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International Concrete Abstracts Portal

Showing 1-5 of 60 Abstracts search results

Document: 

23-257

Date: 

August 1, 2024

Author(s):

Leigh E. W. Ayers and Isaac L. Howard

Publication:

Materials Journal

Volume:

121

Issue:

4

Abstract:

In this paper, several hundred specimens were compacted and tested to evaluate the potential of beam testing protocols to directly measure four mechanical properties from one beam. Mechanical properties measured through beam testing protocols were compared to properties of plastic mold (PM) device specimens and were found to be comparable once specimen densities were corrected. Mechanical properties were also used to quantify mechanical property relationships, often used as pavement design inputs. When compared to traditionally recommended mechanical property relationships, relationships between elastic modulus and unconfined compressive strength, as well as modulus of rupture and unconfined compressive strength, were overly conservative; however, indirect tensile strength and unconfined compressive strength relationships from the literature were accurate. This paper also assessed an elevated-temperature curing protocol to simulate later-life pavement mechanical properties on laboratory specimens. Mechanical properties of laboratory specimens that underwent accelerated curing were shown to be comparable to 10- to 54-year-old cores taken from Mississippi highways.

DOI:

10.14359/51740780


Document: 

22-353

Date: 

July 1, 2024

Author(s):

Ahmed Elbady, Salaheldin Mousa, Hamdy M. Mohamed, and Brahim Benmokrane

Publication:

Structural Journal

Volume:

121

Issue:

4

Abstract:

The behavior of precast concrete tunnel lining (PCTL) segments reinforced with glass fiber-reinforced polymer (GFRP) bars under punching loads is one area in which no research work has been conducted. This paper reports on an investigation of the punching-shear behavior of GFRP-reinforced PCTL segments induced by soil conditions, such as rock expansion or the geotechnical conditions surrounding a tunnel. Six full-scale rhomboidal PCTL specimens measuring 1500 mm (59 in.) in width and 250 mm (9.8 in.) in thickness were constructed and tested up to failure. The investigated parameters were: 1) reinforcement type (GFRP or steel); 2) reinforcement ratio (0.46 or 0.86%); 3) stirrups as shear reinforcement; and 4) segment length (2100 or 3100 mm [82.7 or 122 in.]). The experimental results are reported in terms of cracking behavior, punching-shear capacity, deflection, strain in the reinforcement and concrete, and failure modes. The results reveal that the GFRP-reinforced PCTL segment was comparable with its steel counterpart with the same reinforcement ratio and satisfied serviceability limits. Increasing the reinforcement ratio and decreasing the segment length enhanced the punching-shear strength. The shear stirrups improved the structural performance and increased the punching and deformation capacities of the GFRP-reinforced PCTL segments. In addition, theoretical predictions of the punching-shear capacity using the current design provisions were compared to the experimental results obtained herein. The theoretical outcomes show the suitability of using current FRP design provisions for predicting the punching capacity of PCTL segments reinforced with GFRP bars.

DOI:

10.14359/51740709


Document: 

21-500

Date: 

May 1, 2023

Author(s):

Pierre van Tonder and Christoff Cornelis Kruger

Publication:

Structural Journal

Volume:

120

Issue:

3

Abstract:

Modular concrete elements are used for retaining walls to provide lateral support. Depending on the retaining wall layout, these precast panels may be interlocking and may be tied into the soil backfill through geosynthetic strips. This study investigates the ultimate pullout load increase, which is possible by adding varied diameter supplementary reinforcement through embedded anchor loops within concrete retaining wall panels. Previous research has investigated supplementary reinforcement around the anchor loops. This paper extends this investigation by evaluating supplementary reinforcement placed through the panel anchor loops. Full-scale panels used in practice have four embedded anchor points. However, only one anchor loop was embedded in the center of the experimental panels. The experimental panels were also cast without any bending reinforcement, as would typically be obtained in the full-scale panels. These reinforcements were purposefully excluded to evaluate the impact of a single-bar reinforcement through the center of the anchor loops. Failures that occurred were loop, panel, and a mixture thereof. Overall, the reinforced panels showed a 14 to 23% increase in the factor of safety.

DOI:

10.14359/51738462


Document: 

21-409

Date: 

September 1, 2022

Author(s):

A. S. Carey, L. A. Cooley Jr., A. Middleton, W. G. Sullivan, L. E. W. Ayers, and I. L. Howard

Publication:

Materials Journal

Volume:

119

Issue:

5

DOI:

10.14359/51735957


Document: 

18-240

Date: 

March 2, 2020

Author(s):

Barbara Klemczak and Aneta Zmij

Publication:

Structural Journal

Volume:

117

Issue:

2

Abstract:

Massive foundation slabs are one of the structures in which early age effects play a significant role. These effects are mainly related to the exothermic nature of cement hydration and a consequent temperature rise in the structure. The inhomogeneous volume changes have consequences in arising stresses in a concrete foundation slab. Two types of early-age stresses can be distinguished: self-induced stresses caused by the internal restraints, and restrained stresses resulting from the restraint existing along the contact surface of foundation slab and subsoil. This paper is focused on the distribution and the magnitude of the restrained stresses caused by the restraint between the foundation slab and soil. The results of the study have been expressed by the restraint factor R, defined as a ratio between the real stress generated in the analyzed slabs to the stress generated at full restraint of the slabs. The dependence of the external restraint factor on length/thickness ratio and thickness of the slab, type of subsoil, age of concrete, and presence of slip layers is investigated in the study. The general equations for the R factor, dependent both on length/height ratio (L/H) and thickness of the slabs, are proposed.

DOI:

10.14359/51721362


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