Outstanding structural properties of secondary building materials

remexit® consists of a mixture of different aggregates such as concrete, bricks, clinker, gravel and sand. The original properties of each of the constituents of the construction and demolition rubble are retained after processing, which is why, from a technical point of view, recycled aggregates are comparable to primary building materials. The requirements to be met by our secondary building materials result from technical rules and regulations and the tender documents respectively.

Overview of rules and regulations for road construction and earthworks

The technical regulations pertaining to road construction and traffic are defined by the various committees of the German Road and Transportation Research Association (Forschungsgesellschaft für Straßen- und Verkehrswesen, short FGSV). They provide the recommendation for federal states, which generally adopt these standards. However, variations from state to state are possible, particularly in regard to substitute construction aggregates.

The following FGSV publications form the basis in Germany for the use of recycled aggregates in road construction and earthworks.

Regulations for secondary building materials such as recycled aggregates

Relevant technical regulations for secondary aggregates for use in road construction and earthworks

Road design according to RStO 12

When planning the road pavement structure, the Guidelines for the standardisation of pavement structures of traffic areas (Richtlinien für die Standardisierung des Oberbaus von Verkehrsfläche, short RStO 12) must be observed. The following figure is a simplified illustration of the road structure.

Depending on the construction method (asphalt, concrete, block pavement) and anticipated traffic load, the pavement structure will consist of two or three base courses of different thickness, but usually at least a frost blanket course and a crushed base or gravel base course, which can be bound or unbound. Underneath are the subgrade and the natural subsoil.

The FGSV regulations differentiate between load classes for road design. Each road is assigned to one of these classes as part of the planning, depending on the traffic load based on measured traffic volume. The load class affects, among other things, the type of construction and the structure of the road surface.

Subsoil, subgrade and pavement structure: Road design principle

Principles of a road pavement structure

Load classes influence applicability of recycled aggregates in according roads

Load classes for typical design situations

Seven load classes are distinguished according to RStO 12. Examples are given in the table "Load classes for typical design situations".

With the introduction of RStO 12, the previously valid construction classes of RStO 01 were changed to load classes. Since then, an assignment between old and new class is necessary to use the FGSV rules.

Specifications of aggregates

With regard to the technical requirements for aggregates for unbound layers such as frost blanket course and base course, TL Gestein-StB 04 and TL SoB-StB 04 or TL G SoB-StB 04 as well as ZTV SoB-StB 04 must be observed. In earthworks, the Technical delivery terms for soil and building materials TL BuB E-StB 09 and the Additional technical conditions of contract and directives ZTV E-StB 09 are particularly relevant.

In addition to geometric and physical properties proving suitability, these publications define the requirements for the material composition that recycled aggregates must meet.

Recycled aggregates and required material composition for road works

Requirements for material composition of recycled construction materials

Technical suitability of recycled aggregates

In accordance with the FGSV regulations, the use of quality-monitored remexit® recycled aggregates is generally possible in the following applications:

  • Unbound base courses (crushed base course, frost blanket course) in all load classes
  • Hydraulically bound base courses and hydraulic consolidation in all load classes
  • Bedding material under paving and slabs
  • Subgrade for roads
  • Subgrade under foundations/floor slabs
  • Other earthworks: Dam, backfill, embankment

The environmental specifications for the use of recycled aggregates must be observed. A complete overview of the resulting fields of application after comparison of technical and environmental specifications can be found here

Handbook on secondary aggregates

Detailed background on the use of substitute construction materials in road construction and earthworks with information on construction technology as well as environmental regulations can be found in a comprehensive compilation in our German secondary aggregates handbook. The 7th edition already contains the information that must be observed when the new directive for secondary aggregates "Ersatzbaustoffverordnung" comes into force on 1 August 2023.

Recycled aggregates: Requirements included in our handbook for use of secondary building materials