Sponsors: American Concrete Institute, RILEM, Université de Sherbrooke, CRIB, Université Toulouse III, Lmdc Toulouse, Kruger Biomaterials, Euclid Chemical, Prodexim International inc., BASF Master Builders, ACAA Editor: Arezki Tagnit-Hamou In July 1983, the Canada Centre for Mineral and Energy Technology (CANMET) of Natural Resources Canada, in association with the American Concrete Institute (ACI) and the U.S. Army Corps of Engineers, sponsored a five-day international conference at 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 taken place 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 renewed interest in alternative and sustainable binders and supplementary cementitious materials, a new series was launched by Sherbrooke University (UdeS); ACI; and the International Union of Laboratories and Experts in Construction materials, Systems, and Structures (RILEM). They, 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 in Montréal, QB, Canada, from October 2 to 4, 2017. The conference proceedings, containing 50 refereed 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 held online from June 7 to 10, 2021. The conference proceedings, containing 53 peer reviewed papers from more than 14 countries, were published as ACI SP-349. 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 was to highlight advances in the field of alternative and sustainable binders and supplementary cementitious materials, which are receiving increasing attention from the research community. To all those whose submissions could not be included in the conference proceedings, the Institute and the Conference Organizing Committee extend their appreciation for their interest and hard work. Thanks are extended to the members of the international scientific committee to review the papers. Without their dedicated effort, the proceedings could not have been published for distribution at the conference. The cooperation of the authors in accepting reviewers’ suggestions and revising their manuscripts accordingly is greatly appreciated. The assistance of Chantal Brien at the Université de Sherbrooke is gratefully acknowledged for the administrative work associated with the conference and for processing the manuscripts, both for the ACI proceedings and the supplementary volume. Arezki Tagnit Hamou, Editor Chairman, eleventh ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete (ICCM2021). Sherbrooke, Canada 2021

This paper studies the use of a new preconditioning process for an accelerated testing of concrete resistance against sulfate attack. For this reason, concrete specimens were subjected to a part by part pre-saturation method using a concentrated sulfate solution drained inside desiccators. This preconditioning technique was applied before exposing the specimens to different immersion conditions in 5% and 10% sulfate solutions, and to storing at high temperature and to wetting/drying cycles. Length change measurements and sulfate penetration profiles were performed on normal and high strength concretes. In addition, SEM-EDS analysis were used to investigate the type and amount of degradation products in the core layer of samples exposed to accelerated testing. The new pre-saturation method highly accelerated the degradation of concrete samples exposed to different immersion conditions. The microstructural observations showed advanced depths and greater amounts of gypsum and ettringite within the degraded specimens subjected to the primary preconditioning stage. However, the real field observations were only achieved when combining the pre-saturation method and the immersion in 5% sulfate solution.

The feasibility of producing “just add water” alkali-activated self-consolidated (AASCC) mixtures using multi-powder activators and various cement-less binder combinations was evaluated in this study. During this study, fresh properties for mortar mixtures were evaluated by conducting the mini-slump flow test. Moreover, the relative performance of activated mortars and potential interactions among materials used in the mixtures was examined using the isothermal calorimeter. The performance of the hardened mortar mixtures was evaluated after 3, 7 and 28 days by conducting compressive strength tests. Results indicated an increase in the mechanical properties was observed while increasing the dry-powder activator ratio and source material nature for ground and non-ground mixtures.

This paper focuses on developing ambient-cured alkali-activated concrete incorporating recycled concrete aggregates (RA). The binder was either slag or a blend of slag and fly ash (3:1, by mass). Hook-ended steel fibers were added, in 2% volumetric fraction, to improve the properties of concrete made with RA. The alkaline activator solution was a blend of sodium silicate and sodium hydroxide. Concrete mixtures were proportioned to achieve three target compressive strengths, namely 30, 45, and 60 MPa. The performance of concrete mixtures was assessed based on 1, 7, and 28-day compressive strengths. Experimental results showed that full replacement of natural aggregates by RA caused up to 28% reduction in compressive strength of plain alkali-activated slag concretes, with greater reductions being reported in mixtures with higher target strength and tested at 28 days. The incorporation of 2% steel fibers enhanced the strength and caused limited strength reductions of up to 7%. Compared to alkali-activated slag RA concretes, mixtures with 25% fly ash replacement exhibited lower strengths at 1 and 7 days, but their 28-day strength was superior. Analytical multi-linear regression models were developed to identify statistical significance of concrete components and examine their impact on the compressive strength.

The occurrence of CAH10 in a calcium sulfoaluminate (CSA) clinker and in the CSA clinker blended with anhydrite was assessed by experimental data and thermodynamic modelling. For the CSA clinker it was found that CAH10 forms as an intermediate phase directly from the hydration of ye’elimite together with ettringite and aluminium hydroxide, which is an alternative reaction path to the formation of monosulfate and aluminium hydroxide. The occurrence of CAH10 is linked to the solubility of the aluminum hydroxide formed, which decreases with time due to an increase of its crystallinity. In case of a highly soluble aluminum hydroxide, which occurs at early hydration times, the formation of CAH10 and ettringite is thermodynamically more favoured than the formation of monosulfate. At later ages, when the solubility of aluminum hydroxide decreases, CAH10 and a part of the ettringite convert to monosulfate. This conversion is associated with an increase of porosity, which leads to a significant loss of compressive strength beyond a sample age of 28 days. In the CSA clinker blended with anhydrite the formation of CAH10 could not be evidenced. No loss of compressive strength was observed for this sample.