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International Concrete Abstracts Portal

Showing 1-5 of 132 Abstracts search results

Document: 

19-188

Date: 

March 1, 2020

Author(s):

Kai Jiao, Chen Chen, Lei Li, Xun Shi, and Yong Wang

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

To promote the application of pervious concrete (PC) in heavy-duty pavement engineering, a thick plate (approximately 50 to 100 cm) paving structure can be used, and its failure form mainly by fatigue compression. Therefore, compressive fatigue tests were carried out under fatigue loads in four stress levels (S): 0.6, 0.7, 0.8, and 0.9, at three loading frequencies of 10, 15, and 20 Hz. The results showed that the fatigue life (N) and fatigue residual strength are controlled by S, while loading frequency showed no statistically significant effect on them. The fatigue failure of PC will not occur under a stress level of 0.6. The survival rate of PC and the fatigue life of uniaxial compression obey a Weibull distribution with two parameters. The material constants of uniaxial compression fatigue of PC are 0.0464 to 0.052, which are similar to ordinary concrete. There are two forms of fatigue failure: one is the shearing along the vertical central axis and the other is shear failure at an angle of 15 to 30 degrees with the vertical central axis.

DOI:

10.14359/51722402


Document: 

19-137

Date: 

March 1, 2020

Author(s):

Assem A. A. Hassan

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

This study investigated the structural behavior of large-scale rubberized self-consolidating engineered cementitious composite (SCECC) beams designed to fail in shear. Specifically, the experimental program focused on the use of crumb rubber (CR) and powder rubber (PR) in SCECC as a partial replacement of silica sand at replacement levels of 0, 10, 20, and 30% (by volume). All cast SCECC, SCECC-CR, and SCECC-PR beams were compared with the performance of normal self-consolidating concrete (SCC) beam (containing coarse aggregates) at comparable compressive strength. The results obtained from this study included the fresh and mechanical properties of the developed mixtures, in addition to load-deflection curves, cracking behavior, first flexural crack load, diagonal crack load, ultimate load, ductility, and energy absorption capacity of the tested beams. The performance of some code-based equations in estimating the ultimate capacity and cracking moment of the tested beams was also evaluated. The results showed that all SCECC, SCECC-CR, and SCECC-PR beams exhibited higher performance compared to that exhibited by the normal SCC beam. However, the inclusion of either CR or PR in SCECC led to a reduction in the first crack load, diagonal crack, and ultimate load capacity of SCECC. The ductility and energy absorption capacity of SCECC was found to increase when 10% CR was introduced, while further increase in the percentage of CR decayed both the ductility and energy absorption capacity. On the other hand, the use of PR with up to 30% contributed to improving the deformability of the SCECC beam with no significant loss in its load-carrying capacity, thus providing a sustainable composite with higher ductility and energy absorption.

DOI:

10.14359/51720300


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: 

18-457

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: 

18-309

Date: 

July 1, 2019

Author(s):

X. Wirth, D. Benkeser, N. N. Nortey Yeboah, C. R. Shearer, K. E. Kurtis, and S. E. Burns

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

Due to changes in energy production and increased emissions regulations, fly ashes that meet specifications for concrete production are becoming increasingly limited in North America. Woody biomass ash, ash from coal that has been co-fired with small amounts of biomass, and previously geologically disposed, weathered coal fly ashes are each vast and geographically distributed potential sources which could augment the limited supply of “on-spec” or ordinary fly ash. This study characterizes a range of these alternative ash sources to assess if they fulfill the physical and chemical requirements and the strength performance index in ASTM C618. Changes to ASTM C618 that address the current fly ash production environment are recommended, including broadening the definition of fly ash to allow for reclaimed weathered ashes, co-fired ashes, and blended ashes that meet prescriptive and performance specifications.

DOI:

10.14359/51716712


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