International Concrete Abstracts Portal

Bleeding and finishing issues can result in an increased risk of concrete scaling. This risk may be further increased when supplementary cementitious materials and Type IL cement are used. This article focuses on petrographic examination of scaled flatwork constructed of concrete containing Type IL cement and fly ash, and Type IL cement and slag cement.

The Slag Cement Association (SCA) announced the recipients of the 2024 Slag Cement in Sustainable Concrete Awards during the ACI Concrete Convention – Spring 2025 in Toronto, ON, Canada. These fourteen winners all demonstrate how slag cement works to improve the durability of concrete while lowering the embodied carbon associated with concrete production.

In July of 1983, the Canada Centre for Mineral and Energy Technology of Natural Resources Canada (CANMET), in association with the American Concrete Institute (ACI) and the U.S. Army Corps of Engineers, sponsored a 5-day international conference in Montebello, Quebec, Canada, on the use of fly ash, silica fume, slag, and other mineral by-products in concrete. The conference brought together representatives from industry, academia, and government agencies to present the latest information on these materials and to explore new areas of needed research. Since then, eight other such conferences have been held around the world (Madrid, Trondheim, Istanbul, Milwaukee, Bangkok, Madras, Las Vegas, and Warsaw). The 2007 Warsaw Conference was the last in this series. In 2017, due to the renewed interest in alternative and sustainable binders and supplementary cementitious materials, a new series was launched by Sherbrooke University (Professor Arezki Tagnit-Hamou), American Concrete Institute (ACI), and the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM)—in association with a number of other organizations in Canada, the United States, and the Caribbean—sponsored the 10th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete (ICCM2017). The conference was held October 2-4, 2017, in Montréal, Canada. The conference proceedings, containing 50 reviewed papers from more than 33 countries, were published as ACI SP-320. In 2021, UdeS, ACI, and RILEM, in association with Université de Toulouse and a number of other organizations in Canada, the United States, and Europe, sponsored the 11th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete (ICCM2021). The conference was scheduled to take place in Toulouse, but due to COVID, it was held online June 7-10, 2021. The conference proceedings, containing 53 reviewed papers from more than 21 countries, were published as ACI SP-349. In 2024, the conference was finally held in-person in Toulouse from June 23 to 26, 2024, with the support of UdeS, ACI, and RILEM in association with Université de Toulouse (Martin Cyr) and a number of other organizations in Canada, the United States, and Europe. The purpose of this international conference was to present the latest scientific and technical information in the field of supplementary cementitious materials and novel binders for use in concrete. The new aspect of this conference is to highlight advances in the field of alternative and sustainable binders and supplementary cementitious materials for the transition to low carbon concrete. The conference proceedings, containing 78 reviewed papers from more than 25 countries, have been published as ACI SP-362. Thanks are extended to the members of the International Scientific Committee who reviewed the papers. The cooperation of the authors in accepting the reviewers’ suggestions and revising their manuscripts accordingly is greatly appreciated. The involvement of the steering committee and the organizing committee is gratefully acknowledged. Special thanks go to Chantal Brien (Université de Sherbrooke) for the administrative work associated with the conference and for processing the manuscripts for both the ACI proceedings and the supplementary volume. Arezki Tagnit Hamou, Editor Chairman, 12th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete (ICCM2024). Sherbrooke, Canada, 2024

Accelerated carbonation of recycled concrete aggregates (RCA) is one way to convert them into carbon stores by capturing CO₂ from cement plants. This study investigates the CO₂ captured depending on composition (paste, mortar, or concrete), origin (laboratory, platform), production process (crushing, molding, sawing), and age of RCA. The CO₂ captured is quantified by means of calcimetry (CaCO₃ content evolution). RCA studied ranged in size from 4 to 16 mm (0.16 to 0.63 in.). They were carbonated on a laboratory or semi-industrial scale. It has been shown that the CaCO₃ content of young RCA or RCA protected from natural carbonation, crushed and composed of CEMI is more likely to evolve. It was shown that the cement paste content and the duration of accelerated carbonation increase the amount of CO₂ captured. The composition of the parent aggregates affects the non-carbonated and carbonated CaCO₃ contents, which requires accurate sampling to limit bias in the results. Carbonation efficiency is more difficult to estimate on a semi-industrial scale and the assessment by calcimetric measurement is biased when the parent concrete is made of slag-based cement. The study was carried out within the framework of the French national program FastCarb.

It is known that the use of recycled coarse aggregates (RCA) can raise a variety of problems, which are mainly due to the porosity of the old mortar contained in RCA. One of the simpler ways to solve these problems is the pre-wetting of RCA, which allows not only to minimize disadvantages but also to obtain the advantages associated with the effect of internal curing. Undoubtedly, the strongest positive effect of pre-wetted RCA is on the rheology of recycled concrete. But there are also possible positive effects of internal curing for strength and durability of blended cement concretes, which require longer curing times compared to normal Portland cement concrete. In this paper, we mostly study the influence of porous RCA on the rheology of cement paste, based on slag cement with a 75% slag content. For this purpose, the absorption properties of RCA of different sizes were studied. From this, mathematical dependences of the workability of cement systems on w/c and time could be obtained. These further underline the positive effect of pre-wetting of RCA with regard to retaining the workability of cementitious systems. This lays the basis for a broader study of pre-wetting RCA on the rheology of mixtures, strength, and durability to be covered in future publications.