A Novel, Multifunctional, Floatable, Lightweight Cement Composite: Development and Properties

This paper presents the development of a novel, multifunctional, floatable, lightweight cement composite (FLCC) using three different types of glass microspheres for structural engineering applications. Eight different mixtures of FLCC were produced and their matrix-related parameters were examined experimentally by adopting different types of microsphere fillers, fiber content (polyethylene fibers (PE)), and water-to-binder ratios. Along with the mechanical properties such as compressive, flexural, tensile strengths, and modulus of elasticity, the water tightness of the material was evaluated by sorptivity measurements and the energy efficiency by thermal conductivity. The optimal FLCC has an oven-dry density of 750 kg/m³, compressive strength (f_cm) up to 41 MPa after 28-day moist curing, low thermal conductivity of 0.152 W/mK, and very low sorptivity. It is found that an optimized amount of PE fiber is beneficial for improving the tensile resistance and ductility of FLCC while a relatively large amount of microspheres can increase the entrapped air voids in the FLCC matrix and reduce its density and thermal conductivity. Microstructural analysis by scanning electron microscopy (SEM) reveals that the microspheres are distributed uniformly in the cement matrix and are subjected to triaxial compression confinement, which leads to high strength of FLCC. Segregation due to density difference of FLCC ingredients is not observed with up to 60% (by weight) of glass microspheres added. Compared to the other lightweight aggregate concretes, the proposed FLCC could be used to build floating concrete structures, insulating elements, or even load-bearing structural elements such as floor and wall panels in which self-weight is a main concern.