Recycled Construction Materials Research Articles

Use of Time–Temperature Superposition and Stepped Isothermal Method for Estimating Long-Term Properties of Recycled Aggregate Roller-Compacted Concrete

Abstract Although the use of recycled materials in civil engineering construction is a desirable option from a sustainability standpoint, the questionable long-term performance of these materials often hinders their widespread use in practice. The primary focus of this study was to perform accelerated aging and testing for estimating long-term properties of a roller-compacted concrete composed of crushed recycled aggregate, Type-I portland cement, and ASTM Class-F fly ash replacing up to 50 % of cement by weight. Accelerated aging was accomplished by curing cylindrical specimens at three different elevated temperature regimes for specific time durations. At the end of each time–temperature regime, the residual stiffness of the specimen was measured in a nondestructive fashion. Series of stiffness–time master curves were then constructed for each mix using the time–temperature superposition (TTS) technique and the stepped isothermal method (SIM). While the TTS method uses different sets of specimens for each elevated time–temperature regime, SIM uses a single set of specimens that are stepped up in temperature and held at each regime for a specified duration. Results indicated that for all mixes, the material stiffness degraded with time. Based on the Arrhenius equation, stiffness–equivalent age master curves were developed. Stiffness prediction was accomplished up to an equivalent age of almost 600 days, although the actual short-term test lasted only up to 6 days. It was also found that SIM and TTS provided comparable results, thus implying that the testing time and the number of specimens can be significantly reduced by using the SIM.

Methodology for the environmental analysis of mortar doped with crumb rubber from end-of-life tires

The construction sector is in a process of improvement towards sustainability. The study of the use of a waste as raw materials is an opportunity. This article aims to evaluate the environmental viability of incorporating recycled crumb rubber from end-of-life tires into a mortar. To this end, a life cycle assessment tool is implemented by applying the EPD methodology to assess the various categories of impact. A series of mortar alternatives were analyzed in which fine aggregate is replaced by a percentage of crumb rubber ranging from 10% to 40%: the proportion increases by 5% in each solution. The scope of the LCA is from cradle to gate as it is during the various stages that the greatest environmental impacts are incurred: including the extraction of raw materials, their transport, as well as the production process. The functional unit is that of producing 1 m3 of mortar. The results obtained in this study show that the primary contributor to environmental impact is the cement production phase. On the other hand, the various alternatives evaluated achieved a 37.04% reduction in emissions of kg of CO2, as well as a 41.83% reduction of abiotic depletion of fossil fuels when 40% of fine aggregate was replaced by crumb rubber. This study also demonstrates that the transport distance of recycled materials from their point of production to the mortar production plant is a decisive factor. Depending on that distance, the proposed solution can be rendered environmentally unviable. On a final note, it is important to underscore that the appropriate use of recycled aggregates in mortar is not only determined by strength but also environmentally. This research generates knowledge about the environmental benefits of using recycled materials in construction.

Evaluating and modeling aggregate loss of Otta seal for low-volume roads

Otta seal has gained significant interest from Iowa road engineers in search of a more economical surface alternative for low-volume road construction, preservation, and rehabilitation. This technology has not been sufficiently studied in the US, with the only available guideline for Otta seal construction based on field experience in Norway. Otta-seal specimens prepared using Iowa local aggregate were investigated in the laboratory by using sweep tests to measure the effect on aggregate loss of aggregate and binder types, application rate calculation method, and gradation. Methods such as Overby, McLeod, and modified McLeod were investigated to determine the optimum rates for both aggregate and binder application, with results indicating that material type variation did not significantly affect the aggregate loss of Otta seal specimens and that aggregate loss in specimens gradually decreased as grading was changed in from dense to open. Recycled aggregates (recycled concrete aggregate and slag) showed satisfactory performance, essentially the same as conventional aggregates, in the sweep tests; this encourages using recycled materials in Otta seal construction, considering the resulting economic and environmental benefits. Among the different methods tested for material application rate, the modified McLeod method produced the lowest aggregate loss for Otta seal specimens. Multiple linear regression (MLR) and artificial neural network (ANN) models for predicting aggregate loss of Otta seal from the ratio of binder to aggregate application rate (BR/AR), gravel content, and uniformity coefficient (Cu) were also developed. The model can be utilized to predict aggregate loss from easy-to-measure material properties.

Effects of material non-linearity on the structural performance of sandwich beams made of recycled PET foam core and PET fiber composite facings: Experimental and analytical studies

This paper presents the results of experimental and analytical studies on sandwich beams subjected to three-point bending beyond their limit of proportionality. The sandwich beams were composed of polyethylene terephthalate (PET) fiber-reinforced polymer (FRP) composite facings and recycled PET (R-PET) foam core made from post-consumer plastic bottles. The study tested three R-PET core densities (70, 80, and 100 kg/m3) and compared the results to a control group with 100 kg/m3 core density and glass FRP facings. The beam geometry and testing set-up were consistent throughout the study, with 12 beams tested in total. The results showed that all specimens exhibited non-linear load–deflection behavior, resulting in developing a non-linear analytical model using decreasing secant elastic and shear moduli under increasing loads. The proposed model was validated, and a parametric analysis was performed to evaluate its mechanical performance under different conditions, including variations in span length and the thickness of the core and facing components. Additionally, the study created a novel failure mode map to predict the failure mechanism of the sandwich panels based on core density and the PET FRP facing thickness to span length ratio, considering the non-linear behavior of both components. As a result, this study provides valuable insights into using recycled materials in construction, contributing to reducing plastic waste and mitigating environmental impact.

Experimental investigation on compressive strength addition of leftover building debris to paver blocks using coir fibre

India is a country under development. Similar to India, other emerging nations also benefit from cost-effective construction methods and affordable building materials for their national development. The building industry generates close to 12 to 14 million tonnes of waste annually, of which roughly 7 to 8 million tonnes are brick and concrete debris. Waste construction material can play a significant role when added to paver blocks. When employed in paver blocks, the waste recycled construction material is cost-effective and long-lasting because of some of its unique features that are applicable to conventional construction materials. After being crushed using a laboratory jaw crusher, this concrete debris can be substituted in two steps for coarse aggregates. In accordance with Indian Standard standards for paver blocks, as a full 100% replacement and a 40% partial replacement. This garbage is either discarded or diverted toward a landfill. The idea of adding concrete scraps to the concrete used to make the interlocking paver blocks with coir fibre is depicted in this study. In comparison to 0.1% and 0.5% coir fibre, the average compressive strength of paving blocks with 0.3% coir fibre produces the best results. Compressive strength, workability, bulk density, specific gravity, flexural strength, splitting tensile strength, and water absorption tests were analysed in order to build paver blocks with coir fire in various percentages by adding leftover construction materials.

Feasibility of Using Recycled Construction and Demolition Materials for Deep Soil Mixing

Reusing construction and demolition wastes for geotechnical and geo-environmental purposes has already become a research hotspot. This study was carried out to evaluate the feasibility of using recycled construction and demolition wastes in a partial substitution of cement to enhance the mechanical properties of soft soil. The strength and stiffness development of two types of recycled material (RM1 and RM2), incorporated with peat and clayey soil under 7, 14, and 28 days’ curing time, was investigated based on unconfined compressive strength and free–free resonance frequency test methods. The findings demonstrated that clayey soil showed an average of 2.5 times higher strength than peat with the addition of recycled materials, regardless of the type. However, after 14 days of curing, the strength remained constant for peat soil. Moreover, it is concluded that the studied granular recycled materials could be used to replace a part of the cement content to improve the strength and stiffness properties.

Use of Waste Building Materials in Architecture and Urban Planning—A Review of Selected Examples

Modern environmental protection standards have a direct impact on the construction and shaping of public space. Designers are increasingly reaching for materials produced via recycling technologies. Waste materials are more readily adopted and used in urban planning and architecture. Current projects in this area are being increasingly designed to meet the requirements of the circular economy, which is facilitated by the reuse of once-used components. The aim of the study is to review research papers in the Scopus database (bibliometric analysis) and other selected materials applied in construction, which are recycled and used again in various ways in the construction of subsequent buildings. The results show various application possibilities of recycled materials in construction. The study draws attention to the fact that the use of recycled materials in modern construction is becoming more and more effective, which may contribute to increasing the share of the circular economy in the implementation process related to this subject.

Advancing Circular Economy in the existing building stock: A methodology to support building characterisation for sustainable refurbishment design

The lack of standard practices and platforms for assessing refurbishment strategies towards Circular Economy (CE) and their impact in global warming constitutes a challenge for the decarbonization of existing building stock. Incorporating data and feedback from designers and practitioners since early design stages is important to feed a multi-criteria dynamic process with multiple dimensions, which must be assessed under a life cycle perspective. To tackle this issue, this paper introduces a new methodology to support the implementation of tailored refurbishment strategies for increased recovery, reuse and recycling of construction materials. The final objective is to build a methodological framework for sustainable refurbishment design in a BIM environment, which aims to facilitate standardized practices in the construction sector, regarding CE, with a positive impact in the mitigation of global warming and the decarbonization of the building stock. To test the development of this methodology, a case study building in Lisbon, corresponding to a 1919 - 1945 archetype is analysed, making use of its BIM model, where BIM standardization criteria and circularity indicators are discussed, in order to be implemented as a Plugin for Circularity.

Analysis of types of technologies for the processing of building materials by carbon footprint indicators

With the increase in the rate of civil construction and the growth of socio-economic development, there is a significant increase in the consumption of construction materials based on natural raw materials, which makes research in the search for an alternative raw material base for the construction industry as a whole relevant. Rational solution in terms of ecology and economy becomes the recycling of construction materials and the use of industrial waste. The trend of using construction waste as aggregates for concrete products and structures, is currently the most effective solution to reduce the negative impact on the environment, and also has a number of economic advantages, when choosing the optimal processing technology. This article considers the state, trends and problems of development of the construction sector of the economy in the direction of energy-efficient technologies and principles of sustainable development that help to reduce the negative impact of the construction sector on the environment in urban conditions. The main reasons for the increased interest in the research of environmentally friendly methods of recycling construction materials are indicated. The characteristics and unique properties of raw materials subjected to various methods of recycling are described. The advantages offered by the innovative system of "green" construction with the introduction of construction waste recycling technologies are given. The authors present an analysis of the most common technologies and methods of recycling concrete scrap into secondary aggregate, as well as the advantages and disadvantages of each method of regeneration of concrete scrap. The experience of researches of innovative methods of recycling concrete in foreign countries, the prospects and problems of further development of "green" technologies in the Russian building industry, and also priorities and prospects for entering the market of domestic producers of concrete products on the basis of secondary aggregate, which will allow to provide decrease in extraction and production of natural raw materials are revealed. Formulated further research directions of the problems of development of green technologies in the construction sector of the economy.

Circular material passports for buildings – Providing a robust methodology for promoting circular buildings

The construction sector is responsible for about 50% of all extracted raw material and for over 35% of the EU’s total waste generation. To transition to a circular construction model, reliable and standardized information on the material composition of buildings is required. A Circular Material Passport (CMP) can organize and store such information. It provides an identity for a certain product and assigns value to it, enabling the recovery of materials by providing information for maintenance, recovery, reuse and recycling. A set of various CMPs can also be turned into a Building Materials Passport. This paper proposes a new structure for a CMP. The new CMP distinguishes itself from previous efforts to define material passports since it is aligned with the EU Level(s) framework of core sustainability indicators for office and residential buildings. This paper, firstly, reviews the relevant indicators from the Level(s) framework. Secondly, analyzes the current barriers in the development and use of material passports and proposes mitigation measure. Thirdly, identifies parameters to provide relevant information to promote circularity in the built environment. Fourthly, summarizes the findings and proposes a new structure for a lean CMP. The proposed CMP structure can be divided into three sections: 1) general data, 2) product context use and location, and 3) circularity potential. It can be concluded that indicators provided by the CMP could have the potential to be used for public procurement, as well as to define building permit criteria and assessment. Moreover, CMPs should be integrated with Building Information Modelling (BIM) and as a support tool for pre-demolition audits for identifying reusable and recyclable construction products and materials. The importance of policy development for the promotion of a standardized and regulated use of this tool needs to be highlighted.

Utilization of CO2 into recycled construction materials: A systematic literature review

Utilization of CO2 into recycled construction materials: A systematic literature review

Life cycle assessment of eco-friendly asphalt pavement involving multi-recycled materials: A comparative study

In this research, a comparative Life Cycle Assessment (LCA) is conducted to evaluate the environmental potential of utilizing multi recycled materials in asphalt pavement construction. These Materials are Reclaimed Asphalt Pavement (RAP), Off-spec Fly Ash (OFA), and a Food Waste Bio-oil (FWBO). A comparative analysis is performed on producing one ton of asphalt mixture considering multiple scenarios, which stem from virgin materials extraction, recycled materials production, transportation, and asphalt mix production. The study analyzed six percentages of RAP replacement to aggregate and asphalt binder , 0%, 15%, 30%, 50%, 80%, and 100% RAP. Moreover, two proposed products substituted 11% virgin asphalt binder by weight in the different mixtures. The first product is the FWBO, which is utilized alone as an asphalt binder rejuvenator with the highest two RAP rate scenarios: 80 and 100%. The second product is a blend of the OFA with the FWBO with a 2:1 ratio, which is evaluated with all the investigated scenarios. After assessing the baseline scenario, two alternative scenarios are investigated. The first alternative is utilizing natural gas to replace the commonly used Heavy Fuel Oil (HFO) in the asphalt mix production process. The second alternative scenario is changing the FWBO extraction technique from Soxhlet to Ultrasonic Assisted-oil Extraction (UAE). Open-LCA software is used for modeling all the investigated scenarios in the light of TRACI v.2.1 impact assessment methodology in this case study. The results show a reduction in environmental impacts with RAP utilization and the new eco-friendly products. Shifting asphalt mix plant fuel to natural gas instead of HFO offers considerable potential environmental benefits. Adopting the UAE as FWBO rejuvenator extraction method showed less energy and solvent consumption than the Soxhlet extraction, resulting in less environmental impacts.

Mechanical properties evaluation of asphalt mixtures with variable contents of reclaimed asphalt pavement (RAP)

This research paper aims to evaluate the performance of hot asphalt mixes containing reclaimed asphalt pavement (RAP) at different percentages. The usage of RAP as a recycled construction material has become a common practice in many countries nowadays. To achieve this objective, experimental tests were conducted on a total of 15 asphalt mixtures prepared with five different contents of asphalt cement, including 3.5, 4, 4.5, 5, and 5.5%. Three Marshall mixes were made for each asphalt content. Following the ASTM standards, Marshall stability and flow tests were performed to determine the optimum asphalt content of each mix tested (i.e., control, 25% RAP, 50% RAP, and 75% RAP mixes, respectively). The results showed an improvement in the stability and flow values with the increase in RAP content. Maximum stability of 15.11 kN was obtained with a 75% RAP mix at 4% asphalt cement content. Notably, as the asphalt content increases, lower air voids values and vice versa, higher voids filled with asphalt were observed for the four tested mixes.

Macro and micro characteristics of eco-friendly fly ash-based geopolymer composites made of different types of recycled sand

The main objective of the present study is to explore alternative recycled sand materials to river sand. Within this context, six different types of recycled sand materials obtained from the recycling of construction materials were considered to be alternatives to the river sand. In producing fly ash-based geopolymer composites, the river sand was substituted with recycled sands. Then, the properties of geopolymer composites in the fresh and hardened states were studied comparatively. In this regard, flow table test, rheology, and fresh unit weight were determined as fresh state properties whereas dry unit weights, flexural and compressive strengths, and ultrasonic pulse velocity performance were determined as hardened state characteristics. In addition, the interfacial transition zone occurring between these sands and geopolymer paste was displayed using the scanning electron microscope technique. In a general perspective, all the investigated characteristics of the geopolymer composites were influenced by substituting the river sand with recycled sands. The flowability of the geopolymer mixtures decreased whereas they performed more viscous behavior when the river sand was replaced with recycled sands. Among the recycled sands, only the sand recycled from basalt tile increased the fresh and dry unit weights of geopolymer composite while the others resulted in decreases. Replacing the river sand with the sands recycled from tiles did not significantly influence the flexural strength, however, the sands recycled from basalt, granite, and marble tiles led to increasing the compressive strength. Regarding the results achieved in the current study, it could be stated that these recycled sands could be utilized in the production of the geopolymer composites in a controlled manner.

Quantitative research on embodied carbon emissions in the design stage: a case study from an educational building in China

ABSTRACT Achieving low carbon emissions in buildings has a critical impact on controlling global greenhouse gas (GHG) emissions. With the boom in educational buildings, especially those with reinforced concrete structures, carbon emissions from such buildings are brought to the fore. Among building carbon emissions, embodied carbon emissions are closely related to building structure and materials. This paper aims to study the embodied carbon emissions of a Chinese educational building in the design stage with a quantitative method – process-based life cycle assessment, summarizing the carbon emission characteristics of construction materials and proposing corresponding optimization methods. The results indicate that local data of emission factors is preferred for calculating the embodied carbon emissions and the number of construction materials could be obtained through design estimates; that embodied carbon emissions from material manufacturing are much higher than those from material transportation; that steel and concrete are the two most carbon-emitting materials in the reinforced concrete frame structure educational building; and that using local and reused materials are the two main low-carbon optimization measures, with carbon emission reduction contribution rates of 19.7% and 80.3%, respectively, which reused and recycled construction materials should be considered a priority in reducing the embodied carbon emissions of buildings.

Performance of DBM mixtures with unmodified and modified binder with RAP

In the recent years, due to increased traffic, pavements are exposed to higher traffic loading and are oppressed to environmental changes. It is necessary to improve the properties of bituminous mixes to sustain the stresses as well as reflecting it as cost-effective. In this connection, modified binders play a vital role in enhancing the properties of asphalt mixtures. As the days pass on, the availability of natural construction materials are depleting at a rapid rate owing to the fact of large scale infrastructural development. With this stand point, it is essential to prevent the natural resources without compromising with the performance of the structure. The only alternative in this regard is use of recycled materials in construction. Thus, in this study, one such recycled waste namely recycled asphaltic pavement (RAP) was considered for the preparation of dense bituminous macadam (DBM). For evaluating the performance of DBM mixes prepared with unmodified and modified binder i.e., VG 30 and CRMB 55 were considered as binders. The processed RAP was varied from 0 to 50% with an interval of 25%. For the performance evaluation, Marshall test and indirect tensile strength (ITS) tests were considered. Marshall specimens were prepared and tested to analyze the volumetric properties of mixes. The bituminous mixes exhibited higher stability in case of modified binders in comparison with the unmodified ones. The indirect tensile strength is found to improve by a factor of 1.11 and 1.69 under unconditioned and conditioned states respectively when the conventional material is replaced by 25% RAP. Also, the moisture sensitivity of the mixture is reduced. Thus, use of RAP offers durable, long lasting and economical pavements.

Indoor Nanoparticle Characterization in Construction Waste Recycling Companies over Time

Building activity is a significant source of atmospheric contamination by ultrafine dust. Cognizant of this fact, those active in the use and recycling of construction materials must be aware of the risks associated with exposure to nanoparticles (NPs) and ultra-fine particles (UFPs), as well as the associated health impacts. This work analyzed NPs and UFPs generated in a small building-material recycling company using high-resolution electron microscopes and X-ray Diffraction. A self-made passive sampler (LSPS) that can obtain particulate samples without physical and morphological changes, especially where there is a suspension of particulate material, was used in this study. A total of 96 particulate samples, using the LSPS for three months in four seasons, were collected during the study. Thus, the dry deposition of the particles, which are considered highly harmful to human health, was found in each of the four seasons of the year. It is suggested that for future research, the toxicological evaluations of the particulates in the construction industry should be investigated through the consideration of measures to control and mitigate the health risks of workers regarding exposure to NPs and UFPs.

The Effect of Waste Plastics on the Ageing Phenomenon of Bituminous Binders and Asphalt Mixtures.

The push for environmental sustainability in the civil engineering industry has resulted in an increased interest in the use of recycled construction materials, with one example being the use of waste plastic for the modification of bituminous binder in asphalt mixtures. Existing research has associated waste plastics with various binder and asphalt mixture performance enhancing properties. However, there is a lack of research on the age-related durability of waste plastic-modified roads. This research compared the effect of commercially available waste plastic binder modifiers on the ageing phenomenon of bituminous binders and asphalt mixtures, to the effect of conventional polymers SBS and EVA, through artificial bituminous binder and asphalt mixture ageing performed in a laboratory. The addition of polymers (both waste and virgin) resulted in an increase in binder stiffness after short-term ageing as the polymer content increased. The effect of the waste plastic on ageing was comparable to the effects associated with the conventional polymers, and it was concluded that the waste plastic binder modified products should be considered sustainable alternatives to standard polymers for bituminous binder and asphalt mixture modification.

Mining the Built Environment: Telling the Story of Urban Mining

Materials are continuously accumulating in the human-built environment since massive amounts of materials are required for building, developing, and maintaining cities. At the end of their life cycles, these materials are considered valuable sources of secondary materials. The increasing construction and demolition waste released from aging stock each year make up the heaviest, most voluminous waste outflow, presenting challenges and opportunities. These material stocks should be utilized and exploited since the reuse and recycling of construction materials would positively impact the natural environment and resource efficiency, leading to sustainable cities within a grander scheme of a circular economy. The exploitation of material stock is known as urban mining. In order to make these materials accessible for future mining, material quantities need to be estimated and extrapolated to regional levels. This demanding task requires a vast knowledge of the existing building stock, which can only be obtained through labor-intensive, time-consuming methodologies or new technologies, such as building information modeling (BIM), geographic information systems (GISs), artificial intelligence (AI), and machine learning. This review paper gives a general overview of the literature body and tracks the evolution of this research field.

Life Cycle Economic and Environmental Impacts of CDW Recycled Aggregates in Roadway Construction and Rehabilitation

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.