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Sealing joints and seams in asphalt and concrete
Maximum durability and safety for traffic areas
In road construction, joints, seams and connections are the most critical areas of a road surface. If they are not properly constructed and protected, cracks, moisture penetration and structural damage can occur – with serious consequences for traffic safety and high repair costs.
These risks can be minimised with high-quality solutions and the right planning and execution in accordance with the German specifications of ZTV Asphalt-StB 07/13 and ZTV Fug-StB 15.
What are joints, seams and connections?
Joints
Joints are intentional or work-related spaces between two asphalt or concrete layers or between their layers and components such as kerbs, manhole covers, etc. They allow material movements such as expansion or compression due to temperature fluctuations and prevent uncontrolled cracking. A joint gap is usually created by cutting.
Seams
Asphalt seams are contact surfaces that are created when asphalt mix is laid in lanes, alongside or near to breaks in the application of the asphalt (longitudinal or lateral seams). As the connection is often only adhesive, there is a high risk of water and pollutants entering. Seams are ‘slightly angled’ with an inclined seam flank of approx. 60 °.
Connections to existing structures
Connections are contact surfaces between different types of asphalt mix (e.g. rolled asphalt and poured asphalt) or to built-in components, e.g. in connection with kerbs, paving, etc. In accordance with ZTV Fug-StB 15, connections must be provided with suitable jointing materials to prevent damage caused by load changes and weathering.
It is extremely important to protect these weak points with high-quality products. With DENSO's high-quality solutions, asphalt and concrete roads can permanently and safely withstand the diverse loads they endure. Introduced in 1977, TOK®-Band bitumen joint tape revolutionised road construction and has been synonymous with bitumen joint tapes ever since. TOK® products are simple and easy to use and have an extremely long service life.
Bitumen joint tapes for perfect joints and seams
The tape TOK®-Band has proven itself for decades as the ideal solution for sealing joints and seams. The bitumen joint tape possess exceptional stretching and adhesion properties and can be applied cold (self-adhesive) or using a burner. Many TOK® tapes do not require you to go through the time-consuming process of applying a primer, which saves a significant amount of time and money – and also protecting the user and the environment.
Machine application with the TOKOMAT®
The TOKOMAT® is used as a processing device for the fast and reliable application of joints on milled and cut edges, especially on motorways and national A-roads. The machine-extruded bitumen joint tape creates a joint that is appropriate for the profile and height, even on poorly processed surfaces. With an application speed of approx. 15 m per minute, the TOKOMAT® is an exceptionally fast and precise solution.
Seam adhesive for secure connections
Seams must be painted over with polymer-modified bitumen or a bitumen-based binding agent. TOK®-Plast is a cold-processable, stable material made from polymer-improved bitumen, making it ideal as a permanent seam treatment. Using the PLASTOMAT®, developed specifically for this product, TOK®-Plast is easy and quick to apply.
Protection of sensitive joints
DENSOLASTIC®-VT is the ideal solution to protect joints against the ingress of petrol and aircraft fuels, heating oil, diesel, unused oil and inorganic lyes. DENSOLASTIC®-VT is solvent-free and ETA-certified, for use in storage, filling and transport applications and in manufacture, treatment and usage settings.
Hot-pour compounds for permanent joint sealing
If joints are cut into asphalt and concrete surfaces at a later stage, for example, they can be filled with TOK®-Melt Hot-pouring compounds. These products are also used as crack filling compounds or rail bedding compounds.
Why are joints and seams particularly susceptible to damage?
- Traffic loads: Constant load changes caused by vehicles, especially trucks and heavy goods vehicles, cause material fatigue.
- Temperature-related movements: Asphalt and concrete expand when heated and contract when cooled, causing the joint filler to compress or stretch.
- Weather influences: Water penetrates, freezes in winter and causes frost damage.
- Poor workmanship: Errors in seam and joint construction or inaccurate cutting at connection transitions lead to premature damage and the need for renovation.
Scientific studies show that unsuitable or missing joint seals in asphalt construction drastically increase water permeability and cause long-term damage. Professionally executed joints reduce water flow by an average of 99 %.
Important technical regulations
In the German road system, there are technical regulations for the planning, construction and operation of roads, some of which are for information and guidance purposes, but some of which must be strictly adhered to; the most important are:
✓ ZTV Asphalt-StB 07/13 (Additional Technical Contract Conditions for the Construction of Traffic Areas Made of Asphalt): Requirements for joints, seams and connections with pre-treatment and formation.
✓ ZTV Fug-StB 15 (Additional Technical Contract Conditions for Joints in Traffic Areas): Specifications for the correct joint formation and the use of joint sealing compounds.
✓ TL Sbit-StB 15 (Technical Delivery Conditions for Special Bitumen-Based Binders): Specifications for seam adhesives and bitumen-containing binders.
✓ DIN EN 14188-1: European standard for joint fillers in asphalt and concrete surfaces.
Interesting facts from the regulations:
- Seams can only bond the contact surfaces; they cannot compensate for movement.
- The joints must also be pre-treated in the binder layer.
- The joint filler must be flexible, adhesive and able to move.
- Joints and seams in the longitudinal direction must not be located in the area of wheel tracks or road markings.
- For connections, the grouting depth for asphalt joints must be ≥ 1.5 times the joint width and concrete transverse joints must be executed with a maximum of 2.5 times the joint width.
Avoiding damage: What needs to be considered during planning?
✔ Seal joints professionally, inspect them regularly and repair them in good time.
✔ Use suitable materials in accordance with ZTV Asphalt-StB & ZTV Fug-StB.
✔ Take temperature movements and material expansion into account.
Practical recommendation: Authorities are increasingly relying on cutting back and forming a joint instead of a simple seam to prevent long-term damage.
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