Tar residues occur in construction more often than it first appears: in old joint compounds, in waterproofing, beneath floor coverings, or in tar-containing asphalt. In concrete demolition, in special demolition and in building gutting, professional handling of such residues determines occupational safety, emission control, disposal and efficiency. Choosing low-emission, hydraulic methods and the selective separation of construction materials – for example by concrete pulverizers or rock and concrete splitters from Darda GmbH – supports a clean, controlled approach without unnecessary thermal loads.
Definition: What is meant by tar residue
Tar residue is the remaining fraction of tar-containing substances from the use of coal tar, tar pitch or tar-containing mixtures. Typical are dark brown to black, sticky or brittle materials with a characteristic odor. Tar residues can exhibit high levels of polycyclic aromatic hydrocarbons (PAHs) and other accompanying substances. They are to be distinguished from bitumen-containing products that are petroleum-based and generally have different properties and risks. Tar residues are found mainly in existing buildings of older vintages and in traffic areas with tar-containing layers.
Origin and typical occurrences of tar residues in construction
Tar-containing substances were widely used in the past. Therefore, tar residues can occur in different structural components:
- Joint sealants and expansion joints on concrete pavements, bridges and parking structures
- Waterproofing in basements, foundation elements, upstands and plinth areas
- Roofing membranes from older years, bondings and penetrations
- Adhesives beneath floor coverings (e.g., under parquet, wood block flooring, slab coverings)
- Tar-containing asphalt and binder layers in traffic areas and halls
- Joint compounds in sewers, channels and technical structures
Time frame and building age
Particularly relevant is the stock up to the 1970s/1980s, when tar-containing products were widespread in building and infrastructure construction. A reliable classification, however, is only possible through appropriate investigations.
Material composites
Tar residues frequently occur as a composite with concrete, masonry, screed, asphalt or metal parts. For deconstruction, selective separation of these composites is crucial in order to capture contaminated portions in a targeted manner.
Tar or bitumen: reliable differentiation
The distinction between tar- and bitumen-containing materials has significant implications for occupational safety and disposal.
Sensory indicators and preliminary assessment
Tar often has an intense, pungent odor, is more brittle at room temperature and can have a reddish-brown to deep black coloration. Such impressions only serve for an initial assessment; they do not replace analytics.
Laboratory analysis and sampling
A sound evaluation is carried out by professional sampling and laboratory analysis, usually for PAH sum parameters and characteristic individual substances. Samples must be representative, separated by layers and properly documented.
Health and environmental risks of tar residues
Tar residues can contain components relevant to health. Emissions occur especially when heating, during mechanical fragmentation with high energy input and due to dust or aerosols. Careful, low-emission procedures significantly reduce risks for workers and the surroundings.
Emission sources in deconstruction
- Thermal methods that release vapors
- High-energy separation techniques with spark formation or strong heating
- Uncontrolled fragmentation and dust release
Investigation, assessment and planning in deconstruction
Professional execution begins with a systematic investigation and continues from the planning of work steps through to disposal.
- Inventory and historical overview
- Targeted sampling, laboratory evaluation, classification
- Definition of work methods and protective measures
- Selective separation of contaminated and uncontaminated components
- Clean logistics, intermediate storage and traceable documentation
Low-emission methods: separate mechanically instead of applying heat
When handling tar residues, methods that work without heat, with low vibration and low dust generation have proven effective. Concrete pulverizers and rock wedge splitters and concrete splitters from Darda GmbH enable controlled, selective separation of components, which can minimize the release of unwanted substances.
Selective removal of tar-containing zones
By gripping, crushing and splitting, tar-containing joint strips, upstands or bonded layers can be separated step by step. The bond to clean concrete is released at the same time, allowing material flows to be cleanly separated.
Reduced secondary impacts
Mechanical, hydraulic processes operate without sparks and without an open flame. This reduces odor and smoke development and facilitates compliance with protective measures, especially indoors or in sensitive environments.
Application in concrete demolition and special demolition
Tar-containing joints and bearing zones are regularly encountered by teams in concrete demolition and special demolition. Concrete pulverizers allow targeted opening of joint areas on pavements, bridges or ramps without extensively affecting sound concrete, in concrete demolition and deconstruction contexts. Rock wedge splitters and concrete splitters apply controlled splitting forces to release components along defined lines—helpful when tar-containing layers have been marked and exposed beforehand.
Building gutting and cutting
In building gutting, small-scale tar-containing residual layers on upstands, shafts or edge areas can be removed by incremental gripping and removal. This facilitates separate capture and avoids unnecessary mixing.
Special applications
For work in sensitive areas with higher requirements for low emissions and spark-free operation, hydraulic methods without thermal impact are particularly appropriate.
Tool selection and the roles of individual systems
The choice of tool is guided by the component, the composite and the goal of material separation. Hydraulic systems from Darda GmbH offer a coordinated range for the selective deconstruction of tar-affected zones.
Concrete pulverizers
For controlled biting and crushing of concrete with tar-containing joints or bearing layers. Advantages include precise work and low secondary impacts.
Rock wedge splitters and concrete splitters
For splitting massive components along defined lines. Suitable for isolating tar-containing layers and separating components without thermal influence.
Hydraulic power packs
Supply the tools with energy via suitable hydraulic power units. Important factors are sufficient drive power, sensitive control and reliable operation for consistent, reproducible results.
Hydraulic demolition shears, steel shears and Multi Cutters
For steel installations or mixed composites. They help to separate reinforcement, sections or attachments in advance so that tar-containing layers become freely accessible.
Occupational safety and health: principles
The protection strategy follows the principle of minimizing exposures. Mechanical, spark-free methods, closed material streams and orderly site organization are key elements.
- Dust and emission control: localized dust extraction, adapted working speed, covering of exposed areas
- Personal protective equipment: suitable gloves, protective clothing, respiratory protection according to the hazard assessment
- Hygiene and cleaning: low-contamination change zones, regulated disposal of wipes and consumables
Disposal and documentation of proof
Tar-containing materials must be collected separately, packaged and disposed of according to their classification. Complete documentation facilitates transport, handover and proof.
Separate collection
Mixing with clean concrete or asphalt must be avoided. Selective separation at the source saves effort in processing.
Packaging and transport
Tight, suitable containers and clear labeling help prevent emissions and avoid mix-ups.
Documentation
Accompanying documents, weighbridge tickets and laboratory reports must be kept complete and traceable. This ensures quality and legal certainty in the usual framework.
Process quality on the construction site
A clear structure of processes increases efficiency and reduces risks.
- Prepared cutting and splitting lines so tar-containing areas can be addressed in a targeted manner
- Step-by-step procedure: expose, separate, remove, package
- Continuous visual inspection and adjustment of parameters to material behavior
- Clean separation of material streams through suitable containers and route guidance
Avoid common mistakes
- Using thermal methods without necessity, thereby increasing emissions
- Insufficient investigation and misjudgment of the material type
- Mixing tar-containing and clean fractions
- Missing or incomplete documentation of disposal routes
Specifics in infrastructure and tunnel environments
In tunnel construction or at engineering structures, tar-containing joints and transitions can occur on concrete pavements, abutments or structure joints. Here, low-emission, low-vibration methods are important to avoid affecting the surroundings and to not disrupt the operation of adjacent areas. Concrete pulverizers and rock wedge splitters and concrete splitters enable precise, controlled work in such scenarios with reduced impact on the structure.
Planning notes for tendering and execution
Potential tar residues should be highlighted already in the tender documents. Requirements for investigation, the separation concept, low-emission working methods and disposal create clarity and comparability. In execution, prepared work instructions, defined tool selection and quality-assuring checks ensure the achievement of objectives.