Research on the Investment Mode and Path of China’s Construction Waste Resourceization Industry

At present,China’s construction waste accounts for about 40%of the total municipal solid waste,with a large stock,a large increment,and a low rate of resource utilization,which is still a big gap compared with developed countries.However,the market prospect of the construction waste industry is relatively broad,the reuse value of the construction waste is high,so these resources should be fully utilized.This paper presents an in-depth analysis of projects in the construction waste resourceization industry,examining the industrial chain,development history,current status,investment and financing modes,and case studies.It proposes targeted strategies for companies to focus on the upstream and downstream segments of the construction industry’s value chain and explores the implementation of investment opportunities in construction waste resourceization.

Adsorption characteristics of Pb from urban stormwater runoff by construction wastes

Construction wastes were selected as the adsorbents and static and dynamic adsorption batch experiments were carried out to investigate the adsorption of Pb to construction wastes with different particle size gradations in the simulated stormwater runoff system.The experimental results show that the pseudo-second-order kinetics model can better characterize the adsorption process of Pb than the pseudo-first-order kinetics model.The adsorption equilibrium data can be well fitted by the Freundlich isotherm model. The construction wastes with different tested size gradations can greatly remove Pb from stormwater runoff and their average removal rate can reach up to 99%.The construction wastes with narrow size distribution can better remove Pb but with worse permeability than those with wide size distribution. The particle size gradation of construction wastes greatly influences the equilibrium time rate and the capacity of Pb adsorption.The equilibrium adsorption rate and capacity are 18.1 μg/min and 5.5 μg/g respectively for the construction wastes with the size of 2.36 to 4.75 mm which are the greatest among the different size gradations.The present study provides a scientific basis for effectively controlling Pb pollution from stormwater runoff and the construction wastes resource utilization.

Controlled low-strength material incorporating recycled fine aggregate from urban red brick based construction waste

Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.

Adsorption characteristics of construction waste for heavy metals from urban stormwater runoff

Stormwater runoff has become an important source of surface water pollution. Bioretention, a low impact development measure in urban stormwater management, has been proven to be effective in the removal of pollutants from stormwater runoff, with appropriate bioretention media. In this study, construction wastes were selected as bioretention media to remove heavy metals from stormwater runoff. Static and dynamic adsorption batch experiments were carried out to investigate the adsorption of heavy metals in simulated stormwater runoff system with construction wastes in different particle sizes. The experimental results show that the pseudo-secondorder kinetic model characterizes the adsorption process and the adsorption equilibrium data are well described by Freundlich isotherm model. The construction wastes used can remove heavy metals from stormwater runoff effectively, with their average removal rates all more than 90%. The particle size of construction wastes greatly influences the equilibrium time, rate and adsorption capacity for heavy metals.

On construction waste disposal in Chongqing

With rapid development of the construction industry in China, lots of construction materials are being widely reused. Meanwhile, more and more materials for building remover or demolition enter into the environment as a result. However, China is facing big building garbage pollution, with simple disposal methods and low efficiency, which urgently needs to be improved. The paper takes Chongqing as an example to illustrate existing problems in this field and then puts forward corresponding countermeasures from the aspects of economy, technology, management and policy, aiming at enhancing the level of construction waste disposal in China.

Construction Waste Quantification and Benchmarking： A Study in Klang Valley, Malaysia

Construction industry is a major contributor of negative impact to the environment. Estimation of construction waste amount is crucial for implementing waste minimization program. Estimation of construction waste amount generated is a mean in assessing the potential for waste reduction. Decision-making should be based on quantified measurements expressed in numerical terms to effectively minimize waste produced. A better understanding of C＆D waste generation in terms of causes and sources can be achieved. Lack of benchmarking will hinder the implementation of more sustainable practices in the industry. The aim of this paper is to establish benchmarks on construction waste generation rate in Klang Valley （greater Kuala Lumpur）, Malaysia using appropriate waste quantification method. Nine projects in Klang Valley constructed between 2006-2010 have been selected for this study, which include residential and commercial building projects conducted by a wide range of contractors employing conventional and IBS systems. Wastage level and waste index approaches had been employed in this study as tools for quantifying waste and also for environmental assessment. Types of waste that generated at significant amount, such as concrete, timber, reinforcement bars, tiles, screeds, and plaster are considered. Other factors, such as waste management provision, Environmental Management System （EMS） employed, record-keeping, contractors＇ profile and other related policies are also assessed by conducting interviews with construction personnel. Based on the findings, overall site-management, size of project, and awareness of waste management among construction personnel are the most significant factors that contribute to construction waste generation. Currently, there is still relatively lack of waste minimization awareness among construction players in Malaysia as reflected by poor waste record-keeping, lack of waste sorting and recycling practice, low usage of IBS systems, and lack of supports from top management, clients, and authorities. The roles of construction authorities are essential in achieving the desired benchmark in waste generation rate for Malaysian context. Construction authorities as the policy maker and enforcer could develop and issue new regulations or incentives to stimulate and encourage waste management practices and the use of green building technology, establishing formally standardized systems in record-keeping of quantitative data, introduce useful guidelines and measures, conduct education and training to achieve sustainability and better environmental awareness among Malaysian construction players.

Use of CCW （Civil Construction Waste） in Soil Improvement

The vast production of CCW （Civil Construction Waste） has caused socio-environmental concern as a result of the exploration of natural resources, clandestine disposal and proliferation of vector-borne diseases, for example. It now gives priority to non-generation, reduction and recycling of CCW. This study, therefore, seeks an alternative for CCW by comparing the physical and mechanical characteristics, both in laboratory and onsite, of the recycled CCW aggregate and natural aggregate （stone powder）, commonly used in the composition of compaction piles for improving soils in foundation works in the city of Recife, Pernambuco, Brazil. All results showed similar behaviours among the investigated samples （CCW recycled and natural）, confirming the satisfactory performance of the investigated CCW material.

Research Characterized the Physical Properties of Recycled Aggregate of Civil Construction Wastes

One of the big problems of the urban centres of the cities in Brazil is the growth of the generation of the Civil Construction Waste （CCW）. A disturbing concern for the public and private sectors is to find proper disposal of Urban Solid Waste （USW） in large cities, since suitable dumping sites for this waste are increasingly scarce due to the spread and development of large urban centres. In general, recycling is currently one of the procedures most studied by researchers for disposal of such waste. In this context and aiming a new application for recycled CCW aggregates, the research characterized the physical properties of the material to use in fill compaction piles in soil improvement. The analysis shows results from laboratorial tests executed in CCW recycled samples, which came from works in different construction stages from Recife-PE, and natural aggregate, adopted as a reference. Characterization tests were performed with samples CCW recycled CLue aggregates and samples of natural fine aggregate （stone powder）. The results of characterization tests showed similarities between the CCW samples tested and the reference samples, indicating that the civil construction wastes has potcntial use as material for consolidation piles in foundation works.

Application of Construction Waste Recycled Material Processing in Road Engineering

In order to promote the recycling of construction waste in China and reduce the cost of road engineering materials,this paper expounds on the technical indexes,road performance,durability,and the impact on the compressive strength of road engineering of construction waste recycled materials based on the analysis of the processing technology of construction waste recycled materials to provide reference for future research.

DRIVING FACTORS FOR CONSTRUCTION WASTE MINIMIZATION:EMPIRICAL STUDIES IN HONG KONG AND SHENZHEN

Effective waste management is an important aspect of green building development.However,a number of studies find that construction waste minimization actions are not satisfactorily performed in practice.Thus,it is of significance to identify the driving factors that influence construction practitioners’waste minimization behavior.This paper aims to explore the driving factors by comparing the affecting factors and construction waste minimization behavior between Hong Kong and Shenzhen.Firstly,through a comprehensive literature review,potential affecting factors were categorized into five groups:background information variables,construction waste minimization intentions,economic viability,governmental supervision,and project constraints.Based on the identified factors,a questionnaire was initially designed and then refined through a focus group meeting with three experienced experts.A total of 166 questionnaires were collected and non-parametric tests(Mann-Whitney U Test and Kruskal-Wallis Test)were conducted to investigate the underlying driving factors.Results revealed that background information variables play insignificant roles in construction waste minimization.Compared with other affecting factors(i.e.,waste minimization intentions,governmental supervision,project constraints),economic viability is the most important driving factor that determines construction waste minimization.Results suggested that local governments should make policies that increase practitioners’profit,rather than just increasing their intentions or regulating waste management behavior.

A COST-BENEFIT ANALYSIS OF GREEN BUILDINGS WITH RESPECT TO CONSTRUCTION WASTE MINIMIZATION USING BIG DATA IN HONG KONG

It is generally accepted that the extra construction costs involved in the construction of green buildings will result in benefits including lower operation costs,higher sale/rental prices,and better sustainability performance.However,there has been little recognition of construction waste minimization(CWM)as one of the important benefits of sustainability performance as designated in green building. is paper aims to provide a better understanding of the cost benefit of green buildings with respect to CWM by using big data in the context of Hong Kong.The study is innovative in that it conducts a cost-benefit analysis specifically on CWM of green buildings by mining large-volume datasets.A surprise finding is that Hong Kong’s green building rating system(GBRS),i.e.the BEAM Plus,has a negligible effect on CWM,while it generally increases construction costs by approximately 24%.Hence,the increased construction cost of green buildings cannot be offset by CWM if corresponding items in the BEAM Plus are not properly incentivized. is paper demonstrates the necessity of emphasizing CWM-related items in GBRSs and of taking appropriate measures to deal with them.It also provides better decision-support information on the increased construction costs and the attainable benefits of green building that developers may wish to consider when initiating a green building project.

Permanent deformation and prediction model of construction and demolition waste under repeated loading

This study aims to reveal the macroscopic permanent deformation(PD)behavior and the internal structural evolution of construction and demolition waste(CDW)under loading.Firstly,the initial matric suction of CDW was measured by the filter paper method.Secondly,the PD of CDW with different humidity and stress states was investigated by repeated load triaxial tests,and a comprehensive prediction model was established.Finally,the discrete element method was performed to analyze the internal structural evolution of CDW during deformation.These results showed that the VAN-GENUCHTEN model could describe the soil-water characteristic curve of CDW well.The PD increases with the increase of the deviator stress and the number of cyclic loading,but the opposite trend was observed when the initial matric suction and confining pressure increased.The proposed model in this study provides a satisfactory prediction of PD.The discrete element method could accurately simulate the macroscopic PD of CDW,and the shear force,interlock force and sliding content increase with the increase of deviator stress during the deformation.The research could provide useful reference for the deformation stability analysis of CDW under cyclic loading.

An Experimental Study of Self-Compacting Concrete Made with Filler from Construction and Demolition Waste

This study evaluated the influence of the Portland cement replacement by 0, 5%, 10%, 15% and 20% of Construction and Demolition Waste (CDW) filler contents in the production of self-compacting concrete (SCC). The SCC mixtures were evaluated on fresh state by slump flow, J-ring, resistance of segregation, specific gravity, and on hardened state by compressive and splitting tensile strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.

Construction and Demolition Waste Management Scenario in Republic of Cape Verde—The Case Study of City of Praia

Globally, the construction industry is one of the leading producers of solid waste. The city of Praia, the capital of the Republic of Cape Verde has been suffering from environmental degradation with the irregular disposal of waste caused by inadequate management of waste from construction and also the demolition. The research was developed based on local inspections in the context of environmental laws, in semi-structured interviews with people who deal with this activity and bibliographic references. The main conclusion is that the city does not have a CDW management plan consequently leading to environmental problems. On the other hand, waste of recycled construction can be used as inert reducing the consumption of raw materials that can be used as base and sub-base for paving, landfills, aggregate in mortars and raw materials to be manufactured blocks, bricks concrete tiles, etc.

Modelling the water diversion of a sustainable cover system under humid climates

Extreme rainfall significantly threatens the safety of the landfill cover system,especially under humid climates.This study aims to provide design recommendations for a sustainable landfill cover system consisting of a low-permeability soil layer underlying a two-layer capillary barrier for humid climates.First,the numerical back-analysis was conducted for verification against a series of flume model tests.Then,a parametric study was performed to investigate the effects of inclination angle,particle size and layer thickness on the lateral diversion length(DL)of the three-layer cover system under the 100-year return period rainfall of humid climates.The results show that the water lateral DL of the cover system can be greatly enhanced by increasing the inclination angle from 3°to 18°.Moreover,the bottom layer of the cover system with a coarser d10 was more susceptible to the impact of the heavy rainfall,while this can be alleviated by increasing the thickness of the bottom layer.A dimensionless number,defined as the ratio of thickness and d_(10) of the bottom layer,is proposed for designing lateral diversion of the three-layer cover system under humid climates.To preserve the maximum DL,it is suggested that the proposed dimensionless number should be larger than 95 and 110 for the design of rainfall events with 50-year and 100-year return periods for humid climates,respectively.

Review of construction and demolition waste management tools and frameworks with the classification,causes,and impacts of the waste

This review looks over the current construction and demolition waste management(C&DWM)situations by scrutinizing the definition,classification,components,compositions,generated sources and causes,impacts of generated construction and demolition wastes(C&DWs),waste management hierarchy(WMH),3R principles(Reduce,Reuse,and Recycle),Circular Economy(CE),frameworks,tools,and approaches of C&DWM.After reviewing the literature this study contributes to the literature by the following means:(a)suitable working definitions of C&DW and C&DWM are provided,(b)an expanded WMH for construction and demolition operations is presented,(c)frameworks of C&DWM are identified and listed as follows:frameworks based on WMH,including 3R principles and CE concept,frameworks focusing on the quantification,estimation,and prediction of generated C&DW,frameworks focusing on effective and sustainable C&DWM,frameworks focusing economic,social,and environmental performance assessment,frameworks based on multi-criteria analysis(MCA),frameworks based on post-disaster recovery period,and other miscellaneous frameworks,and(d)four categories of tools utilized in C&DWM are identified and explained,namely,approaches employed in C&DWM,information technology(IT)tools employed in C&DWM,multi-criteria decision analysis(MCDA)tools employed in C&DWM,and C&DWM technologies.Moreover,this study also found that CE,and green rating system(GRS)are widely used approaches,Building Information Modeling(BIM),Radio Frequency Identification(RFID),Geographic Information System,and Big Data are the extensively used IT tools,Analytical Hierarchy Process,FUZZY,TOPSIS(Technique for Order Preference by Similarity to the Ideal Solution),Weighted Summation,Elimination and Choice Expressing the Reality II,Elimination and Choice Expressing the Reality III,Evaluation of Mixed Data,and REGIME(REG)are the widely used MCA tools in C&DWM,and Prefabricated Construction and Modular Construction are broadly used C&DWM technologies.Furthermore,it has been observed that the application of the Analytic Networking Process(ANP)and hybridization of ANP,FUZZY,and TOPSIS tools do not catch considerable attention in the literature for conducting MCA,although it yields more precise outcomes.Additionally,most previous research has focused on the estimation of generated C&DW,but less attention has been given to forecasting the generated C&DW due to inadequate available C&DW data.This review article also assists C&DWM practitioners,academics,stakeholders,and contractors in choosing appropriate frameworks and tools for C&DWM while managing C&DW.

Characterization of Mechanical Properties of Waste Slurry Modified by Recycled Sand and Cement

In order to study the modification effect of recycled sand on cement reinforced waste slurry(CWS),triaxial test,scanning electron microscope test and X-ray diffraction test were carried out.The mechanical test of recycled sand and cement reinforced waste slurry(RCWS)shows that the deviatoric stress–strain curve of RCWS samples changes from hardening type to softening type with the increase of recycled sand content;the peak stress increases with the increase of recycled sand content;recycled sand can enhance the shear strength of CWS by increasing both cohesion and internal friction angle.The microscopic test shows that recycled sand can improve the structural compactness by cementing with hydrated calcium silicate and can reduce the void ratio and orientation index of RCWS samples.Finally,the mathematical model between shear strength parameters and void ratio is established.The research shows that adding an appropriate amount of recycled sand and cement has a good modification effect on waste slurry.This is an effective method to treat two kinds of construction wastes:construction waste slurry and waste concrete.

Guide for Barriers when Using Soils and Construction Materials with Environmentally Sensitive Contents

On 16 July 2021,the German“Mantelverordnung”(Construction Materials Regulation)was published in the Federal Law Journal.From August 1,2023,this regulation is to be applied nationwide and,for the first time,regulates legally nationwide binding requirements for mineral construction waste and its use in technical structures.It also refers to specific construction methods with construction waste material.In the course of the construction of infrastructure traffic routes,it is possible to use these construction materials with limited contamination for the construction of,e.g.,noise barriers,dams or embankments.The German M TS E(Merkblattüber Bauweisen für Technische Sicherungsmaßnahmen beim Einsatz von Böden und Baustoffen mit umweltrelevanten Inhaltsstoffen im Erdbau)Guideline of the FGSV(Road and Transportation Research Association)lists various alternatives for barriers in such structures.Geosynthetic barriers,e.g.,GCLs(Geosynthetic Clay Liners,also known as bentonite mats)or polymeric geomembranes as well as other geosynthetics can have economic and design advantages over conventional mineral barriers.Depending on the proposed construction method,the guideline sets out certain requirements,not only but also for permittivity and confining stress.In the following,the construction methods in general and the design solutions with GCLs in particular are presented.

Tensile Behavior of Strain Hardening Cementitious Composites (SHCC) Containing Reactive Recycled Powder from Various C&D Waste

This work investigates the feasibility of utilizing reactive recycled powder(RP)from construction and demolition(C&D)waste as supplementary cementitious material(SCM)to achieve a ductile strain hardening cementitious composites(SHCC).The recycled mortar powder(RMP)from mortar waste,recycled concrete powder(RCP)from concrete waste and recycled brick powder(RBP)from clay brick waste were first prepared,and the micro-properties and tensile behavior of SHCC containing various types and replacement ratios of RPs were determined.The incorporated RP promotes pozzolanic and filler effects,while the hydration products in cementitious materials decrease with RP incorporation;therefore,the incorporated RP decreases the compressive strength of SHCC.Attributed to the reduction in the matrix strength,the incorporated RP increases the crack-bridging extent and ductility of SHCC;the irregular micro-structure and high reactivity of RP also help the strain-hardening performance of the prepared SHCC.In addition,the strainhardening performance of SHCC containing RMP and RBP is surperior to that of SHCC with RCP and is slightly lower than that of SHCC with fly ash(FA);for instance,the ultimate strain of SHCC containing 54%FA,RMP,RCP and RBP is 3.67%,3.61%,2.52%and 3.53%,respectively.In addition,the strain-hardening behavior of an SHCC doubled mix with FA and RMP or RBP has a similar ultimate strain and a higher ultimate stress than SHCC containing only FA.

Water Retention Curve and Particle Breakage of Aggregates Recycled from Demolition Waste

CDW （construction and demolition wastes） present a high amount of aggregate chips covered with mortar. This results in high absorption of water with a direct impact in particle breakage or disaggregation. It is supposed that intra particle suction plays an important role in this phenomenon. However, WRCs （water retention curves） of CDW are not well understood. In this work, the WRCs of dynamically compacted specimens of aggregates recycled from the demolition of the National Stadium in Brasilia are studied. The objective of this study is to obtain WRCs of the recycled materials by using the pressure plate and filter paper methods. The breaking effect during compaction is quantified from the grain size distribution curves. The particle breakage during compaction increases when the energy is augmented. The results from the WRCs were incorporated into a pore size capillary model to predict pore size distribution.