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International Concrete Abstracts Portal

Showing 1-5 of 219 Abstracts search results

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: 

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


Document: 

18-456

Date: 

November 1, 2019

Author(s):

Joseph J. Assaad, Najib Gerges, Kamal H. Khayat, Najib Lattouf, and Jimmy Mansour

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

A comprehensive research project was undertaken to evaluate the effect of styrene butadiene rubber (SBR) latex admixture on washout loss and bond strength of underwater concrete (UWC) designated for repair applications. Three UWC series possessing low to high stability levels that incorporate 5 to 15% SBR, by binder mass, were tested. A 1.5 m (4.93 ft) long specially designed channel was developed to enable the UWC to free fall from the outlet of a V-funnel apparatus, flow along an inclined surface submerged in water, then spread onto a horizontal concrete surface. Results show that underwater casting leads to reduced pulloff strengths caused by washout loss and aggregate segregation that weaken in-place properties. The incorporation of SBR was particularly efficient to reduce washout loss and improve adhesion between the repair overlay and substrate. Regression models enabling the prediction of residual bond strengths from the UWC rheological properties, washout loss, and polymer content are established.

DOI:

10.14359/51716982


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: 

18-337

Date: 

September 1, 2019

Author(s):

Dongming Yan, Shikun Chen, Chenglin Wu, Qiang Zeng, and Fan Yang

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

In this work, the dynamic pullout experiments with loading rates ranging from 0.1 to 100 MPa/s (0.0145 to 14.5 ksi/s) were conducted to investigate the bond behavior between the metakaolin-based geopolymer (MKG) concrete and the plain and deformed steel reinforcement. A rate-dependent bonding behavior between the MKG concrete and the steel reinforcement was observed. Using an analytical model, the effects of the dynamic properties of MKG concrete and the interfacial properties at MKG-steel interface were quantitatively characterized. The morphologies of the bonded and failed interfaces were also examined and analyzed, showing different failure mechanisms associated with varying loading rates. These results link the loading rate-dependency of the MKG-steel bonding behavior to the enhanced chemical adhesion at the MKG-steel interface.

DOI:

10.14359/51715586


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