Influence of thermally activated artificial concrete fines composition on concrete long-term behavior

Thermal activation of concrete fines is a promising method for the simultaneous reduction of
CO2 emissions and mineral waste. Hydrated cement paste, a major component of these recycled
materials, can be used as a reactive supplementary cementitious material after dehydration
at elevated temperatures and grinding. This affects concrete strength, especially when fines
contain a higher proportion of aggregates. While strength loss can be mitigated by adjusting
the water-binder ratio, the combined effect on other mechanical properties and durability
remains unclear. This study utilizes seven different artificial concrete fines with varying
binder compositions, aggregate contents, and aggregate mineralogies to produce concrete with
varying compressive strengths. These concretes are then assessed for their flexural strength,
elastic modulus, shrinkage, water absorption, chloride diffusion, carbonation, and freeze-thaw-
resistance. Results highlight that with increasing compressive strength, mechanical properties
and durability also improve. However, while strength development and the elastic modulus are
similar to the reference concrete, the substitution of Portland cement through activated fines
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increases shrinkage as well as carbonation and chloride ingress, especially for fines with a high
amount of reactive SiO2.