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Structural and Chemical Analysis of New Cement Based on Eggshells and Sand from Dunes (Southern West of Algeria) Stabilized by PET

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Abdelghani Brahimi, Mourad Meghachou, Hicham Abbad, Abdelkader Rahmouni, Redouane Chebout, Khaldoun Bachari, Fatima Zohra Zeggai and Mohammed Belbachir

Submitted: March 21st, 2021 Reviewed: May 11th, 2021 Published: May 4th, 2022

DOI: 10.5772/intechopen.98346

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In this chapter, we present our study of geopolymers and hybrid geopolymers synthesized with treated fly ash from eggshells (FAES) and sand from the dunes of southern Algeria using activators such as NaOH and Na2SiO3, respectively, in addition to the organic polymer polyethylene terephthalate (PET). Several parameters have been modified, such as alkali concentration and percentage of activators and PET, with the objective to improve the quality of the desired geopolymers and hybrid geopolymers. The main objective of this work is to study the use of waste PET in the matrix of this new material to replace Portland cement, which is widely used today, as well as develop ecological building materials that are durable and lightweight and prevent chemicals from attacking old structures. Through optical and electron microscopy, we studied the effect of the addition of PET on the structure of our geopolymer material and on the bond and interface areas between the aggregates and the matrix. The microstructural analysis discussed here refers to specimens containing 5% PET by weight. We observed that PET contents significantly altered the structure and morphology of the samples.


  • fly ash of eggshells (FAES)
  • sand dune
  • cement
  • microstructure
  • analysis
  • construction
  • Young’s modulus
  • structure
  • silica fume

1. Introduction

Geopolymers can replace cement in various forms of construction work and the manufacture of concrete and mortars, and they have very important mechanical characteristics given their three-dimensional aluminosilicate network [1]. The use of geopolymers instead of Portland cement is justified by the reduction in CO2 emissions and energy savings [2]. Dune sand is a widely available natural resource that can be integrated into the construction industry, which needs more development [3]. The process of geopolymerization of mixtures of sand and fly ash is used to produce a new material composed of very fine elements. Mortars composed of modified polymers are building materials with excellent properties and can replace mortars based on Portland cement [4]. Polymers have been used to enhance the waterproof properties and modify the mechanical properties of concrete and mortars as well as reinforce adhesion [5]. The literature specifies that the characteristics of concrete and mortar modified by polymers depend mainly on the polymer percentage or on the ratio between the cement and polymer, that is, the ratio of the value of the mass of solid polymers contained in a polymer-based addition to the value of cement in a polymer, concrete, or modified mortar [6]. Among plastics, polyethylene terephthalate (PET) is the most widely used to produce products such as consumer goods, beverage bottles,and food packaging [7]. PET bottles have replaced traditional glass bottles for liquid storage due to their ease of handling, light weight, and possibility of storage [8]. Fly ash is a fine and powdery material produced from coal when generating electricity. When coal is used in a power plant, it is crushed into a very fine powder that will be blown into the furnace of the plant [9]. The hydrogen and carbon in the coal are depleted, leaving molten noncombustible particles rich in alumina and silica. After the solidification of these particles in the fly ash state, these very fine powders easily enter the atmosphere and pollute water and the air [10]; they can cause respiratory problems if not properly eliminated. In addition, fly ash deposited on leaves and plants in agricultural fields near electrical power plants can diminish crop yield. However, when used properly, fly ash can help to conserve natural resources [11]. The manufacture of Portland cement is a major contributor of CO2 gas emissions, thus any reduction in the use of cements will result in a reduction in greenhouse gas emissions, possibly reducing emissions to zero. One ton of CO2 is emitted for each ton of Portland cement produced [12]. Thus, replacing Portland cement with fly ash will eliminate CO2 emissions. If all the fly ash produced is used instead of carrier cement in the various construction works of buildings, roads, and bridges, it is estimated that the reduction in CO2 emissions will be equivalent to the elimination of 25% of vehicles worldwide [13]. This chapter summarizes the scientific advances in the preparation, fabrication, properties, and applications of fly ash of eggshells (FAES) and sand dune-based geopolymer and geopolymer hybrids. The production of mixed geopolymers and hybrid geopolymers is mainly based on alkali-activated geopolymerization, which can occur under mild conditions and is considered a cleaner process due to much lower CO2 emissions than that from the production of cement [14].


2. Experiment

2.1 Materials and methods

2.1.1 Materials

The basic material used in these experiments is the original siliceous sand of the sand dunes of southwest Algeria. First, 100 g of dry sand was treated with 200 ml of hydrochloric acid over a period of 30 minutes at room temperature. Then, all the leaching tests were carried out in a 250-ml glass beaker placed on a magnetic stirrer with a control unit to ensure the homogeneity of the product at stable temperatures. When the required temperature (80°C) of the contents of the beaker (100 ml of acid) was reached, approximately 30 g of dry sand was added to the beaker while the contents of the beaker rotated at a constant speed of 250 rpm. The beaker was covered to avoid losses by evaporation. From the leaching solution, a sample amount of our prepared mixture was taken at predetermined time intervals, filtered, washed several times with distilled water to remove any unspent acid, and then dried at 110°C for 1 hour. All the experiments were repeated for more precision. The chemical composition of the silica sand prepared for this study was determined by X-ray fluorescence (XRF). Table 1 presents the study results.

OxideContent %OxideContent %

Table 1.

Chemical composition of the sand dune (western Algeria).

The eggshells were used as raw material to prepare the fly ash. They were washed first with distilled water and then with an acid solution (1 M HCl) to reduce the level of limine (CaO) and remove impurities. After drying, and when all moisture was removed, the material was calcined at temperatures ranging from 700–850°C after drying at 25°C. XRF analysis was performed to characterize the fly ash sample (see Table 2). It is evident that the sample is very rich in silica and eliminated, which makes it a suitable raw material to begin the geopolymerization process. The dimensions of the fly ash particles are less than 100 μm. The main element in pork roosters is CaO (63.69%).

OxideContent %OxideContent %

Table 2.

Chemical composition of the fresh fly ash of eggshell (FAES).

Water glass, also called sodium silicate (Na2SiO3), was synthesized at the chemistry laboratory of Polymer Oran 1, University of Algeria. Then, 100 g of sand was washed with an acid solution (1 M HCl), dried at 25°C, and mixed with 200 g of sodium hydroxide (13 M NaOH). A platinum crucible was placed in an electric furnace at 850°C for 1 hour at a heating rate of 5°C/min. The mixture was melted, and the melt was cooled and solidified in the crucible. This method allowed us to synthesize 75 g of water glass nanomaterials (sodium silicate). This white powder was dried at 25°C to allow us to carry out microstructural, chemical, and mineralogical analyses.

Thermoplastic polyester (PET) has acceptable mechanical characteristics; in particular, a tensile modulus of elasticity of 2.89 GPa and a flexural modulus of elasticity of 2.36 Gpa, with a tensile strength of 58 Mpa and resistance to chemical attack. It is a semicrystalline polymer with a density melting point (specific gravity) of 1.28 to 1.39 g/cm3. The very fine grinding of plastic waste, such as drink bottles, gives us PET powder.

2.1.2 Methods

We analyzed the morphology of the raw fly ash samples using scanning electron microscopy (SEM;LEO SEM 1450), the molecular structure using Fourier-transform infrared spectroscopy (FTIR;Perkin Elmer 100 spectrum), the mineralogy using X-ray diffraction (XRD; X-ray generator, Philips PANalytical pw3830), and the chemical composition using XRF (dispersion spectrometer, Philips 1404 wavelength).

2.2 Synthesis of different forms of geopolymers

The synthesis of geopolymers is carried out by mixing source materials containing aluminosilicate (sand dune), fly ash with a high calcium (Ca) classified as (F), and an alkaline solution (NaOH 13 M). The source materials used are FAES washed with acidic solution (HCl 1 M) to eliminate impurities and minimize the rate of calcium and limine as producers of carbon dioxide (CO2), calcined at 700 to 900°C, and sand dune (Algerian sand) leached with acid solution (HCl 1 M) and mixed with alkaline solution (NaOH 13 M) to prepare sodium silicate (Na2SiO3). In the last step, four samples of geopolymers were prepared for comparison, as shown in Table 3. The final product was placed in molds at room temperature for 24 hours and then stored in an oven at 80°C for another 24 hours. Table 4 presents the results of the XRF assay analysis. The sample is full of silica and limine, which is a suitable raw material to begin the geopolymerization process.

Geopolymers (GP)Mass (g) ratio
GP1: FAES, Na22SiO3, NaOH, H2O3.00, 1.75, 1.00, 2.25
GP2: FAES, Na2SiO3, NaOH, H2O, SiO23.00, 1.75, 1.00, 2.25, 0.5
GP3, FAES, Na2SiO3, NaOH, H2O, Al2O33.00, 1.75, 1.00, 2.25, 0.5
GP4, FAES, Na2SiO3, NaOH, H2O, Fe2O33.00, 1.75, 1.00, 2.25, 0.5

Table 3.

Geopolymers synthesis procedure (GP).

OxideContent %OxideContent %

Table 4.

Chemical composition of the synthesized geopolymer (GP-2).

2.3 Synthesis of hybrid geopolymers

The synthesized organic–inorganic hybrid geopolymers consist of FAES and Na2SiO3 from sand dunes (southern Algeria) activated by alkaline solution (13 M NaOH) in which a percentage of PET was incorporated. Four different formulations of hybrids were prepared and characterized, as shown in Table 5.

Geopolymers hybrid (GHPs)Mass (g) ratio
GHP1: FAES, Na2SiO3, H2O, PET3.00, 1.75, 1.00, 2.25, 0.5
GHP2: FAES, Na2SiO3, NaOH, H2O, SiO2, PET3.00, 1.75, 1.00, 2.25, 0.5, 0.5
GHP3: FAES, Na2SiO3, NaOH, H2O, Al2O3, PET3.00, 1.75, 1.00, 2.25, 0.5, 0.5
GHP4: FAES, Na2SiO3, NaOH, H2O, Fe2O3, PET3.00, 1.75, 1.00, 2.25, 0.5, 0.5

Table 5.

Geopolymers hybrid synthesis procedure (GHP).

FAES and sand from the dunes were used as the principal sources of aluminosilicates because they are the cheapest aluminosilicates with a good degree of purity. Moreover, this raw material improves the mechanical strength of and reduces salts and CO2 in the final product. Table 2 presents the compositions of the raw material. The mixture of fly ash and sand was sieved to obtain a fine powder with an average diameter of 100 μm. The powder was added gradually to an alkaline solution (NaOH 13 M) previously prepared by mixing a sodium silicate solution with SiO2/Na2O ratio = 2 and sodium hydroxide with Na2SiO3/NaOH ratio = 1.5. The final composition of the synthesized geopolymer can be expressed as Si, Al, Na, and H2O. To synthesize geopolymer/PET hybrid systems, PET was also added in part to the alkaline solution as well as to the mixture of fly ash and sand dune during the mixing phase. The resulting product was stirred mechanically for approximately 30 min to reach good homogenization and then poured into plexiglass-clad molds and sealed. The molds were placed in an oven for 24 hours at 30°C to avoid any possible thermal degradation of the polymer and successively stored for 28 days at room temperature.


3. Results and discussion

Geopolymers and hybrid geopolymers or cementitious materials in general were synthesized using FAES activated by alkali solution and silicate sodium from sand from the dunes in southern Algeria. Results confirm that quartz is the main component in the different forms of the prepared geopolymers, along with calcite, hematite, mullite, and ferrite. These are the main elements responsible for networking in geopolymer matrixes. Thus, reactivity under alkaline conditions is affected only in the amorphous section of these reagents and acts as an indicator of geopolymer and a substitute for metakaolin.

3.1 Analysis of geopolymers and hybrid geopolymers

3.1.1 Analysis of different form of geopolymers

The prepared geopolymers generally contain a large percentage of quartz in the form of silica (SiO2), which exhibits better resistance to external actions due to the hardness of the material. Local conditions and sources influence the chemical composition of geopolymers [15]. XRF is the most reliable technique for finding the lowest concentrations of the elements in a prepared sample, as shown in Table 4.

Ceramic materials can be prepared by geopolymers. The preparation and synthesis of our geopolymers is carried out by a chemical solution of alkali silicate. Solid aluminosilicates have been added from the source of the sand of the dunes. FAES is very rich in calcium, and with the presence of 13 M NaOH as an alkaline solution, the XRD models studied show remarkable differences in the influence of the fly ash samples on the geopolymers due to the position and shape of the quartz peaks and bumps (lower and upper) (Figure 1). The XRD diagrams of the geopolymer based on fly ash confirm that the geopolymer materials are essentially composed of an amorphous character under X-ray, knowing that the diffraction crystals are the same as the original materials (calcite, mullite, limine, hematite, and quartz). An amorphous peak was observed, as the value of 2θ on the diffraction pattern ranged from approximately 20 degrees to 69 degrees, given the presence of amorphous glassy materials [16]. With activation of the ash by NaOH (alkaline solution), it was found that the diffractogram of the original ash was changed [17]. A slight shift of 19–50 degrees to 20–69 degrees (2θ) of the value of the peak attributed to the phase of the vitreous form of the original fly ash was observed. Ahydrate gel in the form of alkali aluminosilicate was formed as a result of this transformation. This hydrate gel is the main material that allows the initial reaction of geopolymerization of the geopolymeric materials mentioned in the diffraction diagrams [18]. With activation, the crystalline stages (hematite, quartz, calcite, mullite) observed inside the initial material remained practically without modification [19]. For the geopolymer model, the basic fly ash mineralogy does not change much, a result that agrees with the literature [20].

Figure 1.

XRD patterns of geopolymers (GP1, GP2, GP3, and GP4) with a NaOH molar ratio variation of 13 M.

The SEM images shown in Figures 2 and 3 show a change in morphology in most geopolymer samples compared to fly ash. Sodium silicate (Na2SiO3) was the most present element in all the samples studied (GP1, GP2, GP3, and GP4). In addition, after approximately 1 hour of preparation, a greater quantity of fly ash reacted positively. The microstructure of the geopolymers was heterogeneous and the matrix was full of loosely structured fly ash grains of different sizes, except in sample GP2, as shown in Figure 3, in which we observed a good microstructure. In the gel, several circular shaped cavities do not appear. Here, we suggest that a significant amount of spherically shaped fly ash reacts, and this result shows complete transformation within the system after only 1 hour and the reaction up to 78.93%. Finally, we found that the number of reactions taking place in a paste that forms the geopolymer develops as a function of the molar percentage of SiO2/Al2O3 and the reactivity ratio of the fly ash, which is rich in calcium (Ca). The “GP” geopolymers prepared by us have many characteristics that make them economical materials for construction [21]. The formation of geopolymer-type concretes is accomplished by the addition of water to a geopolymer, keeping in mind that the different shapes of geopolymers have a relatively porous structure. The water molecules limit the formation of gases before the gel hardens in the structure [22]. The geopolymer is formed when water is added to FAES in alkaline activation solutions. After adding FAES to the geopolymers, the number of gas-producing compounds is known, and they are trapped to produce a microstructure within the cured material [23]. When mixing water and geopolymers, the chemical reactions liberate different gases that are entrapped in the structure, especially CO2. When the oxides of silicone and calcium as well as metallic aluminum in an alkaline solution are conserved, carbon oxide and H2 are removed, creating aluminum hydroxide. Finally, the CO2 molecules will be blocked in the structure of the geopolymer, which means that the product is very reactive.

Figure 2.

SEM of the foamed geopolymer according to the percentage of fly ash eggshell after 1 hour (GP1, GP2, GP3, GP4).

Figure 3.

SEM of the foamed geopolymer according to the percentage of fly ash eggshell after 24 hours (GP1, GP2, GP3, GP4).

3.1.2 Analysis of different forms of prepared geopolymer hybrids

XRD techniques were used for a wide variety of material characterization studies. The XRD results show some qualitative differences in the hydration rate due to the incorporation of PET polymer. Figure 4 shows the X-ray patterns of the composites with 5% PET and composites without polymer PET (Figures 3 and 4). The main compounds observed are large amounts of CaCO3, calcium oxide, and quartz resulting from anhydrous fly ash and sand dune, respectively. The peak intensity in 18, 52 degrees to 67, 37 degrees has been considered a region of the quantity of CaCO3. Therefore, it is also noted here that at a hybrid geopolymer ratio of 5%, a slight increase in the peak intensity compared to the unmodified geopolymer is observed. Furthermore, CaCO3 crystals may produce sharper reflection in the presence of PET polymer due to a change in the orientation pattern of the crystals. Based on SEM micrograph analysis (Figures 5 and 6) and chemical composition (Table 6), it is possible to explain this variation in terms of the fact that PET addition causes a progressive decrease in the amount of calcium carbonate and calcium oxide in the hybrid composites compared to the unmodified geopolymer. These results agree with previous studies [24].

Figure 4.

XRD patterns of hybrid geopolymers (GHP-1, GHP-2, GHP-3, and GHP-4) with a NaOH molar ratio variation of 13 M.

Figure 5.

SEM of the foamed hybrid geopolymer according to the percentage of fly ash eggshell after 1 hour (GPH1, GPH2, GPH3, GPH4).

Figure 6.

SEM of the foamed hybrid geopolymer according to the percentage of fly ash eggshell after 24 hours (GPH1, GPH2, GPH3, GPH4).

OxideContent %OxideContent %

Table 6.

Chemical composition of the synthesized hybrid geopolymer (GHP-2).

Images of the SEM micrograph in Figures 5 and 6 show the microstructure of the mixture hybrid geopolymer based on PET with sand dune (quartz) after 1 hour. The PET composite indicates a weak interfacial transition zone in the hybrid geopolymer matrix interface at 1 hour, which is related to the large shrinkage of the geopolymer paste, as revealed by XRD [25, 26]. There is approximately less distance between PET and the surface of the geopolymer matrix. Furthermore, some microcracks also formed in the hybrid geopolymer. As shown in Figures 5 and 6, PET was placed in the crack zone when the specimen was subjected to a chemical reaction after 1 hour. The PET might deform and lengthen, rupture, or pull out because of the applied stress at the fiber section in a crack zone.


4. Conclusion

The synthesis of a new geopolymer-type material using a hydrothermal process was carried out after the preparation of base materials such as silica and alumina. This work describes the synthesis and valuation of FAES in the raw and activated states as well as sand from the dunes of southern Algeria for the preparation of geopolymer mortars by alkaline activation. The characterization and preparation of sodium silicate (Na2SiO3) were carried out in specialized laboratories in Algeria. Chemical analysis by XRF shows that the sand of the dunes is very rich in quartz ranging from 90.04% to 99.16% silica; in addition, a low concentration of other oxides was observed. However, microscopic SEM observations of the sand revealed the presence of pores with differing morphologies (e.g., rounded, elongated, and angular). The influence of FAES is important with respect to water penetration, and this performance is better than that of ordinary Portland cement. In addition, we observed very good fire resistance with a reduction in CO2 emissions. SEM also revealed uniform and correct distribution of the eggshells over the whole matrix phase. It was also found that there is good adhesion between the sand particles and eggshell particles, due to the sand being rich in aluminum and silicon. From the alkaline activation of eggshells, it was found that FAES can be used with sand from dunes to obtain geopolymers and hybrid geopolymers that can be used as green and durable concrete.



We thank all staff of the research center in physicochemical analysis (CRAPC) of Tipaza, Algeria, for their kind cooperation and characterization (XRF, X-ray, SEM). We wish the best of luck to Prof. Mohammed Belbachir (Oran 1 University) and Prof. Mourad Megachou (University DjillaliLiabes of Sidi Bel Abbes) for their support in making the publication of this research possible.


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Written By

Abdelghani Brahimi, Mourad Meghachou, Hicham Abbad, Abdelkader Rahmouni, Redouane Chebout, Khaldoun Bachari, Fatima Zohra Zeggai and Mohammed Belbachir

Submitted: March 21st, 2021 Reviewed: May 11th, 2021 Published: May 4th, 2022