NZ532133A

NZ532133A - Sealing composition and its use for sealing rock or soil

Info

Publication number: NZ532133A
Application number: NZ532133A
Authority: NZ
Inventors: Peter Greenwood; Inger Jansson; Ulf Skarp
Original assignee: Akzo Nobel Nv
Priority date: 2001-10-18
Filing date: 2002-09-23
Publication date: 2005-09-30
Also published as: HK1071394A1; NO20042047L; CN1571826A; BR0213278B1; ZA200402800B; BR0213278A; CN1264950C; CA2463638A1; MY131479A; JP4243337B2; CA2463638C; AR036828A1; KR20030032847A; KR100543613B1; WO2003033618A1; JP2005505680A; EP1436357A1; AU2002337551B2

Abstract

Use of a sealing composition for sealing rock or soil, wherein the sealing composition is obtainable by mixing a silica sol and at least one gelling agent, wherein the silica sol has an S-value higher than about 72%; a method for cutting off a liquid flow in a leaking part or cavity by inserting the sealing composition; and a method for preparing the sealing composition and a composition obtainable from the method is disclosed.

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number 532133 532 WO 03/033618 PCT/SE02/01723 1 Sealing composition and its use The present invention relates to the use of a composition for sealing rock and soil. The invention also relates to a method for cutting off the flow of liquid in a leaking part or cavity. The invention also relates to a method for preparing the sealing 5 composition and a sealing composition obtainable from said method. Background of the invention The requirements and performance of compositions used for sealing rock and soil have increased in the course of time. These requirements involve both improved 10 environmental and technical aspects. Previously, various plastics and polymers involving toxic substances have been employed to seal water leaks in e.g. concrete walls, tunnels, or cavities formed on the back side of a concrete wall. Such sealing chemicals have in a number of cases caused contamination of groundwater and health problems to e.g. construction workers handling them. However, attempts have been made to replace 15 hazardous products with more environmentally adapted ones. New products have also been sought for to meet the recently imposed leakage restrictions. In some instances, water leakage levels below 1 litre/(min*100 meters) have been the upper threshold on constructions sites of tunnels. This have forced the suppliers to provide technically improved sealing products. US 5,396,749 describes a method for cutting off water flow by 20 grouting whereby troubles due to water leakage and collapse of ground is prevented. The cut-off agent is prepared by mixing e.g. colloidal silica, inorganic salt, and a water-soluble urethane polymer. ;However, the strength of these agents has shown to be insufficient in several applications, particularly where the agent during injection and gelling is exposed to a high 25 water pressure. Especially unstable agents have during the ageing phase resulted in a fairly low long term strength. Sealing agents have also been used for sealing soil to prevent leakage of contaminants in subterranean areas like buried sources, waste dumps etc. US 5,836,390 describes a method of forming subsurface barriers where a viscous liquid comprising e.g. poiybutenes, polysiloxanes, and colloidal silica is injected. 30 It is desirable to, provide an environmentally adapted liquid cut-off agent having a high long term strength, especially in the field of sealing rock, where the cut-off agents may be subjected to high water pressure from groundwater. It is also desirable to provide durable products which resist washout forces and having a low permeability, i.e. impermeable to water and other liquids. ;35 It is an object of the present invention to provide such products solving the drawbacks of the prior art referred to above. ;WO 03/033618 ;2 ;PCT/SE02/01723 ;The invention ;The present invention relates to the use of a sealing composition for sealing rock or soil, which sealing composition is obtainable by mixing a silica sol having an S-value 5 higher than about 72% and at least one gelling agent. ;The invention also relates to a method for cutting off a liquid flow in a leaking part or cavity wherein the sealing composition, obtainable by mixing a silica sol having an S-value higher than about 72% and at least one gelling agent, is inserted into a leaking part or cavity. ;10 The present invention also relates to a method for preparing a sealing composition, which comprises mixing a silica sol having an S-value higher than about 72% and at least one gelling agent. The present invention also relates to a sealing composition obtainable by this method. ;It has been surprisingly found that a silica sol having a high S-vaiue, i.e. an S-15 value higher than about 72%, can impart a high long term gel strength to a sealing composition. The term "gel strength" as used herein is a measure of the shear and compressive strength of the gelled sealing composition that develops with time. A high long term strength provides a durable sealing. It has also been found that the sealing composition according to the present invention has a low permeability, which indicates 20 good sealing characteristics. ;The "S-value" characterises the extent of aggregation of the silica particles in the silica sol, i.e. the degree of aggregate or microgel formation. The S-value of the silica sol has been measured and calculated according to the formulas given in Her, R.K. & Dalton, R.L. in J. Phys. Chem. 60(1956), 955-957. ;25 The S-value is dependent on the silica content, the viscosity, and the density of the silica sol. A high S-value indicates a low microgel content The S-value represents the amount of Si02 in percent by weight present in the disperse phase of the silica sol. The degree of microgel can be controlled during the production process of silica sols as further described in e.g. US 5368833. ;30 According to one preferred embodiment of the invention, the S-value is higher than about 73%, preferably higher than about 74%, even more preferably higher than about 75%. Preferably, the S-value is lower than about 90%, and most preferably lower than about 85%. ;The silica sol comprises silica particles suitably having an average particle diameter 35 ranging from about 3 to about 150 nm, preferably from about 12 to about 50 nm, and most preferably from about 12 to about 40 nm. Suitably, the silica particles have a specific surface area of from about 20 to about 900, preferably from about 40 to about 230, and ;WO 03/033618 PCT/SE02/01723 ;3 ;most preferably from about 60 to about 220 m2/g. The density of the silica sol suitably is from about 1 to about 1.6, preferably from about 1.1 to about 1.5, and most preferably from about 1.2 to about 1.4 kg/m3. ;The silica sol is suitably substantially monodisperse, i.e. having as narrow particle 5 size distribution as possible. Suitably, the silica particles have a relative standard deviation of the particle size distribution lower than about 15% by numbers, preferably lower than 10% by numbers, and most preferably lower than about 8% by numbers. The relative standard deviation of the particle size distribution is the ratio between the mean particle size by numbers and the standard deviation of the particle size distribution. The silica particles of the 10 silica sol are suitably dispersed in water in presence of stabilising cations such as K+, Na+, Li+, NH4+ or the like or mixtures thereof. However, also other dispersions such as organic solvents, e.g. lower alcohols, acetone or mixtures thereof may be used. The pH of the dispersion suitably is from about 1 to about 12, preferably from about 7 to about 11. As long as the silica sol remains stable, i.e. substantially without any aggregation or gelation, a 15 high silica content is preferred in the silica sol. This is beneficial in view of the superior technical performance of a highly concentrated silica sol and the reduced transportation cost thereof. According to one embodiment, the ingredients, i.e. the silica sol and the gelling agent are separately added to the applied point to be sealed. This may be performed e.g. by means of so called jet grouting, wherein the ingredients are mixed in 20 situ, e.g. in the soil. ;By the terms "silica sol" and "silica particle" are herein also meant to comprise e.g. aluminium-modified silica particles and sols, and boron-modified silica particles and sols. Boron-modified silica sols are described in e.g. US 2,630,410. Aluminium modified silica sols, sometimes also referred to as aluminate modified silica sols, can be prepared 25 by adding an appropriate amount of aluminate ions, AI(OH)4, to a conventional non-modified silica sol under agitation and heating. Suitably, a diluted sodium or potassium aluminate solution corresponding to an aluminium modification of from about 0.05 to about 2, preferably from about 0.1 to about 2 Al atoms/nm2 surface area of the silica particle is used. The aluminium-modified silica particles comprise inserted or exchanged 30 aluminate ions, creating aiuminosilicate sites having a fixed negative surface charge. The pH of the aluminium-modified silica sol can be adjusted, preferably by means of an ion exchange resin, suitably to a pH ranging from about 3 to about 11, preferably from about 4 to about 10. The aluminium modified silica particles suitably have an Al203 content of from about 0.05 to about 3 wt%, preferably from about 0.1 to about 2 wt%. The procedure 35 of preparing an aluminium modified silica sol is further described e.g. in "The Chemistry of Silica", by Her, K. Ralph, pages 407-409, John Wiley & Sons (1979) and in US 5 368 833. ;WO 03/033618 ;PCT/SE02/01723 ;4 ;The gelling agent suitably is an inorganic salt or acid, an organic salt such as sodium acetate, or acid such as acetic acid, but preferably an inorganic salt such as potassium chloride, calcium chloride, sodium chloride, magnesium chloride, magnesium sulphate, potassium iodide magnesium nitrate, sodium nitrate, potassium nitrate, calcium 5 nitrate, and sodium silicate or mixtures thereof, preferably calcium chloride, sodium chloride or potassium chloride, and most preferably sodium chloride, sodium aluminate. ;A gel time regulator such as an acidic triacetine (glycerine triacetate), diacetine, Glauber's salt (NaS04*10H20), sulphuric acid, phosphoric acid or mixtures thereof may also be added to the sealing composition to control the gelation thereof. 10 The term "gel time", as used herein, means the amount of time elapsed from the moment of mixing the ingredients making up the sealing composition until the time when the sealing composition becomes too viscous to move or insert to a leaking point. The viscosity is suitably controlled in such way that a homogeneous moving front of the composition is formed moving in the direction of the point to be sealed. Suitably, the initial 15 viscosity of the sealing composition Is from about 3 to about 100, preferably from about 4 to about 30 mPas. The gel time may easily be controlled by adjustment of the amount of gelling agent. Sometimes, instantaneous gelling without substantial dilution of the composition is necessitated to provide a gelled pressure-resisting sealing composition. A short gel time may be optimal in cracks being relatively ground and where the risk for 20 rapid dilution of the sealing composition exists. In some cases, it is essential especially in cracks that the gelling preferably should not start before the front of the inserted composition has fully penetrated the crack. Usually, the gel time ranges from about 1 to about 120, preferably from about 2 to about 60, more preferably from about 5 to about 40, and most preferably from about 5 to about 20 minutes in rock sealing. In soil sealing, the 25 gel time usually ranges from about 5 minutes to about 24 hours, preferably from about 10 minutes to about 6 hours, and most preferably from about 15 minutes to about 3 hours. The ingredients may be mixed at ambient temperature. The gelling agent is suitably added to the silica sol in an aqueous solution in a concentration from about 1 to about 30 wt%, preferably from about 2 to about 15 wt%. The silica sol, to which the 30 gelling agent suitably is added, suitably has a silica content of from about 1 to about 70, preferably from about 20 to about 60, and most preferably from about 35 to about 50 wt%. A high silica content in the silica sol may in many instances be favourable due to reduced transportation costs of silica sol. The silica content in the sealing composition suitably is from about 1 to about 60, 35 preferably from about 15 to about 50, and most preferably from about 30 to about 45 wt%. A high silica content minimises shrinkage and maximises long term strength. The weight ratio of silica to gelling agent depends on the application and may vary depending WO 03/033618 PCT/SE02/01723 5 on the application. Suitably, the weight ratio of silica particles: gelling agent is from about 400:1 to about 10:1, preferably from about 200:1 to about 20:1. The gelling agent content in the sealing composition may vary depending on the type of gelling agent used. However, the gelling agent content suitably is from about 0.1 5 to about 10, preferably from about 0.2 to about 5 wt% of the composition. If sodium chloride is used as gelling agent, the content suitably is from about 0.2 to about 5, preferably from about 1 to about 3, and most preferably from about 1.5 to about 2 wt% of the composition. If calcium chloride is used as gelling agent, the content suitably is from about 0.1 to about 2, preferably from about 0.2 to about 1, and most preferably from 10 about 0.25 to about 0.5 wt% of the composition. According to a preferred embodiment, the sealing composition is inserted by injecting the silica sol separately to a leaking part or cavity whereby the sealing composition is formed in situ, e.g. in a crack of a rock or a cavity in the soil. The gelling agent may thus also be separately injected to the leaking part or cavity. This may be 15 performed e.g. by injecting the sealing ingredients simultaneously, e.g. by placing injection nozzles for the silica sol and the gelling agent in parallel such that the gelling agent and the silica sol can be injected at the same time without premixing. However, in certain leaking parts or cavities, e.g. in soil, a gelling agent in the form of e.g. a salt may already be present in the soil in such quantity that no further gelling agent need to be 20 added to form a sealing composition. Hence, in one preferred embodiment of the invention, solely silica sol is separately injected to a leaking part or cavity. The method can generally impart cutting off of any liquid flow of e.g. water and aqueous solutions, organic solutions etc, but the method is principally adapted to cut off flow of water and aqueous solutions. 25 The sealing composition may also be inserted to a leaking part or cavity by means of other methods such as jet grouting, in which at least a part of the material constituting the leaking part or cavity is removed to add the sealing composition and then reset to the same point from which it was earlier removed with the sealing composition incorporated therein. This method is preferably adapted to be used in the sealing of soil. 30 According to one preferred embodiment, the silica sol and the gelling agent are mixed immediately before injection, in this context, the wording "immediate" means from about 0 to about 30 seconds, preferably from about 0 to about 15 seconds. This way of mixing the ingredients of a composition is often referred to as in-line mixing. According to one preferred embodiment, the sealing composition may also be 35 prepared in a batch process in advance and used suitably within 60 minutes, and preferably within 30 minutes before insertion of the composition. This way of preparing the sealing composition, however, necessitates a sufficiently stable sealing composition WO 03/033618 PCT/SE02/01723 6 that can be stored without substantial gelling until the moment of insertion. The injection time of the sealing composition is suitably from about 1 minute to about 1 hour, preferably from about 5 minutes to about 30 minutes. The injection /penetration depth varies of course with the leak to be sealed. However, the method of the present invention is 5 particularly beneficial for depths from about 0.5 to about 50 metres, preferably from about 5 to about 30 metres. The injection pressure suitably is from about 1 to about 50 bar, preferably from about 2 to about 25 bar. The sealing composition is principally adapted to provide barriers in the subsurface for preventing leakage of water. The sealing of rock involves insertion of the 10 sealing composition into e.g. a cavity such as a microcrack, especially to control groundwater leakage, e.g. in tunnels. By the term "microcrack" is usually meant a cavity having a diameter lower than 20 jjm. As the diameter of the silica particles in the silica sol is from about 10 to about 100 nm, sealing compositions containing such silica particles are of course suitable for injection into microcracks. 15 The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the gist and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims. The following examples will further illustrate how the described invention may be performed 20 without limiting the scope of it. Example 1 Sealing compositions were prepared from a salt solution of 1.7 M sodium chloride which was added under agitation to 200 g of different silica sol products as 25 defined in the tables below. The amount of salt solution added was 40 g solution in all compositions. The compositions were aged up to 672 hours to evaluate the long term shear strength. In table 1, one set of the compositions was exposed to an increased temperature of 55 °C and another set was exposed to a pH of 12 to accelerate the ageing of the sealing composition. The calculation of the particle diameter of the silica particles 30 was made by Sear's method for calculating the specific surface area. The shear strength test was performed with the fall cone test according to the Swedish Standard SS 02 71 25. Also the compressive strength was determined for the sealing compositions. This was made by compression tests in which a load-frame, a pressure-head with the 35 same diameter as the sample, a load cell with a plane surface where the sample is placed between the load-cell and the pressure-head, a displacement transducer, a battery powered data-logger, a signal processing software were used. The load frame WO 03/033618 PCT/SE02/01723 7 forces the pressure-head to move in vertical direction. The frame is of same type as used in machine shops for controlled vertical drilling. The load is controlled by weights, which loads the load-head without any transmission (dead weight). The pressure-head consists of a rigid steel cylinder with 50 mm diameter. The load-cell has a capacity for 300 kg. The 5 load-cell forms a plane surface. The sample is situated between the load-cell and the pressure-head. The accuracy for the load-cell is within 0.1 kg. The displacement transducer has a stroke capacity of 5 mm. The error of the actual transducer was tested by the factory to max 0,4%. The data-logger used for the tests is developed to monitor vibrations and deformations during field conditions. The logger monitors continuously 10 during the test. The compression tests were performed only for samples cured during 28 days. The mould-cylinders size was 50 mm diameter and 25 mm height. The mould cylinders were positioned in a pot with a plane bottom. The sealing composition was then poured up to the upper end of the cylinders. All samples were cured in 20° C water bath at pH 10. Only the cross sections where exposed to water. Before testing, the samples 15 were separated from the mould-cylinders. Table 1 Compositions made with the following sols: Particle diameter (nm) S- value Surface area on product base (m2/g) Shear strength (kPa), 55 °C, pH 10, 672 h Shear strength (kPa), 20°C, pH 12, 672h SoM 17 77 68 326 - Sol 2 12 76 88 640 475 Sol 3 11 70 100 218 - Sol 4 7 70 108 250 70 Sol 5 5 45 75 48 39 20 In table 1, it can be seen that the sealing compositions made from silica sols having an S-value according to the invention results in a higher gel strength after 672 hours than the composition prepared from the comparative silica sols 3-5, both at ambient temperature and at a pH of 12 (which accelerates the ageing of the products) 25 and at a pH of 10 and a temperature of 55 °C (which also results in a faster ageing process). 30 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> WO 03/033618 8 Table 2 PCT/SE02/01723 Compositions made from the following sols: Particle diameter (nm) S-value Surface area on product base (m2/g) Compressive strength (kPa)/max load Sol 6 35 90 40 48 SoM 17 77 68 50 Sol 2 12 76 88 45 Sol 3 11 70 100 11 Sol 5 5 45 75 11 In table 2, it can be seen that the sealing compositions prepared from the silica 5 sols with an S-value in accordance with the present invention impart higher compressive strength than the sealing compositions made from the comparative silica sols 3 and 5. 18/03/2004 03:01 4686441645 17/03/2004 15:54 EKfi CHEMICfiLS PfiTENT DEPT. -> 0064 4 381 60 51 NR.573 I the Swedish Patent Office IPC j PCT Internationa) Application PCT/SE02/01723 24-10-2003 ' 9 Claims

1. Use of a sealing composition for sealing rode or soil, wherein said sealing composition is obtainable by mixing a silica sol having an S-vaJue higher than about 72% 5 and at least one gelling agent.

2. Method for cutting off a liquid flow in a leaking part or cavity by inserting a sealing composition, said sealing composition being obtainable by mixing a silica sol having an S-value higher than about 72% and at least one gelling agent, into the leaking part or cavity. 10

3. Method for preparing a sealing composition by mixing a silica sol having an S-value higher than about 72% and at least one gelling agent.

4. Method according to claim 3, wherein the silica sol and the gelling agent are mixed in situ in a leaking part or cavity by separately injecting the silica sol to said leaking part or cavity. 15

5. Sealing composition obtainable by mixing a silica sol having an S-value higher than about 72% and at least one gelling agent.

6. Sealing composition according to claim 5, wherein the S-value is higher than about 75%.

7. Sealing composition according to claims 5-6, wherein the silica sol is an 20 aluminium modified silica sol.

8. Sealing composition according to any of claims 5-7, wherein the composition has a silica content from about 35 to about 50 wt%.

9. Sealing composition according to any of claims 5-8, wherein the gelling agent is selected from potassium chloride, sodium chloride, calcium chloride, magnesium 25 chloride, magnesium nitrate, magnesium sulfate or mixtures thereof.

10. Sealing composition according to any of claims 5-9, wherein the composition has a relative standard deviation of the' particle size distribution lower than about 15% by numbers.

11. Sealing composition according to any of claims 5-10, wherein the 30 composition has a gelling agent content from about 0.2 to about 5 wt%.

12. Sealing composition according to any of claims 5-11, wherein the silica sol comprises silica particles having a specific surface area from about 40 to about 230 m2/g.

13. Sealing composition according to any of claims 5-12, wherein the composition has a weight ratio of silica particles to gelling agent from about 400:1 to 35 about 10:1. AMENDED SHEET 18/03/2004 03:02 4686441645 17/03/2004 15:54 ERA CHEMICALS PATENT DEPT. 0064 4 381 60 51 NR.573 The Swedish Patent Office PCT International Application PCT/SE02/01723 24-10-2003 10

14. Sealing composition according to any of claims 5-13, wherein the composition contains silica particles having a size within the range of from about 12 to about 50 nm. AMENDED SHEET 11 A use according to claim 1, substantially as herein described or exemplified. A method according to claim 2, substantially as herein described or exemplified. A method according to claim 3, substantially as herein described or exemplified. A sealing composition according to claim 5, substantially as herein described or exemplified. END OF CLAIMS </div>