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International Concrete Abstracts Portal

Showing 1-5 of 58 Abstracts search results

Document: 

20-210

Date: 

July 1, 2021

Author(s):

Tayseer Z. Batran, Mohamed K. Ismail, and Assem A. A. Hassan

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

This study investigated the structural behavior of lightweight self-consolidating concrete (LWSCC) beams strengthened with engineered cementitious composite (ECC). Four LWSCC beams were strengthened at either the compression or tension zone using two types of ECC developed with polyvinyl alcohol (PVA) fibers or steel fibers (SFs). Three beams were also cast in full depth with LWSCC, ECC with PVA, and ECC with SFs, for comparison. The performance of all tested beams was evaluated based on loaddeflection response, cracking behavior, failure mode, first crack load, ultimate load, ductility, and energy absorption capacity. The flexural ultimate capacity of the tested beams was also estimated theoretically and compared to the experimental results. The results indicated that adding the ECC layer at the compression zone of the beam helped the LWSCC beams to sustain a higher ultimate loading, accompanied with obvious increases in the ductility and energy absorption capacity. Higher increases in the flexural capacity were exhibited by the beams strengthened with the ECC layer at the tension zone. Placing the ECC layer at the tension zone also contributed to controlling the formation of cracks, ensuring better durability for structural members. Using ECC with SFs yielded higher flexural capacity in beams compared to using ECC with PVA fibers. The study also indicated that the flexural capacity of single-layer and/or hybrid composite beams was conservatively estimated by the ACI ultimate strength design method and the Henager and Doherty model. More improvements in the Henager and Doherty model’s estimates were observed when the tensile stress of fibrous concrete was obtained experimentally.

DOI:

10.14359/51732635


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: 

19-244

Date: 

May 1, 2020

Author(s):

Hadi Bahmani, Davood Mostofinejad, and Sayyed Ali Dadvar

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

This study investigated the effects of different synthetic and mineral fibers and limestone powder on the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC). For the purpose of this study, 16 mixture designs and 204 prism specimens were prepared and cured under either of wet or autoclave conditions. Measurements revealed that mixtures containing synthetic fibers recorded considerable compressive and flexural strengths close to the steel fiber-reinforced mixtures. Specimens reinforced with nylon fibers as the best fibers in this study exhibited a much better flexural performance in terms of flexural strength, deflection capacity, and post-peak ductility than did those containing ceramic and polyester fibers. Finally, specimens containing limestone powder recorded acceptable flexural strength, which was close to those only containing silica fume. The X-ray diffraction (XRD) test showed that limestone powder increased ettringite content due to the dilution effect at 180 days as the main reason for decreasing of compressive strength of mixtures.

DOI:

10.14359/51724596


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: 

18-235

Date: 

May 1, 2019

Author(s):

Nabila Zemour, Alireza Asadian, Ehab A. Ahmed, Brahim Benmokrane, and Kamal H. Khayat

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

This study investigated the effect of several parameters on the bond behavior of spliced glass fiber-reinforced polymer (GFRP) reinforcing bars in self-consolidating concrete (SCC) and normal concrete (NC). A total of 21 full-scale reinforced concrete (RC) beams were tested under four-point bending up to failure. Six influential design Code parameters were investigated, specifically concrete type, casting position, casting height, splice length, beam height, and longitudinal reinforcement type. The experimental results and observations reveal that the SCC and NC beams behaved similarly in terms of failure load, crack pattern, failure mode, and load-deflection response. The bond strength of the spliced bars in the SCC beams was slightly lower than that of the NC. The SCC beams exhibited lower reductions in bond strength than the NC beams due to the casting-position effect. In addition, the experimental findings confirm that the top-bar factor of 1.3, recommended in current design codes, can provide adequate safety margins for GFRP-reinforced NC and SCC beams with a splice length of 40db. Furthermore, the threshold depth of 305 mm (12 in.) provided in current design codes and guidelines appears to be reasonably safe.

DOI:

10.14359/51714459


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