Mechanically Stabilised Semi-Rigid Pavements

Abstract

The present invention relates to a semi-rigid pavement comprising: an upper course comprising upper course aggregate and a hydrocarbon binder; a support layer comprising chemically-stabilised aggregate, the support layer located below the upper course; and a subgrade, the subgrade located below the support layer; wherein a geosynthetic is at least partially embedded in the chemically-stabilised aggregate that comprises the support layer.

1 . A semi-rigid pavement comprising:
 an upper course comprising upper course aggregate and a hydrocarbon binder;   a support layer comprising chemically-stabilised aggregate, the support layer located below the upper course; and   a subgrade, the subgrade located below the support layer;   wherein a geosynthetic is at least partially embedded in the chemically-stabilised aggregate that comprises the support layer.   
     
     
         2 . The semi-rigid pavement of  claim 1 , wherein the semi-rigid pavement has two configurations:
 a first configuration wherein the support layer is monolithic, the support layer being chemically and mechanically stabilised; and   a second configuration wherein the support layer is cracked, the support layer being mechanically stabilised.   
     
     
         3 . The semi-rigid pavement of  claim 1 , further comprising a base course. 
     
     
         4 . The semi-rigid pavement of  claim 1 , further comprising a layer of a granular fill. 
     
     
         5 . The semi-rigid pavement of  claim 1 , wherein the geosynthetic is selected from geogrids, geotextiles, geonets, geocells, geocomposites, and combinations thereof. 
     
     
         6 . The semi-rigid pavement of  claim 5 , wherein the geosynthetic comprises a geogrid or is a geogrid. 
     
     
         7 . The semi-rigid pavement of  claim 6 , wherein the geogrid is a multiaxial geogrid, optionally the multiaxial geogrid is a triaxial geogrid or a geogrid with multiple geometries. 
     
     
         8 . The semi-rigid pavement of  claim 7 , wherein the triaxial geogrid has one or more of the following properties:
 i. product weight of from 0.120 to 0.400 kg/m 2 , more preferably of from 0.150 to 0.350 kg/m 2 , most preferably of from 0.170 to 0.310 kg/m 2 , for example from 0.180 to 0.300 kg/m 2 ; and/or   ii. pitch of at least 30 mm, preferably of from 40 to 150 mm, more preferably of from 50 to 140, most preferably of from 65 to 125 mm; and/or   iii. junction efficiency of at least 90% preferably at least 95%, more preferably of at least 97%, most preferably of at least 99%, for example of 100%.   
     
     
         9 . The semi-rigid pavement of  claim 7 , wherein the geogrid with multiple geometries has one or more of the following properties:
 i. Apertures with triangular, trapezoidal, and hexagonal geometries; and/or   ii. Pitch of at least 30 mm, preferably of from 40 to 150 mm, more preferably of from 50 to 140, most preferably of from 65 to 125 mm; and/or   iii. Rib aspect ratio of at least 1, preferably, between 1 and 4; and/or   iv. Minimum rib thickness of at least 3 mm, preferably at least 5 mm; and/or   V. Where the geogrid has a solid inner layer and a two compressible outer layers, the two compressible outer layers are at least forty percent (40%) of the overall height of the geogrid, preferably at least seventy percent (70%).   
     
     
         10 . The semi-rigid pavement of  claim 6 , wherein the geogrid has a multilayer structure, optionally wherein the geogrid has a solid inner layer and compressible outer layers. 
     
     
         11 . The semi-rigid pavement of  claim 1 , wherein the geosynthetic is located at the base of the support layer. 
     
     
         12 . The semi-rigid pavement of  claim 1 , wherein the chemically-stabilised aggregate comprises a biochemical binder, a polymeric binder, a hydrocarbon binder, lime, cement, or a combination thereof, optionally wherein the chemically stabilised aggregate comprises cement, optionally up to 10% by weight cement, further optionally from 0.1 to 8% by weight cement, optionally from 0.5 to 5% by weight cement, yet further optionally from 1 to 4% by weight cement, and still further optionally from 1.5 to 3% by weight cement. 
     
     
         13 . The semi-rigid pavement of  claim 1 , wherein the chemically stabilised aggregate and/or the upper course aggregate comprise a continuously graded aggregate. 
     
     
         14 . The semi-rigid pavement of  claim 1 , wherein the support layer has a thickness of from 50 to 400 mm, optionally of from 75 to 300 mm, further optionally from 100 to 200 mm, yet further optionally of about 150 mm. 
     
     
         15 . The semi-rigid pavement of  claim 1 , wherein the upper course has a thickness of from 10 to 100 mm, optionally of from 25 to 75 mm, further optionally of about 50 mm. 
     
     
         16 . A method of constructing a semi-rigid pavement, the method comprising:
 a) providing a geosynthetic above a subgrade;   b) providing aggregate and binder over the geosynthetic such that the geosynthetic is at least partially embedded in the aggregate;   c) setting the binder to form a support layer comprising chemically-stabilised aggregate; and   d) providing an upper course comprising an upper course aggregate and a hydrocarbon binder above the support layer.   
     
     
         17 . A method of constructing a semi-rigid pavement with an improved lifespan, the method comprising:
 a) at least partially embedding a geosynthetic within an aggregate and a binder; and   b) setting the binder to form a support layer comprising chemically-stabilised aggregate,   wherein the support layer is incorporated into the semi-rigid pavement during construction.   
     
     
         18 . A method of constructing a semi-rigid pavement with a reduced thickness, the method comprising:
 a) at least partially embedding a geosynthetic within an aggregate and a binder; and   b) setting the binder to form a support layer comprising chemically-stabilised aggregate,   wherein the support layer is incorporated into the semi-rigid pavement during construction.   
     
     
         19 . Use of a geosynthetic to increase the lifespan of a semi-rigid pavement, the use comprising at least partially embedding a geosynthetic within an aggregate that is chemically-stabilised with a binder and incorporating into the semi-rigid pavement. 
     
     
         20 . Use of a geosynthetic to decrease the thickness of a semi-rigid pavement with a pre-determined lifespan, the use comprising at least partially embedding a geosynthetic within an aggregate that is chemically-stabilised with a binder and incorporating into the semi-rigid pavement. 
     
     
         21 . A method of operating a semi-rigid pavement, the semi-rigid pavement comprising a subgrade, a support layer of chemically-stabilised aggregate above the subgrade, wherein a geosynthetic is at least partially embedded in the layer of chemically-stabilised aggregate, and an upper course above the chemically-stabilised aggregate, wherein the semi-rigid pavement is capable of exhibiting:
 a first operating mode wherein the support layer is substantially monolithic, the support layer being chemically and mechanically stabilised such that load applied to the upper course is transferred to the subgrade; and   a second operating mode wherein the support layer is at least partially cracked, the support layer being mechanically stabilised such that load applied to the upper course is transferred to the subgrade;   the method comprising permitting traffic to pass over the semi-rigid pavement in at least one of the first and second operating modes.   
     
     
         22 . A method of designing a semi-rigid pavement for a location, the semi-rigid pavement comprising:
 an upper course comprising upper course aggregate and a hydrocarbon binder;   a support layer comprising chemically-stabilised aggregate, the support layer located below the upper course; and   a subgrade, the subgrade located below the support layer;   wherein a geosynthetic is at least partially embedded in the chemically-stabilised aggregate that comprises the support layer:   
       the method comprising:
 a) determining a target lifespan for the semi-rigid pavement; 
 b) determining the properties of the subgrade present at the location; 
 c) selecting the support layer of chemically-stabilised aggregate above the subgrade, wherein a geosynthetic is at least partially embedded in the layer of chemically-stabilised aggregate; 
 d) selecting the upper course; 
 e) predicting a predicted lifespan of the semi-rigid pavement comprising the subgrade, the selected support layer, and the selected upper course; 
 f) comparing the predicted lifespan with the target lifespan; and 
 g) repeating steps c) to f) if the predicted lifespan is less than the target lifespan. 
 
     
     
         23 . The method of  claim 22 , wherein the semi-rigid pavement further comprises a base course and/or a granular fill and the method further comprises additional steps of selecting a base course and/or a granular fill. 
     
     
         24 . A method of designing a semi-rigid pavement for a location, the method comprising:
 a) determining a target lifespan for the semi-rigid pavement;   b) determining the properties of a subgrade present at the location;   c) selecting a pre-designed semi-rigid pavement for the location, the pre-designed semi-rigid pavement comprising the subgrade, the selected support layer, and the selected upper course;   d) predicting a predicted lifespan of the pre-designed semi-rigid pavement;   e) comparing the predicted lifespan with the target lifespan;   f) if the predicted lifespan is less than the target lifespan, at least partially embedding a geosynthetic in the support layer and repeating steps d) and e).   
     
     
         25 . A method of maintaining a semi-rigid pavement, the semi-rigid pavement comprising:
 an upper course comprising upper course aggregate and a hydrocarbon binder;   a support layer comprising chemically-stabilised aggregate, the support layer located below the upper course; and   a subgrade, the subgrade located below the support layer;   wherein a geosynthetic is at least partially embedded in the chemically-stabilised aggregate that comprises the support layer;   
       the method comprising:
 a) determining acceptable values for one or more properties of the semi-rigid pavement; 
 b) waiting a survey period; 
 c) surveying the semi-rigid pavement and determining if the one or more properties of the semi-rigid pavement satisfy the acceptable values; 
 d) undertaking maintenance if the one or more properties of the semi-rigid pavement do not satisfy the acceptable values; and 
 e) repeating steps a) to d).