R.E. Davis did the first comprehensive study of fly ash in concrete in 1937 at the University of California. The first major use of coal fly ash was by the U.S. Bureau of Reclamation (BOR) in the repair of the tunnel spillway at the Hoover Dam in 1942 followed by the concrete construction of the Hungry Horse Dam near Glacier National Park in Montana in 1948-52. Six other dams were constructed during the 1950s using coal fly ash concrete. Thirty dams were constructed in the 1960's. The second largest coal fly ash market during this time period was the cementing of oil wells. 

Today fly ash, a finely-divided spherical material collected from the flue gases by electrostatic precipitators is used in a number of applications. Some examples of the use of fly ash are: Water Tower Place in Chicago, the Eisenhower Expressway in Chicago, the Dunsmuir Tunnel in Vancouver, Picasso Tower in Madrid, the Commerzbank Tower in Frankfurt, Puylaurent Dam in France, the Channel Tunnel between France and United Kingdom, the Underground railway tunnel in Vienna, in the East Bridge in Copenhagen, and the Eindhoven Airport landing strip in the Netherlands. Recently, Fly ash was used in the reconstruction of historic Wacker Drive in the City of Chicago, IL USA. This high-performance concrete contained (lb/yd3): 525 of portland cement, 52.5 Class F fly ash, 26.25 silica fume, and 78.8 ground granulated blast furnace slag.

High performance concrete is used in the construction of the world's tallest building (Burj Dubai) in Dubai, United Arab Emirates (kg/m3): 990 fine aggregate, 810 coarse aggregate, 350 Portland cement, 120 Class F fly ash (probably exported from India), 30 Microsilica, 135 water and superplasticizer.

Power plant fly ash and bottom ash from coal burning is typically reused in China. Some power plants are able to dispose of nearly all of the ash and other solid wastes through sale to recyclers and reusers. China does considerable work in fly ash research and utilization. Use this as a search term to get web pages in both English and Chinese:" 粉煤灰 AND fly ash ".

One of the 'Green' buildings on the University of British Columbia campus is the Liu Centre for Global Issues. It was the first Canadian non-industrial building to use a high-volume fly ash concrete mix. ParkLane Development in Halifax, Nova Scotia is an example of high-volume fly ash concrete. 55% of the cementitious mix was fly ash. Think of the savings in energy and to the environment (less global warming.)

1. It is a pozzolan in highway pavement concrete, structural concrete, Roller Compacted Concrete (RCC), concrete products like pipe and autoclaved aerated concrete.  Fly ash in RCC may exceed cement content and is often used in large dams; these dry mixes must be compacted in place. Fly ash is also used in self-compacting concrete (SCC), which was developed because of the lack of uniformity and incomplete compaction of concrete by vibration during construction. Self-compacting concrete might contain: 174kg water, 408kg cement, 45 kg fly ash, 1052kg fine aggregate, 616kg coarse aggregate and a high-range water reducer and viscosity-modifying admixture. See the FHWA and EFNARC.
2. It can be used up to 50 % of total cementitious material in high pressure steam-cured block and as a 20-30% replacement in low pressure steam-cured block where it provides strength and plasticity to the relatively harsh block mixes.
3. India has a huge housing shortage that can be helped by the use of recycled byproducts such as fly ash. Cellular Light-Weight Concrete (CLC) blocks are a substitute to bricks and conventional concrete blocks with densities varying from 800 kg/m3 to 1800 kg/m3. The normal constituents of this Foaming Agent-based technology from Germany are: cement, Fly Ash (to the extent 1/4th to 1/3rd of total materials constituent), sand, water and foam (generated from biodegradable foaming agent). CLC walling & roofing panels can also be produced. Foaming agent and the Foam generator, if used for production of CLC with over 25% fly ash content invites concession on import duty by Govt. of India.

4. It is used as a mineral filler in asphaltic roads to minimize void content and increase the stability of bituminous wearing courses. Use of fly ash rather than ground limestone has proved itself. See the FHWA for information on this.
5. It is a pozzolan in grouts for pressure grouting of concrete highways (slabjacking or under-slab grouting); and in grouts for other purposes such as tunnel linings, sewer relining, and abandoned sewer and mineshafts. Pavement Undersealing: Tennessee allows for cement-fly ash grouting to underseal pavements. (The mix design is 1 part Portland cement to 3 parts fly ash by volume.) Use this as a search term in Google: cement fly ash grouting site:tdot.state.tn.us/ Iowa also calls for fly ash- cement grouts.In Google search for: cement fly ash grouting site:dot.state.ia.us/ See the FHWA for information on this.
6. It is used in mining mortars in such applications as rock stabilization or filling of cavities.
7. It is used in embankments and backfills (as engineered construction material or structural fills).
8. It is used in Soil Stabilization both to dry the soil and reduce its plasticity. See the FHWA for information on this.
9. It is used in Road Base. These dry compacted mixtures ,containing portland cement (CFA)or lime (LFA), are used in sub-base and base courses. Bearing strength and durability are improved as compared to conventional natural aggregate.
10. It is used in stabilized backfills (flowable fills).Flowable fills, which are also called controlled low strength materials (CLSM), were evaluated at the Wisconsin DOT using (lb/yd3): 2500 foundry sand, 400 Class C fly ash, 50 cement and 700 water. Use this in your search term in Google: fly ash site:dot.wisconsin.gov/ See the FHWA for information on this. The San Francisco Bay Area Rapid Transit District (BART) specifies fly ash in controlled density fills. The 28 day strength is 50-150 psi.
11. It is used as a Portland cement raw material, and in fly ash blended cements, etc. 
12. It is used as a lightweight synthetic aggregate in block and concrete. Pellets are formed on a rotating disk and then sintered in an oven. Aardelite has a production process that involves thorough mixing of raw materials such as fly ash, lime, water, and some additives such as gypsum. The mix is pelletized and cured in an autoclave. 
13. It is used as an industrial mineral filler. The hollow spheres in fly ash,cenospheres , are used in plastics, paints, varnishes and in refractory applications like the U.S. Space Shuttle's heat shield.
14. In Germany, it is an ingredient in sand-lime bricks. These are produced using boiler slag, fly ash, lime and water. These bricks are pressed into a brick mold and autoclaved at 190 Celcius.
15. It can be used in industrial ceramics.
16. Tiger Mountain Innovations produces a Squak Mountain Stone for countertops and tiles. This stone is made from cement, waste paper fiber, pulp, granite dust and fly ash (contact Amee Quiriconi in Issaquah, WA USA.)
17. It is used to stabilize industrial wastes.
18. It is used along with bottom ash as a growing media for plants.
19. Turner-Fairbank Highway Research Center-FHWA-US DOT. Refer to this guideline to use coal ash in a variety of ways.