Recycling Of Construction Waste Research Articles

Analysis of fire resistance of cement mortars with mineral wool from recycling

The objective of this research is to analyse the fire resistance of cement mortars with mineral wool from construction and demolition waste (CDW) recycling. The recycled mortars are therefore exposed to direct fire reaching a maximum temperature of 700 °C, and an experimental plan is designed to analyse thermo-mechanical behaviour before and after the testing of the mortars with different types of recycled fibres. The results show that the surface hardness of all mortars is practically unchanged after the fire, whereas the incorporation of fibre residues produce a significant improvement in the flexural strength after fire test compared with the reference mortar. The compressive strength values of all mortars decrease after the fire although they remain at optimum values for use according to regulatory requirements. The values of thermal conductivity are lower or remain unchanged after the fire test. Results show that the addition of these recycled fibres can be a sustainable alternative to the commercial ones currently being used, improving mechanical-thermal behaviour after the fire and preventing the explosive behaviour of the mortars.

Implementing on-site construction waste recycling in Hong Kong: Barriers and facilitators

Construction and demolition (C&D) waste recycling constitutes an indispensable component in the overall waste management strategy. Unlike the traditional recycling approaches whereby C&D waste is transported to off-site facilities for treatment, construction managers are actively exploring the possibility of on-site recycling where C&D waste is treated directly at source. This study reports the barriers and facilitators of implementing on-site C&D waste recycling by contextualizing it in Hong Kong. It does so by adopting a mixed-method approach combining case study, site visits, and interviews. It is discovered that the barriers include (1) site space constraints, (2) narrow window of opportunity to trade recycled products, (3) vulnerable business case, (4) lack of support from off-site recycling, and (5) lack of government policy support. A series of facilitating measures are also proposed, including (1) developing customized on-site recycling equipment, (2) establishing a demand-supply information-sharing platform, (3) developing more thriving off-site recycling, and (4) providing more government support. This study probes into the real-life on- and off-site waste recycling practices in Hong Kong's prominent C&D management system. It can also provide useful references for others in developing their own C&D waste recycling strategies by rationally deploying on- and off-site recycling.

Mechanical behaviour of structural concrete with ground recycled concrete cement and mixed recycled aggregate

This article analyses the combined effect of valorising ground recycled concrete (GRC) as 10% or 25% cement replacement and 0% or 50% mixed recycled construction and demolition waste aggregate (RA-CDW) in structural concrete. An exhaustive experimental programme was designed to assess the variation in compressive and tensile strength, modulus of elasticity and hardened concrete density. Non-destructive ultrasonic pulse velocity and electrical resistivity tests were also conducted. The concrete mixes prepared with GRC and RA-CDW exhibited lower mechanical performance than those manufactured with natural aggregate and cement only (although the difference was smaller than the respective replacement ratios). These findings were attributed to: a higher water/binder (cement + GRC) ratio, the dilution effect resulting from a lower cement content in the new mixes and the intrinsic properties (water absorption and abrasion resistance) of the new recycled components. The mixes with 10% GRC and 50% RA-CDW, however, showed similar mechanical performance and remained in the same strength class as those with 50% RA-CDW and 100% Portland cement. In terms of the electrical resistivity and ultrasonic pulse velocity tests, the effect of replacing OPC with GRC was below 14%, irrespective of whether natural or recycled aggregates were used. Such promising findings pave the way for more efficient and global C&DW management with a view to steering the construction industry toward the circular economy.

Construction and Demolition Waste (CDW) Recycling—As Both Binder and Aggregates—In Alkali-Activated Materials: A Novel Re-Use Concept

This article demonstrates the possibility of producing alkali-activated materials (AAM) from a mixture of mechanically processed concrete, ceramic, masonry, and mortar wastes, as a sustainable alternative for recycling construction and demolition wastes (CDWs) under real conditions. The addition of 10% Portland cement allowed the materials to cure at room temperature (25 °C). CDW binder achieved a compressive strength of up to 43.9 MPa and it was classified as a general use and low heat of hydration cement according to ASTM C1157. The concrete produced with this cement and the crushed aggregates also from CDW reported a compressive strength of 33.9 MPa at 28 days of curing and it was possible to produce a high-class structural block with 26.1 MPa according to ASTM C90. These results are considered one option in making full use of CDWs as binder and aggregates, using alkaline activation technology thereby meeting the zero-waste objective within the concept of the circular economy.

Influence of 5G and IoT in construction and demolition waste recycling – conceptual smart city design

Influence of 5G and IoT in construction and demolition waste recycling – conceptual smart city design

Sustainable Development of Civil and Residential Real Estate Based on the Construction Waste Recycling

The work is devoted to assessing the environmental and economic efficiency of construction waste recycling concerning the sustainable development of civil real estate. The crisis processes in the micro-and macro-level economy has a negative impact on the Russian investment and construction complex, which threatens the national task performance to provide affordable housing within implementation of the investment programs financed by municipal and federal budgets. It is shown that one of the directions of sustainable reproduction of real estate objects in modern socio-economic conditions is the optimal design and selection of materials using innovative recycling technologies. Low rates of retiring areas replacement and a steady trend of growth in the volume of construction industry waste is observed. This approach is focused on solving two global problems: the economic benefits of using resources and the elimination of environmental pollution. Proposed algorithms evaluate the potential effectiveness of the property manager’s activities and the practical implementation of the techniques in management software.

Civil construction wastes and influence of recycling on their properties: a review

Failures in the management and planning processes for waste disposal have caused serious urban and environmental problems leading to costly and inadequate management in cities. The lack of areas for waste deposition resulting from the occupation and valorisations of urban areas, the high social costs in waste management, troubles of public sanitation and environmental contamination are some of these problems. With technology suitable for the joint use of recycled construction waste as coarse aggregate, it is intended to reduce the extraction of sand and gravel, and also to reduce the volume of waste landfills. In this manuscript, a review of the bibliography on construction waste and its potential for application in the construction industry is presented.

Evolutionary game analysis of construction waste recycling management in China

With China's rapid industrialization and urbanization, building industry generates a large amount of construction waste, which is becoming a burgeoning problem for the local governments to ensure a sustainable and effective management of construction waste. There is a general agreement among researchers that construction waste recycling is an important means for curbing the deterioration of the environment in China. Previous studies have focused on the methods of waste treatment and the recycling behaviour of a single stakeholder, as well as lack of consideration of cooperation among different stakeholders. This study develops a dynamic evolutionary game model on construction waste recycling to analyse the symbiotic evolution between the behaviour of construction enterprises and recycling enterprises, in situations with or without government incentives. This research also investigates how government incentive policy affects the dynamic evolution process of the construction waste recycling. The results from this study show that subsidy to construction enterprises is essential to promote the construction waste recycling in China, but compensating recycling enterprises is not always necessary, because in certain cases as long as the construction enterprises recycle the waste, the recycling enterprises will participate in recycling spontaneously without subsidy. Finally, some suggestions and countermeasures are proposed to help achieving an efficient waste recycling management in China.

Optimization of Grasping Efficiency of a Robot Used for Sorting Construction and Demolition Waste

The recycling of construction and demolition waste (CDW) remains an urgent problem to be solved. In the industry, raw CDW needs to be manually sorted. To achieve high efficiency and avoid the risks of manual sorting, a sorting robot can be designed to grasp and sort CDW on a conveyor belt. But dynamic grasping on the conveyor belt is a challenge. We collected location information with a three-dimensional camera and then evaluated the method of dynamic robotic grasping. This paper discusses the grasping strategy of rough processed CDW on the conveyor belt, and implements the function of grasping and sorting on the recycling line. Furthermore, two new mathematical models for a robotic locating system are established, the accuracy of the model is tested with Matlab, and the selected model is applied to actual working conditions to verify the sorting accuracy. Finally, the robot kinematics parameters are optimized to improve the sorting efficiency through experiments in a real system, and it was concluded that when the conveyor speed was kept at around 0.25 m/s, better sorting results could be achieved. Increasing the speed and shortening the acceleration/deceleration time would reach the maximum efficiency when the load would allow it. Currently, the sorting efficiency reached approximately 2 000 pieces per hour, showing a high accuracy.

Alliance strategy of construction and demolition waste recycling based on the modified shapley value under government regulation

<p style='text-indent:20px;'>Construction and demolition waste (CDW) recycling enterprises have an imperfect operation system, which leads to low recovery rate and low production profits. A feasible method to improve this situation involves seeking a high-efficiency enterprise alliance strategy in the CDW recycling system composed of manufacturers, retailers and recyclers and designing a reasonable and effective coordination mechanism to enhance their enthusiasm for participa-tion. First, we constructed a Stackelberg game model of CDW recycling under government regulation and analyzed the optimal alliance strategy of CDW recycling enterprises under punishment or subsidy by the government as a game leader. In order to ensure the stable cooperation of the alliance, we used the Shapley value method to coordinate the distribution of the optimal alliance profit and improved the fairness and effectiveness of the coordination mechanism through modification of the unequal rights factor. Finally, based on the survey data of Chongqing, we further verified the conclusion through numerical simulation and an-alyzed changes in various parameters at different product costs. The results show that the alliance strategy and coordination mechanism can improve the CDW recovery rate, improve the recycling market status, and increase the production profits of enterprises.</p>

Re-cycling of construction and demolition waste and steel slag: characterization of the durability

The main objective of the study was to evaluate the durability of a crushed concrete aggregate, processed from construction and demolition waste and an inert siderurgical aggregate for construction, processed from electric arc furnace steel slag, with a view to boosting their re-cycling, minimizing the consumption of non-renewable natural resources and preserving the capacity of landfills. Both recycled aggregates were selected based on their high availability worldwide and to be generally associated with suitable engineering properties. However, in many cases, their acceptance by the end-users continues to be very low. One reason for continuing this distrust is the lack of knowledge about the durability of both materials. In natural aggregates, durability has been considered as an important mechanical property in the evaluation of their performance, but it has not been studied in recycled aggregates; so, slake durability tests were carried out. Their durability was compared with the behaviour of two reference natural aggregates, a basalt and a limestone. To complement the durability results obtained, macropetrographic and micropetrographic examinations as well as physical characterizations were performed. The results of the tests showed that, under the test conditions adopted, both recycled aggregates present durability which foresees their use in civil engineering applications.

Incentive Mechanism and Subsidy Design for Construction and Demolition Waste Recycling under Information Asymmetry with Reciprocal Behaviors

To solve information asymmetry, we adopted the principal-agent framework to design the incentive mechanisms between the remanufacturer and the collector in the construction and demolition (C&D) waste-recycling industry. By using the model of reciprocity, we analyzed how the entities’ behavioral motives affect their decisions in terms of the incentive mechanisms. The findings showed that the collector responds to their perception of the remanufacturer’s intentions. If the perception is positive, they will make more effort in the collection work. If not, less effort will be put forth. Most importantly, we found that reciprocity helps to save the remanufacturer cost in the incentive mechanisms and makes the collector choose a higher effort level in the collection work. This finding showed that reciprocity serves to solve information asymmetry. By conducting a numerical simulation, we found that although a high subsidy policy can achieve rapid improvement of recycling-supply-chain performance, it is inefficient in maintaining friendly cooperation between the remanufacturer and the collector.

Establishing a sustainable evaluation indicator system for railway tunnel in China

The large-scale construction of railway tunnels in China in recent years has resulted in serious resources waste and environmental damage due to the lack of conception of sustainability. This paper establishes a sustainable evaluation indicator system of the railway tunnel and analyzes the weight of each indicator. Firstly, the fuzzy Delphi method was used to screen the initial indicators. The selected 30 final indicators constitute the railway tunnel sustainable evaluation indicator system, which includes three major dimensions (Policy Management, Support Structure and Auxiliary Facilities, and Regional Ecological Environment) and nine subdimensions; Subsequently, using the analytic hierarchy process to calculate the relative weight of each indicator. The differences in relative weight were compared between the academic researchers and railway tunnel builders. The study results show that on the major dimensions, both sides agree that the “Regional Ecological Environment” should be given priority. However, on the subdimensions, “Ecological Restoration” has gained the greatest consensus among academic researchers, and the railway tunnel builders believe that “Daily Maintenance” should be the key direction of sustainable construction. Therefore, the indicators related to the recycling and utilization of construction waste were recognized by academic researchers, while the indicators related to the optimization of construction management were more valued by railway tunnel builders. This divergence may be due to academic researchers focusing on ecological restoration results, while railway tunnel builders are more concerned about additional construction and maintenance costs. The sustainable evaluation of the Jianhuazhen Railway Tunnel by using the indicator system has obtained positive and effective results.

Современные методы утилизации и переработки строительного мусора

Современные методы утилизации и переработки строительного мусора

Особенности и факторы, определяющие направления комплексного использования вторичных строительных ресурсов

The article discusses the features and factors that determine the direction of integrated use of secondary building resources (SBR) in modern conditions. The author formulates the basic methodological approach to the integrated management of SBR which consists in the fact that management of recycling should begin not at the stage of formation and collection but at all stages of construction products life cycle. It is concluded that in the design of new facilities it is necessary to consider in advance the issues of environmental safety in disassembly, technology and methods of production of construction and demolition works (CDmW), the effectiveness of further processing and use of SBR. To develop efficient SBR use the author proposes the creation of integrated regional recycling of construction waste. The strategic goal may be the establishment of an industry of secondary construction resources recycling.

Sorting efficiency in mechanical sorting of construction and demolition waste.

The requirements for the recycling of construction and demolition waste are tightening, and companies in the waste business have improved their performance to comply with new legislation. Construction and demolition waste includes various recyclable materials, such as metals, plastics and wood. However, effective material recovery requires functional and reliable technology for sorting in order to separate waste fractions into useful secondary materials or applications. This paper concerns the mechanical sorting efficiency of construction and demolition waste with a commercial mechanical sorting equipment consisting of a roller screening and an air separation unit. Sorting ability is studied with pre-sorted and crushed test material. Sieve analysis of pre-sorted test material is used to define particle size distribution before sorting. The quality criteria of construction and demolition waste vary greatly, depending on a number of factors which pose a challenge to the operation of the sorting system. The studied sorting equipment was found to be reliable for producing nine different fractions from pre-sorted and crushed material mixtures. The requirements for the purity level of the fractions and the profitability of utilization define the number of fractions to be sorted cost-efficiently. Typically, a compromise between cost and purity level has to be found.

Analysis of the compactness and properties of the hardened state of mortars with recycling of construction and demolition waste (CDW)

Several countries in the world have experienced considerable economic growth in the construction sector in recent decades, culminating in the demolition and reconstruction of large structures of reinforced concrete, that produced large amounts of solid waste. Much of this construction and demolition waste (CDW) is deposited in landfills, which generates high costs. The objective of this work is to evaluate the use of CDW as a replacement of natural sand in coating mortars. Four mortar mixtures, 1:1:6 (cement:lime:natural sand), with partial and total substitutions of the natural sand were investigated for CDW addition of 0 (reference), 25, 50 and 100wt.%. Physical characterization of the CDW was carried out by particle size analysis while chemical composition was disclosed by EDX. Technological properties related to mortar fluidity, mechanical strength, mass density and water absorption by capillarity as well as environmental characteristics associated with leaching and solubilization of mortars, were evaluated. In addition, the compactness of the material was verified through Rene Feret's law. The results demonstrate that the substitution of more than 25% CDW for sand requires relatively larger amounts of water in the mortar. With regard to the degree compactness, the use of CDW improves the degree of compaction of the evaluated mortars and increase the compressive strength. However, the water absorption of the mortar increased with the levels of incorporated CDW. Therefore, to attend standard requirements for mortars, it is not possible to use CDW contents above 25%.

Optimization and dust emissions analysis of the air jigging technology applied to the recycling of construction and demolition waste

This work aims to evaluate the use of the air jigging technique, a density-based separation technology commonly applied in mineral processing, to upgrade the quality of mixtures (density and geometric properties) that represents the typical composition of construction and demolition waste (CDW) produced in Brazil. In this sense, tests involving the variation of the main operational parameters of jigging (bed expansion rate, pulsation frequency and jigging time) were carried out aiming to find those which provided the best recycled aggregates quality after processing. Also, fines and dust emissions generation during jigging were measured in order to estimate their potential impacts on human health and environment. The results showed that the air jigging process is adequate to improve the quality of CDW by increasing the concrete concentration in the dense product. The use of high bed expansion rates showed to be of major importance to decrease the content of ceramic aggregates in the dense product, allowing obtaining products richer in concrete. Also, the measured properties of the obtained aggregates (size distribution, shape, etc) met the usual standards required for natural aggregates. Finally, material losses and dust emissions generated were negligible in comparison to the total mass processed, although special attention must be given to safety measures due the presence of inhalable particles (<10 μm).

Рециклинг вторичных строительных ресурсов. Проблемы и перспективы отрасли на примере г. Москвы

&lt;span&gt;В статье анализируется проблема утилизации отходов строительства и сноса в России, особенно актуальная в связи с активизацией проектов реновации жилого фонда и реализацией национальных проектов. Наиболее эффективным методом утилизации является рециклинг, т.е. переработка в качестве вторичных строительных ресурсов (ВСР), но по доле перерабатываемых строительных отходов (около 10% от их общего объема) Россия сильно отстает от развитых стран. На примере г. Москвы рассмотрены предварительные итоги начального этапа реновации ветхого жилого фонда и выявлены основные проблемы, негативно влияющие на эффективность и развитие отрасли по переработке строительных отходов. Главные из них&lt;/span&gt;&lt;span class="myHorizontalScaleForEmDashSpaceBefore"&gt; &lt;/span&gt;&lt;span&gt;–&lt;/span&gt;&lt;span class="myHorizontalScaleForEmDashSpaceAfter"&gt; &lt;/span&gt;&lt;span&gt;это недостаточная мощность существующих предприятий и сложность организации процесса сбора и сортировки отходов непосредственно на строительной площадке. С целью преодоления названных ограничений авторы предлагают блок-схему структуры и этапов комплексного рециклинга вторичных строительных ресурсов. Определены и рассмотрены основные экономически эффективные технологии переработки ВСР, которые перспективны для инвестирования в развитие малого и среднего бизнеса с использованием рыночных механизмов и государственного регулирования.&lt;/span&gt;

Construction and demolition waste recycling: Investigating the role of theory of planned behavior, institutional pressures and environmental consciousness

The purpose of this study is to analyze the attitude of builders towards construction and demolition waste recycling in India. A conceptual framework was proposed using theory of planned behavior (perceived benefits, perceived costs, attitude, subjective norms and perceived behavioral control), institutional pressures (regulatory, normative and mimetic) and environmental consciousness on behavioral intention of builders towards construction and demolition waste recycling. Empirical data with 260 responses from different builders of construction sector in two large Indian cities were analyzed through partial least squares based structural equation modelling. The findings indicate that behavioral intention towards construction and demolition waste recycling is mainly driven by personal motivations (perceived benefits, perceived costs, attitude and perceived behavioral control), regulatory pressures and environmental consciousness. The study is relevant for policy makers, regulatory institutions, industry, and academia who study or manage construction and demolition waste and recycling.