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International Concrete Abstracts Portal

Showing 1-5 of 46 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: 

21-458

Date: 

November 2, 2022

Author(s):

Duo Zhang and Victor C. Li

Publication:

Materials Journal

Abstract:

The built environment is facing an increasing challenge of emission reduction regarding both embodied and operational carbon. As an ultra-durable concrete, engineered cementitious composites (ECC) reduce the need for repair, thus resulting in a prominent reduction of lifecycle footprints. Here, a new version of low-carbon ECC was developed for cast-in-place applications by sequestering CO2 via mineralization. Two waste streams were pre-carbonated and incorporated into ECC as fine aggregate and supplementary cementitious material, respectively. At 28 d, the CO2-sequestered ECC exhibited a compressive strength of 32.2 MPa (4670 psi), a tensile strength of 3.5 MPa (508 psi), and a strain capacity of 2.9%. Multiple fine cracks were distinctly identified, with a residual crack width of 38 µm (0.0015 in.) and a self-healing behavior comparable to that of conventional ECC. The new ECC sequestered 97.7 kg/m3 (164.7 lb/yd3) CO2 (equivalent to 4.7 wt% of final mixture) and demonstrated a 42% reduction in cradle-to-gate emissions compared to conventional concrete at the same strength level. This study demonstrates the viability of turning waste CO2 gas into durable construction materials and proposes a potential path toward carbon neutrality.

DOI:

10.14359/51737331


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: 

22-057

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: 

21-466

Date: 

November 2, 2022

Author(s):

Xiaoguang Chen, Zeger Sierens, Elke Gruyaert, and Jiabin Li

Publication:

Materials Journal

Abstract:

Mixed recycled aggregate (MRA) is considered a sustainable construction material, and its use in precast concrete is currently banned due to its poor engineering performance. This paper aims to evaluate the feasibility of partial replacement of natural coarse aggregate with MRA in self-compacting concrete (SCC) for manufacturing architectural precast concrete sandwich wall panels. To this end, five MRAs from recycling plants were characterized, out of which two were selected to develop SCC. SCC mixtures with three replacement levels and three water compensation degrees were produced, and their physical, mechanical, durability and aesthetic properties were examined. The results showed that the incorporation of MRA dominated the mechanical properties of SCC, while the water compensation degree primarily affected the flowability and carbonation resistance. The presence of MRA had no considerable effect on the aesthetic characteristics. Up to 10% MRA in weight of total aggregates could be used in precast SCC.

DOI:

10.14359/51737333


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