TY - JOUR A1 - Vanoutrive, Hanne A1 - van den Heede, Philip A1 - Alderete, Natalia A1 - Andrade, Carmen A1 - Bansal, Tushar A1 - Camões, Aires A1 - Cizer, Özlem A1 - de Belie, Nele A1 - Ducman, Vilma A1 - Etxeberria, Miren A1 - Frederickx, Lander A1 - Grengg, Cyrill A1 - Ignjatović, Ivan A1 - Ling, Tung-Chai A1 - Liu, Zhiyuan A1 - Garcia-Lodeiro, Inés A1 - Lothenbach, Barbara A1 - Medina Martinez, César A1 - Sanchez-Montero, Javier A1 - Olonade, Kolawole A1 - Palomo, Angel A1 - Phung, Quoc Tri A1 - Rebolledo, Nuria A1 - Sakoparnig, Marlene A1 - Sideris, Kosmas A1 - Thiel, Charlotte A1 - Visalakshi, Talakokula A1 - Vollpracht, Anya A1 - von Greve-Dierfeld, Stefanie A1 - Wei, Jinxin A1 - Wu, Bei A1 - Zając, Maciej A1 - Zhao, Zengfeng A1 - Gruyaert, Elke T1 - Report of RILEM TC 281-CCC: outcomes of a round robin on the resistance to accelerated carbonation of Portland, Portland-fly ash and blast-furnace blended cements JF - Materials and Structures N2 - Many (inter)national standards exist to evaluate the resistance of mortar and concrete to carbonation. When a carbonation coefficient is used for performance comparison of mixtures or service life prediction, the applied boundary conditions during curing, preconditioning and carbonation play a crucial role, specifically when using latent hydraulic or pozzolanic supplementary cementitious materials (SCMs). An extensive interlaboratory test (ILT) with twenty two participating laboratories was set up in the framework of RILEM TC 281-CCC 'Carbonation of Concrete with SCMs'. The carbonation depths and coefficients determined by following several (inter)national standards for three cement types (CEM I, CEM II/B-V, CEM III/B) both on mortar and concrete scale were statistically compared. The outcomes of this study showed that the carbonation rate based on the carbonation depths after 91 days exposure, compared to 56 days or less exposure duration, best approximates the slope of the linear regression and those 91 days carbonation depths can therefore be considered as a good estimate of the potential resistance to carbonation. All standards evaluated in this study ranked the three cement types in the same order of carbonation resistance. Unfortunately, large variations within and between laboratories complicate to draw clear conclusions regarding the effect of sample pre-conditioning and carbonation exposure conditions on the carbonation performance of the specimens tested. Nevertheless, it was identified that fresh and hardened state properties alone cannot be used to infer carbonation resistance of the mortars or concretes tested. It was also found that sealed curing results in larger carbonation depths compared to water curing. However, when water curing was reduced from 28 to 3 or 7 days, higher carbonation depths compared to sealed curing were observed. This increase is more pronounced for CEM I compared to CEM III mixes. The variation between laboratories is larger than the potential effect of raising the CO2 concentration from 1 to 4%. Finally, concrete, for which the aggregate-to-cement factor was increased by 1.79 in comparison with mortar, had a carbonation coefficient 1.18 times the one of mortar. Supplementary Information The online version contains supplementary material available at 10.1617/s11527-022-01927-7. Y1 - 2022 U6 - https://doi.org/10.1617/s11527-022-01927-7 VL - 55 IS - 3 SP - 1 EP - 29 PB - Springer ER - TY - CHAP A1 - Sakoparnig, Marlene A1 - Galan, Isabel A1 - Balderman, Andre A1 - Steindl, Florian A1 - Dietzel, Martin A1 - Thumann, Maria A1 - Saxer, Andreas A1 - Kusterle, Wolfgang A1 - Mittermayr, Florian T1 - Experimental Ca leaching of shotcrete & secondary precipitation T2 - ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik Y1 - 2019 UR - https://iccc-online.org/fileadmin/gruppen/iccc/proceedings/ICCC15_2019.pdf SP - 3488 EP - 3495 ER - TY - CHAP A1 - Sakoparnig, Marlene A1 - Baldermann, Andre A1 - Thumann, Maria A1 - Mittermayr, Florian A1 - Kusterle, Wolfgang T1 - Bestimmung der experimentellen Calcium-Auslaugung an Spritzbetonbohrkernen: Methodenvergleich und Update T2 - Spritzbeton-Tagung 2018, Alpbach, Österreich 11.-12.01.2018 N2 - Im Rahmen des FFG-Forschungsprojektes „Entwicklung neuer dauerhafter und nachhaltiger Spritzbetone (Advanced and sustainable sprayed concrete; ASSpC)“ werden Methoden zur Prüfung der Calcium-Auslaugung von Spritzbeton eingesetzt bzw. weiterentwickelt. Bestimmt wurde dafür das Reduzierte Versinterungspotential nach Regelwerken der Österreichischen Bautechnik Vereinigung und das Auslaugverhalten von Spritzbeton bei leichtem Säureangriff (Salpetersäure und Kohlensäure), um dauerhaftigkeitsrelevante Parameter im Bereich der Wechselwirkungen von Spritzbeton mit leicht sauren (Kohlensäure- und Nitrathaltigen) Oberflächen-, Grund- und Sickerwässern zu untersuchen und potentielle Schädigungsmechanismen zu identifizieren und zu quantifizieren. Die Vor- und Nachteile der verwendeten Prüfmethoden zum lösenden Angriff werden in Bezug auf die Dauerhaftigkeit von Spritzbeton diskutiert. T2 - DIFFERENT EXPERIMENTAL APPROACHES TO STUDY CA-LEACHING IN SPRAYED CONCRETE: COMPARISON OF METHODS AND UPDATE Y1 - 2018 UR - http://www.spritzbeton-tagung.com/downloads/vortraege/2018/11_Sakoparnig_et_al_Methodenvergleich_Calcium-Auslaugung_an_Spritzbeton-Bohrkernen.pdf ER - TY - CHAP A1 - Steindl, Florian A1 - Galan, Isabel A1 - Baldermann, Andre A1 - Sakoparnig, Marlene A1 - Dietzel, Martin A1 - Röck, Rudolf A1 - Kusterle, Wolfgang A1 - Mittermayr, Florian T1 - Dauerhaftigkeitsuntersuchungen an Trocken- und Nassspritzbetonen mit mineralischen Zusatzstoffen - Investigations on the durability of dry- and wet-mix sprayed concrete with mineral additions T2 - Spitzbeton-Tagung 2021, 21. + 22. Jänner 2021, Alpbach Tirol N2 - Die Dauerhaftigkeit von Spritzbeton kann, insbesondere in seiner Verwendung als Stütz-und Ausbaumaterial im Tunnelbau, durch chemische Angriffe deutlich herabgesetzt werden. Im Forschungsprojekt "Entwicklung neuer dauerhafter und nachhaltiger Spritzbetone (ASSpC)" wurden Prüfkörper von Trocken-und Nassspritzbetonen in Großspritzversuchen hergestellt. Der Sulfatwiderstand und das Lösungsverhalten der Betone in sulfathaltigen wässrigen Lösungen wurden mit drei Testverfahren bestimmt und die Ergebnisse miteinander verglichen: Ein Pulvertestverfahren zeigt die Auflösung von Zementhydratphasen zugunsten der Neubildung von Calcit und Ettringit. Das Ausmaß der Sulfatdehnung an Bohrkernen, ermittelt im zweiten Testverfahren, korrespondiert mit dem chemischen Verhalten des gemahlenen Materials, insbesondere bezüglich der Reaktivität von calcium-und aluminium-haltigen Hydratphasen. Der Thaumasitwiderstand, ermittelt über Masseverlust von Prüf-körpern, zeigte eine weitgehende Übereinstimmung mit den zuvor genannten Tests. Die Verwendung von hochreinen Metakaolinen (7-10 M-% des Bindemittels) oder Feinstcalcit (5-10 M-% des Bindemittels) allein führte insgesamt zu deutlich geringerer Sulfatbeständigkeit. Hingegen konnten hohe Gehalte an Hüttensand oder Silikastaub auch in Kombination mit Metakaolin und Feinstcalcit den Sulfatwiderstand von Spritzbeton erhöhen. The durability of shotcrete can be degraded by chemical attacks, especially if used as ground support in tunnel construction. In the course of the research project "Advanced and Sustainable Sprayed Concrete (ASSpC)" test specimens of dry-mix and wet-mix shotcrete were sprayed in large-scale tests. The sulfate resistance and the leaching behaviour of these shotcretes were assessed in sulfate-bearing solutions. A test procedure based on the use of shotcrete powders shows that hydrated cement phases dissolve in favour of calcite and ettringite neo-formation. The sulfate expansion measured on drill cores in the second procedure corresponds to the behaviour of the powders, especially regarding the reactivity of calcium-and aluminium-bearing hydrated phases. The resistance against thaumasite attack, assessed by measuring the mass loss of prisms, coincides with the former test results. The exclusive use of high-purity metakaolin (7-10 wt-% of binder) or fine calcium carbonate (5-10 wt-% of binder) leads to a decrease in the sulfate durability. However, high amounts of blast furnace slag or silica fume can increase the sulfate resistance of shotcrete even when used in combination with metakaolin or fine calcium carbonate. Y1 - 2021 UR - https://www.spritzbeton-tagung.com/downloads/vortraege/2021/17_Steindl.pdf SP - 94 EP - 111 ER - TY - JOUR A1 - Steindl, Florian Roman A1 - Sakoparnig, Marlene A1 - Briendl, Lukas G. A1 - Thumann, Maria A1 - Galan, Isabel A1 - Juhart, Joachim A1 - Röck, Rudolf A1 - Saxer, Andreas A1 - Mittermayr, Florian A1 - Kusterle, Wolfgang T1 - ASSpC – Vier Jahre Forschung für dauerhaften Spritzbeton JF - Bautechnik Y1 - 2020 PB - Wilhelm Ernst & Sohn CY - Berlin ER - TY - JOUR A1 - Sakoparnig, Marlene A1 - Galan, Isabel A1 - Kusterle, Wolfgang A1 - Lindlar, Benedikt A1 - Koraimann, Günther A1 - Angerer, Thomas A1 - Steindl, Florian Roman A1 - Briendl, Lukas G. A1 - Jehle, Sebastian A1 - Flotzinger, Johannes A1 - Juhart, Joachim A1 - Mittermayr, Florian T1 - On the significance of accelerator enriched layers in wet-mix shotcrete JF - Tunnelling and Underground Space Technology N2 - The application process, which gives shotcrete its name is a robust and established method, dating back to the beginning of the 20th century. Since then, the spraying process has been significantly enhanced. However, during the last decades no major technical changes have been made. In this study the wet - mix shotcrete process including the dosing of accelerator was investigated. For this, we monitored the concrete and accelerator pressure with 5 sensors in the pumps and pipes, and analysed the accelerator distribution in the hardened shotcrete matrix. The recorded pressure fluctuations clearly indicated that the pumping of the concrete with a double-piston pump led to flow pulsations. The pressure along the accelerator pipes, controlled by a peristaltic pump, was not steady either. However, the accelerator flow pulsation had a higher frequency than that of the concrete flow. This misalignment led to changes in the accelerator to concrete ratio during the spraying process. The impact of these incongruent concrete and accelerator flows on the resulting hardened shotcrete was visually analysed with the use of 0.02 % uranin as fluorescent tracer added to the accelerator. The tracer distribution showed that changes in the accelerator/concrete ratio led to the formation of ‘accelerator layers’, layers with higher accelerator concentrations in the hardened shotcrete. These layers show differences in chemistry, mineralogy and open porosity compared to the rest of the shotcrete matrix. The presence of accelerator enriched layers can have detrimental effects on the shotcrete properties, especially affecting the durability and mechanical performance. In consequence, we recommend a revision of the shotcrete process to eliminate these inhomogeneities. KW - Inhomogeneities KW - Pulsation KW - Concrete pumping KW - Layering KW - Accelerator KW - Shotcrete Y1 - 2023 U6 - https://doi.org/10.1016/j.tust.2022.104764 VL - 131 SP - 1 EP - 10 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 - 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 - 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 -