Geopolymer Composition, A Method For Preparing the Same and Its Uses

Abstract

A geopolymer composition for use as a cement or concrete is provided, the composition comprising: (a) fly ash (FA); (b) ground granulated blast-furnace slag (GGBS); and (c) high-magnesium nickel slag (HMNS). The composition may optionally comprise a filler. A method for forming a geopolymer composition is also provided, the method comprising: providing a geopolymer precursor comprising: (a) fly ash (FA); (b) ground granulated blast-furnace slag (GGBS); and (c) high-magnesium nickel slag (HMNS); combining components (a) to (c) with an activator, the activator comprising a silicate and a base in solution in a solvent; and allowing the resulting mixture to cure. The geopolymer composition advantageously comprises one or more allotropes of carbon, in particular a carbon nano-structure material, for example nanotubes, nanobuds and nanoribbons. The geopolymer composition finds use in form a wide range of construction components and structures.

Claims

1. A geopolymer composition comprising: (a) fly ash (FA); (b) ground granulated blast-furnace slag (GGBS); and (c) high-magnesium nickel slag (HMNS).

2. The geopolymer composition according to claim 1, wherein the weight ratio of fly ash and ground granulated blast-furnace slag is greater than 1:1.

3. The geopolymer composition according to claim 1, wherein the weight ratio of fly ash and high-magnesium nickel slag is greater than 1.1.

4. The geopolymer composition according to claim 1, wherein the weight ratio of ground granulated blast-furnace slag and the high-magnesium nickel slag is from 10:1 to 1:2.

5. The geopolymer composition according to claim 1, further comprising a filler, wherein the filler is one or more of an aggregate, an allotrope of carbon, a rubber, an elastomer and a plant material.

6. (canceled)

7. The geopolymer composition according to claim 5, wherein the allotrope of carbon is a carbon nano-structure material.

8. The geopolymer composition according to claim 5, wherein the filler is an allotrope of carbon and is present in an amount of from 0.2% by weight.

9. A method for forming a geopolymer composition, the method comprising: providing a geopolymer precursor comprising: (a) fly ash (FA); (b) ground granulated blast-furnace slag (GGBS); and (c) high-magnesium nickel slag (HMNS); combining components (a) to (c) with an activator, the activator comprising a silicate and a base in solution in a solvent; and allowing the resulting mixture to cure.

10. The method according to claim 9, wherein the silicate comprises an alkali metal silicate.

11. The method according to claim 9, wherein the base comprises a basic salt of an alkali metal, an alkaline earth metal or ammonia.

12. (canceled)

13. The method according to claim 9, wherein the concentration of basic anions in the solvent is from 5M.

14. The method according to claim 9, wherein the weight ratio of the geopolymer precursor and the activator is greater than 1:1.

15. A method for forming a geopolymer composition comprising one or more of fly ash, granulated blast furnace slag and high-magnesium nickel slag and one or more allotropes of carbon, the method comprising: i) providing a suspension of the carbon allotrope in a solvent; ii) combining the suspension provided in step i) with one or more of fly ash, granulated blast furnace slag and high-magnesium nickel slag; and iii) combining the resulting mixture with an activator.

16. The method according to claim 15, wherein the solvent is an organic solvent, selected from one or more of alcohols, aldehydes and ketones.

17. The method according to claim 16, wherein the solvent comprises acetone.

18. The method according to claim 15, wherein the allotrope of carbon is a carbon nano-structure material.

19-25. (canceled)

Description

EXAMPLES

Example 1— Geopolymer Composition

[0101] A geopolymer composition was prepared from fly ash (FA), ground granulated blast furnace slag (GGBS) and high-magnesium nickel slag (HMNS), together with an alkaline activator, as follows:

[0102] Class F FA was obtained from Manjung power plant at Perak in Malaysia. The average particle size of the FA was about 18 μm. The specific surface area of the FA was around 1.29 m.sup.2/g.

[0103] GGBS was obtained from the steel plant at Penang in Malaysia. The average particle size of the GGBS was about 138 μm. The specific surface area of the GGBS was around 0.106 m.sup.2/g.

[0104] HMNS was obtained from the steel plant in Shaanxi Province, China. The average particle size of the HMNS was about 280 μm. The specific surface area of the HMNS was around 0.0536 m.sup.2/g.

[0105] The chemical compositions of the FA, GGBS and HMNS are summarised in Table 1, which were determined using x-ray fluorescence analysis.

TABLE-US-00001 TABLE 1 Class FA GGBS HMNS Component (wt %) (wt %) (wt %) SiO.sub.2 55.7 28.2 43.22 Al.sub.2O.sub.3 27.8 9.73 4.35 Fe.sub.2O.sub.3 7.27 0.98 10.34 CaO 4.10 52.69 3.45 TiO.sub.2 2.29 1.01 0.1 SO.sub.3 0.27 1.46 0.28 K.sub.2O 1.55 1.22 0.18 MgO — 2.9 26.15 MnO — 0.74 0.89 P.sub.2O.sub.5 — — 0.05 Na.sub.2O — — 0.23 Cr.sub.2O.sub.3 — — 1.01 LOI 3.04 3.76 0.3 Others 1.018 1.05 9.4

[0106] An alkaline activator was prepared as follows:

[0107] A sodium silicate solution was obtained from South Pacific Chemicals Industries (SPCI) Ltd in Malaysia, with the chemical composition of 14.7 wt % Na.sub.2O, 29.8 wt % SiO.sub.2, and 55.5 wt % water.

[0108] A sodium hydroxide solution was prepared in the laboratory by dissolving sodium hydroxide pellets in water. To prepare the sodium hydroxide solution with a concentration of 12M, 480 grams of sodium hydroxide pellets supplied by Formosa Plastic Corporation, Taiwan were dissolved in 1 litre of distilled water. After cooling for 24 hours at room temperature, the sodium hydroxide solution was then mixed with the sodium silicate solution.

[0109] The mass ratio of sodium silicate to sodium hydroxide solution was 2.5. This provides a weight ratio of silicate ions and hydroxide ions of about 4:1.

[0110] The FA, GGBS, HMNS and activator solution were combined in the amounts indicated in Table 2 below.

TABLE-US-00002 TABLE 2 Component Example 1 Class F FA (kg/m.sup.3) 420 GGBS (kg/m.sup.3) 120 HMNS (kg/m.sup.3) 60 Na.sub.2SiO.sub.3 solution (kg/m.sup.3) 214.28 NaOH solution (12M) (kg/m.sup.3) 85.71 Na.sub.2SiO.sub.3/NaOH weight ratio 2.5 Solid/alkaline activator weight ratio 2.0

[0111] To prepare the geopolymer composition, the solid FA, GGBS and HMNS were placed in a mixing vessel and stirred to form a dry mixture. The activator solution was added to the dry mixture and the mixture stirred to form a uniform paste.

[0112] The geopolymer paste was placed in cubic moulds and covered with a plastic film for 24 hours. Thereafter, the contents of the moulds were removed and cured at room temperature (25+/−2° C.) at a relative humidity of 85 to 90%.

[0113] Samples of the geopolymer composition were allowed to cure for 7 or 14 days before testing.

Examples 2 to 4— Geopolymer Compositions

[0114] The method of Example 1 above was repeated to prepare geopolymer compositions having a range of compositions.

[0115] The compositions of the geopolymer compositions are summarised in Table 3 below.

TABLE-US-00003 TABLE 3 Component Example 2 Example 3 Example 4 Class F FA 450 390 300 (kg/m.sup.3) GGBS (kg/m.sup.3) 120 120 120 HMNS (kg/m.sup.3) 30 90 120 Na.sub.2SiO.sub.3 solution 214.28 214.28 214.28 (kg/m.sup.3) NaOH solution 85.71 85.71 85.71 (12M) (kg/m.sup.3) Na.sub.2SiO.sub.3/NaOH 2.5 2.5 2.5 weight ratio Solid/alkaline 2.0 2.0 2.0 activator weight ratio

Example 5— Setting Time Tests

[0116] The setting time of the geopolymer composition of Example 1 was determined using a Vicat apparatus.

[0117] The initial setting time was taken to be the time elapsed from the addition of the activator solution to the dry mixture to the point in time when the paste began to lose its elasticity.

[0118] The final setting time was taken to be the time elapsed from the addition of the activator solution to the dry mixture to the point in time when the paste lost all its elasticity.

[0119] The results are set out in Table 4 below.

TABLE-US-00004 TABLE 4 Initial Setting Time Final Setting Time (min) (min) Example 1 310 1490

Example 6— Strength Tests of Geopolymer Composition

[0120] The cured samples of Examples 1 to 4 were subjected to a test to determine their compressive strength.

[0121] The compressive strength tests were performed using a universal testing machine, under a load control regime with a loading rate of 0.3 kN/s in accordance with the ASTM C496 standard.

[0122] All tests were carried out in triplicate and average values were obtained and used as the results.

[0123] The results of the compressive strength tests are summarised in Table 5 below.

TABLE-US-00005 TABLE 5 Example No. and Curing Time Compressive Strength (MPa) Example 1 - 7 days 39.95 Example 1 - 14 days 60.82 Example 2 - 7 days 35.69 Example 2 - 14 days 47.54 Example 3 - 7 days 32.79 Example 3 - 14 days 38.56 Example 4 - 7 days 33.15 Example 4 - 14 days 47.78

Example 7— Concrete Composition

[0124] A concrete composition was prepared from a geopolymer composition comprising fly ash (FA), ground granulated blast furnace slag (GGBS) and high-magnesium nickel slag (HMNS), together with an alkaline activator, and aggregate as follows:

[0125] Class F FA was obtained from Manjung power plant at Perak in Malaysia. The average particle size of the FA was about 18 μm. The specific surface area of the FA was around 1.29 m.sup.2/g.

[0126] GGBS was obtained from the steel plant at Penang in Malaysia. The average particle size of the GGBS was about 138 μm. The specific surface area of the GGBS was around 0.106 m.sup.2/g.

[0127] HMNS was obtained from the steel plant in Shaanxi Province, China. The average particle size of the HMNS was about 280 μm. The specific surface area of the HMNS was around 0.0536 m.sup.2/g.

[0128] The chemical compositions of the FA, GGBS and HMNS are summarised in Table 1 above.

[0129] An alkaline activator was prepared as follows:

[0130] A sodium silicate solution was obtained from South Pacific Chemicals Industries (SPCI) Ltd in Malaysia, with the chemical composition of 14.7 wt % Na.sub.2O, 29.8 wt % SiO.sub.2, and 55.5 wt % water.

[0131] A sodium hydroxide solution was prepared in the laboratory by dissolving sodium hydroxide pellets in water. To prepare the sodium hydroxide solution with a concentration of 12M, 480 grams of sodium hydroxide pellets supplied by Formosa Plastic Corporation, Taiwan were dissolved in 1 litre of distilled water. After cooling for hours at room temperature, the sodium hydroxide solution was then mixed with the sodium silicate solution.

[0132] The mass ratio of sodium silicate to sodium hydroxide solution was 2.5.

[0133] River sand of particle sizes not exceeding 5 mm and gravel of particle sizes ranging from 5 mm and 19 mm were used as the fine and coarse aggregates, respectively. The density of the fine aggregate was 1640 kg/m.sup.3. The density of the coarse aggregate was 1204 kg/m.sup.3.

[0134] The mass ratio of fine aggregate to coarse aggregate was 3:7 for all experiments.

[0135] The coarse aggregate was saturated in water for about 2 hours, then left to dry at a room temperature of 25+/−2° C. and a relative humidity of 85 to 90% for another 1 hour until the water film on the surface visibly vanished, before it was mixed with the dry binder composition and alkaline activator solution. This was to ensure that the gravel would not absorb excessive amounts of the activator solution when the components were mixed together.

[0136] The FA, GGBS, HMNS, aggregate and activator solution were combined in the amounts indicated in Table 6 below.

TABLE-US-00006 TABLE 6 Component Example 7 Class F FA (kg/m.sup.3) 336 GGBS (kg/m.sup.3) 96 HMNS (kg/m.sup.3) 48 Na.sub.2SiO.sub.3 solution (kg/m.sup.3) 171.43 NaOH solution (12M) (kg/m.sup.3) 68.6 Coarse aggregate (kg/m.sup.3) 1176 Fine aggregate (kg/m.sup.3) 504 Na.sub.2SiO.sub.3/NaOH weight ratio 2.5 Solid binder/alkaline activator weight ratio 2.0

[0137] To prepare the concrete composition, the solid FA, GGBS, HMNS and aggregates were placed in a mixing vessel and stirred to form a dry mixture. The activator solution was added to the dry mixture and the mixture stirred until uniform.

[0138] The concrete composition was placed in cubic moulds and covered with a plastic film for 24 hours. Thereafter, the contents of the moulds were removed and cured at room temperature (25+/−2° C.) at a relative humidity of 85 to 90%.

[0139] Samples of the concrete composition were allowed to cure for 7, 14, 28 and 90 days before testing.

Example 8— Concrete Compositions

[0140] The method of Example 7 above was repeated to prepare a concrete composition.

[0141] The composition of the concrete composition is summarised in Table 7 below.

TABLE-US-00007 TABLE 7 Component Example 8 Class F FA (kg/m.sup.3) 222.6 GGBS (kg/m.sup.3) 63.6 HMNS (kg/m.sup.3) 31.8 Na.sub.2SiO.sub.3 solution (kg/m.sup.3) 113.6 NaOH solution (12M) (kg/m.sup.3) 45.5 Coarse aggregate (kg/m.sup.3) 779 Fine aggregate (kg/m.sup.3) 333.7 Na.sub.2SiO.sub.3/NaOH weight ratio 2.5 Solid binder/alkaline activator weight ratio 2.0

[0142] The concrete composition was placed in cylindrical moulds and covered with a plastic film for 24 hours. Thereafter, the contents of the moulds were removed and cured at room temperature (25+/−2° C.) at a relative humidity of 85 to 90%.

[0143] Samples of the concrete composition were allowed to cure for 7, 14, 28 and 90 days before testing.

Example 9— Slump Test

[0144] The slump of the concrete composition of Example 7 was tested from the point in time the mixture was removed from the mould to the point in time when the slump reached zero.

[0145] The results are set out in Table 8 below.

TABLE-US-00008 TABLE 8 Time (min) Slump (mm) 0 220 40 115 80 70 120 55 160 40 200 25 240 15 280 0

Example 10— Strength Tests of Concrete Composition

[0146] The cured concrete samples of Example 7 were subjected to a test to determine their compressive strength.

[0147] The compressive strength tests were performed using a universal testing machine, under a load control regime with a loading rate of 0.3 kN/s in accordance with the ASTM C496 standard.

[0148] All tests were carried out in triplicate and average values were obtained and used as the results.

[0149] The results of the compressive strength tests are summarised in Table 9 below.

TABLE-US-00009 TABLE 9 Curing Time (days) Compressive Strength (MPa) 7 27.17 14 43.43 28 55.6 90 48.14

[0150] The cured concrete samples of Example 7 were subjected to a test to determine their splitting tensile strength.

[0151] The splitting tensile strength tests were performed using a universal testing machine, under a load control regime with a constant load rate of 1.0 kN/min in accordance with the ASTM C496 standard.

[0152] All tests were carried out in triplicate and average values were obtained and used as the results.

[0153] The results of the compressive strength tests are summarised in Table 10 below.

TABLE-US-00010 TABLE 10 Curing Time (days) Splitting Tensile Strength (MPa) 7 2.89 14 3.65 28 4.57 90 4.12

Example 11— Chloride Ion Migration Tests of Concrete Composition

[0154] Cured concrete samples prepared by the method of Example 7 were subjected to a test to determine the extent of chloride ion migration.

[0155] To investigate the migration of chloride ions into the concrete composition, a Rapid Chloride Permeability Test (RCPT) was conducted according to the procedure described in Nord Test Standard (NT Build 492, 1999).

[0156] In summary, in the test, a sample of the concrete composition was held in a rubber sleeve between an anode and a cathode while immersed in a reservoir containing, as a catholyte, a solution of NaCl and tap water (100 g of NaCl for each 900 g of tap water). The rubber sleeve contained an anolyte solution comprising 0.3M NaOH in de-ionised water. The temperature was maintained to be from 20 to 25° C. A DC voltage was applied across the anode and cathode.

[0157] After testing, each sample was split axially and a silver nitrate solution (0.1N AgNO.sub.3) was sprayed onto the faces of the split. The depth of the region of change of colour was measured using a ruler and caliper at intervals along the sample and the average depth calculated.

[0158] The chloride migration coefficient is obtained using Fick's Second Law:

[00001]$D_{nssm}=\frac{0.0239\left(273+T\right)*L}{\left(U-2\right)*t}\left(X_d-0.0238\sqrt{\frac{\left(273+T\right)*L*X_d}{U-2}}\right)$

[0159] where:

[0160] D.sub.nssm is the non-steady-state migration coefficient [x10.sup.−12 m.sup.2/s];

[0161] U is the absolute value of the applied voltage [V];

[0162] T is the average value of the temperature of the anolyte solution [° C.];

[0163] L is the thickness of the specimen [mm];

[0164] X.sub.d is the average value of the penetration depths [mm]; and

[0165] t is the duration of the test [Hours].

[0166] The results after 75 and 210 days are summarised in Tables 11a and 11b below.

TABLE-US-00011 TABLE 11a Chloride Migration Coefficient D.sub.nssm at Average Temperature Applied 75 days Sample Depth (+/−2) Voltage (×10.sup.−11 No. (mm) (° C.) (V) m.sup.2/s) 1 11.60 18.2 15 0.66 2 7.10 18.2 15 0.55 3 9.40 18.2 15 0.77 Average 9.37 0.66

TABLE-US-00012 TABLE 11b Chloride Migration Coefficient D.sub.nssm at Average Temperature Applied 210 days Sample Depth (+/−2) Voltage (×10.sup.−11 No. (mm) (° C.) (V) m.sup.2/s) 1 NA 20 20 NA 2 11.96 20 15 1.032 3 8.47 20 15 0.689 Average 10.21 0.86

Example 12— Thermal Resistance Tests of Concrete Composition

[0167] Cured concrete samples prepared by the method of Example 7 were subjected to a test to determine their thermal resistance.

[0168] Each sample was heated in an oven with the temperature increased at a rate of 6° C./min until the test temperature was reached. The sample was held at the test temperature for 2 hours. The sample was then allowed to cool to room temperature.

[0169] The compressive strength of each sample was measured both before and after heating. The compressive strength tests were performed using a universal testing machine, under a load control regime with a loading rate of 0.3 kN/s in accordance with the ASTM C496 standard.

[0170] All tests were carried out in triplicate and average values were obtained and used as the results.

[0171] The results are set out in Table 12 below.

TABLE-US-00013 TABLE 12 Compressive Reduction in Test strength after compressive Temperature heating Standard strength (° C.) (MPa) Error (%) Ambient (20° C.) 48.40 2.4205 — 200 49.84 2.492 −2.96 300 31.19 1.56 35.54 400 31.05 1.5525 35.84 500 31.94 1.597 34.00 600 22.97 1.1485 52.53 700 21.82 1.091 54.91 800 22.42 1.121 53.66 900 20.56 1.028 57.52

Examples 13 to 17— Geopolymer Composition with Carbon Nanotubes

[0172] A range of geopolymer compositions was prepared from fly ash (FA), ground granulated blast furnace slag (GGBS), high-magnesium nickel slag (HMNS) and carbon nanotubes, together with an alkaline activator, as follows:

[0173] Class F FA was obtained from Manjung power plant at Perak in Malaysia. The average particle size of the FA was about 18 μm. The specific surface area of the FA was around 1.29 m.sup.2/g.

[0174] GGBS was obtained from the steel plant at Penang in Malaysia. The average particle size of the GGBS was about 138 μm. The specific surface area of the GGBS was around 0.106 m.sup.2/g.

[0175] HMNS was obtained from the steel plant in Shaanxi Province, China. The average particle size of the HMNS was about 280 μm. The specific surface area of the HMNS was around 0.0536 m.sup.2/g.

[0176] The chemical compositions of the FA, GGBS and HMNS are summarised in Table 1 above, which were determined using x-ray fluorescence analysis.

[0177] Multi-walled carbon nanotubes were obtained from US Research Nanomaterials Inc., Houston, Tex. The carbon nanotubes were synthesized using chemical vapour deposition and had a purity of greater than 97%.

[0178] The carbon nanotubes had an outside diameter of from 5 to 15 nm, an inside diameter of from 3 to 5 nm and a length of from 40 to 50 μm.

[0179] The carbon nanotubes were added to acetone (50 mL) and dispersed using a high frequency sonicator (1000 W, BR-20MT-10 L) operated in a pulsed mode (50 seconds on, 10 seconds off) for 5 minutes. Thereafter, the FA, GGBS and HMNS were added and the resulting mixture stirred until uniform. The resulting mixture was placed in an oven at 60° C. for 1 hour to remove the acetone by evaporation.

[0180] An alkaline activator was prepared as follows:

[0181] A sodium silicate solution was obtained from South Pacific Chemicals Industries (SPCI) Ltd in Malaysia, with the chemical composition of 14.7 wt % Na.sub.2O, 29.8 wt % SiO.sub.2, and 55.5 wt % water.

[0182] A sodium hydroxide solution was prepared in the laboratory by dissolving sodium hydroxide pellets in water. To prepare the sodium hydroxide solution with a concentration of 12M, 480 grams of sodium hydroxide pellets supplied by Formosa Plastic Corporation, Taiwan were dissolved in 1 litre of distilled water. After cooling for 24 hours at room temperature, the sodium hydroxide solution was then mixed with the sodium silicate solution.

[0183] The mass ratio of sodium silicate to sodium hydroxide solution was 2.5. This provides a weight ratio of silicate ions and hydroxide ions of about 4:1.

[0184] The mixture of FA, GGBS, HMNS and carbon nanotubes was combined with the activator solution to form a paste in the amounts indicated in Table 13 below.

TABLE-US-00014 TABLE 13 Example Example Example Example Example Component 13 14 15 16 17 Class F FA (kg/m.sup.3) 1120 1117.76 1111.04 1104.32 1097.6 GGBS (kg/m.sup.3) 320 320 320 320 320 HMNS (kg/m.sup.3) 160 160 160 160 160 Carbon Nanotubes 0 2.24 8.96 15.68 22.4 (kg/m.sup.3) Carbon Nanotubes 0 0.2 0.8 1.4 2.0 (wt %) Na.sub.2SiO.sub.3 solution 71.42 71.42 71.42 71.42 71.42 (kg/m.sup.3) NaOH solution (12M) 28.57 28.57 28.57 28.57 28.57 (kg/m.sup.3) Na.sub.2SiO.sub.3/NaOH weight 2.5 2.5 2.5 2.5 2.5 ratio Solid/alkaline activator 2.0 2.0 2.0 2.0 2.0 weight ratio

[0185] To prepare the geopolymer composition, the mixture of FA, GGBS, HMNS and carbon nanotubes was placed in a mixing vessel. The activator solution was added to the dry mixture and the mixture stirred mechanically to form a uniform paste.

[0186] The geopolymer paste was placed in flat and cubic moulds and cured at room temperature (20+/−2° C.) at a relative humidity of 85 to 90%.

Example 18— Strength Tests of Geopolymer Composition with Carbon Nanotubes

[0187] The cured samples of Examples 13 to 17 were subjected to a quasi-static compression test to determine their compressive strength.

[0188] The compressive strength tests were performed after curing for 7 days using a universal testing machine (INSTRON 5582), under a load control regime with a loading rate of 0.3 kN/s in accordance with the ASTM C496 standard.

[0189] All tests were carried out in triplicate and average values were obtained and used as the results.

[0190] The compressive strength tests were conducted after heat treatment of the cured samples at different temperatures.

[0191] For the samples heated to 300° C., each sample was heated in an oven with the temperature increased at a rate of 6° C./min until the test temperature was reached. The sample was held at the test temperature for 2 hours. The sample was then allowed to cool to room temperature.

[0192] For the samples cooled to −36° C., each sample was immersed in liquid nitrogen at −96° C. until reaching the test temperature. The sample was then allowed to warm to room temperature.

[0193] The results of the compressive strength tests are summarised in Table 14 below.

TABLE-US-00015 TABLE 14 Carbon Nanotube Compressive Temperature Content Strength (° C.) (% wt) (MPa) Example 13 Room Temp. 0 18.0 −36 0 17.7 300 0 16.6 Example 14 Room Temp. 0.2 18.2 −36 0.2 17.8 300 0.2 15.7 Example 15 Room Temp. 0.8 22.0 −36 0.8 20.3 300 0.8 20.0 Example 16 Room Temp. 1.4 21.5 −36 1.4 20.7 300 1.4 20.1 Example 17 Room Temp. 2.0 21.2 −36 2.0 20.6 300 2.0 19.5

Example 19— Electrical Conductivity Tests of Geopolymer Composition with Carbon Nanotubes

[0194] The cured samples of Examples 13 to 17 were subjected to a test to determine their electrical conductivity.

[0195] Each sample was held between two opposing copper sheets. To improve the electrical contact between the copper sheets and the sample, the faces of the sample in contact with the sheets were painted with a high purity silver coating. The electrical conductivity between the cooper sheets was measured using a digital multi-meter (Keithly 6517B) at room temperature (20° C.+/−2° C.).

[0196] The in-plane electrical conductivity a of the samples was estimated using the following equation:

σ=L/RA

[0197] where:

[0198] L is the sample length (m);

[0199] R is the electrical resistance (Ω); and

[0200] A is the cross-sectional area of the sample (m.sup.2).

[0201] The results are summarised in Table 15 below.

TABLE-US-00016 TABLE 15 Carbon Nanotube Electrical Content Conductivity (% wt) (S/m*10.sup.−7) Example 13 0 1.1454 Example 14 0.2 2.3880 Example 15 0.8 8.0812 Example 16 1.4 11.11 Example 17 2.0 13.0655

Example 20— Electrical Heating Tests of Geopolymer Composition with Carbon Nanotubes

[0202] A cured sample of Example 17 was subjected to a test to determine their electrical heating properties.

[0203] The sample was held between two opposing copper sheets. To improve the electrical contact between the copper sheets and the sample, the faces of the sample in contact with the sheets were painted with a high purity silver coating. A current of 0.13 A was applied to the copper sheets. The temperature of the sample was measured over time.

[0204] The results are summarised in Table 16 below.

TABLE-US-00017 TABLE 16 Time (s) Temperature (° C.) 0 25 200 39 400 47 600 52 800 57 1000 59 1100 66

Example 21— Geopolymer Composition with Rubber Powder

[0205] A geopolymer paste composition was prepared from fly ash (FA), ground granulated blast furnace slag (GGBS), high-magnesium nickel slag (HMNS) and rubber powder, together with an alkaline activator, as follows:

[0206] Class F FA was obtained from Manjung power plant at Perak in Malaysia. The average particle size of the FA was about 18 μm. The specific surface area of the FA was around 1.29 m.sup.2/g.

[0207] GGBS was obtained from the steel plant at Penang in Malaysia. The average particle size of the GGBS was about 138 μm. The specific surface area of the GGBS was around 0.106 m.sup.2/g.

[0208] HMNS was obtained from the steel plant in Shaanxi Province, China. The average particle size of the HMNS was about 280 μm. The specific surface area of the HMNS was around 0.0536 m.sup.2/g.

[0209] The chemical compositions of the FA, GGBS and HMNS are summarised in Table 1 above, which were determined using X-ray fluorescence analysis.

[0210] Rubber powder was obtained from Crumb Rubber Ltd, Plymouth, UK. The rubber powder was manufactured from waste vehicle tyres and had an average particle size of less than 8 μm (ultra-fine rubber powder).

[0211] The FA, GGBS, HMNS and rubber powder was combined and mixed to form a homogeneous dry mixture.

[0212] An alkaline activator was prepared as follows:

[0213] A sodium silicate solution was obtained from South Pacific Chemicals Industries (SPCI) Ltd in Malaysia, with the chemical composition of 14.7 wt % Na.sub.2O, 29.8 wt % SiO.sub.2, and 55.5 wt % water.

[0214] A sodium hydroxide solution was prepared in the laboratory by dissolving sodium hydroxide pellets in water. To prepare the sodium hydroxide solution with a concentration of 12M, 480 grams of sodium hydroxide pellets supplied by Formosa Plastic Corporation, Taiwan were dissolved in 1 litre of distilled water. After cooling for 24 hours at room temperature, the sodium hydroxide solution was then mixed with the sodium silicate solution.

[0215] The mass ratio of sodium silicate to sodium hydroxide solution was 2.5. This provides a weight ratio of silicate ions and hydroxide ions of about 4:1.

[0216] The mixture of FA, GGBS, HMNS and rubber powder was combined with the activator solution in the amounts indicated in Table 17 below.

TABLE-US-00018 TABLE 17 Component Example 21 Class F FA (kg/m.sup.3) 864 GGBS (kg/m.sup.3) 320 HMNS (kg/m.sup.3) 160 Rubber Powder (kg/m.sup.3) 96 Rubber Powder (wt %) 10 Na.sub.2SiO.sub.3 solution (kg/m.sup.3) 71.42 NaOH solution (12M) (kg/m.sup.3) 28.57 Na.sub.2SiO.sub.3/NaOH weight ratio 2.5 Solid/alkaline activator weight ratio 2.0

[0217] To prepare the geopolymer composition, the mixture of FA, GGBS, HMNS and rubber powder was placed in a mixing vessel. The activator solution was added to the dry mixture and the mixture stirred mechanically to form a uniform paste.

[0218] The geopolymer paste was placed in cubic moulds and cured at room temperature (20+/−2° C.) at a relative humidity of 85 to 90%.

Example 22— Strength Tests of Geopolymer Composition with Rubber Powder

[0219] The cured sample of Example 21 was subjected to a test to determine its compressive strength.

[0220] The compressive strength tests were performed after curing for 28 days using a universal testing machine, under a load control regime with a loading rate of 0.3 kN/s in accordance with the ASTM C496 standard.

[0221] All tests were carried out in triplicate and average values were obtained and used as the results.

[0222] The cured geopolymer composition comprising rubber powder as a filler exhibited a compressive strength at room temperature of 44.25 MPa.

Example 23— Geopolymer Composition with Sugar Powder Waste

[0223] A geopolymer composition was prepared from fly ash (FA), ground granulated blast furnace slag (GGBS), high-magnesium nickel slag (HMNS) and sugar powder waste, together with an alkaline activator, as follows:

[0224] Class F FA was obtained from Manjung power plant at Perak in Malaysia. The average particle size of the FA was about 18 μm. The specific surface area of the FA was around 1.29 m.sup.2/g.

[0225] GGBS was obtained from the steel plant at Penang in Malaysia. The average particle size of the GGBS was about 138 μm. The specific surface area of the GGBS was around 0.106 m.sup.2/g.

[0226] HMNS was obtained from the steel plant in Shaanxi Province, China. The average particle size of the HMNS was about 280 μm. The specific surface area of the HMNS was around 0.0536 m.sup.2/g.

[0227] The chemical compositions of the FA, GGBS and HMNS are summarised in Table 1 above, which were determined using X-ray fluorescence analysis.

[0228] Sugar powder waste was obtained from Group Cevital Agro-Industrie Spa, Algeria. The sugar powder had an average particle size of less than 30 μm.

[0229] The FA, GGBS, HMNS and sugar powder waste was combined and mixed to form a homogeneous dry mixture.

[0230] An alkaline activator was prepared as follows:

[0231] A sodium silicate solution was obtained from South Pacific Chemicals Industries (SPCI) Ltd in Malaysia, with the chemical composition of 14.7 wt % Na.sub.2O, 29.8 wt % SiO.sub.2, and 55.5 wt % water.

[0232] A sodium hydroxide solution was prepared in the laboratory by dissolving sodium hydroxide pellets in water. To prepare the sodium hydroxide solution with a concentration of 12M, 480 grams of sodium hydroxide pellets supplied by Formosa Plastic Corporation, Taiwan were dissolved in 1 litre of distilled water. After cooling for 24 hours at room temperature, the sodium hydroxide solution was then mixed with the sodium silicate solution.

[0233] The mass ratio of sodium silicate to sodium hydroxide solution was 2.5. This provides a weight ratio of silicate ions and hydroxide ions of about 4:1.

[0234] The mixture of FA, GGBS, HMNS and sugar powder waste was combined with the activator solution in the amounts indicated in Table 18 below.

TABLE-US-00019 TABLE 18 Component Example 23 Class F FA (kg/m.sup.3) 864 GGBS (kg/m.sup.3) 320 HMNS (kg/m.sup.3) 160 Sugar Powder Waste (kg/m.sup.3) 96 Sugar Powder Waste (wt %) 10 Na.sub.2SiO.sub.3 solution (kg/m.sup.3) 71.42 NaOH solution (12M) (kg/m.sup.3) 28.57 Na.sub.2SiO.sub.3/NaOH weight ratio 2.5 Solid/alkaline activator weight ratio 2.0

[0235] To prepare the geopolymer composition, the mixture of FA, GGBS, HMNS and sugar powder waste was placed in a mixing vessel. The activator solution was added to the dry mixture and the mixture stirred to form a uniform paste.

[0236] The geopolymer paste was placed in cubic moulds and cured at room temperature (20+/−2° C.) at a relative humidity of 85 to 90%.

Example 24— Strength Tests of Geopolymer Composition with Sugar Powder Waste

[0237] The cured sample of Example 23 was subjected to a test to determine its compressive strength.

[0238] The compressive strength tests were performed after curing for 7 days using a universal testing machine, under a load control regime with a loading rate of 0.3 kN/s in accordance with the ASTM C496 standard.

[0239] All tests were carried out in triplicate and average values were obtained and used as the results.

[0240] The cured geopolymer composition comprising sugar powder waste as a filler exhibited a compressive strength at room temperature of 18 MPa.