This paper studies the potential environmental and economic impact of replacing natural aggregates (NA) with recycled aggregates (RA) in the production of different sustainable concrete mixes in the United Arab Emirates (UAE). A life cycle assessment (LCA) was carried out according to the methodology proposed by the international standards of the series ISO 14040. The performance of concrete mixes having a similar design compressive strength was evaluated. Results showed that the inclusion of steel fibers (SF) led to an increase in the global warming potential (GWP), whereas mixes with cement replacement by fly ash, slag, or microsilica recorded a reduction in GWP. Furthermore, SF-reinforced mixes created with 100% RA were at least three times more expensive than the NA-based control mix, while the cost of those with cement replacement by mineral additives was generally similar to that of the control. Material transportation was found to be a main contributor to the environmental and economic impacts, only second to cement, and its contribution increased with longer distances and steel fiber incorporation and decreased with RA replacement. To integrate these individual measures and select optimum mixes for various applications, multifunctional performance indices were developed. Research findings highlight the possibility to fully replace NA with RA (100%) while maintaining the performance and improving the economic and environmental impacts of concrete produced in the UAE.

Assessing the current levels of greenhouse gas (GHG) emissions from road transportation projects allows for benchmarking and is essential for potential emissions reduction. The objective of this study was to estimate the GHG emissions associated with the construction and operation of three road cases—two primary roads and one secondary road network—in Abu Dhabi, United Arab Emirates. The GHG emissions produced by the study cases were estimated using the RoadCO₂ estimation tool. Results showed that the total emissions (in kg CO₂e/m²/y) range from 76 for the secondary road case to 1100 for the primary road cases. The operation phase is responsible for 94–98% of these emissions; the construction phase is responsible for the rest. Road works contributed the most to GHG emissions during the construction phase. The contribution of the remaining categories of the construction phase fluctuates within a certain case and among the considered cases. The equipment used in the construction phase for the three cases contributed 15–70% of the total phase emissions, while the remaining emissions were due to construction materials. In the operation phase, emissions were mainly generated by vehicle movement. Street lighting also contributed to emissions during the operation phase. On the other hand, the irrigation of planted trees along the road had a very low impact on GHG emissions, and carbon sequestration by these trees had a negligible effect in terms of acting as a carbon sink. The results obtained from this study were compared with other cases reported in the literature.

Research on self-healing concrete has flourished in recent years. This paper aims to comprehensively understand the current research situation and future development directions of self-healing concrete. It summarizes and analyzes the publications on self-healing concrete from 1974 to 2021 to reveal the current key research topics and development trends and identifies the most productive research constitutes. The bibliometric analysis software Biblioshiny was used to analyze 1433 documents written by 2961 authors and published in 450 sources retrieved from Scopus. The analysis included an overview of the leading information and an analysis of the authors, countries, universities/institution, publications, and keywords. Results obtained from the author analysis suggest that tracking the work of the most productive authors is essential, as it will provide researchers with valuable information, such as possible leads and ideas for future research work and collaboration opportunities. Countries, universities/institutes, and publications analysis revealed that more collaboration leads to more exposure and a higher citation rate, significantly promoting self-healing research development. A keywords analysis highlighted the focus areas in self-healing concrete and presented potential gaps in the literature. The findings of this study will provide scholars with a comprehensive understanding of the current research work in the field of self-healing concrete and its future directions. Results can also benefit stakeholders in making effective decisions to direct the development of the self-healing industry.

The transportation sector is considered one of the driving forces behind the increased release of greenhouse gases (GHGs), with road transport being this sector’s main emissions contributor. In turn, efforts should be devoted to reducing emitted GHGs from this sector, and many such opportunities lie in the road transport life cycle. This paper investigated fourteen emission reduction scenarios based on the green initiatives issued by the Abu Dhabi Government. The explored measures are either related to road works and road municipal services or to traffic movement. The proposed measures were evaluated with reference to a baseline study previously reported by the authors for three different road projects in Abu Dhabi city. Findings reveal that normalized GHG emission reduction could be significantly reduced by (i) replacing 30% of internal combustion engine passenger cars with battery electric vehicles where the power demand is covered almost equally from nuclear and liquified natural gas (LNG) sources, (ii) reducing the number of passenger cars by 10%, and (iii) having one-fifth of passenger cars powered by LNG. A lesser significant reduction could be achieved by replacing conventional lamps with light-emitting diode (LED) lamps or by having one-fourth of lighting powered by solar energy. Even lesser reduction could be achieved by (i) replacing a portion of Portland cement with ground granulated blast furnace slag in concrete structures, (ii) fully utilizing treated sewage effluent for roadside-plant irrigation, (iii) reducing desalinated water used for roadside-plant irrigation by 20%, and (iv) increasing the number of higher efficiency passenger cars by 10%. Replacing hot-mix asphalt with warm-mix asphalt and using asphalt with a high stiffness modulus in the base layer results in low emission reduction. The use of 15% recycled asphalt or the use of 50% recycled aggregate in road construction has the least impact on emission reduction. When all explored scenarios were combined, an overall normalized GHG emissions reduction of 9–17% during the road project life cycle could be achieved.

A number of countries have recognized the need to quantify the greenhouse gas (GHG) emissions produced by road transportation. As a result, several estimation tools have been developed during the last decade. However, the available tools do not capture all activities contributing to GHG emissions during the life cycle of road projects. This paper describes the development of a comprehensive web-based tool that can be used to quantify direct and embodied emissions from all activities associated with different phases of road projects. The tool, called RoadCO ₂ , accounts for all possible activities that may be encountered during the pre-construction, construction, operation, maintenance, and rehabilitation phases of a road project. Although RoadCO ₂ currently uses emission factors established by the Intergovernmental Panel on Climate Change (IPCC), the tool has the flexibility to accommodate country-specific emission factors, if available.