Public Works Engineering

Flexible pavement structures are very complex systems usually consist of multi-layers with each layer having different properties (elastic modulus and Poisson's ratio). In order to simplify these complex systems for stress and strain calculations, Odemark has developed a method to transform these multi-layer systems into an equivalent one-layer system with equivalent thicknesses but one elastic modulus. This method has been used in many advanced research studies and design methods including the newly developed Mechanistic-Empirical Pavement Design Guide (MEPDG). This paper investigates the accuracy of the Odemark method and presents a methodology to increase its accuracy. A two-layer system with different modular ratios and thicknesses was extensively analyzed. The results showed that a correction factor must be used with Odemark's method in order to produce highly accurate stress and strain results. This correction factor is not constant and depends not only on the modular ratio and the thickness of the layer but also on the depth of interest.

This research work focused on the investigation of the properties of asphalt binder modified with different percentages of nanoclay (NC), and nanosilica. The nanosilica was manufactured from two different sources: silica fume (NSF) and rice husk (NSH). Results showed that, NSF tends to decrease the penetration and increase the softening point temperature (SFT) and rotational viscosity (RV). However, NC content more than 3% was found to increase the penetration and decrease both RV and SFT. Using smaller percentages of NC increased both SFT and RV and decreased the penetration. Up to 3% of NSH exhibited improvement in penetration, SFT, and RV, however slight or no improvement was observed at higher contents. The Dynamic Shear Rheometer (DSR) results showed obvious improvement in the Superpave performance grade. Both NSF and NC were found to improve Marshall stability of the asphalt mixtures.

This paper presents a comprehensive laboratory study for optimization and quantification of the beneficial effects of stabilization of subgrade soils in flexible pavement systems. Two types of Kuwaiti soils, inorganic silt and clayey sand were selected. A total of six different groups stabilizers were added to the two soils. They are, cement, lime, a mixture of cement and polystyrene fibers, a mixture of lime and polystyrene fibers, a mixture of lime and fly ash, and finally a mixture of lime, cement, and fly ash. Unconfined compressive strength tests were performed on all combinations of variable ratios of stabilizers to evaluate the unconfined compressive strength and the moduli of elasticity. It was found that the unconfined compressive strength increases with the increase of the stabilizer content. However, moduli values increased till certain percentage of the stabilizer and then decreased. A procedure is outlined to quantify the beneficial effect of subgrade soils stabilization based on the extension of pavement service life or reduction in the pavement thickness. Based on both methods, It was found that cement content of 7% by weight of soil is the best stabilizing group and the mixture of 7% lime and 15% fly ash is the poorest group amongst the studied groups of stabilizers.

Currently, many countries are facing a dangerous challenge due to the shortage in the virgin materials used in highway construction. This problem increases with time as a result of constructing new roads as well as maintaining the existing road network. In addition, construction costs and oil prices increased tremendously in the last few decades. Thus, reusing old pavement materials in new construction gains the attention of researchers and practitioners. Pavement recycling technology is relatively new in the developed countries, especially in terms of machines availability and successful application of the technique. The main purpose of this research was to investigate the use of reclaimed asphalt pavement (RAP) materials in highway construction in Kuwait and to determine the optimum RAP percentage. A comprehensive experimental laboratory program was designed and conducted. A total of five asphalt mixtures containing different percentages of RAP from old pavements in Kuwait were investigated. Marshall tests were conducted on these mixtures to determine the optimum asphalt content according to Kuwait specifications. Asphalt concrete specimens were then prepared at the optimum asphalt content resulted from Marshall tests to investigate the influence of the percentage of RAP in the mixtures on the cracking and rutting resistance through the indirect tensile test and the wheel tracking test. Results showed that, using up to 25% RAP yields about 3.6% reduction in the optimum asphalt content as well as saving in the virgin aggregate without a significant influence on the mixture performance. Furthermore, using more than 25% RAP in the asphalt concrete mixture yields a significant reduction in the mixture resistance to rutting, cracking, stability and flow.

Reconstruction and Rehabilitation of old asphalt pavements produces a significant amount of asphalt pavements. Pavement recycling is an effective practical way to conserve the diminishing supply of construction materials and to help reduce the cost of preserving the existing pavement network in the country. In the U.S. the asphalt pavement industry recycles approximately 73 million tons of material annually. However, recycling of pavement materials in Egypt as well as many of the developing countries is not practically practiced on a routine basis. This research study addresses the effect of blending reclaimed asphalt pavements (RAP) with virgin aggregate in order to produce a base/subbase material to be used in pavement construction in Egypt.  It also aims at finding the optimum RAP percentage to be added to a virgin aggregate in order to produce a base or subbase quality material with cheaper cost without affecting the pavement performance. In this research study, two types of pavement materials were investigated. The first material is a size 6 aggregate material used extensively in the construction of the base layers of flexible pavements in Egypt. The second material is a reclaimed asphalt pavement (RAP) collected from an old pavement. A total of five different mixtures were prepared using different percentages of the two material types. This research showed that, based on the CBR strength, aggregate blends containing RAP are only suitable to function as a subbase material, if no stabilizer is added. In addition, adding RAP to an aggregate of a base quality produces a mixture with lower dry density and strength. Even small percentages of RAP reduce the mixture strength (based on the CBR) to a subbase quality material. The maximum amount of RAP material to be added to a virgin aggregate of a base quality to produce a subbase material with a minimum CBR of 25% (according to the Egyptian specifications) is 50%. Lastly, a very strong nonlinear relationship between the RAP amount and CBR of a RAP-Aggregate mixture exists.

The dynamic modulus (|E*|) is one of the primary hot-mix asphalt (HMA) material properties required in the Mechanistic–Empirical Pavement Design Guide (MEPDG). It is strongly correlated to pavement performance over a diverse range of traffic and climatic conditions. This study focused on using laboratory measured |E*| data to compare Witczak NCHRP 1-40D with Hirsch E* predictive model. Both models use shear modulus (Gb*) and phase angle () as the binder characterization parameters. Laboratory |E*| tests were conducted on 25 Superpave mixes which were recruited from different ongoing construction projects in the Kingdom of Saudi Arabia (KSA). These mixes contain different modified and virgin binders. Dynamic Shear Rheometer tests (DSR) were conducted on the binders contained in the investigated mixes. The results also showed that Witczak NCHRP 1-40D and Hirsh models yielded highly accurate |E*| values for the investigated mixes. However, both models showed some bias in the predictions. The bias in the predicted |E*| values was slightly lower for Hirsh model compared to Witczak model.

The Mechanistic-Empirical Pavement Design Guide (MEPDG) is an advanced analysis/design tool for flexible and rigid pavements. Various agencies throughout the U.S. have attempted to implement MEPDG and found that local calibration of the performance models is needed. This paper focuses on the calibration of the rutting models in MEPDG for the state of Idaho as a case study. MEPDG predicts the rutting within each layer, as a function of time and traffic repetitions using mechanistic-empirical models. The total predicted rut depth is the sum of rut depth in each individual layer. In this case study, seven projects were selected for the rutting calibration effort. The projects cover a wide range of subgrade strength, traffic levels, climatic conditions, and asphalt concrete (AC) material properties. Required inputs were collected from several sources. MEPDG Level 2 input data was used for the characterization of the AC layers and subgrade soils. For traffic characterization, Idaho statewide Axle Load Spectra (ALS) and number of axles per truck class data were used. All other required inputs were MEPDG level 3. Total rutting values measured at the AC surface at different time intervals for each of the projects were obtained from Idaho Pavement Performance Management Information System (PPMIS). Simulation runs using MEPDG with the nationally calibrated rutting models yielded very high rutting predictions compared to the measured field rutting. Optimization techniques were used to develop local calibration factors for the rutting models. The developed local calibration factors significantly enhanced the MEPDG rutting predictions.

This paper presents the development of a comprehensive materials and traffic database to support the implementation of MEPDG in Idaho. A database covering all hierarchical input levels required by MEPDG for hot-mix-asphalt (HMA) and binders, typical in Idaho, was established. This database was also utilized to validate the prediction accuracy of the current MEPDG NCHRP 1-37A HMA dynamic modulus (E*) model. The model was also calibrated for Idaho mixes. For the unbound materials and subgrade soils, a total of 8233 historical R-value results along with routine material properties were used to develop level 2 unbound material characterization. A simple R-value regression model as a function of the soil plasticity index and percent passing No. 200 U.S. sieve was developed. A resilient modulus (M r) predictive model based on the estimated R-value of the soil and laboratory measured M r values, collected from literature, was also developed. For MEPDG traffic characterization, classification and weight data from 25 weigh-in-motion (WIM) sites in Idaho were analyzed. Site-specific (level 1) axle load spectra (ALS), traffic adjustment factors, and number of axles per truck class were established. The established database will facilitate MEPDG implementation in Idaho. It also provides framework for other agencies trying to implement MEPDG.

Pavements are subject to environmental conditions, which affect the performance of both flexible and rigid pavements. The current flexible pavement design system in Egypt relies primarily on the 1993 American Association of State Highway and Transportation Officials (AASHTO) Design Guide. The method has many limitations. One of the serious limitations is the empirical drainage layer coefficients. These coefficients in addition to the seasonal variation of the roadbed resilient modulus are the only environmental consideration in the method. The newly AASHTO released production version of the Mechanistic-Empirical Pavement Design Guide (MEPDG) which is called AASHTOWare Pavement ME Design was developed to overcome the limitations inherent in the AASHTO 1993 method. Unlike the AASHTO 1993 method, Pavement ME Design method considers the variation in moisture and temperature on the mechanical properties of the pavement layers. Thus, the main objective of this study was to develop the climatic data to facilitate the implementation of Pavement ME Design in Egypt and study its influence on the pavement performance. Pavement ME required climatic data which are the hourly air temperature, precipitation, wind speed, sunshine and relative humidity were collected for 16 climatic locations distributed all over Egypt for four years. The quality of the data was checked and verified and the data was transformed to the format required by the software. A typical flexible pavement section was simulated using the ME design at the 16 different climatic locations and the performance predicted using the ME Design was analyzed. The performance indicators predicted by Pavement ME are rutting, alligator fatigue cracking, longitudinal cracking, thermal cracking, and International Roughness Index (IRI). Results showed that the pavement performance is significantly affected by the change in the climatic data. As expected, for Egypt, the most significant influence was on the predicted rutting of the Asphalt layer.

 Abstract-Recently, media, researchers, and others have brought increased attention to young drivers' risk, hoping to find ways to reduce it. This paper investigated the risk factors of young drivers, who are considered a vulnerable road user group. A questionnaire was carried out among 750 drivers in Mansoura city, Egypt between July and September 2012 aiming to obtain information on demographic factors, drivers' behavior while driving, as well as information on the traffic violations and accident faults. Analysis of the questionnaire results proved that the main reason of young driver involved in road accidents is careless driving. Results of the questionnaire demonstrated that young drivers are more prone than other drivers to negative behavior as well as traffic violations and accidents.

h i g h l i g h t s NCHRP1-37A yielded better E Ã values compared to NCHRP 1-40D model at all binder characterization input levels. NCHRP1-37A E Ã model with Level 3 binder characterization produced the most accurate and the least biased estimates. Because of the hot desert climate in KSA, care should be taken when using such models for E Ã predictions. Keywords: MEPDG AASHTOWare Dynamic Modulus Rutting Temperature Modified binder Witczak DSR Brookfield

This paper focuses on developing two models for subgrade soil characterization for use in the Mechanistic-Empirical Pavement Design Guide (MEPDG). First, a multiple regression model can be used to predict R-value as a function of the soil plasticity index and percent passing No 200 sieve. Second, a Mr predictive model is based on the estimated R-value of the soil. Hence, the models can be used to estimate the Mr value as a Level 2 data input in the MEPDG. For the R-value model development, 8233 records were used from a historical database of Idaho Transportation Department (ITD) laboratory testing on subgrade soils. For the Mr model development, laboratory measured Mr values for different subgrade soils were gathered from literature nationwide. The R-values for these soils were then predicted using the developed R-value model. Hence, a relationship between the Mr and R-value was established. A limited sensitivity analysis was also conducted to address the influence of the material strength upon the predicted distresses by MEPDG.

 Abstract—Recently, media, researchers, and others have brought increased attention to young drivers' risk, hoping to find ways to reduce it. This paper investigated the risk factors of young drivers, who are considered a vulnerable road user group. A questionnaire was carried out among 750 drivers in Mansoura city, Egypt between July and September 2012 aiming to obtain information on demographic factors, drivers' behavior while driving, as well as information on the traffic violations and accident faults. Analysis of the questionnaire results proved that the main reason of young driver involved in road accidents is careless driving. Results of the questionnaire demonstrated that young drivers are more prone than other drivers to negative behavior as well as traffic violations and accidents.

—Traffic congestion extends the travel time leading to increased cost for most people especially business men and stakeholders. More fuel is consumed, which reduces the air quality, decreases the people's health and increases the emissions. In addition, the noise level is increased due to the traffic congestion. Mansoura city is directly affected by this problem due to the large number of private cars on the streets and the lack of efficient public transportation system. The lack of parking spaces make drivers to park incorrectly on the streets or turn back, resulting in further traffic jams. This research paper focused on estimating the direct costs of the traffic congestion in Mansoura city. Field study was conducted on Mansoura city main corridors to measure the geometric design elements, traffic volume, and speeds. Traffic volume was counted over one day and the average vehicle speed was measured during free-flowing and peak periods. These measurements were used for the calculation of travel time delay cost, excess fuel consumption cost, excess emission cost and excess noise cost due to congestion. Moreover, a questionnaire was designed and handed to vehicle drivers and passengers on the studied corridor. The questionnaire focused on travel time, actual congested travel time, fuel consumption and non-recurring travel delay due to crashes and road restrictions. The annual direct traffic congestion cost was estimated to be 150.37 million Egyptian Pounds (EGP) for the studied link.

The electrocoagulation (EC) process has been upgraded using powdered activated carbon (PAC). The conventional EC process has been supported by different concentration of PAC for wastewater treatment that has high concentrations of phosphate and ammonia, under different operational conditions. These operational conditions have included applied voltage (5, 10, and 15 V), retention time, initial total dissolved solids (TDS; 1,000, 2,000, 2,500, and 3,000 mg/L), initial pH value (4.5, 7.0, and 9.0), and PAC concentration (2.5, 5, and 10 g/L). The other operational conditions such as temperature, mixing power, and space between electrodes have been kept constant. It was found that EC supported with PAC has high removal efficiency of phosphate and ammonia reaching 75% and 73%, respectively. Further, the system has shown more stability for decreasing the TDS, pH, power consumption, and applied voltage during the experiment. The experimental results were analyzed and confirmed by Freundlich isotherm.

The removal of lead Pb+2, copper Cu+2 and cadmium Cd+2 from aqueous solutions by alluvial soil (AL) as adsorbent has been investigated in a series of laboratory scale experiments under various operational conditions (solution pH, adsorbent dose, ions concentration and contact time). Characterization of AL has been carried out using infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The surface of AL beads is irregular with many spaces, channels and holes, which are helpful for mass transfer of metal ions into AL soil. The optimum ions removal can be achieved in alkaline solutions. Ions removal efficiency is directly related to contact time and adsorbant dose and inversely related to the initial ions concentration. Ion selectivity on AL followed the order of Pb+2 > Cu+2 > Cd+2. The results confirm that AL can remove heavy metals from wastewater efficiently, which is a cheap and environmentally friendly adsorbent. Langmuir and Freundlich isotherms fit the exper...