١Mohanad M. Alfa, ٢Hassan T. Abdelwahab.,٣ Nagwa F. Ghaly, ٤Magdy S. Noureldein,
١,2,4 Public Works Department, Faculty of Engineering, Cairo University, Giza, Egypt
3Asphalt and Polymer Service Center, Egyptian Petroleum Research Institute, Cairo, Egypt
Natural asphalt exists in Syria in Al-Beshery and Kefria quarries. The use of this natural
asphalt is currently limited to low-volume roads in which the raw asphalt mix is crushed and
laid down in layers, to act as a low-quality surface dressing. The ability to utilize this natural
asphalt resource is a major challenge to reduce highway construction cost without scarifying
pavements’ quality. This naturally occurring material consists of a mix of sand and asphalt.
The percentage of asphalt cement in this mix is between 15 and 22% of total weight.
This research covers evaluating the performance of bituminous hot concrete mixtures
designed using Syrian natural asphalt. The main objective is to use locally available material
to prepare a high-quality asphalt paving mixture. The designed mix consists of natural
asphalt and coarse aggregates.
Results of the laboratory tests on Al-Beshery raw material showed that the bitumen content is
around 18%. Physical properties of the extracted asphalt, such as penetration and viscosity,
were also determined. Results indicated the hardness and stiffness of the natural asphalt
cement as compared to the commonly used 60-70 penetration-grade refined asphalt.
Trial specimens were prepared utilizing the natural sand-asphalt mix ‘as is’ at different
compaction levels. Results showed that this natural mix cannot be used alone in highway
construction due to lack of necessary stability. Therefore, the next stage of the research was to
improve the performance of natural asphalt mixes by adding local aggregates to satisfy
specification requirements of hot-mix asphalt concrete pavements. Crushed dolomite was
mixed with the natural sand-asphalt mix to meet the requirements of the standard Egyptian 4-
C and 2-C gradation limits for bituminous wearing surface and binder layers, respectively.
Performance of designed mixtures was measured under static and dynamic loading. Marshall
stability and flow, and wheel track tests were all utilized to measure the different properties of
the designed asphalt concrete mixtures. Results showed significant improvements in mix
properties as compared to the base case (the natural sand-asphalt mix alone).