Compaction self-assembly of a low-binder-content geopolymer material
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Compaction self-assembly of a low-binder-content geopolymer material Kiwon Oh1, Haozhe Yi2, Rui Kou2, and Yu Qiao1,2,* 1 2
Program of Materials Science and Engineering, University of California – San Diego, La Jolla, CA 92093, USA Department of Structural Engineering, University of California – San Diego, La Jolla, CA 92093-0085, USA
Received: 21 May 2020
ABSTRACT
Accepted: 9 July 2020
In order to reduce the use of class F fly ash in geopolymer parts, we investigated the compaction self-assembly (CSA) technology, which could greatly decrease the fly ash content from * 25 to * 10 wt%. In CSA, a compaction pressure was applied on the premixed material, to efficiently distribute the small amount of binder to the most critical microstructural sites. When the compaction pressure was 70 MPa, the flexural strength reached * 4 MPa, comparable with typical unreinforced concrete; when the compaction pressure was 200 MPa, the flexural strength was * 10 MPa, comparable with typical steel-reinforced concrete. The material strength increased with the binder content and was quite insensitive to the water glass to sodium hydroxide solution ratio.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05069-5
J Mater Sci
GRAPHIC ABSTRACT
Introduction The compaction self-assembly (CSA) technology was recently developed to produce ultralow-binder-content (UBC) composites [1, 2]. CSA begins with premixing a small amount of binder, such as epoxy, into a filler, such as sand. The binder amount can be as low as * 4 wt%; the rest * 96 wt% is the filler. Then, a compaction pressure, typically 50–200 MPa, is applied. The high pressure densifies the filler, squeezes the binder droplets, and more importantly, causes a high capillary pressure at the narrow space where filler grains are in contact with each other. The capillary pressure drives the binder to the most critical microstructural locations, so that the binder is efficiently utilized to carry load. Thus, the CSA-processed UBC composites can be stronger than typical steelreinforced concrete. Because of the drastically reduced binder usage, the materials cost is lowered, and the carbon emission associated with the production and transportation of the binder is minimized. The previous study on CSA was focused on organic polymer binders, such as epoxy and unsaturated polyester resin. Organic polymers are workable, strong, tacky, ductile, and quite durable [3, 4]. However, they are relatively expensive [5], and have a certain limitation for high-temperature or high-
moisture applications [6]. Their pot lives are usually only a few hours [7]. For construction materials, an emerging green binder is geopolymer [8–10]. Geopolymer is viewed as an alternative to ordinary portland cement (OPC). Compared to OPC, production of geopolymer emits less carbon dioxide. Geopolymer tends to have a high early strength, a high workability, an excellent chemical resistance, and an adequate fire re
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