Re-thinking: using secondary materials where possible

As a rule, current regulations pertaining to road construction and earthworks will mostly require that only natural aggregates be used. And alternatives are unlikely to be explored. However, in those countries where regulations pertaining to the use of secondary aggregates exist, their use in construction has proven to be as safe as, and more economic than, conventional construction with primary aggregates.

Main application in road construction

The following graphics explain the general set-up of a road. The cross section on the left explains the principle of a flexible, flexible composite or rigid composite pavement, for example when constructing with asphalt as a wearing course. The other picture demonstrates the elements and layers of a concrete pavement.

Flexible, flexible composite & rigid composite pavement

Rigid pavement

 

In many countries, the technical guidelines for secondary aggregates, especially incinerator bottom ash, permit the use of GRANOVA in the following earthworks and road applications:

  • embankments and fill
  • subgrade
  • capping
  • unbound mixtures for subbase and base
  • hydraulically bound mixtures for subbase and base

The final decision on the use of IBA has to take into account the local environmental conditions.  

Application examples for road construction

Incinerator bottom ash is mostly used in construction projects requiring significant aggregate volumes with continuously high quality.The reference projects below were implemented using 250,000 and 100,000 tonnes of IBA respectively. 

Reference A 61Reference L 585n

Special earthworks: noise or sight barriers

Apart from earthworks needed for roads, there are other constructions requiring significant amounts of mineral material. Traffic, for example, has significant adverse effects on humans and the environment – e.g. in the form of exhaust emissions, fine dust and noise. Accordingly, sight and/or noise protection is needed and embankments along roads can be alternatives to other kinds of barriers such as embankments. Similarly, significant amounts of material are often needed for landscaping or backfilling.

The financial capacity of local authorities often restricts the carrying out of such projects. It is especially here that secondary aggregates form a feasible alternative.