The leaching protocols available for the evaluation of the long-term environmental impacts of building composites containing waste materials were assessed. For evaluating the long-term environmental impacts the NEN 7375 test has been proposed. Over a period of 64 days, at specific points in time, the leaching solution (demineralised water) is replenished. By applying the NEN 7375 test, leaching of contaminants that is based mainly on diffusion is followed. In this work, new leaching tests were proposed using synthetic surface and seawater as leaching solutions for the evaluation of the leaching of selected elements and chromate, molybdate and vanadate from compact and ground building composites (98% mixture of fly ash (80%) and cement (20%), and 2% of electric arc furnace (EAF) dust) over 6 months. The leaching solutions were not replenished, imitating both the diffusion and the dissolution of contaminants. The data revealed larger extent of leaching when solution was not replenished. Synthetic sea and surface water used as leaching solutions, without replenishing, were found to be suitable to simulate the conditions when the building material is immersed in stagnant environmental waters.
COBISS.SI-ID: 29929767
In the present work compact and ground cement composites in which 30% of cement by mass was replaced by ladle slag were investigated for their chemical and physico-mechanical properties. To evaluate longterm environmental impacts, leachability test based on diffusion, which combined both, diffusion and dissolution of contaminants, was performed in water and saline water. Total element concentrations and Cr(VI) were determined in leachates over a time period of 180 days. At the end of the experiment, the mineralogical composition and the physico-mechanical stability of cement composites was also assessed. The results revealed that Cr(III) and Cr(VI) were immobilized by the hydration products formed in the cement composites with the addition of ladle slag. Cr(VI) content originating from the cement was also appreciably reduced by Fe(II) from minerals present in the added ladle slag, which thus had significant positive environmental effects. Among metals, only Mo and Ba were leached in elevated concentrations, but solely in ground cement composites with the addition of ladle slag. It was demonstrated that the presence of ladle slag in cement composites can even contribute to improved mortar resistance. The investigated ladle slag can be successfully implemented in cement composites as supplementary cementitious material.
COBISS.SI-ID: 28586535
Based on a road reconstruction case study, the advantages and disadvantages of two alternative road pavement rehabilitation techniques, a hypothetically defined comparable traditional approach and an actually used cold-in-place-recycling approach were investigated by means of Life Cycle Assessment. The results showed that the considered environmental impacts of the traditional approach exceeded those of the cold-in-place-recycling approach: by only 1% with regard to Global Warming, by 18% with regard to Acidification, by 15% with regard to the Abiotic Depletion of Fossil Fuels, and by 16% with regard to primary energy consumption. In the case of the traditional approach, the use of larger amounts of natural aggregate and the transportation of materials significantly contributed to emissions and the consumption of fossil fuels and energy, whereas the cold-in-place-recycling approach was sensitive to the use of cement, whose production results in relatively high emissions, especially of greenhouse gasses. In the case of the traditional approach, sensitivity analyses were carried out with regard to the use of aggregate from a quarry instead of a gravel pit, and to the delivery distance of material hauled away from the distressed road during rehabilitation works. It was found that, if aggregate from a quarry is used instead of from a gravel pit, then the various environmental impacts of the traditional approach would exceed those of the cold-in-place-recycling approach by factors which range between 1.3 and 1.7. A further sensitivity analysis was carried out in the case of the cold-in-place-recycling approach, with regard to the use of Portland cements containing different amounts of clinker. It was found that the use of cements with a higher clinker content results in an increase in the Global Warming impact to a level significantly higher than that of the traditional approach.
COBISS.SI-ID: 2177127
Boiler slag is a by-product that is derived from coal combustion in wet bottom boilers. Due to its low bulk density, in the compacted state it is an attractive alternative for use as structural fill material. Compared with other coal combustion by-products, the geotechnical and leaching properties of boiler slag are less known. This paper presents the results of laboratory and field investigation of boiler slag, produced in boilers where brown coal is used as fuel. Chemical and mineralogical composition, as well as mechanical properties were studied in the laboratory. A test embankment was constructed in order to identify compaction behavior and the achieved layer stiffness. A lysimeter was installed as part of the test embankment for the long-term monitoring of the quality and quantity of percolated water.
COBISS.SI-ID: 7433313
Postopki nanoremediacije so običajno načrtovani tako, da se upošteva le en kontaminant ali skupina kontaminantov. V obravnavanem delu smo uporabili celovit pristop k raziskavam procesov, ki hkrati potekajo pri čiščenju vode iz male biološke čistilne naprave (MBČN) z različnimi nanodelci nič-valentnega železa (nZVI). Preizkušene so bile tri različice nZVI: nZVI sintetizirani v laboratoriju, komercialni Nanofer STAR in Nanofer25 slurry, ki se razlikujejo po reaktivnosti in po metodah sinteze. Vzorci vode iz iztoka MBČN so bili remediirani z različnimi koncentracijami nZVI, pri različnih časih mešanja in usedanja železovih delcev, z namenom optimizacije učinkovitosti odstranjevanja izbranih potencialno toksičnih elementov (PTE), dušikovih zvrsti in patogenih bakterij (koliformne bakterije, Escherichia coli, intestinalni enterokoki in Clostridium perfringens). Rezultati so pokazali, da so laboratorijsko sintetizirani nZVI najbolj reaktivni med testiran nanodelci. Najbolj učinkovito so odstranjevali PTE in patogene bakterije. Vendar pa je uporaba laboratorijsko sintetiziranih nZVI omejena, saj v vodo sproščajo B, ki izvira iz reagentov, uporabljenih pri njihovi sintezi. V določeni meri so vse preiskovane vrste nZVI znižale koncentracije nitrata in nitrita z pretvorbo v amonijev kation. Dodatna tvorba amonijevega dušika je bila posledica interakcij nZVI z organskim dušikom, prisotnim v vodi iz MBČN. Pri optimalni koncentraciji dodanih nZVI v obliki Nanofer25 slurry, optimalnim trajanjem mešanja in usedanja smo dosegli najučinkovitejšo odstranitev PTE in dezinfekcijo patogenov.
COBISS.SI-ID: 30391847