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

This paper presents an experimental study carried out to investigate the durability of one-part alkaliactivated slag (AAS) mortars in different aggressive environments, such as chloride- and sulphate-rich solutions or in presence of freezing-thawing cycles. The mixtures were manufactured at equal water content and were activated by using sodium silicate, potassium hydroxide and sodium carbonate in powder form. In particular, the behavior of AAS mortars with different alkali content was compared with that of mixtures based on Portland cement and blast-furnace cement. Results show that the alkali content is a key-parameter for the durability of these innovative binders. In fact, in mortars manufactured with an alkali content higher than 0.06 by binder mass, the strength loss is similar to those of mixtures based on blast furnace cement after 150 freeze/thaw cycles. On the contrary, the sulphate-rich solution promotes a stronger degradation of the slag-based mortars respect to that shown by cement-based mixtures, regardless of the alkali content. Finally, the strong deterioration of cement matrix promoted by the formation of oxychloride in CaCl₂-rich environment is negligible in AAS mortars due to the lack of calcium hydroxide in the slag matrix.

The effect of temperature on the hydration of portland cement blended with 20% of metakaolin is studied in a temperature range of 5 to 40°C. Temperature affects microstructure, phase assemblage, and transport properties. Temperature shows a strong influence on the microstructure at early age in both systems because it enhances the reactivity. At late age of hydration, the inner product formation of the blended system is less developed at higher temperature. The hydrated phase of the blended with metakaolin is more sensitive to the temperature than the plain system. In particular, the AFm and AFt phases vary depending on the temperature. The microstructure governs the transport properties of cements; the blended system shows a lower bulk conductivity. The reactivity of metakaolin is slow at lower temperatures resulting in a high bulk conductivity at early age in the blended system.

Low environmental impact binders, in which clinker is partially substituted by less reactive powders, are used in proportioning low water-to-cement ratios mixtures to ensure higher compactness, low porosity and improved mechanical as well as durability properties. The use of relatively high solid volume fractions dramatically affects the workability of the mixture and affects its ease of placement and consolidation. Various superplasticizer types have been investigated in literature to control the rheological properties, although these admixtures considerably decrease the yield stress values, their effect on viscosity is moderate. The main objective of this investigation is to control the rheology of ternary cements by controlling the morphology of particles, which is the key parameter affecting the rheology of cementitious suspension. The test results on LC3 (i.e. 55% Portland cement + 30% calcine clay + 15% Limestone) and CEM II/B-M (S-LL) (i.e. 65% Portland cement + 20% Slag + 15% Limestone) ternary binders revealed that the optimization of the particlesize distribution and the maximum packing fraction of the powders leads to a considerable decrease of both viscosity and yield stress by 20% and 50%, respectively.

The industrialization of Super Sulphated Slag Cement requires a strict control of the activation of slag. Optimal activator content is a compromise between early age and long term strengths. In particular, an excessive activator dosage leads to a strong decrease of final strength that could lead to non-conformities. Thanks to the coupled use of mechanical testing, SEM and isothermal calorimetry, this paper provides a clearer insight on how SSSC reacts. It is shown that excess of activation impacts mechanical strength twofold. First, it is observed after one or two days of hydration a decrease of hydration kinetics that could be attributed to a denser or thicker hydrate layer around slag particles. Second, overactivated SSSC exhibit heterogeneous porosity including defects that leads to a decrease of strength and lower mechanical efficiency. Finally, this paper highlights that the increase of strength observed when using hemihydrate is mainly due to the improvement of hydration kinetics, more than a gypsum setting effect.