Severity levels How to Measure

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d. Possible causes

Causes include the expected alligator cracks one or more of the following reasons GTC, 1998: 1- Damaged layer of asphalt concrete as a result of damage to the substrate due to repeated traffic loads. 2- Instability of the foundation layer of asphalt case or layer under the foundation because of the drop surface. 3- Double layer foundation stone, making it unable to land resulting from excessive loads of traffic. 4- Aging of asphalt materials by the time. 5- Insufficient thickness of the pavement. 6- Poor drainage in the base layers and under the foundation.

2.3.1.2 Block cracking

a. Description

Blocks are interconnected cracks that divide the pavement into approximately rectangular pieces. The blocks may range in size from approximately 3 by 3cm to 3 by 3m.Block cracking usually indicates that the asphalt has hardened significantly. Block cracking normally occurs over a large proportion of pavement area, but sometimes will occur only in nontraffic areas. This type of distress differs from alligator cracking in that alligator cracks from smaller, many sided pieces with sharp angles. Also, unlike block cracks, alligator cracks are caused by repeated traffic loadings, and are therefore found only in traffic areas wheel paths. Figure 2.4 cracks and network levels of severity David, 2006. 18 Figure 2.4 Block Cracking GTC, 1998

b. Severity levels

Low level of intensity L: the classification of the low level of network cracks must provide one case: i. Non-filled cracks Non-Filled offer less than 10 mm. ii. Cracks filled with insulation any offer was in acceptable condition. Medium level of intensity M: the classification of moderate cracks network must provide one of the following: i. Width of cracks more than 10 mm and less than 75 mm. ii. Cracks introduced less than or equal to 75 mm and surrounded by light random badly broken. iii. Cracks filled with any offer and is surrounded by light random badly broken. Higher level of intensity H: it is for the classification of high intensity of the cracks network there must be one of the following: i. Any cracks filled or not filled with badly broken surrounded by random high or medium severity. ii. Showing unfilled cracks greater than 75 mm. iii. Cracks introduced about 100 mm and surrounded by very badly broken and broken.

c. How to Measure

Block cracking is measured in square meter of surface area. It usually occurs at one severity level in a given pattern section; however, any areas of the pavement section having distinctly different levels of severity should be measured and recorded separately.