HIGHWAY MAINTENANCE Failures in flexible pavement

Outcome of this session The student would be able to Identify the different types of failure in flexible pavements List down the causes and symptoms of flexible failures Suggest suitable treatments for failure of flexible pavement

Recap of Flexible Pavement Elastic Less flexural strength More number of layers Materials - Gravel , tar / bitumen Cost - Less construction cost more maintenance cost Opened to traffic within 24 hours of construction

Defects in flexible pavement 1.Surface defects 2.Cracks 3.Deformation 4.Disintegration

1.Surface defects Symptoms Causes Treatment Fatty surface Smooth surface Streaking Hungry surface Symptoms Causes Treatment Collection of binder material Excessive binder Loss of aggregate Non uniform spreading Application of sand Application of Seal coat Removal and replace

1.Surface defects(contd..) Fatty surface Smooth surface Streaking Hungry surface Symptoms Causes Treatment Slippery when wet Excessive binder Polishing of aggregate under traffic Resurfacing Application of slurry Seal coat

1.Surface defects(contd..) Fatty surface Smooth surface Streaking Hungry surface Symptoms Causes Treatment Presence of lean bitumen in longitudinal and transverse direction Non uniform application of bitumen Resurfacing

1.Surface defects(contd..) Fatty surface Smooth surface Streaking Hungry surface Symptoms Causes Treatment Loss of aggregate from surface Appearance of fine crack Less bitumen usage Use of absorptive aggregate Application of slurry seal

2.Cracks Symptoms Causes Treatment Appearance of short and fine crack at close interval Less bitumen usage Excessive filler Improper compaction Depends on whether pavement is sound or not Sound – slurry seal can be used Not sound – rehabilitation Hair-line cracks Alligator cracks Longitudinal crack Edge crack Shrinkage cracks Reflection cracks

2.Cracks(contd..) Symptoms Causes Treatment Interconnected cracks – small blocks – skin of alligator Excessive deflection – unstable sub- grade Brittleness of binder(due to age of binder) Depends on whether pavement is sound or not Sound – slurry seal can be used Not sound – rehabilitation Hair-line cracks Alligator cracks Longitudinal crack Edge crack Shrinkage cracks Reflection cracks

2.Cracks(contd..) Symptoms Causes Treatment Hair-line cracks Alligator cracks Longitudinal crack Edge crack Shrinkage cracks Reflection cracks Symptoms Causes Treatment Cracks in straight line along the road (joints -(shoulder & road) (two lanes)) Alternate wetting and drying Depends on whether pavement is sound or not Sound – slurry seal can be used Not sound – rehabilitation

2.Cracks(contd..) Symptoms Causes Treatment Hair-line cracks Alligator cracks Longitudinal crack Edge crack Shrinkage cracks Reflection cracks Symptoms Causes Treatment Cracks parallel to outer edge 0.3 – 0.5 m from edge Sometimes transverse cracks appear from this Lack of lateral support Settlement of underlying material Improper surface drainage Shrinkage Frost heave Improper width of pavement Depends on whether pavement is sound or not Sound – slurry seal can be used Not sound – rehabilitation

2.Cracks(contd..) Symptoms Causes Treatment Hair-line cracks Alligator cracks Longitudinal crack Edge crack Shrinkage cracks Reflection cracks Symptoms Causes Treatment Cracks in transverse cracks direction Shrinkage due to age (materials) Depends on whether pavement is sound or not Sound – slurry seal can be used Not sound – rehabilitation

2.Cracks(contd..) Symptoms Causes Treatment Hair-line cracks Alligator cracks Longitudinal crack Edge crack Shrinkage cracks Reflection cracks Symptoms Causes Treatment longitudinal, transverse , diagonal or block cracks Cracks in pavement underneath Depends on whether pavement is sound or not Sound – slurry seal can be used Not sound – rehabilitation

Settlement and upheavel 3.Deformation Symptoms Causes Treatment Cresent shaped cracks – in direction of thrust of wheels Thrust of wheels Inadequate prime or tack coat Lack of bond b/w layers Excessive deflection leading to failure in bond Resurfacing Slippage Rutting Corrugation Shoving Shallow Settlement and upheavel

Settlement and upheavel 3.Deformation(contd..) Symptoms Causes Treatment Longitudinal depression or groove heavy traffic Inadequate compaction Improper mix design Filling with premix open graded patching material after a tack coat and compacting Slippage Rutting Corrugation Shoving Shallow Settlement and upheavel

Settlement and upheavel 3.Deformation(contd..) Slippage Rutting Corrugation Shoving Shallow Settlement and upheavel Symptoms Causes Treatment Undulations( ripples) Faulty laying of surface course Lack of stability in mix Resurfacing that affected area

Settlement and upheavel 3.Deformation(contd..) Slippage Rutting Corrugation Shoving Shallow Settlement and upheavel Symptoms Causes Treatment Plastic movement within the layer - bulging Lack of bond b/w layers Lack of stability in mix Heavy traffic Use of non –volatile oil on wheel roller Removal of the material and patching

Settlement and upheavel 3.Deformation(contd..) Slippage Rutting Corrugation Shoving Shallow Settlement and upheavel Symptoms Causes Treatment Shallow depression settlement of lower layers Filled with premix material

Settlement and upheavel 3.Deformation(contd..) Slippage Rutting Corrugation Shoving Shallow Settlement and upheavel Symptoms Causes Treatment Large deformations Uncomfortable for traffic Inadequate compaction Excessive moisture in sub grade Inadequate pavement thickness Frost heave Excavate and refill Under drains can be provided Proper redesign reconstruction

4.Disintegration Symptoms Causes Treatment Stripping Loss of aggregate Ravelling Pot hole Edge breaking Symptoms Causes Treatment Loss of bond and strength of aggregate improper aggregate usage (design) Spreading and compacting coarse sand (heated) Replacing fresh bituminous mix

4.Disintegration(contd..) Stripping Loss of aggregate Ravelling Pot hole Edge breaking Symptoms Causes Treatment Loss of aggregate leading to rough appearance poor binding b/w aggregate and binder Application of liquid seal, fog seal or slurry seal

4.Disintegration(contd..) Stripping Loss of aggregate Ravelling Pot hole Edge breaking Symptoms Causes Treatment Failure of binder – eroded areas at edge inadequate compaction Construction during wet weather Use of inferior quality aggregate Insufficient binder – ageing of binder Application of cut back bitumen covered with coarse sand or slurry seal

4.Disintegration(contd..) Stripping Loss of aggregate Ravelling Pot hole Edge breaking Symptoms Causes Treatment Bowl shaped holes of various sizes penetration of water into the pavement Application of premix open graded or dense graded patching or penetration patching

4.Disintegration(contd..) Stripping Loss of aggregate Ravelling Pot hole Edge breaking Symptoms Causes Treatment Irregular breakage leading to peeling of surface penetration of water into the pavement patching

Formative assessment (Multiple Choice Question) (Answer the following questions as the reflection of the material which you have seen in the above presentation)

Question number 1 Bowl shaped holes of various sizes is the symptoms of _____________ type of failure Cracks Surface defects Disintegration deformation

Question number 2 __________is one type of deformation failurein flexible pavement Stripping Corrugation Longitudinal crack Streaking

Question number 3 Excessive deflection due to unstable sub- grade results in _________failure Longitudinal crack Alligator crack Edge crack Reflection crack

Thank you