Resources

Small diameter tyres are increasingly being used in heavy vehicle applications. While they give operational advantages in some situations they may have a negative impact on pavement wear. This study, carried out between 1996 and 1997, investigated the implications for pavement wear of using small diameter tyres in place of standard sizes.

The road transport industry in New Zealand has been lobbying for increases in the allowable mass limits for heavy vehicles on the basis that this would give increased efficiency and benefits to the economy. Some of the proposals for increased mass limits involve increased axle load limits which would clearly lead to additional pavement wear. Road controlling authorities, while sharing the industry’s aims for increased efficiencies in the road transport system, are concerned that any additional pavement wear generated by higher axle loads will be paid for, so that the standard of the roading network can be maintained. At present (2005) Road User Charges (RUCs) are based on the fourth power law, which was developed from the AASHO road test in the United States in the 1950s. The pavements and vehicles used for that test differ considerably from those in use in New Zealand today.

This document is intended as a guide for practitioners in the assessment of site liquefaction potential. It is based on a three year research project (1993–1996) and recommends six liquefaction assessment methods which have given the best correlation with known soil behaviour under earthquake loading based on historic information from 14 sites in New Zealand. It also discusses the development of liquefaction prediction models and their advantages and limitations, as well as the application of the recommended liquefaction assessment methods, earthquake and site factors affecting liquefaction, and site investigation methods. Appendices detail the sites and provide information on which the assessments are based.

Bridge health monitoring is a method of evaluating the ability of a bridge to perform its required task (also called fitness for purpose) by monitoring the response of the bridge to the traffic loads it has to withstand.

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.

A review has been made of the international literature that was available up to 1996 and of New Zealand experience and practices for the stabilisation of materials for use in road pavements. The review indicates that stabilisation has provided economic and durable road pavements, and highlights the New Zealand approach of using relatively low levels of additives to provide flexible stabilised pavements.

Bridge health monitoring is a method of evaluating the ability of a bridge to perform its required task (also called fitness for purpose) by monitoring the response of the bridge to the traffic loads it has to withstand.

The historical development of the traditional Marshall and the modern gyratory-based, performance-related asphalt mix design procedures is described. New Zealand is progressively adopting performance-related specifications and implementing performance contracts for road maintenance and construction. Thus, in 2002, asphalt mixes sourced from a range of asphalt manufacturers located around New Zealand were subjected to a comprehensive laboratory testing regime, to determine their volumetric- and performance-related properties, such as modulus. Two sets of asphalt specimens were created, using either Marshall or gyratory compaction procedures, based on existing mix designs. They were then tested by AUSTROADS APRG18 procedures and equipment to provide performance-related data.

This report describes research in 2004 and 2005 aimed at improving the means by which the durability of bitumens manufactured or imported to New Zealand for use in chipseals is assessed and monitored. Bitumen durability refers to the long-term resistance to oxidative hardening of the material in the field. Although, in-service, all bitumens harden with time through reaction with oxygen in the air, excessive rates of hardening (poor durability) can lead to premature binder embrittlement and surfacing failure resulting in cracking and chip loss. Some means of assessing durability by accelerating the process in the laboratory is necessary. However, no internationally accepted ‘standard’ exists for bitumen durability, as for some other bitumen tests (eg penetration). Keywords: bitumen, chipseal, durability, oxidation, pavements, roads, testing

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