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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 416 Abstracts search results

Document: 

21-482

Date: 

November 2, 2022

Author(s):

Stephen O. Ekolu

Publication:

Materials Journal

Abstract:

Major cities worldwide are densely built with concrete structures. Moreover, urban infrastructures partly cause and are in return adversely impacted by the Urban Heat Island (UHI) effect that elevates localized temperature, further to the rise caused by the climate-change-induced (CCI) impact of CO2 emissions. While the influence of temperature on carbonation is generally well–established based on experimental research, there are hardly any analytical engineering methods for evaluating temperature effect on natural carbonation specifically. In the present study, an equation referred to as the temperature correction factor (TCF) submodel, capable of accounting for temperature effect on natural carbonation, was nested into the natural carbonation prediction (NCP) model, then used to conduct the evaluation.

The second aspect of the present study was the employment of the TCF submodel for the evaluation of CCI temperature rise on natural carbonation. The scope of evaluation covered 130 selected major cities, geographically located globally and strategically representative of the diverse climate regions worldwide. It was found that the tropical climate regions exhibit a more significant increase in CCI carbonation progression, compared to that of the temperate regions. For structural concretes of normal to moderate strengths, CCI carbonation increases by up to 34 to 46% in tropical regions and by as low as 9.43 /0% in cold /sub-polar temperate regions. The silver-bullet solution to CCI's adverse effects is the use of high-strength concretes, which is a conundrum as this measure undermines or negates sustainability principles. Evidently, the projected CCI global temperature rise significantly increases concrete carbonation in major climate zones. Research is needed into the development of countermeasures and design provisions for the climate resilience of concrete structures.

DOI:

10.14359/51737335


Document: 

22-057

Date: 

November 2, 2022

Author(s):

Niranjan Prabhu Kannikachalam, Davide di Summa, Ruben P. Borg, Estefania Cuenca, Matteo Parpanesi, Nele De Belie. and Liberato Ferrara

Publication:

Materials Journal

Abstract:

This research focuses on the evaluation of the sustainability of recycled ultra-high-performance concrete (R-UHPC), from a life cycle analysis perspective and with reference to a case study example dealing with structures exposed to extremely aggressive environments. This involves the assessment of the self-healing capacity of R-UHPC, as guaranteed by the recycled UHPC aggregates themselves. Recycled aggregates (RA) were created by crushing four-month-old UHPC specimens with an average compressive strength of 150 MPa. Different fractions of recycled aggregates (0 to 2 mm) and two different percentages (50 and 100%) were used as a substitute for natural aggregates in the production of R-UHPC. Notched beam specimens were pre-cracked to 150 µm using a three-point flexural test. The autogenous self-healing potential of R-UHPC, stimulated also by the addition of a crystalline admixture, was explored using water absorption tests and microscopic crack healing at a pre-determined time (0 days, 1 month, 3 months, and 6 months) following pre-cracking. Continuous wet/dry healing conditions were maintained throughout the experimental campaign. The specimens using recycled UHPC aggregates demonstrated improved self-healing properties to those containing natural aggregates, especially from the 2nd month to the 6th month. To address the potential environmental benefits of this novel material in comparison to the conventional ones, a Life Cycle Assessment (LCA) analysis was conducted adopting the 10 CML-IA baseline impact categories, together with a Life Cycle Cost (LCC) analysis to determine the related economic viability. Both LCA and LCC methodologies are here integrated into a holistic design approach to address not only the sustainability concerns but also to promote the spread of innovative solutions for the concrete construction industry. As a case study unit, a basin for the collection and cooling of geothermal waters has been selected. This is meant as representative of both the possibility offered, in terms of structural design optimization and reduction of resource consumption, and of reduced maintenance guaranteed by the retained mechanical performance and durability realized by the self-healing capacity of the R-UHPC.

DOI:

10.14359/51737336


Document: 

21-470

Date: 

November 2, 2022

Author(s):

Julie K. Buffenbarger, James M. Casilio, Hessam AzariJafari, and Stephen S. Szoke

Publication:

Materials Journal

Abstract:

The overdesign of concrete mixtures and substandard concrete acceptance testing practices significantly impact the concrete industry's role in sustainable construction. This study evaluates the impact of overdesign on the sustainability of concrete and embodied carbon emissions at the national and project scales. In addition, this paper reviews quality results from a concrete producer survey; established industry standards and their role in acceptance testing in the building codes; the reliance on proper acceptance testing by the Licensed Design Professional, Building Code Official, and the project owner; and the carbon footprints that result from overdesign of concrete mixtures. In 2020, a field survey conducted on over 100 projects documented Pennsylvania's quality of field testing. Of those surveyed, only 15% percent of the projects met the testing criteria within the ASTM and building code requirements. As a result, the total overdesign-induced cement consumption is as large as 6.7% of the U.S. estimated cement used in the U.S.

DOI:

10.14359/51737334


Document: 

22-116

Date: 

October 18, 2022

Author(s):

S.H. Chu

Publication:

Materials Journal

Abstract:

Concrete mixture design is the foundation of cement and concrete research. Innovations in concrete materials could, should, and would inevitably be incorporated into new mixture designs. Thus, a rigorous method for concrete mixture design can better bridge the research community and the construction industry with high reliability and high fidelity. However, current methods for concrete mixture design vary a lot in literature, thus compromising the accuracy and consistency in interpreting the properties of concrete subject to changes in its raw ingredients. Moreover, the extraneous variables in controlled experiments are not always controlled well. To solve this old but critical problem, this paper summarizes the prevalent concrete mixture design methods in literature and in practice. By contrast, the volume-based mixture design method is superior to the mass ratio-based mixture design method in terms of simplicity, accuracy, and consistency. Further discussion on packing density measurement and water or slurry film thickness (SFT) as a basis of volume-based mixture design is elaborated. Mathematically, the hardened properties were linked to the particle packing behavior and fresh properties of concrete. This research contributes to a unified volume-based design method to bridge the research community and the construction industry. In the end, it is conducive to upgrading from concrete technology to concrete science.

DOI:

10.14359/51737295


Document: 

21-493

Date: 

October 18, 2022

Author(s):

M. Selvam and Surender Singh

Publication:

Materials Journal

Abstract:

Lack of understanding of the compaction mechanism, both in the laboratory and field, could result in significant under/overestimation of the RCCP performance. The literature (1987-2022) depicts that there are numerous techniques to design the RCCP in the laboratory; however, which method could closely simulate the field compaction is not fully explored. The present paper critically reviews the fundamental parameters affecting the strength characteristics of RCCP when compacted with different compaction mechanisms in the laboratory and attempts to rank the compaction methods based on the field performance. Also, recommendations have been made on how to fabricate the specimens without having much impact on the considered compaction technique. The techniques that have been considered are the vibratory hammer, vibratory table, modified Proctor, gyratory compactor, and special compactors such as the California kneading compactor, Marshall hammer, and duplex rollers. Based on the present review, future research prospects are outlined to improve the performance of RCCP.

DOI:

10.14359/51737290


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