@article{VanoutriveAldereteDeBelieetal., author = {Vanoutrive, Hanne and Alderete, Natalia and De Belie, Nele and Etxeberria, Miren and Grengg, Cyrill and Ignjatović, Ivan and Ling, Tung-Chai and Liu, Zhiyuan and Garcia-Lodeiro, In{\´e}s and Medina Mart{\´i}nez, C{\´e}sar and Sanchez, Javier and Palomo, Angel and Rebolledo, Nuria and Sakoparnig, Marlene and Sideris, Kosmas and Thiel, Charlotte and Van den Heede, Philip and Vollpracht, Anya and von Greve-Dierfeld, Stefanie and Wei, Jinxin and Zając, Maciej and Gruyaert, Elke}, title = {Report of RILEM TC 281-CCC: outcomes of a round robin on the resistance to natural carbonation of Portland, Portland-fly ash and blast-furnace cements and its relation to accelerated carbonation}, series = {Materials and Structures}, volume = {57}, journal = {Materials and Structures}, number = {9}, publisher = {Springer Science and Business Media}, issn = {1359-5997}, doi = {10.1617/s11527-024-02464-1}, abstract = {Numerous (inter)national standards are in place for assessing the resistance to carbonation of mortar and concrete. Within the framework of RILEM TC 281-CCC 'Carbonation of Concrete with SCMs,' an extensive interlaboratory test campaign (ILT) involving twenty-two participating laboratories worldwide was initiated to compare natural carbonation of concrete and mortar with three different cement types (Portland cement (CEM I), Portland-fly ash cement (CEM II/B-V) and blast-furnace cement (CEM III/B)) and investigate its relation to accelerated carbonation as reported in Vanoutrive et al. (Mater Struct 55:1-29, 2022). It could be concluded that ranking of cement types was analogous between accelerated and natural carbonation methods. Environmental parameters have an important effect on the carbonation rate, however, differences between the mean carbonation rates originating from indoor and sheltered outdoor natural exposure with different exposure conditions and curing regimes were insignificant for each considered cement type. This is caused by the scatter related to carbonation testing among different laboratories. Nevertheless, results showed that a natural exposure period of at least one year is essential to reach a constant carbonation rate over time. For both natural and accelerated carbonation, the carbonation rate increased by 18\% when the aggregate-to-cement ratio increased by 1.79 (concrete versus mortar). This correlation seems insensitive to binder type and exposure method. Finally, the best correlation between natural and accelerated carbonation was found for EN 12390-10 (specifically natural indoor exposure) and EN 12390-12 (accelerated exposure) when only test methods performed by more than one laboratory were considered.}, language = {en} } @article{BernalDhandapaniElakneswaranetal., author = {Bernal, Susan A. and Dhandapani, Yuvaraj and Elakneswaran, Yogarajah and Gluth, Gregor J. G. and Gruyaert, Elke and Juenger, Maria C. G. and Lothenbach, Barbara and Olonade, Kolawole Adisa and Sakoparnig, Marlene and Shi, Zhenguo and Thiel, Charlotte and van den Heede, Philip and Vanoutrive, Hanne and Von Greve-Dierfeld, Stefanie and De Belie, Nele and Provis, John L.}, title = {Report of RILEM TC 281-CCC: A critical review of the standardised testing methods to determine carbonation resistance of concrete}, series = {Materials and Structures}, volume = {57}, journal = {Materials and Structures}, number = {8}, publisher = {Springer}, issn = {0025-5432}, doi = {10.1617/s11527-024-02424-9}, pages = {31}, abstract = {The chemical reaction between CO2 and a blended Portland cement concrete, referred to as carbonation, can lead to reduced performance, particularly when concrete is exposed to elevated levels of CO2 (i.e., accelerated carbonation conditions). When slight changes in concrete mix designs or testing conditions are adopted, conflicting carbonation results are often reported. The RILEM TC 281-CCC 'Carbonation of Concrete with Supplementary Cementitious Materials' has conducted a critical analysis of the standardised testing methodologies that are currently applied to determine carbonation resistance of concrete in different regions. There are at least 17 different standards or recommendations being actively used for this purpose, with significant differences in sample curing, pre-conditioning, carbonation exposure conditions, and methods used for determination of carbonation depth after exposure. These differences strongly influence the carbonation depths recorded and the carbonation coefficient values calculated. Considering the importance of accurately determining carbonation potential of concrete, not just for predicting their durability performance, but also for determining the amount of CO2 that concrete can re-absorb during or after its service life, it is imperative to recognise the applicability and limitations of the results obtained from different tests. This will enable researchers and practitioners to adopt the most appropriate testing methodologies to evaluate carbonation resistance, depending on the purpose of the conclusions derived from such testing (e. g. materials selection, service life prediction, CO2 capture potential).}, 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{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} } @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} }