRL, undertook a national survey of the crack sealing practices of the Department Of Transportation of all 50 states. It was concluded that 45 states utilized crack sealing under their standard pavement maintenance program. Even the sates that did not do crack sealing, recognized that cracks in their pavements were a problem. States with numerous freeze-thaw cycles cited that;
It has been estimated that ninety percent (90%) of asphalt roads in the United Sates have significant problems due to the deterioration of the base and sub-base material because of water infiltration.
Pavements where cracks have not been sealed, offer many routes for water entry into the base and sub-base courses. Water will penetrate through cracks that are over 1/8th to ¼ inch wide. Finer cracks also allow water infiltration into the pavement through the pumping action of the traffic; the surface water is pushed into the cracks when vehicles pass over the cracks. For cracks larger than ¼ inch, water flows under gravity into the surface and the base course. Once water enters the base, the aggregate absorb the water expand in volume and become soft, thus causing internal stress which accelerates the development of more and larger cracks.
Life Cycle Cost Analysis (LCCA) is defined as “a process for evaluating total economic worth of a usable project segment by analyzing initial costs and discounted future costs, such as maintenance, user costs, reconstruction, rehabilitation, and restoring and resurfacing costs, over the life of the project segment.”
Crack sealing, like any other maintenance project, has to be done with proper economic justification, using proper materials and procedures. It is an established pavement preservation technology, which is steadily evolving to meet the challenges of modern age traffic requirements, utilizing state-of- the-art materials and tools.
Crack sealing is highly cost effective and a lot less expensive than other preventive procedures e.g. an asphalt overlay which costs 8 to 26 times as much as crack sealing. Furthermore, crack sealing slows the reappearance of reflective cracks in the new surface after an overlay. Reflective cracks may be considered as secondary cracks which are caused by the problems within the base course and can not be eliminated without addressing the initial cause of the problem.
State maintenance departments bear most of the burden of dealing with cracks and out of several options available to them (slurry, chip sealing, overlays, etc.), they commonly exercise crack sealing.
Crack sealing is a highly cost effective maintenance procedure for asphalt pavement. Most states in the U.S. use crack sealing as part of their standard pavement maintenance program.