Dense-graded cold asphalts

As with any dense-graded mixture, DGCAs possess greater stability and stiffness, and are far less permeable to water, when compared to open-graded cold asphalts (OGCAs). 

The bituminous emulsion, preferably the cationic type, is produced from paving grade bitumen and should comply with the national specifications (CEN EN 13808 2013, ASTM D 2397 2012 or AASHTO M 208 2009, ASTM D 977 2012 or AASHTO M 140 2013, or Asphalt Institute 2008, for the European or US market). Useful information for selecting the appropriate bituminous emulsion can be found in an asphalt cold mix manual (Asphalt Institute MS-19 2008). 

Aggregates, as in hot asphalts, are preferably crushed materials of any appropriate rock or natural deposits. The use of uncrushed natural deposits should be avoided. 

In all cases, the properties of the aggregates should satisfy the requirements for bituminous mixtures, for example, CEN EN 13043 (2004) or Superpave requirements - see Section 5.4.2 or other national specifications. 

It is also recommended that the aggregate absorption should not exceed the value of 2%, particularly when the cold mixture is going to be used for surface course. Aggregates with higher absorption can be used only for layers below the surface course provided the water absorption is taken into consideration for the determination of the effective binder content. 

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The composition of dense-graded cold asphalts is carried out by in-house methodologies developed by organisations or by laboratories of the public/private sector, such as those... 

ANNEX 6.B MODIFIED MARSHALL MIX DESIGN FOR DENSE-GRADED COLD ASPHALT (DGCA)... 

ASTM D 7229. 2008. Standard test method for preparation and determination of the bulk specific gravity of dense-graded cold mix asphalt (CMA) specimens by means of the Superpave gyratory compactor. West Conshohocken, PA ASTM International. 

Construction processes may be more challenging. For example, gap and open graded RA has to be compacted at higher temperatures than conventional dense graded asphalt because the rubber stiffens the binders. The RA mixtures can also be difficult to hand work due to this stiffening, and the construction must be completed 48 h after mixing. Also, construction in cold temperatures, in the wet, and over pavements with severe cracks can cause problems. 

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