Cinderela pilot project - Road construction in Madrid (by AEDHE)

Recommendations for the demolition
The critical parameters related with this kind of materials are the water absorption and the total
sulphur content. Due to the high amount of attached mortar paste to the original aggregates, the
water absorption is drastically increased compared to natural aggregates. This higher water
absorption will determine the amount of water to be included during the mixing process in order to
have a good balance between the fresh consistency and the hardened mechanical properties.

The second parameter is related with the gypsum presence. As explained above, the presence of gypsum
can cause swelling inside the concrete and the fracture of the elements.
It is obligatory to perform a selective demolition in order to avoid gypsum components and other
waste streams:
- The components X should be removed as much as possible before the demolition and during
the processing in order to obtain fractions ≤ 1%. I.e. gypsum, plastics, wood, insulations,
metals, etc.
- The clean concrete should be demolished, stocked and processed separately, i.e. the
concrete from the structure, pavement, slabs, foundations, etc.
- Special attention must be paid to hazardous elements and substances during demolition
(asbestos, contamination by heavy metals, hydrocarbons, volatile organic components, etc.).
If dangerous substances are detected during the pre-demolition audit, these materials shall
be removed, managed and treated according to the Spanish regulation10
.
Recommendations for the processing
The Coarse Recycled Concrete Aggregates must be treated appropriately in order to be used in
recycled concretes for the demos 3A and 3C. Some key aspects are detailed below:
- The material must be processed by metal extraction, crushing below 20 mm, and sieving
between in order to recover fraction 4-20 mm.
- Avoid the generation of fines during the processing; this can be achieved by using jaw
crushers instead of impact crushers.
- Pre-sieving (20 mm) to avoid the feeding with unnecessary material and thus reduce the
production of more fines shall be used
- The coarse recycled concrete aggregates shall be stocked separately.