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International Concrete Abstracts Portal

Showing 1-5 of 459 Abstracts search results

Document: 

SP-349_18

Date: 

April 22, 2021

Author(s):

Ivan Janotka, Michal Bačuvčík, Peter Paulík, and Lukáš Húlek

Publication:

Symposium Papers

Volume:

349

Abstract:

A layer of 2-4 mm (0.08-0.16 in) protective render coat (PRC) has proven to be an effective anticarbonation barrier at two bridges protecting the underlying concrete against carbonation for 100 years. The carbonation of concrete under the PRC with low permeability was found to be less than 2 mm (0.08 in). It is assumed that the PRC was placed for aesthetic purposes. Taking into account the considered XC3 exposure class according to EN 206, to which concrete structures were subjected and compressive strengths of the underlying concrete between 20 - 25 MPa (2900 - 3625 psi), low carbonation depth can be explained by the presence of the PRC applied on concrete surface. The main scientific goal of this article is to explain the cause of extremely low carbonation depth of concrete under the PRC. Its composition has been unknown until now but the present research reveals the secret of this substance. Investigations of the aspects of low carbonation depth thoroughly focused on the PRC role covering concrete beneath as well as material development of new current PRC based on the present cement and sand, without the use of chemical admixtures, are also the subject of ongoing research.


Document: 

SP-349_53

Date: 

April 22, 2021

Author(s):

Thomas, M.D.A., Smith, D. and Moffatt, E.G., Kasaniya, M.

Publication:

Symposium Papers

Volume:

349

Abstract:

This paper presents data on the durability of concrete produced using ground glass as a pozzolan. Various sources of glass were used including soda glass, E-glass and Pyrex glass. All the materials showed excellent pozzolanic activity when ground to pass 75-microns. The use of ground glass resulted in substantial reductions in permeability and chloride penetrability, and improved resistance to sulfate attack. Air-entrained concrete containing glass showed good freeze-thaw resistance. Low alkali E-glass and borosilicate glass were effective in preventing deleterious expansion due to alkali-silica reaction (ASR). Bottle glass, which contains substantial amounts of alkali, was not efficacious with regards to ASR. The inclusion of bottle glass results in very substantial increases to the pore solution alkalinity and this can result in substantial increases in expansion in concrete containing reactive aggregate and low-alkali cement. It is shown that the accelerated mortar bar test is not suitable for evaluating the impact of high-alkali materials on ASR as the alkalis contributed by the cementing materials are released when the mortar bars are masked by the conditions of the test (first immersed in hot water and then in hot NaOH solution).


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.


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