How can joint seals improve FOD prevention?
Concrete is not a flexible material. It always wants to shrink or expand. This can cause cracking. Therefore, airfield aprons, taxiways and runways often consist of connections to the asphalt and large areas of concrete pavement, divided into sections (slabs) with expansion joints. The expansion joints absorb the movement in the concrete and prevent the pavement from breaking.
The degree of shrinkage and expansion depends on the climate (Delta T including sun intensity) and the size of the slabs and the joints. It is important to design the joint construction correctly so that the joint size matches the size of the concrete. The design of the joint construction is therefore very important to reduce the risk of FOD.
These expansion joints need to be elastically sealed with the right sealant to prevent the sand flushing away from below the construction. In addition, the seals ensure the pavement remains liquid tight, which prevents soil contamination by hazardous liquids, including kerosene, oil and de-icing agents.
Joint sealants therefore require high standards. During their entire lifetime, they must bond to the pavement construction and remain elastic and liquid tight. That is why the sealants must resist:
- Ageing due to climatic conditions, including heat, frost, temperature variations and sunlight;
- Movement tue to expansion and shrinkage of slabs;
- Chemical loads, including kerosene, petrol, acids, alkalines, and other chemicals (like de-icing materials).