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Utilization of some industrial wastes for eco-friendly cement production
Accepted Manuscript Utilization of some industrial wastes for eco-friendly cement production
S.M.A. El-Gamal, F.A. Selim PII: DOI: Reference:
S2214-9937(17)30016-7 doi: 10.1016/j.susmat.2017.03.001 SUSMAT 38
To appear in:
Sustainable Materials and Technologies
Received date: Revised date: Accepted date:
2 February 2017 17 February 2017 3 March 2017
Please cite this article as: S.M.A. El-Gamal, F.A. Selim , Utilization of some industrial wastes for eco-friendly cement production. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Susmat(2017), doi: 10.1016/j.susmat.2017.03.001
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ACCEPTED MANUSCRIPT Title Page
Manuscript title:
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"Utilization of Some Industrial Wastes for Eco -Friendly Cement
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Production"
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Authors
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S. M. A. El-Gamal* , F. A. Selim
Email: [email protected]
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*Corresponding author
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Faculty of Science, Chemistry Department, Ain Shams University, Egypt.
ACCEPTED MANUSCRIPT Utilization of Some Industrial Wastes for Eco -Friendly Cement Production Abstract The development of new eco-friendly construction materials
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alternatives to Portland cement is of greatest importance to the industry
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and world climate, this will minimize the utility of fast deteriorating
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natural resources and also reduce the emission of green - house gases. In
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this investigation, Ground Granulated Blast Furnace Slag (GGBS) has been used to produce Geopolymer cement (GPC) at ambient temperature
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and at about 100% relative humidity, the influence of replacing slag by 5 and 10% of fly ash or clay- bricks wastes (Homra) as well as the effect
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of sodium silicate to sodium hydroxide ratio (SS: SH) in the alkaline activator solution on the properties of the produced Geopolymer have
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been investigated. This was done through measurement of compressive strength values, water absorption as well as performing FTIR spectra,
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XRD patterns and SEM imaging. From the experimental results, the optimum percentage replacement of GGBS with FA or Homra is 5%. Besides, the optimum SS: SH ratio is 1 by weight, while 0.5 ratio produces the lowest compressive strength and higher water absorption values.
ACCEPTED MANUSCRIPT Keywords Geopolymer; ground granulated blastfurnace slag; fly Ash; Homra ;compressive strength.
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1. Introduction
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Increasing the requirement of environment-friendly building
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materials has been the driving force for developing sustainable and
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economical building materials. The main factors affecting the development process are the performance of the materials under different
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and special user conditions, economic as well as environmental impact aspects. Production of Portland cement is an energy consuming and high
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greenhouse gas emitting product [1]. Actually, one ton of Portland cement generates one ton of CO2 [2]. It is estimated that with
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demographic growth and industrialization, the pollution generated by Portland cement manufacturing in a few years will represent 17% of
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worldwide CO2 emissions [3]. Evidently, geopolymers are gaining a great interest as binders with low CO2-emission in comparison to Portland cement. Geopolymers are a very promising kind of material since they have been shown to offer an environmentally friendly, technically competitive alternative to ordinary Portland cement (OPC) [4-6]. Geopolymer manufacturing produces five
ACCEPTED MANUSCRIPT times less CO2 than does the manufacture of Portland cement. Actually, using geopolymer concrete, which does not utilize any Portland cement in its production achieve a significant reduction in the energy consumption and the CO2 emission, so it has been proposed to be an alternative to
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Portland cement concrete (PCC).
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Production of geopolymer binder require about less 3/5 energy and
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about from 80-90 % less CO2 is generated than that of Portland cement [7,8]. Actually, geopolymers are kinds of inorganic polymers, it is a class
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of three-dimensionally networked alumino-silicate materials, similar to
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zeolite and first developed by Joseph Davidovits in 1978 [9,10]. Geopolymer systems are divided into two types of a binding system
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which are silica-aluminum with medium to a high alkaline solution and
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silica-calcium with a mild alkaline solution [11]. For the silica-aluminum binding system, the materials included in this system are class F fly ash
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and metakaolin due to having silica and alumina content as the main
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composition. Meanwhile, for silica- calcium system, ground granulated blast furnace slag was included in this system due to its main composition which is silica and calcium. The hydration products of these two systems are also different where calcium silicate hydrate (CSH) is the main product for the (Si + Ca) system, and zeolite-like polymers are the main products for the (Si + Al) system. Actually, geopolymer binders exhibit similar or superior engineering properties compared to Portland cement.
ACCEPTED MANUSCRIPT Such as fast setting and hardening, early compressive strength, fire resistance, durability, excellent bond strength and good ability to immobilize toxic metals, and better acid resistance [12-16]. Geopolymer is synthesized by alkali activation of materials
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containing mostly amorphous silica (SiO2) and alumina (Al2O3).
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Naturally occurring materials like, kaolin [17,18], natural pozzolana [19,
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20], Malaysian marine clay [21], treated minerals like metakaolin and waste materials like fly ash [22-30], construction waste, red clay brick
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waste (Homra) [31,32], rice husk-ash and blast furnace slag [33,34].
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In general, the polymerization process involves a fast chemical reaction of aluminosilicate minerals under an alkaline condition that
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results in a three-dimensional polymeric chain. It includes three main
Condensation
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steps: 1. dissolution of Si and Al atoms from the source material, 2. of
precursor
ions
forming
monomers,
and
3.
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Polycondensation of the formed monomers into polymeric structures
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[35]. The produced geopolymers are influenced by many factors such as chemical composition of the used materials as well as the composition of the alkaline activators [36]. For the alkaline activator solution, many studies revealed that the combination of sodium hydroxide and sodium silicate solution leads to higher geopolymerisation rates compared to sodium hydroxide alone [37,38]. Moreover, many investigations reported that additional silica (Si)
ACCEPTED MANUSCRIPT is essentially required for the geopolymerisation process when different source materials of the alumina-silicate mineral are used to produce geopolymer [39]. In general, alkali hydroxide is required for the dissolution process of aluminosilicate sources, while Na2SiO3 solution
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acts as a binder [40]. The geopolymer preparation mainly depends on two
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factors namely as (1) solids/liquid (S/L) and (2) Na2SiO3/NaOH ratio
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which is important in developing the geopolymer strength [41]. Blast furnace slag is obtained as byproducts formed in processes
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such as pig iron manufacturing from iron ore, combustion residue of
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coke, and fluxes such as serpentine or limestone. If the molten slag is rapidly-cooled using high-pressure water jets, a vitreous Ca–Al–Mg
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silicate fine grain glass is formed. Water cooled slag (granulated blast
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furnace slag) is a glassy, granular material consisting of SiO2, CaO, Al2O3, and MgO. Generally, granulated blast furnace slag is used as
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partially replacing to Portland cement. Granulated blast furnace slag is a
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non-toxic material, and can be used as a raw material for making geopolymers with good mechanical properties as well as in fire resistant applications [42]. In this study ground granulated blast furnace slag, coal fly ash and clay -bricks (Homra) wastes were used as industrial raw materials to produce geopolymeric green cement using sodium silicate(SS) -sodium
ACCEPTED MANUSCRIPT hydroxide(SH) alkaline activator with different SS:SH mass ratio at ambient temperature and 100% relative humidity conditions, 2. Experimental
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2.1 Materials Raw materials used in this investigation are Ground Granulated
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Blast Furnace Slag (GGBS) which is a by-product of iron production,
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Crushed clay bricks (Homra) of Blaine surface area of 5000 cm2/g and
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class F fly ash (FA) of Blaine surface area ≈ 3,800 cm2/g and average diameter ≤ 10 μm. Fly ash is one of the deposits produced from the
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Homra are given in Table (1).
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burning of coal. The chemical oxide compositions for GGBS, Fly ash and
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Alkaline Activated Solution (AAS) used here is a mixture of sodium silicate (Na2SiO3 9H2O., 8M) and sodium hydroxide (NaOH, 10M).
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Distilled water is used to prepare the alkaline activator solution. The
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required mass ratio of sodium silicate and sodium hydroxide solutions are mixed prior to adding to the dry raw materials. Polycarboxylate based superplasticizer is used to maintain the workability of the formed GPC paste without adding extra water. 2.2. Sample preparation
ACCEPTED MANUSCRIPT The dry Mixes with the required composition (as mentioned in Table 2) were prepared by mixing the solid raw materials in ball mill for 8 hours to ensure the complete homogeneity of the dry mixtures. Geopolymer cement pastes (GPC) were prepared by mixing the dry
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sample with the calculated amount of alkaline activator (10% NaOH and
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8% Na2SiO3). The mass ratio of solid raw materials to alkaline activator
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solution used (S: A) is 2:1, while, the ratios of Na2SiO3 (SS) to NaOH
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(SH) to form alkali activator are 0.5, 1.0 and 1.5 (by mass). The addition of small amount of polycarboxylate superplasticizer is required for
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preparation of some pastes prepared using 1.5 SS: SH ratio for
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maintaining a good workability with no extra water addition.
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The resulted pastes were molded into cubic specimens by using cubic moulds having one-inch dimension. The moulds were compacted via
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vibration; the leveling and smoothness of the top surface of the pastes were done by a thin edged towel. After casting, the moulds were cured at
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60 °C in the oven for 24 hours. Then the specimens were removed from their moulds and cured at ambient temperature and about 100 % relative humidity for 3,7 and 28 days. 2.3. Testing and characterization Three cubic specimens were used for the determination of the compressive strength after each curing period, the average of the three
ACCEPTED MANUSCRIPT results was considered. These specimens represented a certain composition and cured for a prescribed period. The compressive strength test was performed using a Ton industry machine (West Germany). Stopping the geopolymerisation process at each curing time was done by
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removing the free water, this was accomplished by drying the crushed
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specimens for 24 hours at 105 °C [43]. The setting times (Initial and
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Final) for each freshly prepared pastes were determined using Vicat
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needle [44].
Water absorption measurements of the hardened geopolymer
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specimens were carried out according to ASTM C140 [45]. The percentage of absorption was calculated using the following equation:
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Absorption (%) = [(W2 – W1)/ W1] ×100 Where: W1 = weight of specimen after complete drying at 105 °C;
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W2 = final weight of the surface dry sample after immersion in water for
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at least 24 hours.
X-ray diffraction technique was carried out on some selected hydrated and dried geopolymer specimens after 28 days of curing to investigate the crystallinity structure and mineralogy of these mixes. The Spectroscopic analysis was performed on some selected hardened geopolymer specimens after 28 days to evaluate the functional groups in
ACCEPTED MANUSCRIPT the hardened GPC sample using Fourier Transformation Infra-Red (FTIR). The band spectral was recorded in the range of 4000-400 cm-1. Scanning electron microscope, (SEM), has been used to study the morphology and microstructure of some selected GPC hardened
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specimens after 28 days of curing.
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3. Results and Discussion 3.1 Compressive strength
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The compressive strength values for 100% GGBS based
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geopolymer cement (GPC) hardened specimens, prepared using solid/activator (S:A) ratio of 2:1 and sodium silicate/sodium hydroxide
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(SS: SH) ratios of 0.5,1 and 1.5 (Mixes A1-A3) after 3,7 and 28 days of
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curing at ambient room temperature, and ~ 100 relative humidity are shown in Fig.1. The compressive strength values indicated a continuous
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increase with increasing the age of curing for all tested specimens (Mixes
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A1-A3). In addition, as the SS: SH ratio increase the compressive strength values increase. The increase in the compressive strength values indicating the formation of geopolymer with good mechanical properties via the alkali activation of GGBS. This results can be explained in terms of the higher reactivity of GGBS, which in the presence of the alkaline activator (OH−), promote the rupture of bonds in its structure (Ca-O; Si-O and Al-O) that
ACCEPTED MANUSCRIPT forms dissolved species (Ca2+; [H2SiO4]2−, [H3SiO4]−and [Al(OH)4]−), which can precipitate when reaches to supersaturation forming CSH and C-A-S-H hydrate [34]. Besides, the calcium ions present in GGBS enter in the Si-O-Al gel structure, which compensates the charge of the
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aluminum atoms (Al3+) and allows space for the C-A-S-H system in
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addition to the N-A-S-H gel. This leads to the formation of a more-
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denser structure [35-37]
Obviously, the GPC specimens prepared using the highest contents
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of sodium hydroxide (SS: SH mass ratio of 0.5), showed the lowest
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compressive strength development among the other SS: SH ratios at all tested ages and thus indicated the lowest geopolymerization reaction.
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Evidently, under lower alkalinity conditions (high SS: SH ratio), the
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dissolution of calcium ions (Ca2+) from GBFS is promoted and consequently the formation of C-S-H gels is pronounced, leading to
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stable gel coexistence, but higher alkalinity (low SS: SH ratio) tends to
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lead to Ca(OH)2 precipitation. Obviously, for GPC specimens prepared using alkaline activator (SS: SH) mass ratio of 1.0 -1.5 the geopolymer indicated a relatively high strength development during all curing periods. The high strength development in the GPC specimens prepared using SS: SH mass ratios of 1.0 and 1.5 reveals the complexity of the geopolymerization process and indicates the effect of the concentration of the alkaline activator
ACCEPTED MANUSCRIPT constituents. Evidently, the presence of dissolved silicon in the aqueous solution of sodium silicate contributes to the increase of compressive strength. The higher concentration of dissolved silicon in the matrix produces higher compressive strength values, but only for certain limit,
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further increase in silicon ions concentration causes a notable decrease in
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the compressive strength values [22]. Researchers have suggested that the
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optimum SS: SH ratio to produce geopolymer having high strength is in the range 0.67–1.00 [37]. In general, the use of sodium silicate helps to
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improve and increase the rate of the geopolymerisation process by
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accelerating the dissolution of the source material. These results are in agreement with previously obtained results [5,12].
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Finally, the slight decrease in the compressive strength values
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observed with increasing SS: SH ratio from 1 to 1.5 in the alkaline solution, is mainly attributed to increasing the amount of unreacted
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material, which increases with silicon concentration and has a deleterious
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effect on the mechanical strength of geopolymers [38,39]. Moreover, it could be attributed to increasing the viscosity of the reaction matrix with increase SS: SH ratio and thus hindered the mass transport through the solution which leads to a low strength of geopolymer paste. On conclusion, the obtained results revealed that the compressive strength of the formed geopolymers increases with increasing SS: SH ratio, due to the promotion of polymerization reaction [40]
ACCEPTED MANUSCRIPT The GPC specimens prepared from 95% GGBS + 5% FA and 90% GGBS +10 FA by using 2 :1 (S: A) and SS: SH ratios of 0.5,1 and 1.5 (Mixes B1-B3 and C1-C3), respectively, after different curing periods at ambient room temperature at ~ 100 relative humidity are shown in Figs.
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(2) and (3). The compressive strength values of these GPC specimens
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showed a continuous increase with increasing curing age. Also, as the SS:
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SH ratio increases from 0.5 to 1 causes increase the compressive strength values, but a slight decrease in the compressive strength values was
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discussed in the previous section.
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observed by increase SS: SH to 1.5, the reasons for these results were
Comparing the results of Fig (1), (2) and (3), a slight increase in the
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compressive strength values was observed in the case of replacing GGBS
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by 5% FA only in case of SS: SH is 1 after all curing ages. While in the case of SS: SH 0.5 or 1.5 these mixes showed a slight decrease in the
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compressive strength values at all curing periods. While replacing GGBS
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with 10%FA causes the compressive strength values to decrease during all tested periods at different SS: SH ratios (when compared with Mixes A or B). These results can be explained in terms of the increase in the amount of unreacted silicon by the presence of excess amount of FA, which has a deleterious effect on the mechanical strength of geopolymers [38].
ACCEPTED MANUSCRIPT Figures (4) and (5) show the compressive strength values of GPC specimens prepared from 95% GGBS+5% Homra and 90 %GGBS +10 % Homra by using S: A ratio 2:1 and SS: SH ratios 0.5,1 and 1.5 (Mixes D1-D3 and E1-E3), respectively, after different curing periods at ambient
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room temperature at ~ 100 relative humidity. The figures indicated a
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continuous increase in the compressive strength values with increasing
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the curing age for all mixes. Besides, the variation of compressive strength value with SS: SH ratios for these Mixes is the same as in the
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case of other prepared GPC specimens (Mixes A, B, and C). Obviously,
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replacing GGBS by 5 or 10% Homra gives higher and or/comparable compressive strength values as compared with geopolymer made from
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100% GGBS during all ages of hydration at different SS: SH ratios.
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Besides, increasing the amount of GGBS replaced by Homra from 5% to 10% the compressive strength values showed a slight decrease (but still
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higher than GPC made from 100 GGBS), which is attributed to the same
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reason mentioned previously in the case of fly ash substitution. 3.2. Absorption studies This test was done to investigate the relative porosity or permeability characteristics of the hardened GPC pastes. The values of water absorption for different mixes investigated after 28 days of curing at ambient temperature are given in Fig. (6). It is clear that for all tested GPC specimens the water absorption decreases with increasing the SS:
ACCEPTED MANUSCRIPT SH ratio from 0.5 to 1, then a slight increase with a further increase of this ratio to 1.5 was observed. Obviously, these results are in agree with the obtained compressive strength results. Obviously, GPC specimens prepared from different mixes using SS/SH ratio 1 showed the lowest
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water absorption values, these results are in agree with the obtained
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compressive strength results, which indicated higher compressive
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strength values for these mixes, indicating a low degree of porosity.
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3.3. Setting Time
The results of the initial and final setting times for all tested GPC
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specimens are shown in Figs. (7) and (8), respectively. The initial setting
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times ranges from 4 to 88 minutes while the final setting time ranged from 9 to 385 minutes. Evidently, the results revealed that the initial and
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final setting times are largely affected by two main factors namely (i)
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Sodium silicate: sodium hydroxide ratio and (ii) The % replacement of GGBS by FA or Homra. Obviously, the results showed a notable decrease in both initial and final setting times values with increasing the SS: SH ratio for all tested fresh pastes. Besides, the gap between the initial and final setting increase. Obviously, GPC specimens made with least amount of sodium silicate (SS/SH ratio of 0.5) have the longest initial and final setting times compared to those made with 1 and 1.5
ACCEPTED MANUSCRIPT SS/SH ratios. This result is attributed to the reduction in the amount of Si present in the mix, which results in slow down the polymerization process [41]. Increasing the ratio SS: SH in the alkaline activator solution decreased
setting
time
which
reveals
increasing
the
rate
of
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geopolymerisation [40], Figs. (7) and (8). These results illustrate the
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influence of chemical compositions of alkaline activator on the rate of
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setting. Evidently, upon increasing the SS: SH ratio from 0.5 to 1.5, the amount of soluble silica increase, the polymerization process is
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accelerated so, the initial and final setting times decreased. Replacing
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GGBS with different amount of FA or Homra (5 or 10% by mass of slag) causes a notable increase in both the initial and final setting times,
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indicating retardation of the rate of polymerization process by the
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presence of these waste materials. 3.4. XRD analysis
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The XRD patterns of GPC specimens made from Mixes A1, B1,
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C1, D1 and E1 after 28 days' hydration are shown in Fig.9. The diffraction patterns of all tested mixes have a large diffused hump in the region of 27-33o centered at about 29.5o, this hump is characterizing for the glassy phase of the formed geopolymer, mainly as CSH gel [42,46]. The intensity and the degree of broadening of this hump are increased with increasing the amorphous constituents (CSH content) of the formed geopolymer [47]. Replacement of GGBS with 5 and 10 % of FA or
ACCEPTED MANUSCRIPT Homra indicated the same diffraction patterns as that of Mix A1 (100% GGBS) but with the appearance of a new peaks in the XRD patterns which characteristic for quartz and calcite, the appearance of calcite in these patterns is due to the carbonation of the geopolymer specimens, Fig
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(9).
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The GPC specimens prepared using SS: SH ratio 1 (Mixes A2, B2,
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C2, D2, and E2) indicated the same diffraction patterns as their corresponding ones prepared using SS: SH- 0.5, Fig. (10). Obviously,
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from Fig (10) we can note an increase in the intensity and broadening of
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the diffused hump obtained at 29.5o (characteristic for amorphous CSH) in the XRD pattern of these GPC specimens, which confirm the increase
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in the amount of amorphous CSH formed with increasing the SS:SH ratio
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from 0.5 to 1, these results agree with the results of compressive strength development obtained.
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3.5. Fourier Transform Infrared Spectroscopy (FTIR) Analysis
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Figures (11) and (12) display the IR spectra of geopolymer samples prepared using 0.5 and 1 SS/SH ratios, respectively, after 28 days of curing at ambient temperature and 100% relative humidity. Evidently, at both SS: SH ratios all the tested GPC specimens showed broad bands appearing around 3425 and 2380 cm−1, due to stretching vibrations OH and HOH. In addition, the bending vibration of HOH was detected at about 1650 cm−1. these absorption bands are characteristics to crystalline
ACCEPTED MANUSCRIPT H2O of the hydrated products such as C–S–H and calcium aluminosilicate (C–A–S-H), as well as the presence of entrapped water molecules in the geopolymeric network [28,48]. stretching vibration of O-C-O was detected for all tested GPC specimens at 1460 cm−1 which is attributed to
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the carbonation reaction. The carbonation process occurred as a result of
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the presence of excessive amount of Na (present from NaOH in activator
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solution) where it reacted with CO2 from the atmosphere [49]. The band attributed to asymmetric stretching vibration of Si-O-Si and Al-O-Si at
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about 970 cm−1 indicated the formation of aluminosilicate gel. Besides
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that, symmetric stretching vibrations Si-O-Si were located at 670–720 cm−1.Also, the bending vibrations of Si-O-Si and O-Si-O were found at
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450 cm−1 [49,50].
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From Figs. (11) and (12) the FTIR patterns showed a notable increase in the intensity of C-A-S-H and CSH gel with increasing the
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SS:SH ratio from 0.5 to 1 and with substituting GGBS with 5% of FA or
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Homra, indicating increase the amount of geopolymer formed, these results confirmed the obtained compressive strength values for these mixes. Besides, an increase in intensity of broad bands appeared in the IR -1
spectra of these mixes, in the region of 3425 and 1650 cm was observed which assigned to stretching (-OH) and bending (H-O-H) vibrations of bound water molecules, which are surface absorbed or entrapped in the
ACCEPTED MANUSCRIPT large voids of the polymeric network [51]. This implies that the Geopolymers ability to adsorb water in their three-dimensional framework increases with the substitution of slag with FA or Homra. 3.6. Morphology and Microstructure
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The microstructure of the hardened geopolymer specimens
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prepared using 0.5 - SS: SH ratio (Mixes A1, B1, D1) after 28 days of
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curing at ambient temperature are shown in Figs. (13-15). In generally, the SEM micrographs of all these specimens indicate the formation of with
mostly
amorphous
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geopolymer
phases.
Obviously,
the
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microstructure of GPC specimens made from 100 GGBS had a dense – gel-like solid matrix with a uniform structure of hydration products
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mainly as calcium alumino-silicate hydrate (C–A–S–H) imbedded with
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micro-fibrous crystals of CSH and nearly absence of pores [46]. In addition, the unreacted slag particles also appear on the surface of the
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dense geopolymer matrix, Fig. (13-a, b). Evidently, the pastes having 5%
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FA or Homra (Mixes B1 and D1) are more compact and less porous than that having 100% GGBS (Mix A1), Figs. (14-a, b) and (15- a,b), respectively. The SEM micrographs of the GPC specimens prepared using SS: SH ratio 1 (Mixes A2, B2, and D2) indicated a more compact and dense micro structure as a result of increase the amounts of formed aluminosilicate geopolymeric materials which dispersed with micro -
ACCEPTED MANUSCRIPT fibrous of CSH. Consequently, this will enhance the binding characteristics of Geopolymer specimens, Figs. (16-18). These results revealed that the ratio of alkaline activator (SS: SH ratio) affect the saturation rate of the geopolymeraisation process as well as the
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compressive strength of the formed geopolymer [28]. Obviously, these
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results confirmed the obtained results of compressive strength mentioned
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previously. Finally, the partially reacted and un-reacted fly ash, Homra and slag particles are more commonly visible in the paste made with SS:
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SH ratio 0.5 more than that made with 1.
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Conclusions
The major findings of this work are summarized as follows:
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1. Partial replacement of slag by 5 and 10 % Homra effectively increase
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the compressive strength, enhanced microstructural properties and formed compact geopolymeric structures, as it increased the rate of
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Geopolymerization reaction.
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2. Replacing GGBS with 5%FA improves the mechanical properties and microstructure of the produced GPC only when using SS: SH ratio 1, while replacing it with 10%FA causes a slight decrease in the compressive strength values as compared with 100% GGBS based geopolymer.
ACCEPTED MANUSCRIPT 3. The SS: SH ratio plays an important role in the mix design of the geopolymer paste, the optimum ratio for SS: SH is 1 while the ratio 0.5 give the least compressive strength values. 4. Both the initial and final setting times increase with decreasing the
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SS:SH.
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5. Water absorption of the formed geopolymers decreased with increasing
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SS: SH ratio from 0.5 to 1 then showed a slight increase with a further increase to 1.5.
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This research did not receive any specific grant from funding agencies in
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CE
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the public, commercial, or not-for-profit sectors.
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[2] S.E. Wallah, B.V. Rangan, Low-calcium fly ash-based geopolymer
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process IPCBEE, 10 (2011) 18-24. [13] C.Y. Heah, H. Kamarudin, A.M. Mustafa Al Bakri, M. Binhussain, M. Luqman, I. Khairul Nizar, C.M. Ruzaidi , Y.M. Liew, Effect of curing profile on Kaolin-based geopolymers, Physics Procedia 22 (2011) 305311.
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geopolymer binders based on natural pozzolan, Cement and Concrete
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Composite 34(1) (2012) 25-33.
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[16] S.M. Tamizi, A.M. Mustafa Al Bakri, H. Kamarudin, C.M. Ruzaidi, J. Liyana, A.K. Aeslina, Feasibility study on composition and mechanical
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Materials 594-595 (2014) 401-405.
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properties of marine clay based geopolymer brick, Key Engineering
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Nizar, A.R. Rafiza, Y. Zarina, The Processing, characterization and
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properties of fly ash based geopolymer concrete, Rev. Advances Materials Scince 30 (2012) 90-97.
industry,
the
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building
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[18] A.M. Mustafa Al Bakri, M. Binhussain, Geopolymer materials for
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for geopolymer binders, International Journal of Civil Engineerng 7
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[22] L. Reig, M.M. Tashima, M.V. Borrachero, J. Monzo, C.R. Cheeseman, J. Paya, Properties and microstructure of alkali-activated red
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clay brick waste, Construction and Building Materials 43 (2013) 98-106.
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[23] T. Klabprasit, C. Jaturapitakkul, W. Chalee, P. Chindaprasirt, S. Songpiriyakij, Influence of Si/Al ratio on compressive strength of rice
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husk–bark ashes and fly ash-based geopolymer paste, The 3rd ACF
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International Conference- ACF/VCA (2008) 151-157. [24] F. Puertas, S. Martinez-Ramirez, S. Alonso, T. Vazquez, Alkali-
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activated fly ash/slag cement strength behaviour and hydration products,
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Cement and Concrete Research 30 (2000) 1625-1632. [25] P. Duxson, A. Fernandez-Jimenez, J.L. Provis, G.C. Lukey, A. Palomo, J.S.J. van Deventer, Geopolymer technology: the current state of the art, Journal of Materials Science 42(9) (2007) 2917-2933. [26] E.I. Diaz, E.N. Allouche, S. Eklund, Factors affecting the suitability of fly ash as source material for geopolymers, Fuel 89 (2010) 992-996.
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AbdRazak, A.V. Sandu, Effect of solids-to-liquids, Na2SiO3-to-NaOH
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and curing temperature on the palm oil boiler ash (Si + Ca)
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geopolymerisation system, Materials 8 (2015) 2227-2242. [29] H. Xu, J.S.J. van Deventer, The geopolymerisation of alumino-
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silicate minerals, International Journal of Mineral Process 59 (2000) 247-
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266.
[30] K. Komnitsas, D. Zaharaki, Geopolymerisation: A review and
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prospect for the mineral industry, Mineral Engineering 20 (2007) 1261-
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1277.
[31] J.G.S. Van jaarsveld, J.S.J. van Deventer, G.C. Lukey, The effect of
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composition and temperature on the properties of fly ash and kaolinite-
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based geopolymers, Chemical Engineering Journal 89 ( 2002) 63-73. [32] F. Skvara, T. Jilek, L. Kopecky, Geopolymer materials based on fly ash, Ceramics-Silikaty 49(3) (2005) 195-204. [33] E. Rodriguez, S. Bernal, R. Mejia de Gutierrez, F. Puertas, Hormigon alternative basad oenescorias activadasal calinamente. Materiales de Construccion 58(291) (2008) 53-57.
ACCEPTED MANUSCRIPT [34] R.A. Robayo, R. Mejia de Gutierrez, M. Gordillo, Natural pozzolanand granulated blast furnace slag-based binary geopolymers, Materiales de Construccion 66 (321) (2016). [35] H.K. Tchakoute, A. Elimbi, E. Yanne, C.N. Djangang, Utilization of
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volcanic ashes for the production of Geopolymers cured at ambient
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temperature, Cement and Concrete Composite. 38 (2013) 75-81.
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[36] Z. Zhang, H. Wang, Y. Zhu, A. Reid, J. Provis, F. Bullen, Using fly ash to partially substitute metakaolin in geopolymer synthesis, Applied
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Clay Science 88-89 (2014) 194-201.
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[37] P. Chindaprasirt, T. Chareerat, V. Sirivivatnanon, Workability and strength of coarse high calcium fly ash geopolymer, Cement and
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Concrete Composite 29 (2007) 224-229.
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[38] P. Duxon, J.L. Provis, G.C. Lukey, S.W. Mallicoat, W.M. Kriven, J.S.J. van Deventer, Colloids surfaces, A 269 (2005) 47-58.
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[39] Mechanical and microstructural characterization of geopolymer
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synthesized from low calcium fly ash, Chemical Indian Chemistry Engineering Q. 21(1) (2015) 13-22.
ACCEPTED MANUSCRIPT [40] A.M. Mustafa Al Bakri, H. Kamarudin, M. Binhussain, A.R. Rafiza, Y. Zarina, Effect of Na2SiO3/NaOH Ratios and NaOH Molarities on Compressive Strength of Fly-Ash-Based Geopolymer,Materials Journal 109 (2012) 503-508.
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[41] P. Nath , P K Sarker, Effect of GGBFS on setting, workability and
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early strength properties of fly ash geopolymer concrete cured in ambient
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condition, Construction and Building Materials 66 (2014) 163-171. [42]W. Shao-Dong, S. Karen, Hydration products of alkali activated slag
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cement, Cement and Concrete Research 25 (1995) 561-571.
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[43] H.M. Khater, Effect of cement Kiln dust on geopolymer composition and its resistance to sulfate attack, Green materials Journal,
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1(1) (2013) 36-46.
[44] ASTM C191, Standard test methods for time of setting of hydraulic
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cement by vicat needle, (2013). [45] ASTM C140, Standard test methods for sampling and testing
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concrete masonry units and related units, (2012). [46] M. Ben Haha, G. Le Saout, F. Winnefeld, B. Lothenbach, Influence of activator type on hydration kinetics, hydrate assemblage and microstructural development of alkali activated blast-furnace slags, Cement and Concrete Research 41(3) (2011) 301-310.
ACCEPTED MANUSCRIPT [47] H.M. Khater, H.A. Abd el Gawaad, Characterization of alkali activated geopolymer mortar doped with MWCNT, Advances in Materials Research 4(1) (2015) 45-61. [48] H.A. Abdel-Gawwad , S.A. Abo-El-Enein, A novel method to
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produce dry geopolymer cement powder, HBRC Journal 12 (2016) 13-24.
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[49] H. M. Khater, Abdeen M. El Nagar, M. Ezzat, Optimization of alkali
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activated grog/ceramic wastes geopolymer bricks, International Journal of Innovative Research in Science, Engineering and Technology 5(1)
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(2016).
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[50] S.K. Nath, S. Kumar, Influence of iron making slags on strength and microstructure of fly ash geopolymer, Construction and Building
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Materials 38 (2013) 924-930.
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[51] A. Fernandez-Jimenez, A. Palomo, Composition and microstructure of alkali activated fly ash binder: Effect of the activator, Cement and
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Concrete Research 35 (2005) 1984-1992.
7 days
28 days
40
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26.2
25.9
23.2
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31.7
29.9
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3 days
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A1
A2
A3
Geopolymer mixes
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Fig.1 Compressive strength values of GPC specimens made from Mixes (A1-A3) after different ages of curing.
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Fig.2 Compressive strength values of GPC specimens made from Mixes (B1-B3) after different ages of curing.
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Fig.3 Compressive strength values of GPC specimens made from Mixes (C1-C3) after different ages of curing.
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Fig.4 Compressive strength values of GPC specimens made from Mixes (D1-D3) after different ages of curing.
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Fig.5 Compressive strength values of GPC specimens made from Mixes (E1-E3) after different ages of curing.
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Fig.6 Water absorption values of different GPC Mixes after 28 days of curing.
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Fig.7 Initial setting times values for different GPC Mixes
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Fig.8 Final setting times values for different GPC Mixes
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Fig.9.XRD patterns of some selected geopolymers specimens after 28 days of hydration.
[CSH : calcium silicate hydrate, Q : Quartz ,CC :calcium carbonate]
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Fig.10 XRD patterns of some selected geopolymers specimens after 28 days of hydration. [CSH : calcium silicate hydrate, Q : Quartz ,CC :calcium carbonate]
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Fig.11 FTIR spectra of geopolymer specimens after 28 days of hydration
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Fig.12 FTIR spectra of geopolymer specimens after 28 days of hydration
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Fig. 13 SEM of geopolymer made from Mix A1 after 28-days
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Fig.14 SEM image of geopolymer made from Mix A2 after 28 days.
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Fig. 15 SEM image of geopolymer made from Mix B1 after 28 days.
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Fig.16 SEM image of geopolymer made from Mix B2 after 28 days.
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Fig.17 SEM image of geopolymer made from Mix D1 after 28 days.
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Fig. 18 SEM image of geopolymer made from Mix D2 after 28 days.
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Fe2O3
CaO
MgO
GGBS
41.78
10.55
3.52
32.18
6.63
1.16
Fly ash
76.65
33.01
4.89
1.81
Homra
64.87
15.61
8.27
3.00
1.48
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Na2O
LOI
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Al2O3
Material
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SiO2
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Oxides (mass%)
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Table 1. Chemical oxide composition of raw materials.
SO3 K2O 0.85
0.27
-0.73
0.87
0.01
1.05
0.17
0.95
0.92
1.12
1.30
1.74
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Table 2. The percentage composition of the different geopolymer mixes and their designations.
Fly ash
Homra
A1
100
-
-
A2
100
-
-
A3
100
-
B1
95
5
B2
95
5
B3
95
C1
90
Na2SiO3/NaOH
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GGBS
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Mixes
0.5 1.0 1.5
-
0.5
-
1.0
5
-
1.5
10
-
0.5
90
10
-
1.0
90
10
-
1.5
95
-
5
0.5
D2
95
-
5
1.0
D3
95
-
5
1.5
E1
90
-
10
0.5
E2
90
-
10
1.0
E3
90
-
10
1.5
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S.M.A. El-Gamal, F.A. Selim PII: DOI: Reference:
S2214-9937(17)30016-7 doi: 10.1016/j.susmat.2017.03.001 SUSMAT 38
To appear in:
Sustainable Materials and Technologies
Received date: Revised date: Accepted date:
2 February 2017 17 February 2017 3 March 2017
Please cite this article as: S.M.A. El-Gamal, F.A. Selim , Utilization of some industrial wastes for eco-friendly cement production. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Susmat(2017), doi: 10.1016/j.susmat.2017.03.001
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ACCEPTED MANUSCRIPT Title Page
Manuscript title:
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"Utilization of Some Industrial Wastes for Eco -Friendly Cement
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Production"
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Authors
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S. M. A. El-Gamal* , F. A. Selim
Email: [email protected]
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*Corresponding author
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Faculty of Science, Chemistry Department, Ain Shams University, Egypt.
ACCEPTED MANUSCRIPT Utilization of Some Industrial Wastes for Eco -Friendly Cement Production Abstract The development of new eco-friendly construction materials
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alternatives to Portland cement is of greatest importance to the industry
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and world climate, this will minimize the utility of fast deteriorating
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natural resources and also reduce the emission of green - house gases. In
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this investigation, Ground Granulated Blast Furnace Slag (GGBS) has been used to produce Geopolymer cement (GPC) at ambient temperature
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and at about 100% relative humidity, the influence of replacing slag by 5 and 10% of fly ash or clay- bricks wastes (Homra) as well as the effect
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of sodium silicate to sodium hydroxide ratio (SS: SH) in the alkaline activator solution on the properties of the produced Geopolymer have
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been investigated. This was done through measurement of compressive strength values, water absorption as well as performing FTIR spectra,
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XRD patterns and SEM imaging. From the experimental results, the optimum percentage replacement of GGBS with FA or Homra is 5%. Besides, the optimum SS: SH ratio is 1 by weight, while 0.5 ratio produces the lowest compressive strength and higher water absorption values.
ACCEPTED MANUSCRIPT Keywords Geopolymer; ground granulated blastfurnace slag; fly Ash; Homra ;compressive strength.
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1. Introduction
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Increasing the requirement of environment-friendly building
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materials has been the driving force for developing sustainable and
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economical building materials. The main factors affecting the development process are the performance of the materials under different
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and special user conditions, economic as well as environmental impact aspects. Production of Portland cement is an energy consuming and high
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greenhouse gas emitting product [1]. Actually, one ton of Portland cement generates one ton of CO2 [2]. It is estimated that with
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demographic growth and industrialization, the pollution generated by Portland cement manufacturing in a few years will represent 17% of
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worldwide CO2 emissions [3]. Evidently, geopolymers are gaining a great interest as binders with low CO2-emission in comparison to Portland cement. Geopolymers are a very promising kind of material since they have been shown to offer an environmentally friendly, technically competitive alternative to ordinary Portland cement (OPC) [4-6]. Geopolymer manufacturing produces five
ACCEPTED MANUSCRIPT times less CO2 than does the manufacture of Portland cement. Actually, using geopolymer concrete, which does not utilize any Portland cement in its production achieve a significant reduction in the energy consumption and the CO2 emission, so it has been proposed to be an alternative to
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Portland cement concrete (PCC).
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Production of geopolymer binder require about less 3/5 energy and
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about from 80-90 % less CO2 is generated than that of Portland cement [7,8]. Actually, geopolymers are kinds of inorganic polymers, it is a class
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of three-dimensionally networked alumino-silicate materials, similar to
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zeolite and first developed by Joseph Davidovits in 1978 [9,10]. Geopolymer systems are divided into two types of a binding system
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which are silica-aluminum with medium to a high alkaline solution and
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silica-calcium with a mild alkaline solution [11]. For the silica-aluminum binding system, the materials included in this system are class F fly ash
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and metakaolin due to having silica and alumina content as the main
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composition. Meanwhile, for silica- calcium system, ground granulated blast furnace slag was included in this system due to its main composition which is silica and calcium. The hydration products of these two systems are also different where calcium silicate hydrate (CSH) is the main product for the (Si + Ca) system, and zeolite-like polymers are the main products for the (Si + Al) system. Actually, geopolymer binders exhibit similar or superior engineering properties compared to Portland cement.
ACCEPTED MANUSCRIPT Such as fast setting and hardening, early compressive strength, fire resistance, durability, excellent bond strength and good ability to immobilize toxic metals, and better acid resistance [12-16]. Geopolymer is synthesized by alkali activation of materials
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containing mostly amorphous silica (SiO2) and alumina (Al2O3).
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Naturally occurring materials like, kaolin [17,18], natural pozzolana [19,
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20], Malaysian marine clay [21], treated minerals like metakaolin and waste materials like fly ash [22-30], construction waste, red clay brick
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waste (Homra) [31,32], rice husk-ash and blast furnace slag [33,34].
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In general, the polymerization process involves a fast chemical reaction of aluminosilicate minerals under an alkaline condition that
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results in a three-dimensional polymeric chain. It includes three main
Condensation
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steps: 1. dissolution of Si and Al atoms from the source material, 2. of
precursor
ions
forming
monomers,
and
3.
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Polycondensation of the formed monomers into polymeric structures
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[35]. The produced geopolymers are influenced by many factors such as chemical composition of the used materials as well as the composition of the alkaline activators [36]. For the alkaline activator solution, many studies revealed that the combination of sodium hydroxide and sodium silicate solution leads to higher geopolymerisation rates compared to sodium hydroxide alone [37,38]. Moreover, many investigations reported that additional silica (Si)
ACCEPTED MANUSCRIPT is essentially required for the geopolymerisation process when different source materials of the alumina-silicate mineral are used to produce geopolymer [39]. In general, alkali hydroxide is required for the dissolution process of aluminosilicate sources, while Na2SiO3 solution
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acts as a binder [40]. The geopolymer preparation mainly depends on two
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factors namely as (1) solids/liquid (S/L) and (2) Na2SiO3/NaOH ratio
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which is important in developing the geopolymer strength [41]. Blast furnace slag is obtained as byproducts formed in processes
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such as pig iron manufacturing from iron ore, combustion residue of
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coke, and fluxes such as serpentine or limestone. If the molten slag is rapidly-cooled using high-pressure water jets, a vitreous Ca–Al–Mg
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silicate fine grain glass is formed. Water cooled slag (granulated blast
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furnace slag) is a glassy, granular material consisting of SiO2, CaO, Al2O3, and MgO. Generally, granulated blast furnace slag is used as
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partially replacing to Portland cement. Granulated blast furnace slag is a
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non-toxic material, and can be used as a raw material for making geopolymers with good mechanical properties as well as in fire resistant applications [42]. In this study ground granulated blast furnace slag, coal fly ash and clay -bricks (Homra) wastes were used as industrial raw materials to produce geopolymeric green cement using sodium silicate(SS) -sodium
ACCEPTED MANUSCRIPT hydroxide(SH) alkaline activator with different SS:SH mass ratio at ambient temperature and 100% relative humidity conditions, 2. Experimental
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2.1 Materials Raw materials used in this investigation are Ground Granulated
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Blast Furnace Slag (GGBS) which is a by-product of iron production,
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Crushed clay bricks (Homra) of Blaine surface area of 5000 cm2/g and
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class F fly ash (FA) of Blaine surface area ≈ 3,800 cm2/g and average diameter ≤ 10 μm. Fly ash is one of the deposits produced from the
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Homra are given in Table (1).
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burning of coal. The chemical oxide compositions for GGBS, Fly ash and
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Alkaline Activated Solution (AAS) used here is a mixture of sodium silicate (Na2SiO3 9H2O., 8M) and sodium hydroxide (NaOH, 10M).
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Distilled water is used to prepare the alkaline activator solution. The
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required mass ratio of sodium silicate and sodium hydroxide solutions are mixed prior to adding to the dry raw materials. Polycarboxylate based superplasticizer is used to maintain the workability of the formed GPC paste without adding extra water. 2.2. Sample preparation
ACCEPTED MANUSCRIPT The dry Mixes with the required composition (as mentioned in Table 2) were prepared by mixing the solid raw materials in ball mill for 8 hours to ensure the complete homogeneity of the dry mixtures. Geopolymer cement pastes (GPC) were prepared by mixing the dry
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sample with the calculated amount of alkaline activator (10% NaOH and
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8% Na2SiO3). The mass ratio of solid raw materials to alkaline activator
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solution used (S: A) is 2:1, while, the ratios of Na2SiO3 (SS) to NaOH
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(SH) to form alkali activator are 0.5, 1.0 and 1.5 (by mass). The addition of small amount of polycarboxylate superplasticizer is required for
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preparation of some pastes prepared using 1.5 SS: SH ratio for
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maintaining a good workability with no extra water addition.
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The resulted pastes were molded into cubic specimens by using cubic moulds having one-inch dimension. The moulds were compacted via
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vibration; the leveling and smoothness of the top surface of the pastes were done by a thin edged towel. After casting, the moulds were cured at
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60 °C in the oven for 24 hours. Then the specimens were removed from their moulds and cured at ambient temperature and about 100 % relative humidity for 3,7 and 28 days. 2.3. Testing and characterization Three cubic specimens were used for the determination of the compressive strength after each curing period, the average of the three
ACCEPTED MANUSCRIPT results was considered. These specimens represented a certain composition and cured for a prescribed period. The compressive strength test was performed using a Ton industry machine (West Germany). Stopping the geopolymerisation process at each curing time was done by
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removing the free water, this was accomplished by drying the crushed
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specimens for 24 hours at 105 °C [43]. The setting times (Initial and
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Final) for each freshly prepared pastes were determined using Vicat
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needle [44].
Water absorption measurements of the hardened geopolymer
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specimens were carried out according to ASTM C140 [45]. The percentage of absorption was calculated using the following equation:
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Absorption (%) = [(W2 – W1)/ W1] ×100 Where: W1 = weight of specimen after complete drying at 105 °C;
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W2 = final weight of the surface dry sample after immersion in water for
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at least 24 hours.
X-ray diffraction technique was carried out on some selected hydrated and dried geopolymer specimens after 28 days of curing to investigate the crystallinity structure and mineralogy of these mixes. The Spectroscopic analysis was performed on some selected hardened geopolymer specimens after 28 days to evaluate the functional groups in
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specimens after 28 days of curing.
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3. Results and Discussion 3.1 Compressive strength
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The compressive strength values for 100% GGBS based
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geopolymer cement (GPC) hardened specimens, prepared using solid/activator (S:A) ratio of 2:1 and sodium silicate/sodium hydroxide
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(SS: SH) ratios of 0.5,1 and 1.5 (Mixes A1-A3) after 3,7 and 28 days of
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curing at ambient room temperature, and ~ 100 relative humidity are shown in Fig.1. The compressive strength values indicated a continuous
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increase with increasing the age of curing for all tested specimens (Mixes
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A1-A3). In addition, as the SS: SH ratio increase the compressive strength values increase. The increase in the compressive strength values indicating the formation of geopolymer with good mechanical properties via the alkali activation of GGBS. This results can be explained in terms of the higher reactivity of GGBS, which in the presence of the alkaline activator (OH−), promote the rupture of bonds in its structure (Ca-O; Si-O and Al-O) that
ACCEPTED MANUSCRIPT forms dissolved species (Ca2+; [H2SiO4]2−, [H3SiO4]−and [Al(OH)4]−), which can precipitate when reaches to supersaturation forming CSH and C-A-S-H hydrate [34]. Besides, the calcium ions present in GGBS enter in the Si-O-Al gel structure, which compensates the charge of the
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aluminum atoms (Al3+) and allows space for the C-A-S-H system in
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addition to the N-A-S-H gel. This leads to the formation of a more-
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denser structure [35-37]
Obviously, the GPC specimens prepared using the highest contents
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of sodium hydroxide (SS: SH mass ratio of 0.5), showed the lowest
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compressive strength development among the other SS: SH ratios at all tested ages and thus indicated the lowest geopolymerization reaction.
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Evidently, under lower alkalinity conditions (high SS: SH ratio), the
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dissolution of calcium ions (Ca2+) from GBFS is promoted and consequently the formation of C-S-H gels is pronounced, leading to
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stable gel coexistence, but higher alkalinity (low SS: SH ratio) tends to
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lead to Ca(OH)2 precipitation. Obviously, for GPC specimens prepared using alkaline activator (SS: SH) mass ratio of 1.0 -1.5 the geopolymer indicated a relatively high strength development during all curing periods. The high strength development in the GPC specimens prepared using SS: SH mass ratios of 1.0 and 1.5 reveals the complexity of the geopolymerization process and indicates the effect of the concentration of the alkaline activator
ACCEPTED MANUSCRIPT constituents. Evidently, the presence of dissolved silicon in the aqueous solution of sodium silicate contributes to the increase of compressive strength. The higher concentration of dissolved silicon in the matrix produces higher compressive strength values, but only for certain limit,
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further increase in silicon ions concentration causes a notable decrease in
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the compressive strength values [22]. Researchers have suggested that the
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optimum SS: SH ratio to produce geopolymer having high strength is in the range 0.67–1.00 [37]. In general, the use of sodium silicate helps to
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improve and increase the rate of the geopolymerisation process by
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accelerating the dissolution of the source material. These results are in agreement with previously obtained results [5,12].
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Finally, the slight decrease in the compressive strength values
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observed with increasing SS: SH ratio from 1 to 1.5 in the alkaline solution, is mainly attributed to increasing the amount of unreacted
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material, which increases with silicon concentration and has a deleterious
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effect on the mechanical strength of geopolymers [38,39]. Moreover, it could be attributed to increasing the viscosity of the reaction matrix with increase SS: SH ratio and thus hindered the mass transport through the solution which leads to a low strength of geopolymer paste. On conclusion, the obtained results revealed that the compressive strength of the formed geopolymers increases with increasing SS: SH ratio, due to the promotion of polymerization reaction [40]
ACCEPTED MANUSCRIPT The GPC specimens prepared from 95% GGBS + 5% FA and 90% GGBS +10 FA by using 2 :1 (S: A) and SS: SH ratios of 0.5,1 and 1.5 (Mixes B1-B3 and C1-C3), respectively, after different curing periods at ambient room temperature at ~ 100 relative humidity are shown in Figs.
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(2) and (3). The compressive strength values of these GPC specimens
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showed a continuous increase with increasing curing age. Also, as the SS:
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SH ratio increases from 0.5 to 1 causes increase the compressive strength values, but a slight decrease in the compressive strength values was
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discussed in the previous section.
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observed by increase SS: SH to 1.5, the reasons for these results were
Comparing the results of Fig (1), (2) and (3), a slight increase in the
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compressive strength values was observed in the case of replacing GGBS
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by 5% FA only in case of SS: SH is 1 after all curing ages. While in the case of SS: SH 0.5 or 1.5 these mixes showed a slight decrease in the
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compressive strength values at all curing periods. While replacing GGBS
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with 10%FA causes the compressive strength values to decrease during all tested periods at different SS: SH ratios (when compared with Mixes A or B). These results can be explained in terms of the increase in the amount of unreacted silicon by the presence of excess amount of FA, which has a deleterious effect on the mechanical strength of geopolymers [38].
ACCEPTED MANUSCRIPT Figures (4) and (5) show the compressive strength values of GPC specimens prepared from 95% GGBS+5% Homra and 90 %GGBS +10 % Homra by using S: A ratio 2:1 and SS: SH ratios 0.5,1 and 1.5 (Mixes D1-D3 and E1-E3), respectively, after different curing periods at ambient
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room temperature at ~ 100 relative humidity. The figures indicated a
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continuous increase in the compressive strength values with increasing
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the curing age for all mixes. Besides, the variation of compressive strength value with SS: SH ratios for these Mixes is the same as in the
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case of other prepared GPC specimens (Mixes A, B, and C). Obviously,
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replacing GGBS by 5 or 10% Homra gives higher and or/comparable compressive strength values as compared with geopolymer made from
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100% GGBS during all ages of hydration at different SS: SH ratios.
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Besides, increasing the amount of GGBS replaced by Homra from 5% to 10% the compressive strength values showed a slight decrease (but still
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higher than GPC made from 100 GGBS), which is attributed to the same
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reason mentioned previously in the case of fly ash substitution. 3.2. Absorption studies This test was done to investigate the relative porosity or permeability characteristics of the hardened GPC pastes. The values of water absorption for different mixes investigated after 28 days of curing at ambient temperature are given in Fig. (6). It is clear that for all tested GPC specimens the water absorption decreases with increasing the SS:
ACCEPTED MANUSCRIPT SH ratio from 0.5 to 1, then a slight increase with a further increase of this ratio to 1.5 was observed. Obviously, these results are in agree with the obtained compressive strength results. Obviously, GPC specimens prepared from different mixes using SS/SH ratio 1 showed the lowest
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water absorption values, these results are in agree with the obtained
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compressive strength results, which indicated higher compressive
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strength values for these mixes, indicating a low degree of porosity.
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3.3. Setting Time
The results of the initial and final setting times for all tested GPC
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specimens are shown in Figs. (7) and (8), respectively. The initial setting
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times ranges from 4 to 88 minutes while the final setting time ranged from 9 to 385 minutes. Evidently, the results revealed that the initial and
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final setting times are largely affected by two main factors namely (i)
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Sodium silicate: sodium hydroxide ratio and (ii) The % replacement of GGBS by FA or Homra. Obviously, the results showed a notable decrease in both initial and final setting times values with increasing the SS: SH ratio for all tested fresh pastes. Besides, the gap between the initial and final setting increase. Obviously, GPC specimens made with least amount of sodium silicate (SS/SH ratio of 0.5) have the longest initial and final setting times compared to those made with 1 and 1.5
ACCEPTED MANUSCRIPT SS/SH ratios. This result is attributed to the reduction in the amount of Si present in the mix, which results in slow down the polymerization process [41]. Increasing the ratio SS: SH in the alkaline activator solution decreased
setting
time
which
reveals
increasing
the
rate
of
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geopolymerisation [40], Figs. (7) and (8). These results illustrate the
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influence of chemical compositions of alkaline activator on the rate of
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setting. Evidently, upon increasing the SS: SH ratio from 0.5 to 1.5, the amount of soluble silica increase, the polymerization process is
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accelerated so, the initial and final setting times decreased. Replacing
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GGBS with different amount of FA or Homra (5 or 10% by mass of slag) causes a notable increase in both the initial and final setting times,
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indicating retardation of the rate of polymerization process by the
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presence of these waste materials. 3.4. XRD analysis
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The XRD patterns of GPC specimens made from Mixes A1, B1,
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C1, D1 and E1 after 28 days' hydration are shown in Fig.9. The diffraction patterns of all tested mixes have a large diffused hump in the region of 27-33o centered at about 29.5o, this hump is characterizing for the glassy phase of the formed geopolymer, mainly as CSH gel [42,46]. The intensity and the degree of broadening of this hump are increased with increasing the amorphous constituents (CSH content) of the formed geopolymer [47]. Replacement of GGBS with 5 and 10 % of FA or
ACCEPTED MANUSCRIPT Homra indicated the same diffraction patterns as that of Mix A1 (100% GGBS) but with the appearance of a new peaks in the XRD patterns which characteristic for quartz and calcite, the appearance of calcite in these patterns is due to the carbonation of the geopolymer specimens, Fig
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(9).
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The GPC specimens prepared using SS: SH ratio 1 (Mixes A2, B2,
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C2, D2, and E2) indicated the same diffraction patterns as their corresponding ones prepared using SS: SH- 0.5, Fig. (10). Obviously,
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from Fig (10) we can note an increase in the intensity and broadening of
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the diffused hump obtained at 29.5o (characteristic for amorphous CSH) in the XRD pattern of these GPC specimens, which confirm the increase
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in the amount of amorphous CSH formed with increasing the SS:SH ratio
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from 0.5 to 1, these results agree with the results of compressive strength development obtained.
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3.5. Fourier Transform Infrared Spectroscopy (FTIR) Analysis
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Figures (11) and (12) display the IR spectra of geopolymer samples prepared using 0.5 and 1 SS/SH ratios, respectively, after 28 days of curing at ambient temperature and 100% relative humidity. Evidently, at both SS: SH ratios all the tested GPC specimens showed broad bands appearing around 3425 and 2380 cm−1, due to stretching vibrations OH and HOH. In addition, the bending vibration of HOH was detected at about 1650 cm−1. these absorption bands are characteristics to crystalline
ACCEPTED MANUSCRIPT H2O of the hydrated products such as C–S–H and calcium aluminosilicate (C–A–S-H), as well as the presence of entrapped water molecules in the geopolymeric network [28,48]. stretching vibration of O-C-O was detected for all tested GPC specimens at 1460 cm−1 which is attributed to
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the carbonation reaction. The carbonation process occurred as a result of
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the presence of excessive amount of Na (present from NaOH in activator
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solution) where it reacted with CO2 from the atmosphere [49]. The band attributed to asymmetric stretching vibration of Si-O-Si and Al-O-Si at
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about 970 cm−1 indicated the formation of aluminosilicate gel. Besides
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that, symmetric stretching vibrations Si-O-Si were located at 670–720 cm−1.Also, the bending vibrations of Si-O-Si and O-Si-O were found at
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450 cm−1 [49,50].
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From Figs. (11) and (12) the FTIR patterns showed a notable increase in the intensity of C-A-S-H and CSH gel with increasing the
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SS:SH ratio from 0.5 to 1 and with substituting GGBS with 5% of FA or
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Homra, indicating increase the amount of geopolymer formed, these results confirmed the obtained compressive strength values for these mixes. Besides, an increase in intensity of broad bands appeared in the IR -1
spectra of these mixes, in the region of 3425 and 1650 cm was observed which assigned to stretching (-OH) and bending (H-O-H) vibrations of bound water molecules, which are surface absorbed or entrapped in the
ACCEPTED MANUSCRIPT large voids of the polymeric network [51]. This implies that the Geopolymers ability to adsorb water in their three-dimensional framework increases with the substitution of slag with FA or Homra. 3.6. Morphology and Microstructure
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The microstructure of the hardened geopolymer specimens
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prepared using 0.5 - SS: SH ratio (Mixes A1, B1, D1) after 28 days of
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curing at ambient temperature are shown in Figs. (13-15). In generally, the SEM micrographs of all these specimens indicate the formation of with
mostly
amorphous
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geopolymer
phases.
Obviously,
the
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microstructure of GPC specimens made from 100 GGBS had a dense – gel-like solid matrix with a uniform structure of hydration products
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mainly as calcium alumino-silicate hydrate (C–A–S–H) imbedded with
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micro-fibrous crystals of CSH and nearly absence of pores [46]. In addition, the unreacted slag particles also appear on the surface of the
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dense geopolymer matrix, Fig. (13-a, b). Evidently, the pastes having 5%
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FA or Homra (Mixes B1 and D1) are more compact and less porous than that having 100% GGBS (Mix A1), Figs. (14-a, b) and (15- a,b), respectively. The SEM micrographs of the GPC specimens prepared using SS: SH ratio 1 (Mixes A2, B2, and D2) indicated a more compact and dense micro structure as a result of increase the amounts of formed aluminosilicate geopolymeric materials which dispersed with micro -
ACCEPTED MANUSCRIPT fibrous of CSH. Consequently, this will enhance the binding characteristics of Geopolymer specimens, Figs. (16-18). These results revealed that the ratio of alkaline activator (SS: SH ratio) affect the saturation rate of the geopolymeraisation process as well as the
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compressive strength of the formed geopolymer [28]. Obviously, these
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results confirmed the obtained results of compressive strength mentioned
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previously. Finally, the partially reacted and un-reacted fly ash, Homra and slag particles are more commonly visible in the paste made with SS:
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SH ratio 0.5 more than that made with 1.
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Conclusions
The major findings of this work are summarized as follows:
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1. Partial replacement of slag by 5 and 10 % Homra effectively increase
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the compressive strength, enhanced microstructural properties and formed compact geopolymeric structures, as it increased the rate of
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Geopolymerization reaction.
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2. Replacing GGBS with 5%FA improves the mechanical properties and microstructure of the produced GPC only when using SS: SH ratio 1, while replacing it with 10%FA causes a slight decrease in the compressive strength values as compared with 100% GGBS based geopolymer.
ACCEPTED MANUSCRIPT 3. The SS: SH ratio plays an important role in the mix design of the geopolymer paste, the optimum ratio for SS: SH is 1 while the ratio 0.5 give the least compressive strength values. 4. Both the initial and final setting times increase with decreasing the
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SS:SH.
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5. Water absorption of the formed geopolymers decreased with increasing
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SS: SH ratio from 0.5 to 1 then showed a slight increase with a further increase to 1.5.
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This research did not receive any specific grant from funding agencies in
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the public, commercial, or not-for-profit sectors.
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Cement and Concrete Research 30 (2000) 1625-1632. [25] P. Duxson, A. Fernandez-Jimenez, J.L. Provis, G.C. Lukey, A. Palomo, J.S.J. van Deventer, Geopolymer technology: the current state of the art, Journal of Materials Science 42(9) (2007) 2917-2933. [26] E.I. Diaz, E.N. Allouche, S. Eklund, Factors affecting the suitability of fly ash as source material for geopolymers, Fuel 89 (2010) 992-996.
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7 days
28 days
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25.9
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31.7
29.9
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3 days
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A1
A2
A3
Geopolymer mixes
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Fig.1 Compressive strength values of GPC specimens made from Mixes (A1-A3) after different ages of curing.
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Fig.2 Compressive strength values of GPC specimens made from Mixes (B1-B3) after different ages of curing.
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Fig.3 Compressive strength values of GPC specimens made from Mixes (C1-C3) after different ages of curing.
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Fig.4 Compressive strength values of GPC specimens made from Mixes (D1-D3) after different ages of curing.
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Fig.5 Compressive strength values of GPC specimens made from Mixes (E1-E3) after different ages of curing.
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Fig.6 Water absorption values of different GPC Mixes after 28 days of curing.
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Fig.7 Initial setting times values for different GPC Mixes
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Fig.8 Final setting times values for different GPC Mixes
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Fig.9.XRD patterns of some selected geopolymers specimens after 28 days of hydration.
[CSH : calcium silicate hydrate, Q : Quartz ,CC :calcium carbonate]
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Fig.10 XRD patterns of some selected geopolymers specimens after 28 days of hydration. [CSH : calcium silicate hydrate, Q : Quartz ,CC :calcium carbonate]
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Fig.11 FTIR spectra of geopolymer specimens after 28 days of hydration
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Fig.12 FTIR spectra of geopolymer specimens after 28 days of hydration
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Fig. 13 SEM of geopolymer made from Mix A1 after 28-days
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Fig.14 SEM image of geopolymer made from Mix A2 after 28 days.
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Fig. 15 SEM image of geopolymer made from Mix B1 after 28 days.
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Fig.16 SEM image of geopolymer made from Mix B2 after 28 days.
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Fig.17 SEM image of geopolymer made from Mix D1 after 28 days.
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CE
PT E
D
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
Fig. 18 SEM image of geopolymer made from Mix D2 after 28 days.
ACCEPTED MANUSCRIPT
Fe2O3
CaO
MgO
GGBS
41.78
10.55
3.52
32.18
6.63
1.16
Fly ash
76.65
33.01
4.89
1.81
Homra
64.87
15.61
8.27
3.00
1.48
D PT E CE AC
Na2O
LOI
SC
Al2O3
Material
MA
SiO2
NU
RI
Oxides (mass%)
PT
Table 1. Chemical oxide composition of raw materials.
SO3 K2O 0.85
0.27
-0.73
0.87
0.01
1.05
0.17
0.95
0.92
1.12
1.30
1.74
ACCEPTED MANUSCRIPT
Table 2. The percentage composition of the different geopolymer mixes and their designations.
Fly ash
Homra
A1
100
-
-
A2
100
-
-
A3
100
-
B1
95
5
B2
95
5
B3
95
C1
90
Na2SiO3/NaOH
PT
GGBS
SC
RI
Mixes
0.5 1.0 1.5
-
0.5
-
1.0
5
-
1.5
10
-
0.5
90
10
-
1.0
90
10
-
1.5
95
-
5
0.5
D2
95
-
5
1.0
D3
95
-
5
1.5
E1
90
-
10
0.5
E2
90
-
10
1.0
E3
90
-
10
1.5
AC
CE
C3 D1
MA D
PT E
C2
NU
-