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International Concrete Abstracts Portal

Showing 1-5 of 457 Abstracts search results

Document: 

SP-343_40

Date: 

October 1, 2020

Author(s):

Turgeon-Mallette, V.; Sorelli, L.; Conciatori, D.; Réthore, J.

Publication:

Symposium Papers

Volume:

343

Abstract:

The capacity of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) to develop multiple micro-cracks instead and delay the localization of major cracks has great impact on the permeability and durability at serviceability state. In order to assess the durability of reinforced UHPFRC structures or rehabilitation layers, methods that accurately predict the microcrack width are necessary. This work aims at assessing the accuracy of some current analytical models to predict the crack width and growth of reinforced UHPFRC beam in bending by means of Digital Image Correlation (DIC) analysis of 4-point bending tests. DIC analysis was successfully employed to estimate the microcrack width and their spacing during loading. In particular, the following methods for predicting the growth of cracks of a reinforced FRC member are considered: (i) Eurocode 2; (ii) RILEM TC 162-TDF; (iii) the one proposed by Moffatt; (iv) the one proposed by Deluce. As expected Eurocode crack model overestimates the crack width as it does not consider the fiber contribution. RILEM and Moffatt models well predict the maximum crack width, but Deluce method is the most accurate to predict the mean crack width. The estimation of the crack spacing seems to the be critical factor which may require further improvement, especially for the crack spacing at serviceability states.


Document: 

SP-343_41

Date: 

October 1, 2020

Author(s):

Ding, Y.;Li, D.; Zeng, W.

Publication:

Symposium Papers

Volume:

343

Abstract:

The water permeability of the concrete with cracks has been studied in this paper. Cylindrical specimens with different fiber contents were pre-cracked, and specimens without any fiber reinforcement were also investigated as reference. The water permeability of the specimens with different crack width was measured by hydraulic permeability test. The measured data of the crack surface was collected by the self-developed data acquisition system, the total crack length and surface area of the samples were analyzed, the geometrical property of crack (tortuosity and roughness) was evaluated quantitatively. The results showed that the tortuosity and roughness of the cracked surface can be increased greatly by addition of the macro steel fiber. The coefficient of the water permeability of the specimens followed the Poiseuille law by considering of the influence of the crack geometrical property.


Document: 

SP-340-05

Date: 

April 1, 2020

Author(s):

Nakin Suksawang and Hani Nassif

Publication:

Symposium Papers

Volume:

340

Abstract:

For many decades, latex-modified concrete (LMC) overlays have been successfully used in the United States, inclusive of providing protection for many bridge decks and their steel reinforcements. LMC remains one of the most desirable rehabilitation materials for concrete bridge decks because it is easier to place and requires minimal curing. Nevertheless, as is the case with any cement-based material, LMC overlays are susceptible to plastic shrinkage and delamination. These problems are often solved by proper curing and better surface preparation. Yet, despite these solutions, many questions have been raised regarding the best practices for placing LMC overlays and the proper curing and placement conditions. The current curing practice for LMC in most states simply follows the latex manufacturer’s recommendation because very little information on the proper curing methods is available. There is a need to establish detailed technical specifications regarding curing and placement conditions that will provide more durable LMC overlays. This paper provides an in-depth laboratory-based experimental study of the effect of curing methods and duration on the mechanical properties and durability aspects of LMC. Four different curing methods were examined: (1) dry curing, (2) 3 days of moist curing, (3) 7 days of moist curing, and (4) compound curing. Based on the results from the laboratory tests, technical specifications were developed for field implementation of LMC. Various types of sensors were installed to monitor the behavior of the LMC overlays on bridge deck. Results show that extending the moist-curing duration to a minimum of 3 days (and a maximum of 7 days) significantly improves both the mechanical properties and durability of LMC.


Document: 

SP-337_06

Date: 

January 23, 2020

Author(s):

Edward (Ted) Moffatt, Michael Thomas and Andrew Fahim

Publication:

Symposium Papers

Volume:

337

Abstract:

In 1978, the Canadian Centre of Mineral and Energy Technology (CANMET) initiated a longterm study to determine the performance of concrete in a marine environment. Between 1978 and 1994, over three hundred prisms as part of 14 different experimental phases were placed at the mid-tide level at the Treat Island exposure site. Treat Island is an outdoor exposure site operated by the U.S. Army Corps of Engineers, and lies in the Passamaquoddy Bay, part of the Bay of Fundy, near the town of Eastport in Maine. Following 25 years of exposure, the blocks were retrieved after being exposed to tidal conditions representing approximately 18,250 cycles of wetting and drying, and 2,500 cycles of freezing and thawing. This paper presents the durability performance of concrete from several phases of the CANMET study. This includes concrete incorporating various levels of supplementary cementing materials (up to 80% by mass of cementing material in some cases), with normal density and light-weight aggregate. The paper also compares output from the service-life model Life-365 with experimental chloride profile data. The results indicate the efficacy of SCMs in increasing the concrete resistance to chloride penetration. However, use of very high levels of these materials was found to render the concrete more susceptible to surface scaling. The results also showed that Life-365 model can predict chloride penetration adequately with very simple inputs.


Document: 

SP-336_04

Date: 

December 11, 2019

Author(s):

Yu Jiang, Gang Xu, Zhipeng Li, and Xianming Shi

Publication:

Symposium Papers

Volume:

336

Abstract:

In this study, we tested compressive strength, rheology, initial setting time and transport properties of mortar samples mixed with green corrosion-inhibiting admixtures were tested. Four types of green corrosion inhibitors were adopted, which were extracted from peony leave, Kentucky blue grass, sugar beet leave and dandelion. All of them affected the compressive strength adversely but improved other properties of mortar samples. Resistance of mortar to chloride induced corrosion was evaluated using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. The results indicated that these green corrosion-inhibiting admixtures provided promising inhibiting performance under chloride environment. The results also suggested these green corrosion-inhibitors have the potential to be used as multifunction corrosion inhibitors for concrete, such as serving as water reducer and set retarder. Future work would focus on chemical mechanism of green corrosion inhibitors and the comparative evaluation of these green corrosion inhibitors with other commercially available corrosion inhibitors.


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