African Case Studies: Developing Pavement Temperature Maps for Performance-Graded Asphalt Bitumen Selection

Abstract

The reliable performance of roads is crucial for service delivery, and it is a catalyst for domestic and cross-border spatial development. Paved national roads are expected to carry higher traffic volumes over time as a result of urbanization and to support the economic development in the continent. Increased traffic levels combined with expected increases in air temperatures as a result of global warming highlight the need to appropriately select bituminous road materials for a reliable performance of asphalt roads. The objective of the paper is to present African case studies on the development of temperature maps necessary for performance-graded bitumen selection for road design and construction. A consistent approach, that caters for the variability of geographical, environmental and climatic conditions, does not currently exist within the continent. Therefore, this paper discusses a series of critical components in the development of temperature maps for performance-graded bitumen including (i) pavement temperature models and climatic zones in Africa; (ii) the effect of urban heat islands on pavement temperature; (iii) sources of weather data and (iv) the mapping procedure to produce temperature maps. Characterizing the thermal properties of the pavement was found to be an important factor for reliably calculating expected road temperatures as well as the consideration of the ambient climate for a given location. During this study, the urban heat island effect was found to have little influence on the maximum pavement temperatures but a significant effect on the minimum pavement temperatures. Some areas of the urban district assessed in this investigation were found to increase by two performance grades according to the minimum temperature criteria. The recent observed weather data from weather stations are the most accurate means of measurement of the ambient environmental conditions necessary for performance-based specifications, but they are not always easily accessible, and therefore other sources of data, such as satellite data, may need to be used instead. With the expected temperature increases expected as a result of climate change, the use of Global Climate Models also opens new avenues for performance-based material selection in the African continent for expected climates as an alternative to traditional approaches based on historically observed weather.

Investigating the Trends and Drivers between Urbanization and the Land Surface Temperature: A Case Study of Zhengzhou, China

“…Some studies on Zhengzhou City found that green space and water can effectively reduce LST and mitigate the UHI effect [28,44]. Albedo decrease due to urbanization leads to LST increase [45][46][47]. These findings strongly confirm the plausibility of the above spatial heterogeneity of LST.…”

Performance of Pavement Temperature Prediction Models

“…Sci. 2023, 13, 4164 2 of 12 Extensive research has been carried out across the world and in different climatological regions to formulate pavement temperature prediction models that can be used to select asphalt binder materials for asphalt roads [3,4]. The models can be categorised as theoretical-based on the principles of heat transfer-or empirical models-based on statistical analysis of the measured environmental factors to determine pavement temperature.…”

Road Pavement, Road Pollution, and Sustainability under Climate Change Increased Temperature

“…Mokoena et al [12] pointed out that pavement temperature relies on more than air temperature-it is determined based on various climatic and weather factors as well as on pavement material properties and the overall pavement structure. Future studies should be performed for distinct types of bitumen used in flexible pavements, as the retention potential can vary with the bitumen type.…”

“…Austroroads [11] considered that the life of bituminous surface treatments will be affected by ambient temperature; the increase in temperature will accelerate the rate of deterioration of seal binders and require earlier surface dressings/reseals, which will lead to higher maintenance costs. Mokoena et al [12] show concern for the global warming and the need to appropriately decide on bituminous road materials for a reliable performance of asphalt roads in South Africa. Fletcher et al [13] used observations, output from global climate models, and a statistical model to evaluate the extreme maximum pavement temperature in 17 major Canadian cities, concluding that for most of the cases there will be a projected increased temperature.…”