الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
Mechanistic Empirical (ME) pavement design methods started to gain attention especially the last couple of years in Egypt and the Middle East. One of the challenges facing the spread of these methods in Egypt is lack of advanced properties of local soil and asphalt, which are needed as input data in ME design. Resilient modulus (Mr) for example is an important engineering property for ME design that expresses the elastic behavior of soil/unbound granular materials (UGMs) under cyclic triaxial loading. In order to overcome the scarcity of the resilient modulus data for soil/UGMs in Egypt, a comprehensive laboratorytesting program was conducted to measure resilient modulus of typical UGMs and cohesive subgrade soils used in pavement construction. In addition, the effect of moisture variation of UGMs and subgrade soils on resilient modulus was studied. Moreover, the feasibility of using sodium alginate biopolymer as alternative for traditional additives for treating weak cohesive subgrade soils particularly under repeated triaxial loads for pavement construction applications was investigated. For biotreated subgrade soil, two types of soils (clay and silt), representing typical cohesive soils in the delta region in Egypt, were investigated. The sodium alginate was added to the cohesive soils in the range of 0% to 6% using two different mixing methods (wet and dry). The experimental program included basic engineering tests, resilient modulus and unconfined compressive strength tests, potential hydrogen (PH) along with other chemical tests such as Fourier Transform Infrared Spectroscopy (FTIR) and Thermal Gravimetric Analysis (TGA). In addition, Scanning Electronic Microscope (SEM) images were performed for both untreated and treated soils at different alginate contents. Finally, the factors that affect the resilient modulus of UGMs/soil were reviewed, studied and discussed. The well-known predictive models found in the literature were used to predict resilient modulus for the typical UGMs and subgrade soils. Results showed that the resilient modulus of the treated subgrade soils generally increased with the increase in sodium alginate content up to an optimum value of 2% and 4% for clayey and silty soils, respectively. This significant improvement was reached in the first 4 days of curing with continuous gain of strength up to 28 days. This increase in resilient modulus was found to be dependent on the soil type, alginate concentration, curing time, and treatment method. The micro level tests, TGA, SEM, and FTIR, confirmed the presence of the cementation polymer due to sodium alginate that increased the bond and cross-linking between particles, and consequently an increase in the soil stiffness and strength occurred. Moreover, the effect of moisture variation on the resilient modulus of UGMs and subgrade soils was noticeable. Finally, the well-known models were found to reasonably predict resilient modulus for UGMs and subgrade soils with a prediction accuracy varied from poor to excellent.