Recycled asphalt pavement - fly ash geopolymers as a sustainable pavement base material: Strength and toxic leaching investigations.

The purpose of this study was to investigate the current state of the practice with regard to the use of reclaimed asphalt pavement (RAP) material for road base and subbase applications and the potential for such use by the Virginia Department of Transportation (VDOT). To achieve the objectives of the study, a comprehensive review of the literature was conducted and the current state of the practice by other state departments of transportation was analyzed. The results indicated that the use of RAP in road base and subbase materials is viable and has been implemented by a number of transportation agencies. There seemed to be no major environmental concerns associated with using unbound RAP without chemical stabilization agents. Numerous sources of RAP are available in Virginia. Based on practices adopted by other state transportation agencies, the study recommends that VDOT allow the use of RAP in a road base material on highway construction projects. The study further recommends that the allowable percentage of RAP in a blend be phased in gradually to allow VDOT to gain familiarity with the materials and processes involved. Compaction testing could be performed with current methods while alternative procedures were analyzed for suitability. Once a standard specification has been developed, sites for long-term field studies will be identified to implement further the recommendations stemming from this study. There is a potential for significant economic benefits if RAP is used in base and subbase applications. Approximately 30% in material cost savings could be realized with a 50/50 blend of RAP and virgin aggregate. In addition, this application would likely result in a substantial reduction in the amount of RAP material currently stockpiled in Virginia.

http://www.virginiadot.org/vtrc/main/online_reports/pdf/15-r6.pdf

Feasibility of Reclaimed Asphalt Pavement (RAP) Use As Road Base and Subbase Material

Modern societies make a hard effort to improve the sustainability of resources due to enhanced environmental sensitivities in nowadays. This paper investigates the usability of recycled construction and demolition materials as an alternative to virgin aggregates in geotechnical applications such as the filling. The physical and geotechnical properties of recycled construction and demolition materials were determined by laboratory tests (i.e. sieve test, flatness test, Los Angeles abrasion test, water absorption test, pycnometer test, modified compaction test, California bearing ratio test, unconfined compressive strength test and resilient modulus test) and a comprehensive laboratory evaluation was carried out. Moreover, similar tests were conducted with a type of high-quality virgin aggregate material frequently used in fillings. The results of the tests conducted on construction and demolition materials were compared with results of the tests conducted on both virgin aggregate and different recycled aggregates which are accepted as an alternative to virgin aggregates used in the filling in the literature. Results of the tests conducted on construction and demolition materials were also evaluated according to the limit values in technical specifications of highway administrations of various countries. As a result of this study, it has been concluded that construction and demolition materials can be a good alternative to virgin aggregate used in the filling provided that it is taken measure against excessive water absorption value.

Geotechnical Properties of Recycled Construction and Demolition Materials for Filling Applications

Recycled materials with suitable engineering properties can be used as substitutes for natural aggregates (NA), an economically feasible and environmentally friendly alternative. Various recycled materials such as reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), crushed brick (CB), fine recycled glass (FRG), Steel Slag, waste rock (WR), recycled masonry aggregate (RMA), electrolyte manganese residue (EMR), red mud (RM) and plastic wastes, were used globally in pavement construction. Extensive research is in progress to utilize recycled materials in flexible and rigid pavement bases with and without stabilization. Cement stabilization is widely used among the various stabilization techniques due to the proven process/technology and benefits. The recycled aggregates content, type, cement content, gradation, curing period, and other factors influence the mechanical properties of the cement-treated bases. In the process, there is a need to assess the performance of cement-treated bases at varying percentages of recycled materials to understand the real-time conditions for different climatic conditions. The optimization of the recycled materials and cement is necessary to improve the performance and make the recycled bases economically viable. A detailed review of cement-treated bases using different recycled materials is carried and presented in the current paper. Besides, the indigenous characteristics of various recycled materials with cement stabilization are presented. The extensive literature survey concluded that Cement-treated bases showed better performance than conventional bases in terms of stiffness, strength, economic, environmental, and sustainable perspectives.

Utilization of recycled aggregates in cement-treated bases: a state-of-the-art review

A comprehensive study of recycled concrete aggregates as a drainable base layer for pavements

The increased use of reclaimed asphalt pavement (RAP) materials in road construction has reduced both the amount of construction debris disposed off in urban landfills and the rate of natural resources depletion. However, source-dependent product variability or deficient strength-stiffness characteristics has often limited RAP applications in road bases. These limitations have led to new research efforts aimed at exploring novel, cost effective stabilization methods to treat RAP materials prior to their use in pavement construction. In the present work, a comprehensive series of engineering tests were performed on RAP materials treated with different dosages of Portland type I cement and with alkali-resistant glass fibers. Engineering tests included permeability, leaching, unconfined compression and small-strain shear moduli via resonant column testing. Leaching testing included pH, total and volatile dissolved solids, total and volatile suspended solids, and turbidity. Test results appear to confirm the potential of cement-fiber treated RAP as an environmentally and structurally sound alternative to non-bonded materials for base and sub-base applications in pavement engineering. BACKGROUND Natural aggregates obtained from a variety of source rocks have been traditionally used as road base materials. The extraction of these natural aggregates, however, is increasingly being constrained by urbanization sprawls, increased extraction costs and heightened environmental concerns. The use of reclaimed asphalt pavement (RAP) materials in road construction has been proven to reduce both the rate of depletion of these natural resources and the amount of construction debris disposed off in urban landfills. RAP base materials have also been reported to yield considerable savings in the overall costs of pavement construction projects. A report released by the U.S. Environmental Protection Agency in 1993 has estimated in 73 million tons the amount

C. A. Ordoñez

Papers

Engineering Characterization of Cement-Fiber Treated RAP Aggregates