Expanded clay was removed during roof renovations of a commercial building in Helsinki, and then used, after further processing, as roof soil for green roofs.

“In roof renovations, the old roof is dismantled and a layer of expanded clay, on average 400 mm thick and acting as heat insulation, is removed and delivered as a raw material for use in roof soil. A vapour barrier is installed onto hollow-core slabs, as well as expanded clay and 250 mm mineral wool. Expanded clay ensures adequate ventilation of the roof and it is convenient to carry out inclinations leading to roof drains,” says Lasse Ruuskanen from Eristysmestarit Oy, supervisor for the renovation of a commercial building located in Herttoniemi, Helsinki. expanded clay is removed from the roof and transported away by Anpe Oy.

Of recycled expanded clay, about 80 percent is used for geotechnical uses and 20 percent for other uses. For example, the processing value of expanded clay and soil in the manufacturing of roof soil for special use will rise with no generation of waste,” says Hannu Pesola, ANPE Oy’s managing director.

Pesola reminds us that expanded clay’s combined good properties, namely light weight, compressive strength and good thermal insulation properties are retained, even when the product is re-used.

“By taking advantage of expanded clay removed from roofs in geotechnical or other applications, one can reduce the need for new light aggregates in such applications, whereupon the capacity of a lightweight aggregate plant will improve and materials and the environment will be saved”.

Expanded clay was removed from a roof and delivered to Ralf Ajalin Oy’s Pihamaa service and soil station in Vantaa.

The aggregate was crushed and used as an important part in the manufacture of roof soil. Compared to normal soil, roof soil as a product has been processed for longer and is a more valuable specialty product,” says Olli Mannerjoki, from Ralf Ajalin Oy, responsible for Pihamaa-service products.

Expanded clay allows the soil to be much lighter, so that roof structures are not placed under excess loads. The main tasks of expanded clay aggregate in roof soil are to make the soil light, as well as to improve the movement of water in the growth base, which facilitates access to water for plants”.

During concrete block production inevitably sub-standard products are produced resulting from raw material, machinery or human inconsistencies. Typically in the large scale production of concrete building blocks approximately 0.5% of concrete produced becomes unsuitable for sale and is removed from the production line for reprocessing.

Sub-standard products are accumulated on site over a period of months until significant quantities are available at which stage crushing and sieving equipment is used to crush down the product to a suitable size and grade of raw material.

It is not possible to reprocess the sub-standard products back to the properties and grades which were used in the original concrete mix as the material produced from reprocessing will ultimately comprise expanded clay aggregate, sands and cements. Reprocessing produces a grade of material which comprises a homogeneous mix of the original recipe. From this process a new grade and specification of raw material is produced; to utilise this material a new concrete mix is designed to include the physical characteristics of the reprocessed material.