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International Concrete Abstracts Portal

Showing 1-5 of 1048 Abstracts search results

Document: 

SP-349_45

Date: 

April 22, 2021

Author(s):

Bakhta Boukhatem, Ablam Zidol and Arezki Tagnit-Hamou

Publication:

Symposium Papers

Volume:

349

Abstract:

This study presents an accurate corrosion prediction through an intelligent approach based on deep learning. The deep learning is used to predict the time-to-corrosion induced cover cracking in reinforced concrete elements exposed to chlorides ions. The key parameters taken into consideration include thickness, quality and condition of the concrete cover. The prediction performance of the deep learning model is compared against traditional machine learning approaches using neural network and genetic algorithms. Results show that the proposed approach provides better prediction with higher generalization ability. The efficiency of the method is validated by an accelerated corrosion test conducted on 91 and 182-day moist cured reinforced fly ash concrete samples with different water-to-binder ratios. The results are in agreement with the model predictions. They also show that using the proposed model for numerical investigations is very promising, particularly in extracting the effect of fly ash on reducing the extent of corrosion. Such an intelligent prediction will serve as an important input in order to assist in service life prediction of corroding reinforced concrete structures as well as repair evaluation.


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.


Document: 

SP-345_18

Date: 

February 1, 2021

Author(s):

Vikram Dey, Jacob Bauchmoyer, Chidchanok Pleesudjai, Steve Schaef, and Barzin Mobasher

Publication:

Symposium Papers

Volume:

345

Abstract:

The influence of engineered hydrophilic polypropylene fibers in the formation of distributed cracking and the associated strengthening and toughening of cement-based composites under mechanical loading was studied by conducting, correlating, and modeling tensile and flexural tests. An automated filament winding system was used to manufacture continuous fiber composites. Composites with continuous fibers consisting of low modulus surface-modified hydrophilic macro-synthetic polypropylene fibers were compared for their reinforcing ability with fibrillated micro-synthetic fibers. The digital image correlation technique was used for damage characterization using quantitative analysis of crack width, spacing, and correlated with the tensile response and stiffness degradation. It was observed that the mechanical properties as well as crack-spacing and composite stiffness were significantly affected by the microstructure and dosage of continuous fibers. Procedures for correlating tension and flexural test results were introduced using closed-form solution approaches for strain hardening materials.


Document: 

SP-345_15

Date: 

February 1, 2021

Author(s):

Kissila Botelho Goliath, Daniel C. T. Cardoso, and Flavio de A. Silva

Publication:

Symposium Papers

Volume:

345

Abstract:

Textile-reinforced concrete (TRC) is a composite material resulting from the combination of finegrained concrete and textile reinforcement, widely used to strengthen existing structures. In addition, TRC is an alternative to obtain lighter and thinner structures. However, the behavior of these structures depends on the properties of the matrix and fiber used, as well as on the interface between these two phases. In this work, the interface properties of SBR-based carbon textile-reinforced concrete as supplied and after sand-coating treatment are evaluated through pullout tests. Then, to assess the bending behavior of structural members, four-point bending tests were performed on I-section beams using textiles with and without surface treatment. To analyse the evolution of cracking, digital image correlation (DIC) technique was used. The effectiveness of epoxy-sand treatment surface in textile reinforcement improve the bond between textile as well matrix as the failure mode of TRC beams and was confirmed by improved interface properties, i.e. a stiffer and stronger interface was obtained. In addition to the improved crack pattern, it was observed smaller and less spaced cracks.


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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