Use of fly-ash for the production of hydraulic binding agents and for soil stabilisation / Zastosowanie Popiołów Lotnych Do Produkcji Spoiw Hydraulicznych I Wzmacniania Gruntu

Fly-ash is a form of production waste produced as a result of the burning of coal for energy production. Millions of tonnes of this waste are produced worldwide every year; hence it is extremely important to dispose of it in a useful way, including through treating the initial rawmaterial to obtain amaterial of higher quality. The aim of the present work is to determine the suitability of processed fly-ash from lignite for reinforcing (stabilizing) soils used in the building of road foundations and embankments. The results provide a method of recycling this waste while at the same time obtaining new materials and technologies for use in road building. This is an important issue both environmentally and in terms of the positive effect that processed fly-ash can have on the stability of road structures. This article presents the results of experiments carried out using fly-ash produced from lignite at the P¹tnów Power Plant. This ash was first modified (activated) using a Wapeco magnetic activator, and then used to produce hydraulic binders (with the addition of cement) and soil-binder mixtures. These mixtures were made using natural soils from seven different deposits in the Lubuskie region (western Poland). They were stabilized using two hydraulic binders (strength ratings 3 MPa and 9 MPa) added in different amounts (6% and 8% relative to the mass of the soil). During the experiment, a determination was made of the increase in the strength of the analysed samples (after 14, 28, and 42 days) and the increase in the bearing ratio (immediately after consolidation and after 7 days). Interpretation of the results of the experiment made it possible to assess the dynamics of the increase in compression strength and load-bearing capacity of various soils stabilized with hydraulic binders produced from lignite ash, and to indicate possibilities for the use of these materials. The analysis showed that it is possible to use these binders for the stabilisation of soils, enabling soils formerly considered to have weak load-bearing capacity (clayey sand; clayey, sandy gravel; clays) to be classified as fully usable in road construction.