Search

The final publication is available at Springer via http://dx.doi.org/10.1617/s11527-022-01927-7 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. The authors would like to thank HeidelbergCement AG for the supplied cements and the chemical and physical analysis. H. Vanoutrive has received internal funding from KU Leuven which made this interlaboratory study possible. P. Van den Heede, N. Alderete and Z. Liu are funded by the Research Foundation—Flanders (FWO) (project No. G062720N, 12ZG820N and G0F3619N). The financial support of FWO is gratefully acknowledged. Peer Reviewed This report has been prepared by members of the working groups 1 and 2 within a framework of RILEM TC 281-CCC ‘‘Carbonation of concrete with supplementary cementitious materials’’ and further reviewed and approved by all members of the RILEM TC 281-CCC. TC Membership Chair: Prof. Nele De Belie. Deputy Chair: Prof. Susan Bernal Lopez. Members: Natalia Alderete, Carmen Andrade, Ueli Angst, Tushar Bansal, Ve´ronique Baroghel-Bouny, Muhammed P.a. Basheer, Nele De Belie, Susan Bernal Lopez, Hans D. Beushausen, Leon Black, Aires Camöes, Servando Chincho´n-Paya, Özlem Cizer, Gisela Paola Cordoba, Martin Cyr, Patrick Dangla, Yuvaraj Dhandapani, Katja Dombrowski-Daube, Vilma Ducman, Yogarajah Elakneswaran, Jan Elsen, Juan Manuel Etcheverry, Miren Etxeberria, Ana Maria Fernandez-Jimenez, Lander Frederickx, Isabel Fuencisla Saez del Bosque, Cassandre Le Galliard, Ine`s Garcia Lodeiro, Daniel Geddes, Christoph Gehlen, Mette Geiker, Guoqing Geng, Bahman Ghiassi, Gregor Gluth, Cyrill Grengg, Elke Gruyaert, R. Doug Hooton, Bruno Huet, Andres Idiart, Ivan Ignjatovic, Kei-Ichi Imamoto, Shiju Joseph, Siham Kamali-Bernard, Antonis Kanellopoulos, Xinyuan Ke, Sylvia Kessler, Heejeong Kim, Arto Ko¨lio¨, Juan Li, Ning Li, Tung Chai Ling, Qing-Feng Liu, Zhiyuan Liu, Barabare Lothenbach, Isabel Martins, Jose´-Fernando Martirena-Hernandez, César Medina Martinez, Fabrizio Moro, Shishir Mundra, Marija Nedeljkovic, Kolawole A. Olonade, José Pacheco, Christian Paglia, Angel Paloma, Ravi Patel, Janez Perko, Quoc Tri Phung, John L. Provis, Francisca Puertas, Nuria Rebolledo, Marlene Sakoparnig, Javier Sancez Montero, Francesco Santoro, Sriram Pradeep Saridhe, Karen Scrivener, Marijana Serdar, Zhenguo Shi, Kosmas K. Sideris, Ruben Snellings, Matteo Stefanoni, Charlotte Thiel, Karl-Christian Thienel, Michael D.A. Thomas, Ilda Tole, Luca Valentini, Philip Van den Heede, Hanne Vanoutrive, Yury Andre´s Villagran Zaccardi, Talakokula Visalakshi, Anya Vollpracht, Stefanie Von Greve-Dierfeld, Brant Walkley, Fazhou Wang, Ling Wang, Jinxin Wei, Lia Weiler, Bei Wu, Yan Yao, Guang Ye, Maciej Zaja˛c, Zengfeng Zhao, Semion Zhutovsky. Hanne Vanoutrive and Philip Van den Heede have contributed equally to this work.

The rapid increase in steel slag generation globally highlights the urgent need to manage the disposal or utilization processes. In addition to conventional landfill disposal, researchers have successfully reused steel slag in the construction, chemical, and agricultural fields. With the large portions of alkaline silicate mineral content, steel slag can also be used as a suitable material for carbon capture to mitigate global warming. This article comprehensively reviews the environmental performance of steel slag utilization, especially emphasizing quantitative evaluation using life cycle assessment. This paper first illustrates the production processes, properties, and applications of steel slag, and then summarizes the key findings of the environmental benefits for steel slag utilization using life cycle assessment from the reviewed literature. This paper also identifies the limitations of quantifying the environmental benefits using life cycle assessment. The results indicate steel slag is largely utilized in pavement concrete and/or block as a substitution for natural aggregates. The associated environmental benefits are mostly attributed to the avoidance of the large amount of cement utilized. The environmental benefits for the substitution of traditional energy-intensive material and carbonation treatment are further discussed in detail. Due to the presence of heavy metals, the potential risks to human and ecological health caused by the manufacturing process and usage stage are examined. Finally, the current challenges and global social implications for steel slag valorization are summarized.

In this study, municipal solid waste incineration fly ash (MSWIFA) was pretreated with CO2 via slurry carbonation (SC) and dry carbonation coupled with subsequent water washing (DCW). Both the treated MSWIFAs were then used as cement replacement in cement pastes by weight of 10%, 20% and 30% to investigate the influence on hydration mechanisms, physico-mechanical characteristics and leaching properties. The results showed that carbonates formed on the surface of SC-MSWIFA particles were finer (primarily 20–50 nm calcite) than those from the corresponding DCW-MSWIFA (mostly 130–200 nm vaterite). Hence, SC-MSWIFA blended cement pastes led to shorter setting time and higher early compressive strength than the DCW-MSWIFA pastes. In contrast, the presence of vaterite-rich DCW-MSWIFA in the blended cement pastes could accelerate the cement hydration after 24 h. Both the CO2-pretreated MSWIFA can replace cement up to 30% without sacrificing the long-term strength and mechanical properties of cement pastes, demonstrating excellent performance as a supplementary cementitious material. Moreover, volume stability in terms of expansion and lead leaching of CO2-pretreated MSWIFA cement pastes were far below the regulatory limits.