Alkali Activated Binders and Their Application
2015
Ģirts Būmanis

Defending
03.07.2015. 14:15, RTU Būvniecības Inženierzinātņu fakultātes sēžu zāle Rīgā, Āzenes iela 16/20, 213.kab.

Supervisor
Diāna Bajāre

Reviewers
Ina Pundiene, Danute Vaičiukyniene, Juris Smirnovs

In the framework of thesis a group of porous alkali activated binders (AAB) was created and the effect that composition of raw materials has on the properties of the obtained materials was justified. By changing mixture composition, the materials, which are suitable for application in the following sectors: construction, energetics and water management, were obtained. AAB were obtained by using calcined low carbonate clay (calcined kaolinite or illite clay) and sodium silicate activation solution with different silicate modulus. New porous materials with significantly different properties were obtained by adding pore forming raw materials (aluminium scrap recycling waste or commercially available Al(OH)3 paste) to AAB. Glass additives contribute to the alkali leaching rate from the structure of alkali activated materials that significantly increases efficiency of the material use in biotechnological processes. In addition, the above mention is closely related to the chemical composition of glass that is used. By conducting research on the basic principles of binder formation after composition has been activated in alkaline environment, it is possible to predict changes in the properties of materials depending on the chemical composition and proportions of the raw materials. For the first time it was proved that calcined low carbonate illite clay from Latvia, Liepa clay deposit, can be used as a raw material for the production of AAB. Although the mechanical properties of these binders are lower compared to the binders produced from calcined kaolinite clay, by using alkali activation process it is possible to obtain a porous material with excellent thermal properties. Production of alkali activated binder is characterised with lower CO2 emission rates compared to the production of traditional Portland cement and it corresponds to the guidelines of sustainable binder production existing in the world. Conducting this research both local natural resources and industrial waste were used. Use of waste for production of new materials gives an opportunity for effective waste recycling including those regarded as dangerous for the environment. In some experiments natural kaolinite clay was replaced with metakaoline that is production by-product thus promoting use of the recycled materials and saving natural resources. By using pore forming binders in various concentrations it is possible to obtain building materials with density 540 to 675 kg/m3. Type of the clay that is used has significant impact on the mechanical and durability properties of the construction materials. Construction materials based on metakaoline have higher compression and flexural strength, they have better freeze-thaw resistance as well as better resistance to sulphate attack compared to the construction materials based on Illite clay. High porosity (71-79 %) determines mechanical properties of the material (compressive strength 1.4-3.8 MPa) and thermal conductivity (0.14-0.16 W/mK). Efficient use of the alkali activated materials in the energetics sector - biogas production - is achieved by including glass raw material in the mixture composition of the material. With high Na2O content (21 %) in the material its capability of leaching hydroxide ions and ensuring buffer capacity of the environment is ensured. Therefore this material can be used as an efficient stabilizer of pH levels in bioreactors, where acidic substrates, such as cheese whey, are used for biogas production. The results of alkali activated binder use in bioreactors increasing the efficiency of biometan production, are described in thesis prepared by the RTU doctoral candidate Kristine Rugele (defending of thesis scheduled for March, 2015). Water treatment systems that should maintain the necessary pH levels in a long term, are suitable for thermally treated alkali activated materials (thermal treatment at 200 and 400 °C), which are produced from raw materials not coming from waste. It led to obtaining alkali activated materials which are efficient for pH regulation in water treatment systems and can ensure stable water pH level from 10.0-10.5 in a long term (up to 25 days).


Keywords
Sārmu aktivizētas saistvielas, porains materiāls, sārmu aktivizācija

Būmanis, Ģirts. Alkali Activated Binders and Their Application. PhD Thesis. Rīga: [RTU], 2015. 139 p.

Publication language
Latvian (lv)
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