Theunis Henning

Detecting Flushing of Thin-Sprayed Seal Pavements Using Pavement Management Data

AbstractFlushing is a pavement surface defect that affects the structural integrity of thin-sprayed seal (chip seal) surfacings. Analysis was carried out on pavement performance data to determine the combination of factors that provides the best indication of flushing occurrence on in-service pavements. Data were sourced from the Long-Term Pavement Performance (LTPP) programme in New Zealand as well as from field testing. The LTPP data were analysed in four categories; pavement composition characteristics: traffic-related factors, climatic factors, and effects of other pavement defects. Factor and correlation analyses were used to determine and investigate the factors that showed significant relationships to flushing. Surface thickness, surface age, surfacing type, and rutting were found to have statistically significant correlations to flushing. Field testing provided data relating to the soil moisture environment under the pavement. The dry density and water content of soil were identified as having sig...

Relationship Between Traffic Loading and Environmental Factors and Low-Volume Road Deterioration

Many countries use some form of model to determine road user charges. Trucks are expected to pay for most of the cost because heavy vehicles are responsible for most of the deterioration of roads. This research documents findings that will ultimately be used to refine the New Zealand road user charge models. The research was undertaken on data from the Long-Term Pavement Performance Program with the specific aim of determining the relative damage caused by heavy-vehicle loading alone compared with the combined effects of loading and environmental impacts. As part of the overall research process, a cluster analysis was undertaken. The results from this analysis also emphasized the importance of drainage. The cluster analysis resulted in a recommended stratification of low-volume roads on the basis of their urban or rural location, traffic loading, and climatic area. This stratification could be used for a more detailed implementation of a user charge model if needed. On similar low-volume roads, an approximate 0.1-mm/year higher rut rate was observed in areas that had a wetter climate in combination with sensitive in situ soil conditions. The results also illustrated that adequate drainage was vital for limiting environmental impacts. Roads with inadequate drainage had a rut rate 2.5 times as high as that of roads with the necessary provision for drainage.

Comparing Results between the Repeated Load Triaxial Test and Accelerated Pavement Test on Unbound Aggregate

AbstractUnbound granular materials (UGM) are extensively used as basecourse materials around the world as they are capable of bearing relatively high traffic loads and are an economical option in comparison to bound materials. The unbound materials performance as basecourse determines the life-cycle costs of a pavement. The extent to which the repeated load triaxial test can predict the performance of unbound granular materials in the laboratory is an important parameter for road designers. Moreover, the performance of the unbound basecourse materials depends upon the moisture conditions when they are being loaded, gradation curve of the material, in situ density, permeability, and the nature of the aggregate fines (clays). There is a need to find the factors that cause the variation in the performance of the materials both in the laboratory and in-field pavement conditions to enable appropriate selection and use. This research utilizes accelerated pavement tests (APT) alongside repeated load triaxial (RL...

A risk and criticality-based approach to bridge performance data collection and monitoring

Bridges constitute a substantial and vital part of any transport infrastructure system. The functionality of the system is therefore reliant on the asset management strategies adopted for its bridges. To understand and manage bridge performance, data of appropriate quality has to be collected in a cost-efficient way and closely linked to the decisions made with it. To ensure a coherent approach, a data collection strategy for asset management of road bridges has been developed in this study. In the strategy, a combined risk and criticality-based approach is used to prioritise each bridge and to assign it to one of three data collection levels comprising core, intermediate and advanced. For each collection level, the strategy provides guidance on the type of data to collect, the accuracy and precision required in the data collection process, the frequency of inspections, and the recommended collection techniques to be used, including visual inspection, non-destructive evaluation and structural health monitoring. The strategy will help asset managers to develop a deeper level of knowledge on the bridges that have the greatest impact on the system functionality and to collect data of the required quality needed for the decisions they make.

Risk based bridge data collection and asset management and the role of structural health monitoring

Bridges are critical to the operation and functionality of the whole road networks. It is therefore essential that specific data is collected regarding bridge asset condition and performance, as this allows proactive management of the assets and associated risks and more accurate short and long term financial planning. This paper proposes and discusses a strategy for collection of data on bridge condition and performance. Recognizing that risk management is the primary driver of asset management, the proposed strategy prioritizes bridges for levels of data collection including core, intermediate and advanced. Individual bridges are seen as parts of wider networks and bridge risk and criticality assessment emphasizes bridge failure or underperformance risk in the network context. The paper demonstrates how more reliable and detailed data can assist in managing network and bridge risks and provides a rationale for application of higher data collection levels for bridges characterized by higher risk and criticality. As the bridge risk and/or criticality increases planned and proactive integration of structural health monitoring (SHM) data into asset management is outlined. An example of bridge prioritization for data collection using several bridges taken from a national highway network is provided using an existing risk and criticality scoring methodology. The paper concludes with a discussion on the role of SHM in data collection for bridge asset management and where SHM can make the largest impacts.

Guidelines for Selecting Surfacing Alternatives for Unsealed Roads

Road networks are the vital arteries of societies. The need for roads to provide safe and comfortable access and thus contribute to economic sus-tainability and environmental protection has been increasing with time. Over the years, engineers have become knowledgeable in the optimization of resources for maintaining unsealed roads. Numerous manuals and guidelines have been produced, mostly for developed countries with extensive unsealed networks. Some manuals adopt innovative construction and maintenance methods for the surface layer of unsealed roads. The World Bank has commissioned the development of guidelines for surfacing alternatives for unsealed rural roads to assist countries in making surface selections. The guidelines offer detailed discussion of the following topics: summary of current international experience based on a survey of the literature, case studies and examples, and development of a decision framework for selecting the most appropriate surfacing for given circumstances. The decision framework was developed to offer guidelines and at the same time to remain flexible enough to be applicable for most circumstances. The framework offers a methodology consisting of a three-stage process: Stage 1—evaluation of the need for upgrading on the basis of local environmental and geographic conditions (this stage also allows for overriding political or other aspects); Stage 2—selection of suitable surface types and technologies from the presented list, to result in a short list of options; and Stage 3—suggestion of economic and financial analysis techniques to rank the technically feasible options developed during Stage 2. The guidelines and issues taken into account during the Stage 2 process of deciding on surface technologies are summarized.

Evaluating pavement performance through smart monitoring – effects of soil moisture, temperature and traffic

This paper presents the findings from a research conducted to investigate the effects of moisture and environmental conditions on the mechanical behaviour of granular pavements. Analysis was conducted on data collected from state-of-the-art instrumentation on two field pavement sites located in Sunshine Coast, Australia. The sites were monitored over three years, and daily temperature, moisture and strain values were analysed. Large tensile strains in the basecourse occurred when moisture increased and temperature decreased at the end of day. This result indicated that the change in soil pore pressure due to moisture and temperature variations was causing the strains in the pavement. Heavy traffic volume had a minor effect on basecourse strain in comparison to moisture and temperature although, it was concluded that the combined effect of soil moisture, temperature and heavy traffic loading was a cause for large vertical strains in the pavement.

Improving Recycled Asphalt Mix Performance Through Rejuvenation

Developing technologies that provide sustainable solutions for future pavement construction is vital given the ever-increasing demand on the supply of bitumen and good-quality pavement construction materials. Recycled asphalt pavement (RAP) is a technology that presents many advantages in cost and environmental savings. This study investigated the performance of RAP mixes containing rejuvenation additives to determine the effects of those additives on the deformation (rutting) resistance, cracking resistance, and fatigue performance of RAP mixes. Laboratory testing was conducted on 11 RAP mixes that were manufactured with RAP proportions of 15% and 30%, as well as with the addition of different types of rejuvenating agents. Results produced useful performance indicators for the use of rejuvenation additives in RAP. The mixes that had rejuvenation additives preserved the high deformation resistance of RAP mixes, particularly at the higher RAP proportion of 30% when compared with a mix with no RAP, and concurrently the addition of rejuvenators counteracted against overstiffening effects of RAP. The addition of RAP, especially 30% RAP proportion, had poorer fatigue performance than when only 15% RAP was used, but with the use of rejuvenation agents, the fatigue performance of the high RAP mixes improved significantly. Use of a maltene fraction for RAP rejuvenation had marginally better fatigue performance than a chemical rejuvenation agent. The research results provide a valuable understanding of the behavior of RAP mixes and, in particular, the positive performance results that can be gained by using rejuvenation additives.

Using a multi-phase model to predict flushing of sprayed seal pavements

Flushing is a pavement defect that has a negative effect on the structural integrity and performance of a pavement surface. The aim of this study was to develop a model to predict the occurrence and progression of flushing on sprayed seal pavements. Data analysis and model development were performed using data sourced from New Zealands Long-Term Pavement Performance programme. The developed model consists of two phases to model (1) the probability of flushing initiating on a pavement and (2) the progression of flushing. The probability of flushing initiation was modelled using a logistic model format, and the progression of flushing was modelled using a linear model format. Testing of the developed model revealed that the logistic model predicted the probability of flushing initiation at 76% accuracy, whereas the linear model had statistically robust predictions of flushing. The developed model is recommended for use in sprayed seal pavement management processes.