IMPROVED GEOPOLYMER CEMENT

Abstract

The present invention provides a geopolymer cement, comprising: a geopolymer binder; and a setting control composition comprising: a viscosity control agent, a polymeric binder, and a retarding additive. The invention also relates to a geopolymer concrete comprising the geopolymer cement of the invention and aggregate material. The invention further relates to a method for controlling open time in a geopolymer composition, wherein a sufficient quantity of the setting control composition is added such that the open time is between 30 and 120 minutes. The present invention provides particular uses in construction of walls, flooring, and roofing, especially lightweight prefabricated panels intended to be used as structural, insulating or cladding elements.

Claims

1. A geopolymer cement, comprising: a geopolymer binder; and a setting control composition comprising: a viscosity control agent, a polymeric binder, and a retarding additive.

2. A geopolymer cement according to claim 1 wherein the geopolymer binder comprises an aluminosilicate material and an activator.

3. A geopolymer cement according to claim 1 wherein the aluminosilicate material is fly ash and/or slag.

4. A geopolymer cement according to claim 1 wherein the geopolymer binder is present at a concentration of 60 to 99 wt %, preferably 95 wt %.

5. A geopolymer cement according to claim 2 wherein the activator is an alkaline silicate solution.

6. A geopolymer cement according to claim 2 wherein the activator is a mixture of sodium silicate and sodium carbonate.

7. A geopolymer cement according to claim 1 wherein the viscosity control agent is a cellulose based organic polymer selected from the group consisting of: include methylcellulose (MC), methylhydroxyethylcellulose (MHEC), methylhydroxypropylcellulose (MHPC), hydroxyethylcellulose (HEC), ethylhydroxyethylcellulose (EHEC), methylethylhydroxyethylcellulose (MEHEC), hydrophobically modified ethylhydroxyethylcelluloses (HMEHEC), hydrophobically modified hydroxyethylcelluloses (HMHEC), sulfoethyl methylhydroxyethylcelluloses (SEMHEC), sulfoethyl methylhydroxypropylcelluloses (SEMHPC), sulfoethyl hydroxyethylcelluloses (SEHEC), hydroxypropyl-cellulose (HPC), hydroxypropylmethyl-cellulose (HPMC), methyl-cellulose (MC), ethyl-cellulose (EC), methylethyl-cellulose (MEC), carboxymethyl-cellulose (CMC), carboxymethyl-ethyl-cellulose (CMEC), and carboxymethylhydroxyethyl-cellulose (CMREC).

8. A geopolymer cement according claim 1 wherein the viscosity control agent is present at a concentration of 0.1 to 3.0 wt %, preferably 0.7 wt %.

9. A geopolymer cement according to claim 1 wherein the polymeric binder is a redispersible polymer powder selected from vinyl acetate ethylene (VAE) emulsions.

10. A geopolymer cement according to claim 1 wherein the polymeric binder is present at a concentration of 0.1 to 1.5 wt %.

11. A geopolymer cement according to claim 1 wherein the retarding additive is borate.

12. (canceled)

13. A geopolymer cement according to claim 1 wherein the geopolymer cement further comprises other additives selected from the group consisting of: set accelerating agents, air-entraining agents, foaming agents, wetting agents, shrinkage control agents, efflorescence control agents, colouring agents, corrosion control agents, alkali-silica reaction reducing admixtures, discrete reinforcing fibers, and/or other aggregates, lightweight fillers, mineral fillers.

14-16. (canceled)

17. A geopolymer concrete, comprising: a geopolymer cement according to claim 1, water, and aggregate material, wherein the concrete has a water to cement ratio of between 0.15 to 0.25.

18. A geopolymer concrete according to claim 17 wherein the water:cement ratio is 0.20.

19. A geopolymer concrete according to claim 17 wherein the water:cement ratio is 0.19 or 0.21.

20. A method of making a geopolymer cement, comprising: combining a geopolymer binder with a setting control composition, the setting control composition comprising: a viscosity control agent, a polymeric binder, and a retarding additive.

21. A method of making a geopolymer concrete, comprising: combining a solid geopolymer cement according to claim 1, aggregate material, and water, wherein the water to cement ratio is between 0.15 to 0.25.

22. A method for controlling open time in a geopolymer composition, the method comprising: combining a geopolymer binder with a setting control composition to provide said geopolymer composition, the setting control composition comprising: a viscosity control agent, a polymeric binder, and a retarding additive, and adding water to the geopolymer composition such that the water to cement ratio is between 0.15 to 0.25, wherein a sufficient quantity of the setting control composition is added such that the open time is between 30 and 120 minutes.

23. A method for controlling open time in a geopolymer composition, the method comprising: using a setting control composition comprising: a viscosity control agent, a polymeric binder, and a retarding additive.

24-25. (canceled)

Description

DETAILED DESCRIPTION

[0129] The skilled addressee will understand that the invention comprises the embodiments and features disclosed herein as well as all combinations and/or permutations of the disclosed embodiments and features.

EXAMPLES

[0130] The present invention will now be described with reference to the following examples which should be considered in all respects as illustrative and non-restrictive.

[0131] Granulated blast furnace slag powder used in the following examples comprised the following properties. The particle size was 320 mesh (44 micrometres).

TABLE-US-00002 specific 7 days surface activity Ignition Liquidity Water Density area index loss Chloride ratio Content (g/cm.sup.3) (m.sup.2/kg) (%) (%) (%) (%) (%) 2.9 418 80 0.23 0.047 98 0.4

[0132] The composition of the borate was ≥99.99 wt % Na.sub.2B.sub.4O.sub.7.5H.sub.2O, and the composition of the sodium carbonate was ≥99.2 Na.sub.2CO.sub.2. Sodium metasilicate pentahydrate was used, and comprised 28-30 wt % sodium oxide (Na.sub.2O), 27-29 wt % silica (SiO.sub.2), and had a particle size of 16-60 mesh.

Example 1: Prior Art Geopolymer Cement with Borate Retarder

[0133] In this example, a prior art geopolymer cement was formulated, comprising: slag, sodium carbonate, and sodium metasilicate, as per the table below. Despite borate retarder being added, the cement gelled and set during the mixing process, i.e. an open time of less than 10 minutes.

TABLE-US-00003 Component wt % of solids Slag 100% 84.7 Sodium carbonate 8% of slag 6.8 Sodium metasilicate 8% of slag 6.8 Borate 2% of slag 1.7 Water 20% of pre-mix load Water:cement* ratio 0.200 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate

Example 2: Prior Art Geopolymer Cement with Borate Retarder and Increased Water

[0134] In this example, the same composition as in Example 1 was prepared, but with additional water content, as per the table below. The incorporation of additional water was expected to increase open time. Some open time was observed. However, whilst the formula completed mixing it only flowed for 15 minutes. In this case, whilst the final properties of the cured material were not measured, it would be expected that the compressive strength would be relatively reduced, as the binder was overdosed with water.

TABLE-US-00004 Component wt % of solids Slag 100% 84.7 Sodium carbonate 8% of slag 6.8 Sodium metasilicate 8% of slag 6.8 Borate 2% of slag 1.7 Water 30% of pre-mix load Water:cement* ratio 0.300 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate

[0135] Both of the open times achieved for Examples 1 and 2 were unacceptable by industry standards, making theses compositions less than ideal for practical industry applications.

Example 3: Prior Art Geopolymer Cement with Various Concentrations of Borate Retarder

[0136] In this example, the same composition as in Example 2 was prepared with additional borate content from 2% up to 5% in 0.25% increments, as per the table below. However, it was observed during these experiments that whilst borate had an impact on the open time, its usefulness as a retarder seemed to plateau at 2.75% of the slag content. No additional open time was achieved using borate concentrations from 2.75% to 5%. Although open times of 20 to 25 minutes were achieved, this is still not sufficient to make the formula usable in practical industry applications. Overdosing with water is likely contributing to the increased open time, but at the expense of reduced compressive strength.

TABLE-US-00005 wt % of wt % of Component solids solids Slag 100% 84.7 100% 82.6 Sodium carbonate 8% of slag 6.8 8% of slag 6.6 Sodium metasilicate 8% of slag 6.8 8% of slag 6.6 Borate 2% of slag 1.7 5% of slag 4.1 Water 30% of pre-mix 30% of pre-mix load load Water:cement* ratio 0.300 0.300 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate

Example 4: Prior Art Geopolymer Cement with HPMC

[0137] In this example, the same composition as in Example 2 was prepared with HPMC as replacement for borate, as per the table below.

TABLE-US-00006 wt % of wt % of Component solids solids Slag 100% 86.2 100% 83.3 Sodium carbonate 8% of slag 6.9 8% of slag 6.7 Sodium metasilicate 8% of slag 6.9 8% of slag 6.7 HPMC 0.05% of slag 0.04 4% of slag 3.3 Water 30% of pre-mix 30% of pre-mix load load Water:cement* ratio 0.300 0.300 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + HPMC

[0138] It was observed that, surprisingly, HPMC provided more open time, of around 40 minutes, but only with loads of 3.5% to 4%. This is still not sufficient to make the composition usable in practical industry applications. Additionally, the introduction of HPMC in these concentrations not only added considerable cost to the formulation, it created severe cracking in the cured geopolymer material. Overdosing with water is likely contributing to the increased open time, but at the expense of reduced compressive strength.

Example 5: Prior Art Geopolymer Cement with HPMC and Borate

[0139] This example was prepared by combining HPMC and borate, as per the table below.

TABLE-US-00007 Component wt % of solids Slag 100% 83.9 Sodium carbonate 8% of slag 6.7 Sodium metasilicate 8% of slag 6.7 Borate 2.75% of slag 2.3 HPMC 0.5% of slag 0.42 Water 30% of pre-mix load Water:cement* ratio 0.300 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate + HPMC

[0140] It was observed that during this experiment that HPMC and borate provided an acceptable open time of around 60 minutes. This was surprising given that the HPMC concentration is only about 10% that used in Example 4, suggesting a synergy between these components of the formulation. A further experiment was undertaken whereby the HPMC concentration was increased by only 0.25% (to a total of 0.75%), and surprisingly the open time increased to around 90 minutes. However, the cracking remained an issue, although was significantly better than Example 4. To attempt to remedy the cracking issue, a further experiment was undertaken with a lower water concentration.

Example 6: Prior Art Geopolymer Cement with HPMC/Borate and Lower Water Content

[0141] In this example, the same composition as in Example 5 with additional HPMC at 0.75% was prepared but with lower water content, as per the table below.

TABLE-US-00008 Component wt % of solids Slag 100% 83.7 Sodium carbonate 8% of slag 6.7 Sodium metasilicate 8% of slag 6.7 Borate 2.75% of slag 2.3 HPMC 0.75% of slag 0.63 Water 20% of pre-mix load Water:cement* ratio 0.200 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate + HPMC

[0142] It was observed that the open time did not decrease with the lower water load, remaining at around between 60-90 minutes. However, the cracking did not improve either. The reduction in water content did not affect the open time, which was a surprising outcome, but was expected to lead to better ultimate compressive strength in the final cured material.

Example 7: Prior Art Geopolymer Cement with HPMC/Borate and Polymeric Binder

[0143] In this example, the same composition as in Example 6 was prepared but with the introduction of the polymeric binder in the form of VAE.

TABLE-US-00009 Component wt % of solids Slag 100% 83.7 Sodium carbonate 8% of slag 6.7 Sodium metasilicate 8% of slag 6.7 Borate 2.75% of slag 2.3 HPMC 0.75% of slag 0.63 VAE 0.25% of slag 0.2 Water 20% of pre-mix load Water:cement* ratio 0.200 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate + HPMC + VAE

[0144] The addition of a very small content of VAE had no adverse impact on open time, which remained in a similar range as Example 6. The addition of VAE, did, however reduce the cracking somewhat, and did so at relatively small concentrations. This was surprising, because it was expected that significantly greater concentration of polymeric binder would be required to address the cracking issue that was present in the Example 5 composition.

Example 8: Prior Art Geopolymer Cement with HPMC/Borate and Increased Polymeric Binder

[0145] In this example, the same composition as in Example 7 was prepared but with increased polymeric binder content.

TABLE-US-00010 Component wt % of solids Slag 100% 83.3 Sodium carbonate 8% of slag 6.7 Sodium metasilicate 8% of slag 6.7 Borate 2.75% of slag 2.3 HPMC 0.75% of slag 0.63 VAE 0.50% of slag 0.4 Water 20% of pre-mix load Water:cement* ratio 0.200 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate + HPMC + VAE

[0146] The addition of an additional 0.25% VAE (over Example 7) had no adverse impact on open time, and surprisingly the cracking disappeared completely.

Example 9a and 9b: Investigation of Increased Activator Content

[0147] The following examples were prepared with increased activator content, and varying water loads as per the following tables. The purpose of these experiments was to investigate how overdosing the premix with additional activator (sodium carbonate and sodium metasilicate) and water loads, while removing the HPMC and VAE may affect open time and mechanical properties.

Example 9a—Same as example 8 with increased activators

TABLE-US-00011 Component wt % of solids Slag 100% 80.6 Sodium carbonate 10% of slag 8.1 Sodium metasilicate 10% of slag 8.1 Borate 2.75% of slag 2.2 HPMC 0.75% of slag 0.60 VAE 0.50% of slag 0.4 Water 20% of premix load Water:cement* ratio 0.200 *cement = slag + sodium carbonate + sodium metasilicate
Example 9b—Same as Example 8 with increased activators, without HPMC and VEA Component wt % of solids

TABLE-US-00012 Component wt % of solids Slag 100% 80.6 Sodium carbonate 10% of slag 8.1 Sodium metasilicate 10% of slag 8.1 Borate 2.75% of slag 2.2 HPMC Nil VAE Nil Water 30% of premix load Water:cement* ratio 0.200 *cement = slag + sodium carbonate + sodium metasilicate

[0148] Test samples of the composition set out in the tables above were allowed to cure for 28 days with compressive testing done after 1 day, 7 days, and 28 days. (see table below)

TABLE-US-00013 Experiment Experiment 9a Sam- 9a Sam- 9a Sam- 9b Sample 9a Sample 1 ple 2 ple 3 ple 4 1 day (MPa) 15.2 41.8 43.9 43.6 42.8 7 day (MPa) 31.2 87.2 86.2 89.2 86.4 28 day (MPa)  43.7 103.3 93.2 108.4 101.8

[0149] Interestingly, Experiment 9b's strength after 1 day at 15.2 MPa, is indicative of a poor open time. If an acceptable open time was achieved that figure should be much lower, and in the order of 8-9 MPa. Secondly, Experiment 9b's 28-day strength is not very high, considering the increase in activators from 8% to 10% (for each of the sodium carbonate and the sodium metasilicate). These figures indicate that the additional 10% water load has adversely affected the final strength of Experiment 9b, while still not providing an exceptionable open time.

[0150] Note that Experiment 9a's strength after 1 day at 43 MPa is more than double that of Experiment 9b's but still indicative of a poor open time. But the strength growth over the 28 days culminating at around 100 MPa is an exceptional outcome.

Example 10: Investigation of Reduction in Activator Concentration

[0151] In this example, the same composition as in Example 8 was prepared and the compressive strength measured, as per the following tables.

TABLE-US-00014 Component wt % of solids Slag 100% 83.3 Sodium carbonate 8% of slag 6.7 Sodium metasilicate 8% of slag 6.7 Borate 2.75% of slag 2.3 HPMC 0.75% of slag 0.63 VAE 0.50% of slag 0.4 Water 20% of pre-mix load Water:cement* ratio 0.200 *cement (pre-mix load) = weight of slag + sodium carbonate + sodium metasilicate + borate + HPMC + VAE

[0152] It was observed that the open time was in the order of 24 hours and the set material had little to no strength. This shows that these activator concentrations are insufficient to activate the slag and to form a geopolymer concrete.

Example 11: Investigation of Reduction in Activator Concentration

[0153] In this example, the same composition as in Example 8 was prepared but with reduced activator content, as per the following table.

TABLE-US-00015 Component wt % of solids Slag 100% 83.3 Sodium carbonate 8% of slag 6.7 Sodium metasilicate 8% of slag 6.7 Borate 2.75% of slag 2.3 HPMC 0.75% of slag 0.63 VAE 0.50% of slag 0.4 Water 20% of premix load Water:cement* ratio 0.200 *cement = slag + sodium carbonate + sodium metasilicate

TABLE-US-00016 Example 11 1 day (MPa) 9.4 4 day (MPa) 69.6 7 day (MPa) 82.4 28 day (MPa)  99.8

[0154] Note the 1-day strength at 9.4 MPa, is indicative an acceptable open time. Additionally, measured open time between 60-90 minutes have been obtained in real time applications. Also, the formula's growth in strength had ‘caught up’ with Example's 9a and 9b formula's strength outcomes after 7 days, and showed equivalent outstanding ultimate strength after 28 days, while only using 8% activators (sodium carbonate and sodium metasilicate). The above result when reviewed against Examples 9a, 9b and 10 proves that the mix synergy of all the powered components in the premix in conjunction with a low water ratio is unique in obtaining acceptable open time combined with very high ultimate compressive strength in the concrete produced.

SUMMARY

[0155] A prior art geopolymer cement (comprising: slag, sodium carbonate, and sodium metasilicate), even with some borate retarder, has little to no open time. Adding borate retarder at progressively higher concentrations has a diminishing effect on open time, and even at relatively high concentrations does not provide open time sufficient to make the formula usable for practical industry applications. Increasing the water content improves open time marginally but does so at the expense of compressive strength. Also, a higher concentration of activator does not improve ultimate strength, even with low water content.

[0156] It has been found that utilising HPMC (instead of borate) provides an increase in open time, but only at relatively high concentrations, and even then, the composition is not usable in practical industry applications. Furthermore, severe cracking of the cured material results when using relatively high concentrations of HPMC.

[0157] Surprisingly, reducing the HPMC to relatively low concentrations, and when used in combination with borate, provides an acceptable open time of around 60 minutes, but cracking remains an issue. The present applicant has found that cracking was substantially ameliorated by surprisingly low concentrations of polymeric binder. Furthermore, the inventive compositions disclosed herein display a rate of strength development that is at least equivalent to that of OPC-based concretes, and wherein the ultimate 28-day strength is significantly higher than OPC-based concretes.

[0158] When the activator concentration is under 8% the binder either does not cure or does so too slowly to be useful in the field. By increasing the activator concentration to equal to or greater than 10% the strength should develop faster, which would have a negative effect on open time. It was found that additional water can be added to slow down the rate of curing to increase open time, but mechanical properties are relatively low and the open time could not be controlled to the desired range. Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. In particular, features of any one of the various described examples may be provided in any combination in any of the other described examples. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.