ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 111 Abstracts search results

Document: 

SP-333_08

Date: 

October 1, 2019

Author(s):

Needa Lingga, Yasir Saeed, Anas Yosefani, and Franz Rad

Publication:

Symposium Papers

Volume:

333

Abstract:

This research focused on concrete beams with voids simulating beams with fully corroded steel that were repaired with CFRP laminates. The experimental program included testing five, approximately one-third-scaled simply supported rectangular concrete beams. In three beams, the oiled steel rebars for flexure and shear were safely pulled out of the formwork after the concrete had cured for six hours, leaving voids. This technique was used to represent an extreme case of corrosion, albeit non-realistic, that is even worse than being exposed to the most corrosive environment. The aim was to investigate the extent of improvement by CFRP to flexural and shear capacity of beams that contain fully corroded steel bars, simulated by voids. The first specimen was with voids representing completely deteriorated steel. The second was a plain concrete beam without voids. The third beam was a typical code-designed reinforced concrete (RC) beam, that represented the “original undeteriorated” beam. The two remaining deteriorated beams were repaired by externally bonding one and two layers of CFRP. Load carrying capacity, deflection, and ductility were measured and compared. The novel results of this investigation were that test results showed that one layer of CFRP increased the load capacity to slightly higher than the RC beam, and two layers of CFRP increased it by a factor of two. Finally, a computer model was created to estimate the performance of the tested beams and to carry out a parametric study to investigate the effects of CFRP longitudinal reinforcement ratio and CFRP transverse confinement ratio on the flexural performance of CFRP-repaired concrete beams. The predicted contribution of CFRP to flexure and shear capacities was in good agreement with test results.


Document: 

SP327-29

Date: 

November 1, 2018

Author(s):

Mostafa Yossef, An Chen and Austin Downey

Publication:

Symposium Papers

Volume:

327

Abstract:

Insulated concrete sandwich panels are composed of two concrete wythes separated by an insulation layer and connected by shear connectors. This paper develops a multifunctional photovoltaic (PV) integrated insulated concrete sandwich (PVICS) panel, which can act as a passive energy system through the insulation layer and an active energy system by harvesting the solar energy using attached thin-film solar cells. The panel features an innovative co-curing scheme, where solar cells, Fiber-Reinforced Polymer (FRP) shell, and polymer concrete are manufactured together to act as a formwork for the sandwich panel. The objective of this paper is to prove the concept of PVICS based on bending test, Finite Element (FE) analysis and analytical study. It can be concluded that the test results correlate well with those from the FE and analytical models. FRP shell can act as both shear connectors and reinforcement. The panel achieved 82% Degree of Composite Action, which can provide enough strength and stiffness. Solar cells worked properly under service load. Shear-lag effect was observed for the strains along the width of the panel.


Document: 

SP326-123

Date: 

August 10, 2018

Author(s):

Laurent Libessart, Amine Lahlou, Chafika Djelal, Yannick Vanhove, and Sandrine Mateo

Publication:

Symposium Papers

Volume:

326

Abstract:

The concrete is the ultimate building materials today and answers all the requirements of the modern architecture. The emulsion or the release agents are used to facilitate the concrete demoulding and to protect the formwork surfaces against corrosion. The final quality of the facings depends on the physicochemical characteristics of the demoulding products used. They must be selected according to the nature of the formwork and their compatibility with the casing skins. They must be consistently applied to the unit of the formwork, to a clean surface, in thin layers, uniform thickness. This agent must allow a placement of the more effective concrete while adhering perfectly to the formwork. The adherence of oil with the support is thus very important. It is studied by the determination of the adhesion energy Solid/Liquid on a formwork surface. This study is interested more particularly in the emulsions. Two forms are distinguished: Mineral reverses emulsion with the dispersed phase is water and Vegetable direct emulsion with the dispersed phase is oil. The first physicochemical results show an influence of the temperature on the adhesion energy. The quality of the concrete facings demoulded with emulsions appears better qualities that those carried out with oils demoulding.


Document: 

SP326-62

Date: 

August 10, 2018

Author(s):

Valeriy Dorf, Rostislav Krasnovskiy, Dmitriy Kapustin, Patimat Sultygova, and Nina Umnyakova

Publication:

Symposium Papers

Volume:

326

Abstract:

The results of an experimental campaign on the thermal conductivity of a mortar (cement + sand) containing various amounts of steel fibers are presented in this study. Increasing the amount of steel fibers (from 0 to 6% by volume) is shown to reduce the thermal conductivity of SFRC, by the extra porosity induced by the fibers and contact thermal resistance. To show the possible benefits coming from the use of SFRC, the case of SFRC formworks is presented, as these formworks may be used in the fire protection of R/C members, as expendable permanent formworks. To this purpose, the finite-element analysis of an R/C member protected by a SFRC formwork is presented, to assess the effectiveness of this kind of fire protection


Document: 

SP325-01

Date: 

July 25, 2018

Author(s):

Ufuk Dilek

Publication:

Symposium Papers

Volume:

325

Abstract:

This paper summarizes the planning and execution stages of a critical mass concrete placement performed during summer months. The subject structure was a critical component of a large heavy industrial facility, consisting of large load bearing elevated flexural members. The planning and execution of this critical mass placement consisted of multiple tasks.

A laboratory study was performed for the purpose of making improvements to the mixture proportions existing and currently in use, admixture dosages and investigating placement temperature options. Adiabatic and semi adiabatic temperature rise was also measured during the laboratory study along with set times. Final proportions and admixture dosages were selected as a result of the laboratory phase. Primary outcome was increase in fly ash percentage from the existing mix design to control heat of hydration.

Based on the findings of the measured adiabatic temperature rise, a thermal control plan was developed adapting the new approach to structural mass concrete placements. A thermal protection/insulation regimen was developed using the mix parameters, expected ambient temperatures following placement, member dimensions and formwork/blanket insulation properties. The pre-placement modifications to the mixture proportions and the delivery temperature requirements protected the concrete against high internal temperatures and potential of Delayed Ettringite Formation (DEF), while the insulation regimen protected the concrete against rapid cooling and occurrence of thermal gradients between core and perimeter.

As part of the thermal control plan analysis, target placement temperatures were recommended to control maximum temperatures to prevent occurrence of DEF, in light of the heat rise of the modified mix. The placement temperature was accomplished by starting the placement at night and the use of ice to draw the temperature down. Upon completion of finishing, a curing compound was applied in lieu of water curing and the placement was insulated.

The thermal control plan simulation predicted a gradual reduction in the temperature of the placement, within limits of maximum internal temperatures and temperature gradients. The actual placement was monitored for core and perimeter temperatures using maturity probes. Monitoring enabled the team to react to abrupt changes in temperature if any was to occur. The placement was completed successfully with internal temperatures and gradients controlled within the desired ranges.


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.