Cold recycling in site
Reasons to use it
Road surfaces, the condition of which is very bad, for example, their wearing course is damaged extensively and little bearing power of the road base, need more serious repair works. In these cases, it is often necessary to replace either the whole roadway construction or to replace it for the most part. Further, when constructing roads, motorways, local roads, airports, railways, parking and aside areas, but also when building consolidated areas for commercial and industrial constructions, it is necessary to improve the unsatisfactory bottom courses. To do so, we have two possibilities:
- To replace the former construction layers by new ones
- To use the technology using the original material of the former roadway construction.
As we think economically, we are aware of the fact that roadways are a source of precious building materials. Today, the tendency is to prefer technologies, which are fast, economical, contributing to the environmental protection and, of course, guaranteeing the requested quality. We offer you one of the possibilities using the original material or the bottom course material during the roadway reconstruction. It is a technology of cold recycling in site. This term means a process, when the recycler disintegrates the original roadway construction or the bottom course material in the requested thickness - at the same time it is transformed into the bearing basis course. The process of cold recycling in essence is in principle as follows:
- Disintegration of the original layers of the roadway construction
- Granularity preparation of disintegrated mixture by adding aggregates
- Dosing of the bonding agent on the basis of the analysis of material samples taken from the former construction
- Even spreading of the recycled mixture
- Compaction by heavy rollers
Technology and application field
The technology of cold recycling in site can be divided into three basic groups according to the kind of the bonding agent used:
Cold recycling with a hydraulic bonding agent (either cement or lime)
Cold recycling with a bituminous bonding agent (either bituminous emulsion or foamed bitumen)
Cold recycling with a combined bonding agent (either cement and bituminous emulsion or cement and foamed bitumen)
Cold recycling with a hydraulic bonding agent is used mainly for the improvement of the subsoil of road and motorway roadways, local roads, railways and large consolidated areas (parking areas, airports, industrial halls, department stores, etc.), but also for bottom courses made of the recycled material of the original roadway.
Cold recycling with a bituminous or combined bonding agent is convenient especially for bases of roadways made of the recycled material of the original roadway, possibly from other recycled or local materials. Mostly, the additional bituminous emulsion and foamed bitumen cold mix – FBCM are used, but also the combination of bituminous bonding agent with cement has proved good. As for the foamed bitumen cold mix technology, this is a mixture made by adding hot foamed bitumen (bituminous foam) into not heated – cold recyclate
The foamed bitumen is made by mixing of hot bitumen with water and it offers suppliers further cost savings as it disperses the matrix in the recycled mixture in a better way.
The foamed bitumen is made by mixing of hot bitumen with water and it offers suppliers further cost savings as it disperses the matrix in the recycled mixture in a better way. The tests used so far show that the foamed bitumen needs considerably smaller quantity of bitumen than traditional methods. The recycled material of the original roadway is mostly refilled by the filling aggregates for the granularity preparation depending on the layer thickness. The mixture itself is made in the recycler, equipped with a plant to manufacture and dose the foamed bitumen. Alternative systems use improved computer control for the automatic adjustment of the foam bitumen quantity according to the processed weight of recycled mixture, depending on the speed of operation, width and depth of milling.
Our company used this technology for the first time in the Czech Republic in the repair works of the main street in Hlohovec near Lednice, where we used the following process:
- Before recycling, the profile grade was reduced for milling by the recycler WR 2500
- For mixture preparation, the small aggregates were added (spread by the grader)
- Cement dosing was carried out directly onto the roadway by the dosing device
- Milling and mixing of the mixture with the combined matrix (foamed bitumen + cement) by the recycler WR 2500
- Profiling of the recycled mixture by the grader
- Compaction of the modified layer by rollers
- Samples were taken from the recycled mixture for the recycling quality control. Test pieces were made from these samples in the field laboratory and then tested.
The mixture is used for road bases, bed layers or levelling layers when reconstructing or strengthening the roadway. The use of hydraulic and bituminous bonding agent combination makes the layer more flexible in comparison with the hydraulic bonding agent and considerably decreases the susceptibility of the mixture to the of frost cracks.
The advantages of cold recycling in site
- Use of the original roadway construction material
- No need of storage areas for demolished original materials
- Saving of new building materials consumption (natural sources protection)
- Way of bonding agent dosing guarantees its proportional blending into the mixture
- Original roadway can be recycled into the requested depth without the failure of lower layers
- Lower price in comparison with the traditional way of road base reconstruction (savings of energy and building materials)
- Shortening of the construction period (all operations are in one working cycle, no demolition and removal of the original roadway material and no delivery of material for the new road base)
- Building environs are without noise, vibrations, pollution, dust and mud, which are caused by removal and delivery of building materials etc.
Processes of cold recycling in site combine many social, economic and environmental relations that are very important for everybody. The clear and main advantage of this technology is complete reusage of all original materials (bituminous mixtures and road base), which represents 100 % previous investment. In this way, we save the costs of removal of the demolished material from the side and possible fees for storage areas. The use of new building materials is thus limited just to aggregates for granularity preparation of recycled mixture and bonding agent. The used building machines and processes allow deeper recycling and using adjustable recycling machines enables the contractor to adapt the working parameters of a building machine for each individual order or application. For example, depending on the quality of aggregates from the roadway, and the requested final result, it is possible to adjust the depth of the drum, so that the necessary volume of material is admixed from the bed layer or the road base.
Druhy používaných zariadení: V našej spoločnosti používame recykléry s pracovnou šírkou 1,3m, 2,0m a 2,5m.