Resources

The primary objective of the project was the development of criteria to define the end-of–life condition of pavements. These criteria could then be used in pavement performance modelling to obtain a more robust measure of remaining life. Another objective was the generation of a new model for maintenance costs. This could then be combined with the existing models for roughness and rutting to define a distress level at which rehabilitation should occur. None of the maintenance cost models developed were particularly successful in producing a reliable prediction of maintenance costs based on the pavement characteristics available from RAMM. Therefore, a logit model was developed to predict rehabilitation decisions. The major factors in the rehabilitation model were maintenance costs, traffic levels and roughness. The rehabilitation decision model derived for this study predicted rehabilitation decisions well. Approximately 72% of pavements that had been rehabilitated were predicted as requiring rehabilitation.

Flexural beam breakage and fatigue tests were conducted in 2008–11 to determine their relationships with pavement fatigue life and tensile strain for a range of New Zealand materials for use in pavement design of stabilised aggregates. The results showed that the tensile fatigue relationships from several fatigue tests under repetitive loading could be approximated by single flexural beam breakage tests. These relationships resulted in significantly longer pavement lives than the Austroads pavement design criteria but still predicted shorter fatigue lives than what actually occurred at the Canterbury accelerated pavement testing indoor facility (CAPTIF) test track, indicating some conservatism in the approach. Further research is required to validate the tensile fatigue design procedure against actual field data. Keywords: aggregates, basecourse, CAPTIF, fatigue, beam fatigue testing, modulus, pavement design, strain, tensile strain criteria, tensile strength

Pavement performance modelling for New Zealand roading networks, currently relies on an adjusted structural number (SNP) which is a single parameter intended to describe the performance of a multi-layered pavement structure in terms of its rate of deterioration with respect to all structural distress modes, as well as non-structural modes. This parameter had its origin in the AASHO road test in the late 1950s, before the advent of analytical methods. Hence refinement to keep abreast of current practice in pavement engineering is overdue. This research describes the basis for a new set of structural indices and how these can be used to obtain improved prediction of pavement performance: both at network level and for project level rehabilitation of individual roads. The results are (i) effective use of all the data contained in RAMM, (ii) more reliable assignment of network forward work programmes, (iii) reduced cost through targeting only those sections...

Aggregates used as base materials in thin-surfaced granular pavements common to New Zealand contribute at least half the wheeltrack rutting and roughness seen at the surface. Currently, no reliable cost-effective measure of an aggregate’s resistance to rutting in specifications exists. Several test methods using the repeated load triaxial (RLT) apparatus were investigated for use in specifications for basecourse aggregates. Rut depth prediction methods and pavement finite modelling were applied to the RLT results to determine traffic loading limits for the aggregates tested. It was found that the average slope from the six-stage RLT test was the best predictor of traffic loading limit and this test was recommended for use in basecourse specifications.

This research project had the objective of identifying areas where changes could be made in the use of thin layers of asphalt so that improvements in performance could be obtained. The project was not designed to investigate quality issues, but was to concentrate on materials and selection. The project was initiated because the NZ Transport Agency had found that costs of resurfacing using asphalt had escalated and the lives being achieved appeared to be short. This research in this report, which was undertaken between 2007 and 2012, investigated the following areas:

The transverse shear forces generated by multi-axle groups depends on many factors including turn geometry, vehicle type, axle weights, tyre size and configuration, suspension geometry, and the number and type of axles. This study quantifies the impact of some of these parameters on the transverse pavement shear forces or scuffing forces generated during constant low-speed turns. A field trial on an unbound granular pavement structure with chipseal surfacing assessed the level of scuffing force that caused visible wear on the pavement surface. A computer model of a tandem simple-trailer was used to simulate the forces observed in the field. Computer models were used to assess the effects of axle load, axle group spread, wheelbase, and turn geometry on peak scuffing forces; to simulate various low-speed turns; and to identify the relative impact of the peak scuffing forces for the different vehicles.

Specialist surfacings such as high-friction and coloured traffic-calming surfaces have gained huge popularity since their introduction. However, the reputation of these specialist systems in New Zealand is also plagued by premature failures due to cracking and other related modes.

Structural hot mix asphalt (HMA) pavements have become popular in New Zealand in recent times as heavy traffic volumes have increased and early failures of granular pavements have become more common, especially in urban areas where road maintenance causes major traffic disruption.

A routine inspection revealed significant corrosion of the prestressing strand on a concrete road bridge built in 1966 to a standard design used in about 117 State Highway bridges in New Zealand. To identify the cause of the deterioration and how many bridges of this design might be affected, the conditions of 29 similar bridges on New Zealand State Highways were evaluated by site investigation. The research, carried out in 2005–2006, found that although the concrete quality in the bridge beams was generally good, the combination of cover depths less than 25 mm and exposure to salt spray had increased the likelihood of corrosion in bridges of this design in the B2 (coastal frontage) exposure zone. Bridges in the B1 (coastal perimeter) and A2 (inland) zones are less likely to be affected, although the concrete in some of the beams contained chlorides added during construction.

The corrosion of reinforcing bars and prestressing steel is the most significant risk to the durability of concrete road bridges in New Zealand. The application of water-resistant surface treatments has been suggested as a means of delaying corrosion damage. This research, carried out between 2007 and 2010, reviewed international research findings and the use of preventive surface treatments by road-controlling authorities in Australia, the UK, and North America, to develop a guideline for selecting appropriate surface treatments for delaying chloride-induced corrosion damage on concrete road bridges in New Zealand. The findings indicated that the effectiveness of surface treatments for reducing corrosion activity and extending service life depends not only on the chemical composition of the treatment, but also on the condition of the concrete substrate, the application process, and environmental exposure conditions. A process was developed to identify the potential benefits of such surface treatments for individual bridges and for...