Abstract
Most of the previous research on recycled concrete aggregates (RCA) has focused on coarse RCA (CRCA), while much less has been accomplished on the use of fine RCA particles (FRCA). Furthermore, most RCA research disregards its unique microstructure, and thus the inferior performance of concrete incorporating RCA is often reported in the fresh and hardened states. To improve the overall behaviour of RCA concrete advanced mix design techniques such as equivalent volume (EV) or particle packing models (PPMs) may be used. However, the efficiency of these procedures to proportion eco-efficient FRCA concrete still requires further investigation. This work evaluates the overall fresh (i.e., slump and rheological characterization) and hardened states (i.e., non-destructive tests, compressive strength and microscopy) performance of sustainable FRCA mixtures proportioned through distinct techniques (i.e., direct replacement, EV and PPMs) and incorporating different types of aggregates (i.e., natural and manufactured sand) and manufacturing processes (i.e., crusher fines and fully ground). Results demonstrate that the aggregate type and crushing process may influence the FRCA particles’ features. Yet, the use of advanced mix design techniques, particularly PPMs, may provide FRCA mixes with quite suitable performance in the fresh (i.e., 49% lower yield stress) and hardened states (i.e., 53% higher compressive strength) along with a low carbon footprint.
Highlights
Concrete is a widely used material for critical infrastructure worldwide; over 10 billion tons of concrete are produced annually in the modern industrial society [1]
One of the earliest attempts to use a mix proportion of recycled concrete aggregates (RCA) concrete was performed through direct replacement methods (DRMs), which can be conducted by weight or volume
It is important to notice that due to the torque limitations of the IBB rheometer used for the analysis, the DRM mixtures could not be investigated since they pre
Summary
Concrete is a widely used material for critical infrastructure worldwide; over 10 billion tons of concrete are produced annually in the modern industrial society [1]. One of the earliest attempts to use a mix proportion of RCA concrete was performed through direct replacement methods (DRMs), which can be conducted by weight or volume. This approach treats RCA as homogeneous material and partially replaces a certain amount of natural aggregates accounting for their distinct microstructure and or the presence of RM [33,34]. DRM techniques often result in recycled concrete mixtures with similar fresh-state behaviour Still, it is quite inferior hardened-state performance compared to a companion CC mix, especially when moderate to high amounts of RCA is used [35].
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