Revealing the micro-mechanical characteristics of high early strength cement pastes

Abstract

The steam curing has been widely used to enhance the early strength of cement-based materials, while it is generally regarded that the higher early strength would lead to higher brittleness of cement-based materials. Nevertheless, how the enhancement on the early strength of cement-based materials would affect the brittleness is still not clear. This study adopts micro-mechanical indentation and scratch tests to investigate the micro-mechanical characteristics of cement pastes whose early strengths are enhanced by steam curing and the addition of nano-seeding materials. It is found that the fracture toughness of cement paste is identical with that of hydration products, which illustrates that the brittleness of hydration products is essential source to that of cement paste. Especially, with the adopting steam-curing and the addition of C-A-S-H nano-seeds, the early strength of cement paste is enhanced by 63% and 78% respectively, and the fracture toughness of cement paste is increased by 62% and 68% respectively. Moreover, the micro-mechanical properties of hydration products distributed more uniformly in cement paste doped by nano-seeding materials than steam-cured cement paste. Therefore, this study shows that nano-seeding materials is beneficial to the micro-mechanical properties of cement pastes comparing to traditional steam curing.