Within the process of recycling the RCD, are obtained on the one hand, as products, aggregates and recycled materials, and, as byproducts, other materials included within the RCD that can also be recovered in other authorized agents, such as plastic, wood, paper, cardboard and metals both ferrous and non ferrous metals. The other components of the RCD that can not be recovered are to be ultimately to landfill.
Recycled aggregates with different particle size for certain applications including bases and sub bases for roads and communication routes, urban fillings and earthworks, sea walls, fillings for berms and ditches, forest tracks and country roads, pavements of asphaltic agglomerates, etc ...
The reduced extraction of raw materials, lower transport costs, increased profits, reduced environmental impact and the quick depletion of the reserves of conventional natural aggregates have required the use of recycling in order to achieve conservation of the conventional natural aggregates.
Solid waste is generated as the building activity is developed, which includes construction and demolition. These residues contain sand, gravel, concrete, stone, brick, wood, metal, glass, plastic, paper, etc. The waste is generated from the demolition of structures by their deterioration, the demolition of structures to obtain better economic benefits (with new constructions) and the waste generated as a result of natural disasters. The applications of recycled aggregates can be summarized as follows:
Aggregates for road bases and sub bases
Aggregates for concretes
Aggregates for mortars
Aggregates for located fillings
Aggregates for drains, fills and beds of pipes
Recycled materials for restoration of degraded spaces
The recycling of this kind of residues through its transformation into aggregates, not only saves space in landfills, but it reduces the demand for extraction of natural raw materials for new ventures in the construction sector. The problem of demolition waste has become a major concern for planners, developers, engineers and environmentalists.
Therefore, an inevitable corollary is to use materials other than natural aggregates in order to save natural aggregate reserves for the most important works. The considerations related to sustainable development are central to these issues to ensure adequate resources for future generations. And in this context, it encourages the concept of recycling of demolition debris as it is useful construction material. The demolition debris generated in the process are mainly used as filler in other lands intended for construction.
In order to determine the applications of recycled aggregates, one must know the source RCD and the final composition of the aggregate. In a generic manner, we can say that there are three types of recycled aggregates:
• Concrete aggregates • Asphalt aggregates • Other recycled aggregates •
Recycled aggregates from concrete
The recycled aggregates coming from concrete are the most studied and those with a greater number of applications. The source RCD may be extremely varied, such as foundations and structures for buildings, foundations of rigid pavements, precast, etc.The working strength of starting concrete, although it is virtually impossible to determine and classify the plant for different stockpiles, when known, gives us a rough idea of the final characteristics of the aggregates.
The greater the resistance, the lower percentage of fines (declassified lower) and higher resistances to fragmentation.
Aggregates from layers of asphaltic agglomerate
This type of recycled aggregate, has, like the one coming from concrete, a core formed by the natural source aggregate, covered by a matrix of asphalt, which is porous and highly resistant to wear and abrasion.
These characteristics translate into the obtaining of aggregates with a very small percentage of declassified lower and high values of the Los Angeles coefficient, as no fines are generated by friction of the aggregate in the screens or transport tapes, unlike in the recycled aggregate coming from concrete.
Other recycled aggregates
In addition to the aggregates coming from concrete and asphalt agglomerate, which are usually used in construction, there are aggregates from clean ceramic, and aggregates coming from mixtures.
Because of its hygroscopicity, it retains moisture and, therefore, they have numerous applications in gardening and ecological covers.