A critical review of 3D concrete printing as a low CO2 concrete approach

Concrete is by volume the most widely used building material all over the world. The concrete industry emits large quantities of greenhouse gases. Therefore, developing low CO2 concrete becomes an urgent issue for those countries with significant concrete production and consumption. In recent years, 3D concrete printing (3DCP) which is a new concrete construction method, is being developed by many research institutions and enterprises throughout the world. The primary advantages of 3DCP include increasing architecture flexibility, reducing labor usage, as well as saving in-situ construction time and cost. According to the statements by Tay et al. [2017], Wolfs et al. [2018], and Bos et al. [2016], 3DCP as a future construction trend may be a potential low CO2 approach. Thus, the objective of this paper is to critically explore the possible low CO2 strategies for 3DCP which have not been systematically conducted so far. Initially, this study introduces an overview of 3DCP by reviewing the relevant publications over last 20 years. Moreover, the potential low CO2 aspects of 3DCP are illustrated and discussed. Finally, the challenges and opportunities of developing 3DCP are analyzed and summarized. Overall, 3DCP is exploring possibilities of a low CO2 concrete approach, since it might consume less concrete materials and does not need formwork. On the other hand, to maximize CO2 reduction and accelerate the development of this technique, the future routes of 3DCP can be identified such as developing low CO2 printable concrete, seeking the proper reinforcement methods, improving print quality andcapability.Materials and EnvironmentStructural Design & Mechanic