CA2158501C - Rapid-setting cementitious composition - Google Patents
Rapid-setting cementitious composition Download PDFInfo
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- CA2158501C CA2158501C CA002158501A CA2158501A CA2158501C CA 2158501 C CA2158501 C CA 2158501C CA 002158501 A CA002158501 A CA 002158501A CA 2158501 A CA2158501 A CA 2158501A CA 2158501 C CA2158501 C CA 2158501C
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- cement
- malate
- citramalate
- water
- weight
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- 239000000203 mixture Substances 0.000 title claims abstract description 74
- 239000004568 cement Substances 0.000 claims abstract description 50
- 229940049920 malate Drugs 0.000 claims abstract description 19
- 239000011396 hydraulic cement Substances 0.000 claims abstract description 17
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims abstract description 16
- -1 Alkali metal citrates Chemical class 0.000 claims abstract description 9
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 8
- XFTRTWQBIOMVPK-UHFFFAOYSA-L citramalate(2-) Chemical compound [O-]C(=O)C(O)(C)CC([O-])=O XFTRTWQBIOMVPK-UHFFFAOYSA-L 0.000 claims abstract 12
- BJEPYKJPYRNKOW-UHFFFAOYSA-N malic acid Chemical compound OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 13
- SVICABYXKQIXBM-UHFFFAOYSA-L potassium malate Chemical group [K+].[K+].[O-]C(=O)C(O)CC([O-])=O SVICABYXKQIXBM-UHFFFAOYSA-L 0.000 claims description 5
- 235000011033 potassium malate Nutrition 0.000 claims description 5
- KCIDZIIHRGYJAE-YGFYJFDDSA-L dipotassium;[(2r,3r,4s,5r,6r)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl] phosphate Chemical compound [K+].[K+].OC[C@H]1O[C@H](OP([O-])([O-])=O)[C@H](O)[C@@H](O)[C@H]1O KCIDZIIHRGYJAE-YGFYJFDDSA-L 0.000 claims description 3
- 239000012530 fluid Substances 0.000 claims 2
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 239000011378 shotcrete Substances 0.000 abstract description 7
- 150000004701 malic acid derivatives Chemical class 0.000 abstract description 4
- BJEPYKJPYRNKOW-UHFFFAOYSA-L malate(2-) Chemical compound [O-]C(=O)C(O)CC([O-])=O BJEPYKJPYRNKOW-UHFFFAOYSA-L 0.000 abstract 1
- XFTRTWQBIOMVPK-UHFFFAOYSA-N citramalic acid Chemical compound OC(=O)C(O)(C)CC(O)=O XFTRTWQBIOMVPK-UHFFFAOYSA-N 0.000 description 19
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 16
- 239000003795 chemical substances by application Substances 0.000 description 15
- 239000004570 mortar (masonry) Substances 0.000 description 11
- 150000003839 salts Chemical class 0.000 description 11
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 description 9
- XFTRTWQBIOMVPK-YFKPBYRVSA-N Citramalic acid Natural products OC(=O)[C@](O)(C)CC(O)=O XFTRTWQBIOMVPK-YFKPBYRVSA-N 0.000 description 8
- 239000011398 Portland cement Substances 0.000 description 7
- 239000001508 potassium citrate Substances 0.000 description 7
- 229960002635 potassium citrate Drugs 0.000 description 7
- QEEAPRPFLLJWCF-UHFFFAOYSA-K potassium citrate (anhydrous) Chemical compound [K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O QEEAPRPFLLJWCF-UHFFFAOYSA-K 0.000 description 7
- 235000011082 potassium citrates Nutrition 0.000 description 7
- 239000002253 acid Substances 0.000 description 6
- 239000004615 ingredient Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000004576 sand Substances 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 238000011161 development Methods 0.000 description 5
- 229910003002 lithium salt Inorganic materials 0.000 description 4
- 159000000002 lithium salts Chemical class 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000003518 caustics Substances 0.000 description 3
- 150000001860 citric acid derivatives Chemical class 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 150000004645 aluminates Chemical class 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 229940071264 lithium citrate Drugs 0.000 description 2
- WJSIUCDMWSDDCE-UHFFFAOYSA-K lithium citrate (anhydrous) Chemical compound [Li+].[Li+].[Li+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O WJSIUCDMWSDDCE-UHFFFAOYSA-K 0.000 description 2
- 239000001630 malic acid Substances 0.000 description 2
- 235000011090 malic acid Nutrition 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229910021487 silica fume Inorganic materials 0.000 description 2
- 150000004760 silicates Chemical class 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- QXNVGIXVLWOKEQ-UHFFFAOYSA-N Disodium Chemical compound [Na][Na] QXNVGIXVLWOKEQ-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910001579 aluminosilicate mineral Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000000404 calcium aluminium silicate Substances 0.000 description 1
- 235000012215 calcium aluminium silicate Nutrition 0.000 description 1
- WNCYAPRTYDMSFP-UHFFFAOYSA-N calcium aluminosilicate Chemical compound [Al+3].[Al+3].[Ca+2].[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O WNCYAPRTYDMSFP-UHFFFAOYSA-N 0.000 description 1
- 229940078583 calcium aluminosilicate Drugs 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000013020 final formulation Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000010451 perlite Substances 0.000 description 1
- 235000019362 perlite Nutrition 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 229960003975 potassium Drugs 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000000518 rheometry Methods 0.000 description 1
- 235000019265 sodium DL-malate Nutrition 0.000 description 1
- 239000001509 sodium citrate Substances 0.000 description 1
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 1
- 235000011083 sodium citrates Nutrition 0.000 description 1
- WPUMTJGUQUYPIV-UHFFFAOYSA-L sodium malate Chemical compound [Na+].[Na+].[O-]C(=O)C(O)CC([O-])=O WPUMTJGUQUYPIV-UHFFFAOYSA-L 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000009974 thixotropic effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
- C04B24/04—Carboxylic acids; Salts, anhydrides or esters thereof
- C04B24/06—Carboxylic acids; Salts, anhydrides or esters thereof containing hydroxy groups
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/10—Accelerators; Activators
- C04B2103/12—Set accelerators
Abstract
Rapid-setting cementitious compositions comprise hydraulic cement and at least 4% by weight based on the weight of the cement of a water-soluble citrate, malate or citramalate or a mixture thereof. Alkali metal citrates, malates and citramalates are preferred. The compositions are especially useful as shotcrete.
Description
215850~
RAPID-SETTING CEMENTITIOUS COMPOSITION
The present invention relates to rapid-setting cement compositions and more particularly to the use of certain chemical compounds as quick-setting agents in the formulation of such compositions.
Rapid-setting cement compositions are desirable and widely-used materials, particularly in applications known as lining and relining construction where a continuous layer of modest thickness of a cement composition is applied to a surface. A common procedure in which rapid-setting cement compositions are used is "shotcreting", the application of concrete to a surface by spraying from a nozzle. Other applications for rapid-setting cement compositions include cement plugging compounds and quick-setting mortars. In all such usages, the cement composition must set quickly in order to retain its position as applied.
The particular quick-setting agent used in rapid-setting cement compositions will influence a number of performance criteria of interest to the industry. Not only must the agent effect a rapid setting within certain time limits, but this rapid setting is also desirably achieved with economically-attractive amounts of a quick-setting agent. In addition, the rapid development of strength properties, which does not arise simply because of the rapid setting, is an important performance criterion of a quick-setting agent. The ability to continue early strength development to a high final strength is also a desirable objective.
Quick-setting agents have traditionally been strongly alkaline solutions of silicates and aluminates, the aluminates tending to be better than the silicates in providing early strength development. Both, however, are caustic in nature, and this caustic nature gives rise to health and environmental concerns.
It is an objective in the cement art to provide alternatives to current quick-setting 2 5 agents and particularly to provide non-caustic quick-setting agents which provide rapid early strength development and other desired properties.
In accordance with the invention, it has been found that water-soluble salts of citric acid, malic acid (hydroxybutanedioc acid) and citramalic acid (2-hydroxy-2-methylbutanedioc acid), in particular alkali metal salts, are especially useful as quick-setting 3 0 agents in cementitious compositions. This is a surprising discovery as such acids and their alkali metal salts are well known in the art as cement retarders.
The invention therefore provides in one major aspect thereof rapid-setting cementitious compositions comprising hydraulic cement and at least 4% by weight of the cement of a water-soluble salt of citric acid, malic or citramalic acid or mixture thereof. These compositions will be applied in admixture with sufficient water for hydraulic setting of the cement. Both very quick setting and rapid and good strength development are obtained with the invention.
In another embodiment, the compositions of the present invention consist essentially of hydraulic cement and at least 4% by weight of the cement of a water-soluble salt of citric acid, malic or citramalic acid or mixture thereof.
A salt of citric acid, malic or citramalic acid is, for the purposes of this invention, defined as an acid molecule with all of its acid groups in salt form, i.e. a tri-salt in the case of citric acid and a di-salt in the case of malic or citramalic acid. The preferred water-soluble salt forms are the alkali metal salts, particularly the sodium, potassium and lithium salts. The particularly preferred quick-setting agents are sodium citrate, potassium citrate, disodium malate, disodium citramalate, dipotassium malate and dipotassium citramalate and mixtures thereof, with potassium citrate, dipotassium malate or dipotassium citramalate being most preferred. However, lithium salts may be preferred where the alkali-silica reaction is a concern, since it is well known that lithium salts inhibit the alkali-silica reaction.
The citric acid, malic and citramalic acid salts used in the invention may be readily prepared, or commercially-available varieties may be used. The acid salts are preferably added to the cementitious compositions as aqueous solutions, generally at concentrations of about 50% by weight of salt, although the concentration is not critical.
For the less soluble salts, e.g. lithium salts, the concentrations may be less than 50% by weight. In general, at least 4% by weight of water-soluble citrate, malate or citramalate, or mixture thereof, based on the weight of the hydraulic cement, is required to attain the quick-setting action achievable with this invention. When a citrate, malate or citramalate is employed in amounts of 4% or more, it will rapidly accelerate the setting of the cement. Substantially greater amounts up to 20% by weight or more may be employed, depending upon the final formulation, objectives and conditions of use. Desirably, at least 5% water-soluble citrate, malate or citramalate based on the weight of the cement is employed, with amounts greater than 10% being unnecessary in most applications. Preferably, the amount of citrate, malate or citramalate is in the range of 5.0 to 8.5%, more usually 5.5 to 8.0%, based on the weight of the hydraulic cement. However, the skilled person can readily ascertain the appropriate material and quantity in any given set of circumstances.
In general, the water-soluble citrates, malates and citramalates, depending largely on the amount employed, can be used to provide quick setting as desired in a variety of applications. Hence, an initial setting time of not greater than 20 minutes by ASTM
Method C266 can readily be achieved. Setting times in the range of 10 seconds to 5 minutes, preferably 30 seconds to 5 minutes, as are common in shotcreting applications, are easily targeted by the addition of water-soluble citrates, malates or citramalates in accordance with the invention. Again, this is well within the skill of the art.
The hydraulic cement employed in the compositions of the invention may be selected from the wide range of commercially-available calcium alumino-silicate mineral blends, which when mixed with water will set to form a hard product. The most common type of hydraulic cement is portland cement, i.e. types I-IV portland cement, and for purposes of the present invention, portland cement is the preferred hydraulic cement.
In addition to cement, the compositions of the invention may include other ingredients commonly present in quick-setting cement compositions and other cement additives which do not substantially interfere with the quick-setting ability of the compositions of the invention. A common ingredient of quick-setting cement composition is aggregate, especially fine aggregate such as sand and the like. Pea gravel aggregates (maximum diameter of about 0.95cm (0.375 inch)) and the like may also be used in shotcrete applications with suitable nozzles. Coarse aggregates may also be used in quick-setting applications. In typical applications, the amount of aggregate, e.g. fine aggregate such as silica sand, will be present in a weight ratio to the cement of from 0.5:1 to 6:1, more usually from 1.2:1 to 5:1, and particularly from 1.5:1 to 4.5:1. Lighter weight aggregates such as perlite and the like may also be used. A variety of other materials not classed as 2 5 aggregates may also be included. Examples are silica fume, silicones and fibers such as glass and steel fibers. Agents to provide cohesion or bonding of the applied cement composition, such as polyvinyl alcohols, may also be included.
The amount of water to be included in the quick-setting compositions of the invention will vary depending upon the particular application and other known factors, but is always sufficient for the hydraulic setting of the cement component. The amount of water used in shotcrete application is usually controlled to avoid undesired fluidity.
Hence, the amount of water in shotcrete compositions will usually vary from 20% to 60%, more usually 30%
to 45%, by weight of the hydraulic cement component. Since the water-soluble citrates, malates and citramalates have been found to have a solids dispersing effect, the amount of water may be less than that otherwise indicated for particular applications.
In other applications, greater amounts of water than used in shotcreting may be employed to provide desired fluidity. Other cement additives to maintain fluidity may also be used but in general the compositions will achieve a rapid initial set in not greater than 20 minutes, preferably no more than 15 minutes under the influence of the water-soluble citrate, malate or citramalate when employed in amounts of 4% by weight of the cement or greater.
The rapid-setting compositions and method of the invention are particularly useful in shotcrete applications. Shotcreting can be carried out using a dry mix cement composition (the dry mix system) or a wet mix cement composition (the wet mix system), as described below.
a) The dry mix system is one in which dry-mixed cement and aggregate are pneumatically conveyed through a delivery hose, with water and a quick-set agent generally being added in the vicinity of the nozzle assembly or upstream of the nozzle just prior to passage into the nozzle assembly (the quick-setting agent can be added at the point of mixing instead of vicinal to the nozzle, but this is relatively rare). The mixture is applied on to the requisite surface in the vicinity of the nozzle, by pneumatically projecting it out from the nozzle under pressure, e.g. by means of compressed air. With the dry mix system it is difficult to control the quantity of water added and therefore to control the water to cement ratio (hereinafter referred to as the W/C ratio). The method has the additional drawback that dust is generated.
b) The wet mix system is a system in which the cement and aggregate are mixed in the presence of water and the mixture pumped through a delivery hose to a nozzle and then pneumatically projected out of the nozzle, a quick-setting agent being added within the nozzle assembly or upstream of the nozzle, just prior to passage into the nozzle. There are also examples of this system where the cement composition can be pumped, rather than pneumatically conveyed, to a point midway between the point of mixing and the nozzle in the delivery hose followed by pneumatic conveying between this midpoint and nozzle. The system allows good control of W/C ratio and generates little dust.
Pressures employed in the pneumatic delivery of cement compositions in shotcreting generally range from 60 to 140 psi (413-965 KPa), and are more usually 80 to 120 psi (551-827KPa).
A particularly useful method of employing the malic or citramalic acid-based quick-setting agents of the present invention in shotcreting is to add less than an accelerating amount of a water-soluble salt of malic or citramalic acid initially upon batching of the cementitious composition and then to add an additional accelerating amount of the water-soluble salt of malic acid or citramalic acid in the vicinity of the nozzle, such as is described in United States Patent No. 5,634,972. If desired, a rheology modifying 5 material capable of imparting thixotropic properties to the cementitious composition may be added as described in the aforementioned US Patent No. 5,634,972.
The following examples merely demonstrate the invention and are not intended to limit the same. In the examples, setting time and compressive strength measurements conform to American Society for Testing and Materials Methods C 266 and C 109, respectively. All measurements were made at room temperature. In the examples, set times are determined from the time the citrate, malate or citramalate is mixed with the cement.
EXAMPLE I
The mix procedure simulates the time scale of wet-mix shotcreting, such that the mortar is premixed and the shotcrete accelerator, added at the nozzle, is mixed with the mortar only for a brief moment.
In a plastic bag, 3000 g of mortar mix (dry ingredients), which consists of 590 g of ordinaiy portland cement, 30 g of silica fume, and 2380 g of silica sand, is blended.
Approximately 75% of tL total of 206.5 g of mixing water is placed in the mixing bowl of a HobattTM lab mixer. The blended dry ingredients are then added. The mixer is started on low speed and the mortar is mixed for two minutes. During this time, the 35.4 g of potassium citrate (6% by weight of cement) is dissolved in the remaining mix water. This is added into the mixing bowl at the conclusion of the two minute initial mix cycle, and the mortar is mixed for an additional minute. The test specimens are then cast immediately.
Setting time and compressive strength measurements conform to American Society for Testing and Materials Methods C 266 and C 109, respectively, with the following results.
Setting Time @ 16 C+/-0.5 C(61 F+/-1 F) Final: 7 minutes Compressive Strength @ 16 C(61 F) MPa (PSI) 1 hour 5(730) 4 hour 12 (1709) 1 day 17 (2404) 7 day 25 (3647) 28 day 38 (5433) Example 1 is repeated except that the experiment is conducted at a temperature of 51.3 F and the amount of potassium citrate is increased to 8% by weight of the cement.
Setting time and strength properties by ASTM C266 and C 109, respectively, are as follows.
Setting Time @0.5oC+/-0.5 C(51 F+/-1 F) Final: 5 minutes Compressive Strength @ 16 C(61 F) MPa (PSI) 1 hour 5 (707) 4 hour 7 (1060) 1 day 19 (2742) 7 day 30 (4256) 28 day 41 (5856) In cement paste experiments (100 g. portland cement and 35 g. of deionized water), 5% of potassium citrate and 5% of lithium citrate (based on the weight of the cement) are individually evaluated with following set times recorded by a VicatTM needle apparatus.
Citrate Initial Set Final Set potassium citrate 240 seconds 320 seconds lithium citrate 200 seconds 280 seconds Following the general procedure of Example 1, a shotcrete mortar mix is prepared to contain 122 g. of Ashgrove Type I portland cement, 220 g. of silica sand, 40 g. of water and 7 g. of potassium citrate. The sand and cement are mixed together and then mixed with a solution of the citrate in the water. The resulting composition has an initial set of 30 seconds (ASTM C266) and a 1 hour compressive strength of 1800 psi (ASTM C109).
In a plastic bag, 2775 g of mortar mix (dry ingredients), which consists of 740 g of ordinary portland cement and 2035 g of silica sand, is blended together.
Approximately 50%
of a total of 333 g of mixing water is placed in the mixing bowl of a Hobart lab mixer.
The blended dry ingredients are then added. 44.4 g of dipotassium malate (6%
by weight of cement) is dissolved in the remaining mix water and added into the mixing bowl. The mortar is then mixed for three minutes. The test specimens are then cast immediately and determined to have the following properties:
Initial setting time: 7 minutes Final setting time: 9 minutes Compressive Strength PSI (MPa):
1 hour 673 (4.64) 4 hour 1525 (10.52) 1 day 2739 (18.89) 7 day 4411 (30.42) A mortar mix prepared in accordance with ASTM C109 is prepared to contain 8.5%
dipotassium malate based on the weight of the cement at a water to cement ratio of 0.45 and is determined to have the following properties:
Initial setting time: 4 minutes Final setting time: 6.5 minutes Compressive Strength PSI (MPa):
1 hour 863 ( 5.95) 4 hour 1840 (12.69) 1 day 3040 (20.97) 7 day 4081 (28.14) A mortar mix is prepared in accordance with ASTM C109 and contains 8% sodium citramalate based on the weight of cement at a water to cement ratio of 0.40 and is determined to have the following set times:
Initial set: 3 minutes Final set: 5 minutes
RAPID-SETTING CEMENTITIOUS COMPOSITION
The present invention relates to rapid-setting cement compositions and more particularly to the use of certain chemical compounds as quick-setting agents in the formulation of such compositions.
Rapid-setting cement compositions are desirable and widely-used materials, particularly in applications known as lining and relining construction where a continuous layer of modest thickness of a cement composition is applied to a surface. A common procedure in which rapid-setting cement compositions are used is "shotcreting", the application of concrete to a surface by spraying from a nozzle. Other applications for rapid-setting cement compositions include cement plugging compounds and quick-setting mortars. In all such usages, the cement composition must set quickly in order to retain its position as applied.
The particular quick-setting agent used in rapid-setting cement compositions will influence a number of performance criteria of interest to the industry. Not only must the agent effect a rapid setting within certain time limits, but this rapid setting is also desirably achieved with economically-attractive amounts of a quick-setting agent. In addition, the rapid development of strength properties, which does not arise simply because of the rapid setting, is an important performance criterion of a quick-setting agent. The ability to continue early strength development to a high final strength is also a desirable objective.
Quick-setting agents have traditionally been strongly alkaline solutions of silicates and aluminates, the aluminates tending to be better than the silicates in providing early strength development. Both, however, are caustic in nature, and this caustic nature gives rise to health and environmental concerns.
It is an objective in the cement art to provide alternatives to current quick-setting 2 5 agents and particularly to provide non-caustic quick-setting agents which provide rapid early strength development and other desired properties.
In accordance with the invention, it has been found that water-soluble salts of citric acid, malic acid (hydroxybutanedioc acid) and citramalic acid (2-hydroxy-2-methylbutanedioc acid), in particular alkali metal salts, are especially useful as quick-setting 3 0 agents in cementitious compositions. This is a surprising discovery as such acids and their alkali metal salts are well known in the art as cement retarders.
The invention therefore provides in one major aspect thereof rapid-setting cementitious compositions comprising hydraulic cement and at least 4% by weight of the cement of a water-soluble salt of citric acid, malic or citramalic acid or mixture thereof. These compositions will be applied in admixture with sufficient water for hydraulic setting of the cement. Both very quick setting and rapid and good strength development are obtained with the invention.
In another embodiment, the compositions of the present invention consist essentially of hydraulic cement and at least 4% by weight of the cement of a water-soluble salt of citric acid, malic or citramalic acid or mixture thereof.
A salt of citric acid, malic or citramalic acid is, for the purposes of this invention, defined as an acid molecule with all of its acid groups in salt form, i.e. a tri-salt in the case of citric acid and a di-salt in the case of malic or citramalic acid. The preferred water-soluble salt forms are the alkali metal salts, particularly the sodium, potassium and lithium salts. The particularly preferred quick-setting agents are sodium citrate, potassium citrate, disodium malate, disodium citramalate, dipotassium malate and dipotassium citramalate and mixtures thereof, with potassium citrate, dipotassium malate or dipotassium citramalate being most preferred. However, lithium salts may be preferred where the alkali-silica reaction is a concern, since it is well known that lithium salts inhibit the alkali-silica reaction.
The citric acid, malic and citramalic acid salts used in the invention may be readily prepared, or commercially-available varieties may be used. The acid salts are preferably added to the cementitious compositions as aqueous solutions, generally at concentrations of about 50% by weight of salt, although the concentration is not critical.
For the less soluble salts, e.g. lithium salts, the concentrations may be less than 50% by weight. In general, at least 4% by weight of water-soluble citrate, malate or citramalate, or mixture thereof, based on the weight of the hydraulic cement, is required to attain the quick-setting action achievable with this invention. When a citrate, malate or citramalate is employed in amounts of 4% or more, it will rapidly accelerate the setting of the cement. Substantially greater amounts up to 20% by weight or more may be employed, depending upon the final formulation, objectives and conditions of use. Desirably, at least 5% water-soluble citrate, malate or citramalate based on the weight of the cement is employed, with amounts greater than 10% being unnecessary in most applications. Preferably, the amount of citrate, malate or citramalate is in the range of 5.0 to 8.5%, more usually 5.5 to 8.0%, based on the weight of the hydraulic cement. However, the skilled person can readily ascertain the appropriate material and quantity in any given set of circumstances.
In general, the water-soluble citrates, malates and citramalates, depending largely on the amount employed, can be used to provide quick setting as desired in a variety of applications. Hence, an initial setting time of not greater than 20 minutes by ASTM
Method C266 can readily be achieved. Setting times in the range of 10 seconds to 5 minutes, preferably 30 seconds to 5 minutes, as are common in shotcreting applications, are easily targeted by the addition of water-soluble citrates, malates or citramalates in accordance with the invention. Again, this is well within the skill of the art.
The hydraulic cement employed in the compositions of the invention may be selected from the wide range of commercially-available calcium alumino-silicate mineral blends, which when mixed with water will set to form a hard product. The most common type of hydraulic cement is portland cement, i.e. types I-IV portland cement, and for purposes of the present invention, portland cement is the preferred hydraulic cement.
In addition to cement, the compositions of the invention may include other ingredients commonly present in quick-setting cement compositions and other cement additives which do not substantially interfere with the quick-setting ability of the compositions of the invention. A common ingredient of quick-setting cement composition is aggregate, especially fine aggregate such as sand and the like. Pea gravel aggregates (maximum diameter of about 0.95cm (0.375 inch)) and the like may also be used in shotcrete applications with suitable nozzles. Coarse aggregates may also be used in quick-setting applications. In typical applications, the amount of aggregate, e.g. fine aggregate such as silica sand, will be present in a weight ratio to the cement of from 0.5:1 to 6:1, more usually from 1.2:1 to 5:1, and particularly from 1.5:1 to 4.5:1. Lighter weight aggregates such as perlite and the like may also be used. A variety of other materials not classed as 2 5 aggregates may also be included. Examples are silica fume, silicones and fibers such as glass and steel fibers. Agents to provide cohesion or bonding of the applied cement composition, such as polyvinyl alcohols, may also be included.
The amount of water to be included in the quick-setting compositions of the invention will vary depending upon the particular application and other known factors, but is always sufficient for the hydraulic setting of the cement component. The amount of water used in shotcrete application is usually controlled to avoid undesired fluidity.
Hence, the amount of water in shotcrete compositions will usually vary from 20% to 60%, more usually 30%
to 45%, by weight of the hydraulic cement component. Since the water-soluble citrates, malates and citramalates have been found to have a solids dispersing effect, the amount of water may be less than that otherwise indicated for particular applications.
In other applications, greater amounts of water than used in shotcreting may be employed to provide desired fluidity. Other cement additives to maintain fluidity may also be used but in general the compositions will achieve a rapid initial set in not greater than 20 minutes, preferably no more than 15 minutes under the influence of the water-soluble citrate, malate or citramalate when employed in amounts of 4% by weight of the cement or greater.
The rapid-setting compositions and method of the invention are particularly useful in shotcrete applications. Shotcreting can be carried out using a dry mix cement composition (the dry mix system) or a wet mix cement composition (the wet mix system), as described below.
a) The dry mix system is one in which dry-mixed cement and aggregate are pneumatically conveyed through a delivery hose, with water and a quick-set agent generally being added in the vicinity of the nozzle assembly or upstream of the nozzle just prior to passage into the nozzle assembly (the quick-setting agent can be added at the point of mixing instead of vicinal to the nozzle, but this is relatively rare). The mixture is applied on to the requisite surface in the vicinity of the nozzle, by pneumatically projecting it out from the nozzle under pressure, e.g. by means of compressed air. With the dry mix system it is difficult to control the quantity of water added and therefore to control the water to cement ratio (hereinafter referred to as the W/C ratio). The method has the additional drawback that dust is generated.
b) The wet mix system is a system in which the cement and aggregate are mixed in the presence of water and the mixture pumped through a delivery hose to a nozzle and then pneumatically projected out of the nozzle, a quick-setting agent being added within the nozzle assembly or upstream of the nozzle, just prior to passage into the nozzle. There are also examples of this system where the cement composition can be pumped, rather than pneumatically conveyed, to a point midway between the point of mixing and the nozzle in the delivery hose followed by pneumatic conveying between this midpoint and nozzle. The system allows good control of W/C ratio and generates little dust.
Pressures employed in the pneumatic delivery of cement compositions in shotcreting generally range from 60 to 140 psi (413-965 KPa), and are more usually 80 to 120 psi (551-827KPa).
A particularly useful method of employing the malic or citramalic acid-based quick-setting agents of the present invention in shotcreting is to add less than an accelerating amount of a water-soluble salt of malic or citramalic acid initially upon batching of the cementitious composition and then to add an additional accelerating amount of the water-soluble salt of malic acid or citramalic acid in the vicinity of the nozzle, such as is described in United States Patent No. 5,634,972. If desired, a rheology modifying 5 material capable of imparting thixotropic properties to the cementitious composition may be added as described in the aforementioned US Patent No. 5,634,972.
The following examples merely demonstrate the invention and are not intended to limit the same. In the examples, setting time and compressive strength measurements conform to American Society for Testing and Materials Methods C 266 and C 109, respectively. All measurements were made at room temperature. In the examples, set times are determined from the time the citrate, malate or citramalate is mixed with the cement.
EXAMPLE I
The mix procedure simulates the time scale of wet-mix shotcreting, such that the mortar is premixed and the shotcrete accelerator, added at the nozzle, is mixed with the mortar only for a brief moment.
In a plastic bag, 3000 g of mortar mix (dry ingredients), which consists of 590 g of ordinaiy portland cement, 30 g of silica fume, and 2380 g of silica sand, is blended.
Approximately 75% of tL total of 206.5 g of mixing water is placed in the mixing bowl of a HobattTM lab mixer. The blended dry ingredients are then added. The mixer is started on low speed and the mortar is mixed for two minutes. During this time, the 35.4 g of potassium citrate (6% by weight of cement) is dissolved in the remaining mix water. This is added into the mixing bowl at the conclusion of the two minute initial mix cycle, and the mortar is mixed for an additional minute. The test specimens are then cast immediately.
Setting time and compressive strength measurements conform to American Society for Testing and Materials Methods C 266 and C 109, respectively, with the following results.
Setting Time @ 16 C+/-0.5 C(61 F+/-1 F) Final: 7 minutes Compressive Strength @ 16 C(61 F) MPa (PSI) 1 hour 5(730) 4 hour 12 (1709) 1 day 17 (2404) 7 day 25 (3647) 28 day 38 (5433) Example 1 is repeated except that the experiment is conducted at a temperature of 51.3 F and the amount of potassium citrate is increased to 8% by weight of the cement.
Setting time and strength properties by ASTM C266 and C 109, respectively, are as follows.
Setting Time @0.5oC+/-0.5 C(51 F+/-1 F) Final: 5 minutes Compressive Strength @ 16 C(61 F) MPa (PSI) 1 hour 5 (707) 4 hour 7 (1060) 1 day 19 (2742) 7 day 30 (4256) 28 day 41 (5856) In cement paste experiments (100 g. portland cement and 35 g. of deionized water), 5% of potassium citrate and 5% of lithium citrate (based on the weight of the cement) are individually evaluated with following set times recorded by a VicatTM needle apparatus.
Citrate Initial Set Final Set potassium citrate 240 seconds 320 seconds lithium citrate 200 seconds 280 seconds Following the general procedure of Example 1, a shotcrete mortar mix is prepared to contain 122 g. of Ashgrove Type I portland cement, 220 g. of silica sand, 40 g. of water and 7 g. of potassium citrate. The sand and cement are mixed together and then mixed with a solution of the citrate in the water. The resulting composition has an initial set of 30 seconds (ASTM C266) and a 1 hour compressive strength of 1800 psi (ASTM C109).
In a plastic bag, 2775 g of mortar mix (dry ingredients), which consists of 740 g of ordinary portland cement and 2035 g of silica sand, is blended together.
Approximately 50%
of a total of 333 g of mixing water is placed in the mixing bowl of a Hobart lab mixer.
The blended dry ingredients are then added. 44.4 g of dipotassium malate (6%
by weight of cement) is dissolved in the remaining mix water and added into the mixing bowl. The mortar is then mixed for three minutes. The test specimens are then cast immediately and determined to have the following properties:
Initial setting time: 7 minutes Final setting time: 9 minutes Compressive Strength PSI (MPa):
1 hour 673 (4.64) 4 hour 1525 (10.52) 1 day 2739 (18.89) 7 day 4411 (30.42) A mortar mix prepared in accordance with ASTM C109 is prepared to contain 8.5%
dipotassium malate based on the weight of the cement at a water to cement ratio of 0.45 and is determined to have the following properties:
Initial setting time: 4 minutes Final setting time: 6.5 minutes Compressive Strength PSI (MPa):
1 hour 863 ( 5.95) 4 hour 1840 (12.69) 1 day 3040 (20.97) 7 day 4081 (28.14) A mortar mix is prepared in accordance with ASTM C109 and contains 8% sodium citramalate based on the weight of cement at a water to cement ratio of 0.40 and is determined to have the following set times:
Initial set: 3 minutes Final set: 5 minutes
Claims (10)
1. A quick-setting cement composition comprising hydraulic cement and at least 5.5% by weight of the weight of the hydraulic cement of at least one of a water-soluble malate or citramalate.
2. A composition according to claim 1, wherein the composition additionally contains water for the hydraulic setting of the cement.
3. A composition according to claim 1, wherein the water-soluble malate or citramalate is an alkali metal malate or alkali metal citramalate.
4. A composition according to claim 3, wherein the alkali metal malate or alkali metal citramalate is selected from dipotassium malate and dipotassium citramalate.
5. A composition according to claim 1, wherein the malate or citramalate is present in an amount of from 5.5% to 8.5% by weight based on the weight of the hydraulic cement.
6. A method of rapidly forming in place a cementitious structure, comprising mixing a cementitious composition comprising hydraulic cement with at least 4% by weight of the weight of the hydraulic cement of at least one water-soluble citrate, malate or citramalate in the presence of sufficient water for hydraulic setting of the cement, delivering the resulting composition while fluid to the place of cementitious structure and forming the cementitious structure.
7. A method according to claim 6, wherein the cement composition is pneumatically delivered through a nozzle to the place of cementitious structure.
8. A method according to claim 6, wherein the citrate, malate or citramalate in the form of an aqueous citrate, malate or citramalate solution is mixed with the cement composition just prior to discharge from the nozzle.
9. A method according to claim 6, wherein the citrate, malate or citramalate is present in an amount of from 5.5% to 8.5% by weight based on the weight of the hydraulic cement.
10. Use of at least one water-soluble citrate, malate or citramalate in the rapid formation in place of a cementitious structure, comprising mixing a cementitious composition comprising hydraulic cement and delivering the resulting composition while fluid to the place of cementitious structure, wherein there is added to the mix at least 4% by weight of the weight of the hydraulic cement of the water-soluble citrate, malate or citramalate in the presence of sufficient water for hydraulic setting of the cement and such that the delivered composition achieves an initial set within 20 minutes of the time the cement is mixed with both the water and citrate, malate or citramalate.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US30937394A | 1994-09-20 | 1994-09-20 | |
| US30937194A | 1994-09-20 | 1994-09-20 | |
| US309,373 | 1994-09-20 | ||
| US309,371 | 1994-09-20 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2158501A1 CA2158501A1 (en) | 1996-03-21 |
| CA2158501C true CA2158501C (en) | 2008-11-04 |
Family
ID=26976773
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002158501A Expired - Fee Related CA2158501C (en) | 1994-09-20 | 1995-09-18 | Rapid-setting cementitious composition |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA2158501C (en) |
| CH (1) | CH689729A5 (en) |
| DE (1) | DE19534929B4 (en) |
| GB (1) | GB2293378B (en) |
| IT (1) | IT1276185B1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO962925L (en) * | 1996-03-29 | 1997-09-30 | Olav Geir Tjugum | Spray Concrete Accelerator, and Methods and Equipment for Addition to Spray Concrete |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE759703A (en) * | 1969-12-02 | 1971-05-17 | Progil | NEW ADDITIVES FOR CEMENT, MORTARS AND CONCRETE |
| DE2102172C3 (en) * | 1971-01-18 | 1980-03-20 | Dr. Karl Thomae Gmbh, 7950 Biberach | New means of treating and caring for the skin |
| US3856541A (en) * | 1971-04-28 | 1974-12-24 | Dow Chemical Co | Hydraulic cement and method of cementing in environments having elevated temperatures |
| GB2033367A (en) * | 1978-11-07 | 1980-05-21 | Coal Industry Patents Ltd | Quick Setting Cements |
| JPS5951504B2 (en) * | 1979-02-05 | 1984-12-14 | 積水化学工業株式会社 | Heat-curing cement composition |
| JPH0283244A (en) * | 1988-09-19 | 1990-03-23 | Showa Denko Kk | Dry spraying method |
| CH678526A5 (en) * | 1990-01-27 | 1991-09-30 | Sandoz Ag | |
| US5273579A (en) * | 1990-06-19 | 1993-12-28 | Mitsubishi Mining And Cement Co., Ltd. | Quick setting compositions |
| US5262166A (en) * | 1991-04-17 | 1993-11-16 | Lty Medical Inc | Resorbable bioactive phosphate containing cements |
| CH684476A5 (en) * | 1991-11-27 | 1994-09-30 | Sandoz Ag | Cement mixtures. |
| US5281265A (en) * | 1992-02-03 | 1994-01-25 | Liu Sung Tsuen | Resorbable surgical cements |
| AU4598393A (en) * | 1993-06-02 | 1994-12-20 | Sandoz Ltd. | Cement compositions and admixtures therefor |
-
1995
- 1995-09-18 CH CH02633/95A patent/CH689729A5/en not_active IP Right Cessation
- 1995-09-18 CA CA002158501A patent/CA2158501C/en not_active Expired - Fee Related
- 1995-09-18 GB GB9519072A patent/GB2293378B/en not_active Expired - Fee Related
- 1995-09-18 IT IT95RM000621A patent/IT1276185B1/en active IP Right Grant
- 1995-09-20 DE DE19534929A patent/DE19534929B4/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB2293378B (en) | 1998-01-21 |
| IT1276185B1 (en) | 1997-10-27 |
| ITRM950621A1 (en) | 1997-03-18 |
| CH689729A5 (en) | 1999-09-30 |
| ITRM950621A0 (en) | 1995-09-18 |
| GB2293378A (en) | 1996-03-27 |
| DE19534929A1 (en) | 1996-03-21 |
| GB9519072D0 (en) | 1995-11-15 |
| CA2158501A1 (en) | 1996-03-21 |
| DE19534929B4 (en) | 2005-06-16 |
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