Title of Invention	CONTROLLED DETERIORATION OF NON - REINFORCED CONCRETE ANCHORS
Abstract	A concrete formulation, which undergoes controlled deterioration in water, that can be used for making anchors for releasably tethering submarine devices at the seabed. The anchor may have handles for a device release mechanism or a central hole for a central device release mechanism. The formulation includes additives, which cause the cement to transform into non-binding Thaumasite over a pre-set period of time, leaving only natural material on the seafloor.

Title of Invention

CONTROLLED DETERIORATION OF NON - REINFORCED CONCRETE ANCHORS

Abstract

A concrete formulation, which undergoes controlled deterioration in water, that can be used for making anchors for releasably tethering submarine devices at the seabed. The anchor may have handles for a device release mechanism or a central hole for a central device release mechanism. The formulation includes additives, which cause the cement to transform into non-binding Thaumasite over a pre-set period of time, leaving only natural material on the seafloor.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See section 10, rule 13) CONTROLLED DETERIORATION OF NON-REINFORCED CONCRETE ANCHORS" ELECTROMAGNETIC GEOSERVICES AS; of Stiklestadveien 1, N-7041 Trondheim, Norway. The following specification particularly describes the invention and the manner in which it is to be performed. ) Concrete is widely used in contact with water in constructions such as piers, bridge pillars, oil platforms etc. Concrete may also be used to make 5 anchors for releasably tethering a. submarine device at the seabed. Submarine devices are used for many purposes, for example, Sea Bed Logging surveys. These surveys require measuring devices to be tethered on the seabed, remain static during the survey, and be released afterwards so that the expensive device can be reused. 10 The measuring device, to the top of which a floater element is attached, is strapped to a concrete anchor element. The anchor then helps to sink the device in a stable manner and to secure a stable position on the seabed. After the measurements are finished, the device is released and floats to the surface leaving the concrete anchor behind. The concrete anchor is left on the seafloor 15 and apart from the fact that it is a foreign object on the seabed, it may subsequently present an obstacle for fisheries (e.g. trawling) or other industrial activity. Therefore, it would be desirable to develop concrete that will disintegrate within a limited time after contact with water, and, for seawater 20 applications, preferably only in seawater. In order to prevent the concrete anchors forming obstacles for trawling and other activities, the concrete should disintegrate shortly after the end of the useful life of the anchor. A secondary advantage of such an approach would be to ensure recovery of the expensive measuring devices after some time in cases where the release mechanism 25 should fail. The concrete composition should disintegrate into components that are not harmful to the environment and marine life. -2- The hydraulic binder of concrete based on Portland cement is amorphous calcium silicate hydrate (CSH-gel) where some 25% crystalline calcium hydroxide is embedded. Other less abundant minerals exist as well. If sufficient calcium carbonate is added to such a concrete (e.g. as 5 limestone filler), it is known that the concrete will be prone to degradation by sulphate attack at low temperatures (12H20) without binding 10 properties. Three components are required to form Thaumasite: 1. Calcium silicate (taken from the cement paste) 2. Calcium carbonate (e.g. addition of limestone filler) 3. Sulphate (usually intruded from the surroundings) The formation of Thaumasite is discussed by Sibbick, T., Fenn, D. and 15 Crammond, N. in "The Occurrence of Thaumasite as a product of Seawater Attack?', Cement and Concrete Composites, Vol. 25, No. 8, December 2003, pp. 1059-1066. The bedding mortar of a recently constructed harbour wall step in South Wales had suffered severe cracking and spalling within 2 years. The reaction products formed included Thaumasite, Ettringite, Brucite and hydrated magnesium silicate. The study proved that concrete with limestone will eventually form Thaumasite in line with the chemical changes outlined above. This reference discusses the undesired formation of Thaumasite and the problems caused thereby. However, the aim of the current invention is to provide a concrete formulation which may be used for seabed anchors, which will cause the anchor to disintegrate substantially shortly after the end of the useful life of the anchor. The useful life of the anchor .after deployment in the sea is of the order of 1 month. It is an object of the present invention to provide a cement formulation that will degrade in a controlled fashion, particularly in sea water. - 3 The present applicants have discovered that the degradation of the binder in a cement can be accelerated somewhat (with respect to standard compositions) by using a cement composition with sufficient limestone filler and high water-to-cement ratio (w/c) to make the resulting concrete very open 5 for diffusion of sulphates. The present applicants have further discovered that concrete formulations which include calcium sulphate in the form of either anhydrite (CaS04), hemihydrate (CaS04«l/2H20) or gypsum. (CaS04«2H20) as an additive, as well as sufficient limestone filler, experience a greatly accelerated 10 rate of degradation. Such concrete will be stable as long as it is stored dry and will only require fresh water to start: the Thaumasite formation. Furthermore, the reaction takes place uniformly throughout the concrete cross-section and an even crumbling is likely to occur. 15 According to the invention, there is provided a Portland cement formulation comprising amorphous calcium silicate, the formulation additionally comprising calcium carbonate and a source of sulphate. The calcium carbonate may represent 10 to 50 wt % of the formulation and may be in the form of limestone, chalk or calcite. The sulphate may 20 represent 6 to 50 wt % of the formulation and may be in the form of a metal sulphate such as calcium sulphate. The composition of the cement is such that items formed from it will undergo disintegration as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite. The particles in the 25 cement which react to form Thaumasite will preferably be small (e.g. less than 1 mm in diameter) in order to allow the reaction to progress at an appropriate rate. 4 WO 2006/03801-8- PGT/GB2W5W03859 The preferred form of calcium sulphate is anhydrite (CaS04). Anhydrite is better for workability, in particularly if it is nearly "dead burnt" for delayed reactivity. A preferred cement formulation is obtained when the calcium carbonate 5 and source of sulphate are present in amounts which give rise to a molar ratio of S0427CQ32" of between 0.2 and 3.0. Particularly, the calcium carbonate and source of sulphate may be present in a stoichiometric ratio with respect to Thaumasite. The cement formulation may additionally comprise calcium hydroxide. 10 The calcium hydroxide may represent 2 to 40 wt % of the formulation. Preferably, the cement formulation contains no additives which would not decompose into components occurring naturally in the environment, and no organic admixtures. The main components of seawater are in decreasing order; 18,980 ppm 15 chloride (CI"), 10,561 ppm sodium (Na4), 2,650 ppm sulphate (S042~), 1,272 ppm magnesium (Mg2+), 400 ppm calcium (Ca2+), 380 ppm potassium (K4), 140 ppm carbonate (CO32"), 65 ppm bromide (Br), 13 ppm strontium (Sr) and up to 7 ppm silica (Si02). Seawater is in principle saturated with respect to calcium carbonate and is essential for crustaceans, mussels etc in building 20 protective shells. For this reason seawater has pH on the basic side (around 8). Thaumasite, Ca3Si(OH)12H2, can be said to consist of 27.02% calcium oxide (CaO), 9.65% silica (Si02), 43.40% water (H20), 7.07% carbon dioxide (C02) and 12.86% sulphur trioxide (S03) although it is a calcium salt of silicate, carbonate and sulphate. Thaumasite occurs naturally, 25 and transparent crystals are for instance found in the N'Chwaning Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Another site is the Bjelke Mine near Areskutan, Jamtland, Sweden. Standard industrial concrete formulations include organic admixtures such as plasticizers, which improve the workability of the concrete and - 5- decrease the water demand. However, since the concrete of this invention is designed to disintegrate, the inclusion of these admixtures is undesirable due to environmental concerns. According to a further aspect of the invention, there is provided a 5 Portland cement formulation as described in any of the preceding aspects, which is mixed with an aggregate, optionally being a light weight aggregate, preferably with a particle size of less than 50 mm. The aggregate may optionally be any of the following: filler, sand, limestone with particle size greater than 1 mm or gravel. 10 The invention also extends to an anchor for releasably tethering a submarine device at the seabed, made substantially from a formulation which will allow the anchor to disintegrate as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite. The anchor optionally includes a 15 handle for the attachment of a release mechanism, which is preferably made of wood, leather or any other natural and environmentally non-polluting material suitable for the purpose. Alternatively, there may be a central hole for a central release mechanism. The invention also extends to a method of tethering a submarine device 20 at the seabed, which comprises: forming an anchor by mixing a cement or concrete formulation as described in any of the above aspects, respectively, with water, allowing the mixture to harden to form a finished anchor, attaching the submarine device to the anchor, and deploying the anchor and submarine device at a required location at the seabed. This method may be combined with 25 the further steps of releasing the submarine device from the anchor and allowing the anchor to disintegrate as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite. 6 WQ-a006/038018 PGF/GD2003/003859 The present invention can be put into practice in various ways, some of which will now be described in the following set of example compositions, with reference to the accompanying drawings, in which: Figure 1 is a plot of compressive strength at age 28 days versus water- 5 to-cement ratio for concrete; Figure 2 is a plot of compressive strength evolution for concrete as a function of time and limestone (LS) addition; Figure 3 is a plot of compressive strength evolution for concrete as a function of time and addition of Limestone (LS)/anhydrite (ratio stoichiometric 10 with respect to Thaumasite) The aspect of the invention extending to an anchor made substantially from a formulation as described may be put into practice in various ways, an example of which is described below with reference to the accompanying drawings, in which: 15 Figure 4 is a side view of the anchor; Figure 5 is a section on A-A of Fig. 4; Figure 6 is a plan view of the anchor; Figure 7 is a view of the top surface of the anchor; Figure 8 is a view of the underside of the anchor. 7 WO 2006/038018 PCT/G1TCW5WB859- The following materials were used in trial concrete mixing. Cement: Norcem Rapid Portland Cement (Industry cement), laboratory cement "IN5" Limestone: 8 plastic bags of Verdalskalk Calcium carbonate, approximately 5 200kg Anhydrite: 1 bucket of Anhydrite, approximately 80 kg Aggregate:- 1 big bag of Norstone sand 0-8 mrri, approximately 300 kg 2 big bags of Verdalskalk, limestone 8-16 mm crushed stone, approximately 10 300 kg 2 bags of FrǾseth sand 0.4 mm, approximately 50 kg Laboratory concretes Proposed laboratory mixes to make concrete cubes and beams are shown in Table 1. The reference concrete is the one used by Spenncon Verdal AS 15 today. Spenncon has previously produced concrete elements approximately 1,000 x 1,000 x 90 mm for EMGS. The composition of the other laboratory recipes is with increasing limestone filler content, ending up with a stoichiometric concrete composition that deteriorates the binder totally. The limestone content is increased in steps of 20% and the cement+ limestone filler 20 + anhydrite mass is kept constant to 410 kg/m3 concrete. The concrete density is proposed equal for all the mixes. The water/cement (w/c) ratios are increasing from 0.45 to 0.81 and thereby the porosity increases as well. - 8 - WO 2006/038018 B€T/GD2005/003859 Table 1: Nominal concrete composition, kg/m3 Mix No 1 2 3 4 5 6 7 8 9 % Limestone 0 20 20 40 40 60 60 80 80 Rapid cement 410 342 342 293 293 256 256 228 228 Water, free 185 185 185 185 185 185 185 185 185 Water/cement-ratio 0.45 0.54 0.54 0.63 0.63 0.72 0.72 0.81 0.81 Limestone filler 0 68 68 117 117 154 154 182 182 Anhydrite 0 0 86 0 .147 0 192 0 228 Ardal 0-8 nun sand 885. 885 840 885 810 885 790 885 770 Fraseth 0-3 mm sand 40 40 40 40 38 40 38 40 37 Verdalskalk 8-16 mm gravel 880 880 840 880 810 880 785 880 770 Density 2400 2400 2401 2400 2400 2400 2400 2400 2400 Cement + limestone 410 410 410 410 410 410 410 410 410 From each mix 100 mm cubes and 100 x 100 x 400 mm prisms were made. The concrete was demoulded after 20 hours and placed in water at 20°C until 7 days age. 5 9 Laboratory procedures Concrete for documentation of properties was mixed in a 60 litre forced action mixer. Each concrete was mixed in two batches to achieve a total volume of 120 litres. 5 The mixing was carried out according to the following procedure: 1. 1 min mixing of dry materials 2. addition of mixing water during 1 min mixing,, 3. addition of excess mixing water to get a slump of approximately 200 mm 10 4. 2 min rest 5. 2 min mixing Fresh concrete properties for each mix were determined according to EN 12350, part 2 (slump), part 6 (density) and part 7 (air content). Compressive strength was determined on 100 mm cubes according to 15 EN 12390 part 3. Curing regimes After 7 days the specimens were stored at three temperature regimes: 1. In laboratory fresh water at 20°C 2. In sea water 5°-9°C 20 3. In concentrated seawater (5 times natural concentration) in laboratory at 5°C CCT/GD20U5ffitt38ST 40- Testing schedule Three cubes were tested for compressive strength after demoulding at 24 hours. Three cubes were tested for compressive strength after 7 days in fresh water of 20°C. The other. test specimens were placed in hardening regime 2 and 3 for 5 later testing. The testing schedule from 1 month after mixing for each mix is shown in Table 2 (the number indicates number of cubes or prisms subjected for testing). Table 2: Testing schedule for all mixes Testing after mixing 1 month 2 months 3 months 4 months 5 months 1 year Bending strength 5°C 2 3 3 3 3 Compressive strength 5°C 3 3 3 3 3 3 3 3 3 3 Hardening conditions A B C B C B C B C B C B C A - Laboratory fresh water at 20°C 10 B - Seawater 5-9°C C - Concentrated (5 times) seawater to increase the deterioration, 5°C Results 15 Fresh Concrete The real compositions of the 9 mixes are shown in Table 3. The workability was measured by standard slump measure according to EN 12350- PC 2. The density and air content was measured according to EN 12350-6 and EN 12350-7, respectively. The density and air content was measured according to EN 12350-6 and EN 12350-7, respectively. 5 12 ECT/CB2005/003859 Table 3: Real composition and fresh concrete results, (surface dry aggregates) Concrete Mix No 1 2 3 4 5 6 7 8 9 Industry cement 400 334 277 286 212 250 170 223 143 Calcium Carbonate 0 67 5.5 114 85 150 102 179 114 srete Anhydrite 0 0 70 0 107 0 129 0 144 a om.n Ardal sand 0-8 mm 856 861 866 865 870 863 863 867 862 bH Fraseth sand 0-4mm 39 39 38 38 38 38 38 38 38 Verdalskalk 8-16 mm 856 861 861 860 865 858 858 862 857 Free water 219 211 208 209 201 208 208 204 207 Water/binder-ratio .55 .631 .750 .731 .950 .835 1.22 .915 1.45 Slump, batch 1, mm 195 180 200 190 190 190 210 200 210 Slump, batch 2, mm 205 190 200 200 200 190 210 200 210 Air content batch 1, % 1.2 1.3 1.2 1.2 1.4 1.3 1.0 1.3 0.9 Air con tent batch 2, % 1.2 1.2 1.3 1.3 1.3, 1.2 0.9 1.3 0.9 13 P€T/GB2005/0038S Density batch 1, kg/m3 2370 2370 2375 2375 2375 2365 2365 2370 2370 Density batch 2, kg/m3 2365 2375 2375 2370 23801 2370 2370 2375 2360 Hardened concrete (in fresh water) Eight 100 mm cubes were cast for determination of compressive strength according to EN 12390-3 at ages, 1, 7 and 28 days. The results are listed in 5 Table 4. Table 4: Testing results after hardening in air and fresh water Concrete Mix No 1 2 3 4 5 6 7 8 9 Compressive strength 30.8 25.1 16.2 19.0 12.4 16.1 7.2 13.2 5.2 MPa after 1 day in air at 20°C Compressive strength 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1 MPa after 7 days in water, 20° C Compressive strength MPa 48.1 44.4 33.7 38.7 27.3 33.1 20.2 27,8 16.1 after 28 days in water, 20° C Compressive strength MPa 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1 after 28 days in water, 5°C Flexural strength, MPa 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5 after 28 days' in water, 5°C Comments: Grey shades mark results for concrete with anhydrite 14 WO 2006/038013— P€T/CB2005/00385» Hardened concrete in sea water The compressive and flexural strength of concrete cured in both fresh and sea water are given in Table 5. Grey shades mark results for concrete with 5 anhydride. "-" indicates disintegrated concrete. 15 pCTG02oo5/oo3859 Table 5: Testing results after hardening in air, fresh water and sea water Concrete Mix No 1 2 3 4 5 6 7 8 9 Compressive strength 30.8 25.1 16.2 19.0 12.4 16.1 7.2 13.2 5.2 MPa after 1 day in air at 20°C Compressive strength 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1 MPa after 7 days in fresh water, 20° C Compressive strength MPa 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1 after 28 days in freshwater, 5° C Compressive strength MPa 45.7 43.7 30.5 37.4 22.9 31.8 9.9 27.1 6.4 2 months in seawater, 5°C Compressive strength 48.4 45.2 24.3 37.0 12.8 31.8 1.1 27.8 _. MPa 3 months in sea water, 5°C • Compressive . strength 49.9 45.3 12.1 37.8 6.4 34.0 _ 28.1 _ MPa 4 months in sea water, 5°C Compressive strength 49.5 _ _ MPa 5 months in sea water, 5CC Compressive strength _ . MPa 12 months in sea water 5°C Flexural strength MPa 28 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5 days in freshwater, 5°C . Flexural strength MPa 28 6.5 5.6 3.6 5.1 3.5' 4.6 2.7 3.9 2.3 days in seawater, 5°C \|i -16- PCT/GD2005/0038SS) Flexural strength MPa 2 6.3 5.8 3.7 5.5 3.1 5.0 1.8 4.2 1.2 months in seawater, 5°C 4 Hardened concrete in concentrated sea water (salt water) Compressive strength of concrete stored in concentrated (5x) sea water is given 5 in Table 6. Table 6: Testing results after hardening in air, fresh water and salt water Concrete Mix No 1 2 3 4 5 6 7 8 9 Compressive strength 30.8 25.1 16.2 19.0 12.4 16.1 7.2 13.2 5.2 MPa after 1 day in air at 20°C Compressive strength 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1 MPa after 7 days in fresh water, 20° C Compressive strength MPa 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1 after 28 days in freshwater, 5° C. Compressive strength MPa 44.7 41.7 29.2 33.9 23.6 3.0.1 15.5 25.1 13.2 28 days in salt water, 5°C Compressive strength 47.2 42.5 20.7 35.5 21.8 30.1 12.7 25.5 9.3 MPa 2 months in salt ■ water, 5°C Compressive strength 45.9 42.5 17.6 34.9 10.8 28.1 4.1 26.4 2.0 MPa ,3 months in salt water, 5°C - 17- WO 2006/038018 PCT/GD2005/003859 17 Compressive strength MPa 4 months in salt water, 5°C 44.3 41.4 14.4 34.8 7.4 26.0 13/2 25.8 16/2 Compressive strength MPa 12 months in salt water, 5°C Flexural strength MPa 28 days in freshwater, 5°C 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5 Flexural strength MPa 28 days in a salt water, 5°C 6.5 6.0 3.4 5.1 3.2 4.7 2.7 4.0 2.3 Flexural strength MPa 2 months in salt water, 50C 5.8 6.2 3.6 5.3 3.0 5.0 2.1 4.7 1.5 Comments: Grey shades mark results for concrete with anhydrite Discussion Concrete cured in fresh water The development of compressive strength after 28 days curing versus 5 water/cement ratio is shown in Fig. 1 and compared with results from Norcem. The concrete with limestone filler as well as the concrete with limestone filler . and gypsum are close to the reference mixes. Concrete cured in sea water All the concrete cubes (and prisms) were stored their moulds in 10 laboratory conditions the first day and thereafter hardened in fresh water up to seven days. Then the prisms were placed in seawater (5°C to 9°C) and tested 1, 2, 3, 4, 5 and 12 months after casting. Fig. 2 shows the results with limestone filler only while Fig. 3 depicts the result with limestone filler and. anhydrite in stoechiometric ratio with respect to Thaumasite formation. 18 W£-300(i/038018 PQT/GB2005/003859 Addition of limestone as the only additive has not yet (within the test period) given any significant deterioration, even for the most permeable and porous concrete. The addition of both limestone filler and anhydrite to the concrete has 5 caused increasing disintegration with increasing amount of additives. Concrete specimens with 60 and 80% limestone filler of cement weight were totally destroyed after 3 months. Table 7: Strength development after hardening in freshwater and sea water Concrete Mix No 1 2 3 4 5 6 7 8 9 Compressive strength MPa. 7 days in fresh water, 20° C 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1 Compressive strength MPa 28 days in freshwater, 5° C 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1 Compressive strength MPa 28 days in salt water, 5°C 45.7 41.1 30.5 35.8 25.1 30.1 17.8 25.8 13.6 Strength sea water 28 days/Strength fresh water 28 days 0.98 0.95 0.97 0.97 0.94 0.95 0.94 0.97 0.90 Flexural strength MPa 28 days in freshwater, 5°C 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5 Flexural strength MPa 28 days in sea water, 5°C 6.5 5.6 3.6 5.1 3.5 4.6 2.7 3.9 2.3 Strength sea water 28 days/Strength fresh water 28 days 1.10 1.08 1.03 0.98 1.03 1.15 1.00 0.98 0.92 Comments: Grey shades mark results for concrete with anhydrite 19 WO2006/038018 PCI/CB2005/003859 19^ Compressive strength deterioration is less than 10% for all mixes during the three first weeks of exposure to sea water, which make them suitable as anchors for the seabed logging period. The flexural strength was higher after three weeks exposure in sea 5 water, except for the cement with the highest amount of limestone filler and anhydrite. Concrete cured in concentrated sea water There was only a small difference in deterioration between sea water and concentrated (5x) sea water for mixes with anhydrite. Since the specimen 10 without anhydrite in natural seawater did not deteriorate, it is difficult to say whether the concentrated seawater increases the deterioration rate or not, but the compressive strength was somewhat lower after storage in concentrated sea water as seen by comparing results in Table 5 and 6. Including limestone filler (i.e. calcium carbonate) in the recipe did not 15 deteriorate the hardened concrete within 6 months after submersion in seawater. To speed up the deterioration, tests were also performed by adding calcium carbonate and anhydrite in a stochiometric ratio with respect to Thaumasite that deteriorates the binder totally. These specimens disintegrated 20 in contrast to the specimen without anhydrite. Increasing the amount of additives decreased the 7 and 28 days compressive strength for concrete hardened in fresh water. Preferred Physical Form Referring to figures 4 to 8 of the drawings, the anchor comprises 25 a body 10 with legs 11. The presence of two inclined surfaces 14 located on each side of the anchor results in the rotation of the anchor during sinking. Further, there is a hole 12 suitable for attaching a central release mechanism 20 WO 2006/038018 PCF/GB2003/00385r (not shown). Slots 13 are introduced in the body of the anchor, to stabilise the anchor during sinking. Specific Preferred Embodiment A recommended concrete composition with 40% limestone filler and a 5 stoechiometric ratio of anhydrite with respect to Thaumasite was found to disintegrate in seawater after 4 months. The composition of the recommended concrete is: Ingredients in kg/m Producer Recipe 1 Recipe 2 Rapid Portland Cement Norcern 210 210 Free water 195 195 Limestone filler Verdal Kalkverk 85 85 Anhydrite Outocompu, Odda 110 110 Sand 0-8 mm Norstone, Ardal 880 920 Sand 0-4 mm Froseth, local deposite 40 0 Crushed stone 8-16 mm Verdal Kalkverk 880 880 The concrete contains no ingredients harmful to the marine environment it is 10 meant to serve in. All ingredients are found in natural gravel, limestone and/or seawater. The concrete does not contain any organic admixtures. The anchor is characterised in that its physical form causes it to rotate during sinking by means of the presence of inclined surfaces located along each side of the anchor. 21 WO 2006/038018 P€T/GD2005/00383r We claim: 1. A Portland cement formulation comprising amorphous calcium silicate, the formulation additionally comprising calcium carbonate and a source of 5 sulphate. 2. A formulation as claimed in Claim 1, in which the calcium carbonate content is in the range 10 to 50 wt% of the formulation. 10 3. A formulation as claimed in Claim 1 or Claim 2, in which the calcium carbonate is in the form of limestone, chalk or calcite. 4. A formulation as claimed in any preceding Claim, in which the sulphate content is in the range 6 to 50 wt% SO42" of the formulation. 15 5. A formulation as claimed in any preceding Claim, in which the sulphate is in the form of a metal sulphate. 6. A formulation as claimed in Claim 5, in which the metal sulphate is a 20 calcium sulphate. 7. A formulation as claimed in Claim 6, in which the calcium sulphate is anhydrite. 25 8. A formulation as claimed in any preceding Claim, including in which the calcium carbonate and source of sulphate are present in amounts which give rise to a molar ratio of S042/C032'of between 0.2 and 3.0. 22 WO2006/(B8et* PGT/GB3005/0038S9 9. A formulation as claimed in any preceding Claim, including in which the calcium carbonate and source of sulphate are present in a stoichiometric ratio with respect to thaumasite. 5 10. A formulation as claimed in any preceding Claim, further including calcium hydroxide. 11. A formulation as claimed in Claim 10, in which the calcium hydroxide content is in the range 2 to 40 wt % of the formulation. 10 12. A formulation as claimed in. any preceding Claim which includes no additives which would not decompose into components occurring naturally in the environment. 15 13. A formulation as claimed in any preceding claim which includes no organic admixtures. 14. A concrete formulation, comprising a cement as claimed in any preceding Claim, mixed with an aggregate. 20 15. A concrete formulation, comprising a cement as claimed in Claim 14, h which the aggregate is a light weight aggregate. 16. A formulation as claimed in any of Claims 14 to 15, in which the 25 aggregate represents 0 to 80 wt % of the concrete formulation. 17. A formulation as claimed in any of Claims 14 to 16, in which the particle size of the aggregate is less than 50 mm. 23 18. A formulation as claimed in any of Claims 14 to 17, in which the aggregate material is filler, sand, limestone with particle size greater than 1 mm or gravel. 19. An anchor for releasably tethering a submarine device at the seabed, made substantially from a formulation as claimed in any preceding Claim. 20. An anchor as claimed in Claim 19, further including at least one handle for the attachment of a release mechanism. 21. An anchor as claimed in Claim 20, in which the handle is made from a natural and environmentally non-polluting material. 22. An anchor as claimed in Claim 21, in which the handle is made from wood, or leather. 23. An anchor as claimed in Claim 19, further including a central hole for a central release mechanism. 24. A method of tethering a submarine device at the seabed, which comprises: forming an anchor by mixing a cement or concrete formulation as claimed in any of Claims 1 to 13 or 14 to 18, respectively, with water; allowing the mixture to harden to form a finished anchor; attaching the submarine device to the anchor; and deploying the anchor and submarine device at a required location at the seabed. 25. A method as claimed in Claim 24 combined with the further steps of releasing the submarine device from the anchor and allowing the anchor to disintegrate as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite. 30 Dated this 05th Day of May, 2007 OMANA RAMAKRISHNAN Of K &S PARTNERS 35 AGENT FOR THE APPLICANT(S) 24 ABSTRACT CONTROLLED DETERIORATION OF NON-REINFORCED CONCRETE ANCHORS A concrete formulation, which undergoes controlled deterioration in water, that can be used for making anchors for releasably tethering submarine devices at the seabed. The anchor may have handles for a device release mechanism or a central hole for a central device release mechanism. The formulation includes additives, which cause the cement to transform into non-binding Thaumasite over a pre-set period of time, leaving only natural material on the seafloor. 25

Full Text

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
CONTROLLED DETERIORATION OF NON-REINFORCED CONCRETE ANCHORS"
ELECTROMAGNETIC GEOSERVICES AS; of Stiklestadveien 1, N-7041 Trondheim, Norway.
The following specification particularly describes the invention and the manner in which it is to be performed.
)

Concrete is widely used in contact with water in constructions such as piers, bridge pillars, oil platforms etc. Concrete may also be used to make
5 anchors for releasably tethering a. submarine device at the seabed. Submarine devices are used for many purposes, for example, Sea Bed Logging surveys. These surveys require measuring devices to be tethered on the seabed, remain static during the survey, and be released afterwards so that the expensive device can be reused.
10 The measuring device, to the top of which a floater element is attached,
is strapped to a concrete anchor element. The anchor then helps to sink the device in a stable manner and to secure a stable position on the seabed. After the measurements are finished, the device is released and floats to the surface leaving the concrete anchor behind. The concrete anchor is left on the seafloor
15 and apart from the fact that it is a foreign object on the seabed, it may subsequently present an obstacle for fisheries (e.g. trawling) or other industrial activity.
Therefore, it would be desirable to develop concrete that will disintegrate within a limited time after contact with water, and, for seawater
20 applications, preferably only in seawater. In order to prevent the concrete anchors forming obstacles for trawling and other activities, the concrete should disintegrate shortly after the end of the useful life of the anchor. A secondary advantage of such an approach would be to ensure recovery of the expensive measuring devices after some time in cases where the release mechanism
25 should fail.
The concrete composition should disintegrate into components that are not harmful to the environment and marine life.
-2-

The hydraulic binder of concrete based on Portland cement is amorphous calcium silicate hydrate (CSH-gel) where some 25% crystalline calcium hydroxide is embedded. Other less abundant minerals exist as well.
If sufficient calcium carbonate is added to such a concrete (e.g. as
5 limestone filler), it is known that the concrete will be prone to degradation by sulphate attack at low temperatures (12H20) without binding
10 properties. Three components are required to form Thaumasite:
1. Calcium silicate (taken from the cement paste)
2. Calcium carbonate (e.g. addition of limestone filler)
3. Sulphate (usually intruded from the surroundings)
The formation of Thaumasite is discussed by Sibbick, T., Fenn, D. and
15 Crammond, N. in "The Occurrence of Thaumasite as a product of Seawater Attack?', Cement and Concrete Composites, Vol. 25, No. 8, December 2003, pp. 1059-1066. The bedding mortar of a recently constructed harbour wall step in South Wales had suffered severe cracking and spalling within 2 years. The reaction products formed included Thaumasite, Ettringite, Brucite and hydrated magnesium silicate. The study proved that concrete with limestone will eventually form Thaumasite in line with the chemical changes outlined above.
This reference discusses the undesired formation of Thaumasite and the problems caused thereby. However, the aim of the current invention is to provide a concrete formulation which may be used for seabed anchors, which will cause the anchor to disintegrate substantially shortly after the end of the useful life of the anchor. The useful life of the anchor .after deployment in the sea is of the order of 1 month.
It is an object of the present invention to provide a cement formulation that will degrade in a controlled fashion, particularly in sea water.
- 3

The present applicants have discovered that the degradation of the binder in a cement can be accelerated somewhat (with respect to standard compositions) by using a cement composition with sufficient limestone filler and high water-to-cement ratio (w/c) to make the resulting concrete very open
5 for diffusion of sulphates.
The present applicants have further discovered that concrete formulations which include calcium sulphate in the form of either anhydrite (CaS04), hemihydrate (CaS04«l/2H20) or gypsum. (CaS04«2H20) as an additive, as well as sufficient limestone filler, experience a greatly accelerated
10 rate of degradation. Such concrete will be stable as long as it is stored dry and will only require fresh water to start: the Thaumasite formation. Furthermore, the reaction takes place uniformly throughout the concrete cross-section and an even crumbling is likely to occur.
15 According to the invention, there is provided a Portland cement formulation comprising amorphous calcium silicate, the formulation additionally comprising calcium carbonate and a source of sulphate.
The calcium carbonate may represent 10 to 50 wt % of the formulation and may be in the form of limestone, chalk or calcite. The sulphate may
20 represent 6 to 50 wt % of the formulation and may be in the form of a metal sulphate such as calcium sulphate. The composition of the cement is such that items formed from it will undergo disintegration as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite. The particles in the
25 cement which react to form Thaumasite will preferably be small (e.g. less than 1 mm in diameter) in order to allow the reaction to progress at an appropriate rate.
4

WO 2006/03801-8- PGT/GB2W5W03859
The preferred form of calcium sulphate is anhydrite (CaS04). Anhydrite is better for workability, in particularly if it is nearly "dead burnt" for delayed reactivity.
A preferred cement formulation is obtained when the calcium carbonate
5 and source of sulphate are present in amounts which give rise to a molar ratio
of S0427CQ32" of between 0.2 and 3.0. Particularly, the calcium carbonate and
source of sulphate may be present in a stoichiometric ratio with respect to
Thaumasite.
The cement formulation may additionally comprise calcium hydroxide.
10 The calcium hydroxide may represent 2 to 40 wt % of the formulation.
Preferably, the cement formulation contains no additives which would not
decompose into components occurring naturally in the environment, and no
organic admixtures.
The main components of seawater are in decreasing order; 18,980 ppm
15 chloride (CI"), 10,561 ppm sodium (Na4), 2,650 ppm sulphate (S042~), 1,272
ppm magnesium (Mg2+), 400 ppm calcium (Ca2+), 380 ppm potassium (K4),
140 ppm carbonate (CO32"), 65 ppm bromide (Br), 13 ppm strontium (Sr) and
up to 7 ppm silica (Si02). Seawater is in principle saturated with respect to
calcium carbonate and is essential for crustaceans, mussels etc in building
20 protective shells. For this reason seawater has pH on the basic side (around 8).
Thaumasite, Ca3Si(OH)12H2, can be said to consist of
27.02% calcium oxide (CaO), 9.65% silica (Si02), 43.40% water (H20), 7.07%
carbon dioxide (C02) and 12.86% sulphur trioxide (S03) although it is a
calcium salt of silicate, carbonate and sulphate. Thaumasite occurs naturally,
25 and transparent crystals are for instance found in the N'Chwaning Mine,
Kalahari Manganese Field, Northern Cape Province, South Africa. Another
site is the Bjelke Mine near Areskutan, Jamtland, Sweden.
Standard industrial concrete formulations include organic admixtures such as plasticizers, which improve the workability of the concrete and
- 5-

decrease the water demand. However, since the concrete of this invention is designed to disintegrate, the inclusion of these admixtures is undesirable due to environmental concerns.
According to a further aspect of the invention, there is provided a
5 Portland cement formulation as described in any of the preceding aspects, which is mixed with an aggregate, optionally being a light weight aggregate, preferably with a particle size of less than 50 mm. The aggregate may optionally be any of the following: filler, sand, limestone with particle size greater than 1 mm or gravel.
10 The invention also extends to an anchor for releasably tethering a
submarine device at the seabed, made substantially from a formulation which will allow the anchor to disintegrate as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite. The anchor optionally includes a
15 handle for the attachment of a release mechanism, which is preferably made of wood, leather or any other natural and environmentally non-polluting material suitable for the purpose. Alternatively, there may be a central hole for a central release mechanism.
The invention also extends to a method of tethering a submarine device
20 at the seabed, which comprises: forming an anchor by mixing a cement or concrete formulation as described in any of the above aspects, respectively, with water, allowing the mixture to harden to form a finished anchor, attaching the submarine device to the anchor, and deploying the anchor and submarine device at a required location at the seabed. This method may be combined with
25 the further steps of releasing the submarine device from the anchor and
allowing the anchor to disintegrate as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite.
6

WQ-a006/038018 PGF/GD2003/003859
The present invention can be put into practice in various ways, some of which will now be described in the following set of example compositions, with reference to the accompanying drawings, in which:
Figure 1 is a plot of compressive strength at age 28 days versus water-
5 to-cement ratio for concrete;
Figure 2 is a plot of compressive strength evolution for concrete as a function of time and limestone (LS) addition;
Figure 3 is a plot of compressive strength evolution for concrete as a function of time and addition of Limestone (LS)/anhydrite (ratio stoichiometric
10 with respect to Thaumasite)
The aspect of the invention extending to an anchor made substantially from a formulation as described may be put into practice in various ways, an example of which is described below with reference to the accompanying drawings, in which:
15 Figure 4 is a side view of the anchor;
Figure 5 is a section on A-A of Fig. 4;
Figure 6 is a plan view of the anchor;
Figure 7 is a view of the top surface of the anchor;
Figure 8 is a view of the underside of the anchor.

7
WO 2006/038018 PCT/G1TCW5WB859-
The following materials were used in trial concrete mixing.
Cement: Norcem Rapid Portland Cement (Industry cement), laboratory cement "IN5"
Limestone: 8 plastic bags of Verdalskalk Calcium carbonate, approximately
5 200kg
Anhydrite: 1 bucket of Anhydrite, approximately 80 kg
Aggregate:-
1 big bag of Norstone sand 0-8 mrri, approximately 300 kg
2 big bags of Verdalskalk, limestone 8-16 mm crushed stone, approximately
10 300 kg
2 bags of FrǾseth sand 0.4 mm, approximately 50 kg
Laboratory concretes
Proposed laboratory mixes to make concrete cubes and beams are shown in Table 1. The reference concrete is the one used by Spenncon Verdal AS
15 today. Spenncon has previously produced concrete elements approximately 1,000 x 1,000 x 90 mm for EMGS. The composition of the other laboratory recipes is with increasing limestone filler content, ending up with a stoichiometric concrete composition that deteriorates the binder totally. The limestone content is increased in steps of 20% and the cement+ limestone filler
20 + anhydrite mass is kept constant to 410 kg/m3 concrete.
The concrete density is proposed equal for all the mixes. The water/cement (w/c) ratios are increasing from 0.45 to 0.81 and thereby the porosity increases as well.
- 8 -

WO 2006/038018 B€T/GD2005/003859
Table 1: Nominal concrete composition, kg/m3

Mix No 1 2 3 4 5 6 7 8 9
% Limestone 0 20 20 40 40 60 60 80 80
Rapid cement 410 342 342 293 293 256 256 228 228
Water, free 185 185 185 185 185 185 185 185 185
Water/cement-ratio 0.45 0.54 0.54 0.63 0.63 0.72 0.72 0.81 0.81
Limestone filler 0 68 68 117 117 154 154 182 182
Anhydrite 0 0 86 0 .147 0 192 0 228
Ardal 0-8 nun sand 885. 885 840 885 810 885 790 885 770
Fraseth 0-3 mm sand 40 40 40 40 38 40 38 40 37
Verdalskalk 8-16 mm gravel 880 880 840 880 810 880 785 880 770
Density 2400 2400 2401 2400 2400 2400 2400 2400 2400
Cement + limestone 410 410 410 410 410 410 410 410 410
From each mix 100 mm cubes and 100 x 100 x 400 mm prisms were made. The concrete was demoulded after 20 hours and placed in water at 20°C until 7 days age.
5
9

Laboratory procedures
Concrete for documentation of properties was mixed in a 60 litre forced action mixer. Each concrete was mixed in two batches to achieve a total volume of 120 litres.
5 The mixing was carried out according to the following procedure:
1. 1 min mixing of dry materials
2. addition of mixing water during 1 min mixing,,
3. addition of excess mixing water to get a slump of approximately 200 mm
10 4. 2 min rest
5. 2 min mixing
Fresh concrete properties for each mix were determined according to EN 12350, part 2 (slump), part 6 (density) and part 7 (air content).
Compressive strength was determined on 100 mm cubes according to
15 EN 12390 part 3.
Curing regimes
After 7 days the specimens were stored at three temperature regimes:
1. In laboratory fresh water at 20°C
2. In sea water 5°-9°C
20 3. In concentrated seawater (5 times natural concentration) in laboratory at 5°C

CCT/GD20U5ffitt38ST
40-
Testing schedule
Three cubes were tested for compressive strength after demoulding at 24 hours. Three cubes were tested for compressive strength after 7 days in fresh water of 20°C. The other. test specimens were placed in hardening regime 2 and 3 for
5 later testing. The testing schedule from 1 month after mixing for each mix is shown in Table 2 (the number indicates number of cubes or prisms subjected for testing).
Table 2: Testing schedule for all mixes

Testing after mixing 1 month 2 months 3 months 4 months 5 months 1 year
Bending strength 5°C 2 3 3 3 3
Compressive strength 5°C 3 3 3 3 3 3 3 3 3 3
Hardening conditions A B C B C B C B C B C B C
A - Laboratory fresh water at 20°C 10 B - Seawater 5-9°C
C - Concentrated (5 times) seawater to increase the deterioration, 5°C
Results

15 Fresh Concrete
The real compositions of the 9 mixes are shown in Table 3. The workability was measured by standard slump measure according to EN 12350-

PC
2. The density and air content was measured according to EN 12350-6 and EN 12350-7, respectively.
The density and air content was measured according to EN 12350-6 and EN 12350-7, respectively.
5

12
ECT/CB2005/003859
Table 3: Real composition and fresh concrete results, (surface dry aggregates)

Concrete Mix No 1 2 3 4 5 6 7 8 9
Industry cement 400 334 277 286 212 250 170 223 143
Calcium Carbonate 0 67 5.5 114 85 150 102 179 114
srete Anhydrite 0 0 70 0 107 0 129 0 144
a om.n Ardal sand 0-8 mm 856 861 866 865 870 863 863 867 862
bH Fraseth sand 0-4mm 39 39 38 38 38 38 38 38 38
Verdalskalk 8-16 mm 856 861 861 860 865 858 858 862 857
Free water 219 211 208 209 201 208 208 204 207
Water/binder-ratio .55 .631 .750 .731 .950 .835 1.22 .915 1.45
Slump, batch 1, mm 195 180 200 190 190 190 210 200 210
Slump, batch 2, mm 205 190 200 200 200 190 210 200 210
Air content batch 1, % 1.2 1.3 1.2 1.2 1.4 1.3 1.0 1.3 0.9
Air con tent batch 2, % 1.2 1.2 1.3 1.3 1.3, 1.2 0.9 1.3 0.9
13
P€T/GB2005/0038S
Density batch 1, kg/m3 2370 2370 2375 2375 2375 2365 2365 2370 2370
Density batch 2, kg/m3 2365 2375 2375 2370 23801 2370 2370 2375 2360
Hardened concrete (in fresh water)
Eight 100 mm cubes were cast for determination of compressive strength according to EN 12390-3 at ages, 1, 7 and 28 days. The results are listed in
5 Table 4.
Table 4: Testing results after hardening in air and fresh water

Concrete Mix No 1 2 3 4 5 6 7 8 9
Compressive strength 30.8 25.1 16.2 19.0 12.4 16.1 7.2 13.2 5.2
MPa after 1 day in air at
20°C
Compressive strength 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1
MPa after 7 days in water,
20° C
Compressive strength MPa 48.1 44.4 33.7 38.7 27.3 33.1 20.2 27,8 16.1
after 28 days in water, 20° C
Compressive strength MPa 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1
after 28 days in water,
5°C
Flexural strength, MPa 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5
after 28 days' in water,
5°C
Comments: Grey shades mark results for concrete with anhydrite
14

WO 2006/038013—

P€T/CB2005/00385»

Hardened concrete in sea water
The compressive and flexural strength of concrete cured in both fresh and sea water are given in Table 5. Grey shades mark results for concrete with
5 anhydride. "-" indicates disintegrated concrete.

15

pCTG02oo5/oo3859
Table 5: Testing results after hardening in air, fresh water and sea water

Concrete Mix No 1 2 3 4 5 6 7 8 9
Compressive strength 30.8 25.1 16.2 19.0 12.4 16.1 7.2 13.2 5.2
MPa after 1 day in air at
20°C
Compressive strength 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1
MPa after 7 days in fresh
water, 20° C
Compressive strength MPa 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1
after 28 days in
freshwater, 5° C
Compressive strength MPa 45.7 43.7 30.5 37.4 22.9 31.8 9.9 27.1 6.4
2 months in seawater, 5°C
Compressive strength 48.4 45.2 24.3 37.0 12.8 31.8 1.1 27.8 _.
MPa 3 months in sea
water, 5°C
• Compressive . strength 49.9 45.3 12.1 37.8 6.4 34.0 _ 28.1 _
MPa 4 months in sea
water, 5°C
Compressive strength 49.5 _ _
MPa 5 months in sea
water, 5CC
Compressive strength _ .
MPa 12 months in sea
water 5°C
Flexural strength MPa 28 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5
days in freshwater, 5°C .
Flexural strength MPa 28 6.5 5.6 3.6 5.1 3.5' 4.6 2.7 3.9 2.3
days in seawater, 5°C |i
-16-

PCT/GD2005/0038SS)

Flexural strength MPa 2 6.3 5.8 3.7 5.5 3.1 5.0 1.8 4.2 1.2
months in seawater, 5°C 4
Hardened concrete in concentrated sea water (salt water)
Compressive strength of concrete stored in concentrated (5x) sea water is given
5 in Table 6.
Table 6: Testing results after hardening in air, fresh water and salt water

Concrete Mix No 1 2 3 4 5 6 7 8 9
Compressive strength 30.8 25.1 16.2 19.0 12.4 16.1 7.2 13.2 5.2
MPa after 1 day in air at
20°C
Compressive strength 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1
MPa after 7 days in fresh
water, 20° C
Compressive strength MPa 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1
after 28 days in
freshwater, 5° C.
Compressive strength MPa 44.7 41.7 29.2 33.9 23.6 3.0.1 15.5 25.1 13.2
28 days in salt water, 5°C
Compressive strength 47.2 42.5 20.7 35.5 21.8 30.1 12.7 25.5 9.3
MPa 2 months in salt ■
water, 5°C
Compressive strength 45.9 42.5 17.6 34.9 10.8 28.1 4.1 26.4 2.0
MPa ,3 months in salt
water, 5°C
- 17-

WO 2006/038018 PCT/GD2005/003859
17

Compressive strength MPa 4 months in salt water, 5°C 44.3 41.4 14.4 34.8 7.4 26.0 13/2 25.8 16/2
Compressive strength MPa 12 months in salt water, 5°C
Flexural strength MPa 28 days in freshwater, 5°C 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5
Flexural strength MPa 28 days in a salt water, 5°C 6.5 6.0 3.4 5.1 3.2 4.7 2.7 4.0 2.3
Flexural strength MPa 2 months in salt water, 50C 5.8 6.2 3.6 5.3 3.0 5.0 2.1 4.7 1.5
Comments: Grey shades mark results for concrete with anhydrite
Discussion
Concrete cured in fresh water
The development of compressive strength after 28 days curing versus
5 water/cement ratio is shown in Fig. 1 and compared with results from Norcem. The concrete with limestone filler as well as the concrete with limestone filler . and gypsum are close to the reference mixes.
Concrete cured in sea water
All the concrete cubes (and prisms) were stored their moulds in
10 laboratory conditions the first day and thereafter hardened in fresh water up to seven days. Then the prisms were placed in seawater (5°C to 9°C) and tested 1, 2, 3, 4, 5 and 12 months after casting. Fig. 2 shows the results with limestone filler only while Fig. 3 depicts the result with limestone filler and. anhydrite in stoechiometric ratio with respect to Thaumasite formation.
18
W£-300(i/038018 PQT/GB2005/003859
Addition of limestone as the only additive has not yet (within the test period) given any significant deterioration, even for the most permeable and porous concrete.
The addition of both limestone filler and anhydrite to the concrete has
5 caused increasing disintegration with increasing amount of additives. Concrete specimens with 60 and 80% limestone filler of cement weight were totally destroyed after 3 months.
Table 7: Strength development after hardening in freshwater and sea water

Concrete Mix No 1 2 3 4 5 6 7 8 9
Compressive strength MPa. 7 days in fresh water, 20° C 42.0 37.1 27.3 33.1 22.6 27.9 15.9 23.6 13.1
Compressive strength MPa 28 days in freshwater, 5° C 46.5 43.2 31.5 36.9 26.6 31.6 18.9 26.7 15.1
Compressive strength MPa 28 days in salt water, 5°C 45.7 41.1 30.5 35.8 25.1 30.1 17.8 25.8 13.6
Strength sea water 28 days/Strength fresh water 28 days 0.98 0.95 0.97 0.97 0.94 0.95 0.94 0.97 0.90
Flexural strength MPa 28 days in freshwater, 5°C 5.9 5.2 3.5 5.2 3.4 4.0 2.7 4.0 2.5
Flexural strength MPa 28 days in sea water, 5°C 6.5 5.6 3.6 5.1 3.5 4.6 2.7 3.9 2.3
Strength sea water 28 days/Strength fresh water 28 days 1.10 1.08 1.03 0.98 1.03 1.15 1.00 0.98 0.92
Comments: Grey shades mark results for concrete with anhydrite
19

WO2006/038018

PCI/CB2005/003859

19^
Compressive strength deterioration is less than 10% for all mixes during the three first weeks of exposure to sea water, which make them suitable as anchors for the seabed logging period.
The flexural strength was higher after three weeks exposure in sea
5 water, except for the cement with the highest amount of limestone filler and anhydrite.
Concrete cured in concentrated sea water
There was only a small difference in deterioration between sea water and concentrated (5x) sea water for mixes with anhydrite. Since the specimen
10 without anhydrite in natural seawater did not deteriorate, it is difficult to say whether the concentrated seawater increases the deterioration rate or not, but the compressive strength was somewhat lower after storage in concentrated sea water as seen by comparing results in Table 5 and 6.
Including limestone filler (i.e. calcium carbonate) in the recipe did not
15 deteriorate the hardened concrete within 6 months after submersion in
seawater.
To speed up the deterioration, tests were also performed by adding calcium carbonate and anhydrite in a stochiometric ratio with respect to Thaumasite that deteriorates the binder totally. These specimens disintegrated
20 in contrast to the specimen without anhydrite.
Increasing the amount of additives decreased the 7 and 28 days compressive strength for concrete hardened in fresh water.
Preferred Physical Form
Referring to figures 4 to 8 of the drawings, the anchor comprises
25 a body 10 with legs 11. The presence of two inclined surfaces 14 located on
each side of the anchor results in the rotation of the anchor during sinking.
Further, there is a hole 12 suitable for attaching a central release mechanism
20

WO 2006/038018 PCF/GB2003/00385r
(not shown). Slots 13 are introduced in the body of the anchor, to stabilise the anchor during sinking.
Specific Preferred Embodiment
A recommended concrete composition with 40% limestone filler and a
5 stoechiometric ratio of anhydrite with respect to Thaumasite was found to disintegrate in seawater after 4 months. The composition of the recommended concrete is:

Ingredients in kg/m Producer Recipe 1 Recipe 2
Rapid Portland Cement Norcern 210 210
Free water 195 195
Limestone filler Verdal Kalkverk 85 85
Anhydrite Outocompu, Odda 110 110
Sand 0-8 mm Norstone, Ardal 880 920
Sand 0-4 mm Froseth, local deposite 40 0
Crushed stone 8-16 mm Verdal Kalkverk 880 880
The concrete contains no ingredients harmful to the marine environment it is
10 meant to serve in. All ingredients are found in natural gravel, limestone and/or seawater. The concrete does not contain any organic admixtures. The anchor is characterised in that its physical form causes it to rotate during sinking by means of the presence of inclined surfaces located along each side of the anchor.
21
WO 2006/038018

P€T/GD2005/00383r

We claim:
1. A Portland cement formulation comprising amorphous calcium silicate,
the formulation additionally comprising calcium carbonate and a source of
5 sulphate.
2. A formulation as claimed in Claim 1, in which the calcium carbonate
content is in the range 10 to 50 wt% of the formulation.
10 3. A formulation as claimed in Claim 1 or Claim 2, in which the calcium carbonate is in the form of limestone, chalk or calcite.
4. A formulation as claimed in any preceding Claim, in which the sulphate
content is in the range 6 to 50 wt% SO42" of the formulation.
15
5. A formulation as claimed in any preceding Claim, in which the sulphate
is in the form of a metal sulphate.
6. A formulation as claimed in Claim 5, in which the metal sulphate is a
20 calcium sulphate.
7. A formulation as claimed in Claim 6, in which the calcium sulphate is
anhydrite.
25 8. A formulation as claimed in any preceding Claim, including in which
the calcium carbonate and source of sulphate are present in amounts which give rise to a molar ratio of S042/C032'of between 0.2 and 3.0.

22
WO2006/(B8et* PGT/GB3005/0038S9
9. A formulation as claimed in any preceding Claim, including in which the calcium carbonate and source of sulphate are present in a stoichiometric ratio with respect to thaumasite.
5 10. A formulation as claimed in any preceding Claim, further including calcium hydroxide.
11. A formulation as claimed in Claim 10, in which the calcium hydroxide
content is in the range 2 to 40 wt % of the formulation.
10
12. A formulation as claimed in. any preceding Claim which includes no
additives which would not decompose into components occurring naturally in
the environment.
15 13. A formulation as claimed in any preceding claim which includes no organic admixtures.
14. A concrete formulation, comprising a cement as claimed in any
preceding Claim, mixed with an aggregate.
20
15. A concrete formulation, comprising a cement as claimed in Claim 14, h
which the aggregate is a light weight aggregate.
16. A formulation as claimed in any of Claims 14 to 15, in which the
25 aggregate represents 0 to 80 wt % of the concrete formulation.
17. A formulation as claimed in any of Claims 14 to 16, in which the
particle size of the aggregate is less than 50 mm.

23

18. A formulation as claimed in any of Claims 14 to 17, in which the aggregate material is filler, sand, limestone with particle size greater than 1 mm or gravel.
19. An anchor for releasably tethering a submarine device at the seabed, made substantially from a formulation as claimed in any preceding Claim.
20. An anchor as claimed in Claim 19, further including at least one handle for the attachment of a release mechanism.
21. An anchor as claimed in Claim 20, in which the handle is made from a natural and environmentally non-polluting material.
22. An anchor as claimed in Claim 21, in which the handle is made from wood, or leather.
23. An anchor as claimed in Claim 19, further including a central hole for a central release mechanism.
24. A method of tethering a submarine device at the seabed, which comprises: forming an anchor by mixing a cement or concrete formulation as claimed in any of Claims 1 to 13 or 14 to 18, respectively, with water; allowing the mixture to harden to form a finished anchor; attaching the submarine device to the anchor; and deploying the anchor and submarine device at a required location at the seabed.
25. A method as claimed in Claim 24 combined with the further steps of releasing the submarine device from the anchor and allowing the anchor to disintegrate as a result of a chemical reaction between the calcium silicate, the calcium carbonate and the source of sulphate, in the presence of water, to produce thaumasite.
30
Dated this 05th Day of May, 2007

OMANA RAMAKRISHNAN
Of K &S PARTNERS
35 AGENT FOR THE APPLICANT(S)

24

ABSTRACT
CONTROLLED DETERIORATION OF NON-REINFORCED CONCRETE ANCHORS
A concrete formulation, which undergoes controlled deterioration in water, that can be used for making anchors for releasably tethering submarine devices at the seabed. The anchor may have handles for a device release mechanism or a central hole for a central device release mechanism. The formulation includes additives, which cause the cement to transform into non-binding Thaumasite over a pre-set period of time, leaving only natural material on the seafloor.

25

Documents:

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Patent Number

277910

Indian Patent Application Number

669/MUMNP/2007

PG Journal Number

51/2016

Publication Date

09-Dec-2016

Grant Date

06-Dec-2016

Date of Filing

07-May-2007

Name of Patentee

ELECTROMAGNETIC GEOSERVICES AS

Applicant Address

Stiklestadveien 1, N-7041 Trondheim,

Inventors:

#	Inventor's Name	Inventor's Address
1	ELLINGSRUD SVEIN	Tyholt Alle 9A, N-7052 Trondheim
2	SODAL AUDUN	Hasselbakkveien 10, N-7053 Ranheim
3	RECHSTEINER HANS	Askeladdvn. 20A N-7056 Ranheim
4	JUSTNES HARALD	Gisle Johnsons Gate 6, N-7042 Trondheim
5	JOHANSEN KARE INGVAR	Arnljot Johnstads vei 56, N-2312 Ottested

PCT International Classification Number

C04B28/04

PCT International Application Number

PCT/GB2005/003859

PCT International Filing date

2005-10-07

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0422426.7	2004-10-08	U.K.