The Fly Ash Marketplace

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Utilization of coal combustion byproducts (CCBs) began with the utilization of fly ash. Fly ash was first used in the 1930's as a mineral filler in asphaltic mixes. In 1946, the Chicago Fly Ash Company (precursor to American Fly Ash Company) was formed by Harry Cain, Craig Cain and others. Its purpose was to market coal fly ash as a construction material for manufacturing concrete pipe. Commonwealth Edison Company requested help with its increasing fly ash disposal problems. Other markets were needed. Initial markets opened up by the Chicago Fly Ash Company were for fly ash as a cement replacement and as an enhancer of the qualities of concrete to meet the new postwar requirements. The Walter N. Handy Co. was formed in the 1950's in Springfield, MO to market fly ash.

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.

Fly ash is also being used in the concrete at the Freedom Tower at the World Trade center Site.

Fly is used in high strength concrete in Denmark.

Rockport Fly Ash (American Electric Power-AEP) was used in I-70 Reconstruction:
Approximately 14,000 tons of fly ash from AEP- Rockport Power Plant, located near Rockport, Indiana, was used as a pozzolan in the concrete poured for the reconstruction of I-70 in Clark County, Indiana. LaFarge North America, which is the fly ash marketer, is providing the technical and logistical support required for the project. Fly ash used as a pozzolan or partial replacement for cement in concrete, provides for:
* Higher Strength. Fly ash continues to combine with free lime, increasing structural strength over time.
* Decreased Permeability. Increased density and long term pozzolanic action of fly ash, which ties up free lime, results in fewer bleed channels and decreases permeability
* Increased Durability. Dense fly ash concrete helps keep aggressive compounds on the surface, where destructive action is lessened. Fly ash concrete is also more resistant to attack by sulfate, mild acid, soft (lime hungry) water, and seawater.
* Reduced Sulfate Attack. Fly ash ties up free lime that can combine with sulfate to create destructive expansion.
* Reduced Efflorescence. Fly ash chemically binds free lime and salts that can create efflorescence and dense concrete holds efflorescence producing compounds on the inside.
* Reduced Shrinkage. The largest contributor to drying shrinkage is water content. The lubricating action of fly ash reduces water content and drying shrinkage.
* Reduced Heat of Hydration. The pozzolanic reaction between fly ash and lime generates less heat, resulting in reduced thermal cracking when fly ash is used to replace portland cement.
* Reduced Alkali Silica Reactivity. Fly ash combines with alkalis from cement that might otherwise combine with silica from aggregates, causing destructive expansion.
* Workability. Concrete is easier to place with less effort, responding better to vibration to fill forms more completely.

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.)

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.

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.

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.
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.

It is a pozzolan in grout for pressure grouting of concrete highways (slabjacking or undersealing) ; and in grout 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 grout site:tdot.state.tn.us/ Iowa also calls for fly ash- cement grout.In Google search for: cement fly ash grout site:dot.state.ia.us/ See the FHWA for information on this.

It is used in mining mortars in such applications as rock stabilization or filling of cavities.

It is used in embankments and backfills (as engineered construction material or structural fills).

It is used in Soil Stabilization both to dry the soil and reduce its plasticity. See the FHWA for information on this.

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.

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.

It is used as a Portland cement raw material, and in fly ash blended cements, etc.

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.

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.

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.

Fly Ash Bricks with Class C fly ash.

It can be used in industrial ceramics.

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.)

It is used to stabilize industrial wastes.

It is used along with bottom ash as a growing media for plants.

Turner-Fairbank Highway Research Center-FHWA-US DOT. Refer to this guideline to use coal ash in a variety of ways.

Fly Ash Concrete-Friendly to the Environment

Fly Ash in Self-Leveling Flooring

Fly Ash Movie-Headwaters Resources

Fly Ash Brick Technology

Fly Ash Soil- Sement

Boiler slag, a coarse, glassy, non-porous, black, and angular material obtained from the bottom of the slag-tap or cyclone wet-bottom boiler, is used as an antiskid material for roads during winter and as a coarse blasting grit in the abrasives industry, and as asphalt shingle roofing granules. The slag-tap boiler burns pulverized coal and produces 50% slag and 50% fly ash. The cyclone boiler burns crushed coal and produces 70-80% slag and 20-30% fly ash. A new application for boiler slag is water-jet cutting. It is also used as a road drainage medium and as a filtering medium. It has low bulk density, high shear strength, good drainage and filtering characteristics.

Bottom ash , a coarse, porous, sandy, gray-brown lightweight material from the bottom of the dry-bottom boiler (burning pulverized coal), is used as structural fill material, as roadbase with fly ash, as antiskid material for roads, and as a lighterweight aggregate in concrete block. Bottom ash should be free of carbonaceous material (which is not mechanically stable) and pyrites to avoid discoloration of the concrete block.

RiverCity is an example where a high cost material,Portland cement, can be replaced at some percentage by a low cost material, fly ash. For example, all concrete in place has a structural function. The concrete that defines the shapes of the rooms also provides the building's structural support. Each S-shaped building is created by a series of vertical concrete tubes (or pods) spaced at intervals along an S-shaped line made from two semicircles. 22 different types of apartment shapes are created by the tube's curvilinear layout and from ways spaces enclosed by the tubes are combined with spaces between tubes.

The recycling of CCB's meets society's concerns for conservation of limited resources and saving landfill space. This creates a demand for fly ash testing, quality control programs, and fly ash marketers.

MARKETERS

Topeka, Kansas USA