A paper about the development of building material technologies

A paper about the development of building material technologies

A new material with geopolymer attributes has been invented by scientists at the Faculty of Chemistry at the Brno University of Technology.

Geopolymers are materials that combine utility value and physical and chemical resistances. The name can be generally understood also as “artificially created stones”. They are formed as solid bodies through so-called geopolymer reaction (alkali activation). Because a high temperature demand is not needed, the benefit – compared to producing the raw materials for similar building materials – is energy and CO2 emission savings. Waste materials such as fly ash, cinder, slag, etc. are often used in these technologies, apart from or instead of natural raw materials. Also in this case, the production processes and the formed materials are a significant method of industrial waste disposal.

The first significant contribution to the development of geopolymers was the papers of Professor V. D. Glukhovsky who, in the 1950s, managed to introduce alkali activated materials into building practice in the former Soviet Union under the name “soil cements”. The term geopolymers used today was introduced by Professor Davidovits in the years 1976-79. However, according to his explanation, only alkali activated materials should be included; these are relatively expensive and preparing them is energy demanding. So the above advantages are partly reduced in this case. In his paper (2007), associate Professor F. Škvára states that ignoring this strict definition brings us to a very extensive new group of inorganic binders with large ecological and energy potential.

The team at the Materials Research Centre Ing. Tomáš Opravil, PhD., Ing. František Šoukal, PhD., and doc. Ing. Petr Ptáček, Ph.D. focused on researching the preparation method and use of a new type of X-ray amorphous, magnesia alkali activated material which consists of activating the dehydroxylated and delaminated magnesia-siliceous raw material of the X-ray amorphous group with (sodium, potassium) water glass at an elevated temperature (90°C and higher). This material (according to Davidovits) cannot be classified as a geopolymer, but it can be regarded as a new type of the material prepared by alkali activation of dehydroxylated and delaminated magnesia-siliceous sheet silicates.

The new material is patent protected. It can be used mainly in specific applications in which the materials must be very resistant (particularly to weather effects and pH). Another wide range of use is renovating existing concrete structures, because this material can be applied to the surface by spraying or coating. The material can be used plain or mixed with aggregates or fibre reinforcement.

Another interesting feature worth mentioning is that the cited Professor Davidovits wrote a hypothesis according to which geopolymer-based technologies were used in the construction of the Egyptian pyramids and in ancient civil engineering. He also states that a similar method was used to create the ceramic material out of which the Venus of Věstonice was made between 25,000 to 29,000 B.C. (details in English can be found here). His hypotheses have not yet been credibly proved or disproved.

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