International Concrete Abstracts Portal

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

Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) is a type of concrete with superior mechanical and durability properties, which might be improved even further with the addition of nano-materials. This work studies the influence of adding nano-additions to two UHPFRCs with compressive strength around 150MPa (21755 psi), with and without crystalline admixtures. Two nano-materials were considered: cellulose nano-crystals (4-5 nm diameter, 50–500 nm length, 0.157-0.197 μin diameter, 1.97-19.7 μin length); in a dosage up to 0.15% by the cement weight; and aluminum oxide nanofibers (diameter 4-11nm, length 100-900nm, 0.157-0.433 μin diameter, 3.94-35.4 μin length) in a dosage of 0.25% by the cement weight. Water content of the mixes with nanomaterials was modified to maintain workability in a similar range aiming to maintain the self-compacting behavior. The following properties were analyzed: workability, compressive strength, modulus of elasticity and tensile properties calculated through a simplified inverse analysis after performing four-point bending tests. The study considered the effect of using three levels of mixing energy to ensure a proper dispersion of all the components, and its effect in the aforementioned properties. The results show a potential effect of these nanomaterials as nanoreinforcement, with slightly better ultimate strength and strain values for the higher energy level.

Supplementary cementing materials (SCM) have a great importance for preventing ASR in concrete structures worldwide. Different materials were used, e.g. fly ashes, silica fume or metakaolin. However, the results are often contradictory. What works with one aggregate does not necessarily work with another, or in other cases, the efficiency is not the same. Not all effects can be explained by fluctuations in the SCM composition.

Long-term investigations were carried out using three different aggregates. Concrete prisms were produced, and parallel aggregates were stored together with different SCM`s (different types and concentrations) in highly alkaline solutions with and without calcium hydroxide in the system. The reaction products, which precipitated as a result of the interactions between aggregate and SCM`s at different storage times, could be investigated by NMR and even XRD. The results were surprising because different aggregates formed different reaction products when using the same SCM. Such effects can only be explained by the release of different soluble minerals that are part of aggregates.

The conclusion is that obviously aggregates control the formation process of reaction products which are formed as a result of the interactions between SCM`s and aggregates. And these products are responsible for preventing ASR when using the SCM`s.

Boron efficiently absorbs neutrons due to its large cross section. Thus, boron containing materials are an effective shield to neutrons and are commonly used as containment barriers in nuclear reactors. The most economical way to include boron into shielding structures is to prepare B-rich mortars or concretes, to be used as structural elements or as plastering. However, colemanite [Ca(B₃O₄(OH)₃)∙(H₂O)], the most abundant Bcontaining mineral, is sufficiently soluble to release enough borate ions in solution to indefinitely stop Portland cement hydration.

Here we present the formulation of hydraulically active binders containing 50% of colemanite. They are based on blends of calcium aluminate cements and blastfurnace slag. The main hydration product in the absence of colemanite is strätlingite along with other AFm phases. MgO causes an increasing hydrotalcite precipitation, and fly ashes further increase strätlingite content. The presence of colemanite causes the precipitation of B-ettringite, where B(OH)₄^¯ ions substitute for sulphate ions. These binders set in one day and harden in 4 days. The addition of hydrated lime in the formulations brings about the additional precipitation of B-containing AFm phases, where the trigonal HBO₃^2- ion constitutes the interlayer between positive [Ca₂Al(OH)₆]+ sheets. These binders set in few hours and harden in one day.

To decarbonize the portland cement sector worldwide, the Cement Sustainability Initiative recommends systematically reducing the clinker-to-cement ratio down to 60% by 2050. However, the sources of usable clinker substitutes - the supplementary cementitious materials (SCMs) - are unevenly distributed geographically and will become increasingly scarce in the future. Through a time-series material-product chain analysis, this paper investigates the multi-regional and multi-sectorial (cement, coal-fired electricity, and steel sectors) interactions that occur when increasing demand for SCMs in eastern Canada and Northeastern U.S., up to 2050. It tracks the trade effects and how it affects region-specific domestic flows of raw and secondary materials, end-product products, and greenhouse gas emissions. Although the lever is favorable overall, the results show unintended economic and environmental consequences across regions, with winners and losers. At the material level, benefits are influenced by the local availability of SCMs, which disadvantages Canadian regions due to the increasing remoteness of supply to meet demand. At the product level, decoupling blended cement production capacity from clinker production capacity allows the U.S. regions to reduce their dependence on Canadian cement imports. These new perspectives provide key geopolitical, environmental, and economic insights for better decision-making when developing sustainable initiatives.