Fly Ash in Building Materials

KEMA has expert knowledge to turn fly ash into building materials

Fly ash for high-grade concrete
Within the concrete industry, demand for uniformly fine-grained aggregate is growing fast. Using such aggregates, it is possible to make high-grade concretes that are twice or three times as strong as the conventional alternatives, and are also easier to work with. The most commonly used material is micro-silica. However, micro-silica is scarce; so it is not only expensive, but rising demand leads to shortages. Fly ash is very similar to micro-silica in terms of its composition and properties. Unfortunately, the particle size is too large. KEMA has developed a procedure for reducing the particle size of fly ash. Micronization by granular milling produces ‘ultra-fine fly ash’ show that concrete of strength class B105 or higher can be made using this ultra-fine fly ash aggregate.

Fly ash in bricks
Fly ash from the combustion of pulverized coal is a valuable raw material, widely used in the manufacture of building materials. Its use as an additive by the brick industry is opening up new disposal channels for power plant operators. However, fly ash is only suitable for this application if the leaching requirements laid down in the relevant environmental protection decree can be met. Furthermore, questions have arisen concerning the accuracy of the ‘decay factors’ worked out by the National Institute of Public Health and the Environment (RIVM). These factors are meant to define the relationship between behavior under laboratory conditions and behavior in the field. The BSB’s leaching requirements are based on the soil immission level over a period of a hundred years. KEMA applied this standardized laboratory test for a field test program the determining the leaching from five sections of a brick wall of which two sections contain 20 per cent fly ash by mass.

Radon from building materials
Radon is formed by the disintegration of radium, itself a radioactive decay product of uranium-238. It is found in all minerals and construction raw materials. Being gaseous, Radon is able to escape from solid materials. The radon concentration inside a building is attributable largely to gas emerging from the ground. The amount of radioactivity diffusing into the interior of a building over a given period of time is called the level of "exhalation". In line with the Dutch government’s Radon Policy Statement, KEMA has developed standards to regulate the radiological properties of building materials using fly ash as an aggregate. One of the properties to come under scrutiny is ‘radon exhalation’. It appears that the use of fly ash can reduce radon exhalation.