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

Calcined clays represent a promising future supplementary cementitious material (SCM) because of the worldwide availability of suitable clays and low material-related CO₂ emissions during calcination. The application of superplasticizers is inevitable for a secured workability of cementitious systems with calcined clays due to their specific chemophysical properties. For their prospective use as SCM, a sound knowledge is elementary about the interaction of calcined clays with superplasticizers depending on clay and polymer structure. An ordinary Portland cement is replaced by 20 wt% of calcined clays. Four different calcined materials are used: one calcined clay mixture, industrial metakaolin, a metaillite and a metamuscovite. One polycondensate and one polycarboxylate-based polymer, both industrial products, are chosen as superplasticizers. The required dosages are adjusted by the same slump flow, so a similar dispersing behavior for all systems is given immediately after water addition. Over a period of two hours after water addition, the rheological behavior is evaluated via mini slump test and by rotational viscometer. The impact of different velocities during measurements with the viscometer provides further information related to the viscosity of these systems.

Scrap tyres are one of the most serious wastes that are landfilled with small percentages. Recycled scrap tyres are being used in different domains of industry because they are notdegradable. The experimental work focused on mechanical properties and durability indicators of self-compacting sand concretes blended with recycled rubber. Such modified concretes comprised 5, 10, 15 and 20% of rubber fine powder (RFP) and coarse particles (RCP) as partial substitutions of natural sand and aggregates. To shed light on physical and mechanical properties rubber particles effects, ordinary vibrated and self-compacting as well as self-compacting sand concretes (SCSCs) were characterised. Special attention was given to compression and bending performances of SCSCs. Identification of two durability indicators — water porosity and density — was assessed, according to AFGC specifications. Experimental findings enhanced previous literature reported statements and demonstrated that use of rubber particles as substitutes improved performances of elaborated SCSCs and produced eco-friendly materials that are appropriate for large surface applications such as pavements and terraces as well as civil engineering constructions.

Recent studies focused on the quality of the interfacial transition zone (ITZ) of ordinary concretes made from recycled aggregates (RA), without however focusing on High Performance Concretes (HPC).

This paper aims to formulate HPC from RA that are exclusively derived from concrete, whose composition is controlled. These concretes are made in a ready-mixed concrete plant and then undergo a crushing and riddling process to produce RA. Partially saturated gravels are substituted up to 100% in the HPC composition in order to accentuate internal cure phenomenon. This phenomenon was observed and demonstrated using a scanning electron microscope (SEM) in the low Water/Cement (W/C) paste up to a distance of 150 μm from the RA and compared by image processing, to a reference concrete made from natural aggregates (NA).

The comparison of the mechanical performances and the microscopic analysis of HPC show that the characteristics transfer of the RA seem to favor a hydration of the paste by a mechanism of desorption of their absorbed water, in a process of “internal cure”. The internal cure appears optimal for concrete C60. In addition to this observation, there was an increase in the strength of the recycled HPCs compared to control natural-aggregate HPCs.

The utilization of recycled concrete as an adsorbent to sequester NO₂ without additives or catalysts is an innovative, cost-effective, and sustainable approach to capture NO₂ from targeted industrial facilities. During NO2 sequestration, alkaline products such as calcium hydroxide (CH) in the adhered old mortar of recycled concrete can react with NO₂ to form Ca(NO₂)₂ and Ca(NO₃)₂. Thus, the use of NO₂ sequestered recycled concrete aggregates (NRCA) as a constituent of concrete can be beneficial since Ca(NO₂)₂ and Ca(NO₃)₂-based chemical compounds are widely used as multi-functional admixtures for concrete applications. This study investigates the influence of the properties of the parent (demolished) concrete on the mechanical and durability performance of NRCA incorporated ordinary portland cement (OPC) concrete. Two types of recycled concrete aggregate (RCA) were derived from 2 and 20-year old concrete blocks to produce two types of NRCA—2-NRCA (2-year-old NRCA) and 20-NRCA (20-yearold NRCA) by exposing them to a humidified air/NO₂ mixture (at RH = 50% and 23±2°C) for two weeks. NRCA was used as a partial replacement for natural fine aggregate in fresh OPC mixtures at 20% and 40% rates by volume. The influence of NRCA on concrete compressive strength, porosity, and long-term chloride diffusion coefficients were assessed. In addition, open-circuit and potentiodynamic polarization tests were conducted to evaluate the resistance to chloride-induced corrosion of steel in concrete. Control test mixtures containing a commercially available Ca(NO₂)₂ based corrosion inhibitorwere also tested for comparison purposes. Both types of NRCA enhanced the mechanical and durability properties of concrete compared to control mixtures. Test mixtures containing 2-NRCA showed better resistance against chloride-induced corrosion than concrete with 20-NRCA.