ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 61, (4) 327 - 339 (2017)

Jankovský Ondřej 1, Pavlíková Milena 2, Sedmidubský David 1, Bouša Daniel 1, Lojka Michal 1, Pokorný Jaroslav 2, Záleská Martina 2 , Pavlík Zbyšek 2
1 Department of Inorganic Chemistry, Faculty of Chemical Technology, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic
2 Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague 6, Czech Republic

Keywords: Biomass combustion, Wheat straw ash, Chemical and physical analysis, Pozzolana activity, Cement blends, Strength activity index

Wheat straw ash coming from combustion of packed wheat straw was studied as a potential pozzolana active admixture for blended cements. X-Ray fluorescence, X-Ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy were used to examine chemical and mineralogical composition, morphology and elemental distribution of a raw untreated ash. Due to high carbon content, the wheat straw ash was thermally treated for 2 hours at 700 °C and analyzed again using the same analytic techniques. Thermal treatment process was monitored using simultaneous thermal analysis and Fourier Transform infrared spectroscopy. The pozzolana activity was assessed using Chapelle and Frattini tests. In the next step, wheat straw ash was used for preparation of blended cement pastes. The content of ash in the blends was 10, 15, and 20% by mass. For the hardened pastes, basic physical properties, mechanical parameters, and pore size distribution were measured. For fresh past mixes, workability was tested. Moreover, leachability of chlorides, nitrates, sulfates and alkalis from paste samples was studied. The experimentally obtained data pointed to the high pozzolana activity of wheat straw ash and sufficient mechanical properties of cement pastes with the ash content up to 20 mass% of cement. In summary, the analyzed waste product from biomass combustion was found to be applicable as a part of cement-based blended binder providing economic and environmental benefits for concrete industry.

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doi: 10.13168/cs.2017.0032
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