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International Concrete Abstracts Portal

Showing 1-5 of 61 Abstracts search results

Document: 

22-379

Date: 

March 15, 2024

Author(s):

Joseph Jean Assaad and Marianne Saba

Publication:

Materials Journal

Abstract:

This paper assesses the suitability of geopolymers (GPs) for use as adhesives for ceramic tile fixing, including their compliance to relevant EN 12004 specifications. Two series prepared with different percentages of metakaolin (MK), blast furnace slag (BFS), and limestone materials activated by an alkaline NaOH/Na2SiO3 solution are investigated. Tested properties included the thixotropy, setting, compressive strength, open time, and adhesion bond strength under different exposure conditions (i.e., dry, wet, heat, or freeze/thaw cycles). Compared to cement-based mortars containing adjusted proportions of cellulose and redispersible polymers, the GPs exhibited higher thixotropy reflecting additional energy for spreading the material over the substrate, yet better maintaining of the alternating patterns of ripples and grooves at rest. The bond strengths tested under different exposure conditions were remarkably high for the MK-based GP, given the fine MK particle sizes that foster geopolymerization and cross-linking of solid bonds in the hardened structure. The BFS-based GP exhibited relatively lower bond strengths (compared to MK) due to coarser particles. Such results can be of interest to civil engineers and manufacturers of ready-to-use building materials that aim at reducing the Portland cement footprint while assuring the performance and sustainability of tiling applications.

DOI:

10.14359/51740702


Document: 

22-054

Date: 

May 1, 2023

Author(s):

Gokul Dev Vasudevan and David Trejo

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

Fly ashes that do not meet the ASTM C618 specifications areconsidered “off-spec” and are not used as supplementary cementitious materials (SCMs). In this research, four off-spec fly ashes (OFAs) were sourced from different parts of the United States and the characteristics of these OFA concretes were measured to compare their performance with that of the mixtures containing 0% OFA. The first objective of this study is to assess the influence of OFA reactivity and replacement levels on concrete characteristics. The second objective is to assess the influence of constituent material characteristics such as shape and size of coarse aggregate, fineness modulus of fine aggregate, and cementitious content of the concrete mixture on the fresh and hardened characteristics of concretes containing OFAs. Results indicate that at sufficient degrees of reactivity and replacement levels, OFAs can provide characteristics comparable to that of conventional ordinary portlandcement (OPC) concrete while improving the consistency of theconcrete. Findings from sensitivity analysis reveal that the degree of reactivity (DoR) of the OFA has a high influence on the hardened characteristics of concrete. Finally, the life cycle assessment of concrete mixtures containing OFAs indicate that greenhouse gas emissions can be reduced up to 45% when compared to conventional mixtures.

DOI:

10.14359/51738707


Document: 

21-461

Date: 

January 1, 2023

Author(s):

Francesca Lolli, Renee T. Rios, Katelynn Schoenrock, Emily Grubert, and Kimberly E. Kurtis

Publication:

Materials Journal

Volume:

120

Issue:

1

Abstract:

The use of performance-based specifications (PBS) may increase quality and sustainability while lowering project costs through innovations in concrete materials selection and proportioning. A preliminary survey was conducted showing that barriers to implementation for PBS still exist, the main barrier being the enforcement of the specification, followed by cost and time. This study aims to develop guidelines to overcome the identified barriers by presenting a laboratory-scale case study of six concrete mixtures that both conform (one) and do not conform (five) to Georgia Department of Transportation specifications. This case study includes experimental results of mechanical (flexural and compressive strength) and resistivity performance properties, as well as three additional parameters: time, cost, and carbon dioxide (CO2) emissions associated with each mixture design. This study showed that innovation in material use and mixture design can increase durability and performance while reducing the overall project cost and environmental impact.

DOI:

10.14359/51738457


Document: 

21-495

Date: 

September 1, 2022

Author(s):

L. Bouchelil, R. M. Ghantous, G. Clark, M. N. Goodwin, W. J. Weiss, and M. Khanzadeh Moradllo

Publication:

Materials Journal

Volume:

119

Issue:

5

Abstract:

Relatively limited work has been performed to quantify how internal curing influences curing specifications. This paper examines the performance of internally cured mixtures (made using fine lightweight aggregates) compared to conventional concrete cured with wet burlap and curing compounds. Mortar mixtures were prepared using ordinary portland cement (OPC), fly ash, and silica fume (SF) with water-cementitious materials ratios (w/c) of 0.35 and 0.45. Neutron radiography (NR) was used to determine the nonevaporable water content as a function of curing time and distance from the exposed surface. The curing-affected zone (CAZ) was determined using the nonevaporable water profiles. The CAZ was used to develop equivalent curing durations for conventionally cured and internally cured samples. Internally cured mixtures reduced the depth of the CAZ, especially in the samples with limited external curing durations (reduction up to 15 mm [0.6 in.]). The application of internal curing in all mixtures reduced the duration of external curing by 50 to 60%, except for the internally cured SF samples, which showed a slight reduction. This dramatically impacts the construction schedule.

DOI:

10.14359/51735980


Document: 

20-435

Date: 

March 1, 2022

Author(s):

K. S. T. Chopperla, S. Smith, T. Drimalas, N. P. Vaddey, A. Bentivegna, K. E. Kurtis, M. D. A. Thomas, and J. H. Ideker

Publication:

Materials Journal

Volume:

119

Issue:

2

Abstract:

The American Concrete Institute (ACI) provides guides, specifications, and code documents related to concrete durability. The authors reviewed two code documents from ACI Committees 318 and 350, two guidance documents from ACI Committees 201 and 222, and a specification document from ACI Committee 350, and observed that several discrepancies exist in terms of providing uniform durability requirements for freezing and thawing and chemical sulfate attack of concrete, and allowable chloride limits for new construction. By analyzing existing concrete durability data from published literature, laboratory testing, and field exposure sites, recommendations on unified durability requirements and exposure class descriptions are made for potential adoption by ACI Committees 201, 222, 318, and 350.

DOI:

10.14359/51734352


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