Currently, LTA maintains more than 2000 road structures (flyovers, viaducts, underpasses, road tunnels, overhead bridges, footbridges, road culverts and retaining walls) island-wide. Over the years, we are beginning to see an increasing number of our concrete structures facing challenges on durability. This is largely due to weathering, exhaust fumes from traffic and other harmful pollutants. Durability issues arising from carbonation with the harmful effects of water and chloride ingress, if not properly addressed, would lead to the deterioration of the concrete structure in the form of delamination, spalling concrete and corroding reinforcement, which in turn would affect the service life of the road structures.
Annex A shows photos of common defect found on road structures.
One effective solution to improve durability is to apply a layer of protective coating to the road structure. With improved durability and extended lifespan by 10 years (conservatively), we can delay the replacement of the structures. Improved durability of the road structures would mean the need for fewer repairs, which would otherwise cause inconvenience to motorists and the public. In addition, the protective coating system also has the capability to repel dust and grime, prevent fungus, biological and algae growth. With the protective coating, usually in grey, the need for washing can also be greatly reduced in most areas.
Since 1998, LTA has started applying protective coating to bridges, viaducts, flyovers and vehicular underpasses when they are being upgraded. The upgrading works include structure strengthening (thickening of structure elements and installing external post-tensioning) and expansion joints replacement. Once upgraded, these road structures could accommodate heavier and larger goods vehicles (gross vehicle weight increases from 24 tonnes to 46 tonnes). The upgrading works are an ongoing process to ensure that the integrity of the road structures is not compromised. Thus far more than hundreds of road structures have been upgraded.