Enhancing properties of concrete by addition of fly ash from a thermal power plant for application in geothermal systems

Abstract

Electric power in Serbia is predominantly provided by thermal power plants. All of eleven existing thermal power plants in Serbia use coal, mainly lignite in the electricity production process thus generating about 6 million tons of fly ash per year. The estimated amount of fly ash from thermal power plants accumulated in Serbian landfills exceeds 200 million tons. On the other hand, during the last decades, respecting the principles of ecologically sustainable development has been imposed on industries, and one of them is the construction industry. Due to the presence of amorphous SiO2 and Al2O3, fly ash as pozzolanic material is convenient for the production of concrete and mortar. Consequently, multiple positive effects can be expected by the proper consumption of fly ash- reducing landfills and improving concrete properties. The idea of this study is to analyze the possibility of recycling fly ash from a thermal power plant by replacing a part of common mineral filler- limestone in the production of self-compacting concrete (SCC). Properties of conventional SCC with limestone and compositions with different fly ash content were compared. Considering that requirements for SCC should be satisfied and all properties remain or enhance in the case of fly ash addition, this study proved that all designed concretes can be used for structural applications.

Električnu energiju u Srbiji pretežno obezbeđuju termoelektrane. Svih jedanaest termoelektrana u Srbiji koriste ugalj, uglavnom lignit u procesu proizvodnje električne energije, čime se godišnje generiše oko 6 miliona tona letećeg pepela. Procenjena količina letećeg pepela iz termoelektrana akumulirana na deponijama u Srbiji prelazi 200 miliona tona. S druge strane, poslednjih decenija poštovanje principa ekološki održivog razvoja nametnuto je industrijama, a jedna od njih je i građevinska. Zahvaljujući prisustvu amorfnog SiO2 i Al2O3, pepeo kao pucolanski materijal pogodan je za proizvodnju betona i maltera. Zbog toga se pravilnom upotrebom letećeg pepela mogu očekivati višestruki pozitivni efekti- smanjenje deponija i poboljšanje svojstava betona. Ideja ovog istraživanja je analiziranje mogućnosti recikliranja letećeg pepela iz termoelektrane tako što će delimično zameniti uobičajeni mineralni punioc- krečnjak u proizvodnji samozbijajućeg betona (SCC). Upoređena su svojstva konvencionalnog SCC sa krečnjakom i kompozicija sa različitim sadržajem pepela. S obzirom da je u slučaju dodatka letećeg pepela potrebno da budu zadovoljeni zahtevi za SCC, kao i da svojstva betona ostanu ista ili poboljšana, ova studija je pokazala da se sve dizajnirane smeše mogu koristiti za konstrukcijske primene.