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Concrete waste as a substitute for natural graded aggregate

Promotora Mediterránea-2, S. A. (PROMSA) is a company part of the Cementos Molins group that sells construction materials such as concrete, aggregate and mortar. The company is also dedicated to the recycling of materials and the recovery of waste aimed to produce refused derived fuel (RDF).

During the distribution of the materials to the different customers, concrete goes back to the PROMSA manufacturing plant. The returned concrete can be of 1 or 2 m3 (interesting volumes from 2 m3). This is considered waste together with the concrete exceeding from the production of fresh concrete. The company PROMSA manages this waste as a by-product to be used as raw material in the production of fresh concrete and to be more environmentally and economically efficient. PROMSA reuses the leftovers as aggregates, since the company has recycling plants where they separate the aggregate from the water with fines (cement + fine aggregate). The composition of the concrete is a mixture of aggregates (40% coarse aggregate, 40% fine aggregate), cement (13% cement) and water (7% water with additives).

Once the concrete is almost solidified, this is shredded and stacked to be valued as an aggregate, and to be used to make fresh concrete.

In addition to this internal recycling, another management route is as a by-product. The remaining waste concrete is used as raw material in the company VIVANCO HERNÁNDEZ, SA. Specifically, it is used in its natural aggregate crushing plant for the manufacture of the gravel, a mixture coming from crushed limestone aggregates. Limestone is found in 80% of the concrete composition, as a result the use of concrete waste can replace part of the natural aggregate, can be mixed with natural aggregates in order to manufacture new aggregates to be applied in public works and construction.

The advantages of managing concrete waste as a by-product (Catalan regulatory framework) are:

  • Reduction of the consumption of natural resources (sand and gravel extracted from quarries and gravel pits).
  • Reuse of construction materials that allows to avoid the waste disposal in the controlled deposit.