Properties of recycled crushed sand on fresh and hardened mortars based on its particle size distribution

Abstract

The recent amendment of DIN 1045 allows the use of recycled aggregates with particle sizes below 4 mm and 2 mm, although restrictions regarding replacement levels and exposure classes remain. Currently, only Type I recycled aggregates can be used without individual approval. This study investigates recycled aggregates from multiple producers, focusing on particle size distribution and its influence on mortar properties. In addition to dry sieving, computerized particle analysis (CPA) and laser diffraction were used to characterize the full particle spectrum, including fine fractions. Densities of aggregates and cement were determined to ensure consistent mixture design. The results show that particle size distribution, shape, porosity and type have a stronger impact on fresh and hardened properties than CO ₂ conditioning, which exhibited only minor effects. These findings highlight the importance of optimized particle packing and support the increased use of fine recycled aggregates.