ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • 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 62 Abstracts search results

Document: 

22-164

Date: 

November 14, 2023

Author(s):

Avinaya Tripathi, Sooraj A. O. Nair, Harshitsinh Chauhan, Narayanan Neithalath

Publication:

Materials Journal

Abstract:

Conventional approaches to concrete 3D printing rely on printing concrete in a straight (linear) print path, with layers overlaid on top of each other. This results in inter-layer and inter-filament joints being potential weak spots that compromise the mechanical performance. This paper evaluates simple alterations to the print geometry to mitigate some of these effects. A printable mixture with 30% limestone powder replacing cement (by mass), with a 28-day compressive strength of about 70 MPa in the strongest direction, is used. S- and 3-shaped print paths are evaluated as alternatives to the linear print path. Staggering of the layers ensures that the inter-filament joints do not lie on the same plane along the depth. Flexural strength enhancement is observed when print geometries are changed and/or layers are staggered. The study shows that print geometry modifications mitigate mechanical property reductions attributed to inter-filament defects in concrete 3D printing.

DOI:

10.14359/51740262


Document: 

21-100

Date: 

May 1, 2023

Author(s):

Keun-Hyeok Yang, Ju-Hyun Mun, Seung-Jun Kwon, and Jong-Won Kim

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

The atmospheric purification capacity of concrete has not beenadequately investigated. This study examines the feasibility ofusing sustainable foam-concrete granules as a porous materialfor reducing air pollutants in concrete. To enable the removal of nitrogen oxide (NOx) and sulfur oxide (SOx) using titanium dioxide (TiO2) nanoparticles, foam concrete was crushed into granules with porosity exceeding 30%. Ordinary portland cement (OPC), fly ash (FA), and slag cement were used as source cementitious materials. OPC was replaced with 0 to 40% FA and 0 or 40% slag cement by weight. Test results indicate that 30% FA and unit cementitious materials content exceeding 500 kg/m3 (31.2 lb/ft3) are optimal for replacing cement and foam-concrete granules, respectively. Considering the particle-size distribution and specific surface area, 6 to 13 mm (0.24 to 0.51 in.) and 6 to 9 mm (0.24 to 0.35 in.), were selected as optimal granule sizes. The coating procedures yielded improved SOx and NOx removal, with the removal rates reaching 83.8 and 45% using granules of 6 to 9 mm (0.24 to 0.35 in.), respectively. Consequently, the foam-concrete granules coated with TiO2 nanoparticles are promising in developing porous concrete with the reduction capability of air pollutants.

DOI:

10.14359/51738507


Document: 

21-497

Date: 

November 1, 2022

Author(s):

Rita E. Lederle and Amanda Birnbaum

Publication:

Materials Journal

Volume:

119

Issue:

6

Abstract:

This study tested the effect of using taconite as an aggregate replacement in concrete. Taconite is a by-product from iron ore mining that has the potential to be used in concrete production as a coarse and/or fine aggregate. Replacing the aggregate in a concrete pavement with taconite could decrease the demand for increasingly scarce high-quality aggregates. The mechanical properties of concrete made with only fine, only coarse, or both fine and coarse taconite aggregates were tested. Properties tested include compressive, flexural, and tensile strength; elastic modulus; and coefficient of thermal expansion. All concretes made with taconite coarse and fine aggregate, either alone or in combination, produced concrete with acceptable mechanical properties for use in paving. The use of taconite coarse aggregate increased all mechanical properties tested, while the use of taconite fine aggregate had mixed effects on mechanical properties, but values of all properties tested remained within normal ranges. Fresh concrete properties were also tested, and taconite was found to decrease workability. This work shows that both coarse and fine taconite aggregates have the potential to be used as viable aggregates for concrete.

DOI:

10.14359/51736003


Document: 

21-333

Date: 

July 1, 2022

Author(s):

S. Sundar Kumar and S. Maheswaran

Publication:

Materials Journal

Volume:

119

Issue:

4

Abstract:

Geopolymer (GP) binders are an environmentally friendly alternative to ordinary portland cement (OPC). They can be produced from materials which otherwise would be considered waste and would result in environmental degradation. The objective of this study is to use industrial residues—namely, fly ash (FA), slag cement, and calcined lime sludge (CLS)—as raw materials for geopolymer binder synthesis and to investigate the thermal, microstructural, and mechanical properties of ternary blended geopolymers. This study also focused on replacing calcium-rich slag cement with CLS, a pulp and paper industry residue, the disposal of which is still a concern for the industry. Alkali activator solutions (AAS) responsible for the chemical reactions were used at two levels of concentration. Thermal analysis was carried out by using an isothermal conduction calorimeter and thermogravimetric-differential thermogravimetric analysis (TG-DTG). Microstructural characterization of raw materials and GP products were investigated by using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDAX). The results showed that the reaction characteristics of products formed and strength developed of GP mortars were as in conventional cement mortars, and also proved that CLS is a viable replacement for slag cement in geopolymer. Hence, in this novel work, slag cement and fly-ash-based geopolymers were produced by using CLS as a ternary blend partially replacing slag cement. With slag cement no longer being available free of cost, use of CLS in place of slag cement would not only reduce the cost of geopolymer but also result in a smaller carbon footprint of the product.

DOI:

10.14359/51734728


Document: 

20-398

Date: 

January 1, 2022

Author(s):

G. P. Cordoba, A. Rossetti, S. V. Zito, V. F. Rahhal, D. Falcone, and E. F. Irassar

Publication:

Materials Journal

Volume:

119

Issue:

1

Abstract:

The use of calcined clays in cement (kaolinitic and common calcined clays) introduces challenges due to the high alumina content, large specific surface area, and high-alkali content. This paper examines the performance against sulfate attacks, alkali-silica reactions, and chloride penetration in mixtures with calcined illitic shale (CIS). Replacement of high and moderate alkali content cement with 25% CIS significantly reduces the expansion in the alkali-silica reaction (ASR) test, as the pozzolanic reaction contributes to the combination of alkalis. Replacing 20% white portland cement with CIS allows the formulation of sulfate-resistant cement by limiting the formation of gypsum and ettringite. The incorporation of 25% CIS in concrete does not significantly increase chloride ingress. Therefore, blended cements with replacement levels of 20 to 25% of portland cement by CIS reduce or maintain the performance against ASR, sulfate attack, and chloride penetration.

DOI:

10.14359/51734192


12345...>>

Results Per Page