Rational design of lightweight cementitious composites with reinforced mechanical property and thermal insulation: Particle packing, hot pressing method, and microstructural mechanisms

Low density, high strength, together with good thermal insulation are desirable but hard to achieve simultaneously for lightweight cementitious composites. This work addresses the preparation of a novel lightweight cementitious composite (HP-LWCC) by employing the hot-pressing method and optimizing the insulating particles packing. The main raw materials are glass microspheres (GB), fly ash cenospheres (FAC), white Portland cement (PW), aluminum cement (AC), and silica fume (SF). Results showed that HP-LWCC specimens with density of 800-1200 kg/m3 exhibited superior mechanical properties and thermal insulation. Their flexural strength, compressive strength, and thermal conductivity achieved 7.5-10 MPa, 30-51 MPa, and 0.16-0.29 W/ (mK), respectively. The microstructure results show that the packing of glass microspheres, which are tightly bridged by the hydration products, significantly refines the pore morphology, forming a denser cementitious matrix. The hot-pressing method benefits the reaction of aluminum cement and the alignment of fibers, resulting in high strength and flexural toughness. Based on the Compressible Packing Model, it is found that the optimized particles packing of HP-LWCC can decrease the porosity of specimens and improve the strength. Such HP-LWCC material provides a potentially solution in developing thermal insulated construction applications.