Carlos Montes

Optimization of Geopolymer Properties by Coating of Fly-Ash Microparticles with Nanoclays

Geopolymer binders are aluminosilicate inorganic polymers with expanding applications as construction materials. For wider industrial use of these binders, limited controls of their rheological properties and short solidification time have to be improved. A surface modification of fly ash microcores allows for better control of the geo-concrete formation. Naturally occurring nanoclays, such as halloysite nanotubes and kaolin nanoplates are cheap and abundantly available materials allowing encapsulating alumosilicate microcores with simple and scalable layer-by-layer (LbL) nanocoating technique. An electrostatic attraction drives coating of anionic nanoclays onto fly ash particles providing a potential to controllably adjust properties of geopolymer composites. LbL technique was used to modify geopolymer through nanoarchitectural formation of composite shells on ash microcores. We describe mechanical and rheological enhancement of geopolymers produced from ash microparticles coated with tubule or platy nanoclays sandwiched with polycations, and its advantages for better concrete materials.

Rheological behavior of fly ash-based geopolymers with the addition of superplasticizers

Geopolymers are novel cementitious binders that are finding new industrial applications every day. One of the most important aspects for the commercialization of these products is their behavior in plastic state. The workability of fresh geopolymer paste can be measured with several common tests used for Portland cement concrete, like flow and slump; however, a more in-depth characterization of their rheology is essential to understand its basic setting mechanisms. In this article, the rheological behavior of geopolymer paste prepared under different mix design formulations is studied. Special consideration is given to the rheological behavior of geopolymer paste under the action of a superplasticizer. The effect of the superplasticizers on the viscosity of fresh geopolymers was evaluated and recommendations about the use of these additives are provided.

Influence of Activator Solution Formulation on Fresh and Hardened Properties of Low-Calcium Fly Ash Geopolymer Concrete

The effect of the composition of activator solutions on fresh and hardened properties of geopolymer concrete was investigated. Research variables included liquid sodium silicate product (DH, NH, and StarH), sodium hydroxide molar concentration (6, 10, and 14), and sodium silicate–to–sodium hydroxide ratio (1, 2, and 3). Response variables were compressive strength, corrosion resistance expressed as remaining compressive strength and mass loss, and flowability. Results were analyzed using Minitab statistical software. Findings suggest that activator solution formulation has a significant effect on the properties of the resulting geopolymer binder. The experimental design used was found effective in establishing the optimum activator solution formulation for a given fly ash stockpile to be used for an application with specific performance requirements. f 2012 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 20 September 2011; Received in revised form 6 January 2012; Accepted 9 January 2012

Study of the Interaction Between Nanoclay and Fly Ash and Its Impact on the Enhancement of the Rheological Properties of Geopolymer Binders

Naturally occurring nanoclays, such as halloysite nanotubes (HNTs) are relatively cheap and abundant materials with interesting applications in the construction industry. Recently, an electrostatic interaction was discovered between halloysite and fly ash particles, which has the potential to beneficially alter the properties of some hardened products of fly ash, such as geopolymer binders. Additionally, layer-by-layer deposition can be used to enhance even further the benefits of the fly ash-nanoclay interaction. This paper describes the nature of the interaction of the nanoclay particles with fly ash and the results of mechanical and rheological testing conducted on geopolymer produced from such nanocomposites, and the implications of this discovery for construction materials.