Circular joint filling material Sustainability

When creating a concrete structure, expansion joints must be factored into walls and/or floors for various reasons – either between two new concrete components or between a new and existing component. The resulting breaks in the continuous concrete structure are often a few centimetres wide.

During the implementation, this is generally achieved by using a strip of compressible material that can withstand the pressure of the concrete pour – for example, EPS foam or Tempex. This material then remains as a part of the final construction. One advantage is that no sand or other material can seep into the expansion joint. However, a key disadvantage is that the ‘open space’ is not actually an open space, and that the material decays or wears down very slowly, and then contaminates the rubble during the demolition process.

The result: a material with a long lifespan and polluting properties is used to fulfil a temporary function.

The assignment for startups:

Develop a sustainable joint filler for expansion joints between cast-in-place concrete structures. It must have sustainable material properties and fulfil all technical requirements. Consider the construction, the usage and EOL (demolition/material harvesting) phases.


  • Easy to cut to size (length) on site.
  • Can be produced in various thicknesses, from 2 cm upwards (to be specified at time of purchase).
  • No moisture absorption during the concrete pour.
  • Good compressibility during the usage phase.
  • It must retain its shape during the concrete pour.
  • Ideally the raw materials should be bio-based or sourced by recycling/reuse.
  • Possible other processing requirements (to be defined by contractors).

Issued by:

Ingenieursbureau, City of Amsterdam