Huanyu Wu

An Investigation of Demolition Waste Management: Case of Shenzhen in China

A huge amount of demolition waste was produced during the Chinese urban renewal process. How to promote the material recycling rate and therefore to reduce the environmental impacts has been a significant challenge. However, there is a lack of research revealing the flows and key procedures of demolition waste management. To fill the research gap, this study conducted in-depth interviews with 15 on-site managers involved in demolition projects in Shenzhen of China. As a result, the flows, key management processes and measures have been obtained. Particularly, the key procedures and waste management measures have been identified with a Process Mapping Approach (PMA). The results show that main stakeholders in demolition waste management chain include general contractors, professional demolition companies, transport companies, recycling plants, landfill officers, government departments and scavengers. Illegal dumping and low marketing acceptation of recycling products are two major barriers of demolition waste management. This study forms a concrete base for future studies aiming at optimizing the demolition waste management process.

Characterization of the Generation Rate of Demolition Waste in Shenzhen, a Mega City of China

The projection of generation of C&D waste is the first process in conducting management. As the basis of the projection, however, there is a lack of data of the demolition waste generation rates (DWGRs) in previous studies and opening sources. This study is aim at providing detailed information of DWGRs by conducting an on-site investigation in 78 demolition projects in Shenzhen city of China, which covers four specific building types and three structure types. The results reveal that the DWGRs range from 877.5 to 2337.5 kg/m2, and the average amount is 1360.2 kg/m2, with the standard deviation of 310.5. By analyzing the mean values, concrete is undoubtedly the dominant part among various waste materials, which is 660.1 kg/m2, followed by brick/block (287.2 kg/m2), ceramic (139.1 kg/m2) and mortar (105.1 kg/m2). Those four inert wastes contribute 88 % to the total weight of demolition waste generated in 1 m2 demolition work. Based on the DWGRs derived from the research, the differences of DWGRs among several building types and structure types are also discussed. Specifically for residential, industrial, commercial and public building, the DWGRs vary from 1304.0 to 1919.5 kg/m2, from 1065.4 to 1448.5 kg/m2, from 1310.2 to 1627.4 kg/m2 and from 1131.7 to 1605.3 kg/m2, respectively. For different structures, the DWGR of brick-concrete structure lies between 1314.9 and 1553.5 kg/m2, frame structure lies between 1079.8 and 1490.3 kg/m2 and frame-shear system lies between 1293.0 and 1696.9 kg/m2. What’s more, a comparative analysis of present DWGRs with findings in previous studies is also conducted. These results could work as the basis for the future studies regarding the generation of C&D waste, and they do add to the body of knowledge that is currently available for understanding the generation of demolition waste in China.

A Framework for Quantifying Carbon Emissions Generated During Demolition Waste Processing

Massive demolition waste has been generated during urban renewal activities in China. Within the waste treatment and disposal procedures, tremendous carbon emissions have been generated due to energy consumption and exhaust emission from machines and vehicles operation. However, there is no attempt has been tried to quantify the carbon emission of demolition waste processing. This paper proposes a framework for quantifying the carbon emission during demolition waste treatment and disposal procedures. The results showed that the framework for quantifying carbon emissions from demolition waste processing involves seven main stages: set the aims of study; build the model and decide the system boundary; identify the carbon emission factors; construct equations to quantifying the carbon emission factors (CEFs); obtain the data inventory for CEFs; calculate the carbon emissions and; output and analysis the results. From the generation to the final disposal, demolition waste processing involves four main stages: generation, onsite treatment, transport and disposal. When using the quantification model, both direct and indirect carbon emission need to be considered. This paper provides a practical framework for scholars to quantify carbon emission from demolition waste processing.

Construction Schedule Risk Analysis Based on Complex System Theory: Methodology and Empirical Study

With the development of China’s society and economy, a large number of construction projects are being actively carried out. Project schedule, as one of the major concerns in construction projects, is always affected by high uncertainties and risks brought by the substantial amount of human and nonhuman factors. Therefore, more prominence should be given to proposing effective measures to minimize the losses caused by schedule risks. Although a certain progress has been made from the previous studies, the lack of dynamics and uncertainty analysis lead to results different from reality. This study aims to propose a novel model for analyzing construction project schedule risk. On the basis of complex systems theory, this paper builds a system dynamics model, and encapsulates the system dynamics model into discrete event simulation to form “work module” which can be combined according to the requirements of different projects, Monte Carlo simulation is also employed to analyze the uncertainty of risks. In addition, a WeChat platform is established for collecting schedule risk data. Finally, the present model is validated by a case study after the structure test and behaviors test. The results showcase that: (1) System dynamics can effectively deal with the complex problems of project schedule from the perspective of system, which includes rework, quality problems, the allocation of resource, productivity, decision-making delays, schedule pressure, etc. (2) It greatly improves the applicability of the model to combine system dynamics and discrete event simulation together. (3) Monte Carlo simulation enables the model to obtain the distribution of real-time planned duration in the process of construction, and to be suitable for managers with different risk attitudes and risk-bearing capacity to make decisions.

Green Building and Construction

The building sector contributes significantly to the energy use and related greenhouse gas (GHG) emissions. Prior research has mainly focused on the impacts associated with material selection and b ...