Papers by Eman Mousa
Transportation Geotechnics, 2020
The application of reclaimed asphalt pavement (RAP) has become a common practice in road construc... more The application of reclaimed asphalt pavement (RAP) has become a common practice in road construction as a substitute to natural aggregate. The significance of RAP amount on the resilient modulus behavior, shear strength and hydraulic conductivity characteristics of unbound granular base materials were investigated in this research. RAP was blended with crushed aggregate by different percentages ranging from 0% to 100% by the blend weight. The laboratory testing program includes modified compaction, California Bearing Ratio (CBR), permeability, and repeated and static triaxial tests. A descriptive statistical analysis was conducted on all testing results. Furthermore, the X-ray computed tomography (CT) scanning technique was applied to investigate the internal (micro) structure of specimens. It was noted that with the addition of more RAP to the blend the resilient modulus increased and the coefficient of permeability decreased. The apparent cohesion of the RAP blends increased almost linearly and the friction angle decreased as the RAP replacement level increased. The CT scanning results indicated that the virgin crushed aggregate has a higher void ratio than the RAP blends, which interpreted the lower permeability and higher resilient modulus of RAP blends. In conclusion, blending RAP with virgin aggregate produces superior quality material for road bases.
Innovative Infrastructure Solutions, 2020
This research presents the prediction of pavement performance constructed with base layer consist... more This research presents the prediction of pavement performance constructed with base layer consisting of reclaimed asphalt pavement (RAP)/virgin aggregate blends. The prediction was made by the Multi-Layer Elastic Analysis software (KENLAYER) in terms of horizontal tensile strain at the bottom of AC layer and the vertical resilient strain at critical locations within the pavement system. The dynamic modulus |E*| for the hot mix asphalt was estimated by using the quality-related specifications software considering three different climatic conditions and two levels of design speeds. Finally, total pavement rutting and fatigue cracking were determined using the critical strains computed by the Multi-Layer Elastic Analysis along with the Mechanistic Empirical Pavement Design Guide performance models and transfer functions. In general, the RAP blends showed superior/comparable performance compared to natural aggregates for the application in base/subbase layers for the Egyptian conditions. The effect of the rate of loading and climate conditions was significant on both asphalt concrete layer fatigue cracking and rutting.
International Journal of Pavement Engineering, 2020
Currently, Egypt is using the AASHTO 1993 guide for the flexible pavement structural design. In t... more Currently, Egypt is using the AASHTO 1993 guide for the flexible pavement structural design. In this method, as well as the current available Mechanistic–Empirical Pavement Design methods, the resilient modulus (MR) of the unbound granular base/subbase materials and subgrade soils is a measure of material stiffness used for characterization. For pavement structural design, MR of the unbound materials is considered one of the major factors affecting the calculated pavement layer thicknesses, which are crucial for pavement performance over the service life. However, in Egypt, California Bearing Ratio (CBR) test is the main strength test used for the quality control and characterization of the unbound granular materials and subgrade soils due to its availability and simplicity. In this research, a comprehensive experimental testing program was conducted on different unbound granular base/subbase materials typically used in pavement construction projects in Egypt. The testing program includes MR, CBR, and the basic material properties such as gradation, specific gravity, Atterberg limits, Los Angles Abrasion and absorption. The effect of aggregate gradation on the resilient modulus is investigated. A model predicting MR as a function of the index material properties is proposed. The MR–CBR relationship adopted in the current Egyptian Code of Practice for urban and rural roads is verified based on the results of testing program. The experimental data warranted the calibration of the current model. The calibrated MR–CBR model has reasonable goodness of fit statistics and yields rational MR estimates for the local materials.
Canadian Journal of Civil Engineering, 2017
This paper presents the engineering characteristics of reclaimed asphalt pavement (RAP), blended ... more This paper presents the engineering characteristics of reclaimed asphalt pavement (RAP), blended with virgin aggregate for unbound base and subbase layers. The proportions of RAP were 0%, 20%, 60%, 80%, and 100% by total mass of the blend. The experimental laboratory testing included index properties such as gradation, modified Proctor compaction, California Bearing Ratio, and hydraulic conductivity. Repeated load resilient modulus testing was conducted on the blends. The impact of load duration on resilient modulus was also investigated. A strong inverse trend was found between resilient modulus and California Bearing Ratio. An accurate model was proposed for the prediction of the resilient modulus as a function of stress state and reclaimed asphalt pavement percentage with coefficient of determination of 0.94. Finally, multilayer elastic analysis of typical pavement sections with the base layer constructed of virgin aggregate and reclaimed asphalt pavement blends showed good performance.
Thesis Chapters by Eman Mousa
Reclaimed asphalt pavement (RAP) is the most abundant and available material with great potential... more Reclaimed asphalt pavement (RAP) is the most abundant and available material with great potential to substitute natural aggregate, especially in Egypt. The Egyptian market produces approximately 4 million tons of RAP per year. The use of RAP into new construction provides a way to reduce waste disposal loads sent to landfills, extend the life of natural resources, and protects the environment. In this study, the performance of RAP blended with virgin aggregate was evaluated for use as unbound base/subbase layers in paved and unpaved roads in Egypt. The proportions of the RAP blends were 0%, 20%, 60%, 80% and 100% by total mass of the blend. The experimental testing program consisted of index and advanced tests. The index tests included the particle size distribution (PSD), specific gravity, water absorption, Los Angles Abrasion (LAA), Atterberg limits, modified Proctor compaction, CBR, Potential of Hydrogen (pH) and hydraulic conductivity. The advanced tests included the repeated load resilient modulus (Mr) test, the static triaxial shear strength test and X-Ray Computed Tomography (CT) scanning for the investigation of engineering behavior of the blends under traffic loads. Based on the testing results, the basic properties were found to meet the requirements of the current Egyptian specifications for UGMs for base and subbase. Based on CBR results, RAP up to 60% can be used in road subbase construction in Egypt. However, only up to 20% RAP could be used in road base construction. It was indicated that the CBR and the hydraulic conductivity decrease with the increase of the RAP percentage. However, an increase in Mr was noted with the increase of the RAP percentage. Based on X-Ray CT scanning, lower air voids value was detected for blends containing higher RAP percentage, which might be one of the reasons leading to higher resilient modulus and lower permeability. Two models were developed for Mr prediction based on the universal model with a single set of constants for all blends. The first model predicts Mr as a function of the stress state and RAP amount with R2 of 0.94. While the second model was developed for Mr prediction for all blends taking into account the load duration with R2 of 0.92. An Mr – CBR model for RAP blends was developed which yielded R2 of 0.93. Then pavement performance was predicted using the multi-layer elastic analysis (MLEA) software (KENLAYER) in terms of horizontal tensile strain at the bottom of the asphalt layer and the vertical resilient strain at the critical locations. The dynamic modulus (E*) of the Hot Mix Asphalt (HMA) was predicted by the Quality-Related Specifications Software (QRSS) at three different climatic conditions; Alexandria, Cairo and Aswan and two levels of design speeds of 10 and 50 mph (16 and 80 km/hr). Finally, the total pavement rutting and HMA fatigue cracking were estimated using multilayer elastic analysis along with the Mechanistic-Empirical Pavement Design Guide (MEPDG) performance models and transfer functions. In general, RAP blends showed superior/comparable performance compared to virgin aggregates as base/subbase layers for paved and unpaved roads. A simple comparative economic analysis was conducted. These analyses conducted in this research confirm the validity and economic benefits of RAP as a base/subbase material in pavement construction.
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Papers by Eman Mousa
Thesis Chapters by Eman Mousa