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The use of geogrid reinforcement for enhancing the performance of concrete overlays

Concrete overlays of existing rigid pavements have been extensively used for the rehabilitation of the pavement’s structural capacity. The thickness of concrete overlays typically ranges between 2 and 11in depending on whether they are bonded or un-bonded with existing pavement. One of the most serious problems associated with the use of thin concrete overlays is reflective cracking. This phenomenon is due to the horizontal and vertical movement of the underlying pavement layer caused by external loading and thus resulting in shearing and tearing of the overlay. Steel reinforcement is commonly proposed as a possible solution for this problem. However, the use of steel reinforcement in thin layers, where minimum concrete cover is not ensured, imposes problems like surface deterioration, steel corrosion and exposure, which creates great danger for on road vehicles.
This study suggests the use of geogrids as main reinforcement in thin concrete overlays; geogrids possess favorable characteristics in terms of strength, ductility and ease of installation. The objective is to study the effect of geogrid reinforcement on mitigating the cracks propagation and improving the design of the overlays. For that purpose, a finite element mathematical model was developed to simulate the performance of geogrid reinforced overlays. The model is first validated using data acquired from laboratory experimental set-ups, and then it is used to assess the effects of the geogrid type, location, and loading conditions on the performance of concrete overlays. The obtained results verify that the use of geogrid reinforcement significantly enhances the overlay performance; whereby geogrid reinforced models were more resilient to cracking than the unreinforced ones and demonstrated a reduction in the rate of crack propagation.

Author(s):

Hayssam Itani    
American University of Beirut
Lebanon

George Saad    
American University of Beirut
Lebanon

Ghassan Chehab    
American University of Beirut
Lebanon