Transportation infrastructure is one of the largest consumers of natural materials. To improve the environmental quality and sustainable development of transportation infrastructure, it is important to implement sustainable strategies in pavement construction and rehabilitation. The use of recycled materials is a key element in generating sustainable pavement designs to save natural resources, reduce energy, greenhouse gas emissions, and costs. The objective of this study was to propose a methodology for assessing the environmental and economic life-cycle benefits when using recycled asphalt pavement (RAP) materials in highway projects. Previous studies on life cycle analysis (LCA) using RAP focused on the economics and/or environmental impacts during the material production process. Thus, there is a need to consider sustainability analysis at all stages of construction and rehabilitation during the performance period of pavement structures. This study addresses this need with the proposed methodology. The suggested approach could be potentially implemented in a pavement management system (PMS) so as to introduce sustainability principles in optimizing alternative rehabilitation strategies. The methodology includes various steps for the analysis, starting with condition assessment of the existing highway, identifying alternative structural pavement designs, predicting service life, setting up alternative rehabilitation strategies, and conducting life cycle environmental and economic analysis. To demonstrate the value of the methodology, a comparative parametric study was conducted on two real case study projects representing actual field conditions for primary roads in Maryland. These case studies were used in order to quantify the economic savings and environmental benefits of using different levels of RAP in highway rehabilitation. The results of the analysis indicate that incorporating RAP in pavement rehabilitation can contribute substantially to cost savings and environmental impact reduction (e.g., greenhouse gas emission, energy, water, and hazardous waste). The benefits illustrated in this study are expected to encourage wide adoption of the proposed methodology and the use of recycled materials in highway construction and rehabilitation. The methodology is transferable where similar materials and highway construction techniques are used.

The use of recycled materials in roadway construction and rehabilitation can achieve significant benefits in saving natural resources, reducing energy, greenhouse gas emissions and costs. Construction and demolition waste (CDW) recycled aggregate as an alternative to natural one can enhance sustainability benefits in roadway infrastructure. The objective of this study was to quantitatively assess the life cycle economic and environmental benefits when alternative stabilized-CDW aggregates are used in pavement construction. Comparative analysis was conducted on a pavement project representative of typical construction practices in northern Italy so as to quantify such benefits. The proposed alternative sustainable construction strategies considered CDW aggregates stabilized with both cement and cement kiln dust (CKD) for the base layer of the roadway. The life cycle assessment results indicate that using CDW aggregate stabilized with CKD results in considerable cost savings and environmental benefits due to (i) lower energy consumption and emissions generation during material processing and (ii) reduction in landfill disposal. The benefits illustrated in this analysis should encourage the wider adoption of stabilized CDW aggregate in roadway construction and rehabilitation. In terms of transferability, the analysis approach suggested in this study can be used to assess the economic and environmental benefits of these and other recycled materials in roadway infrastructure elsewhere.

Concrete production consumes enormous amounts of fossil fuels, raw materials, and is energy intensive. Therefore, scientific research is being conducted worldwide regarding the possibility of using by-products in the production of concrete. The objective is not only to identify substitutes for cement clinker, but also to identify materials that can be used as aggregate in mortar and concrete productions. Among the potential alternative materials that can be used in cement composite production is rock dust of different geological origin. However, some adversarial effects may be encountered when using rock dust regarding the properties and durability of mortars and concrete. Therefore, comprehensive research is needed to evaluate the adequacy of rock dust use in cementitious composite production. This paper presents a comprehensive review of the scientific findings from past studies concerning the use of various geological origins of rock dust in the production of mortars and concrete. The influence of rock dust as a replacement of fine aggregates on cementitious composites was analyzed and evaluated. In this assessment and review, fresh concrete and mortar properties, i.e., workability, segregation, and bleeding, mechanical properties, and the durability of hardened concrete and mortar were considered.

Due to the depletion of natural aggregates and high maintenance cost of highway systems, developing sustainable asphalt concrete (AC) mixes that use waste materials instead of virgin raw materials is necessary. A large amount of waste glass material is globally generated per year that could be beneficial to sustain the asphalt industry. In this context, the present paper evaluates the properties and performance of AC mixtures that utilize crushed waste glass as a replacement material of filler aggregates. Three AC mixes with percentages of filler replacement in the range from 0%, 25%, to 50% were fabricated. Complex modulus testing was performed to evaluate the dynamic modulus |E*| and phase angle δ over a range of temperatures and loading frequencies. In addition, the flow number (FN) test was conducted to assess the rutting potential of the mixtures. The results showed that the mix containing 25% of crushed glass is likely to better resist fatigue cracking; however, the inclusion of glass in the AC reduced the rutting resistance compared to conventional hot mix asphalt (HMA). Finally, the results of the flow number test and the simple performance indicators were compared and used to rank the mechanical performance of the various mixtures.

In the current trend of sustainability, the concrete community has been aggressively looking into adopting green construction material practices and at the same time improving concrete quality and performance for extensive service life and adaptive reuse. Concrete is the construction material most used in the world, with an estimated yearly production of 2.35 billion tons worldwide. In the United States, it is estimated that on average approximately 5% of the ready-mix concrete produced is unused and returned to the plant with only a small portion reused. Such a material when further processed, identified as crushed returned concrete aggregate (CCA), has a significant residual value because among other things it is free of contaminants and has better quality than recycled concrete aggregate (RCA). The objective of this study was to assess the shrinkage behavior of CCA concrete mixtures produced with aggregate from returned concrete. The aggregate was prepared from concrete of different strength. The virgin aggregate (stone) was replaced either partially or at 100% level in the concrete mixtures. The response of the hyperbolic shrinkage prediction model was examined, and based on the experimental results an alternative model is proposed. The proposed model and methodology can be used to estimate the drying shrinkage of CCA mixtures, and eventually can be adopted for assessing the shrinkage behavior of these concrete mixtures in other regions.