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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 38 Abstracts search results

Document: 

21-182

Date: 

March 1, 2022

Author(s):

M. Khanzadeh Moradllo, R. M. Ghantous, S. Quinn, V. Aktan, S. Reese, and W. J. Weiss

Publication:

Materials Journal

Volume:

119

Issue:

2

Abstract:

Calcium silicate cements react with carbon dioxide (CO2) to form a concrete-like product. While several papers have focused on the properties of the solid material that forms, this study investigates the processing of carbonated calcium silicate systems. Specifically, this paper examines the drying of fresh calcium silicate cement/water systems and the subsequent carbonation process. A new methodology is presented, based on neutron radiography, to quantify the drying and extent of carbonation that has occurred (degree of carbonation) and the spatial distribution of carbonated products within the sample. Mortar mixtures with high-purity calcium silicate-based cement significantly extend the initial drying period, enabling greater penetration of CO2, allowing it to react with the calcium silicate at greater depths in the sample. While the carbonation reaction is rapid immediately after the CO2 is introduced into the system, the carbonation reaction slows over time. The findings indicate that the degree of saturation and the potential formation of reaction products may limit the penetration of CO2 through the sample depth.

DOI:

10.14359/51734401


Document: 

21-062

Date: 

January 1, 2022

Author(s):

Guillermo Hernández-Carrillo, Alejandro Durán-Herrera, and Arezki Tagnit-Hamou

Publication:

Materials Journal

Volume:

119

Issue:

1

Abstract:

Ultra-high-performance concrete is a milestone of both durability and mechanical performance; nevertheless, its high consumption of clinker generates a large carbon footprint, and a large quantity of this clinker remains anhydrous due to the very low water availability in the compound. Studies of back-scattered electrons, X-ray diffraction, and quantitative energy-dispersive spectroscopy were done to propose that the cement replacement by inert fillers having a hardness between the limestone and quartz powder is possible due to a higher dissolution of both cement and silica fume that allows the formation of lower Ca/Si ratio C-S-H if enough silica fume is present to keep porosity next to the aggregate constant. Finally, the replaced mixtures had a 37% lower carbon footprint than the reference. The results showed no difference between quartz and limestone systems—both with an adequate silica fume dosage, where able—to keep both compressive strength and bulk resistivity performance at a 37.5% cement replacement.

DOI:

10.14359/51734222


Document: 

20-469

Date: 

November 1, 2021

Author(s):

Viacheslav Markin, Christof Schröfl, Paul Blankenstein, and Viktor Mechtcherine

Publication:

Materials Journal

Volume:

118

Issue:

6

Abstract:

The applicability of wood-based, starch-bonded composite materials for three-dimensional (3D)-printed temporal, fully recyclable support structures was studied experimentally with respect to delivering the specific geometric and load-bearing features of the product of a continuous 3D concrete printing process. Extrudability of the support material developed was verified by direct test using a conventional screw extruder. The observations and quantitative results were compared with those gained with a ram extruder. The development of the compressive strength of the support materials was analyzed experimentally from an early age, beginning a few minutes after extrusion. The results obtained confirmed the sufficiency of the product’s strength in withstanding prospective weight loads of concrete layers printed on top of the support. Furthermore, methods of enhancing early-age compressive strength were analyzed, and a most promising approach was experimentally implemented—namely, the deposition of the material under a constant defined airflow. In contrast to its promising mechanical material characteristics, massive fungi formation was observed as early as 1 day, amounting to a severe drawback. Consequently, improvements to the material’s composition are suggested that will not impair the environmental sustainability of the support material.

DOI:

10.14359/51733131


Document: 

20-467

Date: 

November 1, 2021

Author(s):

Jason Straka, Stephen P. Klaus, Junfeng Zhu, Pete A. Gentile, and Nathan A. Tregger

Publication:

Materials Journal

Volume:

118

Issue:

6

Abstract:

Tens of millions of cubic meters of concrete have now been delivered through in-transit measurement systems across the world. These sensor and control systems exist as true IoT (Internet of Things) systems, providing millions of data points describing the impact that process and materials changes have on concrete delivery and performance. Through advanced analytics, many insights can be garnered, leading to improvements in both concrete quality and the economic and environmental impact of concrete production. This paper discusses the current and future consequences of having an in-transit measurement system, including slump management, increased admixture efficiencies, and reduced environmental impact.

DOI:

10.14359/51733130


Document: 

20-446

Date: 

November 1, 2021

Author(s):

L. S. C. Ko, S. Moro, J. Bury, T. Vickers, B. Sachsenhauser, and S. Mönnig

Publication:

Materials Journal

Volume:

118

Issue:

6

Abstract:

To ensure a successful outcome when using cementitious materials during three-dimensional (3D) printing operations, the effects of chemical admixtures on rheological and setting behavior must be carefully adjusted to accommodate the needs for pumping, extrusion, deposition, and self-sustainability without the support of formwork. This paper highlights potential solutions offered by chemical admixtures, while discussing various testing methods and important influencing parameters. The impact of commercial polymers on viscosity, initial yield stress, thixotropy, and their variations over time are reported. Influencing factors, such as mixing energy and material interactions, are discussed. Accelerating and strength-enhancing admixtures are used to illustrate the adjustment of setting and early strength development of concrete. Understanding the possibilities of modifying fresh concrete properties will help to improve the robotic construction process as well as the design or adaptation of the printing equipment.

DOI:

10.14359/51733121


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