Abstract
Costs and environmental impacts are currently the critical parameters of construction works. One way to fulfill these criteria is the use of alternative materials. In the Slovak Republic, it is primarily the waste from the power industry, which landfilling fees are still high as well as increasing negative impact on the environment. Fly ash (FA) is defined as a fine grained residue of coal combustion in thermal production stations of electrical energy, which particles are smaller and almost totally spherical in shape, allowing them to fill voids, flow easily, and blend freely in concrete mixtures. Fly ash, a by-product of the coal-burning power industry, is a rich cementitious industrial waste which has the great potential to substitute Portland cement, a major producer of CO2. Research in Slovakia showed that despite the strict criteria and the requirements of technical standards (maximum use of Slovak FA of 5 %; the currently worldwide information say about high volume concrete with 60-80 % of FA cement replacement), the Slovak brown coal fly ash due to its characteristics can be used in the building industry as a replacement for cement component in concrete with minimum of 15 % FA. Based on the calculations, the substitute by fly ash represents for the construction companies of the area of High Engineering, savings tens of thousands of euros/km of roads. It is true; however, only meeting the specific standard criteria i.e. mechanical (strength characteristics), chemical (frost and chemical resistance) and economic indicators are not sufficient for the concluding statement of FA utilization. In terms of comprehensive assessment, it is necessary to draw attention to the analysis of its life cycle. The study of main environmental parameters, but also of the FA- concrete durability is the aim of this paper. Obtained results again confirm that in terms of hazardous elements content and of calculated environmental profiles (environmental impact), the fly ash is a suitable cement replacement in concrete.
