Treatment of fly ash for use in concrete
View Patent ↗A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with a quantity of spray dryer ash (SDA) and water to initiate a geopolymerization reaction and form a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 40%, and in some cases less than 20%, of the foam index of the untreated fly ash. An optional alkaline activator may be mixed with the fly ash and SDA to facilitate the geopolymerization reaction. The alkaline activator may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.
1. A process of treating fly ash for use as a cement additive for use in concrete comprising:
obtaining a quantity of fly ash that contains between 0.1 and 50% carbon, by weight, based upon loss on ignition and which is considered unusable fly ash for concrete based upon foam index testing; and
mixing the fly ash with a sufficient quantity of spray dryer ash and water to initiate a geopolymerization reaction and form a geopolymerized fly ash, wherein the spray dryer ash contains an unreacted flue gas desulfurization sorbent, wherein the geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing.
2. The process according to claim 1 , wherein the flue gas desulfurization sorbent is selected from the group consisting of sodium sesquicarbonate, hydrated lime, and sodium carbonate.
3. The process according to claim 1 , further comprising the step of mixing an alkaline activator with the fly ash and spray dryer ash.
4. The process according to claim 3 , wherein the alkaline activator is selected from the group consisting of a metal carbonate, a metal silicate, a metal aluminate, a metal sulfate, a metal hydroxide, and mixtures thereof.
5. The process according to claim 3 , wherein the alkaline activator comprises a metal hydroxide.
6. The process according to claim 1 , wherein the ratio of spray dryer ash to fly ash is between 1:5 and 5:1.
7. The process according to claim 1 , wherein the ratio of spray dryer ash to fly ash is between 1:3 and 3:1.
8. The process according to claim 1 , further comprising the step of granulating the geopolymerized fly ash.
9. The process according to claim 8 , wherein the geopolymerized fly ash is granulated by spray drying.
10. The process according to claim 9 , wherein the geopolymerized fly ash is heated to a temperature between 20 and 250° C.
11. The process according to claim 9 wherein the geopolymerized fly ash is heated to a temperature between 20 and 150° C.
12. The process according to claim 8 , wherein the geopolymerized fly ash is granulated by crushing.
13. The process according to claim 8 , wherein the granulated, geopolymerized fly ash has a mean particle size between 0.1 and 1000 microns.
14. The process according to claim 8 , wherein the granulated, geopolymerized fly ash has a mean particle size between 10 and 100 microns.
15. The process according, to claim 1 , further comprising the step of adding the geopolymerized fly ash in wet form directly to a concrete mixture.
16. The process according to claim 1 , wherein the geopolymerized fly ash is considered premium grade for concrete based upon foam index testing.
17. The process according to claim 1 , wherein the geopolymerized fly ash is considered standard grade for concrete based upon foam index testing.
18. The process according to claim 1 , wherein the geopolymerized fly ash has a foam index less than 40% of the foam index of the untreated fly ash.
19. The process according to claim 1 , wherein the geopolymerized fly ash has a foam index less than 20% of the loam index of the untreated fly ash.
20. The process according to claim 1 , wherein the fly ash contains one or more heavy metals.
21. The process according to claim 1 , further comprising the step of mixing the granulated and geopolymerized fly ash with a second quantity of spray dryer ash and water sufficient to initiate a second geopolymerization reaction and form a second geopolymerized fly ash.
22. A process of treating fly ash comprising:
obtaining a quantity of fly ash that contains unwanted metals or heavy metals: and
mixing the fly ash with a sufficient quantity of spray dryer ash and water to initiate a geopolymerization reaction and form a geopolymerized fly ash, wherein the spray dryer ash contains an unreacted flue gas desulfurization sorbent selected from sodium sesquicarbonate, hydrated lime, and sodium carbonate, wherein the unwanted metals or heavy metals are entrapped within the geopolymerized fly ash to inhibit leaching into the environment.
23. The process according to claim 22 , further comprising the step of mixing an alkaline activator with the fly ash and spray dryer ash.
24. The process according to claim 1 , wherein the alkaline activator comprises a metal carbonate, alone or in combination with a metal hydroxide.
25. The process according to claim 1 , wherein the alkaline activator comprises a metal hydroxide, alone or in combination with a metal carbonate.
26. The process according to claim 23 , wherein the alkaline activator comprises a metal carbonate, alone or in combination with a metal hydroxide.
27. The process according, to claim 23 , wherein the alkaline activator comprises a metal hydroxide, alone or in combination with a metal carbonate.