PAVEMENTS – Evaluating the moisture susceptibility of lightly bound cement layers

Granular layers underneath sprayed seal, asphalt or concrete surfacings can be highly susceptible to moisture induced damage. If the degree of saturation (DoS) is not controlled, premature failures may occur. Current practice in the regions is to treat granular materials with small quantities of cement (typically 1–2%) in order to improve properties and avoid the requirement to control DoS during construction.  

The objective of this multiple-year project is to determine the threshold, in terms of cement content and moduli, at which each material transitions from behaving as an unbound granular material to a cement modified material with reduced risk of moisture damage and early pavement failure. The anticipated benefits of this project is to have improved understanding on the impact of moisture on lightly bound materials and minimise premature failures in pavements that could have otherwise been avoided.  

The testing shows that, as expected, moisture content (and degree of saturation) has an impact on the performance of lightly bound materials when assessed using the repeat load triaxial (RLT) test. To remedy this shortcoming, changes to the specifications regarding lightly bound materials have been recommended. Further testing will aim to better define what the specifications will need to be before surfacing can be done in order to minimise these failures.