A new technology for the building materials industry from the Brno University of Technology’s laboratories

A new technology for the building materials industry from the Brno University of Technology’s laboratories

Scientists from the Faculty of Chemistry at the Brno University of Technology have invented a new processing method for manufacturing building materials. Their method saves more energy and also reduces the environmental load.

Civil engineering has been a human activity for thousands of years. One of the widest spread building materials is concrete. Billions of tons are used every year. Forecasts assume that it will keep increasing in both advanced and developing countries. The traditional concrete mixtures binder is cement which is available and cheap but producing it is environmentally demanding, large amounts of CO2 are emitted into the atmosphere. It is stated that globally cement production produces up to 8% of this type of emissions. Scientists and researchers search for methods of reducing the adverse effects or invent new solutions that can replace the older, less perfect ones.

Experts from the Materials Research Centre, doc. Ing. Petr Ptáček, Ph.D., Ing. Tomáš Opravil, PhD., and Ing. František Šoukal, PhD. have been looking into the problems of geopolymers for a long time. These are materials which can not only replace concrete in a number of applications but they even surpass it in many properties (particularly in resistance to physical and chemical effects). In addition, industrial waste (fly ash, cinder, slag) is often used to produce them (significantly more environmentally friendly), which is another advantage from the environmental protection viewpoint. The basic raw material for preparing geopolymers is metakaolin (which can also be used as a partial substitute for cement when manufacturing concrete). Metakaolin is obtained by burning rocks containing kaolinit at temperatures of 600 to 900°C. So it is obvious that this production method is to certain extent contrary to the above environmental benefits.

Their aim was to develop a production method which would eliminate the need for heat treatment. The subject of their invention is in the method of preparing metakaolin, i.e. the X-ray amorphous (delaminated) and dehydroxylated phase, without heat treatment (calcination), which also allows less valuable input materials to be used . This can be achieved by grinding kaolinite or kaolinite clay which disintegrates the layered structure of the kaolinite (delamination) in a relatively short time and, at the same time, the structurally bound water is removed (dehydroxylation). Adding the carbonate of an alkali metal (Li2CO3, Na2CO3, or K2CO3) to the ground kaolinite significantly reduces the grinding time by 5% of the ground material weight. The result is the required phase – metakaolin.

The usability of their invention, which is patent protected, is a solely mechanical method without complicated pre-treatment (e.g. washing), so less valuable raw materials with low washouts (content of particles under 20 µm in size) or also coarse fractions which fall off during washing can also be processed. As energy demanding operations such as burning (calcination) or washing can be eliminated, this method produces great energy savings and thus reduces the production of greenhouse gases. The potential of processing less quality raw materials also means lower production costs and, last but not least, an improvement in the management of kaolinite clay resources.

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