**6. Discussion and conclusion**

As can be seen from the literature, the PCMs were incorporated by building materials in two ways: (i) addition of MPCM to building materials (ii) the addition of non-encapsulated PCM to building materials by impregnation (directly or by vacuum) method. Despite numerous studies carried out to make fresh materials suitable for 3D printing, no study has developed geopolymer-based PCM for 3D printing construction.

• Although the vermiculite and perlite clay minerals have been used to prepare FSCPCMs with leakproof property until now [77, 78], vermiculite and perlite based FSCPCMs has not been yet integrated with fly ash based-GP to prepare novel kinds of GP-FSCPCM concretes which can be used to decrease temperature fluctuations of building inside.

• Literature survey indicated that paraffin as PCMs were commonly used with geopolymers. However, bio-based fatty acid eutectic mixtures are rarely used. When compared to the paraffins, the fatty acid has better TES characteristics in terms of especially subcooling degree, volume change, latent heat energy storage capacity, phase change reversibility and low-cost due to their produce ability from the vegetable and animal fats [79, 80].

Therefore, based on these considerations, we think that the most proper way to achieve GP-FSCPCM concrete with the most effective is incorporation of nonencapsulated PCM with proper material by vacuum infiltration method and then addition to the GP mortar.

To prepare form-stable composite phase change materials (FSCPCMs), PCMs may be impregnated separately with vermiculite and perlite using vacuum impregnation technique (**Figure 1**) [78, 81].

To achieve the form-stable composition, the mass fraction of PCM could be changed. Then, each of the vermiculite/PCM and perlite/PCM composite samples could be subjected to leakage test by heating them above melting temperature of regarded PCM. After this test, the composite with free of leakage will be defined as FSCPCM.

Different clays such as diatomite, perlite, kaolinite, bentonite, vermiculite etc. as porous, lightweight supporting materials have been used to produce form-stable composite PCMs (FSCPCMs) [82, 83]. Among these clay minerals, vermiculite (VMT) and perlite (PER) are good supporting materials for absorbing organic PCMs. VMT is a lightweight material with porous, inexpensive, ecologically harmless, non-toxic and expandable as much as 8–30 times its original size, when heated to about 800°C. Therefore, VMT is used for construction and insulation in buildings. Perlite (PER) is glassy volcanic rhyolitic rock. PER can be expanded up to 10–20 times its original volume when heated rapidly at 850–1150°C. The resulting expanded perlite (EPER) particles are spherical in shape, usually fluffy, highly porous due to a foam-like cellular internal structure. EPER has low sound transmission, high fire resistance, a large surface area, low moisture retention and a very low density. Besides it is classified as environmentally safe ultra-lightweight

**Figure 1.**

*Vacuum impregnation technique used for preparation of FSCPCMs.*

*Incorporation of Phase Change Materials and Application of 3D Printing Technology... DOI: http://dx.doi.org/10.5772/intechopen.96886*

building material. In the buildings, VMT and PER are used as lightweight aggregate for plaster, concrete compounds, firestop mortar, and component of interior fill for walls. Moreover, they have good chemical compatibility with organic PCMs such as fatty acids and their binary mixtures. Therefore, both clay minerals are promising candidates as building material to prepare FSCPCMs for TES applications in buildings [78, 81].

By using, 3D printing technology, GP, PCMs and charging storage facilities with energy generated from renewable sources, we can reduce the greenhouse gas emissions and the dependence on fossil fuels, preserve the environment, attenuate the overheating or excessive cooling of the room and maintain a desirable temperate without the use of the air-conditioning system, allow to positively influencing indoor room temperature by storing direct solar radiation.
