Efeito de diferentes teores de resíduo de gesso sobre o ataque interno por sulfato em argamassas incorporando agregados reciclados de concreto (ARC) ou misto (ARM)

Abstract

There is a growing need to find more sustainable alternatives to produce and use building materials that reduce environmental impacts. These impacts may be related to the extraction of natural resources or the disposal of waste in inappropriate places. The study on the use of construction and demolition waste (CDW) as aggregate is in the process of consolidation however, there is still information to be explored about the effects of these waste on the microstructure of cement composites. In this context, the presence of gypsum as a contaminant in these aggregates is a matter of interest, since gypsum can be a relevant factor in the study of internal sulfate attack and a limiting factor to the use of CDW aggregates. The main objective of this research was to propose a conceptual model of the behavior of Portland cement mortars when produced with CDW contaminated by different levels of gypsum waste. The properties of the mortars in the fresh and hardened state, with different particle size distribution, typology and gypsum waste contents were analyzed. Studied the relationship between CDW aggregate contaminated with different gypsum waste contents and the effect of internal sulfate attack. The interaction between secondary ettringite crystal formation, damage formation and the porous distribution of the system was evaluated. The study demonstrated that mortars produced with CDW aggregates have the potential to form secondary ettringite, regardless of the added content of contaminant. It also demonstrated that the formation of damage depends on the porous distribution of the system and the location of formation of the ettringite crystals, indicating a possible flexibility in relation to the limits stipulated by the standard.