In recent years, the application of sustainable cementitious materials has become of great importance to improve buildings efficiency and to achieve carbon neutrality. Main goal of this work to study and develop BIOAERMAC, an innovative construction material with low density, composed of synthetic anhydrous calcium sulfate obtained as by-product in the industrial production of hydrofluoric acid and an aerating agent composed of microorganisms and peroxides, with the addition of rubber from end-of-life tires (ELTs). A density from 600 to 950 kg/m³ with a compressive strength up to 6.0 MPa and a thermal conductivity from 0.15 to 0.3 W/mK are the key performance metrics of BIOAERMAC composites. Experimental results showed an improvement in technical and energy performance, combined with a reduction in natural resource consumption and the wide quantity of by-product reintroduced into the production process.

The transition towards carbon-neutral construction materials requires innovative solutions that combine reduced embodied energy, enhanced durability and improved building energy efficiency. This study investigates and compares two novel bioaerated low-density composites—BAAC and BIOAERMAC—developed through biologically driven aeration processes incorporating industrial byproducts. BAAC is produced using Saccharomyces cerevisiae and hydrogen peroxide, replacing conventional aluminum powder and improving safety while enabling the valorization of waste-derived yeast. BIOAERMAC is a gypsum-based composite incorporating synthetic anhydrite, microorganisms, peroxides, and recycled rubber from end-of-life tires. The materials were characterized in terms of hygrothermal behavior and dimensional stability, and compared with commercial autoclaved aerated concrete under equivalent mechanical strength conditions. The results highlight significant differences in moisture transport and shrinkage, primarily governed by pore structure and connectivity. BAAC exhibits behavior comparable to conventional AAC, whereas BIOAERMAC shows reduced capillary and hygroscopic absorption, indicating limited pore connectivity, but higher drying shrinkage. These findings demonstrate the effectiveness of bioaeration in tailoring pore structure and controlling the trade-off between moisture transport, durability, and dimensional stability, highlighting the potential of bioaerated composites for low-carbon and energy-efficient building applications.