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International Concrete Abstracts Portal

Showing 1-5 of 142 Abstracts search results

Document: 

20-383

Date: 

July 1, 2021

Author(s):

Naseeruddin Haris and Sangeeta Gadve

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

Corrosion of reinforcing steel bars in concrete has always been one of the major causes of structural failure. This paper experimentally investigates the effect of corrosion on the mechanical properties of reinforcing bars. In the experiment, an anodic current is impressed at the specific current density to reinforcing bars of various diameters to attain different levels of corrosion. The correlation of actual mass loss with predicted mass loss, as per Faraday’s law, and the equivalent section area loss are reported. Further, the uniaxial tensile test is performed on these corroded specimens to obtain load-displacement relations. Based on the test results, stresses and strains are evaluated for all the specimens, and their responses to induced corrosion are reported. Statistical models are developed for predicting yield stress, ultimate stress, and percentage elongation in reinforcing bars that are exposed to different levels of corrosion.

DOI:

10.14359/51732795


Document: 

20-207

Date: 

May 1, 2021

Author(s):

Lihe Zhang, Dudley R. Morgan, Iain Kirk, Anastasia Rolland, and Robert Karchewski

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Wet-mix shotcrete has been used more and more for structural applications in the past few decades. Recently, wet-mix shotcrete was successfully used to construct a mass structural wall with congested reinforcement and minimum dimensions of 1.0 m in a sewage treatment plant. A low-heat shotcrete mixture that included up to 40% slag was proposed for shotcrete application. A preconstruction mockup was shot to established proper work procedures for shotcrete application and qualify the shotcrete mixture and shotcrete nozzlemen. Extraction of cores and cut windows from the mockup confirmed proper consolidation around the congested reinforcement. A thermal control plan was developed, which included laboratory and field testing requirements, thermal analysis modeling with a three-dimensional (3-D) finite element program, and thermal control requirements, including installation of cooling pipes and thermal blankets. Shotcrete proved to be an efficient means for mass concrete structural construction. Thermal control for mass shotcrete construction was studied, and the proposed thermal control plan was proved to function properly. The general guidance for mass shotcrete construction is provided.

DOI:

10.14359/51730423


Document: 

19-406

Date: 

March 1, 2021

Author(s):

Anvit Gadkar and Kolluru V. L. Subramaniam

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Self-leveling concrete is developed with low-calcium alkali-activated fly ash (AAF) binder paste. The rheological behavior of AAF pastes with different compositions is evaluated. AAF pastes are proportioned with alkali-silicate activating solutions to ensure specific reactive oxide ratios for comparable geopolymer strength. The yield stress and the viscosity of the AAF binder paste vary with the silica content and the silica modulus (SiO2/Na2O mass ratio) in the alkali-silicate activating solution. The slump and flow behaviors of concrete mixtures made with AAF paste are evaluated. The requirements of the AAF binder characteristics, paste content, and aggregate packing for achieving self-leveling flow characteristics under gravity-induced flow are assessed. The transition from a frictional to a flow-type behavior in concrete mixtures depends on the AAF binder paste content. Self-leveling is achieved without the use of admixtures with an AAF binder paste of low yield stress and at a paste content of 45%. Improving the aggregate packing using the Fuller-Thompson curve and reducing the yield stress of the AAF binder paste increase the flow achieved in concrete mixtures. The specifications for cement-based self-consolidating concrete (SCC) are closely applicable for self-leveling AAF-based concrete.

DOI:

10.14359/51729324


Document: 

19-455

Date: 

March 1, 2021

Author(s):

Mohamed M. Sadek and Assem A. A. Hassan

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

This study evaluated the abrasion resistance for a number of lightweight self-consolidating concrete (LWSCC) incorporating coarse and fine lightweight expanded slate aggregates (LC or LF, respectively). The study also investigated the abrasion resistance before and after exposure to freezing-and-thawing cycles in the presence of deicing salt. The investigated parameters included different volumes of LC and LF aggregates, three binder contents (500, 550, and 600 kg/m3 [31.2, 34.3, and 37.5 lb/ft3]), and different types of concrete (LWSCC, lightweight vibrated concrete, and normal-weight self-consolidating concrete). Increasing the percentage of expanded slate aggregate decreased the abrasion resistance. Mixtures with LF showed higher strength-per-weight ratio and higher abrasion and salt-scaling resistance compared to mixtures with LC. Samples exposed to abrasion before salt scaling had higher mass losses due to salt scaling with an average of 26.8% compared to non-abraded ones. Higher mass loss was also observed in mixtures exposed to abrasion after the exposure to salt scaling with an average of 26% and 43.3% in the rotating-cutter and sandblasting abrasion tests, respectively.

DOI:

10.14359/51729325


Document: 

19-372

Date: 

January 1, 2021

Author(s):

Guilherme S. Araujo, Lui C. Iwamoto, Rosa C. C. Lintz, and Luisa A. Gachet

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

For the production of this lightweight concrete, expanded polystyrene (EPS) associated with expanded clay sintered lightweight aggregates were used to replace nature aggregates. Materials characterization tests were performed, as well as tests of the concrete in the fresh and hardened state. It is worth noting that the fresh tests displayed that the EPS concretes produced met the requirements of ABNT NBR 15823-1: 2017, classifying them as self-compacting. The hardened concrete tests observed the compressive strength, tensile strength, water absorption, void index, and specific mass. All concretes achieved resistances above 20 MPa, considered structural, and presented low specific mass, below 2000 kg/m3, classifying them as light concrete. Scanning electron microscopy (SEM) images allowed a better understanding of the microstructure, justifying the mechanical results obtained. The transition zone between the cement paste and the light aggregates, the number of voids in the cement paste, and the appearance of microcracks were considered.

DOI:

10.14359/51728280


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