TY - JOUR A1 - Steindl, Florian Roman A1 - Galan, Isabel A1 - Baldermann, Andre A1 - Sakoparnig, Marlene A1 - Briendl, Lukas G. A1 - Juhart, Joachim A1 - Thumann, Maria A1 - Dietzel, Martin A1 - Röck, Rudolf A1 - Kusterle, Wolfgang A1 - Mittermayr, Florian T1 - Sulfate durability and leaching behaviour of dry- and wet-mix shotcrete mixes JF - Cement and Concrete Research N2 - Shotcrete is a material frequently used in underground constructions such as tunnels, where Ca leaching and sulfate attack are important durability issues. In this study, two test methods were employed to investigate the sulfate resistance and leaching behaviour of dry- and wet-mix shotcretes in sulfate solutions on a time-resolved basis. Tests on powdered samples showed the dissolution of AFm, portlandite and C-A-S-H, subsequently followed by the precipitation of calcite and ettringite. The extent of sulfate expansion of drill cores corresponded to the chemical response of the powder materials, particularly on the reactivity of Ca- and Al-containing hydrated cement phases. The use of high-purity metakaolin (7-10 wt%) in the shotcrete binder significantly decreased the sulfate durability, while high amounts of other SCMs such as blast-furnace slag and silica fume (> 20 wt%) had a positive effect on the durability of shotcrete. KW - ADMIXTURES KW - ALKALI-FREE KW - ATTACK KW - BLAST-FURNACE SLAG KW - concrete KW - Durability KW - Leaching KW - MECHANISM KW - METAKAOLIN KW - RESISTANCE KW - SCMs KW - Shotcrete KW - Sulfate attack KW - TEMPERATURE KW - THAUMASITE FORM Y1 - 2020 U6 - https://doi.org/10.1016/j.cemconres.2020.106180 VL - 137 IS - November SP - 1 EP - 19 PB - Elsevier ER - TY - JOUR A1 - Steindl, Florian R. A1 - Mittermayr, Florian A1 - Sakoparnig, Marlene A1 - Juhart, Joachim A1 - Briendl, Lukas G. A1 - Lindlar, Benedikt A1 - Ukrainczyk, Neven A1 - Dietzel, Martin A1 - Kusterle, Wolfgang A1 - Galan, Isabel T1 - On the porosity of low-clinker shotcrete and accelerated pastes JF - Construction and Building Materials N2 - Although the number and size of interconnected pores have been identified as the most important aspects of concrete microstructure, comprehensive datasets on shotcrete porosity and pore size distributions are still scarce and their key controls are poorly investigated. In this study we investigate the effects of the spraying process, setting accelerator addition and mix design on the microstructure of real-scale dry- and wet-mix shotcrete and hand-mixed and sprayed accelerated pastes. A newly proposed deconvolution analysis of the pore size distributions, measured by mercury intrusion porosimetry, offers increased precision in determining the critical and median pore diameter parameters. In total >50 samples were analysed. Results show that the dry-mix shotcrete exhibits a shift towards coarser pore sizes (∼100–1 μm) than wet-mix shotcrete. Combinations of different supplementary cementitious materials are favourable for producing wet-mix shotcretes with refined pore structures. The addition of setting accelerators, up to 10 wt-% of binder mass, and the spraying process cause systematic variations in the pore volume and pore structure of (sprayed) paste and shotcrete. KW - Porosity KW - Shotcrete KW - Mercury Intrusion KW - Durability KW - SCMs Y1 - 2023 U6 - https://doi.org/10.1016/j.conbuildmat.2023.130461 SN - 0950-0618 VL - 368 PB - Elsevier CY - 14 ER -