TY - JOUR A1 - Sakoparnig, Marlene A1 - Galan, Isabel A1 - Steindl, Florian Roman A1 - Kusterle, Wolfgang A1 - Juhart, Joachim A1 - Grengg, Cyrill A1 - Briendl, Lukas G. A1 - Saxer, Andreas A1 - Thumann, Maria A1 - Mittermayr, Florian T1 - Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration JF - Materials and structures N2 - The reduction of clinker use is mandatory to lower the negative environmental impact of concrete. In shotcrete mixes, similarly to the case of conventional concrete, the use of supplementary cementitious materials (SCMs) and proper mix design allow for the substitution of clinker without compromising the mechanical properties. However, the impact of the substitution on the durability of shotcrete needs to be further assessed and understood. The results from the present study, obtained from real-scale sprayed concrete applications, show a reduction of the Ca2+ leaching and sintering potential of clinker-reduced shotcrete mixes due to the presence of SCMs. This positive effect, crucial for low maintenance costs of tunnels, is mainly related to a reduced portlandite content, which on the other hand negatively affects the carbonation resistance of shotcrete. Additionally, the hydration of SCMs positively influences the chloride penetration resistance presumably due to a combination of microstructural changes and changes in the chloride binding capacity. Differences found in the pore size distribution of the various mixes have low impact on the determined durability parameters, in particular compared to the effect of inhomogeneities produced during shotcrete application. KW - Carbonate precipitation KW - Carbonation KW - Chloride penetration KW - Durability KW - Leaching KW - Shotcrete Y1 - 2021 U6 - https://doi.org/10.1617/s11527-021-01644-7 VL - 54 SP - 1 EP - 23 PB - Springer Nature ER - 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 -