@incollection{LlanoTorreSernaGarciaTaenguaetal., author = {Llano-Torre, Aitor and Serna, Pedro and Garcia-Taengua, Emilio and Vrijdaghs, Rutger and Pauwels, Hans and del Prete, Clementina and Buratti, Nicola and Zerbino, Ra{\´u}l L. and Kusterle, Wolfgang and Stefan Bernard, E.}, title = {Analysis of the RRT Results}, series = {Round-Robin Test on Creep Behaviour in Cracked Sections of FRC: Experimental Program, Results and Database Analysis}, volume = {34}, booktitle = {Round-Robin Test on Creep Behaviour in Cracked Sections of FRC: Experimental Program, Results and Database Analysis}, editor = {Llano-Torre, Aitor and Serna, Pedro}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-030-72735-2}, doi = {10.1007/978-3-030-72736-9_8}, pages = {147 -- 207}, abstract = {The analysis of the results of the round-robin test (RRT) comprised many steps. The variation of the main variables such as the number of samples tested, environmental conditions, pre-crack level or creep index and mechanical performance were analysed among all the RRT participants. In addition, the main methodologies were independently analysed to search significances between the participant procedures. Analysis of the described procedures, test setups and equipment provided relevant information about such existent differences between participants in terms such as load configuration, boundary conditions or frames construction. The creep coefficient and crack opening rate (COR) parameters were defined and analysed. The complementary data number of fibres in the cross section was analysed to assess the influence in the long-term residual performance. Finally, the correlation between different fibre-reinforced concrete (FRC) specimens as well as the influence of ageing of concrete matrix were analysed.}, language = {en} } @inproceedings{Kusterle, author = {Kusterle, Wolfgang}, title = {Flexural Creep Tests on Beams : 8 Years of Experience with Steel and Synthetic Fibres}, series = {Creep Behaviour in Cracked Sections of Fibre Reinforced Concrete : Proceedings of the International RILEM Workshop FRC-CREEP 2016}, booktitle = {Creep Behaviour in Cracked Sections of Fibre Reinforced Concrete : Proceedings of the International RILEM Workshop FRC-CREEP 2016}, isbn = {978-94-024-1001-3}, doi = {10.1007/978-94-024-1001-3_3}, pages = {27 -- 39}, abstract = {The creep of cracked fibre reinforced concrete beams has been investigated by many laboratories. Different testing procedures have been used. Creep-test results prove that cracked beams reinforced by fibres show time dependent deformations and therefore increasing crack width with time. Some cannot sustain a high percentage of post-crack load for an extended period and fail due to creep rupture. Determination of the residual strength of FRC according to the Austrian Guideline Fibre Reinforced Concrete was the starting point for the tests. The beams were first tested under four-point flexural loading up to a deflection of 1.75 mm. The beams were then unloaded and three pre-cracked beams were loaded with a sustained load at various percentages of the load reported at 1.75 mm deflection. The used testing procedure, realized and planned improvements are discussed. Typical creep-time curves of FRC are presented. The load level was increased stepwise. Starting point was 50 \% of the residual load at 1.75 mm deflection. At the load level of 60 \%, beams with several fibre types started deforming faster and the test ended up in a creep failure. An alarming fact is that beams with some fibre-types may fail after 7 years of loading.}, language = {en} } @incollection{KusterleSindersberger, author = {Kusterle, Wolfgang and Sindersberger, Dirk}, title = {Betonfeuchtemodell f{\"u}r Tunnelinnenschalen in {\"O}sterreich (Tunnelfeuchte)}, series = {Forschungsbericht der OTH Regensburg 2016}, booktitle = {Forschungsbericht der OTH Regensburg 2016}, address = {Regensburg}, isbn = {978-3-9818209-1-1}, pages = {64 -- 65}, abstract = {Die Feuchtigkeit in oberfl{\"a}chennahen Schichten der Tunnelinnenschalen ist neben der Temperaturentwicklung und Dehnungsbehinderung maßgebend f{\"u}r das Abplatzverhalten der Schale im Brandfall. Die Feuchte {\"a}ndert sich mit den Umgebungsbedingungen. Die Feuchteverteilungen und {\"A}nderungen {\"u}ber den Jahreszyklus sind derzeit weitgehend unbekannt. Um ein Modell zu entwickeln ist es notwendig anhand zuverl{\"a}ssiger Messdaten einen {\"U}berblick {\"u}ber die Feuchteverteilung in Abh{\"a}ngigkeit des Tunnelklimas zu bekommen. Die Messung in verschiedenen Tiefenstufen im Tunnel und in der Klimakammer erfolgt mit spezifischen Sensoren und Datenerfassungseinheiten. Die Sensoren m{\"u}ssen f{\"u}r den Einsatz im Beton richtig ausgew{\"a}hlt und gesch{\"u}tzt werden. Aufbauend auf diesen realen Messdaten soll dann ein bauphysikalisches Modell entwickelt werden.}, language = {de} } @article{TestorKusterle, author = {Testor, Markus and Kusterle, Wolfgang}, title = {Druckfestigkeitsentwicklung von Spritzbetonen mit alkalifreier Erstarrungsbeschleunigung}, series = {Zement + Beton}, volume = {97}, journal = {Zement + Beton}, number = {3}, publisher = {Zement und Beton Handels- und Werbeges.}, address = {Wien}, issn = {0514-2946}, pages = {20 -- 25}, abstract = {Spritzbetone mit alkalifreier Erstarrungsbeschleunigung werden ohne alkalische Zusatzmittel (Spritz-Bindemittel mit begrenztem Alkaligehalt oder alkalifreiem Erstarrungsbeschleuniger) verarbeitet. Ein entscheidender Punkt fuer den Einsatz der alkalifreien Erstarrungsbeschleunigung ist das geunstige Auslaugverhalten, speziell hinsichtlich der Einbringung von Alkalien in Tunnelwaesser. Diese Spritzbetone zeigen bei Kontakt mit Wasser das gleiche Auslaugverhalten wie Normalbeton. Alkalihaltige Zusatzmittel fuehrten bisher bei unsachgemaesser Anwendung auch zu Veraetzungen der Haut und der Augen (bis zur Erblindung) sowie zu Reizungen der Schleimhaeute. Die arbeitshygienischen und oekologischen Nachteile klassischer alkalihaetiger Erstarrungsbeschleuniger wurden mit der neuen Technologie ueberwunden. Die Festigkeitsentwicklungen von Spritzbetonen mit alkalifreier Erstarrungsbeschleunigung weisen unterschiediche Charakteristika auf und weichen im Festigkeitsverlauf untereinander beziehungsweise gegenueber herkoemmlichen, mit alkalihaltigen Beschleunigern versehenen Spritzbetonen ab. Eine charakteristische Druckfestigkeitsentwicklung zeigen nur Spritzbetone unter Verwendung von Spritz-Bindemitteln fuer den Einsatz mit ofentrockenen Zuschlaegen beziehungsweise Spritz-Bindemittel auch mit naturfeuchten Zuschlaegen.Werden Zemente auf Basis von Portlandzementklinker mit alkalifreiem Erstarrungsbeschleuniger eingesetzt, so sind grosse Unterschiede im Festigkeitsverlauf, primaer abhaengig vom Erstarrungsbeschleunigergehalt und Wasserzement-Wert, sowohl im Trocken- als auch im Nassspritzverfahren feststellbar.}, language = {de} } @article{TestorKusterle, author = {Testor, Markus and Kusterle, Wolfgang}, title = {Vergleichende Staubmessungen bei Spritzbetonarbeiten : Meßmethoden-Einflussfaktoren-Reduktionsm{\"o}glichkeiten}, series = {Felsbau : Fachzeitschrift f{\"u}r Ingenieurgeologie, Geomechanik und Tunnelbau = Rock and soil engineering}, volume = {15}, journal = {Felsbau : Fachzeitschrift f{\"u}r Ingenieurgeologie, Geomechanik und Tunnelbau = Rock and soil engineering}, number = {2}, publisher = {VGE-Verlag}, address = {Essen}, organization = {{\"O}sterreichische Gesellschaft f{\"u}r Geomechanik ({\"O}GG)}, issn = {0174-6979}, pages = {125 -- 133}, language = {de} } @article{FleischmannKusterle, author = {Fleischmann, Florian and Kusterle, Wolfgang}, title = {Neues Rheometer zur Bestimmung der Frischbetoneigenschaften von Selbstverdichtenden Betonen.}, series = {Beton : die Fachzeitschrift f{\"u}r Bau + Technik}, volume = {64}, journal = {Beton : die Fachzeitschrift f{\"u}r Bau + Technik}, number = {9}, publisher = {Verlag Bau + Technik}, address = {Erkrath}, issn = {0005-9846}, pages = {330 -- 337}, language = {de} } @inproceedings{ThumannKusterle, author = {Thumann, Maria and Kusterle, Wolfgang}, title = {Enhanced durability of shotcrete - Reduced potential for precipitations}, series = {Proceedings of the 11th fib International PhD Symposium in Civil Engineering. - 29.-31.08.2016, Tokyo, Japan}, booktitle = {Proceedings of the 11th fib International PhD Symposium in Civil Engineering. - 29.-31.08.2016, Tokyo, Japan}, editor = {Maekawa, Koichi and Kasuga, Akio and Yamazaki, Jun}, publisher = {Technical University of Tokyo}, isbn = {978-4-9909148-0-6}, pages = {221 -- 228}, abstract = {The contact of underground water with shotcrete leads to leaching of calcium hydroxide and can increase the precipitation of calcite in the secondary drainage system of tunnels under certain conditions. Indeed precipitations in the drainage pipes lead to high maintenance costs. Within a research project the leaching behavior of new and innovative binder compositions was tested in lab tests. One possible change in mix-design is the reduction in clinker content by using a lower amount of Ordinary Portland Cement together with cementitious materials. Successful combinations were further investigated in sprayed mortar and shotcrete tests to examine the influences of the spraying process and the addition of accelerator. The results indicate how shotcrete mix-design can be improved regarding its potential for precipitations and subsequently enhanced durability of shotcrete.}, language = {en} } @unpublished{MalzSindersbergerMonkmanetal., author = {Malz, Sebastian and Sindersberger, Dirk and Monkman, Gareth J. and Steffens, Oliver and Kusterle, Wolfgang}, title = {Determination of the Water Content within Tunnel Linings to Assess Fire Safety}, series = {SSRN Electronic Journal}, journal = {SSRN Electronic Journal}, doi = {10.2139/ssrn.4390700}, pages = {22}, abstract = {Fires in tunnels are known to lead to explosive spalling of the tunnel linings, mainly due to rapid expansion of water as a result of vaporization in the concrete. In order to determine water content and assess fire safety within tunnel linings a novel measurement system has been developed. The development process includes the calibration of the sensor system via both direct and indirect approaches. This work compares both calibration methods and shows the differences that can occur due to measurement uncertainty. This work presents the measured water content within the Inntal tunnel, Austria as a representative tunnel from a total of four investigated tunnels. The obtained water content is compared to that found in the literature, and recommendations for practical work in terms of fire safety is given.}, language = {en} } @inproceedings{ThumannBriendlJuhartetal., author = {Thumann, Maria and Briendl, Lukas G. and Juhart, Joachim and Kusterle, Wolfgang}, title = {Rheologische Untersuchungen an Frischbetonmischungen f{\"u}r Spritzbeton}, series = {Rheologische Messungen an Baustoffen 2019 : Tagungsband zum 28. Workshop und Kolloquium, 13. und 14. M{\"a}rz an der OTH Regensburg}, booktitle = {Rheologische Messungen an Baustoffen 2019 : Tagungsband zum 28. Workshop und Kolloquium, 13. und 14. M{\"a}rz an der OTH Regensburg}, editor = {Teubert, Oliver and Kusterle, Wolfgang and Greim, Markus}, publisher = {tredition}, address = {Hamburg}, isbn = {978-3-7482-4651-0}, pages = {95 ff.}, language = {de} } @misc{BeimlerLeisslEbneretal., author = {Beimler, Josef and Leißl, Caroline and Ebner, Lena and Elsner, Michael and M{\"u}hlbauer, Gerhard and Kohlert, Dieter and Schubert, Martin J. W. and Weiß, Andreas P. and Sterner, Michael and Raith, Thomas and Afranseder, Martin and Krapf, Tobias and Mottok, J{\"u}rgen and Siemers, Christian and Großmann, Benjamin and H{\"o}cherl, Johannes and Schlegl, Thomas and Schneider, Ralph and Milaev, Johannes and Rampelt, Christina and Roduner, Christian and Glowa, Christoph and Bachl, Christoph and Schliekmann, Claus and Gnan, Alfons and Grill, Martin and Ruhland, Karl and Piehler, Thomas and Friers, Daniel and Wels, Harald and Pflug, Kenny and Kucera, Markus and Waas, Thomas and Schlachetzki, Felix and Boy, Sandra and Pemmerl, Josef and Leis, Alexander and Welsch, Andreas F.X. and Graf, Franz and Zenger, Gerhard and Volbert, Klaus and Waas, Thomas and Scherzinger, Stefanie and Klettke, Meike and St{\"o}rl, Uta and Heyl, C. and Boldenko, A. and Monkman, Gareth J. and Kujat, Richard and Briem, Ulrich and Hierl, Stefan and Talbot, Sebastian and Schmailzl, Anton and Ławrowski, Robert Damian and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert and Valentino, Piergiorgio and Romano, Marco and Ehrlich, Ingo and Furgiuele, Franco and Gebbeken, Norbert and Eisenried, Michael and Jungbauer, Bastian and Hutterer, Albert and Bauhuber, Michael and Mikrievskij, Andreas and Argauer, Monika and Hummel, Helmut and Lechner, Alfred and Liebetruth, Thomas and Schumm, Michael and Joseph, Saskia and Reschke, Michael and Soska, Alexander and Schroll-Decker, Irmgard and Putzer, Michael and Rasmussen, John and Dendorfer, Sebastian and Weber, Tim and Al-Munajjed, Amir Andreas and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias and Haug, Sonja and Rudolph, Clarissa and Zeitler, Annika and Schaubeck, Simon and Steffens, Oliver and Rechenauer, Christian and Schulz-Brize, Thekla and Fleischmann, Florian and Kusterle, Wolfgang and Beer, Anne and Wagner, Bernd and Neidhart, Thomas}, title = {Forschungsbericht 2013}, editor = {Baier, Wolfgang}, address = {Regensburg}, organization = {Ostbayerische Technische Hochschule Regensburg}, doi = {10.35096/othr/pub-799}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-7990}, pages = {80}, language = {de} } @inproceedings{SteindlMittermayrThumannetal., author = {Steindl, F. and Mittermayr, Florian and Thumann, Maria and Juhart, Joachim and Galan Garcia, Isabel and Baldermann, Andre and Briendl, Lukas G. and Sakoparnig, Marlene and R{\"o}ck, Rudolf and Kusterle, Wolfgang}, title = {Sulfate resistance of dry mix shotcretes with new binder composition}, series = {ICCC 2019: 15th International Congress on the Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik}, booktitle = {ICCC 2019: 15th International Congress on the Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik}, pages = {3527 -- 3872}, abstract = {Improved understanding of the mechanisms underlying deleterious chemical attacks is necessary to better predict the long-term performance and durability of shotcrete in aggressive environments. In the scope of the research project "ASSpC - Advanced and Sustainable Sprayed Concrete", new durable and sustainable shotcretes and new test methods are developed. In order to increase shotcrete durability, the spray cement (specified in Austrian Guideline "Sprayed concrete") used is substituted with supplementary cementitious materials (SCMs). However, in the past SCMs have seen only limited use in the application of dry-mix shotcrete. This contribution presents 6 new mix designs intended to be used for dry-mix shotcrete, each with varying amounts and types of SCMs, and compares their performance and sprayability with a commercially available spray cement. As sulfate attack is one of the major threats to shotcrete (e.g. in tunnelling), the resistance of the new mixes against sulfate attack is tested using a modified version of the Swiss sulfate test according to SIA 262/1:2013. This approach provides new insights into damaging mechanisms of dry mix shotcrete in sulfate-loaded environments}, language = {en} } @inproceedings{BaldermannMittermayrThumannetal., author = {Baldermann, Andre and Mittermayr, Florian and Thumann, Maria and Kusterle, Wolfgang}, title = {Development of shotcrete with increased durability against thaumasite sulfate attack}, series = {ICCC 2019: 15th International Congress on Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik}, booktitle = {ICCC 2019: 15th International Congress on Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik}, pages = {3425 -- 3435}, language = {en} } @article{SakoparnigGalanSteindletal., author = {Sakoparnig, Marlene and Galan, Isabel and Steindl, Florian Roman and Kusterle, Wolfgang and Juhart, Joachim and Grengg, Cyrill and Briendl, Lukas G. and Saxer, Andreas and Thumann, Maria and Mittermayr, Florian}, title = {Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration}, series = {Materials and structures}, volume = {54}, journal = {Materials and structures}, publisher = {Springer Nature}, doi = {10.1617/s11527-021-01644-7}, pages = {1 -- 23}, abstract = {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.}, language = {en} } @article{SteindlGalanBaldermannetal., author = {Steindl, Florian Roman and Galan, Isabel and Baldermann, Andre and Sakoparnig, Marlene and Briendl, Lukas G. and Juhart, Joachim and Thumann, Maria and Dietzel, Martin and R{\"o}ck, Rudolf and Kusterle, Wolfgang and Mittermayr, Florian}, title = {Sulfate durability and leaching behaviour of dry- and wet-mix shotcrete mixes}, series = {Cement and Concrete Research}, volume = {137}, journal = {Cement and Concrete Research}, number = {November}, publisher = {Elsevier}, doi = {10.1016/j.cemconres.2020.106180}, pages = {1 -- 19}, abstract = {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.}, language = {en} } @article{GalanBriendlThumannetal., author = {Galan, Isabel and Briendl, Lukas G. and Thumann, Maria and Steindl, Florian and Roeck, Rudolf and Kusterle, Wolfgang and Mittermayr, Florian}, title = {Filler Effect in Shotcrete}, series = {Materials}, volume = {12}, journal = {Materials}, number = {19}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma12193221}, pages = {1 -- 24}, abstract = {The effects of fine limestone powder on the early hydration of cementitious systems accelerated by means of alkali-free aluminum sulfate based products, commonly used for shotcrete applications, were investigated in the course of laboratory and real scale tests. In binary (CEM I + limestone) and ternary (CEM I + limestone + slag) systems the addition of fine limestone led to an enhancement of the hydration degree and strength development at early times (<24 h). The formation of ettringite, aluminate hydrates, and C-S-H is affected by the joint action of the setting accelerator and the fine limestone. Accelerator and limestone, in combination with the cement, can be optimized to enhance ettringite and silicate reaction, in some cases coupled with aluminate reaction inhibition, to produce mixes suitable for sprayed concrete applications. Such optimization can help to reduce the cement content in the mixes without compromising the early strength development of the shotcrete.}, language = {en} } @inproceedings{MittermayrGalanSaadeetal.2019, author = {Mittermayr, Florian and Galan, Isabel and Saade, Marcella Ruschi Mendes and Saxer, Andreas and Kusterle, Wolfgang}, title = {"ASSpC" Shotcrete research for the needs of tomorrow}, series = {ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik}, booktitle = {ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik}, pages = {3518 -- 3872}, year = {2019}, abstract = {Shotcrete or sprayed concrete in tunneling in connection with the "New Austrian Tunneling Method" has been developed over the last decades to reach a high quality standard. However, at present the development of new shotcrete mixes is required to fulfill durability and stainability requirements, i.e. for superior performance in aggressive environments and reduction of maintenance costs. In the course of the project ASSpC ("Advanced and sustainable sprayed concrete") the research team focuses on producing and testing new and innovative shotcrete mixes using local and environmentally friendly raw materials. Sustainable and durable shotcrete with optimized mechanical and physical properties and improved chemical resistance is developed. This paper outlines the motivation for the project, gives an overview of the project structure and introduces key reaction mechanisms and environmental controls causing damage of shotcrete in tunnels.}, language = {en} } @inproceedings{SakoparnigGalanBaldermanetal., author = {Sakoparnig, Marlene and Galan, Isabel and Balderman, Andre and Steindl, Florian and Dietzel, Martin and Thumann, Maria and Saxer, Andreas and Kusterle, Wolfgang and Mittermayr, Florian}, title = {Experimental Ca leaching of shotcrete \& secondary precipitation}, series = {ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik}, booktitle = {ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik}, pages = {3488 -- 3495}, language = {en} } @inproceedings{BriendlGalanSteindletal., author = {Briendl, Lukas G. and Galan, Isabel and Steindl, Florian and R{\"o}ck, Rudolf and Thumann, Maria and Juhart, Joachim and Baldermann, Andre and Mittermayr, Florian and Kusterle, Wolfgang}, title = {Hydration processes of accelerated cementitious systems governing early strength development}, series = {ICCC 2019: 15th International Congress on Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik}, booktitle = {ICCC 2019: 15th International Congress on Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik}, pages = {714 -- 724}, language = {en} } @inproceedings{JuhartBriendlRoecketal., author = {Juhart, Joachim and Briendl, Lukas G. and R{\"o}ck, Rudolf and Galan, Isabel and Thumann, Maria and Mittermayr, Florian and Kusterle, Wolfgang}, title = {Performance optimization of shotcrete by combined fillers}, series = {ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik}, booktitle = {ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik}, pages = {1387 -- 3872}, language = {en} } @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{SakoparnigBaldermannThumannetal., author = {Sakoparnig, Marlene and Baldermann, Andre and Thumann, Maria and Mittermayr, Florian and Kusterle, Wolfgang}, title = {Bestimmung der experimentellen Calcium-Auslaugung an Spritzbetonbohrkernen: Methodenvergleich und Update}, series = {Spritzbeton-Tagung 2018, Alpbach, {\"O}sterreich 11.-12.01.2018}, booktitle = {Spritzbeton-Tagung 2018, Alpbach, {\"O}sterreich 11.-12.01.2018}, abstract = {Im Rahmen des FFG-Forschungsprojektes „Entwicklung neuer dauerhafter und nachhaltiger Spritzbetone (Advanced and sustainable sprayed concrete; ASSpC)" werden Methoden zur Pr{\"u}fung der Calcium-Auslaugung von Spritzbeton eingesetzt bzw. weiterentwickelt. Bestimmt wurde daf{\"u}r das Reduzierte Versinterungspotential nach Regelwerken der {\"O}sterreichischen Bautechnik Vereinigung und das Auslaugverhalten von Spritzbeton bei leichtem S{\"a}ureangriff (Salpeters{\"a}ure und Kohlens{\"a}ure), um dauerhaftigkeitsrelevante Parameter im Bereich der Wechselwirkungen von Spritzbeton mit leicht sauren (Kohlens{\"a}ure- und Nitrathaltigen) Oberfl{\"a}chen-, Grund- und Sickerw{\"a}ssern zu untersuchen und potentielle Sch{\"a}digungsmechanismen zu identifizieren und zu quantifizieren. Die Vor- und Nachteile der verwendeten Pr{\"u}fmethoden zum l{\"o}senden Angriff werden in Bezug auf die Dauerhaftigkeit von Spritzbeton diskutiert.}, language = {de} } @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} }