Demand for construction materials has been rising in recent decades in many countries around the
world, placing a heavy burden on the environment in terms of both the natural resources consumed
and the enormous flow of waste generated. In order to obtain a more sustainable construction, it is
often suggested to reintroduce the industry’s own waste as input for the manufacture of new materials.
In this study, the use of construction and demolition waste of concrete or mixed concrete/ceramic
nature is investigated as a replacement of natural aggregates in concrete. The greater affinity of
recycled aggregates for water directly affects the workability and/or the concrete strength and
durability. One possible solution to reduce the aggregates water absorption is to apply a biogenic
treatment with calcium carbonate-precipitating bacteria that consolidate the aggregate surface or the
adhering mortar.
Experimental results show that the biodeposition treatment reduced the recycled aggregate water
absorption by generating precipitation in the pores and an impermeable outer layer, most effectively
on the roughest particle surfaces. The largest decrease happened in the aggregates with the highest
porosity. The biogenic layer had a good cohesion with the aggregates. The results of sonication
indicated that the most effective treatment was on recycled concrete aggregates (RCA) instead of
mixed aggregates (MA). Therefore, the treated RCA was used to make concrete for further
investigation. The concrete made with bio-treated RCA had a denser structure, a decreased water
absorption (around 1%) and an improved compressive strength (25%)
