@article{SakoparnigGalanKusterleetal., author = {Sakoparnig, Marlene and Galan, Isabel and Kusterle, Wolfgang and Lindlar, Benedikt and Koraimann, G{\"u}nther and Angerer, Thomas and Steindl, Florian Roman and Briendl, Lukas G. and Jehle, Sebastian and Flotzinger, Johannes and Juhart, Joachim and Mittermayr, Florian}, title = {On the significance of accelerator enriched layers in wet-mix shotcrete}, series = {Tunnelling and Underground Space Technology}, volume = {131}, journal = {Tunnelling and Underground Space Technology}, publisher = {Elsevier}, doi = {10.1016/j.tust.2022.104764}, pages = {1 -- 10}, abstract = {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.}, language = {en} } @inproceedings{SteindlGalanBaldermannetal., author = {Steindl, Florian and Galan, Isabel and Baldermann, Andre and Sakoparnig, Marlene and Dietzel, Martin and R{\"o}ck, Rudolf and Kusterle, Wolfgang and Mittermayr, Florian}, title = {Dauerhaftigkeitsuntersuchungen an Trocken- und Nassspritzbetonen mit mineralischen Zusatzstoffen - Investigations on the durability of dry- and wet-mix sprayed concrete with mineral additions}, series = {Spritzbeton-Tagung 2021, 21. + 22. J{\"a}nner 2021, Alpbach Tirol}, booktitle = {Spritzbeton-Tagung 2021, 21. + 22. J{\"a}nner 2021, Alpbach Tirol}, pages = {94 -- 111}, abstract = {Die Dauerhaftigkeit von Spritzbeton kann, insbesondere in seiner Verwendung als St{\"u}tz-und Ausbaumaterial im Tunnelbau, durch chemische Angriffe deutlich herabgesetzt werden. Im Forschungsprojekt "Entwicklung neuer dauerhafter und nachhaltiger Spritzbetone (ASSpC)" wurden Pr{\"u}fk{\"o}rper von Trocken-und Nassspritzbetonen in Großspritzversuchen hergestellt. Der Sulfatwiderstand und das L{\"o}sungsverhalten der Betone in sulfathaltigen w{\"a}ssrigen L{\"o}sungen wurden mit drei Testverfahren bestimmt und die Ergebnisse miteinander verglichen: Ein Pulvertestverfahren zeigt die Aufl{\"o}sung 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 bez{\"u}glich der Reaktivit{\"a}t von calcium-und aluminium-haltigen Hydratphasen. Der Thaumasitwiderstand, ermittelt {\"u}ber Masseverlust von Pr{\"u}f-k{\"o}rpern, zeigte eine weitgehende {\"U}bereinstimmung mit den zuvor genannten Tests. Die Verwendung von hochreinen Metakaolinen (7-10 M-\% des Bindemittels) oder Feinstcalcit (5-10 M-\% des Bindemittels) allein f{\"u}hrte insgesamt zu deutlich geringerer Sulfatbest{\"a}ndigkeit. Hingegen konnten hohe Gehalte an H{\"u}ttensand oder Silikastaub auch in Kombination mit Metakaolin und Feinstcalcit den Sulfatwiderstand von Spritzbeton erh{\"o}hen. 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.}, language = {de} } @inproceedings{GalanGarciaStauffacherMittermayretal., author = {Galan Garcia, Isabel and Stauffacher, Anina and Mittermayr, Florian and Thumann, Maria and Kusterle, Wolfgang and Juilland, Patrick and Stenger, Christian and Lindlar, Benedikt}, title = {Estudio de las reacciones de hidrataci{\´o}n temprana en el hormig{\´o}n proyectado}, series = {HAC2018 - V Congreso Iberoamericano de Hormig{\´o}n Autocompactable y Hormigones Especiales ; Valencia 05.03.2018 - 06.03.2018}, booktitle = {HAC2018 - V Congreso Iberoamericano de Hormig{\´o}n Autocompactable y Hormigones Especiales ; Valencia 05.03.2018 - 06.03.2018}, publisher = {Universitat Polit{\`e}cnica Val{\`e}ncia}, isbn = {9788490485910}, doi = {10.4995/hac2018.2018.6907}, abstract = {El hormig{\´o}n proyectado es un tipo de hormig{\´o}n especial utilizado como soporte de rocas durante la construcci{\´o}n de t{\´u}neles y excavaci{\´o}n de minas, entre otras aplicaciones. Las principales caracter{\´i}sticas de este tipo de hormig{\´o}n son el fraguado r{\´a}pido y el desarrollo de una muy alta resistencia mec{\´a}nica a edades tempranas, lo cual permite que el hormig{\´o}n se fije a la base sin necesidad de un soporte extra, endureci{\´e}ndose en pocos minutos. Las reacciones de hidrataci{\´o}n que ocurren en las primeras horas en el hormig{\´o}n proyectado determinan el desarrollo de las propiedades mec{\´a}nicas y su estudio es de crucial importancia para entender y optimizar el comportamiento de este tipo de hormigones. El estudio de estas reacciones, sin embargo, resulta relativamente complicado por varias razones: (i) el hormig{\´o}n proyectado endurece muy r{\´a}pido, lo cual dificulta su manejo durante los ensayos experimentales, y (ii) composiciones similares mezcladas en el laboratorio no se comportan de forma similar a las proyectadas. En este trabajo se presenta una metodolog{\´i}a experimental desarrollada para el estudio de las reacciones de hidrataci{\´o}n que ocurren en el hormig{\´o}n proyectado durante las primeras horas y su correlaci{\´o}n con la resistencia mec{\´a}nica.}, language = {es} } @inproceedings{GalanThumannBriendletal.2018, author = {Galan, Isabel and Thumann, Maria and Briendl, Lukas G. and R{\"o}ck, Rudolf and Steindl, Florian and Juhart, Joachim and Mittermayr, Florian and Kusterle, Wolfgang}, title = {From Lab Scale Spraying to Real Scale Shotcreting and back to the Lab}, series = {8th International Symposium on Sprayed Concrete : Modern Use of Wet Mix Sprayed Concrete for Underground Support - Trondheim, Norwegen. - 11. - 14.06.2018}, booktitle = {8th International Symposium on Sprayed Concrete : Modern Use of Wet Mix Sprayed Concrete for Underground Support - Trondheim, Norwegen. - 11. - 14.06.2018}, editor = {Beck, Thomas and Myren, Synn{\o}ve A. and Engen, Siri}, isbn = {978-82-8208-060-6}, pages = {139 -- 153}, year = {2018}, abstract = {Before new mixes are sprayed in real scale applications, lab experiments have to be carried out to provide a basis for predicting a good performance in real scale. In many cases, to understand the correlations between the behavior in the lab and in real scale spraying, a further set of experiments after the real spraying is required. In this paper we present such a two way process for two new wet mixes, one with a very low tricalcium aluminate Portland cement and the other one with a CEM I with addition of ultra-fine calcite. Calorimetry and Shear-Modulus measurements were used in the lab to monitor hydration evolution. In the real scale spraying compressive strength was measured at periodic intervals up to 24 hours. The hydration of the sprayed samples was stopped at 3, 6 and 24 hours and samples were scanned with X-ray for the identification and quantification of the phases present. The results presented are used to discuss the extent to which lab experiments can predict the behavior of mixes in real scale and how small changes in the raw materials and the mixes can lead to quite different results.}, language = {en} } @inproceedings{StauffacherGalanJuillandetal., author = {Stauffacher, Anina and Galan, Isabel and Juilland, Patrick and Thumann, Maria and Stenger, Christian and Baldermann, Andre and Mittermayr, Florian and Lindlar, Benedikt and Kusterle, Wolfgang}, title = {Einfluss von H{\"u}ttensand und ultrafeinem Kalksteinmehl auf die Hydratation von jungem Spritzbeton}, series = {Spritzbeton-Tagung 2018, Alpbach, Tirol, 11. und 12. Januar 2018. Tagungsbeitr{\"a}ge. CD-ROM}, booktitle = {Spritzbeton-Tagung 2018, Alpbach, Tirol, 11. und 12. Januar 2018. Tagungsbeitr{\"a}ge. CD-ROM}, editor = {Kusterle, Wolfgang}, address = {Oberperfuss}, subject = {Spritzbeton}, language = {de} } @article{SteindlMittermayrSakoparnigetal., author = {Steindl, Florian R. and Mittermayr, Florian and Sakoparnig, Marlene and Juhart, Joachim and Briendl, Lukas G. and Lindlar, Benedikt and Ukrainczyk, Neven and Dietzel, Martin and Kusterle, Wolfgang and Galan, Isabel}, title = {On the porosity of low-clinker shotcrete and accelerated pastes}, series = {Construction and Building Materials}, volume = {368}, journal = {Construction and Building Materials}, publisher = {Elsevier}, address = {14}, issn = {0950-0618}, doi = {10.1016/j.conbuildmat.2023.130461}, abstract = {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.}, language = {en} } @inproceedings{ThumannJuhartRoecketal., author = {Thumann, Maria and Juhart, Joachim and R{\"o}ck, Rudolf and Saxer, Andreas and Galan, Isabel and Mittermayr, Florian and Kusterle, Wolfgang}, title = {Entwicklung neuer, dauerhafter und nachhaltiger Spritzbetone}, series = {Kolloquium Forschung \& Entwicklung f{\"u}r Zement und Beton 2018}, booktitle = {Kolloquium Forschung \& Entwicklung f{\"u}r Zement und Beton 2018}, pages = {65 -- 69}, language = {de} }