Regulating the chemical foaming reaction to control the porosity of geopolymer foams

Hajimohammadi, Ailar; Ngo, Tuan; Mendis, Priyan; Sanjayan, Jay

doi:10.1016/j.matdes.2017.02.026

Cited by 135 publications

(77 citation statements)

References 54 publications

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“…The IP activated with the 1.4 solution took longer to initiate the foaming, but the setting of the IP was also postponed in this case, long enough for the foam to be further developed before setting. This contradicts the findings of Hajimohammadi et al . on fly ash system, who stated that increasing the NaOH‐to‐sodium silicate ratio (lower SiO 2 /Na 2 O ratio) resulted in an increased degree of foaming and reduced foam density.…”

Section: Resultscontrasting

confidence: 84%

“…Decreasing the SiO 2 /Na 2 O ratio leads to a narrower pore size distribution and smaller pores, as previously shown in Figure . The influence of SiO 2 /Na 2 O ratio on the pore size distribution was also mentioned elsewhere, however, the opposite effect was observed in that system. These findings might be related to the presence of surfactant, which was not used in Hajimohammadi et al's study, as well as the totally different precursors used, that in practice may have an impact on dissolution kinetics and species.…”

Section: Resultssupporting

confidence: 60%

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Kinetics of pore formation and resulting properties of lightweight inorganic polymers

2019

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Inorganic polymer (IP) foams could be used as an alternative to commonly available cellular concretes. To do so, however, it is crucial to understand how the foaming kinetics and the final foam properties can be controlled and tailored to delivered the desired performance. The research reported in this article investigates the influence of the SiO 2 /Na 2 O ratio of the activating solution, addition time of foaming agent, and temperature, on the reaction kinetics and final properties of a porous IP. The IPs were formed by activating fayalite slag, a by-product of secondary copper production, with a sodium-silicate solution. Foaming was achieved by introducing metallic Al into the formulation, oxidizing it in the alkaline environment, liberating H 2 gas, and entrapping it. Reaction kinetics were assessed using isothermal calorimetry, rheology, and a dedicated setup to record the foaming. The mechanical and physical properties of the foam were assessed via compressive strength and water absorption measurements. Microstructural analysis was undertaken using electron microscopy and computed tomography. The results showed that by decreasing the SiO 2 /Na 2 O ratio and/or increasing the temperature, the reaction kinetics were accelerated. Regarding the properties, postponing the initiation of the foaming led to more uniform and smaller pores, resulting in an increased compressive strength-to-density ratio. K E Y W O R D Sinorganic polymers, kinetics, pore formation, porous materials

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Section: Resultscontrasting

confidence: 84%

Section: Resultssupporting

confidence: 60%

Kinetics of pore formation and resulting properties of lightweight inorganic polymers

2019

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“…Chemical and mechanical foaming methods are generally used. In chemical methods, density can be reduced but large voids are generated [65].…”

Section: Foamed Geopolymer Concretementioning

confidence: 99%

Fly Ash-Based Geopolymer Binder: A Future Construction Material

Singh

2018

Minerals

168

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A large amount of waste coming out from industries has posed a great challenge in its disposal and effect on the environment. Particularly fly ash, coming out from thermal power plants, which contains aluminosilicate minerals and creates a lot of environmental problems. In recent years, it has been found that geopolymer may give solutions to waste problems and environmental issues. Geopolymer is an inorganic polymer first introduced by Davidovits. Geopolymer concrete can be considered as an innovative and alternative material to traditional Portland cement concrete. Use of fly ash as a raw material minimizes the waste production of thermal power plants and protects the environment. Geopolymer concretes have high early strength and resistant to an aggressive atmosphere. Methods of preparation and characterization of fly ash-based geopolymers have been presented in this paper. The properties of geopolymer cement/mortar/concrete under different conditions have been highlighted. Fire resistance properties and 3D printing technology have also been discussed.

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“…The calculated values of total porosity P t and the corresponding bulk density are in accordance with data trends reported by other authors for metakaolin and fly ash geopolymers foamed with different amounts of H 2 O 2 , comprised between 1.2 and 5.0 wt. % [18,32,33] or different amounts of Si or Al [15][16][17][18][19][20][21]: among the considered geopolymers, the biomass-based composite MKBM50 stands as one with the highest total porosity/bulk density ratio ( Figure 6). The reported histograms highlight a bimodal pore size distribution: more than 60% of the total pore volume lays in the diameter range between 0.007 µm and 0.1 µm and about 23% is determined by voids with equivalent diameter comprised between 20 µm and 200 µm.…”

Section: Density Pore Size Distribution and Compressive Strengthmentioning

confidence: 99%

“…Geopolymer composites can meet many of the ideal characteristics of lightweight materials for the building and transportation sectors, such as non-flammability, high temperature resistance, chemical resistance against acids and alkalis, durability, safety for human health and low carbon footprint [4,12,14]. For such remarkable properties, geopolymers and geopolymer composites have been widely investigated for the design of insulating materials in buildings and constructions, exploiting their intrinsic porosity eventually coupled with an induced macro-porosity by direct foaming [15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Porous Geopolymer Insulating Core from a Metakaolin/Biomass Ash Composite

et al. 2017

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Ashes derived from the combustion of vegetal and animal biomass still represent a mostly unexplored secondary raw material for the production of alkali-activated materials, given their peculiar chemical nature. In this work, calcium phosphate biomass ashes were successfully used as partially reactive fillers in a metakaolin-based geopolymer composite to produce, by direct foaming, sustainable and lightweight boards with thermal insulating properties. The investigated materials were obtained by activating a blend of metakaolin and biomass ash in a weight ratio of 1: 1 and foamed with the addition of H 2 O 2 in measure of 5 wt. %, to maximize the volume of disposed ash and ensure adequate properties to the material at the same time. The obtained geopolymer composite was characterized by microstructural, chemical-physical, mechanical and thermal analysis: the obtained results showed that biomass ash and metakaolin well integrated in the microstructure of the final porous material, which was characterized by a density of about 310 kg/m 3 and a thermal conductivity of 0.073 W/mK at a mean test temperature of 30 • C, coupled with an acceptable compressive strength of about 0.6 MPa. Dilatometric and thermogravimetric analysis, performed up to 1000 • C, highlighted the thermal stability of the composite, which could be regarded as a promising material for low-cost, self-bearing thermal insulating partitions or lightweight cores for thermostructural sandwich panels.

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Regulating the chemical foaming reaction to control the porosity of geopolymer foams

Cited by 135 publications

References 54 publications

Kinetics of pore formation and resulting properties of lightweight inorganic polymers

Kinetics of pore formation and resulting properties of lightweight inorganic polymers

Fly Ash-Based Geopolymer Binder: A Future Construction Material

Porous Geopolymer Insulating Core from a Metakaolin/Biomass Ash Composite

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