20.500.12556/RUL-190742 Insights from historical ACR-affected concrete freeze–thaw resistance under chloride exposure This study investigates how mineralogical and microstructural alterations associated with alkali–carbonate reaction (ACR) may influence the salt–frost resistance of approximately 90-year-old concrete from the Rupnik Military Line. Historical limestone- and dolostone-aggregate concretes (HCL and HCD) were compared with laboratory-prepared counterparts made with CEM III/B cement and aged for six months in 1 M NaOH at 60 °C (LC3NH60 and RC3NH60). The specimens underwent freeze– thaw cycling while immersed in 3% NaCl. Mass loss and dynamic modulus were monitored, compressive strength was determined for the laboratory series, and post-exposure phases were characterised by XRD and SEM–EDS. The historical concretes deteriorated substantially more than the laboratory-prepared specimens and exhibited pronounced within-group variability. After 25 cycles, mean mass losses were 71.2% for HCL and 47.7% for HCD, whereas after 30 cycles they were approximately 1.33% for LC3NH60 and 0.62% for RC3NH60. Thus, the dolostone-containing concrete showed lower mean mass loss in both series, although the historical HCL–HCD difference should be interpreted as a descriptive trend. RC3NH60 retained its compressive strength, while neither laboratory mixture exhibited a progressive strength loss. Dynamic-modulus values for severely scaled historical specimens primarily described the ultrasonic response of the remaining cross-section and did not independently demonstrate the absence of internal deterioration. Post-exposure analyses identified a greater relative abundance of monocarboaluminate in the limestone-containing concretes and of hydrotalcite- like phases in the dolostone-containing concretes, together with chloride-bearing AFm phases. These associations are consistent with possible effects of ACR-related evolution on chloride interaction and freezing behaviour, but the mechanisms were not measured directly or isolated from aggregate mineralogy, binder chemistry and pore structure. ACR did not necessarily imply reduced durability under the investigated conditions. Accelerated ageing produced relevant dedolomitisation-related phases and provided a useful controlled reference, but it neither reproduced the complete evolution of the historical concrete nor established that ACR is generally beneficial civil engineering historical concrete freeze-thaw resistance chloride exposure alkali–carbonate reaction (ACR) accelerated ageing dolostone aggregate durability gradbeništvo historičen beton odpornost proti zmrzovanju in tajanju izpostavljenost kloridom alkalno-karbonatna reakcija (ACR) pospešeno staranje dolomitni agregat obstojnost true false false Angleški jezik Slovenski jezik Članek v reviji 2026-11-02 16:12:19 2026-11-02 16:12:31 2026-11-03 04:08:30 0000-00-00 00:00:00 2026 0 0 19 STR. iss. oct., art. 431 Vol. 59 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 691 1359-5997 10.1617/s11527-026-03315-x 303499011 s11527-026-03315-x_(1).pdf s11527-026-03315-x_(1).pdf 1 47C9220CFF6DA38F83223879FE2CDBA3 bdad523ba6104ac29190f66939f4701e46266c1611454ff134cfc6ab81b31def 1755b5d7-d6d0-11f1-aea2-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=252339 https://link.springer.com/article/10.1617/s11527-026-03315-x 1 c79f2ff0-d6cf-11f1-aea2-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=252338 Fakulteta za gradbeništvo in geodezijo Fakulteta za kemijo in kemijsko tehnologijo 0 0 0