Property investigation of calcium–silicate–hydrate (C–S–H) gel in cementitious composites

•A coupled nanoindentation and scanning electron microscope technique was applied.•The physical and mechanical properties were linked by the proposed model.•The porosity and poroelastic parameters were reported for the first time.•The influence of water to cement ratio was studied.

Calcium–silicate–hydrate (C–S–H) gel, the main product of cement hydration, contributes the most to engineering properties of concrete. Hence, the microstructural physical and mechanical properties of C–S–H gel present in cementitious composites were investigated by the coupled nanoindentation and scanning electron microscope analysis. The physical and mechanical properties were linked through the micro-poromechanical approach. Through this study, an insight was provided into the microstructural features of C–S–H gel present in cementitious composites. It is found that C–S–H gel is a multi-scale composite composed of C–S–H solid, pore and intermixtures at the scale of nanoindentation on C–S–H gel, and the physical and mechanical properties of C–S–H gel can be influenced by the porosity and volume fraction of the intermixtures.