CEMENTITIOUS BINDERS FOR GEOPOLYMER, GEOPOLYMERS, AND USES THEREOF

Abstract

Binders for geopolymers, which include: a) not less than 30 w % of a mixture of at least two chemically different aluminosilicates, b) not less than 20 w % of Ordinary Portland cement, and c) 8-20 w % of a mixture of calcium sulfoaluminate cement or calcium aluminate cement with a source of calcium sulfate, wherein in the mixture the weight ratio of calcium sulfate to calcium sulfoaluminate and/or calcium aluminate is between 0.08-1.5, preferably 0.3-1.1, more preferably 0.6-1.1. Also, geopolymers using such binders as well as their use in various construction methods.

Claims

1. A cementitious binder for geopolymers, the cementitious binder comprising in each case relative to the total dry weight of cementitious binder a) not less than 30 w % of a mixture of at least two chemically different aluminosilicates, b) not less than 20 w % of Ordinary Portland cement, and c) 8-20 w % of a mixture of calcium sulfoaluminate cement or calcium aluminate cement with a source of calcium sulfate, wherein in the mixture the weight ratio of calcium sulfate to calcium sulfoaluminate and/or calcium aluminate is between 0.08-1.5.

2. A cementitious binder as claimed in claim 1, wherein the at least two chemically different aluminosilicates are selected from steelmaking slag and fly ash of class F according to ASTM C618.

3. A cementitious binder as claimed in claim 1, wherein a first aluminosilicate is steelmaking slag and further aluminosilicates are selected from fly ash of class F according to ASTM C618 and/or calcined clay.

4. A cementitious binder as claimed in claim 1, wherein two chemically different aluminosilicates are present selected from steelmaking slag and a clay mineral.

5. A cementitious binder as claimed in claim 1, wherein the cementitious binder additionally comprises 5-15 w % of silica fume, relative to the total dry weight of cementitious binder.

6. A cementitious binder as claimed in claim 1, wherein a weight ratio of Ordinary Portland Cement to the sum of the at least two thermally activated aluminosilicate is between 0.1-2.

7. A cementitious binder as claimed in claim 1, wherein silica fume, calcined clay, and fly ash of class F according to ASTM C618 are present and wherein a weight ratio of the sum of silica fume and calcined clay to fly ash is between 0.1-0.5.

8. A cementitious binder as claimed in claim 2, wherein steelmaking slag is ground granulated blast furnace slag.

9. A cementitious binder as claimed in claim 1, wherein the source of calcium sulfate is anhydrite.

10. A geopolymer composition comprising a) a cementitious binder as claimed in claim 1, b) aggregates and/or fillers, c) optionally further additives.

11. A method for the repair of concrete or mortar structures or of masonry, the method comprising the steps of a) providing a cementitious binder according to claim 1 or a geopolymer composition comprising the cementitious binder, aggregates and/or fillers, and optionally further additives, b) mixing the cementitious binder or the geopolymer composition provided in step a) with water, c) applying the mixture obtained in step b) to the surface of a hardened concrete or mortar structure, and d) optionally hardening the applied mixture.

12. A method for the protection of a structure, the method comprising the steps of a) providing a cementitious binder according to claim 1 or a geopolymer composition comprising the cementitious binder, aggregates and/or fillers, and optionally further additives, b) mixing the cementitious binder or the geopolymer composition provided in step a) with water, c) applying the mixture obtained in step b) to the surface of the hardened structure, and d) optionally hardening the applied mixture.

13. A method for the waterproofing of a structure, the method comprising the steps of a) providing a cementitious binder according to claim 1 or a geopolymer composition comprising the cementitious binder, aggregates and/or fillers, and optionally further additives, b) mixing the cementitious binder or the geopolymer composition provided in step a) with water, c) applying the mixture obtained in step b) to the surface of the hardened structure, and d) optionally hardening the applied mixture.

14. A method for the 3D printing of a mortar composition, the method comprising the steps of a) providing a cementitious binder according to claim 1 or a geopolymer composition comprising the cementitious binder, aggregates and/or fillers, and optionally further additives, b) mixing the cementitious binder or the geopolymer composition provided in step a) with water, c) optionally conveying the mixture obtained in step b) to a print head, c) applying the mixture obtained in step b) from a print head layer by layer to form a 3 dimensional object, and d) optionally hardening the 3 dimensional object.

15. A method for shotcreting, the method comprising the steps of a) providing a cementitious binder according to claim 1 or a geopolymer composition comprising the cementitious binder, aggregates and/or fillers, and optionally further additives, b) mixing the cementitious binder or the geopolymer composition provided in step a) with water, c) conveying the mixture obtained in step b) to a gun, d) optionally intermixing an additional accelerator to the mixture obtained in step b), c) spraying the mixture from the gun into a cavity and/or onto a surface, and d) optionally hardening the applied mixture.

Description

FIGURES

[0153] FIG. 1 System for 3D printing of a mortar composition.

[0154] 1 System for 3D printing of a mortar composition [0155] 2 Movement device [0156] 2.1 Movable arm [0157] 3 Print head [0158] 3.1 Passage [0159] 4 Outlet [0160] 5 Inlet nozzle [0161] 6 Static mixer [0162] 7 Deaerating device [0163] 8 Measuring unit [0164] 9 Feed device [0165] 10 Mixing device [0166] 10.1-10.3 Inlets [0167] 11.1-11.4 Containers [0168] 12 Flexible line [0169] 13 Measuring unit [0170] 14 Control unit [0171] 15a-15h Control line, data line

EXAMPLES

[0172] The following table 1 gives an overview of the chemical composition of some of the raw materials used.

TABLE-US-00001 TABLE 1 chemical composition and fineness of fly ash, ground granulated blast furnace slag, metakaolin, and silica fume used Fine- SiO.sub.2* Al.sub.2O.sub.3* Fe.sub.2O.sub.3* CaO* MgO* SO.sub.3* ness** Class F fly 51.9 23.3 14.8 2.3 0.9 0.53 20.8% ash (FA) GGBS 36.5 10.9 0.6 38.8 11.3 2.3 0.9% Metakaolin 50.0 41.3 1.7 0.2 0.2 0.05 1.8% (MK) Silica 95.9 0.1 0.1 0.5 0.2 0.25 2.0% Fume (SF) *determined by XRF as described in EN 196-2:2013 **amount retained on #325 sieve

[0173] White Ordinary Portland Cement Type I (w-PC) with a Blaine fineness of 4280 cm2/g from the company Royal White Cement was used.

[0174] Calcium sulfoaluminate cement (CSA) with an amount of 69.4 w % C.sub.4A.sub.3$, 2.6 w % anhydrite, and <25 w % C.sub.2S was used.

[0175] Calcium sulfate used was anhydrite.

[0176] Sand used is a mixture of silica sand with particle size 0.1-2.5 mm.

[0177] Fine filer used was ground feldspar with an average particle size of 45 microns. Polycarboxylate ether (PCE) of type Melflux 6681 supplied by Azelis Americas Inc was used as an additive.

Example 1Geopolymer Tests

[0178] To make cementitious binders for geopolymer or geopolymer formulations, the dry ingredients were weighed into a Hobart mixer in the amounts indicated in below tables 2-5 and mixed for 3 minutes at 23 C. and 50% relative humidity. Water was then added to realize a weight ratio of cementitious binder to water (ratio w/b) as indicated in below tables 2-5 and mixing continued for another 3 minutes. Test specimen were cast directly from the resulting geopolymer compositions. Measurements were performed as follows.

[0179] Shrinkage was measured according to standard ASTM C157/C157-M08 after 24 hours curing at 23 C./50% r.h. A shrinkage of 1500 m/m or less was desired. Expansion (indicated by positive values in below tables 2-5) is preferable over shrinkage within the present context.

[0180] Compressive strength (termed C.S. in below tables 2-5) was determined according to standard ASTM C109/C109M using cylinders of 25.4 mm height and 25.4 mm diameter. Compressive strength was measured after curing the test specimen for 7 d at 23 C./90% r.h. and subsequently for 7 d immersed in tap water.

[0181] Acid resistance (termed A.R. in below tables 2-5) was measured by comparison of compressive strength of test specimen. For the comparison, a first specimen from each mix was prepared according to ASTM C109/C109M as described above. A second test specimen from each mix was prepared according to the same procedure, but instead of curing for 7 d at 23 C./90% r.h. and subsequently for 7 d immersed in tap water, this second test specimen was cured for 7 d at 23 C./90% r.h. and subsequently for 7 d immersed in 0.5 M sulfuric acid. The difference in compressive strength between the two respective test specimen was calculated and is reported below as a difference in % (a negative value indicating loss of compressive strength during storage in acid, a positive value indicating gain of compressive strength during acid storage).

[0182] For ease of reference, the calculated weight ratio of calcium sulfate to calcium sulfoaluminate (ratio C$: CSA) is given in the below table 2-5 for each mixture.

[0183] Compositions C-1 to C-9 are not according to the present invention and are included for comparative purposes. Compositions G-1 to G-13 are according to the present invention.

TABLE-US-00002 TABLE 2 comparative mixtures C-1 to C-8 and results C-1 C-2 C-3 C-4 C-6 C-7 C-8 FA [g] 17 11 25 13 GGBS [g] 13 15 25 12 w-PC [g] 39 22 14 10 10 10 MK [g] 15 CSA [g] 4 4 5.6 CaSO.sub.4 [g] 1.7 1.7 Sand [g] 60 59 59 57.9 57.2 57.2 57.3 Filler [g] 2 2 2 2 2 2 PCE [g] 0.1 0.1 0.1 0.1 ratio C$: CSA n.d. n.d. n.d. n.d. 0.65 0.65 0.04 ratio w/b 0.41* 0.41 0.41 0.41 0.39 0.39 0.39 Shrinkage [m/m] 6200 n.a. n.a. 1700 n.a. n.a. 900 C.S. [psi] 4099 5114 5978 5457 2286 7288 n.a. A.R. [%] +1.5 32.1 41.9 42.3 15.6 21.7 n.a. *used 23 parts potassium silicate solutiuon (47% solids content) n.d.: not determined n.a.: not available

[0184] It can be seen from the above examples, that a geopolymer composition according to the teachings of Davidovits (C-1) does result in good strength and acid resistance but also shows very high shrinkage. The use of Portland cement based binders decreased the shrinkage, but also decreased the acid resistance (examples C-2 to C-4). The combined use of Portland cement, CSA, and calcium sulfate without aluminosilicate also led to acceptable shrinkage but low acid resistance. Interestingly, the use of only one aluminosilicate with the Portland cement, CSA, calcium sulfate based binder was not sufficient to yield high strength and at the same time increase the acid resistance (cf examples C-6 and C-7).

[0185] The use of CSA alone, without the anhydride, did lead to low shrinkage but not to the desired acid resistance.

TABLE-US-00003 TABLE 3 geopolymer mixtures G-1 to G-6 and results G-1 G-2 G-3 G-4 G-5 G-6 FA [g] 11 13 13 13 13 10 GGBS [g] 14 12 12 12 12 12 w-PC [g] 9 10 10 10 10 10 MK [g] 1.5 SF [g] 1 CSA [g] 3.6 5.9 4.8 4 4.4 4 CaSO.sub.4 [g] 1.6 1.3 0.8 1.5 1.2 1.7 Sand [g] 58.7 55.7 57.3 57.4 57.4 57.7 Filler [g] 2 2 2 2 2 2 PCE [g] 0.1 0.1 0.1 0.1 0.1 0.1 ratio C$: 0.68 0.36 0.28 0.58 0.43 0.65 CSA ratio w/b 0.39 0.39 0.39 0.39 0.39 0.39 Shrinkage n.a. 1050 1400 +800 n.a. n.a. [m/m] C.S. [psi] 4710 n.a. n.a. 5537 5344 5905 A.R. [%] 13.8 n.a. n.a. 20.9 16.7 n.a. n.a.: not available

[0186] It can be seen from the results of table 3, that it is the combination of at least two chemically different aluminosilicates in combination with a binder based on Portland cement, CSA, and calcium sulfate, that increase the acid resistance and yet shows low shrinkage.

[0187] Also, an increase in the ratio of weight ratio of calcium sulfate to calcium sulfoaluminate the shrinkage is improved (examples G-2 to G-4).

[0188] The partial replacement of fly ash by metakaolin and silica fume additionally increased the acid resistance.

TABLE-US-00004 TABLE 4 geopolymer mixtures G-7 to G-9 and results G-7 G-8 G-9 G-10 FA [g] 13 13 13 14 GGBS [g] 12 12 12 9 w-PC [g] 10 10 10 11 CSA [g] 4 4 4 4.3 CaSO.sub.4 [g] 1.3 1.5 1.7 1.9 Sand [g] 55.6 57.4 57.2 57.7 Filler [g] 2 2 2 2 PCE [g] 0.1 0.1 0.1 0.1 ratio C$: CSA 0.51 0.58 0.65 0.67 ratio w/b 0.37 0.37 0.37 0.39 Shrinkage 850 800 +100 n.a. [m/m] C.S. [psi] 4425 4305 3805 4017 A.R. [%] n.a. n.a. n.a. 4.9 n.a.: not available

[0189] From the results of above table 4 it can be seen that with increasing weight ratio of calcium sulfate to calcium sulfoaluminate the shrinkage is improved (examples G-7 to G-9).

[0190] Also, from a comparison of results from tables 3 and 4 (cf examples G-1 and G-10) it can be seen that an increase in the weight ratio of GGBS to fly ash leads to increased strength but lower acid resistance. However, it has to be mentioned that acid resistance was acceptable in both these examples.

TABLE-US-00005 TABLE 5 comparative mixture C-9 and geopolymer mixtures G-10 to G-13 and results C-9 G-10 G-11 G-12 G-13 FA [g] 3.2 5.6 GGBS [g] 11.2 8 8 5.6 7.4 MK [g] 3.2 2.9 w-PC [g] 8.7 8.7 8.7 8.7 8.7 SF [g] 1 CSA [g] 1.2 1.2 1.2 1.2 1.2 CaSO.sub.4 [g] 1.2 1.2 1.2 1.2 1.2 Sand [g] 75 75 75 75 75 Filler [g] 2.3 2.3 2.3 2.3 2.3 PCE [g] 0.1 0.1 0.1 0.1 0.1 ratio C$: CSA 1.0 1.0 1.0 1.0 1.0 ratio w/b 0.15 0.15 0.15 0.15 0.15 Shrinkage 1500 300 164 107 156 [m/m] C.S. [psi] 2102 3686 3381 3160 4072 A.R. [%] n.a. +5.9 18.1 10.9 +1.3 n.a.: not available

[0191] It can be seen from the results in table 5 that compositions according to the invention have significantly lower shrinkage and higher compressive strength as compared to a reference. A binder having a combination of GGBS and fly ash led to lower shrinkage but also slightly lower compressive strength as compared to a binder having a combination of GGBS and metakaolin (cf examples G-10 and G-11). The addition of additional silica fume can further reduce the shrinkage and increase the compressive strength and acid resistance (cf examples G-13 and G-10). A balanced ratio of GGBS to fly ash can also further reduce the shrinkage and improve the acid resistance (cf examples G11 and G-12).

Example 23D Printing

[0192] A geopolymer composition was 3D printed with a system as described in FIG. 1. Layers of material having a width of 5 cm and a height of 0.5 cm were applied. The geopolymer composition consisted of (raw materials as described above): 16.3 w % of GGBS, 9.4 w % of w-PC, 2 w % of MK, 5.8 w % of CSA, 0.5 w % of CaSO.sub.4, 43 w % of sand, 16.7 w % of ground CaCO.sub.3 (D50: appr. 30 m), 5 w % of CaCO.sub.3 fine filler (D50: 0.8 m), 0.2 w % of PCE, and 1.1 w % additives (mixture of diutan gum and modified cellulose thickener, gluconate, and aluminium sulfate). A weight ratio of water to powder of 0.16 was used.

[0193] Visual inspection showed good printability evidenced by all of the following: individual layers show very limited sagging and no flow, adhesion between layers is good, a minimum of three layers could be applied on top of each other. Print time to build an object of 20 cm height was 13 min. Initial hose pressure was 200 psi, final hose pressure was 260 psi. Thus, a geopolymer composition according to the present invention showed smooth extrusion and excellent finish.

[0194] The 24 hour and 28 day strength of the printed object was high. Surprisingly, it was higher as compared to an object printed with conventional cementitious 3D printing inks.