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International Concrete Abstracts Portal

Showing 1-5 of 107 Abstracts search results

Document: 

SP-349_01

Date: 

April 22, 2021

Author(s):

Carol Namnoum, Benoît Hilloulin,Maxime Robira, Frédéric Grondin, Ahmed Loukili

Publication:

Symposium Papers

Volume:

349

Abstract:

The production of cement by calcination of limestone releases large amounts of carbon dioxide. Development of concrete quality lead to optimize the sustainability and maintenance phases of concrete structures, so, using supplementary cementitious materials (SCM) is one of the methods adapted to reduce the environmental impact of cement production. In addition, self-healing of concrete appears as a process to considerably improve the durability of a damaged structure [1]. As revealed by most analyses, mineral additions can be used to improve the autogenous healing ability of cementitious materials [2].

In this study, the influence of using a combination of SCMs, such as ground granulated blast furnace slag and metakaolin, on the mechanism of autogenous crack healing was assessed in ternary formula. Self-healing evolution was characterised by means of mechanical tests carried out on notched mortar samples with different substitution ratios. The mechanical recovery was investigated after the healing period. Moreover, the micro-chemical structure of the healing products was determined using various techniques (TGA, SEM/EDS and XRD). The primary results showed that using metakaolin and ground granulated blast furnace slag together greatly improve the healing efficiency.


Document: 

SP-349_09

Date: 

April 22, 2021

Author(s):

Dima Kanaan and Ahmed Soliman

Publication:

Symposium Papers

Volume:

349

Abstract:

The feasibility of producing “just add water” alkali-activated self-consolidated (AASCC) mixtures using multi-powder activators and various cement-less binder combinations was evaluated in this study. During this study, fresh properties for mortar mixtures were evaluated by conducting the mini-slump flow test. Moreover, the relative performance of activated mortars and potential interactions among materials used in the mixtures was examined using the isothermal calorimeter. The performance of the hardened mortar mixtures was evaluated after 3, 7 and 28 days by conducting compressive strength tests. Results indicated an increase in the mechanical properties was observed while increasing the dry-powder activator ratio and source material nature for ground and non-ground mixtures.


Document: 

SP-349_27

Date: 

April 22, 2021

Author(s):

Jean-Martin Lessard, Guillaume Habert, Arezki Tagnit-Hamou and Ben Amor

Publication:

Symposium Papers

Volume:

349

Abstract:

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.


Document: 

SP-349_39

Date: 

April 22, 2021

Author(s):

Luigi Coppola, Denny Coffetti, Elena Crotti and Gabriele Gazzaniga

Publication:

Symposium Papers

Volume:

349

Abstract:

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.


Document: 

SP-345_06

Date: 

February 1, 2021

Author(s):

Marco Carlo Rampini, Giulio Zani, Matteo Colombo and Marco di Prisco

Publication:

Symposium Papers

Volume:

345

Abstract:

Fabric-reinforced cementitious matrix (FRCM) composites are promising structural materials representing the extension of textile reinforced concrete (TRC) technology to repairing applications. Recent experiences have proven the ability of FRCMs to increase the mechanical performances of existing elements, ensuring economic and environmental sustainability. Since FRCM composites are generally employed in the form of thin externally bonded layers, one of the main advantages is the ability to improve the overall energy absorption capacity, weakly impacting the structural dead weights and the structural stiffness and, as a direct consequence, the inertial force distributions activated by seismic events. In the framework of new regulatory initiatives, the paper aims at proposing simplified numerical approaches for the structural design of retrofitting interventions on existing reinforced concrete structures. To this purpose, the research is addressed at two main levels: i) the material level is investigated on the uniaxial tensile response of FRCM composites, modeled by means of well-established numerical approaches; and ii) the macro-scale level is evaluated and modeled on a double edge wedge splitting (DEWS) specimen, consisting of an under-reinforced concrete substrate retrofitted with two outer FRCM composites. This novel experimental technique, originally introduced to investigate the fracture behavior of fiber-reinforced concrete, allows transferring substrate tensile stresses to the retrofitting layers by means of the sole chemo-mechanical adhesion, allowing to investigate the FRCM delamination and cracking phenomena occurring in the notched ligament zone. It is believed that the analysis of the experimental results, assisted by simplified and advanced non-linear numerical approaches, may represent an effective starting point for the derivation of robust design-oriented models.


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