20.500.12556/RUL-182501 Vpliv izbranega dolomitnega agregata na lastnosti svežega in obstojnost strjenega betona doktorska disertacija Impact of dolomite aggregate on the properties of fresh and durability of hardened concrete doctoral dissertation V doktorski disertaciji smo raziskovali vpliv alkalno karbonatne reakcije (ACR) na obstojnost cementnih kompozitov. Za namen študije smo uporabili dolomitni agregat in referenčni apnenčev agregat. Poskuse smo izvajali pri različnih starostih kompozitov, različnem cementu (CEM I in CEM III/B), različnem vodocementnem razmerju (0,45 in 0,6) in izpostavljenosti različnim mehanskim in kemijskim dejavnikom (zmrzovanje in tajanje v prisotnosti talilne soli, sulfatni napad ob prisotnosti sušenja in vlaženja ter kislinski sulfatni napad). Ugotovili smo, da alkalno karbonatna reakcija pozitivno vpliva na obstojnost cementnih kompozitov v primeru zmrzovanja in tajanja in prisotnosti talilnih soli, pri čemer so se kot najbolj obstojni izkazali pospešeno starani dolomitni kompoziti s CEM III/B cementom. S kemijskimi analizami smo ugotovili, da je pri betonu z alkalno karbonatno reakcijo tvorba hidrotalcita kemijsko spontanejša reakcija, ta pa povzroči njegovo boljšo obstojnost. Ugotovili smo tudi, da lahko zasičenost porne raztopine z ioni, ki so posledica ACR, pripomore k zmanjšanju temperature zmrzovanja, kar ravno tako pomembno doprinese k njegovi boljši obstojnosti. Pri izpostavljenosti dolomitnih kompozitov sulfatnemu napadu in kislinskemu sulfatnemu napadu pa so se le ti izkazali kot manj obstojni v primerjavi z apnenčevimi kompoziti. Do tega je prišlo zaradi tvorbe sekundarnih sulfatnih produktov, ki so oslabili mehanske lastnosti kompozitov. Preverjali smo tudi vpliv recikliranega agregata na lastnosti sveže betonske mešanice in s kemijskimi analizami ugotovili njegovo kompleksno sestavo. S pomočjo termodinamskih modelov in kemijskih analiz ter poznavanja vpliva žveplovih spojin na obstojnost kompozitov smo lahko predpostavili mehanizem, ki vpliva na podaljšan čas vezanja cementnega kompozita, določili primerno koncentracijo agregata, ki nima vpliva na hitrost vezanja ter predpostavili njegovo obstojnost v njegovem življenjskem ciklu. 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. doktorske disertacije grajeno okolje dolomit apnenec agregat beton kloridi sulfati recikliran agregat portland cement žlindrin cement pospešeno staranje obstojnost built environment dolostone limestone aggregate concrete chlorides sulphates recycled aggregate portland cement slag cement accelerated aging durability true false false [T. Turk] Slovenski jezik Angleški jezik Doktorsko delo/naloga 2026-05-14 09:03:38 2026-05-14 09:03:38 2026-05-20 08:04:50 0000-00-00 00:00:00 2025 0 Ljubljana 2025 Ljubljana XXIV, 116 str. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 2027-06-24 666.972.1:691.322(043.3) 179316 240396803 17502.pdf 17502.pdf 1 B711C5D89EBE873B5D5386A325AAF3B1 80c2ddc9e065ccfc866f040ba86edd5b36b3ba90346861efac15e6e9e0307f82 bb57e227-4f62-11f1-b0ab-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=233825 Fakulteta za gradbeništvo in geodezijo 0 0 0