• Energy Research
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[EN] The recently established Sustainable Development Goals recognize the importance of infrastructures for achieving a sustainable future. Along their long-lasting life cycle, infrastructures generate a series of impacts, the reduction of which has been one of the main focus of researchers¿ attention in the past years. The optimization of maintenance intervals of structures, such as bridges, has aroused the attention of the civil engineering sector, since most of the impacts of infrastructures occur during the operational phase. Thus, bridges are currently designed to attend the economic and environmental impacts derived from maintenance activities. However, the social pillar of sustainability is usually neglected in those analyses. Since no universally accepted methodology does yet exist for its consistent evaluation, the social dimension is not effectively included in the life cycle assessments of infrastructures. This communication evaluates the life cycle impacts of alternative concrete bridge deck designs in a maintenance-demanding environment near shore. Reliability-derived maintenance intervals are first optimized by minimizing the economic and environmental impacts. In a second stage of the analysis, the social dimension is included in the optimization process and results are compared. Optimization results from these combined assessments are obtained applying the Multi-Criteria Decision-Making technique AHP-TOPSIS. The present paper demonstrates how the inclusion of the social dimension may lead to different, more sustainability-oriented optimal maintenance strategies. The three-dimensional approach applied here has resulted in other alternatives to be preferred against those derived from the conventional assessment that considers the economic and environmental perspectives. Such finding supports the idea that holistic life cycle assessments are required for sustainable designs of infrastructures and that more efforts are urgently needed to integrate the social dimension in sustainability assessments of structures. The authors acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness, along with FEDER funding (Project: BIA2017-85098-R).

Reinforcing fibers have been widely used to improve physical and mechanical properties of cement-based materials. Most fiber reinforced composites (FRC) involve the use of a single type of fiber to improve cement properties, such as strength or ductility. To additionally improve other parameters, hybridization is required. Another key challenge, in the construction industry, is the implementation of green and sustainable strategies based on reducing raw materials consumption, designing novel structures with enhanced properties and low weight, and developing low environmental impact processes. Different recycled fibers have been used as raw materials to promote circular economy processes and new business opportunities in the cement-based sector. The valuable use of recycled fibers in hybrid FRC has already been proven and they improve both product quality and sustainability, but the generated knowledge is fragmented. This is the first review analyzing the use of recycled fibers in hybrid FRC and the hybridization effect on mechanical properties and workability of FRC. The paper compiles the best results and the optimal combinations of recycled fibers for hybrid FRC to identify key insights and gaps that may define future research to open new application fields for recycled hybrid FRC.

Sustainable design of infrastructures has become a major matter of study since the recent establishment of the Agenda 2030. This paper provides a systematic literature review on the use of multi-criteria decision making techniques used so far for the sustainable design of bridges. Special attention is put as well on how the reviewed studies assess the sustainable performance of bridge designs along their life cycle from the economic, the environmental and the social perspective. Although SAW and AHP are recurrently used in the sustainable assessment of bridges, the analysis of the most recent articles show that the application of TOPSIS and PROMETHEE techniques are gaining increasing relevance for such purpose. Most of the studies focus on the research of the construction and the maintenance stage of bridges. However, a need for further analysis is identified when it comes to the assessment of the impacts resulting from the End of Life cycle stage of bridges from a sustainable point of view. The use of intuitionistic and neutrosophic logic have been detected as emerging alternatives to the fuzzy approach of decision making problems.

Road construction is an activity that involves a large consumption of raw materials, with the consequent high environmental impact. For this reason, various research projects are being developed in which waste is used as a raw material for bituminous mixtures. This avoids the extraction of raw materials, reduces the environmental impact and reduces greenhouse gas emissions. In this research, the incorporation of ladle furnace slag as a filler for continuous grading bituminous mixtures was evaluated. Firstly, the ladle furnace slag was chemically and physically characterised and its suitability for use as a filler was determined in accordance with the regulations. Subsequently, bituminous mixtures were conformed with the slag and also with commercial fillers, calcareous and hornfels, in order to compare the results. Finally, the physical properties, Marshall stability and the effect of water were determined with the immersion–compression test on all families of samples. The results showed that the mixes conformed with ladle furnace slag had higher Marshall stability, less variation due to the effect of water and acceptable physical properties. Consequently, the suitability of utilisation of these slags in bituminous mixtures could be confirmed.

This study conducts a comparative analysis between Chilean and Spanish reality in regard to the recycling of aggregates and their reuse in road works and urban roads. The current situation of both countries was reviewed through different sources of information such as technical and legal regulation, projects and executed works, to then validate them in Chile by way of interviews to various professionals in the field of urban and interurban road construction, as well as others belonging to government bodies. Spain has extensive experience on this issue, as it has a culture of recycling and reusing aggregates that has produced excellent results, a situation which was taken into account to compare it to Chile’s reality. The conclusion is that currently, in Chile, although the existence of recycled aggregate use is known, this is not the case on a technical level for professionals in the sector. It lacks a specific government body that is in charge of this issue and does not have appropriate infrastructure for its treatment. The materials with a promising future within the construction sector are the production of crushed granular bases and the creation of low-resistance concretes, which cannot be used, as laws that regulate them are still being drafted.

Producing limestone powder requires comparably far less energy than the production of ordinary Portland cement (OPC), making it a promising sustainable solution for partial replacement of OPC in concrete. Lower production energy could be translated into lower environmental impact and lower cost, which are two pillars of the sustainability of the resulting concrete. However, the question remains if replacing OPC with larger percentages of limestone powder would compromise the performance of the resulting concrete to a level that surpasses the environmental and economic gains. In order to assess the collective impact of these concretes, a performance-based multi-criteria decision analysis framework, ECO2, is used. For that purpose, 26 experimentally verified, concrete mixtures with and without limestone powder were evaluated through potential application in two types of reinforced concrete (RC) structural elements (slabs and columns) under identical environmental condition. The main results of the research showed a clear environmental advantage of concrete with a reduced OPC content, but the relatively higher superplasticizer amount in some cases could affect the final sustainability performance of the resulting mix. In the case of RC slabs, the best ECO2 score was obtained for concrete containing limestone powder. Mixtures with 200–250 kg of cement per unit volume of concrete had the highest ECO2 score for all the considered criteria. In the second case, due to the nature of the structural performance requirements in columns, the crucial influence of the concrete compressive strength is clear. The obtained results have shown approximately equal sustainability potential of OPC and limestone concretes in vertical elements such as columns. However, it seems that a certain improvement in the design of concrete mixtures with a high limestone powder content could make these competitive in all fields. This work was supported by the Ministry for Education, Science and Technology, Republic of Serbia [grant number TR36017]. Peer Reviewed

Real-time and continuous monitoring through smart sensors is considered to be the evolution of traditional track testing, enabling the earlier detection of the main failure modes that degrade railway tracks. Through carrying out preventive maintenance operations, infrastructure resources may be optimized, leading to smarter and more sustainable infrastructure. For this reason, under the larger goal of creating a synergy with various types of sensors for railway tracks, this article presents a critical review on the different, currently available sensors for smart and continuous monitoring. Specifically, the most appropriate monitoring technologies for each of the main railway track failure modes have been assessed and identified, thus deriving the advantages and capacities of each solution. Furthermore, this review presents some of the main experiences carried out to date in literature by using sensor technologies, such as strain gauges, piezoelectric sensors, fiber-optics, geophones and accelerometers. These technologies have proven to offer appropriate characteristics and accuracy for the continuous monitoring of a railway track’s structural state, being capable of measuring different parameters, such as deflections, deformations, stresses or accelerations that would permit the technical tracking of various forms of degradation.

The use of polyolefin fibre reinforced concrete (PFRC) as an alternative for reducing the reinforcing steel bars employed in reinforced concrete has become real in the past years. This contribution analyses the improvements in sustainability that a change in the aforementioned reinforcement configuration might provide in a flyover bridge. Economic, environmental and social parameters of both possibilities were studied by means of the integrated value model for sustainable assessment. Such model, which acronym is MIVES (Modelo Integrado de Valor para una Evaluación Sostenible, MIVES), is a multi-criteria decision-making method based on the value function concept and the seminars delivered by experts. The results of the MIVES method showed that the use of PFRC in combination with reinforced concrete (RC) has a sustainability index 22% higher. An analysis of the parameters that form this evaluation shows that there are no remarkable differences in the financial costs between the two possibilities studied. Nevertheless, social and environmental aspects provide with a better qualification the option of building a bridge by using PFRC combined with RC.