Valorisation of woody biomass bottom ash in Portland cement: A characterization and hydration study

In the present research work, a characterization of a bottom ash derived from olive plants trimmings combustion was carried out in order to examine its suitability as a substitute in the production of composite cements. For that purpose six different mixtures were prepared: a reference one, containing only ordinary raw materials and five others, substituting Portland cement for 2, 3, 5, 7 and 10 wt%. The woody bottom ash (WBA) characterization was carried out by using particle size distribution analysis, chemical analysis and X-ray diffraction (XRD), whereas its microstructure and morphological characteristics were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The physicochemical and mechanical properties of the produced cements mixtures were examined by means of their initial and final setting times, standard consistency, flow of normal mortar, soundness and compressive strength at 1, 2, 7 and 28 days. Their hydration progress was attested by X-ray diffraction, thermogravimetric/differential thermal analysis (TG/DTG), whereas the microstructure of the hardened cement pastes was examined by SEM. According to the results, the WBA could be used as a substitute for Portland cement, in the production of composite cements of the strength classes 42.5 and 32.5 of EN 197-1.