Title: Mechano-chemistry: an innovative process in the industrial production of poly-sialate and poly-silanoxosialate geopolymeric binders used in building construction
Area: 1 – High-performance Factories
Call topic: 1.2 – Innovative technologies for the carrying-out of components characterized by advanced functional features
Coordinating Institute: IMC – Methodological Chemistry Institute (Rome)
- IGAG – Institute of Environmental Geology and Geoengineering (Rome)
- ISTEC ‐ Institute of Science and Technology for Ceramics (Faenza)
- ISMN – Institute of Nanostructured Materials (Bologna)
Industrial Interest Group:
- Aero Sekur S.p.A. (Aprilia)
- Contento Trade S.r.l. (Pozz.lo del Friuli (UD))
- Assing Sp.A. (Rome)
- Matteo Brioni S.r.l. (Modena)
Abstract: Mechano-chemical processes are proposed here as a simple and reliable solution to activate alumino-silicate materials in the industrial synthesis of poly-sialate and poly-syloxosialate geopolymeric binders used in the production of casted structures for building purposes. With this technology, natural materials can be activated toward the alkaline attack when enough mechanical energy is transferred to them by collision with external bodies. Mechano-chemical transformations can be performed in all types of mills where the moving parts are accelerated at sufficiently high speed. The proposed technology can greatly simplify the industrial production chain of geopolymeric binders, as it combines in one step the conventional grinding and thermal treatments used today to activate kaolinite and other alumino-silicate based materials. Prototypes of geopolymers synthesized with this process will realized together with a demonstrator mill able to work in a production representative environment.
Ideas and solutions:
Kaolin was chosen because the amorphous phase obtained by thermal treatment (metakaolin, MKA) is the most reactive component used in the synthesis of geopolymers, to get geopolymers with the desired Si/Al ratio, in our case, to get geopolymers with a Si/Al=2 and K as compensatory cation. This type of geopolymers (K-PS geopolymers) are known to combine a good mechanical and thermal resistance with very high cementing properties for various types of materials (stones, glass, wood, and even some metals). The advantage with respect to thermal treatment, that are carried out between 650° and 750°C, is that the time required to activate MKA is shorter and the production can be regulated as a function of the market demand. We also decided to see if the mechano-chemical treatment could have activated two volcanic tuffs with different Si/Al ratio as they are much cheaper than kaoilin, and cannot be heated without melting.
To test the industrial feasibility of the mechano-chemical processing, a small scale industrial mill intended for continuous operation was modified to work in a semi-continuous mode. To prove its ability to work in an industrial environment, it was installed in a small plant for the production of zeolites near Siracusa where it worked continuously for six months without any problem. The material grinded was volcanic ash from the Etna volcano. The results obtained were used to design a large mill able to treat several hundreds of kilograms per day. Several companies were contacted, but no one ensured that the construction of a such prototype was possible before one year. Calculations performed on the efficiency of this system indicated that the energy consumption was comparable to that of the thermal treatment, but this was obtained with a much lower environmental impact and lower running costs. The results of the project go beyond the synthesis of geopolymeric cements, as the mechano-chemical processing can also be suitable to activate conventional materials such as clinker or mixtures of clinker and other materials to make better cements.