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International Concrete Abstracts Portal

Showing 1-5 of 525 Abstracts search results

Document: 

23-096

Date: 

March 15, 2024

Author(s):

Zoi G. Ralli and Stavroula J. Pantazopoulou

Publication:

Materials Journal

Abstract:

In light of the effort for decarbonization of the energy sector, it is believed that common geopolymer binding materials such as fly ash may eventually become scarce, and new geological aluminosilicate materials should be explored as alternative binders in geopolymer concrete. A novel, tension-hardening geopolymer concrete (THGC) that incorporates high amounts of semi-reactive quarry wastes (Metagabbro) as a precursor and coarse quarry sand (granite) was developed in this study using geopolymer formulations. The material was optimized based on the particle packing theory and was characterized in terms of mechanical, physical, and durability properties (i.e., compressive, tensile, flexural resistance, Young’s Modulus, Poisson’s ratio; absorption, drying shrinkage, abrasion, and coefficient of thermal expansion; chloride ion penetration, sulfate, and salt-scaling resistance). The developed THGC with an air-dry density of 1,940 kg/m3 [121 lb/ft3], incorporates short steel fibers at a volume ratio of 2% and is highly ductile in both uniaxial tension and compression (uniaxial tensile strain capacity of 0.6% at an 80% post-peak residual tensile strength). Using DIC, multiple crack formation was observed in the strain-hardening phase of the tension response. In compression the material maintained its integrity beyond the peak load, having attained 1.8% compressive strain at 80% post-peak residual strength whereas upon further reduction to 50% residual strength, the sustained axial and lateral strains were 2.5% and 3.5%, respectively. The material exhibited low permeability to chloride ions and significant abrasion resistance due to the high contents of Metagabbro powder and granite sand. The enhanced properties of the material, combined with the complete elimination of ordinary Portland cement from the mix, hold promise for the development of sustainable and resilient structural materials with low CO2j, emissions while also enabling the innovative disposal of wastes as active binding components.

DOI:

10.14359/51740704


Document: 

23-191

Date: 

February 8, 2024

Author(s):

Pouria Mohsenzadeh Tochahi, Gholamreza Asadollahfardi, Seyed Fazlullah Saghravani, Niloofar Mohammadzadeh

Publication:

Materials Journal

Abstract:

In marine structures, concrete requires adequate resistance against chloride ion penetration. As a result, numerous studies have been conducted to enhance the mechanical properties and durability of concrete by incorporating various pozzolans. This research has investigated the curing conditions of samples including zeolite and metakaolite mixed with Micro nanobubble water in artificial seawater and standard conditions. The results indicated that incorporating zeolite and metakaolin mixed with Micro nanobubble water, which was cured in artificial seawater conditions, compared to similar samples that were cured in standard conditions, improved the mechanical properties and durability of concrete samples. The compressive strength of 28 days concrete samples containing 10% metakaolin mixed with 100% Micro nanobubble water and samples consisting of 10% zeolite blended with 100% Micro nanobubble water cured in seawater in comparison to the control sample cured in the standard condition indicated an increase of 25.06% and 20.9%, respectively. The most results were obtained with a compound of 10% metakaolin, and 10% zeolite with 100% Micro nanobubble cured in seawater (MK10Z10NB100CS) which rose significantly Compressive, Tensile and Flexural Strength by 11.13, 14, and 9.1%, respectively, in comparison with to the MK10Z10NB100 sample cured in the standard condition. Furthermore, it decreased considerably 24-hr water absorption and Chloride Penetration at 90 days by 27.70 and 82.89%, respectively, in comparison with the control sample cured in standard conditions.

DOI:

10.14359/51740567


Document: 

21-335

Date: 

January 4, 2024

Author(s):

Zainab Hashim Abbas Alsalami, Fatima Hashim Abbas,

Publication:

Materials Journal

Abstract:

Ultra-high-performance concrete (UHPC) is considered a sophisticated concrete construction solution for infrastructure and other structures because of its premium mechanical traits and superior durability. Fibers played a special effect on the properties of UHPC, especially this type of concrete suffered from high autogenous shrinkages due to high cementitious content, so the properties and volume fraction of fibers are more important in UHPC. This study will describe the previous related works on the mechanical behavior of UHPC specimens reinforced with micro and Nano scale fibers, comparison of the behavior of UHPC reinforced with microfibers and that reinforced with Nanofibers. Compressive strength, flexural behavior, and durability aspects of UHPC reinforced with nano and/or micro scale of variable types of fibers were studied to highlight the issues and make a new direction for other authors.

DOI:

10.14359/51740369


Document: 

22-287

Date: 

January 1, 2024

Author(s):

Igor Lapiro, Rami Eid, and Konstantin Kovler

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

The penetration of chloride ions causes degradation of reinforcing bars, which directly affects the service life of the element. In this study, four different alternatives for the construction of a reinforced concrete (RC) caisson parapet beam are investigated: conventional RC, the addition of a corrosion inhibitor to concrete, and the use of glass fiber-reinforced bars (GFRP) and galvanized steel instead of steel bars. The durability of the RC element under marine environment was studied based on measurements performed both in-place and in well-controlled laboratory conditions on specimens prepared in the laboratory, as well as specimens taken from the actual structural element. It was concluded that the exposure of fresh concrete to seawater splash has no effect on mechanical properties. In addition, galvanized rods were found to be a less effective protection strategy compared to the other alternatives studied. GFRP bars, however, provide better protection than the other tested alternatives, although chloride ion penetration in these bars was found to be more accelerated in an alkaline environment compared to a chloride environment. In contrast to the prevailing approach, which considers plain concrete and according to which the electrical resistance of the concrete decreases because of chloride penetration, this study found that electrical resistance in the reinforced element is increased due to an increase in the amount of corrosion products formed between steel and concrete if no cracks occur. Furthermore, it was found that the potential measured using the half-cell method in all the alternatives slowly increased with time, as well as the corrosion risk in the three alternatives with reinforcing steel. The remaining question is whether this change of potential is a direct characteristic of the corrosion risk. Therefore, more research in this direction is needed.

DOI:

10.14359/51740260


Document: 

22-260

Date: 

January 1, 2024

Author(s):

Amit Kumar, Gyani Jail Singh, Priyanshu Raj, and Rajesh Kumar

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

This research examines the performance of quality-controlled recycled concrete aggregates (QRAs) with fly-ash-based cement. Compared to concrete made from untreated recycled concrete aggregates (URC), quality-controlled recycled aggregate concrete (QRC) has superior physical, mechanical, and durability properties. Except for sorptivity, the physical, mechanical, and durability properties of QRC are almost identical to those of natural aggregate concrete (NC). The compressive strength, splitting tensile strength, flexural strength, fracture energy, and modulus of elasticity of QRC are higher than those of URC by 18.0%, 16.8%, 60.0%, 27.17%, and 43.46%, respectively. The abrasion resistance of QRC is approximately 60% higher than URC. Scanning electron microscope (SEM) image and energy-dispersive X-ray (EDX) analysis prove that quality control produces denser old interfacial transition zones (OITZ) with fewer microvoids. The QRA improves not only the pore structure but also the weak mortar structure attached to the aggregate. There is also a strong correlation between the compressive strength and splitting tensile strength, flexural strength, fracture energy, and modulus of elasticity of QRC. QRA can be used to compute the mixture proportions for concrete (certainly up to medium-strength concrete) according to either the Indian standard or the international standard. It is challenging to improve the sorptivity of recycled concrete aggregates closer to NC. In addition, QRC has an initial sorptivity of two times (initial) and a final sorptivity of 1.8 times higher than NC, whereas URC has an initial sorptivity of 3.5 times (initial) and a final sorptivity of 2.35 times higher than NC.

DOI:

10.14359/51740259


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