Training of supervision engineers
Basic training of owner’s supervision engineers
Additional training of owner’s supervision engineers
Construction of cold in place recycling layers
Using old asphalt layers for cold in place recycling
One of the most wide-spread technologies of using old asphalt layers is cold in place recycling. The old asphalt-concrete layer is crushed by cold milling and either transported to the storage area (when it is necessary to change or improve the base course) or spread evenly on the road. Samples are taken from the crushed old asphalt layer and particle composition and bitumen content will be determined. Based on these samples the added mineral material (e.g. crushed stone) and its quantity per m2 will be decided. For cold in place recycling layer it is necessary to compile a formula, which is the basis of constructing the layer. Depending on which binder is used, there are three cold in place recycling methods that are mainly being used:
Cold in place recycling with bitumen – bitumen as binder
Cold in place recycling with cement – cement as binder
Cold in place complex recycling – both bitumen and cement as binders
In Estonia mostly complex recycling is being used.
When the Client has approved the formula, the materials are transported to the construction site. In case the material was previously taken to the storage area, the mineral material (crushed stone) is transported onto the road and after that crushed old asphalt (milled asphalt) is laid evenly on top of it. Binders are added during mixing. For mixing a special machine is used, e.g. Wirtgen 2500 or something similar. Material is mixed either once or several times. In case of several mixings the binders are added during the first mixing.
After mixing the layer is graded (given longitudinal and cross direction falls) and compacted. The cold in place recycling layer sets in minimum 7 days. After that (when the humidity content of the layer is less than 2,5%) the paving asphalt layer can be placed on top of the cold in place recycling layer using bitumen tack coat.