Architects and Engineers
Architects and Engineers
Increased durability, lower permeability, higher ultimate strength, reduced alkali-silica reactivity, better for the environment each describes concrete products designed with ProAsh®.
Concrete produced with ProAsh® allows specifiers and contractors the opportunity to use a product that is the backbone of green building.
ProAsh® replaces cement in the concrete mix design by reducing the amount of cement needed this ultimately reduces CO2 emissions – when cement is manufactured, 1 ton of CO2 is produced for every ton of cement.
ProAsh® also reduces the amount of waste being sent to landfills. Fly ash not used in concrete or other beneficial ways is disposed of in landfills and collection ponds across the country.
In addition, products with ProAsh® have both a lower initial cost and lower ultimate cost due to the reduced need for repairs and replacement.
- A powder by-product from the combustion of pulverized coal in electric power generating plants. Fly ash is a pozzolan. A pozzolan is a siliceous or alumino-siliceous material that in itself possesses little or no cementitious value. But in the presence of water, it will chemically react with the calcium hydroxide released by the hydration of portland cement to form compounds possessing cementitious properties.
Primarily a silicate glass, spherical in shape
- Particle size
- Range: < 1 to > 100 microns
- Average Particle Size < 20 microns
- Specific gravity ranges from 2.2 to 2.8
- Unburned carbon content Loss of Ignition(LOI). LOI is a measure of the unburned carbon (coal) remaining in the ash.
- Separated from the flue gases by means of electrostatic precipitators, hence the term fly ash as the ash that flies away in the gas stream.
- Used as a supplementary cementitious material in concrete.
How Fly Ash Works
C3S + H2O = CSH + CH Binder Lime By-Product
CH + SiO2 = CSH
Bottom line: Produces MORE GLUE
Type of Fly Ash
- anthracite & bituminous coal
- CaO typically less than 10%
- variable LOI
- lignite & sub-bituminous coal
- CaO greater than 10% (avg. 24%)
- low LOI
- Separation Technologies technical marketing expertise is industry-leading. Our concrete industry customers draw on our in-house sales staff for advice and assistance on admixture chemistry, cement chemistry, and concrete chemistry, and on mix optimization.
There are multiple ways sulfate attack can occur. First, sulfates react with the calcium hydroxide from the free lime in the cement to form calcium sulfate (gypsum). Second, the aluminates in cement react with sulfates and calcium to form ettringite. Both the gypsum and ettringite are expansive compounds that cause fractures in the concrete.
ProAsh® reduces the sulfate attack in the following ways:
- ProAsh® reacts with the free lime in the cement to form more cementitious material and reduces the risk of free lime reacting with sulfates.
- ProAsh® reduces the permeability of the concrete and reduces the penetration of the sulfates.
- Additional ProAsh® translates to less cement and results in fewer aluminates for sulfate attack.
The reduction in permeability is related to the particle size and shape of fly ash. ProAsh®, when introduced to the concrete mix, actually fills voids within the concrete matrix and lowers the permeability of the material. One test for permeability is the rapid Chloride Permeability test. The test involves measuring a small electric current through a cured concrete cylinder that has been stored in a saltwater bath.
There are multiple success stories involving ProAsh® and sulfate remediation, including the two Highway 90 bridges in Biloxi, MS, and the I-10 bridge in New Orleans, destroyed during Hurricane Katrina and since rebuilt using 20% ProAsh®.