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International Concrete Abstracts Portal

Showing 1-5 of 221 Abstracts search results

Document: 

19-306

Date: 

September 1, 2020

Author(s):

Rachel E. Henkhaus, Sandra Villamizar, and Julio A. Ramirez

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

The allowable range of epoxy coating thickness specified by ASTM A775/A775M is 175 to 400 μm (7 to 16 mils). This study investigates the impact on structural performance of increasing the upper limit of epoxy coating thickness to 460 μm (18 mils) with respect to deflections, cracking, and bond strength of tension splices. Twenty beam specimens containing single splices as well as splices of bundled bars were tested to failure. The experimental parameters were ranges of epoxy coating thicknesses (300 to 380 μm [12 to 15 mils] and 460 to 530 μm [18 to 21 mils]) and bar sizes No. 16 and 29 [No. 5 and 9]). Test results confirmed the applicability of current code requirements for development and splice length of epoxy-coated bars in tension in ACI 318-14 and AASHTO LFRD 2014, including bars in bundles, up to a coating thickness not to exceed 460 μm (18 mils).

DOI:

10.14359/51727018


Document: 

19-358

Date: 

September 1, 2020

Author(s):

Christoph Mahrenholtz and Akanshu Sharma

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

The world becomes ever smaller and thus the global construction industry moves closer together. For this reason, civil engineers are looking for possibilities to harmonize design—for example, in the field of reinforced concrete structures. The streamlining would ease working in an international context and could offer opportunities for optimization: harmonization allows the identification of the technically best and most economical solution. This also holds for the provisions to calculate the development length of deformed reinforcing bars which, to date, differ notably from code to code. It is not reasonable that local codes define different development lengths for identical situations in terms of geometry and material used. This paper analyzes the provisions for the calculation of the development lengths according to internationally selected national codes as a basis for this discussion.

DOI:

10.14359/51725782


Document: 

18-450

Date: 

March 1, 2020

Author(s):

T. Chandra Sekhara Reddy, A. Ravitheja, and C. Sashidhar

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

The study aimed at examining the capacity of diverse add-ons in improving the self-healing ability of fiber-reinforced concrete through low water-cement ratios (w/c) and exposure to wide cracks. The self-healing capacities of crystalline admixture (CA) and silica fume (SF) were assessed by mechanical and durability performance. The effect of various exposure periods (7 to 42 days) in four different exposure conditions—namely, water immersion, wetting-and-drying cycles, water contact, and air exposure (AE)—on self-healing was evaluated by application of through-crack compressive stress. Compressive strength and durability analysis showed that CA with 10% SF was excellent in all four environments. Fourier transform infrared spectroscopy and scanning electron microscope results showed significant bond formation contributing to the self-healing property of the CAs. Therefore, concrete mixture with CA and 10% SF is recommended for use to increase the self-healing of concrete.

DOI:

10.14359/51722395


Document: 

18-457

Date: 

November 1, 2019

Author(s):

Félix-Antoine Villemure, Mathieu Fiset, Josée Bastien, Denis Mitchell, and Benoit Fournier

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Installation of drilled-in epoxy-bonded reinforcing bars is generally an effective strengthening method to increase the flexural and shear capacities of deficient concrete structures. However, most of the available studies characterizing the bond behavior of epoxy bonded bars in concrete have been carried out on sound concrete elements—that is, without any pathological material damage. This raises the question of bond capacities in existing damaged elements. This study investigates the influence of alkali-silica reaction (ASR) on the capacity of post-installed reinforcing bars. ASR is a deleterious mechanism that causes expansion and cracking in the affected concrete elements. Pullout tests on post-installed reinforcing bars having embedded lengths of 2db, 4db, and 5db with 15M reinforcing bars (db = 15.9 mm [0.626 in.]) have demonstrated a drop-in bond strength when concrete is affected by ASR. In addition, the study revealed that the progression of concrete expansion due to ASR may lead to some confinement of the post-installed reinforcing bar and possibly increases the bond strength.

DOI:

10.14359/51719069


Document: 

17-433

Date: 

November 1, 2019

Author(s):

Er-yu Zhu and Ze-wen Zhu

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

A total of 16 pullout specimens were tested to investigate the effect of curing conditions on bond behavior of near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strengthening concrete under curing temperatures from 35 to 65°C (95 to 149°F) and curing times from 6 to 12 hours. It was compared to that of specimens in ambient conditions (16°C [60.8°F]). On these bases, a nonlinear local bond-slip model was proposed. Two key parameters—A and B—are employed in the proposed bond-slip model, the specific expressions of which were mainly related to ultimate pullout load and peak shear stress of the specimen. The results show that the bond behavior of CFRP strip represents a negative quadratic curve with curing temperature and positive inverse tangent curves with curing time, respectively. The nonlinear local bond-slip model, considering the curing temperature-time, is deduced and validated.

DOI:

10.14359/51719148


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