Alligator Cracking

photograph CRACKING AN INTRODUCTION - Crocodile gap, also called fatigue snap bean or alligator let oning, is a habitual type of melancholy in asphalt pavage. Crocodile cleft is characterized by interconnecting or interlaced cracking in the asphalt layer resembling the hide of a crocodile. Cell sizes can transmute in size up to 300 millimetres (12in) across, but ar typically less than 150 millimetres (5. 9in) across. Crocodile cracking is generally a commitment failure, but numerous factors can contribute to it. It is often a trait of sub- footing failure, poor d rainfallage, or repeated over-loadings.It is important to prevent crocodile cracking, and repair as soon as feasible, as advanced cases can be rattling costly to repair and can lead to formation of potholes or premature sidewalk failure. CAUSES OF ALLIGATOR CRACKING - * Crocodile cracking is an asphalt pavement harm most often instigated by failure of the rise up payable to transaction loading. * Crocodil e cracking can be greatly influenced by environmental and former(a) effects while traffic loading remains the direct come to a leak. Frequently, overloading happens be create the basal or sub cornerstone inadequately support the surface layer and subsequently cannot bag piles that it would normally endure. Poor drainpipe in the road adjourn is a frequent cause of this degradation of the base or subgrade. A heavy spring thaw, similarly to poor drainage, can weaken the base course, leading to crocodile cracking. * Stripping or raveling is an different possible cause of crocodile cracking. Stripping emits when poor adhesion between asphalt and gather allows the aggregate at the surface to dislodge. If left uncorrected, this reduces the thickness of the pavement, reducing the impact portions powerfulness to carry its designed loading.This can cause crocodile cracking to develop rapidly, as overloading will happen with loads of less magnitude or frequency. CAUSES OF ALLIGATOR C RACKING - Failure of surface due to loading Stripping of bitumen due to poor adhesion of bitumen asphalt Environmental conditions - (a) Due to excessive rain b) hot weather (c) frost action CHARACTERISTICS or IDENTIFICATION - * Crocodile cracking manifests itself initially as longitudinal cracking (cracks along the direction of the current of traffic) in the top layer of the asphalt. * These cracks are initially thin and sparsely distributed. If further deterioration is allowed, these longitudinal cracks are connected by thwartwise cracks to form sharp sided, prismatic pieces. * This interlaced cracking pattern resembles the scales on the back of a crocodile or alligator, hence the name, alligator cracking. * More laborious cases involve pumping of fines, spalling, and loose pieces of pavement. * The most severe cases of crocodile cracking often occur with other pavement afflictiones, but are exemplified by potholes, large cracks(3/8 or larger), and severely spalled edges. MEASU REMENT & QUANTIFICATION -There are many different shipway to measure crocodile cracking, but in general a pavement put out manual or index will be used. For example, the Pavement set Index is widely used to quantify the overall level of distress and condition of a section of road. Measurement of crocodile cracking particularizedally(and pavement distress in general) is requisite to determine the overall condition of a road, and for end of a time-line for rehabilitation and/or repair. There are many other evaluation systems, and many rating systems currently in use are establish on the AASHO Road Test.There are two important criteria to take into effect when measuring crocodile cracking. The first is the extent of the cracking. This is the amount of road surface area which is affected by this pavement distress. The second criterion is the rigour of the cracking. Severity, which has been discussed above, refers to how far the cracking has progressed, and is often directly a fu nction of crack width. Severity may be rated numerically, or given a rating from low to severe. The rating may be entered into a pavement management system, which will suggest a priority and method for the repair.Systems generate been developed that detect crocodile and other types of pavement distress automatically. They measure the rigour and frequency of alligator cracking on the road-path. One such mold is the road surface profilometer, which is mounted on a vehicle and measures the profile of the road surface while it is moving down the roadway. PREVENTION & reconstruct - Preventing crocodile cracking can be as simple as preventing the common causes. Reducing overloading on an asphalt pavement or improving drainage can prevent crocodile cracking in many cases.However, often the particular proposition cause is fairly difficult to determine, and prevention becomes difficult correspondingly. A entire strategy to prevent overloading, which is a main cause of crocodile cracki ng, is to increase the reasonableness of the asphalt layer. According to certain researchers, pavements of a minimum strength or thickness can hypothetically handle infinitely many loads without showing structural defects, including crocodile (fatigue) cracking. These pavements are called perpetual pavements. When repairing pavement affected by crocodile cracking, the main cause of the distress should be determined. whatever investigation should involve barb a pit or coring the pavement and subbase to determine the pavements structural organization as easy as determining whether or not submerged moisture is a contributing factor. The repair needed also differs based on the severity and extent of the cracking. In the early stages, sealing cracks with crack sealant limits further deterioration of the subgrade due to moisture penetration. Small areas may be repaired by removal of the affected area, and replacement with new base and asphalt surface.Once the damage has progressed, a structural asphalt overlay or complete reconstruction may be necessary. CONCLUSION When repairing pavement affected by crocodile cracking, the main cause of the distress should be determined. However, often the specific cause is fairly difficult to determine, and prevention is therefore correspondingly difficult. Any investigation should involve digging a pit or coring the pavement and sub base to determine the pavements structural makeup as well as determining whether the moisture is a contributing factor.Small areas may be repaired by removal of the affected area, and replacement with new base and asphalt surface. Once the damage has progressed or the affected area is large and extensive, a structural asphalt overlay or complete reconstruction is necessary to ensure structural integrity. If the government also takes necessary action by giving an yardstick of the maximum ESWL that can be allowed, then cracking can be prevented. However in practical it is not possible always. Our co nciousness also plays a great role. If we can understand what can cause cracking and take necessary action, then it can be prevented.