**2.2 Natural fiber-reinforced geopolymers for construction and passive cooling systems**

In a recent research, vascular natural fiber is used to improve the properties of end products to be used for more than one purpose. The use of natural fibers such as *Luffa cylindrica* fibers (LCF) as reinforcements for geopolymers has several objectives. In addition to improving mechanical properties, these vascular fibers improve the microstructural properties of the resulting material. In this research,

**Figure 3.** *The schematic diagram of the research methodology [11].*

**Figure 4.** *XRD patterns corresponding to kaolin and the resultant geopolymer [11].*

geopolymers (Sk-geopolymer) and LCF-reinforced geopolymers (LG composite) were made for reference and polymer composites using fiber as a reinforcing material with volume percentage of 10% as shown in **Figure 3**. The composition of the Sk-geopolymer was reported in our previous work [11].

As can be seen from X-ray tests, **Figure 4**, kaolinitic soil is transformed to an amorphous geopolymer gel as a result of the calcination at 750°C and the subsequent geopolymerization reactions [11, 16, 17]. These XRD results are in agreement with the SEM images as reported in **Figure 5**. The kaolin layers in **Figure 5A** break down by the geopolymerization process to obtain geopolymers with a semi-uniform nano-pore network as shown in **Figure 5B**. We also note the presence of bundles of tubes forming LC fiber. Both phases, whether the porous geopolymeric matrix or vascular LCF, help to increase the surface moisture of the material, which helps in the applications of passive cooling systems, especially in hot and dry regions.

On the other hand, we note that introducing LCF contributed significantly in improving the mechanical properties of geopolymeric products, where the

**5**

**Figure 6.**

**Figure 5.**

*Introductory Chapter: Case Studies of Functional Geopolymers*

*SEM images of the precursor (A), geopolymer matrix (B), and the LCF cross section (C) [8, 11].*

*Mechanical and physical properties of geopolymers (Sk-geopolymer) and geopolymer composite (LG-composite): Compressive strength (A), Bulk density (B), and Stress-strain curve (C) [11].*

*DOI: http://dx.doi.org/10.5772/intechopen.90363*

*Geopolymers and Other Geosynthetics*

**4**

**Figure 3.**

**Figure 4.**

*The schematic diagram of the research methodology [11].*

*XRD patterns corresponding to kaolin and the resultant geopolymer [11].*

Sk-geopolymer was reported in our previous work [11].

geopolymers (Sk-geopolymer) and LCF-reinforced geopolymers (LG composite) were made for reference and polymer composites using fiber as a reinforcing material with volume percentage of 10% as shown in **Figure 3**. The composition of the

As can be seen from X-ray tests, **Figure 4**, kaolinitic soil is transformed to an amorphous geopolymer gel as a result of the calcination at 750°C and the subsequent geopolymerization reactions [11, 16, 17]. These XRD results are in agreement with the SEM images as reported in **Figure 5**. The kaolin layers in **Figure 5A** break down by the geopolymerization process to obtain geopolymers with a semi-uniform nano-pore network as shown in **Figure 5B**. We also note the presence of bundles of tubes forming LC fiber. Both phases, whether the porous geopolymeric matrix or vascular LCF, help to increase the surface moisture of the material, which helps in the applications of passive cooling systems, especially in hot and dry regions. On the other hand, we note that introducing LCF contributed significantly in improving the mechanical properties of geopolymeric products, where the

#### **Figure 5.** *SEM images of the precursor (A), geopolymer matrix (B), and the LCF cross section (C) [8, 11].*

#### **Figure 6.**

*Mechanical and physical properties of geopolymers (Sk-geopolymer) and geopolymer composite (LG-composite): Compressive strength (A), Bulk density (B), and Stress-strain curve (C) [11].*

#### **Figure 7.** *HFO granules (point 1) in the geopolymeric matrix (point 2).*


#### **Table 3.**

*Concentration (ppm) of leached metals from crude HFO and HFP geopolymer matrix after immersion in pH = 7 for 1 day.*

compressive strength was doubled as shown in **Figure 6A**. It was observed also that the density of products was reduced by up to 10%, **Figure 6B**, thanks to the addition of vascular LC fiber as reinforcement. This reduction in density is due to the fact that these fibers exhibit low bulk density compared to the geopolymer matrix. The most important influence for LC fibers on the mechanical properties of geopolymers is to significantly increase the tensile strength as shown in **Figure 6C**. Brittle geopolymer matrix also acquires the ductile failure thanks to LC fibers.

It is observed in this research that the LCF geopolymer composites have attracted mechanical and physical properties. In addition, the presence of multiple structures of porous networks, whether the geopolymeric matrix or the vascular LC fibers, plays an active role in the manufacture of passive cooling materials. Thus, these materials can be used as construction materials and in reducing the energy consumed in the indoor conditioning.

**7**

*Introductory Chapter: Case Studies of Functional Geopolymers*

use as construction materials in specific applications.

**3. Conclusions**

**Author details**

Mazen Alshaaer

**2.3 Immobilization and stabilization of toxic wastes in geopolymers**

Geopolymers have been used in recent years as a matrix for immobilization and stabilization of toxic wastes. The finished products can be used for specific construction purposes as well. Therefore, this geopolymerization process achieves several goals at once. In this study [18], heavy oil fly ash (HFO) containing toxic elements such as Ni, Cr, Pb, etc. was added to the geopolymeric matrix as a filler. As can be seen in **Figure 7**, the granules of the HFO are fixed in the geopolymers. The resultant HFO geopolymer exhibits mechanical properties comparable with pure geopolymer [18]. As for the examination of the immobilization of toxic elements, it is observed in **Table 3** that these elements were fixed in the geopolymeric matrix and they were not leached in water after a full day of immersion in water. Accordingly, this research achieves several objectives: the use of geopolymers in the recycling of HFO as a waste and the stabilization of toxic elements, in addition to its

There are several challenges and drawbacks facing the commercialization of geopolymers as an alternative to conventional cement and other conventional materials in construction. One important strategy to overcome these challenges is the manufacture of functional geopolymers with multiple uses. Three different applications of polymers in the fields of water purification, passive cooling systems, and waste recycling were presented in this introductory chapter. It is noticeable that the results are of great importance in many applications and confirm that this strategy will play a key role in the commercialization of geopolymers as products

with multiple uses in engineering and environmental applications.

Department of Physics, College of Science and Humanities in Al-Kharj,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia

\*Address all correspondence to: mazen72@yahoo.com

provided the original work is properly cited.

*DOI: http://dx.doi.org/10.5772/intechopen.90363*
