Control of ammonia emission from ammonia laden fly ash in concrete

A method for reducing ammonia gas evolution from cementitious slurries when ammonia-laden fly ash is added to the slurry, comprising the steps:

• a) determining the concentration of ammonia in said ammonia-laden fly ash;
• b) blending a desired quantity of an oxidizer with said ammonia-laden fly ash;
• c) mixing said oxidizer and ammonia-laden fly ash mixture with said cementitious slurry at a pH of about 12 to about 14;
• and
• d) depositing said mixed slurry for curing.

A rapid screening test procedure for determining the content of ammonia in ammonia-laden fly ash, including the following steps:

• a) collecting a representative dry sample of said ammonia-laden fly ash according to ASTM C702;
• b) placing 100 ml of water in a clean 1000 ml flask;
• c) weighing out 25 g of said ammonia-laden fly ash and adding said fly ash to said water while stirring on a stir plate in said flask;
• d) closing said flask and allowing said water and said fly ash to stir for 1 minute;
• e) opening said flask and adding 10 ml of 1 N sodium hydroxide and immediate stoppering the flask;
• allowing said water, fly ash and said sodium hydroxide to stir for 1 minute;
• testing the pH of said water and said fly ash;
• and, if needed, adding more sodium hydroxide to bring the pH to 12;
• f) preparing the ammonia detector tube for testing;
• g) inserting said detector tube into a hand pump;
• h) inserting said detector tube into a stopper hold, into said flask;
• i) extracting a gas sample through said detector tube via said hand pump;
• and
• j) reading the entire length of the discoloration immediately.