Abstract
The article presents the results of tests performed on fly ash with a high content of ammonium (up to 400 ppm) from the NOx reduction process. The main properties of fly ash were tested according to EN 450-1 and the results were compared with fly ash without ammonium. The comparison showed that fly ash with high concentration of ammonium suits the requirements of the European standard. Although the requirements do not limit the ammonium content, using such material as an additive for cement composites causes the emission of gaseous ammonium during mixing and from the final product. For this reason, the emission of ammonium from mortars containing fly ash were tested. The results have shown that using high ammonium fly ash might pollute indoor air and affect the health of users.
Highlights
Fly ash is a widely used by-product, no longer considered just a waste but a rather a valuable pozzolanic material added to cement composites to improve their properties [1,2,3,4,5,6,7].It is used in cement and concrete manufacturing after fulfilling the requirements of various standards such as EN 197-1, EN 450-1 and ASTM C618 [8,9,10,11]
Fly ashes with lower fineness had the highest concentration of ammonia, which suggests that fly ashes with smaller grains and higher surface might absorb higher amounts of ammonia
No correlation between the ammonia content and loss on ignition and the fineness of fly ash was found no significant effect of ammonia on mortar density and consistency was found no significant effect of ammonia on compressive strength and pozzolanic activity was found no significant influence of ammonia on water requirement was found intense release of ammonia gas was observed when the ash came into contact with a strongly alkaline cement grout, which might cause the observed increase of the air content in fresh mortar ammonia in fly ash increases the initial and final setting times of the grouts within the limits permitted by the PN-EN 450-1 standard [1]
Summary
Fly ash is a widely used by-product, no longer considered just a waste but a rather a valuable pozzolanic material added to cement composites to improve their properties [1,2,3,4,5,6,7]. It is used in cement and concrete manufacturing after fulfilling the requirements of various standards such as EN 197-1, EN 450-1 and ASTM C618 [8,9,10,11]. Both installations use a reducing agent, which is injected directly to the combustion chamber (in SNCR) or into the flue gas before entering the catalytic zone
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