Fly Ash Sales & Marketing

Benefits of Low Carbon Fly Ash

• Fly ash substantially increases concrete’s resistance to chemical reactivity which causes accelerated deterioration of concrete bridges, roads, dams and buildings.

Chloride Ion penetration leads to corrosion of reinforced concrete and is the single most costly deterioration mechanism facing state highway agencies in the United States, Canada and elsewhere. Corrosion of the reinforcing steel members leads to stressing and breaking of the surrounding concrete. Fly ash decreases the permeability of concrete and significantly inhibits the penetration of moisture and chloride ions from de-icing salts and from marine environments.

Alkaline Aggregate Reaction (AAR) is a chemical reaction – which fly ash can prevent – which occurs between the free lime in Portland cement and certain aggregates in concrete. When exposed to the free lime in the presence of moisture, components of the aggregate turn to a gel and cause the aggregate itself to expand. When this occurs, the concrete begins to crack, admitting more moisture which fuels the reaction, leading to the ultimate failure of the structure. Fly ash prevents this reaction by selectively reacting with the free lime without forming expansive products.

• Fly ash provides increased ultimate strength to concrete applications. After 28 days of curing, the compressive strength of concrete with fly ash is greater than that of ordinary concrete. This advantage grows over time as the curing process continues. Fly ash is also a key ingredient in High Performance Concrete (HPC) which is becoming increasingly used in key structural applications.

• Fly ash lowers the heat of hydration by slowing down the heat-generating reaction as compared with the fast-reacting Portland cement. This allows the curing structure to dissipate the heat safely without producing thermal stress cracks.

• Fly ash allows greater flowability of the concrete mix, allowing less water utilization and greater pumping flexibility.

• Fly ash improves water tightness in concrete because the fly ash chemically combines with and stabilizes the water soluble calcium hydroxide in concrete. Fly ash concrete is 5 – 13 times more impermeable to water penetration than a comparable Portland cement. This added impermeability also resists chemical reactivity described above.

• Fly ash concrete requires less water in the mix than ordinary concrete, resulting in less segregation, less likelihood of cracking and an ability to be poured in colder weather. In addition, the requirement for water adsorption additives is reduced and there is a reduction in the heat of hydration.

• Fly ash reduces drying shrinkage in concrete. Water and Portland are the main contributors to drying shrinkage in concrete. By replacing a portion of the Portland and requiring less water in the mix, the shrinkage problem is lessened.

• Fly ash reduces CO2 emissions by replacing Portland cement. The production of Portland powder is extremely CO2 intensive and the replacement of one ton of Portland by fly ash results in the avoidance of one ton of CO2.

• Fly ash utilization results in energy conservation. The production of Portland cement requires a large amount of energy – one barrel of oil or 1/3 ton of coal to produce one ton of cement. Avoiding that energy cost through use of fly ash results in enough energy saving to provide electrical energy to an average American home for 24 days.

• Fly ash utilization improves land conservation by avoiding landfill. One ton of fly ash uses the same amount of landfill space as the solid waste produced by an average American in 455 days.