How Are Our Products Produced?
Ash Grove Resources, L.L.C. supplies Class C Fly Ash and Ash Grove Durabase® (Cement Kiln Dust-CKD) to the construction industry. In this section, we will explain how these products are produced.
Coal-fired power plants produce Fly Ash as a by-product of the combustion process. The Fly Ash consists of the inorganic matter present in the coal that has been fused (melted) during the combustion of the coal, solidified while suspended in the exhaust gases and collected from the combustion air-stream as it exits the power plant. It is made up of minute glassy particles that are generally spherical in shape, usually smaller than 50 microns in size. Fly Ash is then stored in silos until shipped for a wide variety of applications.
Fly Ash is a pozzolan. Pozzolanic materials have the ability to form cementitious substances when mixed with lime (Ca(OH)2) and water (H2O). The hydration reactions are similar to the reactions occurring during the hydration of Portland cement. Romans used Volcanic Ash (natural pozzolan) and lime as a mortar during the construction of Rome and other cities. Many of their structures - which used the Volcanic Ash and lime as a mortar or hydraulic cement - still exist today. One of the most well known is the Coliseum.
Ashes produced during the combustion of coal are artificial pozzolans. In the United States today, more than 40 million tons of useable pozzolans are produced annually. A major use of these pozzolans (Fly Ash) in the construction industry is stabilization of soils and pavement base courses as well as a concrete admixture.
Types of Fly Ash
Fly Ash is classified by its chemical make up. ASTM C618 Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan has two designations for Fly Ash, Class C Fly Ash and Class F Fly Ash.
In the 1970's, many electric generating units were converted to Powder River Basin (sub-bituminous) coals. The Ash produced from these coals is classified as Class C Fly Ash. It quickly became evident that this Ash had self-cementing properties that were well suited to a variety of soil stabilization applications. Upon exposure to water, Class C Fly Ash produces cementitious products without the need of an activator.
Class C Fly Ashes have high concentrations of calcium compounds which provide self-cementing properties. The self-cementing ashes (Class C) are produced in power plants that utilize sub-bituminous coal. The self-cementing properties of the Class C Fly Ash are especially useful in soil stabilization applications because it does not require an additive to achieve the desired results. Thus, Class C Fly Ash is a hydraulic, cementitious material that has pozzolanic properties.
Power plants that utilize bituminous or anthracite coals produce a Class F Fly Ash that is low in lime and does not have self-cementing properties. Class F Fly Ash primarily consists of silica, aluminia and iron compounds. The addition of an activator such as lime is required to produce cementitious products through a pozzolanic reaction.
|Fly Ash Class|
|Compounds||Class F||Class C|
Ash Grove Durabase®
Ash Grove Durabase® (CKD) is similar in composition and hydration characteristics to Class C Fly Ash yet is produced through a totally different process. Ash Grove Durabase® is a partially calcined mineral mixture collected from the exhaust gases of Portland cement kilns. As with Fly Ash, Ash Grove Durabase® is collected from the exhaust gases by electrostatic precipitators.
Ash Grove Durabase® is not suitable for use as a concrete admixture. Ash Grove Durabase® is used solely for the following applications:
- Soil stabilization or modification.
- In asphalt paving as an anti-stripping agent or a mineral filler.
- Stabilization in oil/gas well pits.
- Solidification of sludge and waste materials.
The quantity of Ash Grove Durabase® required varies by soil type and degree of stabilization required. Generally, every project site's materials must be sampled and tested to determine the optimum Ash Grove Durabase® content.
The properties of cement kiln dust (CKD) are being studied more thoroughly and intently by the cement industry as the applications for the Ash Grove Durabase® product expand. As the results of field applications become available, more effective applications are being developed.
Ash Grove Durabase® provides solutions for our customers. It helps fulfill Ash Grove Cement Company's commitment to sustainable development. Ash Grove Durabase® does this by incorporating recycled materials into a valued product line.
|Compounds||Long or Wet Kiln||Pre-Calcined|