Effect of water/cement ratio on micro-nanomechanical properties of the interface between cementitious matrix and steel microfibers in ultra-high performance cementitious composites

Efeito da relação água/cimento nas propriedades micro-nanomecânicas da interface entre matriz cimentícia e microfibras metálicas em materiais cimentícios de ultra-alto desempenho

abstract:

Ultra-high performance concretes with steel microfibers have been studied in depth with the aim of producing more efficient and durable structures. The performance of these materials depends on the characteristics of the interface between microfibers and cementitious matrix. This research investigates the micro-nanomechanical properties of the interfacial transition zone between the steel microfibers and the matrix of ultra-high performance cementitious composite. The effect of the water/cement ratio and distance from the microfiber were analyzed. The results confirm the formation of high-density calcium-silicate-hydrate (HD C-S-H) matrix at higher concentrations than low-density calcium-silicate-hydrate (LD C-S-H) for w/c ratios of 0.2 and 0.3. The properties in cementitious matrix interface with steel microfibers were very similar to that measured for the cement paste, and no significant difference was observed regarding the distance to the microfibers in relation to the elastic modulus, hardness and chemical composition. Thus, the authors can conclude that the formation of a less resistant region does not occur at the interfacial transition zone cement paste/microfibers.

Keywords:
calcium-silicate-hydrate; ultra-high performance concrete; interfacial transition zone; steel microfibers; nanoindentation