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Geopolymers for building and infrastructures, transport, recycling and biomaterials

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Geopolymers are aluminosilicate or phosphate based synthetic inorganic polymers that are chemically bonded at T<300°C. This technology allows to produce ceramic type materials with the same facility as some plastics, removing heavy equipment and high temperatures from the ceramic industrial plants. Actually geopolymeric devices can be produced by moulding and following machining and finishing are not required. Geopolymers are environmentally friendly and sustainable. It has to be underlined that geopolymers are always composite materials: geopolymeric resin acts like a glue sticking the inert fillers which functionalize or reinforce the materials.

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Geopolymers are applied in many sectors, such as:

  • transport
  • building and infrastructures
  • metallurgy
  • waste management
  • restoring
  • art and decoration
  • biomaterials.

 

Fig. 1 Structural lightweight and water-proof panels for thermal insulation and soundproofing

ISTEC cooperates with Italian and international institutions to develop this technology, by studying raw materials reactivity, in particular of metakaolins, and by functionalizing the geopolymeric compositions with secondary phases such as bio-soluble fibres and ceramic particles.

Moreover ISTEC produces geopolymeric materials for structural and thermo-mechanical applications, such as:

  • lightweight panels for thermal insulation, soundproofing and fire-proofing
  • high temperature binders
  • refractory foams and coatings.

Actually, geopolymers have a high heat tolerance because they do not burn or ignite, they do not release gases or smokes and they do not “explode” because they do not incorporate waters of hydration within the structure as hydraulic cements do. Industrial wastes and by-products can be recycled as raw materials or inert fillers for this kind of application.

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Fig. 2 Examples of Industrial wastes and by-products recycling for the production of structural panels for building insulation

In biomaterials field, dental calcium-aluminium-phosphate cements have been developed with controlled radiopacity

PUBBLICATIONS:

 

V. Medri, M. Mazzocchi, A. Bellosi, Doped Calcium-Aluminium-Phosphate Cements for biomedical applications, Journal of Materials Science: Materials in Medicine, 2010, doi:10.1007/s10856-010-4205-3.

V. Medri, S. Fabbri, J. Dedecek, Z. Sobalik, Z. Tvaruzkova, A. Vaccari, Role of the morphology and the dehydroxylation of metakaolins on geopolymerization, Applied Clay Sciences, 50, 538–545 (2010).

C. Leonelli, E. Kamseu, V. Medri, S. Fabbri, Materie prime di origine naturale nel processo di geopolimerizzazione, Ceramica Informazione, Luglio-Agosto 489 2010, 305-310.

V. Medri, Applicazione dei geopolimeri come materiali composite coibentanti e refrattari, Ceramica Informazione –Speciale Cerasaie 2009, 83-86.

V. Medri, Geopolimeri: “Ceramiche” per uno sviluppo sostenibile, L’Industria del Laterizio, 115 gennaio-febbraio 2009, 48-53.

PROCESSES & FACILITIES:

To produce geopolymers the first step is raw materials characterizationin order to evidence:

  • morphology (SEM, granulometric distribution),
  • specific surface area (BET),
  • chemical composition (ICP-OES),
  • crystalline phases and degree of crystallinity (XRD)..

These characteristics give indications about the powder reactivity during the geopolymerization process. Thanks to international cooperation, techniques such as 27Al MAS NMR and FTIR spectroscopies are used to determine aluminium coordination, that is tetrahedral in geopolymers, and geopolymerization degree.

Geopolymer preparation follows the same procedure of cements, i.e.:

  • mechanical mixing of the reactive powder with and aqueous binder and functionalizing fillers,
  • moulding,
  • setting at controlled temperature (T<300°C) on the base of the raw powders.

As the setting is not hydraulic, alkaline (potassium or sodium silicate or hydroxides) or acid (phosphates) aqueous solutions with known concentration should be used for the chemical consolidation. Setting times are evaluated by Gilmore needles test.

Porous geopolymeric materials are produced by using foaming agents and the porosity is estimated by porosimetric analyses in the nano-to-ultra-macro range. Water-proof agents can be used for developing of hydrophobic surfaces.

Structural geopolymers are thermo-mechanical characterized by:

  • dilatometry
  • simultaneous thermal analysis
  • flexural and compressive strength

MAIN SCIENTIFIC COLLABORATIONS:

  • Geopolymers Group of the Italian Ceramic Society
  • J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic
  • Department of Industrial Chemistry and Materials, University of Bologna.
  • National Project (MISE) on the developing of anti-vibration and sound-proofing panels.