Carbon emission analyses of concretes made with recycled materials considering CO₂ uptake through carbonation absorption

Abstract

The effect of incorporation of recycled powder and CO2 absorption of concrete was not considered in the previous life cycle assessment studies. This study evaluated the carbon emission of recycled concrete with different replacement rate of recycled powder and recycled coarse aggregate, taking the carbon absorption in storage and service phase into consideration. The carbon absorption model of recycled concrete with recycled powder was optimized and validated by rapid carbonization tests. It is found that concrete with recycled powder has favorable carbon absorption capacity and can greatly reduce carbon emission. The carbon emission of recycled concrete with recycled powder decreased 12.4–52.2% when compared to normal concrete, and with the increase in the replacement of recycled materials, this advantage becomes more obvious. The evaluation results show that the raw material production and transportation phase are the two main contributors to the carbon emission of recycled concrete, accounting for 67.03–85.81% and 4.01–15.27%, respectively. The evaluation results also show the compensation benefits in storage and service phase from carbon absorption account for 1.58–26.93%. Meanwhile, the long‐distance delivery of natural coarse aggregates makes it possible for recycled concrete to be widely applied.

Low-Carbon and Fundamental Properties of Eco-Efficient Mortar with Recycled Powders

“…As proposed by Yu et al [70], the value of p SCGP is 74.38 kg/t. Xiao et al [5] have pointed out that p Sand is 0.649 kg/t and p Cement is 757.60 kg/t. The value of p Water is considered as zero in this model, as the CO 2 emission from water is negligible [71,72].…”

“…Researchers have confirmed that the grinding process contributes to increasing the surface area of RCP and exposes the non-carbonized part in the building demolition. The increase in the CO 2 absorption of eco-efficient mortar can largely offset the CO 2 emissions from grinding [5,73]. Therefore, stimulating the potential of solid waste to meet the basic requirements of general cementitious materials is an effective method to reduce carbon emissions by the cement industry.…”

“…The CO 2 emission generated by transportation (t i ) is related to the transportation distance of each material and the CO 2 generated by the corresponding transportation mode. The data of transportation distance and CO 2 emission by different transportation modes are derived from Xiao et al [5], listed in Table 4. Referring to the investigation by Xiao et al [5], for each ton of solid waste reused instead of consigned to a landfill, the CO 2 emission will be reduced by 1.055 kg.…”

“…CO 2 emissions by the construction industry contribute greatly to the global CO 2 emissions, as the production process of construction materials (e.g., cement and steel) consumes a lot of energy. For instance, it is estimated that by 2050, the annual global cement production will reach 8 billion tons [4] and the CO 2 emissions from cement production will reach 6 billion tons [5]. Besides, with the development of urbanization, the defects of early urban planning and the functionality of buildings lead to the demolition of a large number of old buildings.…”

Mechanical and durability properties of steel fiber‐reinforced concrete containing coarse recycled concrete aggregate

“…As was reported previously, more than 17, 123, 850 and 15,000 Mt of construction and demolition waste (C&D) is produced per annum in Australia, USA, Europe and China, 6,7 respectively, but only 10% of them are being recycled 7 . Replacing natural aggregates with RCAs not only prevents the over‐exploitation and depletion of non‐renewable natural resources, but also reduces the environmental influence of disposal of C&D waste in landfill 8,9 …”