Issue 38

U. Haider et alii, Frattura ed Integrità Strutturale, 38 (2016) 305-318; DOI: 10.3221/IGF-ESIS.38.41 307 E XPERIMENTAL CAMPAIGN Separation method STM Class F brown coal raw fly ash produced by Počerady power plant of Czech Republic was used to carry out wet separation. Initially, 600 ml of water was added to a graduated 1000 ml glass cylinder followed by 400 grams of raw fly ash, making up a total volume of 800ml. After this, the resulting mixture was well shaken for about fifteen minutes manually and left at room temperature for duration of 4 hours. After such a time, three distinct layers of raw fly ash solution were observed, as shown in Fig. 1. The particles of first layer were greenish grey in colour, including black particles which floated on the surface and comprised of about 10ml volume. Clear water of about 400ml was observed. The second layer is comprised of 250ml volume of greyish green particles of raw fly ash, and third layer is comprised of greyish black particles of 150ml volume. It was seen from the results of tests carried out that second and third layer varied from 40 to 60% of the volume. Figure 1 : Wet separation of raw fly ash in laboratory. Tests to determine physical properties Particle size analysis of raw fly ash and separated fly ash particles were carried out on Fritsch Analysette 22, a laser particle size analyser, using its wet dispersion unit. Density of raw fly ash, and its separated parts, was determined using helium Pycnometer, Pycnomatic ATC. Specific surface areas of raw fly ash, and its separated parts, were measured using BET method on PC-controlled volumetric gas-adsorption system Sorptomatic 1990. Optical images of particles were observed by using a Zeiss (Germany) Axio Imager optical microscope. Mercury intrusion porosimetry tests were carried out to measure the porosity of cementitious samples using Pascal 440 Porosimeter manufactured by Thermo scientific (USA). For moisture content determination, the cementitious specimens were fully saturated by fully immersing in water under vacuum for 24 hours. After fully saturating the specimens they were placed in the oven at 50 o C and were weighed at 1, 2, 7, 14, and 30 days to check the moisture difference. Tests to determine morphological properties, chemical composition and mineralogical properties In order to determine morphology of raw fly ash and its separated particles, images were captured by HE-SE detector on Merlin Carl Zeiss (Germany) field emission electron microscope (FE-SEM). Large / total area analysis were carried out to by using rectangular selection tool in EDX software AZtecEnergy in order to determine overall chemical composition up to thirty elements. A First layer Second layer Third layer