TY - CHAP A1 - Steindl, F. A1 - Mittermayr, F. A1 - Thumann, Maria A1 - Juhart, J. A1 - Galan Garcia, Isabel A1 - Baldermann, Andre A1 - Briendl, Lukas G. A1 - Sakoparnig, M. A1 - Röck, Rudolf A1 - Kusterle, Wolfgang T1 - Sulfate resistance of dry mix shotcretes with new binder composition T2 - ICCC 2019: 15th International Congress on the Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik N2 - 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 Y1 - 2019 SP - 3527 EP - 3872 ER - TY - JOUR A1 - Galan, Isabel A1 - Briendl, Lukas G. A1 - Thumann, Maria A1 - Steindl, Florian A1 - Roeck, Rudolf A1 - Kusterle, Wolfgang A1 - Mittermayr, Florian T1 - Filler Effect in Shotcrete JF - Materials N2 - 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. KW - acceleration KW - ACCELERATORS KW - ALKALI-FREE KW - ALUMINUM SULFATE KW - CaCO3 KW - CALCIUM-CARBONATE KW - CEMENT HYDRATION KW - EARLY AGE HYDRATION KW - hydration KW - LIMESTONE POWDER KW - mechanical properties KW - PORTLAND-CEMENT Y1 - 2019 U6 - https://doi.org/10.3390/ma12193221 VL - 12 IS - 19 SP - 1 EP - 24 PB - MDPI CY - Basel ER - TY - CHAP A1 - Briendl, Lukas G. A1 - Galan, Isabel A1 - Steindl, Florian A1 - Röck, Rudolf A1 - Thumann, Maria A1 - Juhart, Joachim A1 - Baldermann, Andre A1 - Mittermayr, Florian A1 - Kusterle, Wolfgang T1 - Hydration processes of accelerated cementitious systems governing early strength development T2 - ICCC 2019: 15th International Congress on Chemistry of Cement, 16.-20.09.2019, Prague, Czech Republik Y1 - 2019 SP - 714 EP - 724 ER - TY - CHAP A1 - Thumann, Maria A1 - Briendl, Lukas G. A1 - Juhart, J. A1 - Kusterle, Wolfgang ED - Teubert, Oliver ED - Kusterle, Wolfgang ED - Greim, Markus T1 - Rheologische Untersuchungen an Frischbetonmischungen für Spritzbeton T2 - Rheologische Messungen an Baustoffen 2019 : Tagungsband zum 28. Workshop und Kolloquium, 13. und 14. März an der OTH Regensburg KW - Beton KW - Rheologie Y1 - 2019 SN - 978-3-7482-4651-0 PB - tredition CY - Hamburg ER - TY - CHAP A1 - Juhart, J. A1 - Briendl, Lukas G. A1 - Röck, Rudolf A1 - Galan, Isabel A1 - Thumann, Maria A1 - Mittermayr, F. A1 - Kusterle, Wolfgang T1 - Performance optimization of shotcrete by combined fillers T2 - ICCC 2019: 15th International Congress on the Chemistry of Cement, ICCC 2019, 16.-20.09.2019, Prague, Czech Republik Y1 - 2019 SP - 1387 EP - 3872 ER - TY - CHAP A1 - Galan, Isabel A1 - Thumann, Maria A1 - Briendl, Lukas G. A1 - Röck, Rudolf A1 - Steindl, Florian A1 - Juhart, Joachim A1 - Mittermayr, Florian A1 - Kusterle, Wolfgang ED - Beck, Thomas ED - Myren, Synnøve A. ED - Engen, Siri T1 - From Lab Scale Spraying to Real Scale Shotcreting and back to the Lab T2 - 8th International Symposium on Sprayed Concrete : Modern Use of Wet Mix Sprayed Concrete for Underground Support - Trondheim, Norwegen. - 11. - 14.06.2018 N2 - 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. Y1 - 2018 UR - https://betong.net/wp-content/uploads/8th-Sprayed-Concrete_Web-Proceedings.pdf SN - 978-82-8208-060-6 SP - 139 EP - 153 ER - TY - CHAP A1 - Juhart, Joachim A1 - Briendl, Lukas G. A1 - Mittermayr, Florian A1 - Thumann, Maria A1 - Röck, Rudolf A1 - Kusterle, Wolfgang T1 - Optimierte Eigenschaften von Spritzbeton durch kombinierte Zusatzstoffe T2 - Tagungs-CD der Spritzbeton-Tagung 2018, 11.-12. Januar 2018, Alpbach, Tirol, CD-ROM Y1 - 2018 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 - CHAP A1 - Juhart, J. A1 - Briendl, Lukas G. A1 - Mittermayr, F. A1 - Röck, R. A1 - Thumann, Maria A1 - Kusterle, Wolfgang T1 - Mischungsentwicklung von nachhaltigem Spritzbeton mit kombinierten Zusatzstoffen T2 - Beton Graz '18 : 4. Grazer Betonkolloquium : 20./21. September 2018 N2 - Spritzbeton ist nachhaltig, wenn er sowohl umweltfreundlich als auch dauerhaft ist. Traditionelle Mischungszusammensetzungen für Spritzbeton enthalten einen hohen Anteil an fein gemahlenem Portlandzement und an Erstarrungsbeschleunigern. Beide Komponenten sind für eine sehr schnelle Festigkeitsentwicklung, aber auch hohe Umweltauswirkungen (wie CO2-Emissionen, Primärenergiebedarf) verantwortlich. Portlandzement ist ein hervorragendes Bindemittel, bringt aber ein hohes Versinterungspotenzial und bei normaler Zusammensetzung einen geringen Widerstand gegen chemischen Angriff, wie zum Beispiel den Sulfatangriff aus dem Bergwasser, mit sich. Hingegen können latent hydraulische und puzzolanische Zusatzstoffe die Dauerhaftigkeit erhöhen, sind aber auch für eine langsame Festigkeitsentwicklung bekannt. Im Beitrag wird ein neues Konzept des Mischungsentwurfs vorgestellt, das auf der Auswahl geeigneter Zusatzstoffe (i.e. feinste Kalksteinmehle, die die Hydratation beschleunigen, kombiniert mit gemahlenem Hüttensand und Puzzolanen), der Optimierung von Packungsdichte und Wasserbedarf sowie einem optimalen Mischungsverhältnis aller Feinstoffe beruht. Es wird an exemplarischen Mischungszusammensetzungen gezeigt, welche Eigenschaften bzw. Leistungsmerkmale in Labortests sowie in großmaßstäblichen Spritzversuchen erreicht werden können. KW - Bindemittel KW - chemischer Angriff KW - CO2-Emission KW - Dauerhaftigkeit KW - Hüttensand KW - Hydratation KW - Kalkstein KW - Labortest KW - Mischungsverhältnis KW - Packungsdichte KW - Portlandzement KW - Primärenergie KW - Spritzbeton KW - Wasserbedarf KW - Zusatzstoff Y1 - 2018 SN - 978-3-85125-621-5 SP - 139 EP - 152 PB - Verlag der Technischen Universität Graz CY - Graz 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 -