2 the production, transportation, installation and removal of steel affect the hidden carbon emission of steel structure buildings.

The newly constructed cast steel structure in 2021 increased by 10.5% compared with 190 million m2 in 2020.

Rebar Cap

The system boundary of China’s GB / t51366:2019 carbon emission calculation also includes the production and transportation, construction and demolition stages of building materials.

combined with the precast steel structure construction EPC project in recent years, linked with the steel structure manufacturing base of China Construction steel structure in Tianjin, and actively promoted the whole process carbon emission reduction of steel structure precast buildings..

From the perspective of the “cradle to grave” life cycle of building materials, this involves the exploitation of raw materials and the production of building materials products in the building materials stage, the construction and installation in the construction stage, the maintenance, repair, renewal and replacement in the use stage, the demolition, recycling and waste disposal in the termination stage, and the transportation of building materials in various stages.

From the perspective of the carrier of carbon emissions, the implied carbon emissions are mainly carried by the building entity, that is, the building materials and their components.

1 the stage of building life cycle involving hidden carbon emissions according to the Research Report on building energy consumption and carbon emissions in China issued by China Building Energy Conservation Association and Chongqing University in 2021, the total carbon emissions in the whole building process in China reached 4.997 billion tCO2 in 2019, accounting for about 50% of the total carbon emissions in China, of which the carbon emissions in the building materials production stage were 2.77 billion tCO2, accounting for 28.0% of the total carbon emissions in China.

Compared with the traditional building structure system and construction method, the steel structure precast building is considered to have low-carbon advantages.

The direct and indirect carbon emissions are generated by the construction operation, while the implicit carbon emissions involve the building materials industry and the construction sector.

The system boundary is defined according to the European standard en15804:2012, including five parts: building material production, construction, building use, life cycle termination and benefits outside the boundary.

Driven by the government and the market, it has developed rapidly and has great potential in recent years.

The idea of carbon emission reduction is to reduce steel consumption.

The idea of carbon emission reduction is to reduce the production energy consumption of steel structure products, use clean energy, and use recycled and recycled steel raw materials to reduce the carbon emission intensity of steel structure products.

Figure 3 key points of design and material selection for hidden carbon emission reduction of steel structure precast buildings in the process of taking measures to implement the hidden carbon emission reduction task of steel structure precast buildings, it needs the cooperation of multiple industry departments based on steel production, steel structure building design, building construction, and even later building demolition and recycling.

Fig.

According to the method of the United Nations Intergovernmental Panel on climate change (IPCC), the sources of carbon emissions are classified into four major sectors: industry, electricity, construction and transportation.

The carbon emissions generated by the construction industry can be classified into direct, indirect and implied carbon emissions.

The second is to “prolong the life and improve the quality”, reasonably carry out the renovation and repair of existing buildings, extend the service life of steel structures, and avoid large-scale demolition and construction; Adopt steel products with high performance and good durability to improve the recycling rate of steel and steel structure components.

However, at the micro level, the carbon emission calculation of the whole life cycle of a specific building often includes the production of building materials.

The construction sector is the consumer end of steel structure assembled products.

Among the carbon emissions from building materials production, the carbon emissions from steel production reached 1.334 billion tCO2, ranking the first.

Therefore, the carbon emission reduction of steel structure precast buildings involves the building materials industry and the construction department.

Among them, the building materials industry is the production end of steel structure products.

The north region design center of China Construction Science and Engineering Group Co., Ltd.

Among them, the direct carbon emission comes from the combustion process of fossil energy such as fuel oil and gas inside the building, such as the use of gas and loose coal for heating, cooking and production of domestic hot water; Indirect carbon emission refers to the carbon emission contained in the electricity and heat input from the outside, which is consumed by the building; Implied carbon is the carbon emission generated during the production, transportation, construction and demolition of building materials.

According to the international conventional practice, in the carbon emission statistics at the macro level, the direct and indirect carbon emissions are classified into the construction sector, while the carbon emissions from building materials production are classified into the industrial sector.

Fig.

From the perspective of practical engineering application, the formulation of implicit carbon emission reduction strategy for steel structure precast buildings involves two aspects: Architectural Design and building materials selection.

In 2014, the European Union stipulated the carbon emission calculation method of buildings according to the environmental product declaration (EPD) of iso14025.

It can also guide the upstream steel industry to implement carbon emission reduction tasks by selecting low-carbon steel products and setting market access thresholds.

According to the statistics of the Ministry of housing and urban rural development, in 2021, the newly constructed precast building area in China was 740 million m2, accounting for 24.5% of the total newly constructed building area, of which 210 million m2 was cast steel structure, accounting for 28.8%.

The key ideas are as follows: first, “reduction”, through space intensive optimization to reasonably control the building area, floor height and scale; Adopt light-weight and high-strength steel and carry out lightweight design of steel structure to reduce the steel consumption per unit building area; Promote new building standardization and modular construction mode to improve the utilization efficiency of steel.

The third is to “green”, select low-carbon steel products, optimize the combination of steel structural components, and replace the building materials and building components with high carbon emissions locally or even as a whole; Use local steel structure products nearby to reduce carbon emissions from transportation.