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The reuse of reclaimed asphalt material (RAM) and polyethylene terephthalate (PET) plastic waste is a reliable approach to limit the use of virgin aggregates for road construction and mitigate environmental challenges. This study highlights the structural performance of the cementitious base or cement-treated base (CTB) layer by incorporating reclaimed asphalt and plastic waste material. Structural compatibility of CTB layer with different proportions of RAM (20%, 45%, 70% and 95%), virgin aggregates and plastic waste (5%) is recognized by the moisture-density relationship, unconfined compressive, indirect tensile strength, flexural strength and California bearing ratio tests. In the current study, a ranking methodology is used to analyze the overall suitability of the cementitious base mix proportions using different laboratory test parameters. Furthermore, a finite element analysis using the ANSYS software is performed to investigate the effect of CTB layer on the pavement structural responses. Also, using the central public works department guidelines, a cost comparative study is provided. Experimental results showed that all the cementitious base mixes met the requirements for the unconfined compressive strength, except for the 95% and 70% RAM mixes. Therefore, 20%-45% of RAM can partially be used in the CTB layer to replace virgin aggregates partially. The finite element analysis results showed that CTB reduced fatigue strain by 57% and surface deformation by 47%. Moreover, it has been concluded that by utilizing a cementitious base with RAM, there is a 30% cost reduction. KEYWORDS: Reclaimed asphalt material, Cement-treated base, Polyethylene terephthalate, Finite element analysis, Unconfined compressive strength.

Clayey subgrade soils are considered to have a lower bearing capacity, which may develop early pavement failure due to diverse axle loading. To avoid such failure issues, these soils must be treated prior to the beginning of the construction work. In the recent past, soil stabilization with plastic waste has become popular to reduce waste and improve soil behaviour. The current study aimed to use polyethylene terephthalate (PET) waste bottles to improve clayey subgrade soil for pavement construction. The PET fibre content varied between 1% and 5% by weight of the dry soil to investigate its influence on compaction, California bearing ratio (CBR), unconfined compressive strength (UCS), and tri-axial shear strength. The modified soil matrix with PET was further stabilized using Terrasil (0.1%) in order to improve the strength properties of the treated soil with ageing. Overall, the influence of the addition of the PET fibre on the structural behaviour of flexible pavement under diverse axle loading conditions was evaluated using Finite Element (FE) techniques. The pavement model is computationally implemented in ANSYS to study pavement structural behaviour in terms of surface deflection, vertical stress and strain on the subgrade layer, maximum shear strain in the bituminous layer, and tensile strain at the base of the bituminous layer under standard loading and overloading by 1.25 and 1.5 times. The test results indicated that the addition of PET fibres in subgrade soil significantly increases the CBR, UCS, and internal friction angle and decreases the compaction characteristics. The use of PET fibres in subgrade stabilization can result in a significant reduction in pavement thickness. FE analysis results compare pavement rutting performance and show that overloading reduces rutting life.

India is having a road network of about 4.69 million Km with majority of roads as flexible pavement of having black top surface. These black top surfaces are constructed mainly with the use of naturally available local aggregates and asphalt binder, where aggregates are dried and mixed with hot bitumen to produce the Hot Mix Asphalt (HMA). For a given aggregate gradation, the optimum binder content is important and it is estimated by satisfying various mix design parameters. Even designing a bituminous mix to meet the desired requirements of a particular paving project also requires careful selection of the compatible aggregate source, aggregate gradation and bitumen grade to sustain till its design life. Hence, it is essential to understand how aggregate gradation affects the performance of HMA. The present study was taken up with the objective of evaluating the properties of HMA mixtures designed using bituminous concrete (BC)-I gradation and compared with conventional method of gradation used in the field or batch mix plant. For the preparation of bituminous mixes, five types of aggregate gradation (upper limit, mid-point range, fuller-thompson maximum density gradation, HMA plant mix gradation and lower limit aggregate gradation) were used as per the specification of Ministry of Road Transport and Highways (Fifth revision)-2013 and mix design evaluation is done by using Marshall method. By evaluating the volumetric and Marshall properties of the bituminous mixes with five different gradations, results indicate that the performance of mixes made with mid-point of gradation range shows higher stability value than other mixes and the optimum binder content increases form coarser gradation to finer gradation. Finally, a parameter called Gradation ratio (GR) is also evaluated to indicate the type of aggregate grading and to correlate it with various mix design parameters with the variations in aggregate grading.

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