In-situ micro-CT characterization of mechanical properties and failure mechanism of cementitious syntactic foams

The advancements in structural materials are guided by the desire of lowering the density and increasing the strength. Composite materials show promise in tuning the density and strength to meet specific design requirements. Lightweight cementitious materials, such as foamed concretes, are generally known to show poor mechanical properties (e.g., compressive strength and elastic modulus). The lack of control over the size, shape, and distribution of air voids severely limits the improvement of mechanical properties in lightweight cementitious materials. This work is focused on manufacturing and examining the mechanical properties of cementitious syntactic foams with hollow glass microspheres. Use of hollow particles to incorporate porosity allows for the control over the size, shape, and volume fraction of voids present in the composite. Hollow glass microspheres with several different densities (0.15-0.60 g/cm3) are used in different volume fractions (20%-50%) to manufacture the cementitious syntactic foams. The results show that cementitious syntactic foams (CSF) have compressive strengths (32-88 MPa) and elastic moduli (10-20 GPa) for a given range of low density (1.15-1.80 g/cm3), which are better than other cellular cementitious materials in the same density range. In-situ micro-CT scan results reveal that the micro-fracture mechanisms in CSFs under compressive loading depend on the microsphere density and aging of the material.