Surface protection of recycled concrete from different biogenic silica bio-deposition techniques: A sustainable approach

The increasing generation of construction and demolition waste poses an environmental challenge. In this study, the use of recycled concretes is proposed as a possible solution, reducing the extraction of natural resources and minimising the accumulation of waste in landfills. To ensure the durability and strength of this type of recycled concrete, two diatom culture techniques were developed in controlled environments to promote the bio-deposition of biogenic silica on the surface concrete. Through the resulting protective biofilm, diatoms decreased the capillary absorption and improved the impermeability of concrete to water and gases, such as CO2. Furthermore, these contributed to an increased mechanical strength of the concrete and a positive morphological modification of its surface by densifying and sealing surface pores. These results support the potential of diatoms as an effective solution to improve the properties and durability of recycled concrete. •Organic silica bio-deposition from diatoms in hardened concrete is analysed.•Bio-deposition of diatoms decreases the surface pores of recycled concrete.•The surface effect of biogenic silica increases the durability of recycled concrete.•Biogenic silica is an environmentally friendly alternative to synthetic treatments.