HIGH VOLUME FLY ASH CONCRETE AND ITS DURABILITY IN AGGRESSIVE ENVIRONMENT

miscellaneous

English

In the paper are presented results from research focused on high volume fly ash concrete (HVFAC). Three concrete mixtures were designed to reach concrete strength classes C16/20, C25/30 and C40/50 (conforming to EN 260-1). Four modifications of each mixture were prepared where 0 %, 40 %, 50 % and 60 % of cement (CEM I 42,5 R) were replaced by fly ash (brown coal fly ash from thermal power plant Opatovice). Concrete samples were tested for compressive strength in age 7, 28, 60, 90 and 180 days, resistance to SO42- and resistance to NO3- were tested too. Samples for testing resistivity to aggressive environment were stored in water for 28 days and then placed into aggressive solutions for 60 days. Compressive strength of these samples was compared with compressive strength of samples stored for 90 days in water. As pretended, the increasing of compressive strength of concrete without fly ash almost stopped after 28 days of curing. HVFAC had the biggest step in compressive strength increasing between 90th day and 180th day. The best results of resistivity to aggressive environment reached concrete mixture C16/20. Samples exposed to aggressive environment reached higher compressive strength than samples placed in water. Mostly NO3- solution seems less aggressive than SO42- solution. It can be seen that higher dosage of fly ash influences positively resistance to NO3- and negatively resistance to SO42-.

Fly ash, high volume fly ash concrete, durability

ORSÁKOVÁ, D.; HELA, R.

15. 10. 2014

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