| Abstract [eng] |
The main aim of the project was to evaluate the possibility to use pozzolanic additive synthesized from illite clay and biomass fly ash. It was found that illite clay is mostly made of SiO2, Al2O3, CaO, main minerals – quartz, calcite, gismondine. Bio fly ash consist of SiO2, CaO, main mineral – quartz. According to the literature, materials with large amount of SiO2 can be used as raw materials for synthesis of pozzolanic additives. During the synthesis of the additive’s different parameters and their influence on pozzolanic activity were monitored: grain size of bio fly ash, ratio of bio fly ash to illite clay, the temperature of synthesis. It was concluded that additive containing 20% of whole bio fly ash and 80% illite clay synthesized at 500 °C degrees, was the best pozzolanic additive with value of 88,23 mg CaO/g. Bio fly ash has small but positive effect on pozzolanic activity, for example just thermally activated clay without bio fly ash had the pozzolanic activity of 73,16 mg CaO/g (17% less). Influence on hydration process and mortar properties where monitored when 5 – 25% of CEM I was replaced with the pozzolanic additive. It was found that in samples with the additive the induction period was shorter, and the hydration process was a bit faster, heat content and the compressive strength was reduced in comparison with pure Portland cement. While analyzing results of XRD and DSC-TG it was observed that with increased time of hydration, the intensity of peaks specific to portlandite and mass loss decreased. This information confirms the presence of pozzolanic reaction. According to the literature positive effect of bio fly ash on mortar can be observed after ≤28 days, that is why it was decided to make some samples with 5% of additive that had 14,3% lower value of pozzolanic activity (75,58 mg CaO/g) and hydrate it for 28 days. It was found that the influence on the hydration process of this additive was the same as the previous one. It is worth mentioning that after 28 days the sample with 5% of additive containing 60% illite clay and 40% bio fly ash had 3,2% higher compressive strength in comparison with sample containing 5% 80|20 additive. While analyzing XRD and DSC-TG specific peaks to portlandite where less intense, mass loss was lower. All the results let to assume, that the pozzolanic reaction is more intense in systems with higher amount of bio fly ash. |
