Sustainable Building Sourcebook
Chapter: Materials
 
Flyash Concrete
 
CSI Numbers: Division 3 - Concrete, 04230 Reinforced Unit Masonry, 03153 Prefabricated Forms
 
Introduction:
 

Flyash is the finely divided residue resulting from the combustion of ground or powdered coal, which is transported from the firebox through the boiler by flue gases. Flyash is a by-product of coal-fired electric generating plants.

There are two classifications of flyash, depending on the type of coal used. Anthracite and bituminous coal produces flyash classified as Class F. Class C flyash is produced by burning lignite or sub-bituminous coal. Class C flyash is the main type offered for residential applications from ready-mix suppliers.

Also see the Green Building Factsheets for introductions to this and other green building topics.
 
At-A-Glance Notes:
 
Technology:
Flyash used in concrete is a mature technology. On average, thirty percent of the flyash produced in the United States is recycled into concrete mixes. The use of flyash concrete in structural applications such as wall forms is standard technology.
 
Suppliers:
Sixty to seventy percent of central Texas ready-mix suppliers offer flyash concrete. Some suppliers provide it automatically, others give a choice. A survey of Austin ready-mix suppliers found that all suppliers surveyed substituted 18 percent to 24 percent flyash for cement automatically. A number of buyers request 30 percent or more substitution. Concrete masonry units (concrete block) are manufactured locally containing flyash.
 
Cost:
Flyash concrete is the same price as concrete without flyash.
 
Public Acceptance:
There is a small segment of the population that is fearful of flyash as being inferior or unhealthful. U.S. EPA information indicates there is not a health threat, especially in the portions found in ready-mix products and products made with western coal (which is the primary source of local flyash).
 
Regulatory:
Flyash concrete meets applicable codes. Products making use of flyash concrete must indicate having met applicable ASTM test requirements. This information will be provided by the supplier.
 
Considerations:
 

Flyash is a coal combustion byproduct. The use of this byproduct offers environmental advantages by diverting the material from the waste stream, reducing the energy investment in processing virgin materials, conserving virgin materials, and allaying pollution.

Thirteen million tons of coal ash are produced in Texas each year. Eleven percent of this ash is used, well below the national average of 30%. Over 60% of central Texas suppliers offer flyash in ready-mix products. A survey of ready-mix suppliers in Austin indicated that, on average, 18-23 percent of cement is automatically substituted for fly ash in the standard mixes. Customers who have specific requirements will specify from 0-40 percent substitution.

Although flyash offers environmental advantages, it also improves the performance and quality of concrete. Flyash affects the plastic properties of concrete by improving workability, reducing water demand, reducing segregation and bleeding, and lowering hydration heat. Flyash increases strength, reduces permeability, reduces corrosion of reinforcing steel, increases sulphate resistance, and reduces alkali-aggregate reaction. It reaches its maximum strength slower than concrete made with only Portland cement. The techniques for working with this type of concrete are standard for the industry and will not impact the budget of a job.

Flyash concrete may also be used for a finished floor. Coloring, scoring, and texturing techniques are very attractive and are becoming increasingly popular. Appearance is as conventional or unconventional as the designer creates.

 
Guidelines:
 

Specification for flyash

Flyash for use in Portland cement concrete shall conform to the requirements of ASTM C 618, Standard Specification for Flyash and Raw or Calcined Natural Pozzolan Class C Flyash for use as a Mineral Admixture in Portland cement concrete.

The concrete supplier shall furnish a notarized certificate from the flyash marketer at the time of submittal of concrete mix designs for approval indicating conformance with these requirements. Also, a copy of the most recent chemical analysis shall be provided.

At no time during the course of the project will a change of flyash source (plant) be permitted without the prior written consent of the Engineer or Architect.
For sulfate environments, only Class F flyash will be permitted and under no circumstances will Class C flyash be used.

Flyash use

Class F flyash will typically require the addition of a foaming agent and is approved only for limited use, such as in pavers. Class C flyash does not require an entraining or foaming agent.

Standard concrete procedures can be employed.

 
Resources:
 
Professional Assistance:

See "Structural Engineers" in Yellow Pages

Boral Material Technologies
Gary Shelton
45 N.E. Loop 410, Ste. 445
San Antonio, TX 78218
(800) 531-5841
www.boralmti.com
Flyash marketing company, wholesale

Ramone L. Carrasquillo, Ph.D., P.E.
Construction Materials Research Group
Pickle Research Center
10100 Burnet Rd., Bldg. 18B
Mail Code 79100
Austin, TX 78758
(512) 471-4585
Fly ash consulting and research

Center for Maximum Potential Building Systems
8604 FM 969
Austin, TX 78724
(512) 928-4786
www.cmpbs.org
Consulting and testing

Components/Materials/Systems:

See "Contractor's Equipment and Supplies, Concrete Additives, Concrete Construction Forms & Accessories, Concrete Contractors, Concrete Equipment and Supplies, Concrete - Ready Mixed, and Concrete Reinforcements", in Yellow Pages

Environmental Construction Technologies, Inc.
P.O. Box 631126
Houston, TX 77263
(713) 783-9638
(800) 628-5233
www.earthenergy.com
"Enviro-Bricks" system of interlocking, stackable, flyash bricks; units are sized and tinted to match standard clay bricks

Featherlite Building Products/Blocks
508 McNeil Rd.
Round Rock, TX
(512) 255-2573
Concrete block made with flyash

General Assistance:

Boral Material Technologies
Gary Shelton
45 N.E. Loop 410, Ste. 445
San Antonio, TX 78218
(800) 531-5843
www.boralmti.com
Flyash marketing company, wholesale

Cement and Concrete Promotion Council of Texas
6633 Highway 290 E., Ste. 204
Austin, TX 78723
(512) 451-5127
www.ccpc-texas.org

Federal Register
Friday, January 28, 1983
Part IV, Environmental Protection Agency
"Cement and Concrete Containing Fly Ash; Guideline for Federal Procurement"

JTM
Bill Getirman
(713) 240-4082
Flyash marketing company, wholesale

National Concrete Masonry Association
2302 Horse Pen Rd.
Herndon, VA 20171-3499
(703) 713-1900
www.ncma.org

Portland Cement Association
5420 Old Orchard Rd.
Skokie, IL 60077-1083
(847) 966-6200

State Dept. of Highways & Public Transportation
Department Materials Specification
D-9-8900 Fly Ash
Joe Raska
(512) 465-7469

Texas Coal Ash Utilization Group
Jacob Gonzales
TU Electric & Gas
1001 Bryan Street, Ste. 16090
Dallas, TX 75201-3411
(214) 812-8328
jake.gonzales@tuelectric.com