Assessing the Engineering Properties and Performance of Limestone Compared to Contract Specifications As Road Construction Aggregate in the Kingdom of Tonga
Flexible unbound aggregate pavement failure can be caused by a number of factors due to the nature and duration of repetitive loading being applied. These pavements are considered to be elastic multilayered system made up of a bound layer at the surface and unbound layers below. Modulus of elasticity, resilient modulus and Poisson ration properties of these layers are indicative of their capabilities to absorb and dissipate the compressive and tensional stress being subjected to minimize the load impact on the supporting subgrade material. Design objectives are therefore driven by ensuring the resultant strains are below the value of those that would cause deformation or damage to the pavements.
Aggregate material properties play a significant role in delivering the design objectives. More durable aggregate with less inclination to disintegrate under loading pressure are preferred to weaker material. This can be tested using a number of standard aggregate testing procedures.
The specific aggregate tests are usually included as part of the contract specifications so that the pavements are constructed with sound material reflecting the design requirements.
In this research, limestone aggregate samples were obtained from Tonga to be tested and assessed together with three historical case studies of project carried out in Tonga. Test results previously conducted by others were also reviewed.
Based on the analysis carried out, it was found that the contract specifications for unbound aggregate and chipseal projects in Tonga did not meet the minimum requirements for this type of work.
Further research is required to assess the possible use of reinforcement material such as fibres or stabilisation using cement and/or lime to strengthen the weak limestone aggregate. This could help alleviate further environmental degradation currently being caused by excessive limestone mining in Tonga.