Cradle-to-Site Carbon Emissions Assessment of Prefabricated Rebar Cages for High-Rise Buildings in China

Boya Jiang,Yiqi Tao,Yu Wang,Hongxian Li,Ling Dong

doi:10.3390/su11010042

Abstract

Construction industrialization is growing rapidly and has received significant attention worldwide in recent years. The industrialization of construction results in several benefits, including the promotion of sustainable construction and the development and application of prefabrication techniques. The Prefabricated Rebar Cage (PRC) is an emerging solution applied to high-rise buildings as a replacement of the In-situ Reinforcing Bar (ISRB) construction method. This paper investigates the cradle-to-site carbon emissions of PRC, and compares the results with those of conventional in-situ rebar construction methods for high-rise buildings. The cradle-to-site cycle is divided into three stages, namely, material preparation, transportation, and on-site construction. For the material preparation stage, it is found that CO2 emissions are increased by 3% when using PRC due to the operation of machinery during the prefabrication process. In the transportation stage, CO2 emissions are found to increase by 3.3 times for PRC, as there is more transportation required for PRCs than for conventional construction methods. During the on-site construction stage, the PRC method demonstrates its advantages by reducing CO2 emissions by 44.7%, which is attributed to decreased hoisting frequency and lower mechanical utilization for fewer joining activities. Overall, CO2 emissions can be reduced by 1.24% by adopting the PRC method for high-rise buildings, and it is therefore recommended to adopt PRCs for this purpose. This research studies carbon emissions of PRC and contributes to promoting the sustainable development of prefabricated building techniques.

Highlights

A bulletin, issued by the Ministry of Environmental Protection of the People’s Republic of China (MEP) on December 18, 2016, highlighted the severe environmental problems caused by the heavy pollution in large urban cities located in the central and eastern parts of China, and stated that the average pollutant concentration levels were becoming worse in 71 cities
For the In-situ Reinforcing Bar (ISRB) method, it is demonstrated that steel scaffold tubes emit 28,325 kg CO2 and scaffold couplers emit 6281 kg CO2, while the figure for the Prefabricated Rebar Cage (PRC) structure is only 11,525 kg CO2 and 2555 kg CO2, respectively, which is approximately 59.3% lower than that for the ISRB method
PRC is an environmentally-friendly construction method when compared to conventional ISRB

Summary

Introduction

A bulletin, issued by the Ministry of Environmental Protection of the People’s Republic of China (MEP) on December 18, 2016, highlighted the severe environmental problems caused by the heavy pollution in large urban cities located in the central and eastern parts of China, and stated that the average pollutant concentration levels were becoming worse in 71 cities. In the International Energy Agency (IEA) research report, China has been named as the world’s largest carbon emitter, accounting for approximately 21% of the total global carbon emissions [3]. As a major contributor to carbon emissions, the Chinese construction industry consumes approximately 40% of total energy resources worldwide, and accounts for nearly 36% of global CO2 emissions [5] and 40% of the global turnover of raw materials [6]. As the key ingredient of concrete, accounts for 5–7% of global anthropogenic carbon emissions [8]. One of the key ways to reduce carbon emissions of the construction industry is optimizing the construction method of concrete building

Methods

Results

Conclusion