In the name of Allah, who is most merciful & most gracious.

Reflection cracks.

Hafiz Junaid Mushtaq2012-BT-Civil-24

Hafiz Muhammad Nadir Ali2012-BT-Civil-11

Reflection cracks.Hafiz Muhammad Nadir Ali2012-BT-Civil-11

Reflection cracks.

Concrete joints reflected through bituminous overlay.

Reflection cracksCracks in overlays reflect the crack pattern in the pavement underneath. They are difficult to prevent and correct. Thick overlays or reconstruction is usually required.

Cracks in a flexible overlay over an existing crack or joint. The cracks occur directly over the underlying cracks or joints. “Joint reflection cracking” specifically refers to reflection cracks arising from underlying PCC pavement joint movement. Reflection cracks can also occur over existing cement or lime stabilized base, etc

Background.

Reflective cracks are caused by discontinuities in the underlying layers which propagate through the HMA surface due to movement at the crack.

Most common in asphalt overlays placed on rigid pavements.

Also occurs in asphalt overlays on cracked asphalt concrete pavements;

Also in asphalt pavements with stabilized bases.

Types of reflective cracking

Double reflective crackingSingle reflective cracking

The opening and closing of the joint or crack.

temperature variations caused thermal stress and induces cracking initiation.

traffic loading and associated stress play a role in the second step of propagation.

Mechanisms of Single Reflective Cracking.

Prevention.Design asphalt mixtures with higher cracking resistance.

Increase overlay thickness.

Use a modified overlay mix.

Modifying existing pavement prior to overlay construction.

Use of interlayer to reduce stresses and inhibit cracks.

Geogrid System.

Reflective crack in Washington

Geogrid in pavement System

Primary function is reinforcement through• Lateral restraint.• Improved Bearing capacity.• Tension membrane effect.• Reduced cost by reducing pavement structure thickness and

increases pavement life.

Geogrid enhances:• Stiffness and resiliency of aggregate and granular fill• Load distribution• Rutting resistance under repeated loads• Bearing capacity and settlement resistance• Separation of dissimilar soils

Geogrids for Roadway Applications

Function and PerformanceGeogrids

Improved Bearing Capacity.

Case HistorySalo Road Washinton D.C

That’s It. Thanks for your Attention.