Developing Superpave Bitumen Performance Grade Mapping for Ethiopia: Adapting to Historical and Future Climate Condition
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Date
2023-06
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Addis Ababa University
Abstract
The study aims to adapting a Superpave bitumen specification performance grading system for
Ethiopia, considering historical and future climate conditions. By conducting statistical analysis
and examines the performance characteristics of different bitumen grades across varying
temperatures. Historical climate data from 1990 to 2020, obtained from the Ethiopia National
Metrology Agency, establish the baseline climate conditions. Future climate projections from 2020
to 2100, based on two global climate models (CMIP6) and climate change scenarios (SSP 2(4.5)
and SSP 5(8.5)), are used to assess future conditions and prediction pavement temperature using
SHRP and LTPP models. The findings indicate that, for different reliability level, PG58-10 and
PG64-10 are predominantly required in historical contexts, yet future projections indicate a notable
transition towards PG64-10 and PG70-10, encompassing a larger expanse of the country.
Furthermore, the Afar region and western Ethiopia are projected to necessitate PG76-10 in the
future. A considerable number of locations in Ethiopia mandate one grade increment due to climate
change, exhibiting average percentage increases of 20%, 23%, and 27% for the moderate climate
change scenario SSP2 (4.5), and 44%, 27%, and 35% for hottest climate change scenario SSP5
(8.5) of the study area during 2020-2040, 2040-2070, and 2070-2100, respectively.
Climate change significantly impacts road pavement performance in Ethiopia, resulting in an
overall elevation of grade changes as observed. Specifically, under the SSP5 (8.5) scenario,
Adigrat and Sekota locations experience a two-grade increase. Additionally, t-test is employed to
compare two pavement temperature prediction models, revealing a statistically significant
difference in Superpave bitumen specifications due to the characteristic nature of the models.
However, both models demonstrate effectiveness in predicting pavement performance grade (PG)
and evaluate performance of currently used asphalt grade using DSR-machine with the SHRP PG
determination criteria of penetration-grade fail temperature for pet-grade 40/50(69.29oc unaged
and 71.66 oc for Aged Sample),60/70((68.03oc unaged and 64.52 oc for Aged
Sample),80/100((59.13oc unaged and 59.66 oc for Aged Sample) &85/100(62.35 oc unaged and
61.35 oc )then the recommended PG Grade are PG64,PG64,PG58&PG58 Respectively.
Finally, the study proposes a new performance grading system for Ethiopian roads, considering
future climate conditions. The findings provide valuable insights for policymakers and road
construction companies in Ethiopia
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Keywords
Superior performance Asphalt pavement (Superpave), Long term pavement performances (LTPP), Strategic highway research program (SHRP), performance grade (PG), Coupled Model Intercomparing Project Phase 6 (CMIP6), Shared Socioeconomic Pathway (SSP)