Nanoindentation has been reported as an effective tool for realizing the strength and stiffness (modulus of elasticity) of different materials including cementitious composites. However, to the best of the authors’ knowledge, nanoscale fracture of cementitious materials has rarely been examined.…
Nanoindentation has been reported as an effective tool for realizing the strength and stiffness (modulus of elasticity) of different materials including cementitious composites. However, to the best of the authors’ knowledge, nanoscale fracture of cementitious materials has rarely been examined. Fracture of ce- mentitious composites has been typically studied by observing crack growth of notched macroscale speci- mens subjected to flexural or tension loads. We discuss the possible characterization of fracture toughness of cementitious composites using contact mechanics at the nanoscale. This paper reports on the first experiments to evaluate fracture toughness of hydrated cement paste at the nanoscale. The analysis method is based on evaluating the energy absorbed by radial cracks propagating from the indentation imprint in brittle materials. Nanoindentation experiments performed using Berkovich nanoindenter are reported. The hardness, reduced elastic modulus and fracture toughness of hydrated cement paste are extracted from nanoindentation experi- ments. Fracture toughness is evaluated using an equivalent elastic crack energy approach and is compared to macroscale fracture toughness of hydrated cement paste from the literature. The use of nanoindentation for evaluating fracture toughness of concrete constituents might help shedding light on the spatial distribution of fracture toughness in homogenized concrete matrices and the contribution of the different microstructural phases to fracture of concrete.