Resources

This project was designed to investigate the importance of drainage maintenance for pavement performance and to recommend a maintenance strategy. With restrained funding for pavement renewals drainage maintenance is a cost-effective method to ensure optimum pavement performance.

Performance specified maintenance contracts (PSMC) have been operational in New Zealand for more than six years. These contracts are driven by key performance measures (KPMs) that are used to define the expectations of the road agencies and monitor the progress and performance of the contractor. As the effectiveness and efficiency of the KPMs is vital for achieving the desired results, it is essential to examine the effectiveness of the current KPMs in controlling and directing the maintenance contracts. The report examines the interpretations of the collected data using average and mode. The poor representation of the total network condition by the traditionally used average is illustrated by numerous examples. Alternative representation of the network condition is proposed and illustrated by using the mode of the data set.

The falling weight deflectometer (FWD) which measures pavement deflections was assessed for its ability to predict the life of a newly constructed or rehabilitated pavement. FWD measurements used in the study were from NZ Transport Agency’s test track CAPTIF, roads that have failed and from two Performance Specified Maintenance Contracts where the actual life from rutting and roughness measurements could be determined. Three different methods to calculate life from FWD measurements were trialled. The first, a simple Austroads method that uses the central deflection only and was found to either grossly over predict life by a factor of 1000 times more than the actual life or grossly under predict the life. The second two methods trialled were based on Austroads Mechanistic Pavement Design where the life is determined from the vertical compressive strain at the top of the subgrade.

Investigations into the cohesive properties and oxidation resistance of an acid cured, epoxy modified open-graded porous asphalt (OGPA) were undertaken and an associated accelerated loading test carried out at Transit New Zealand’s CAPTIF facility. Results from the Cantabro test (a test of mixture cohesion relating to the resistance of OGPA to surface abrasion losses) indicated that the early life cohesive properties of cured epoxy OGPA should be comparable to that of standard OGPA at 25°C and markedly superior at 10°C. The modulus of the cured epoxy mixture was much higher than that of the standard OGPA but this is probably of little benefit given that failure through rutting and deformation is uncommon for properly designed OGPA.

This report details the findings from research conducted on the Long-Term Pavement Performance Programme (LTPP) and on the Transit New Zealand CAPTIF programme for accelerated pavement testing. The research was aimed at delivering a complete new model format to predict rut progression on New Zealand roads. It was based on earlier findings that suggested some limitations with the current approach using the World Bank’s HDM rutting models.

The objective of this project was to investigate the durability and mechanical integrity of aggregate with a high polished stone value (>60) used in hot mix asphalt, particularly chips or coarse aggregates in stone-on-stone mixes such as stone mastic asphalts and open graded porous asphalts. The research was carried out in Auckland, New Zealand, in 2009-2010. Test sections were constructed within a roading contractor's yards at Auckland and Taupo. The aggregates used were drawn from four different sources. Significant degradation took place during laying and compaction, but trafficking produced little further breakdown, if any. However, a slight decrease in air voids and texture depth was apparent. Most of the source property tests could not predict the degradation that occurred in the test sections. The Los Angeles and micro-deval abrasion tests were probably the most useful. The gyratory compactor test was also evaluated as a prediction tool without a great deal...

The objective of this research, undertaken in 2008–11, was the development of an improved method of modelling the decision to rehabilitate a typical New Zealand thin-surfaced unbound granular pavement. This was driven by previous research that had found a poor correlation between the recorded data and the decision to rehabilitate. It had been hoped that by talking to local engineers and examining pavements proposed for rehabilitation that distress not currently recorded might be identified. This would have then driven the development of better models and may also have expanded the detail collected in the visual surveys. The research found that the drivers are not obvious and that the decision may be based on factors other than those of an engineering nature. It is recommended that a more consistent decision making process be developed that places more emphasis on the present pavement condition rather than the present emphasis on the net...

A study of cores from multilayer chipseals shows that fine solid materials (passing 4.75 mm) fill a significant proportion of the chipseal volume that would otherwise be available for bitumen. If fines are ignored, the available voids are typically about twice the expected volume of bitumen that would be sprayed. Generation of fines may therefore contribute significantly to premature flushing. The origin of these fine materials remains to be examined; at least six different processes may contribute, and the relative contributions may vary from site to site.

Chipsealing is the predominant resurfacing used on the state highway network in New Zealand. An important component of chipseals is the sealing chip layer that is applied to protect the binder layer and provide surface texture and surface friction. There are a number of specifications written to ensure that the sealing chip used is the correct size and shape, and that it has the appropriate ‘polished stone value’ (PSV), but no specifications on chip application rates exist. Early-life failures of chipseals are generally attributed to the binder, the binder application rate, or the weather; however, the sealing chip application rate may also contribute significantly to these early failures.

Precast pre-tensioned concrete bridge construction became common in New Zealand in the 1950s and a large number of pre-tensioned concrete bridges were constructed between 1953 and 1980.