The current widespread use of calcium silicate or aluminate hydrate binder systems in the construction industry finds its roots in the Antique world where mixtures of calcined lime and finely ground reactive (alumino-)silicate materials were pioneered and developed as competent inorganic binders. Architectural remains of the Minoan civilization (2000-1500 BC) on Crete have shown evidence of the combined use of slaked lime and additions of finely ground potsherds to produce stronger and more durable lime mortars suitable for water-proof renderings in baths, cisterns and aqueducts (Spence and Cook 1983). It is not clear when and where mortar technology evolved to incorporate volcanic pumice and ashes as a functional supplement. A plausible site would be the Akrotiri settlement at Santorin (Greece), where archeological indications of strong ties with the Minoan culture were found and large quantities of suitable highly siliceous volcanic ash were present. This so-called Santorin earth has been used as a pozzolan in the Eastern Mediterranean until recently (Kitsopoulos and Dunham 1996). Evidence of the deliberate use of this and other volcanic materials by the ancient Greeks dates back to at least 500-400 BC, as uncovered at the ancient city of Kamiros, Rhodes (Efstathiadis 1978; Idorn 1997). In the subsequent centuries the technological knowledge was spread to the mainland (Papayianni and Stefanidou 2007) and was eventually adopted and improved by the Romans (Mehta 1987). The Roman alternatives for Santorin earth were volcanic pumices or tuff found in neighboring territories, the most famous ones found in Pozzuoli (Naples), hence the name pozzolan, and in Segni (Latium). Preference was given to natural pozzolan sources, but crushed ceramic waste was frequently used when natural deposits were not locally available. The exceptional lifetime and preservation condition of some of the most famous Roman buildings such as the Pantheon or the Pont du …

Supplementary Cementitious Materials

The present state of the methods commonly used for characterization of the phase, mineral, and chemical composition of fly ashes from coal-fired power stations is described and summarized. The application of various methods is briefly discussed; these methods include macroscopic observations, ashing procedures (high-temperature and low-temperature), physical separations (density, magnetic, particle size, froth flotation, and electrostatic), chemical leaching, sequential physical and chemical treatments, as well as optical microscopy (reflected and transmitted), electron microscopy (scanning and transmission), X-ray diffractometry, differential thermal and thermogravimetric analyses, Mossbauer and infrared spectroscopy, and different chemical analyses. A short critical overview on the advantages and limitations is given, as well as certain recommendations during application of the above-listed methods. Some considerations about the practical use of data for fly ash composition are also present.

Methods for Characterization of Composition of Fly Ashes from Coal-Fired Power Stations: A Critical Overview

Mineralogy of combustion wastes from coal-fired power stations

New perspectives for coal ash utilization: synthesis of zeolitic materials☆

Behaviour of elements and minerals during preparation and combustion of the Pernik coal, Bulgaria

Observations on the nature of fly ash particles

The concentrations of 20 elements in two suites of coal samples from India were determined by RABBIT neutron activation analysis (NAA) and x-ray fluorescence spectroscopy (XRF). Sulphur was determined by Leco and ash was determined in the lab at approximately 550°C. One group of samples was collected from feed coals at 11 power plants representing approximately 15% of all the coal burned in India: Korba, Madhya Pradesh (6 plants); Talcher, Orissa (1); Neyveli, Tamil Nadu (2); and Delhi (2). Effective coal concentration (ECC) is defined here as the total amount of a given element mobilized yearly due to coal utilization. For the above plants the ECC are (metric tons/year): ash (7.896 × 106), Al (1.031 × 106), Ba (3,768), Ca (1.03 × 105), Cl (2,229), Co (72), Cr (580), Dy (148), l (108), ln (1), Mg (4.02 × 105), Mn (1.921), Na (6,834), Ni (317), Rb (325, only 10 plants included), S (2.06 × 105), Si(2.017 × 106), Sr(l,325), Ti(77,340), V(1,128), andZn (642). A second set of channel samples was colle...

Coal utilization in India; Mobilization of selected elements to the surface environment

At the ICAR-IIWM research farm in Odisha, a study was carried out during the rabi season to assess the effects of agromet indices on the cowpea variety Kashi uttam during the two growth seasons of 2018–19 and 2019–20. Different growing seasons and a delay in sowing had a significant impact on the length of phenological stages and accumulation of agro-climatic indices (Growing Degree Days, Photothermal Units, and Heliothermal Units). The findings showed that distinct growth phases at the second growing season were responsible for the greater GDD and PTU. However, the decrease in HTU during the second growing season showed that the crop required fewer heat units as a result of the second growth season's considerably lower number of sunshine hours. Among the seasons and sowing dates, the meteorological indices accretion was perceived in 2nd growing season as compared to 1st growing season crop. Second season crop had sown earlier and get highest heat use efficiency.

K.C. Sahu

Papers

Observations on the nature of fly ash particles

Coal utilization in India; Mobilization of selected elements to the surface environment

Evaluation of the Agromet Indices Impact on Cowpea Crop at Khurdha District of Odisha, India