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Displaying Page 4 of 24

Research Report 319 Benchmarking pavement performance between Transit's LTPP and CAPTIF programmes

Published: | Category: Activity management , CAPTIF , Research programme , Research & reports | Audience: General

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.

Research report 433 Abrasion resistance of aggregates in asphalt

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

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...

Research Report 491 Factors influencing the decision to rehabilitate a pavement

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

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...

Research Report 372 Resealing strategies to increase seal life and prevent seal layer instability

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

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.

Research report 445 Investigating the contribution of sealing chip application rates to the early failure of chipseals

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

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.

Research Report 502 Assessing pre-tensioned reinforcement corrosion within the New Zealand concrete bridge stock

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

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.

Research Report 501 Assessment of shear stress limits in New Zealand design standards for high-strength concrete bridge beams

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

The design of concrete beams for shear loading is governed in New Zealand by the provisions of NZS 3101. The shear design provisions of NZS 3101 impose two limits on the permissible design shear capacity, including a maximum shear capacity of 8MPa. This 8MPa limit influences the efficiency of concrete beam design, and in particular the design of concrete bridge beams that have concrete compressive strengths greater than 40MPa. The validity of this limit was assessed through an examination of a number of other international design standards, statistical analyses using databases composed of all previous experimental testing of reinforced concrete (RC) and prestressed concrete (PC) beams, and results from an experimental investigation aimed at addressing deficiencies in the compiled databases. The research found that the limits in NZS 3101 are excessively conservative compared with the limits imposed in most other design standards.

Research Report 277 Harmonising automated rut depth measurements – stage 2

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

Rut depths are permanent deformations of the pavement structure, and an important indicator of the structural integrity of the pavement as well as having an impact on road user safety. Therefore, most road controlling agencies regularly monitor the levels of rut depths on their pavements. Keywords: pavement, pavement condition, pavement monitoring, profilometer, rut depth, simulation, straight-edge

Research report 443 Potential of the Wehner-Schulze test to predict the on-road friction performance of aggregate

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

The specification for aggregates for use on New Zealand roads includes the British Polished Stone Value (PSV) test. This test and the acceptance criteria were adopted in New Zealand in the 1990s, based on British experience that they were the best available method of predicting the on-road friction performance of aggregate. However, research performed by a number of people in New Zealand has shown that the prediction of performance by the PSV test is extremely variable. The Wehner-Schulze (WS) test method, developed in Germany in the 1960s and commonly used there, can test samples taken from the road. This research, which was carried out between December 2009 and August 2010, aimed to assess the potential of the WS test for predicting chipseal surface friction. The chipseal samples taken from New Zealand roads could not be used for testing because their very high texture imposed too much stress on the equipment.

Research Report 560 - Reduced bitumen application rates using bitumen emulsions

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

This research project investigated the differences in cohesive energies of model chipseal samples prepared from bitumen emulsions, the base binders, and the kerosene cutback base binder.
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