High-performance, eco-friendly calcium carbonate cement via alginate-mediated biomimetic mineralisation

Calcium carbonate-based binders offer significant environmental advantages, particularly in carbon capture and sustainable construction. Inspired by the organic matrix in biomineralisation, this study investigates sodium alginate as a functional additive and matrix to enhance calcium carbonate cement. Incorporating 1.5 wt% sodium alginate within the mineralisation system yielded a lightweight composite with a compressive strength of 46 MPa and an elastic modulus of 800 MPa after 28 days of curing – improvements of 1084% and 155%, respectively, compared to alginate-free samples. The phase evolution and structural development influenced by alginate were extensively characterised using X-ray diffraction, thermogravimetric analysis, attenuated total reflection infrared analysis, scanning electron microscopy, and transmission electron microscopy. Alginate was pivotal in nucleating and stabilising amorphous calcium carbonate, orienting its subsequent transformation into spherulitic calcite. Micro-computed tomography analysis under compression revealed the exceptional elasticity and toughness of the alginate composites. It further elucidated the defects distribution of different features of the stabilisation and crystallisation within the composites before, during, and after compression. These findings underscore the critical role of biopolymer-mediated mineralisation in engineering high-performance, cementitious calcium carbonate composites. Beyond CO 2 sequestration, this environmentally friendly material offers promising applications in sustainable construction and advanced composite systems. • Sodium alginate enhanced CaCO 3 composites with 1084% strength gain. • Achieved 46 MPa strength and 800 MPa modulus in 28 days. • Alginate stabilises amorphous CaCO 3 , directing spherulitic calcite growth. • Micro-CT revealed defect distribution insights. • Bio-inspired binders offer promise for CO 2 storage and construction.