Tamer M. Breakah

Effects of Using Accurate Climatic Conditions for Mechanistic-Empirical Pavement Design

The implementation of the new mechanistic-empirical design guide has led to the need for more accurate inputs. One of the most important inputs that affect the performance of the pavement materials is the climatic data. The importance of accurate climatic data is investigated in this case study. Climatic files available with the design guide and ones developed based on historical information for counties in the state of Iowa through the Iowa Environmental Mesonet were used. The climatic files that were interpolated from the data available within the design guide predicted higher rutting (both total and asphalt cement layer) for the northern part of the state, lower thermal cracking, and lower international roughness index compared to the files developed in this study. Statistical analysis showed that the results calculated using both groups are different.

Predicted performance of hot mix asphalt modified with nano-montmorillonite and nano-silicon dioxide based on Egyptian conditions

ABSTRACT This paper focused on predicting the performance of asphalt mixes modified with nano-montmorillonite (NMMT) and nano silicon dioxide (NSD) using the Quality-Related Specifications Software (QRSS), which is a simplification to the Pavement ME Design. The nanomaterials were thoroughly mixed with the binder at a temperature of 145 ± 5°C. The conventional and the rheological properties were determined for the penetration grade 60–70 control binder as well as binders modified by 3, 5 and 7% of NMMT and NSD by the weight of asphalt. The optimum nanomaterial content was found for each modifier and was then used for preparing asphalt mixtures by the conventional Marshall method. Finally, Witczak 1-40D complex shear modulus (G*) based predictive model was used to estimate the dynamic modulus (E*) for the control and nanomodified asphalt mixtures. The field performance in terms of asphalt concrete (AC) layer rutting and fatigue cracking was predicted using the QRSS software for two typical pavement sections and three different climatic locations in Egypt (Alexandria, Cairo and Aswan). The simulation runs revealed that both nanomodified asphalt mixtures exhibited superior pavement performance in terms of AC rutting compared to the control mix without a significant effect on fatigue life.

Preliminary evaluation of the materials in Egypt for Superpave implementation

The Egyptian code of practice for the design of asphalt mixtures is based on Marshall mix design methodology. There is a significant shift to Superpave mix design worldwide and Egypt is one of the countries that is expected to follow this shift. For the transition to be smooth and easy for practitioners, an analysis was done to evaluate the compliance of the gradation bands available in the current Egyptian code of practice to Superpave requirements. This showed that only a few of the gradation bands could still be used with Superpave mix design, and these only with some considerations. Four gradations were developed from two of the gradation bands, and these mixes were designed using both Superpave and Marshall mix design methods. The Superpave mix design samples were tested for stability and flow. A comparison was made between both designs. The results showed that Superpave mix design yielded lower optimum binder content and that its samples had higher values of stability and flow.