Aardelite® Aggregate Information
Aardelite (“light earth” - named by the Dutch company that patented the basic chemistry) is a material comprised of about 95% fly ash plus quicklime and water. The most useful form produced is small pellets which are an ideal aggregate for producing light to medium weight concrete masonry units (“concrete blocks”) or easily finished concrete shapes.
Major advantages of Aardelite aggregate include:
|Above: Aardelite Production Facility|
Crystal River, FL
- The spherical shape of the fly ash pellets result in an improved workability of the concrete, requiring less vibration energy for shaping and compacting.
- Lower specific density of the fly ash pellets results in savings when used in building materials, especially where weight is a critical aspect as in foundations, building elements, transportation costs or handling of the building products.
- Final size distribution of the product can be tailored to meet the customer`s requirements at the same production cost.
|Above: Over 1.7 million tons of aggregate have been produced since 1988|
The Aardelite process is a cold-bonding process which uses fly ash (including high LOI fly ash), quicklime and water and operates at atmospheric pressure and a maximum temperature of about 85 C. The process is based on the hardening of a fly ash/lime mixture due to reaction of calcium oxide with water and the resulting slurry with silica, and alumina which are already available in the fly ash. During these reactions, calcium silicate/aluminate minerals are formed through a reaction mechanism similar to that of Portland cement. These minerals bind the fly ash particles tightly, resulting in strong, hard pellets.
Major advantages of the Aardelite process are:
- It has a low energy consumption because of its +/-85 C curing temperature.
- There are no solid, liquid or gaseous emissions from the process other than modest quantities of dust generated during processing and handling which are collected in dust filters and recycled.
- Compared to the sintering process, the investment and production costs are relatively low.
- The process can be operated by average semi-skilled personnel and does not require complicated upkeep.
PMI Development and Operations
PMI was instrumental in the commercialization of the Aardelite process, licensing the basic chemistry from the Dutch developers and developing the process from lab-scale and batch mode pilot plant to the full scale, continuous mode, first commercial unit of its kind at the Crystal River power plant in 1988. Since startup in 1988 this plant produced in excess of 1,700,000 tons of high-quality aggregate, thereby providing the ash producer, Progress Energy Florida, with an ash utilization rate exceeding 85 percent, compared with a 25 percent average rate for U.S. coal-fired power plants. PMI also assisted with design and start-up of the second Aardelite plant in Holland and the design of another in India as well as several design studies in various countries.