Influence of Fly Ash Form Co-Combustion of Coal and Biomass on Scalling Resistence of Concrete

Industrial utilization of fly ash from various kinds of fuel plays an important role in the environmentally clean and cost effective power production. The primary market for fly ash utilization is as a pozzolanic addition in concrete production. The paper concerns the concretes containing fly ash called Fly Ash from Biomass (FAB) from co-combustion of hard coal and wood biomass (wood chips). Characterization of the fly ash was carried on by means of X-ray diffractometry and E-SEM/EDS analysis. The results of laboratory studies undertaken to evaluate the influence of FAB on concrete resistance to surface scaling due to cyclic freezing and thawing in the presence of NaCl solution were presented. The tests were carried out for concretes containing up to 25% of fly ash related to cement mass. Additionally, the microstructure of air-voids was described. It was concluded that the FAB has significant effect on concrete freeze/thaw durability. The replacement of cement by fly ash from co-combustion progressively transformed the concrete microstructure into less resistant against freeze/thaw cycles and excessive dosage (over 15%) may dangerously increase the scaling. Industrial utilization of fly ash from various kinds of fuel plays an important role in the environmentally clean and cost effective power generation. The primary market for fly ash utilization is as a pozzolanic addition in concrete production. The possibility of the utilization of these ashes as an active concrete addition is determined by their chemical and mineralogical composition. The paper concerns the concretes containing fly ash called Fly Ash from Biomass (FAB) from co-combustion of hard coal and wood biomass (wood chips). Characterization of the fly ash was carried on by means of X-ray diffractometry and E-SEM/EDS analysis. The results of laboratory studies undertaken in order to evaluate the influence of FAB on concrete resistance to surface scaling due to cyclic freezing and thawing in the presence of NaCl solution are presented. The tests were carried out for concretes containing up to 25% of fly ash related to cement mass. Additionally, the microstructure of air-voids was described. The tested fly ash can be considered as a supplementary cementing material. The test results pointed out the pozzolanic activity of fly ash. The density and porosity of fresh concrete is strongly affected by fly ash content. The rate of strength increase in fly ash concrete was slower and sustained for longer periods. However, the concretes containing fly ash, in considered range of FAB/C values, were capable of developing the compressive strength comparable with Portland cement concrete strength. The efficiency of air-entraining agent was influenced by the fly ash content in concrete mix. The scaling resistance in all tested concretes decreased with the content of FAB, but the changes in scaling resistance, for both 5% and 15% cement replacement by FAB, were not significant. The addition of 25% of