Doctoral dissertation explores the impact of alkali carbonate reaction (ACR) on the durability
of cement composites. Therefore, the study utilized dolostone and limestone aggregate as reference
material. The experiments covered various dependent properties relevant to planning durable concrete,
including different aging regimes, various cement types (CEM I and CEM III/B), different water/cement
ratios (0.45 and 0.6), and exposure to different mechanical and chemical degrading mechanisms.
The study observed that ACR enhances the durability of cement composites when subjected to
freeze/thaw cycles and de-icing agents, particularly when aged CEM III/B binder is employed. Chemical
analysis confirmed that hydrotalcite, a byproduct of ACR, reacts spontaneously and exhibits superior
frost resistance compared to limestone counterparts, where hydrotalcite is present in lower
concentrations. Additionally, the improved frost resistance of dolostone composites can be attributed to
the presence of enriched pore solution containing ACR ions, which lower freezing temperature and
potentially enhances durability.
However, when dolostone composites were exposed to sulfates, ACR resulted in reduced durability
compared to reference limestone composites. Chemical analysis revealed the formation of secondary
sulfate products that negatively impacted the mechanical properties of dolostone composites.
Furthermore, the processes influencing the setting time of concrete when recycled aggregate is
incorporated were investigated. Chemical analysis revealed a complex composition of the aggregate.
Thermodynamic models, chemical analyses, and knowledge about sulfurous species and their impact on
cement composite durability were employed to propose a mechanism affecting the setting time of the
composite. Additionally, recommended concentrations of recycled aggregate that did not affect setting
time were determined. Finally, the dissertation concluded by drawing conclusions about the composite
durability during its service life.
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