**Alkali Activated Cements**

**Chapter 14**

**Provisional chapter**

**Clay-Based Materials in Geopolymer Technology**

**Clay-Based Materials in Geopolymer Technology**

DOI: 10.5772/intechopen.74438

The term "geopolymer" was introduced by Davidovits in the 1970s. The prefix "geo" was selected to symbolize the constitutive relationship of the binders to geological materials, natural stone and/or minerals. Geopolymer is mineral polymers of inorganic polymer glasses with structure resembling natural zeolitic materials. Previously, geopolymer formation used source materials such as clay (e.g. kaolin and calcined kaolin) or industrial by-product (e.g. slag and fly ash). The precursor material plays an important role in the formation of geopolymer. The source material provides silicon (Si) and aluminum (Al) for reaction by an alkali activator solution. The Si and Al contents in the source materials dissolve in the alkaline activator solution and then polymerize to form a polymeric Si-O-Al-O framework which becomes the binder. Geopolymeric materials are attractive because of their excellent mechanical properties; durability and thermal stability can also be achieved. Owing to their low calcium content, they are more resistant to acid attack than materials based on Portland cement. In addition, they are of great interest because of the reduced energy requirement for their manufacture and the higher sustainability. Recently the search for alternative low cost and easily available materials led among others to Clay. Clay generally consists of a mixture of different clay minerals and associated minerals, which are strongly affected by the nature of the parent rocks. These materials are extensively distributed over the surface of the world and may show certain reactivity after a thermal activation process shows a great potential to be utilized in geopolymer technology. This article presents the potential of different types of clay as the source materials for geopolymerization reaction in terms of morphological properties. Moreover, the mechanical and microstructural properties of geopolymer made with vari-

ous kinds of clay and its potential application are also presented.

**Keywords:** geopolymer, inorganic polymer, clay

© 2016 The Author(s). Licensee InTech. 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, provided the original work is properly cited.

© 2018 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, provided the original work is properly cited.

Mohd Mustafa Al Bakri Abdullah, Liew Yun Ming,

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Heah Cheng Yong and

**Abstract**

Muhammad Faheem Mohd Tahir

Muhammad Faheem Mohd Tahir

Mohd Mustafa Al Bakri Abdullah,

Liew Yun Ming, Heah Cheng Yong and

http://dx.doi.org/10.5772/intechopen.74438

#### **Clay-Based Materials in Geopolymer Technology Clay-Based Materials in Geopolymer Technology**

DOI: 10.5772/intechopen.74438

Mohd Mustafa Al Bakri Abdullah, Liew Yun Ming, Heah Cheng Yong and Muhammad Faheem Mohd Tahir Mohd Mustafa Al Bakri Abdullah, Liew Yun Ming, Heah Cheng Yong and Muhammad Faheem Mohd Tahir

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.74438

#### **Abstract**

The term "geopolymer" was introduced by Davidovits in the 1970s. The prefix "geo" was selected to symbolize the constitutive relationship of the binders to geological materials, natural stone and/or minerals. Geopolymer is mineral polymers of inorganic polymer glasses with structure resembling natural zeolitic materials. Previously, geopolymer formation used source materials such as clay (e.g. kaolin and calcined kaolin) or industrial by-product (e.g. slag and fly ash). The precursor material plays an important role in the formation of geopolymer. The source material provides silicon (Si) and aluminum (Al) for reaction by an alkali activator solution. The Si and Al contents in the source materials dissolve in the alkaline activator solution and then polymerize to form a polymeric Si-O-Al-O framework which becomes the binder. Geopolymeric materials are attractive because of their excellent mechanical properties; durability and thermal stability can also be achieved. Owing to their low calcium content, they are more resistant to acid attack than materials based on Portland cement. In addition, they are of great interest because of the reduced energy requirement for their manufacture and the higher sustainability. Recently the search for alternative low cost and easily available materials led among others to Clay. Clay generally consists of a mixture of different clay minerals and associated minerals, which are strongly affected by the nature of the parent rocks. These materials are extensively distributed over the surface of the world and may show certain reactivity after a thermal activation process shows a great potential to be utilized in geopolymer technology. This article presents the potential of different types of clay as the source materials for geopolymerization reaction in terms of morphological properties. Moreover, the mechanical and microstructural properties of geopolymer made with various kinds of clay and its potential application are also presented.

**Keywords:** geopolymer, inorganic polymer, clay

© 2016 The Author(s). Licensee InTech. 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, provided the original work is properly cited. © 2018 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, provided the original work is properly cited.

## **1. Introduction**

In 1978, the word "geopolymer" was introduced by Davidovits [1]. In general, geopolymer is an inorganic polymeric material formed through the reaction between aluminosilicate sources and highly alkaline silicate solution, followed by curing at ambient or slightly higher temperature [2]. The formation process is termed as geopolymerization reaction.

Geopolymer has an empirical formula of:

$$M\_{\text{\tiny\text{\tiny\text{\tiny\text{\tiny\text{\tiny\text{\tiny\text{\tiny\text{\text}}}}}}} \left\{ - \left( \text{SiO}\_{2} \right)\_{\text{\tiny\text{\textgreater}}} - \text{AlO}\_{2} \right\} \cdot w \text{ H}\_{\text{\tiny\text{\textquotedblleft}}} \text{O} \tag{1}$$

**2. Aluminosilicates**

**3. Kaolin/kaolinite**

and SiO2

The aluminosilicate sources are materials rich in alumina and silica content (e.g. ashes [11–14], clays [15, 16] or slag [17, 18]). Some other natural and artificial silicoaluminates such as zeolite [19] and magnesium-contained minerals [20] have also been used as an important source of Si4+ and Al4+ ions in the geopolymer binding system. Normally, the total composition of Al2

Kaolinite is the most common clay mineral used in geopolymer synthesis. It has 1:1 uncharged

(gibbsite) sheet linked by sharing oxygen atoms. The layers are held together by weak van der

ter, the utilization of clay or clay minerals in geopolymer formation is discussed.

dioctahedral layer structure (**Figure 2a**) whereby the layers are (Si2

**Figure 2.** Structure of kaolinite (above) and microstructure of kaolinite (below) [22].

waals and hydrogen bonds leading to the layered structure (**Figure 2b**).

is more than 70%, preferable in reactive amorphous phase [3, 21]. In this book chap-

O5 )*n*

2− sheet and the Al(OH)3

Clay-Based Materials in Geopolymer Technology http://dx.doi.org/10.5772/intechopen.74438

O3

241

where M is cation such as K+ , Na+ or Ca2+; *n* is the degree of polycondensation; *z* is 1, 2, 3 and *w* is the amount of binding water. It has three-dimensional Si-O-Al polymeric networks ranging from amorphous to semi-crystalline. Tetrahedral SiO4 and AlO4 are linked alternately by sharing oxygen atom as shown in **Figure 1**. As refer to **Figure 1**, the terminology of geopolymers can be categorized into three forms which are poly(sialate), poly (sialate-siloxo) and poly (sialate-disiloxo). The Al is in IV-fold coordination [3, 4]. This leaves a negative charge in the IV-fold coordinated Al that is charge-balanced by cations (Na+ , K+ , Li+ , Ca2+, Ba2+, NH4+ and H3 O+ ). The charge-balancing by cations is important in determining the structural integrity and fragility of geopolymers [5].

The cations is usually contributed by alkaline silicate solution which is a mixture of alkali hydroxides (NaOH or/and KOH) and silicate solution (Na<sup>2</sup> SiO3 or/and K2 SiO3 ) [6–8]. The alkali hydroxide is required for the dissolution of aluminosilicates while alkali silicate acts as binder, alkali activator and dispersant or plasticizer [9]. The alkali silicate solution contributes certain amount of SiO2 for the geopolymerization reaction [10].

**Figure 1.** Geopolymer systems based number of siloxo Si-O units [2].
