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Showing 1-5 of 454 Abstracts search results

Document: 

SP349

Date: 

April 28, 2021

Publication:

Symposium Papers

Volume:

349

Abstract:

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


Document: 

SP-349_26

Date: 

April 22, 2021

Author(s):

Maurizio Bellotto, MariaChiara Dalconi, Enrico Garbin, and Gilberto Artioli

Publication:

Symposium Papers

Volume:

349

Abstract:

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 HBO32- ion constitutes the interlayer between positive [Ca2Al(OH)6]+ sheets. These binders set in few hours and harden in one day.


Document: 

SP-349_17

Date: 

April 22, 2021

Author(s):

Hugo Valido Deda, Leandro Francisco Moretti Sanchez, Mayra Tagliaferri de Grazia

Publication:

Symposium Papers

Volume:

349

Abstract:

Although the 28-day concrete compressive strength is often used as a quality control indicator, early-age mechanical properties are becoming more critical to optimize construction scheduling. Numerous advanced techniques have been proposed in this regard and among those, electrical resistivity (ER), a non-destructive and inexpensive technique able to characterize the microstructure development of cementitious materials has been showing promising results. Yet, recent literature data have evidenced that ER might be significantly influenced by a variety of parameters, such as the binder type/amount and aggregates nature used in the mix. These factors can hinder the practical benchmark of concrete mixtures proportioned with distinct raw materials. Thus, six concrete mixtures incorporating two types of aggregates (granite and limestone) and two ground granulated blast furnace slag cement replacements (e.g. 0%, 35%, and 70%) were manufactured for this research. Moreover, three distinct ER techniques (e.g. Bulk, Surface, and Internal) and compressive strength tests were performed at different concrete ages. Results show that the binder replacement may significantly affect ER results over time, whereas the aggregate type presented a less significant impact.


Document: 

SP-349_15

Date: 

April 22, 2021

Author(s):

Jamal Medljy, Hilal El-Hassan, and Tamer El-Maaddawy

Publication:

Symposium Papers

Volume:

349

Abstract:

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.


Document: 

SP-349_35

Date: 

April 22, 2021

Author(s):

Alexandre Rodrigue, Josée Duchesne, Benoit Fournier and Benoit Bissonnette

Publication:

Symposium Papers

Volume:

349

Abstract:

Alkali-activated slag/fly ash concretes activated with combined sodium silicate and sodium hydroxide show good mechanical and durability properties in general. When tested in terms of resistance to freezing and thawing cycling in watersaturated conditions, the concretes tested in this study show final values of relative dynamic modulus averaging 100% after 300 cycles. However, all tested concretes showed poor performance towards freezing and thawing in presence of de-icing salts with only one tested mixture showing a final average scaling value below 0.5 kg/m². Early-age microcracking is observed on all tested concretes and is correlated to high values of autogenous shrinkage in equivalent paste mixtures. Increasing the fly ash content reduces both the observed autogenous shrinkage and early-age cracking. Low drying shrinkage values ranging from 470 to 530 μm/m after 448 days of measurements at 50% RH and 23°C are noted. The use of fly ash in these alkali-activated concretes reduces the expansion levels of concrete specimens incorporating alkali-silica reactive aggregates. With increasing fly ash contents (20, 30 and 40% replacement), decreasing expansions are observed for any given reactive aggregate. In general, the durability properties measured in this study were improved by partially substituting slag with fly ash as binder material.


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