Geopolymer Products from Jordan for Sustainability of the

Environment

Journal: MS&T 2010 Ceramic Transactions

Manuscript ID: 37271

Symposium: Green Technologies for Materials Manufacturing and Processing II

Date Submitted by the Author:

08-Aug-2010

Complete List of Authors: Khoury, Hani; University of Jordan

GEOPOLYMER PRODUCTS FROM JORDAN FOR SUSTAINABILITY OF THE

ENVIRONMENT

Hani Khoury*, Yousif Abu Salhah, Islam Al Dabsheh, Faten Slaty, Mazen Alshaaer University of Jordan, Amman, 11942, Jordan Hubert Rahier Research Group of Physical Chemistry and Polymer Science (FYSC), Vrije Universiteit Brussel (VUB) Muayad.Esaifan, Jan Wastiels Department of Mechanics of Materials and Constructions (MEMC), Vrije Universiteit Brussel (VUB) ABSTRACT Geopolymerization is the process of polymerizing minerals with high silica and alumina at low temperature by the use of alkali solutions. Geopolymers could be a substitute for Portland cement and for advanced composite and ceramic applications. The geopolymer technology would eliminate the need for energy requirement as they may be cured at ambient temperature. Current research at the University of Jordan concentrates on developing building products (geopolymers) through geopolymerization. The goal is to produce low cost construction materials for green housing. The produced construction materials are characterized by high strength, high heat resistance, low production cost, low energy consumption, and low CO2 emissions. The results have confirmed that natural kaolinite satisfy the criteria to be used as a precursor for the production of high quality inexpensive, stable materials. The kaolinite geopolymer specimens from El-Hiswa deposits with compressive strength of 44.4MPa under dry conditions and 21.8 MPa under water immersed conditions were obtained by using around 16 % NaOH at 80oC after 14 hours. At higher temperatures these geopolymers maintained or improved their mechanical and physical performance after heating up to 600 °C. At 400 °C the compressive strength was 52.1 MPa under dry conditions and was 39.1 MPa under water saturated conditions. At 1000°C the mechanical strength was 15.1 MPa under dry conditions and was10.5 MPa under water saturated conditions. The density of the geopolymers has dropped down at dry conditions from 2.02 at 80 °C to 1.93 at 1000 °C. The presence of two refractory phases’ sodalite and mullite make them sufficiently refractory at 1000°C. The lower densities at higher temperatures enable their use as an insulating material. Keywords: Geopolymers, kaolinite, Jordan, green construction material

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INTRODUCTION Geopolymer technology has recently attracted researchers because the products are non-combustible, heat-resistant, formed at low temperatures, fire/acid resistant and have environment friendly applications [1, 4, 11 and 15] Geopolymers have been proposed as an alternative to traditional Ordinary Portland Cement (OPC) for use in construction applications, due to their excellent mechanical properties [2]. Their physical behavior exceeded that of Portland cement in respect of compressive strength, resistance to fire, heat and acidity, and as a medium for the encapsulation of hazardous or low/intermediate level radioactive waste [3,4] Chemical polymerization reactions of aluminosilicate minerals could be hardened and transformed into aluminosilicate geopolymers as a result of polycondensation [5]. Clay minerals (calcined clay), mining wastes, and slag are considered as a good source of aluminosilicate precursor. Geopolymers consist of three-dimensional mineral phases resulting from the polymerization of two dimensional sheet-like aluminosilicates in an alkaline solution. The exact mechanism of the geopolymerization is not known precisely until now. The structure maintains electrical neutrality as a result of aluminum substitution for silicon in the tetrahedral layer and the compensation of the negative charge by the available cations such as Na+. Inexpensive functional fillers like silica sand and zeolitic tuff were used in different proportions to help in stabilizing the produced geopolymers [6].The excellent mechanical properties of the geopolymers have attracted the researchers to focus on the effect and application of different raw materials on the compressive strength, chemical impurities, and the effect of the chemical composition of the alkali activating solutions [6]. Recently, geopolymers produced from kaolinite/NaOH system gave a higher unconfined compressive strength values up to 52 MPa for dry test. This value has been increased to 57 MPa by the immersion of the geopolymer samples in 10% solution of triethylene glycol. The maximum obtained unconfined compressive strength is 90 MPa, this high value was obtained by using rock wool as an additive material during the geopolymerization process and heating to 500 °C for one day [7]. New low temperature functional geopolymeric materials were prepared exhibiting adsorption capacity for pollutants [8, 9]. Only a relatively small number of investigations have specifically studied the effects of high-temperature on geopolymeric gels [10].The thermal properties (dehydration and shrinkage) were only investigated of a geopolymer produced from metakaolin and sodium silicate solution. [11 and 12]. The samples exhibited shrinkage of approximately 6% during dehydration, with significant densification observed at approximately 800 °C. The thermal behavior up to 1000°C of geopolymers produced from metakaolin activated with sodium silicate solutions was studied and characterized [6, 11, and 12]. The following work will focus on evaluating the influence of high temperature on the mechanical performance and stability of low temperature geopolymers produced from kaolinitic raw material. The thermal behavior and phase transformation of the Na-geopolymers will be characterized to investigate its possible use as a low temperature refractory material (<1000°C).

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MATERIALS AND TECHNIQUES Materials: Jordanian kaolinitic clay (as a source of aluminum silicate) with a purity of 60% from El-Hiswa deposit was used. The kaolinitic clay deposits are located in the south of Jordan about 45km to the east of Al-Quweira town [8, and 13]. Preparation of the Jordanian kaolinite samples involved crushing, grinding and sieving of an oven dried sample (at 105 oC) to obtain a grain size less than 425µm. Then the samples were mixed in 50 L plastic drum for several times for homogenization. The plasticity limit of El-Hiswa kaolinite was measured according to the ASTM D4318 [14] and was found to be 22%. Silica sand with 99% quartz content was used as a filler to provide high mechanical properties. The sand was washed with distilled water and sieved to obtain a grain size between100 and 400 µm. NaOH (GCC, 96%) was used as an alkaline activator for the dissolution of aluminoslicate precursor. Water was the reaction medium and the optimum water content was close to the plasticity limit. The optimum curing time at 80oC was determined to be around 14 hours [8 and 15]. The optimal ratios of the mixture were determined depending on the best compressive strength, the optimal curing temperature and time for the geopolymer specimens [8 and 15]. The composition of the optimized mixture to produce geopolymers at 80oC after 14 hours curing time is given in Table 1. Table 1. Composition of the geopolymer mixture

Composition Clay Sand NaOH H2O

% 100 100 16 22 Fabrication of geopolymers’ specimens: The geopolymers’ specimens were prepared from from El-Hiswa kaolinitic deposit as a source of aluminum silicate. Silica sand was used as a filler to provide high mechanical properties (SS) and NaOH solution was used as an alkaline solution. Homogeneous mixtures were prepared (Table 1) using a controlled speed mixer (mixing speed was 107rpm for 2 min followed by 198 rpm for 10min). Good mixing is important to obtain homogeneous and comparable specimens and to avoid the agglomeration of the mixture. Each mixture (series) was divided into specimens (50 g each). The mixture was molded immediately after weighing to avoid drying and decrease of the workability of the mixture. The paste was molded in a stainless steel cylinder (diameter of 25mm and height of 45mm) at a pressure of about 15MPa (Carver hydraulic laboratory press). The molded specimens of each series were cured by placing them in a ventilated oven (Binder-ED115) at 80 ◦C for 24 h. After curing, the specimens were cooled down at room temperature. The specimens were tested for physical properties and characterized using microscopic and XRD techniques. The compressive strength for the fabricated heated geopolymer specimens (80 - 1000 °C) was measured using CONTROLS testing machine (Model T106 modified to suit with standard testing), where the load was applied on surface area = (12.5×12.5×π) mm2 and height = 50 mm, and increased by a displacement rate of 2 mm/min. The density for the heated specimens and water absorption of the immersed heated specimens were measured [8 and 15].

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Analytical techniques: The zero measurements (reference) were recorded immediately after curing at 80°C for 24 hours then the geopolymer specimens were heated in the furnace up to 100, 200, 400, 600, 800, and 1000 °C. The required temperature was 24 hours. After heating, the specimens were brought back to ambient temperature before further testing. The properties of interest were measured (e.g. density, strength). An average of at least three specimens was calculated for each test. Thin sections were made for all the heated geopolymer specimens and were studied using the polarized microscope. X-ray diffraction analysis is used to identify crystalline phases of the materials. Representative portions of the ground heated geopolymers were randomly X-rayed using Philips 2KW model, Cu Kα radiation (λ= 1.5418 Å nm) with a scan rate of 2°/min. X-ray diffractograms were recorded for powdered geopolymers at 80, 100, 200, 400, 600, 800, and 1000 °C to detect the phase changes. The SEM/EDX techniques were used for obtaining mineralogical and textural details. The platinum coated geopolymer samples were scanned using high-energy beam of primary electrons in a raster scan pattern using model FEI- INSPECT-F50 of SEM/EDX. 29Si and 27Al spectra were obtained using Bruker AC250 spectrometer that operates at 49.70 MHz and 65.18 MHz for the 29Si and 27Al resonance frequencies, respectively. RESULTS AND DISCUSSION Thin sections were prepared for the heated specimens and studied under the polarized microscope. This microscopic study of the prepared thin sections illustrated that the specimens are massive, cohesive, and show no significant voids. There is a firm and tight adhesion between quartz grains and polymerized kaolinitic matrix in all the studied specimens in the temperature range 100 - 1000 °C (Figure 1).

Fig. 1. A geopolymer specimen heated at 100°C showing polymerized kaolinitic matrix and reaction rims around quartz grains. (XPL, × 100). In the geopolymer specimens heated up to less than 800°C, no significant change in the texture and reaction rims were observed. Reaction rims, possibly sodalite became significant and clear in specimens heated up to 800°C and sodalite was very clear along fractures in specimens heated up at 1000°C (Figure 2).

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Fig. 2. A photomicrograph of reaction rims around and along quartz grains. Isotropic sodalite patches within the matrix. (XPL, × 400). Sodalite was formed at 80°C (Rahier, et al., 2010) and the crystallinity has increased as it was confirmed by the X-ray diffraction results (Fig. 5). Sodalite is an isotropic mineral that forms as a result of the reaction between the decomposed kaolinite (metakaolin) and NaOH in the matrix between quartz grains. The values of the densities of the geopolymer specimens along with compressive strength results are listed in Table 2. Table 2. The physical properties of the geopolymer specimens (densities and compressive strength results) at different temperatures. Temperature

oC Compressive Strength Dry (MPa)

Compressive Strength Immersed (MPa)

Density Dry g/cm3

Density Immersed g/cm3

80 44.4 21.8 2.02 2.18 100 42.1 16.9 2.01 2.20 200 44.1 26.2 1.99 2.19 400 52.1 39.1 1.97 2.20 600 42.2 31.9 1.93 2.17 800 10.0 8.5 1.93 2.14 1000 15.1 10.5 1.93 2.07 The effects of the different temperatures on the compressive strength of the geopolymers’ specimens from El-Hiswa kaolinite after heating at different temperatures up to 1000°C are illustrated in Figure 3. The effects of the different temperatures on the density of the geopolymer specimens are indicated in Figure 4. The kaolinite geopolymer specimens from El-Hiswa deposits with compressive strength of 44.4MPa under dry conditions and 21.8 MPa under water immersed conditions were obtained by using around 16 % NaOH at 80oC after 14 hours. The compressive strength of the geopolymers’ specimens from El-Hiswa kaolinite increases with the increase of temperature up to 52.1 MPa under dry conditions and 39.1 MPa under water immersed conditions at 400°C. Afterwards, the compressive strength decreases with increasing the temperature up to 800°C. The compressive strength of the immersed specimens shows the same trend of dry specimens by increasing the temperature up to 1000°C. The comparison of the compressive strength

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at 80 °C with the tested specimens at higher temperatures has indicated that the geopolymers’ specimens exhibit maximum mechanical strength at 400 °C. The specimens have a high mechanical strength (42.2 MPa) at 600 °C slightly below the initial compressive strength (44.4 MPa). The mechanical performance remarkably has decreased at a temperature higher than 600 °C (10 MPa) then it has increased above 800°C (15.1 MPa).

Fig. 3. Compressive strength of the geopolymers at different temperatures under dry and wet conditions. Figure 4 shows relatively higher densities of the immersed heated specimens. The densities were almost constant above 600 °C for the dried specimens and have decreased for the immersed specimens. The most likely explanation is that the decrease in density is related to the removal of water and breaking of the kaolinite bonds as a result of dehydroxylation at a temperature higher than 400°C, causing the opening of pores and cracks. The almost constant density of the dry specimens from 600-1000°C is attributed to sintering and crystallization of new phases. The decrease in densities of the wet specimens is due to the dissolution of non reactive excessive salts, disappearance of poorly developed Na- Al silicate phases, and to the increase of crystallinity of sodalite, with its channel-like structure.

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Fig. 4. Densities of the geopolymers at different temperatures under dry and wet conditions. The XRD traces of all the geopolymers heated up to 100°C, 200°C, 400°C, 600°C, 800°C, and 1000°C showed that the original geopolymer phases cured at 80 °C. As identified by XRD techniques, the mineral phases of the geopolymer cured at 80 °C [15, 16] are mainly composed of kaolinite, muscovite, quartz, Na-Al silicate phases (Na- phillipsite and natrolite structures). Figure 5 shows the phases change with the increase of temperature. Kaolinite major peaks (7 Å and 3.5 Å) diappear at 600°C as a result of dehydroxylation and change into metakaolinite. Figure 6 illustrated the geopolymer at 100 °C where Na-Al silicate matrix encompassing relicts of unreacted kaolinite. Unstable Na-Al silicate phases (major peaks at 4.7 Å and 3.25 Å) disappear at 800°C. Na-Al silicate phases in general change into sodalite as a result of dehydroxylation and recrystallization. The d-spacings of sodalite at 3.76 Å indicats a better crystallinity at 10 Figures 7 and 8 illustrate to β-quartz and a porous texture with the collapse of kaolinite at 600°C. 00 °C. Mullite appears at 1000°C. It could be seen that α-quartz exhibits phase change to β-quartz at 600 °C. Quartz inverts to high temperature β-quartz at about 573°C. Kaolinite peaks disappeared at 600°C as a result of dehydroxylation, while Na-Al silicate phases disappeared at 800°C. Figures 7 and 8 illustrate to β-quartz and a porous texture with the collapse of kaolinite at 600°C. The drop in the compressive strength values at a temperature higher than 600°C is related to the dehydroxylation of kaolinite and the disappearance of unstable Na-Al – silicate phases possibly as a result of melting and/or recrystallization (Figure 9). The increase in the compressive strength values above 800°C is related to the better crystallinity of sodalite and the appearance of mullite. Sodalite is the result of reaction between metakaolinite and NaOH at high temperature. Heating the geopolymer at 1000°C for 24 h did not show a collapse of the texture and this is an empirical indication of refractoriness. The presence of sodalite and mullite refractory phases should at 1000°C made these geopolymers sufficiently refractory for continuous use up to this temperature. Figure 10 illustrates the porous nature of the geopolymer at 1000 °C, with well developed porous laminated texture and sodalite crystals.

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A geopolymer made with sand as a filler gave a compressive strength of ~ 52 MPa at 400 °C and ~ 42 MPa at 600 °C is sufficiently high. At ~ 1000°C, the compressive strength is much lower (~ 15 MPa). , but as an aluminosilicate geopolymer, it could be used as a thermal insulator. Thermal insulators are used for lining structurally supporting refractory facilities or as mortars in such structures. Hence, a high temperature high strength is not a pre-requisite for their use. The low densities of the geopolymers at higher temperatures, and the presence of zeolites (sieve-like structure) enable their use as insulating materials. CONCLUSIONS Specimens with compressive strength of 44.4 MPa under dry conditions and 21.8 MPa under water saturated conditions were obtained. The obtained materials are environmentally friendly and need only a low energy to be produced. Observations confirmed that natural geomaterials, e.g. kaolinite, satisfy the criteria to be used as a precursor for the production of inexpensive and durable construction materials. At higher temperatures these geopolymers maintained or improved their mechanical and physical performance after heating up to 600 °C. At 400 °C the compressive strength was 52.1 MPa under dry conditions and was 39.1 MPa under water saturated conditions. At 1000°C the mechanical strength was 15.1 MPa under dry conditions and was10.5 MPa under water saturated conditions. The density of the geopolymers has dropped down at dry conditions from 2.02 at 80°C to 1.93 at 1000° C. The geopolymers heated up to 1000°C did not show any major melting. The presence of two refractory phases’ sodalite and mullite should make them sufficiently refractory at 1000°C for its continuous use. The lower densities at higher temperatures enable their use as an insulating material. Therefore, they can be used as insulating material and for applications where fire safety is required. ACKNOWLEDGEMENT The financial support of the Deanship of Scientific Research, University of Jordan of the project “Chemical stabilization of natural geomaterials for construction and industrial applications” is highly appreciated. The support of the Flemish (Belgium) Vlaamse Interuniversitaire Raad (VLIR, Contract ZEIN2006PR333) within the “Own Initiatives” program is gratefully acknowledged. *Corresponding Author: khouryhn@ju.edu.jo

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404448525660 2- θ12162024283236

100 C°

200 C°

400 C°

600 C°

800 C°

1000 C°

KS

α-Q

Q

α-Q

SKQSK

Q

Q

Q

QQ

Q Q

KQQ P

M

K : Kaolinite

Q : Quartz

S :Sodalite

M : Mullite

P : Na-Al-Silicate

-

-Q-Q

-Q -Q

P

S

S

- Q

- Q

Fig. 5. The XRD traces of geopolymers heated up to 100°C, 200°C, 400°C, 600°C, 800°C, and 1000°C.

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Figure 6: SEM image the heated geopolymer at 100 °C with relicts of kaolinite flakes and Na-Al silicate phases as a matrix .

Figure 7: SEM image the heated geopolymer at 600 °C with beta-quartz and fractured texture.

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Figure 8: SEM image the heated geopolymer at 600 °C with collapsed porous texture.

Figure 9: SEM image of heated geopolymer at 800 °C, showing porous and fused glassy texture.

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Figure 10: SEM image of heated geopolymer at 1000 °C, showing porous laminated texture and sodalite crystals.

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REFERENCES [1] P.Duxson, A. Fernández-Jiménez, J.L Provis., G.C. Lukey, A. Palomo and J.S.J. van Deventer. Geopolymer technology: the current state of the art. Journal of Materials Science, 42, 2917-2933, (2007). [2] M. Rowles, B. O’Connor, Chemical optimisation of the compressive strength of aluminosilicate geopolymers synthesised by sodium silicate activation of metakaolinite, J. Mater. Chem. 13 1161–1165, (2003) [3] J. Davidovits, “ Geopolymers: Man-Made Rock Geosynthesis and the Resulting Development of very Early High Strength Cement,” Journal Materials Education, 16 [12] 91-139, (1994). [4] J. Davidovits,”Chemistry of Geopolymeric Systems, Terminology,” Geopolymere ’99, Geopolymer International Conference, Proceedings, 30 June – 2 July, 1999, pp. 9-39, Saint-Quentin, France. Edited by J. Davidovits, R. Davidovits and C. James, Institute Geopolymere, Saint Quentin, France, (1999). [5] J. Davidovits, Geopolymers and geopolymeric new material, J. Therm. Anal. 35, 429–441, (1998) [6] P. Duxson, G. C. Lukey, J. S. J. van Deventer, Physical evolution of Na-geopolymer derived from metakaolin up to 1000 °C. J Mater Sci 42:3044–3054 (2007). [7] H. Khoury, H. Al Houdali, Y. Mubarak, N. Al Faqir, B. Hanayneh, and M. Esaifan: Mineral Polymerization of Some Industrial Rocks and Minerals in Jordan. Published by the Deanship of Scientific Research, University of Jordan. (2008). [8] H. Khoury, M. AlShaaer (2009): Production of Building Products through Geopolymerization. GCREEDER. Proceedings Global Conference on Renewable and Energy Efficiency for Desert Regions. P 1-5, (2009) [9] R. I. Yousef, B. El-Eswed , M. Alshaaer, K. Fawwaz, H. Khoury, The influence of using Jordanian zeolitic tuff on the adsorption, physical, and mechanical properties of geopolymers products, J. Hazardous Materials, 165, Issues 1-3, 379-387, (2009) [10] D. Perera and R.Trautman, Geopolymers with the Potential for Use as Refractory Castables.“Advances in Technology of Materials and Materials Processing”, 7[2] 187-190 (2005). [11] H. Rahier, , B. Van Mele, and J. Wastiels, Low Temperature Synthesised Aluminosilicate Glasses. Part B: Rheological Transformations during Low-Temperature Cure and High- Temperature Properties of a Model Compound, J. Mater. Sc., 31, 80-85, (1996). [12] V. F. F. Barbosa and K. J. D. MacKenzie, “Synthesis and Thermal Behaviour of Potassium Sialate Geopolymers,” Materials Letters, 57 1477-82 (2003). [13] H. Khoury, Clays and Clay Minerals in Jordan, The University of Jordan, p.116, (2002). [14] ASTM D4318 D 4318, Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, vol. 04.08, American Society for Testing and Materials, (2003) [15] F. Slaty “Durability of Geopolymers Product from Jordanian Hiswa Clay” PhD dissertation (2010). [16] H. Rahier, F. Slaty, I. Al dabsheh, M. Al Shaaer, H. Khoury, M. Esaifan and J. Wastiels. Use of local raw materials for construction purposes (2010).

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