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

Hardening and strengthening of cement-concrete compositions (CCC) is a result of forming a moist capillary porous body. Physical water contained in pores and capillaries of the resulting structure is its most informative component. First, it is only the pore solution that is electrically conductive component, and, second, the liquid phase stays perpetually in a thermodynamic equilibrium with the solid surfaces by which it is adsorbed. Thus the physical-moisture state immediately responds to any change in the material’s solid skeleton of hardening CCC.

These effects serve as a physical basis for the CCC hardening and strengthening monitoring using the results ofcontinuous measurement of electric resistivity. Such monitoring is aimed at controlling various properties of the material: from the initial viscous fluid or viscous plastic state of fresh mixtures to the final elastic state of artificial stone. The results of measuring the electric resistivity are compared to those of standard tests. Thus established relationships “Electric resistivity ( ρ ) – Parameters ( i P )” (Parameters: W/C, Slump, Setting Time, Plastic strength, Compressive Strength) allow to carry out technological monitoring over the entire range of CCC hardening. All correlations P_i = f (ρ ) are described by linear relations with high correlation coefficients.

The linearity of the correlations “Strength – Electric Resistivity” is characteristic of various CCC: regular dense concrete, dry concrete mixtures (W/C ≈ 0.35), shotcrete, rising and plastic strengthening of aerated concrete at the stage of preautoclave hardening, etc.

Reducing Normal Portland Cement (NPC) has been a major concern of concrete industry and research community over the last 2-3 decades. As much as 8% of the global CO₂ emissions stem from clinker production. Hence, a wide number of research projects have been focusing on reducing NPC in cementitious materials using numerous strategies such as the use of supplementary cementing materials (SMC’s), limestone fillers (LF) and/or advanced mixproportioning techniques. Yet, the impact of these procedures on the overall behaviour of materials with low NPC content, especially in the fresh state and long-term durability, is still not fully understood. This work aims to understand the influence of the distance between the fine particles, the so-called Inter-Particle Separation (IPS), on the fresh state behaviour of cement-base pastes designed through the use of Particle Packing Models and incorporating LF. Evaluations on the fresh (i.e. rheological behaviour and setting time) and hardened states (compressive strength) were conducted in all mixtures. Results show that IPS directly correlates with the viscosity of cementbase pastes for all shear rates appraised. Moreover, the use of LF increases the hydration rate of NPC pastes. Finally, it is clear that the water-to-cement ratio keeps being the main factor controlling the compressive strength of cement pastes with reduced NPC content and high levels of LF replacement.

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 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.