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International Concrete Abstracts Portal

Showing 1-5 of 397 Abstracts search results

Document: 

23-010

Date: 

January 1, 2024

Author(s):

Sahith Gali and Sri Sritharan

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

Ultra-high-performance concrete (UHPC) is a cementitious concrete material known for its sustained post-cracking tensile performance. Various specimen geometries and different test approaches have been used to establish the tensile characteristics of UHPC. Intending to standardize a direct tension test method, this paper independently evaluates a procedure developed by the Federal Highway Administration (FHWA), which has been adopted into AASHTO T 397. To verify the reliability and repeatability of the test method, 216 tensile specimens were cast from three different UHPC types with fiber-volume fractions of 1, 2, and 3% and tested at six laboratories. The measured responses were characterized for different phases of the tensile behavior and analyzed to understand the scatter in the test data. It was found that testing can be executed with a 60 to 70% success rate with carefully prepared samples and some modifications to the proposed test method. The test results show an increase in both the tensile strength and multicracking phase with an increase in fiber-volume fraction, but the crack straining phase depends primarily on the type of UHPC. Using the test data, average and characteristic tensile responses were established, which are intended, respectively, for analysis and design purposes.

DOI:

10.14359/51739204


Document: 

22-073

Date: 

December 1, 2023

Author(s):

Zhenwen Xu and Dongming Yan

Publication:

Materials Journal

Volume:

120

Issue:

6

Abstract:

External bonding with fiber-reinforced polymer (FRP) offers a potential solution to mitigate the detrimental effects caused by load impact and corrosion, which can weaken the bond strength of reinforced concrete structures. However, existing models need to be improved in addressing the FRP confinement mechanism and failure modes. As a solution, the proposed model employs stress intensity factor (SIF)-based criteria to determine the internal pressure exerted on the steel-concrete interface during various stages of comprehensive concrete cracking. Critical parameters are evaluated using weight function theory and a finite element model. A bond-slip model is introduced for the FRP-concrete interface and reasonable assumptions on failure plane characteristics. The internal pressure model employed demonstrates that FRP confinement has the ability to generate dual peaks in stress distribution and modify their magnitude as the confinement level increases. The proposed predictive model demonstrates superior performance in failure modes, test methods, and wrap methods for assessing bond strength with FRP confinement. The accuracy of this model is indicated by an integral absolute error (IAE) of 9.6% based on 125 experimental data, surpassing the performance of the other three existing models. Moreover, a new confinement parameter is introduced and validated, showing an upper bound of 0.44 for enhancing FRP bond strength. Additionally, a general expression validating the bond strength model with FRP confinement is established, allowing for the prediction of bond length.

DOI:

10.14359/51739144


Document: 

21-483

Date: 

September 1, 2023

Author(s):

Nima Mohammadian Tabrizi, Davood Mostofinejad, and Mohammad Reza Eftekhar

Publication:

Materials Journal

Volume:

120

Issue:

5

Abstract:

This paper is aimed at investigating the effects of different fiber inclusion on the mechanical properties of ultra-high-performance concrete (UHPC) by adding mineral admixtures as cement replacement materials to reduce production costs and CO2 emissions of UHPC. Throughout this research, 21 mixture designs containing four cement substitution materials (silica fume, slag cement, limestone powder, and quartz powder) and three fibers (steel, synthetic macrofibers, and polypropylene) under wet and combined (autoclave, oven, and water) curing were developed. To investigate the mechanical properties in this research, a total of 336 specimens were cast to evaluate compressive strength, the modulus of rupture (MOR), and the toughness index. The findings revealed that at the combined curing, regarded as a new procedure, all levels of cement replacement recorded a compressive strength higher than 150 MPa (21.76 ksi). Furthermore, the mechanical properties of the mixture design containing microsilica and slag (up to 15%) were found to be higher than other cement substitutes. Also, it was shown that all levels of the fiber presented the MOR significantly close together, and samples made of synthetic macrofibers and steel fibers exhibited deflection-hardening behavior after cracking. The mixture design containing microsilica, slag, limestone powder, and quartzpowder, despite the significant replacement of cement (approximately 50%) by substitution materials, experienced a slight drop in strength. Therefore, the development of this mixture is optimal both economically and environmentally.

DOI:

10.14359/51738888


Document: 

22-226

Date: 

May 1, 2023

Author(s):

Savitha Sagari Srinivasan and Raissa Douglas Ferron

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

Most concrete service life models are designed for uncrackedconditions, and the effect of microcracks on such models has not been as well researched. A service life model for concrete structures that takes into account microcracking is presented. A unique feature of this model is that its input parameters can be determined using only nondestructive methods, thus allowing it to be used when samples for laboratory tests cannot be extracted— for example, in in-service or critical infrastructure. The model was developed for low water-cementitious materials ratio (w/cm) concrete mixtures and validated on full-scale prestressed concrete girders. The results showed that the presence of a large number of microcracks could cause a loss in the remaining service life of concrete structures, even if individual microcracks did not cause asignificant impact.

DOI:

10.14359/51738686


Document: 

22-143

Date: 

March 1, 2023

Author(s):

Rodolfo Bonetti, Oguzhan Bayrak, Kevin Folliard, and Thanos Drimalas

Publication:

Materials Journal

Volume:

120

Issue:

2

Abstract:

This paper presents a set of procedures and a recently developed direct tension test for determining the uniaxial tensile strength and full stress-strain behavior of ultra-high-performance concrete (UHPC). The proposed set of procedures aim to establish an upper and lower bound for the tensile strength based on preferential casting orientation. Results from this research show that an upper and lower bound of strength could be established when properly executed casting procedures are in place. On the other hand, the proposed direct tension test can capture the full stressstrain behavior of the material at pre- and post-cracking stages, for both strain-hardening and strain-softening samples. Results from the direct tension tests performed during this research favor the use of contactless extensometers to avoid stress concentrations that induce early localization at the regions close to the attachment points when using traditional measuring methods.

DOI:

10.14359/51738374


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