Influence of microstructure and cement formulation on stiffness and fatigue behavior of cementitious materials

Abstract

This master’s thesis investigates the influence of microstructural aspects and cement formulations, particularly with the incorporation of supplementary cementitious materials (SCMs), on stiffness and fatigue behavior of cementitious materials. The contributions are formatted as three scientific papers. Firstly, (i) an investigation of the glass powder (GP) influence as a SCM on the mechanical, physical and microstructural behavior of mortars is presented. The results show improvements in several aspects, including heat of hydration, porosity, and strength parameters. The sustainability also had significant improvement, demonstrating the GP a feasible SCM addition for cementitious materials. Secondly, (ii) a characterization method that accounts for the viscoelasticity of cementitious materials is proposed. This method led to accurate and consistent findings when assessing the complex modulus of cementitious materials. Finally, in the third paper, (iii) the influence of microstructure and SCM additions on mechanic, quasi-static and fatigue behavior is addressed. The findings demonstrate that the improved microstructural results, such as low heat of hydration, denser pore size structures, and higher CSH content, for example, were aligned with a lower cracks’ incidence and microstructural voids (up to 61.58%), higher absolute value of complex modulus (up to 24%), lower phase angle (up to 0.56° in average), and improved endurance limit by 19.80%. It is possible to address the influence of those aspects on mechanical behavior and fatigue resistance. Additionally, methods were proposed for mechanical characterization and fatigue tests in pure compression and tension, as well as for data processing the results. Those validations demonstrated their consistency, resulting in accurate measures and in agreement with the literature of complex modulus. This research provides a more comprehensive perspective on fatigue, accounting for feasible optimization parameters on the microstructure and SCMs incorporation, promoting the development of more resistant, durable, and sustainable cementitious materials.