A problem that is typical of Australian roads is that the pavement fails not because of the pavement construction but because the subgrade on which the pavement was built is not able to carry the loads of our modern traffic. This could be because of moisture ingress, under design or increased traffic loads. This is a very difficult problem for road authorities as the problem is well below the surface and requires excavation to get to the failed subgrade.
More and more engineers are realising that the only solution is to lime stabilise the failed subgrade which achieves two important results
- The subgrade is made relatively impervious therefore not affected by moisture
- The subgrade is made substantially stronger and given a far longer life as well as reducing the pavement design thickness required for the upper layers
Of course the best cure is to lime stabilise all suitable subgrades prior to original construction as many road authorities are now putting into practise.