Microscopic characterization of alkali-silica reaction (ASR) affected recycled concrete mixtures induced by reactive coarse and fine aggregates

TROTTIER, CASSANDRA; ZIAPOUR, ROUZBEH; ZAHEDI, ANDISHEH; SANCHEZ, LEANDRO; LOCATI, F.

Lisboa

Congreso; 16th International Conference on Alkali-Aggregate Reaction in Concrete; 2022

LABORATÓRIO NACIONAL DE ENGENHARIA CIVIL

The use of recycled concrete aggregates (RCA) is gaining interest in the industry due to the pressure to adopt more sustainable practices yet, concerns regarding the potential for ASR in concrete made with RCA remain. In the current literature, the original extent of the ASR damage is often unknown and therefore, inconsistencies regarding the potential for further ASR in concrete made with affected RCA are observed in the literature [1-4]. RCA is a multi-phase material consisting of the original virgin aggregate (OVA) and RM (i.e., residual sand and cement paste) and ASR may originate from the reactive OVA or residual sand and its extension into the cement paste depends on the extent ofreaction/damage. Consequently, the level and extension of previous damage due to ASR originating from the OVA or residual sand may influence the potential for secondary damage and its nature. This work, therefore, evaluated the secondary damage generation and propagation in concrete made with RCA presenting two levels of initial damage (i.e., 0.05% and 0.30% of expansion, representing a returned and demolished concrete, respectively) induced by either reactive coarse OVA or residual sand. A microscopic tool (i.e., Damage Rating Index - DRI) was used for the analysis while distress features (i.e., cracks) were measured in counts per 100 cm2, length, width and types of propagation to characterize the distinct damage patterns induced by various types of RCA affected by ASR. The full extent of this research can be found in [5].