Recycled concrete aggregates (RCA), derived from demolishing concrete buildings and pavements, have been treated with significant value as a recycled resource. Using RCA instead of virgin aggregates for pavement construction became a feasible approach to conserve construction trash resources since approximately 140 million tons per year were produced in the United States. This research conducted a life cycle cost analysis of stabilized clay subgrade soils in Kansas, USA, combining with RCA from pavements damaged by freeze-thawcycles and theD-cracks process. Class C fly ash and type II Portland cement were stabilizers for subgrade mixture designs. The performance of the mixtures was evaluated through Standard Proctor, unconfined compression strength (UCS), and California Bearing Ratio (CBR) tests. The full-depth flexible pavements incorporating these stabilized subgrades were designed using the AASHTOW are Pavement ME Design (PME) software. Results indicated that a 1:1 mix of Class C fly ash and type II Portland cement was the most effective stabilizer, decreasing the required thickness of the hot-mix asphalt (HMA) layer. The life cycle cost analysis demonstrated that the RCA-stabilized subgrades are economically viable when the chemical stabilizers are used in equal proportions.

The present study aims to evaluate the possibility of perpetual pavement design with stabilized black cotton soil and polymer-modified bitumen for the major highways in India. Ground granulated blast slag (GGBS) was proposed as a potential material for use in pavements on weak subgrades, with proportions of 10%, 20%, 30%, and 40% added to the black cotton soil. Modified proctor compaction and California bearing ratio tests were conducted to determine the engineering properties of the soil and GGBS mixture. The study also aimed to design a high modulus bituminous concrete mixture for perpetual pavements using a combination of styrene-butadiene-styrene (SBS) polymer and viscosity grade 30 (VG 30) bitumen, with SBS added to the bitumen in amounts ranging from 1 to 4% by total weight. The physical and mechanical properties of both SBS-modified bitumen and neat bitumen were determined. Based on these results, 16 combinations of perpetual pavements were designed using the mechanistic-empirical methodology and according to Indian Road Congress (IRC 37: 2018) guidelines, with the aid of the IITPAVE software. These pavements included both treated and non-treated subgrades, as well as modified and unmodified mixes. The study found that the use of a sturdy foundation, treated subgrade, and high stiffness base materials is crucial in reducing the significant cost associated with using bitumen in a developing and oil-importing country like India. The designed pavements were also compared in terms of cost assessment and carbon dioxide emissions to determine the best option among the proposed combinations.