Alkali-activated materials (hereinafter: AAM), often also called geopolymers, are obtained by process where materials rich with glassy aluminosilicate are dissolved in alkali media. After the dissolution and transport of the components (Al, Si) then through poly-condensation of the Al and Si an aluminosilicate network is formed. Suitable precursors for AAM are different waste materials (fly ash, bottom ash, bio-based ashes, various slags, waste glass), but also thermally activated clay (metakaolin), and natural pozzolan (e.g. volcanic ash). Many products, which could replace traditional building products, such as concrete or ceramic, can be obtained by the alkali activation process. In recent years AAM foams have attracted much attention since they are inorganic, non-combustible material for whose production waste materials can be utilized, and the process takes place at relatively low temperature. Foams are formed by adding either preform organic foams and/or by adding of foaming agent which reacts with a slurry or it decomposes into a gas which remains trapped inside the structure. To obtain a stable, uniformly porous structure many parameters play role in the process, and have been subject of our investigations. Results were presented as invited lecture at the 1st International Conference on Advanced Production and Processing, 2019, Novi Sad.
B.04 Guest lecture
COBISS.SI-ID: 2488679Mechanical and chemical properties of AAM are strongly dependent on the type and amount of precursor, activator, the curing regime, particle size etc. The objective of this study was to evaluate the influence of different type and amount of precursors on mechanical properties of hardened fly ash based AAM. For better understanding of the alkali activation process also in situ Fourier-Transform Infrared spectroscopy (FTIR) was carried out. After characterization of FA by means of XRF, XRD and particle size analysis various mixtures with different slag/activator ratios were prepared (activator/FA = 0.40; 0.40 and 0.37 where the activators were NaOH; Na2SiO3; and mixture of Na2SiO3/NaOH respectively). Mechanical strengths were determined at an age of 4 days after curing at a temperature of 70 °C. The values of bending strength were in the range from 1 to 9 MPa whereas compressive strength measurements were between 30 and 60 MPa. With the FTIR in situ measurements two phenomena were followed: i) the decrease of the H2O bands intensity (at ~ 3300 and 1640 cm-1) in order to follow the water consumption in reaction, and ii) the displacement of the main peak between 950 and 1000 cm-1 which is attributed to the Si-O-Si/Al streching vibration and is altering due to the Si/Al/O network rearangement during the alkali activation process.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 2471527In the present study, the properties of alkali activated fly ash based foam materials were studied at room temperature as well as at elevated temperatures (up to 1200 °C) in order to develop a durable material in terms of their mechanical properties and suitability for high temperature applications. Foams were resistant up to 1000 ° C; their mechanical properties were significantely increased after firing.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 2528103