Construction And Demolition Waste Research Articles

Mechanical properties of synthetic aggregate pelletized by waste concrete fines in Vietnam

Due to rapid industrialization and economic growth, the generation of construction and demolition waste (CDW) from the activities of demolishing buildings is increasing in Vietnam. The Vietnamese Government has regulations on recycling and collecting CDW for reuse, recycling to environmental protection through Circular No. 08/2017/TT-BXD in 2017, and Directive 41/CT-TTg in 2020. Waste concrete fines (WCF) are generated during demolishing process or crushing of CDW materials. To save natural resources and increase the recycling rate, a disc pelleting technology has been used to recycle WCF. The pellet machine has a disk with 1.5m of diameter and 0.3m of depth; tilted at an angle of 55 degrees and the rotation speed from 15 to 22 rpm; the capacity is 0.5 to 0.8 tons per hour. This paper presents the results of pelletizing WCF research to produce synthetic aggregate (SA). The SA pelletized by WCF and cement had an apparent specific gravity of 2.45 – 2.55 g/cm3, a dry bulk specific gravity of 1.85 – 1.95 g/cm3, a crushing value of 19.2 – 29.9%, a LA (Los Angeles) value of 23 – 33% and water absorption around 13.2%. The mechanical properties of SA meet the requirement of TCVN 11969:2018, recycled aggregate type II for concrete.

A comprehensive model for quantifying construction waste in high-rise buildings in India.

The construction industry plays a vital role in the economic development of any country. Concurrently, the sector also generates enormous quantities of construction and demolition waste (CDW) that damages the ecology causing environmental pollution and deteriorating human health. Recently, various governments and other organizations realized the importance of implementing construction waste management (CWM) practices to attain sustainability in construction. The current decade can be called a pathway for achieving the 2030 agenda for sustainable development goals in which CWM plays an inevitable role. However, accurately quantifying construction waste is necessary to successfully implement any CDW management plan. A detailed literature review for the current research revealed that limited information on the magnitude of construction waste is available in India. Therefore, the current paper proposes a practically viable model to estimate the waste generation index (construction waste generated per total floor area) of high-rise residential buildings in India. The waste quantification is being done based on the project documents and expert interviews. The methodology is later validated through a high-rise building with G + 18 stories located in Kerala, India. The study indicated that a high-rise concrete framed structure generates 122.3 kg m-2 of waste during construction. It was also noted that, concrete, aggregates and blocks constitute 92% of the total waste generated in the project. The developed model can also be used as a cornerstone for establishing a construction waste database at the regional level.

Evaluating carbon emissions of construction and demolition waste in building energy retrofit projects

Building energy retrofit (BER) is one of the priority tasks of China's ‘14th Five-Year Building Energy Efficiency and Green Building Development Plan’. The number of BER projects has dramatically increased in recent years in China, studies related to the management of construction and demolition waste (CDW) from BER projects have not kept pace. There is a need for more related studies, particularly for evaluating and mitigating the environmental impact of CDW from BER projects. This study aims to evaluate and mitigate carbon emissions from CDW of BER projects using a system dynamics (SD) approach through a case study BER project in the urban area of China. The SD model developed for this study includes sub-models for evaluating carbon emissions from the dismantlement of old components and the retrofit construction. Three scenarios were developed and the scenario analysis results reveal that the carbon emissions of CDW from the dismantlement of the old components account for higher carbon emissions than retrofit construction. Improving the inert waste recycling rate from 50% to 90% could save 2034.43 kg CO2 eq carbon emissions. Reducing 50% of CDW in BER construction could save 7673.06 kg CO2 eq carbon emissions. Improving WTE incineration rate from 50% to 100% could save another 50.53% of carbon emissions from the combustible waste. The SD simulation model provides a dynamic and non-linear scenario analysis platform for decision-makers to analyze the carbon emissions for managing CDW from BER projects.

End-of-Waste Criteria of the Bauxite Red Mud

The main objective of this document is to present the End-of-Waste (EoW) criteria for the bauxite red mud. EoW criteria are based on the different EoW approaches and criteria existing around the European Union (EU), especially for Construction and Demolition Waste (CDW) and the results obtained in the CINDERELA project (EU contr. No. 776751). This EoW criteria protocol could facilitate the recycling process of bauxite red mud thus guiding Republic of Montenegro to implement EoW criteria for this waste, which is landfilled in huge quantity (8 million tonnes) near Podgorica. This document will define the product status, its technical quality and applicability as well as its environmental and human health issues.

Analyzing the Performance of Construction Demolition Waste Aggregates on strength for Non-structural Concrete

Construction and demolition waste (CDW) refers to the waste generated from demolished structures in the construction industry. This waste can include concrete and brick materials. In this study, the focus is on evaluating the physical and mechanical properties of coarse aggregates derived from CDW, as well as the compressive strength of non-structural concrete made by mixing CDW aggregates with natural aggregates (NA) in different proportions. The study involved preparing different mix proportions of concrete using various combinations of CDW coarse aggregates, natural coarse aggregates, and brick aggregates. The mix proportions were categorized into three groups:100% natural coarse aggregate,CDW concrete coarse aggregate mixed with natural aggregate in three proportions: (90% NA, 10% CA), (80% NA, 20% CA), and (60% NA, 40% CA) and Mixtures of natural coarse aggregate, CDW concrete aggregate, and brick aggregate in four proportions: (90% NA, 5% CA, 5% BA), (80% NA, 10% CA, 10% BA), (60% NA, 20% CA, 20% BA), and (80% NA, 30% CA, 30% BA). The physical and mechanical properties of the different mix proportions were analyzed, and it was found that all proportions, except (80% NA, 30% CA, 30% BA), met the specified limits. In terms of compressive strength, the concrete mixture with a proportion of (90% NA, 10% CA) exhibited the highest value (27.04 MPa), while the mixture with a proportion of (60% NA, 20% CA, 20% BA) had the lowest value (17.19 MPa). The mixture with a proportion of (80% NA, 30% CA, 30% BA) did not meet the targeted strength of 15 MPa. Conclusion: Based on the analysis of the test results, it can be suggested that CDW aggregates can be used as a replacement for natural aggregates up to a maximum of 40%. Additionally, a combination of CDW concrete and brick aggregates in equal proportions (20% - 20%) can be used as a replacement for natural aggregates to achieve a concrete strength of 15 MPa.

Environmental feasibility of recycling construction and demolition waste

AbstractConstruction, demolition, and renovation activities generate a significant amount of waste, posing serious environmental risks. The scarcity of recycling facilities makes it difficult to implement the new legislation, which calls for producing recycled aggregates. Moreover, the lack of studies on the environmental feasibility of recycling construction and demolition waste in regions with plentiful natural resources of aggregates is a contributing factor to this scarcity. Therefore, this paper studies the environmental feasibility of establishing a construction and demolition waste (CDW) recycling plant. A case study approach compares the CDW recycling process against the traditional quarrying process for generating aggregates. The lifecycle assessment method is used for evaluating both scenarios. Contribution analysis is performed to infer the factors influencing the viability of the recycling process. Thereafter, a sensitivity analysis is conducted to determine the suitability of the proposed location for the recycling facility. As revealed by the single score, the recycling alternative has a 23% more negative environmental impact than quarrying. Nevertheless, there is a chance that the recycling process could be environmentally advantageous. Findings indicated that a total travel distance of 70 km between the demolition site and the construction site is recommended to guarantee environmental feasibility. The transportation distance is found to be the most critical element influencing the environmental feasibility of recycling CDW. The findings of this study help the decision-makers in environmental affairs to consider the influencing factors when constructing a CDW recycling plant.

The effects of different production parameters (NaOH concentration, curing regime and replacement ratio of recycled aggregate) on fresh, hardened and elevated temperature performance of geopolymer mortar samples

This paper presents the findings of objective to examine the effects of construction and demolition wastes (CDW) as fine aggregate on the performance of geopolymer mortar (GPM) specimens. In order to examine the effect of NaOH concentration on the performance of GPM samples, NaOH solutions with 3 different concentrations (8, 10 and 12 M) were prepared. GPM samples, in which the fine aggregate part was formed by replace of natural aggregate (NA) and CDW at three different ratios (0%, 50% and 100%), were cured in water and ambient conditions for 7 and 28 days. The alkali liquid/binder ratio was not determined as a variable and was kept constant at 0.6 for all GPM samples. Subsequently, compressive strength, workability, water absorption, unit weight and high temperature performance on GPM specimens were investigated in detail. All of these experimental parameters were also supported by microstructural analysis (scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR)). The results showed that the compressive strength values of granulated blast furnace slag (GBFS) based GPM samples can be increased up to 105% in case of choosing of water curing instead of curing in ambient conditions. It was determined that the increase in NaOH concentration decreased the compressive strength values of GPM samples. Furthermore, experimental findings revealed that although CDW had a negative impact on the performance of GPM samples, it could still find potential usage area in the geopolymer production. On the other hand, the increases in NaOH concentration and CDW usage ratio led to decreased workability of GPM samples. Finally, it was underlined that the mechanical and physical characteristics of GPM samples decreased sharply with the increasing elevated temperature values (especially at 750 °C).

The Use of Construction Waste to Remediate a Thermally Active Spoil Heap

This article presents the results of experimental research on the possible use of construction and demolition waste (CDW) to improve the properties of unburnt tailings originating from the thermally active spoil heap in Heřmanice (Ostrava, Czech Republic). Mining activity anywhere in the world generally entails a lot of negative impacts on the environment, which are of a long-term nature. One of the most pressing challenges in the remediation of the consequences of mining activity is the thermal activity of spoil heaps associated with the high acidity of the tailings. Active acidity (pH/H2O), exchangeable acidity (pH/CaCl2), hydrolytic acidity (Ha), and elemental composition of tailings and CDW have been monitored. Based on an acidity study, it has been proven that compared to burnt tailings (pH/H2O = 8.4, pH/CaCl2 = 8.9 and Ha = 1.4 mmol kg−1), unburnt tailings show acidic properties (pH/H2O = 3.7, pH/CaCl2 = 3.6 and Ha = 205 mmol kg−1). The bioavailability of two selected potentially toxic elements (PTEs), namely Al and Fe, was examined based on the elemental composition. BCR sequential extraction analysis was used to determine their bioavailability. It has been proven that mixing CDW with tailings has a positive effect on the pH value, which has a positive effect on the further development of the entire site. The increase in the pH value is provably dependent on the amount of construction waste added, so it can be said that the increasing amount of construction waste will result in improved parameters of the burnt tailings. The results of the BCR analysis show that aluminum from the tailings will be released both from the reducible and oxidisable fractions, where it will be mainly bound to sulphides. The relatively high concentration of Fe in the oxidisable fraction (2002 mg Fe kg−1) suggests that Fe is bound to sulphides in the tailings, and it is due to the high residual pyrite and sulphide content in the dumped material, as expected. This work has found no limits where CDW no longer positively affects the acidity of unburnt tailings. For practical application, however, it is important that the mixture of CDW and tailings is properly mixed and then used for remediation.

Experimental investigation on the impact properties and microstructure of recycled steel fiber and silica fume reinforced recycled aggregate concrete

With the continuous development of the economy and society, the production of solid waste is increasing. Construction and demolition waste (CDW), used tires and silica fume are the main components of solid waste. Recycling these materials will reduce resource pressure, decrease carbon emissions and protect the environment, while bringing certain economic benefits. This study focused on the influence of the synergistic effect of recycled steel fibers (RSF) and silica fume on the mechanical properties and impact resistance of recycled aggregate concrete (RAC). The mathematical statistical model of Weibull distribution was adopted to depict the impact results. In addition, the microstructure of the interfacial transition zone (ITZ) between the cement paste and the aggregate/fiber was researched by scanning electron microscopy (SEM). Results revealed that the synergistic effect of RSF and silica fume significantly improved the impact resistance of RAC. Especially the specimen containing 10% silica fume and 0.75% RSF performed the best properties, the first crack impact and failure impact energy increased by 421.9% and 461.3%, the net-gain in them by the synergistic action of silica fume and RSF with values of 102.7% and 115.3%. The distribution law of the impact life for RSF reinforced RAC can better describe by the two-parameter Weibull distribution function. Impact resistance life was predicted corresponding to reliability levels. SEM investigations revealed that the ITZ between cement and aggregate/RSF significantly improved by mixing silica fume.

Long-term loss of tension stiffening of concrete containing recycled aggregate and steel fibres

This paper presents experimental results on the long-term loss of tension stiffening of concrete containing recycled aggregate and steel fibres. Washed construction and demolition wastes (CDW) size 20 mm were used as a replacement for the natural coarse aggregate, and hooked-end steel fibres (DRAMIX 3D 65/35BG) were added to the mixes. Square section prisms of concrete (120x120x1200 mm) reinforced with a central steel bar were prepared and cast with different replacement percentages of recycled aggregate and volume fractions of steel fibres. A direct tensile load was applied to the steel bar and the measurements of the strain on the concrete surfaces were then recorded for a period of 35 days to assess the long-term loss of tension stiffening. The results indicated that the substitution of NA by RA increased the loss of tension stiffening over time up to 12.9%. However, the addition of steel fibres proved to be highly beneficial; the inclusion of 0.5% and 1.0% steel fibre content to the NC and RAC reduced the loss up to 9.8% and 20.4%, respectively. According to the obtained results, modifications to the Eurocode2 method for predicting the long-term deflection of reinforced concrete beams were proposed to be implicated in the calculation steps for this type of concrete.

Real-time construction demolition waste detection using state-of-the-art deep learning methods; single–stage vs two-stage detectors

Central to the development of a successful waste sorting robot lies an accurate and fast object detection system. This study assesses the performance of the most representative deep-learning models for the real-time localisation and classification of Construction and Demolition Waste (CDW). For the investigation, both single-stage (SSD, YOLO) and two-stage (Faster-RCNN) detector architectures coupled with various backbone feature extractors (ResNet, MobileNetV2, efficientDet) were considered. A total of 18 models of variable depth were trained and tested on the first openly accessible CDW dataset developed by the authors of this study. This dataset consists of images of 6600 samples of CDW belonging to three object categories: brick, concrete, and tile. For an in-depth examination of the performance of the developed models under working conditions, two testing datasets containing normally and heavily stacked and adhered samples of CDW were developed. A comprehensive comparison between the different models yields that the latest version of the YOLO series (YoloV7) attains the best accuracy (mAP50:95 ≈ 70%) at the highest inference speed (<30 ms), while also exhibiting enough precision to deal with severely stacked and adhered samples of CDW. Additionally, it was observed that despite the rising popularity of single-stage detectors, apart from YoloV7, Faster-RCNN models remain the most robust in terms of exhibiting the least mAP fluctuations over the testing datasets considered.

Comparative life cycle assessment analysis of mono, binary and ternary construction and demolition wastes-based geopolymer binders

The global construction industry is in high demand of sustainable building materials that are cost-effective and simultaneously have a low carbon footprint and energy consumption. As a result, geopolymeric materials primarily derived from construction and demolition wastes (CDWs) have become more attractive sustainable alternatives to ordinary Portland cement (OPC)-based cementitious materials. This paper aims to comparatively analyze the life cycle assessment (LCA) of CDW-based geopolymers comprising recycled brick powder (RBP), recycled ceramic tile powder (RTP) and recycled concrete powder (RCP) at the mono, binary and ternary geopolymer (GP) binder systems. The mono GP binders were synthesized based on pre-targeted design chemical parameters of SiO2/Al2O3 and Na2O/SiO2 molar ratios and liquid-to-solid (L/S) ratio, while the binary and ternary combinations considered different RBP, RTP and RCP precursor contents at the optimized SiO2/Al2O3 and Na2O/SiO2 molar ratios of each constituent CDW precursor in the geopolymer matrices. The LCA analysis was performed through experimental results in terms of embodied energy (E-energy) consumption (Ef), and embodied carbon dioxide (E-CO2) emissions (Cf) as indicators of the global warming potential (GWP) of these GP systems while considering ambient curing. Interesting results were attained in terms of improved sustainable environmental impact of the ternary integration of CDW materials than their mono and binary counterparts when used as precursors in geopolymer binders. The synthesis of the optimal ternary composition of BTC-20:40:40 synthesized at SiO2/Al2O3, Na2O/SiO2 and L/S ratios of 10.2, 0.18 and 0.30, respectively resulted in the lowest embodied CO2 emission of Cf = 5.58 kg/ton/MPa and embodied energy of Ef = 18.61 MJ/ton/MPa, indicating 110.8% and 157.9% reduction in terms of embodied carbon dioxide and embodied energy, respectively, as compared to the reference Portland cement (OPC) binder with equivalent strength at 28 days.

A Hybrid Decision Tool for Site Selection of Construction and Demolition Waste (CDW) Facilities in Developing Countries

A Hybrid Decision Tool for Site Selection of Construction and Demolition Waste (CDW) Facilities in Developing Countries

Mechanical and physical properties of concrete made of alkali-activated lightweight aggregates from construction demolition waste

Dwindling natural resources combined with the increasing amount of construction waste is one of the major challenges of the current time. In concrete production, attempts are being made to tackle both problems by obtaining new materials from construction and demolition wastes (CDW).In previous studies, cold-bounded alkali-activated aggregates were formed of the fine fraction (≤4 mm) of concrete and brick demolition waste and determined regarding mechanical and physical properties. In this paper, these aggregates were used to produce concrete prisms at water-to-binder ratios of 0.5. The concrete prisms were compared to prisms containing natural aggregates regarding compressive and flexural strength, density, water absorption and thermal conductivity following EN standards. Compressive and flexural strength were evaluated after 7 and 28 days. Additionally, flow spread was determined.The results show that the concrete samples made with concrete powder aggregates possess higher compressive strength with 42 MPa than the brick powder aggregate samples with around 30 MPa. Natural aggregates achieve the highest compressive strength with 56 MPa. The water absorption of the concrete prisms ranges between 6 and 15 wt-%. The lower density of the concrete prisms made of brick powder aggregates leads to lower thermal conductivity than the concrete prisms made of concrete powder aggregates.

Critical review of the recovery rates of construction and demolition waste in the European Union – An analysis of influencing factors in selected EU countries

Due to its intense use of resources, the construction sector was identified as a priority sector in the European Green Deal. Construction and demolition waste (CDW) is one of the largest waste streams of the European Union. As it shows a high potential for recycling, the European Commission set a recovery target of 70% under the Waste Framework Directive. To control the performance and achievements of the member states, annual national reports to the EU are required. However, there exist different ways to specify and report these rates. Recovery rates published by EUROSTAT are calculated on the basis of waste treatment data of non-hazardous mineral CDW, generated according to the EU Waste Statistics Regulation. Limiting factors like non-unified methods of data collection, different waste coding systems and misinterpretations of the term ‘backfilling’ impede a cross-country comparison of the published EU recovery rates. In this study, factors that may have a misleading impact on reporting EUROSTAT CDW recovery rates were compiled and a detailed analysis using national quality reports of twelve selected EU countries as a data base were performed. The development of the reported recycling rates over five years was examined and the influence of the various factors was determined. The findings may enhance a more purposeful (scientific) discussion of CDW data and for evidence-based reporting of national recovery rates, and may assist the development towards an improved, uniform EU-wide data set. Finally, this will provide support to decision makers for future policy and governmental requirements.

Workability and mechanical properties of GGBS-RFBP-FA ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates

With urbanization developing, various construction and demolition wastes (CDWs) have emerged, causing environmental and social issues. Green concrete materials, such as recycled aggregates concrete (RAC) and alkali-activated cementitious materials, propose for their environmentally friendly construction. In this study, the ground granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA) ternary composite geopolymer concrete with recycled aggregates (GRAC) containing recycled fireclay brick aggregates (RFBA) proposed at first. Then, this study investigated the fresh and hardened properties of this concrete. The experimental variables included the two types of ternary composite geopolymer concrete with recycled fireclay brick aggregates (GRA-RFBAC) mix ratios, five replacement ratios of recycled coarse aggregate, and four replacement ratios of RFBP. The workability and mechanical properties of GRA-RFBAC were studied, respectively. Moreover, the micro-structures and hydration mechanisms of GRA-RFBAC were also studied. The results showed the feasibility of applying RFBP and recycled aggregates containing recycled fireclay brick aggregates (RA-RFBA) in geopolymer concrete, i.e. GRA-RFBAC exhibited good workability and mechanical properties. The addition of RFBP could improve the workability of GRA-RFBAC. GRA-RFBAC with 10% RFBP replacement ratio of was found to have the best mechanical properties. The addition of RA-RFBA has a detrimental effect on both the workability and mechanical properties of the GRA-RFBAC. The stress-strain relationship model of GRA-RFBAC was give and the stress-strain curves of GRA-RFBAC were similar to those of Ordinary Portland cement concrete with recycled aggregates.

RECYCLED AGGREGATE CONCRETE (RAC): A viable solution for sustainable construction

Construction activities are booming in and around the cities with development and modernization. As a result of these constructions, natural aggregates are being extracted. Simultaneously, there is a significant amount of construction and demolition waste (CDW) generated due to the demolition of structures either due to the structure attaining service life or fashion and the ongoing trend of reconstruction. Therefore, recycling coarse aggregate from CDW in concrete is one of the sustainable solutions to prevent a serious threat to the environment due to the extraction of virgin aggregates and landfilling. This paper presents the results of a study undertaken to examine the influence of recycled concrete aggregate on the properties of new concrete and its life cycle cost (LCC) analysis. It is clear from the test that the strength of RAC is much lowered than natural aggregate concrete (NAC). In order to achieve the optimum strength, the natural aggregate is replaced by recycled aggregate within a range of 0% to 100%, in intervals of 10%. Additionally, to enhance its strength further, reinforcing RAC with new and recycled polypropylene (PP) fiber is done in percentages ranging from 0.25% to 2% by weight of cement with an interval of 0.25%. For analysis, compression, and split tensile strength tests were performed at the end of 28 days of the curing period. The result revealed that 40% replacement of natural aggregate with recycled aggregate achieves the ideal percentage replacement without compromising the strength. Moreover, incorporating 1.5% of new PP fiber or 1.25% of recycled PP fiber in the RAC provides optimum strength. For LCC analysis, the initial investment cost, operations, and maintenance cost, and salvage cost of all the alternatives are compared. Through this analysis, it was determined that the LCC of concrete manufactured using recycled aggregate as concrete ingredients is the lowest. Consequently, incorporating recycled aggregates in concrete production reduces the LCC compared to using natural aggregates.

Eco-hybrid cement-based building insulation materials as a circular economy solution to construction and demolition waste

The primary focus of this study is to develop non-structural ultra-lightweight circular building insulation materials by utilizing a substantial amount of construction and demolition waste (CDW). A unique type of Eco-hybrid cement was formulated as the binder phase, while fine recycled concrete aggregates (FRCA) were used in the aggregate phase. The physical, mechanical, and thermal conductivity properties of the mixtures were assessed by altering the content of Eco-hybrid cement, FRCA, foaming agent, silica-aerogel and water-to-binder ratio. The findings indicated that the fresh properties are primarily influenced by the FRCA and foaming agent ratio, whereas the mechanical properties are predominantly associated with the Eco-hybrid cement and foaming agent content. Microstructural analysis revealed that thermal performance is greatly affected by the pore size distribution and their interconnectivity. Consequently, an ultra-lightweight green foam concrete was successfully developed with a dry density of 0.514 g/cm3 and a thermal conductivity of 0.049 W/mK.

A comprehensive framework towards safe disposal of construction and demolition waste: The case of Egypt

Construction and demolition waste (CDW), produced at various stages of construction projects, is a major problem for the construction industry. This waste has led to an international issue that is widespread and enduring. This research used a quantitative method in two stages to suggest workable options to fix this significant problem. An online survey of Egyptian construction industry professionals was conducted during the first round to gauge how three key factors affected the safe disposal of CDW (SDCDW). Management of route, collection, and transportation (MRCT), determinationof illegal waste dumping sites (DIWDS), and construction waste tracking and scheduling (CWTS)are the three main factors. The development of a comprehensive framework for SDCDW, in support of Egypt's vision 2030, involved multivariate statistical analysis using the structural equation modelling (SEM) method in the second stage. The findings showed that these three factors had a favourable impact on SDCDW in Egypt. This was evidenced through mentioning the acceptable effect sizes of these three factors towards SDCDW; where MRCT showed moderate effect towards SDCDW with a value of 0.16, CWTS showed small effect towards SDCDW with a value of 0.137, and DIWDS showed small effect towards SDCDW with a value of 0.052.The study also discovered that MRCT is more effective in treating SDCDW with a model path coefficient of 0.383. However, DIWDS is the least effective when it comes to SDCDW with a model path coefficient of 0.191. In support of Egypt's Vision 2030, this paper makes concrete suggestions for the government and the construction sector regarding the safe disposal of CDW.

Life Cycle Assessment for Substitutive Building Materials Using the Example of the Vietnamese Road Sector

Road construction usually relies on the utilization of natural aggregates as building materials. However, increasing pressure for sustainable roads highlights the importance of replacing natural materials with industrial byproducts. The scope of the present study was to identify feasible secondary raw materials for road subbase construction, and to investigate their environmental footprint in the context of Vietnam. This work examines road subbase alternatives such as manufactured sand (m-sand), granulated blast furnace slag (GBF), electric arc furnace slag (EAF), construction and demolition waste (CDW), and fly ash (FA). Based on the life-cycle assessment (LCA) approach, the environmental footprints of the alternative waste-based layers were compared with one another and with the corresponding conventional layers. The study comprises following working steps: (i) a comprehensive literature review of the respective materials, (ii) general chemical and soil mechanical analysis of road subbase substitutes, and (iii) LCA of the material alternatives in the context of the Vietnamese road construction sector. The results for the road subbase layer indicated that CDW and FA had lower impacts—particularly in the impact categories global warming potential and mineral resource scarcity. The overall LCA analysis for the road subbase layer highlighted that the greatest footprint contribution was involved in the construction material transportation processes. Thus, sourcing of materials closer to the site or the use of low-emission transport alternatives is needed.