**4. Discussion**

The revision of the state of the art shows incipient development in the literature related to calcium aluminate cements and the environment, such as CO<sup>2</sup> Generation, Sustainability, Additive Manufacturing, Environmental Science, Production Costs, Recycling, and Circular Economy. There is therefore a well-defined research area that can be developed for each topic. Furthermore, this review suggests five emerging research areas for CACs, as shown in Figure 7.

**Figure 7.** Perspectives of research and challenges. **Figure 7.** Perspectives of research and challenges.

areas for CACs, as shown in Figure 7.

#### *4.1. Analysis of Symmetry Spaces from Group Theory—Nanoscience 4.1. Analysis of Symmetry Spaces from Group Theory—Nanoscience*

**Table 4.** Types of documents organized by environmental cluster.

**Article Conference** 

**Paper Review Conference** 

Recycling 37 7 1 4 3 1995**–**2022 Production costs 13 3 1 0 0 1995**–**2021 Environmental Science 3 2 0 0 0 2001**–**2020

manufacturing 3 1 1 1 2 2010**–**<sup>2021</sup> CO2 generation 4 1 0 0 0 2011**–**2021 Sustainability 10 4 1 1 1 2007**–**2021 Circular economy 4 0 0 0 0 2017**–**2021 Life cycle assessment 1 2 0 1 0 2014**–**2021

The revision of the state of the art shows incipient development in the literature related to calcium aluminate cements and the environment, such as CO2 Generation, Sustainability, Additive Manufacturing, Environmental Science, Production Costs, Recycling, and Circular Economy. There is therefore a well-defined research area that can be developed for each topic. Furthermore, this review suggests five emerging research

**Review**

**Book Chapter** **Production Interval (in Years)** 

The fundamental chemical interactions that control the structure and performance of cements have been investigated in detail. However, the complex and crystallographic nature of the phases that form in hardened cements makes it difficult to obtain detailed information on the local structure, reaction mechanisms, and kinetics [35,36,37,38]. Solid state nuclear magnetic resonance spectroscopy could solve the key atomic structural issues within these materials in combination with the proper use of X-ray diffraction. The X-ray diffraction should focus on unveiling the crystalline symmetry spaces, in order to set out promising lines of research. The research could generate models using highly advanced designs of new materials using knowledge of their quantum behavior and their proper combination with various suitable nano materials suggested by the theoretical The fundamental chemical interactions that control the structure and performance of cements have been investigated in detail. However, the complex and crystallographic nature of the phases that form in hardened cements makes it difficult to obtain detailed information on the local structure, reaction mechanisms, and kinetics [35–38]. Solid state nuclear magnetic resonance spectroscopy could solve the key atomic structural issues within these materials in combination with the proper use of X-ray diffraction. The X-ray diffraction should focus on unveiling the crystalline symmetry spaces, in order to set out promising lines of research. The research could generate models using highly advanced designs of new materials using knowledge of their quantum behavior and their proper combination with various suitable nano materials suggested by the theoretical analyzes.

#### analyzes. *4.2. Additive Manufacturing*

Additive

**4. Discussion** 

*4.2. Additive Manufacturing*  Additive manufacturing technologies (also known as 3D printing) have expanded rapidly in various industrial sectors, including aerospace, automotive, medical, architecture, arts and design, food and construction. Transition from visualization and prototyping stages to functional and real parts replacement opens up more design possibilities. Among the various AM applications, building and construction is a very promising large-scale area for development and will be included in the coming manufacturing revolution. However, there are obvious challenges and risks to integrating AM into large-scale construction, such as construction and reinforcement regulation. Additive manufacturing technologies (also known as 3D printing) have expanded rapidly in various industrial sectors, including aerospace, automotive, medical, architecture, arts and design, food and construction. Transition from visualization and prototyping stages to functional and real parts replacement opens up more design possibilities. Among the various AM applications, building and construction is a very promising large-scale area for development and will be included in the coming manufacturing revolution. However, there are obvious challenges and risks to integrating AM into large-scale construction, such as construction and reinforcement regulation. Progress in commercialization is advancing at a slow pace since only a few large-scale 3DP trials for construction can be found in the literature [39–41]. The use of CACs to generate AM-friendly mixtures is therefore a virgin and unexplored research area with great prospects for success.
