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International Concrete Abstracts Portal

Showing 1-5 of 287 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_43

Date: 

April 22, 2021

Author(s):

Yassine El Khessaimi, Youssef El Hafiane, and Agnès Smith

Publication:

Symposium Papers

Volume:

349

Abstract:

Ye’elimite-rich cements or calcium sulfoaluminate cements (CSA) are commercialized to prepare shrinkage compensation and self-stressing concretes. Moreover, CSA cements show environmentally friendly characteristics associated to their production, which include reduced CO2 footprint. The expansive behavior of CSA cements is mainly controlled by ettringite amount, produced upon hydration of the key-phase, ye’elimite [Ca4(Al6O12)SO4]. This paper presents, on one hand, the optimal conditions for the synthesis of highly pure ye’elimite by solid state reactions, and on the other hand, it shows a fundamental description of ye’elimite formation mechanisms. Another aspect of the study encompasses the influence of fineness and citric acid addition on ye’elimite phase dissolution, then on hydrates composition of lab made ye’elimite-rich cement. For the fineness effect study, a highly fine and pure ye’elimite was originally synthetized by sol-gel methods. Various experimental techniques were performed to conduct the different aspects of the present study, namely XRD-Quantitative Rietveld analysis, Thermal analysis (TGA, DTA and Dilatometry), SEM (BSE imaging and EDS mapping), BET analysis, PSD by laser diffraction, and Image analysis (2D porosity and 2D PSD).


Document: 

SP-349_31

Date: 

April 22, 2021

Author(s):

Tim Schade and Prof. Dr. Bernhard Middendorf

Publication:

Symposium Papers

Volume:

349

Abstract:

Compared to normal concrete, packing density optimised Ultra High Performance Concretes have a high shrinkage up to 1 mm/m due to their high cement content. Especially in the first 24 hours approximately 80 % of the final shrinkage is reached which reduces the early strength due to microcracks. Instead of additives within the scope of this research work, parts of normal portland cement (NPC) were substituted by Calcium Sulfoaluminate (CSA) Cement and Calcium Aluminate (CA) Cement with the aim to reduce shrinkage of UHPC-mixture as well as a fast setting. CSA-cements with low CO2 footprint are characterised by their fast strength development and expansion behaviour due to early ettringite formation. X-ray diffraction was used to study the phase development. The influence on the shrinkage value was measured by shrinkage tests. In addition, the development of the microstructure was investigated by scanning electron microscopy. Finally, the influence on the strength development was correlated by ultrasonic measurement. These techniques allow a prediction of the setting process in the early stages. Finally, an environmentally friendly NPC-CSA blend could be developed which, in addition to high early strength, also achieves low shrinkage. Furthermore, the influence of the ettringite formation on the microstructure could be determined.


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.


Document: 

SP-346_07

Date: 

January 1, 2021

Author(s):

Joseph Losaria, Steven Nolan, Andra Diggs II, and David Hartman

Publication:

Symposium Papers

Volume:

346

Abstract:

This case study highlights the use of Fiber Reinforced Polymer (FRP) materials on the US 41 Highway Bridge over North Creek in Sarasota County near the Florida Gulf Coast. Design and construction involved the use of Glass-FRP (GFRP) reinforcement on the cast-in-place (CIP) concrete flat slab superstructure, Carbon-FRP (CFRP) prestressing strands on the concrete piles, and GFRP reinforced precast panels for the substructure combining a bridge bearing abutment and retaining wall system. The application of FRP prestressing and reinforcing is promoted by the Florida Department of Transportation (FDOT) under their Transportation Innovation Challenge initiative. Soldier-pile retaining walls are a commonly used system in southeastern US coastal states, but the incorporation of innovative materials such as CFRP-prestressing for piles and GFRP-reinforcing for concrete panels is not yet widespread. Comparison of lateral stability results of this wall system during construction and in the final condition is discussed. In addition, to describing the preferred FRP-PC/RC solution adopted for this project, a comparison is provided to a recently completed adjacent bridge that utilized a conventional carbon-steel PC soldier-pile and RC precast panel wall system. A further comparison is presented for the design and cost of the wall system based on the project design criteria (ACI 440.1R, ACI 440.4R, and 2009 AASHTO LRFD Bridge Design Guide Specifications for GFRPReinforced Concrete, 1st Edition) with the refinements and savings possible under the newer editions. Finally, the life-cycle cost, durability and environmental benefits from the use of the innovative CFRP and GFRP reinforcing systems in this type of traditional wall system, are identified for typical urban coastal areas with extremely aggressive conditions, congested access, and challenging environmental constraints.


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