EFFLORESCENCE-INHIBITING AGENT

Abstract: A liquid-state efflorescence-inhibiting agent which causes low air-entrainment to a cement composition such as concrete, which has storage stability at low temperatures, and which is excellent in the appearance of strength. The efflorescence-inhibiting agent comprises one or more species of C8-C18 fatty acid alkaline metal salts, wherein the content of the C12-C16 fatty acid alkaline metal salts is not less than 80 % by weight.

Description: EFFLORESCENCE-LNHL ITING AGENT The invention relates to a liquid-state efflorescence-inhibiting agent and to a cement composition using this agent. Good external appearance is especially important for a concrete product in which the concrete surface receives no other coating. However, the appearance is frequently spoiled by the permeation to and efflorescence of water-soluble salts from the surface. Various methods to prevent the appearance of efflorescence of concrete have been proposed. Examples of commercially-available efflorescence-inhibiting agents include powder products which are based on higher fatty acid salts of alkaline earth metals such as calcium and magnesium, and aluminum, and liquid products which are based on alkaline salts of unsaturated acids such as oleic acid. For example, in JP, B, H6-74160, a powder product is used in a method to prevent efflorescence. The product is a blend of a water-soluble amino resin and a higher fatty acid metal salt and/or a non-ionic surface active agent. A typical example of a higher fatty acid metal salt is an alkaline earth metal salt of a higher saturated C 9 -C 21 monocarboxylic acid, preferred examples including calcium stearate, magnesium stearate, calcium myristate, calcium pa nitate, calcium laurate and the like. However, because the alkaline earth metal salts of C 9 -C 21 fatty acids are sparingly soluble in water, it is not possible to provide a liquid efflorescence-inhibiting agent, and therefore they are not easy to handle and use. There is also an efflorescence-inhibiting agent based on an alkaline metal salt of an unsaturated fatty acid such as oleic acid (Cj 8 ) or linoleic acid (C] 8 ) or a saturated fatty acid such as palmitic acid (Cι 6 ) or stearic acid (C] 8 ), though this becomes cloudy or solid at ordinary temperatures or lower. It is inferior in storage stability and difficult to supply and use as a liquid product, especially in winter. A further difficulty encountered with conventional efflorescence-inhibiting agents is that they often have air-entraining properties. For example, JP, A, S61-219747 proposes a method of preventing efflorescence using calcium chloride, sodium lauryl sulfate and sodium oleate, but this method involves the problem that sodium lauryl sulfate and sodium 0NR oleate are air-entraining agents, which entrain air into concrete excessively. In addition, calcium chloride corrodes reinforcing steel in concrete. JP, A, H5-319882 proposes an efflorescence-inhibiting agent containing tall oil fatty acids and unsaturated C 8 -C 8 fatty acids, alkanolamine and/or aDcylarnine, but this again is not optimal because the unsaturated fatty acids entrain air into concrete excessively. An anti-foaming agent may be added to counteract this tendency, but the amount of the anti-foaming agent necessary to adjust the desired air content may be large, with the adjustment being difficult and it is difficult to prepare concrete with suitable freeze-thaw durability. Further, since fatty acid salts are generally water-repellent, conventional efflorescence-inhibiting agents have the problem that this property deteriorates the strength development of a cement composition such as concrete. Thus, there is a need in the art for an efflorescence-inhibiting agent which is in a liquid state, causes low air-entrainment, and allows a desired air content to be easily attained by using a small amount of an air- entraining agent, and furthermore does not reduce strength development. Good storage stability at low temperatures is also desirable. The invention therefore provides an efflorescence-inhibiting agent which comprises selected saturated fatty acid alkali metal salts at selected ratios, which is in a liquid state, causes little air-entrainment and has good storage stability at low temperature. Furthermore, by adding alkanolamine and/or alkylenediamine together, an efflorescence- inhibiting agent with excellent strength development is given. More particularly, the invention relates to a liquid-state efflorescence-inhibiting agent comprising one or more species of C 8 -C] 8 fatty acid alkali metal salts wherein the content of the Ci 2 -C 16 fatty acid alkali metal salts is not less than 80% by weight, and to a cement composition containing said inhibiting agent. Further, the invention also relates to an efflorescence-inhibiting agent additionally containing alkanolamine and/or alkylenediamine, and to a cement composition containing said inhibiting agent. The content of Cj 8 fatty acid alkali metal salt in all fatty acid alkali metal salts of the invention is preferably less than 5% by weight to prevent cloudiness of a solution or the appearance of a solid precipitate at ordinary temperatures or below. Additionally, in view of the possibility of air-entrainment into a cement product, the content of saturated fatty acid alkali metal salt of not more than 10 carbon atoms in all fatty acid alkali metal salts of the invention is less than 10% by weight, preferably less than 5% by weight, and the content of unsaturated C 18 fatty acid alkali metal salt is less than 15% by weight, preferably less than 10% by weight. Further, in view of the desirability of storage stability at low temperature, a more preferable embodiment of the invention is that the blend proportion of Cι 2 -C 16 saturated fatty acid alkali metal salts is 40-100% by weight of a d 2 saturated fatty acid alkali metal salt, less than 60% by weight of a C 14 saturated fatty acid alkali metal salt, preferably less than 50%) by weight, and less than 20% by weight of a Cι 6 saturated fatty acid alkali metal salt, preferably less than 15% by weight. The alkali metals of the fatty acid salts in the present invention are sodium or potassium, the potassium salt being preferable in view of the need for storage stability of a solution. An efflorescence-inhibiting agent according to the invention can also contain alkanolamine and/or alkylenediamine. Examples of alkanolamines include ethanolamine, diethanolamine and triethanolamine, and those of alkylenediamine include ethylenediamine and propylenediamine. By using a blend of alkanolamine and/or alkylenediamine, the strength deterioration of the cement product can be improved. Alkanolamine and/or alkylenediamine can be blended into an efflorescence-inhibiting agent in an amount of from 0.005-0.05%) by weight, preferably 0.01-0.03%) by weight solids, based on cement weight in a cement composition. Further, the invention provides a cement composition wherein an efflorescence- inhibiting agent of the invention and a water-reducing agent are used together. The water- reducing agent has the effect of reducing the water content needed in a cement composition, and by use of the water-reducing agent together with an efflorescence- inhibiting agent of the invention, the efflorescence appearance of a cement product can effectively be prevented. Examples of water-reducing agents which can be used include lignosulfonic acid salts, oxycarboxylic acid salts, polyalkylsulfonic acid salts, polycarboxylic acid salts, condensate salts of naphthalene sulfonic acid and formalin, condensate salts of melaminesulfonic acid and formalin, arnino sulfonic acid or polysaccharide derivatives. The amount of water-reducing agent used is from 0.01-3.0%o by weight, preferably 0.05-1.0% by weight solids, based on cement weight in a cement composition. A cement composition according to the present invention is a composition containing at least cement, for example, cement paste, ultra dry-mix concrete, concrete having slump, and the like. The amount of efflorescence-inhibiting agent according to the present invention needed for any composition can be readily determined, but generally it lies in the region of from 0.05-2.0%> by weight solids, based on cement weight in a cement composition. Further, an efflorescence-inhibiting agent of the present invention can be used together with other additives such as drying shrinkage agents, accelerators, retarders, foaming agents, anti-foaming agents, anti-rust agents, set acceleration agents, thickeners, water-soluble polymers, etc. The invention is further illustrated by means of the following non- limiting examples. Examples 1. Materials used The materials used for the test are shown in Table 1. Table 1 2. Mortar and concrete tests 5 2.1 Mortar test (I) abbreviated as saturated fatty acid salts) and the unsaturated fatty acid alkali metal salts (hereinafter abbreviated to unsaturated fatty acid salts) into mortar is tested. 1) Mortar blend The mortar blend used for the test is shown in Table 2. The blend A is mortar wherein no water-reducing agent was used, and the blend B is mortar wherein the water- reducing agent (LSN) was used at 250 ml per 100 kg of cement. Additionally, the amount used for the fatty acid salts is constantly made 0.15% by weight solids, based on cement weight. Further, the amount used for the air-entraining agent (Cl) is shown by the number of A, and the amount corresponding to 0.002%> by weight based on cement weight is shown as 1A. Table 2 2) Test methods The amount used for the air- entraining agent (AE agent or anti-foaming agent) necessary for the adjustment to the desired air content 9±1% is tested. Additionally, the tests of mortar flow and air content are carried out by the methods below. (1) Mortar flow: According to JIS R 5201 (2) Air content: According to Mass method 3) Test results The test results are shown in Table 3 and Figures 1 and 2. According to Table 3 and Fig. 1, each saturated C 8 -Cι 8 fatty acid salt (A 8 -Aι 8 ) shows the tendency of air-entrainment to increase as the number of carbon atoms decreases. The C 18 unsaturated fatty acid salt (B 18 ) gives a larger air entrainment than does the saturated fatty acid salt with the same number of carbon atoms. This tendency is also the same in case of the blend A and the blend B, and the blend B used together with the water-reducing agent (LSN) exhibits larger air-entrainment than the blend A wherein the water-reducing agent is not used. Fig. 2 is that the correlation (correlation equation) between the number of carbon atoms of the saturated fatty acids and the amount of the air-entraining agent necessary for entrainment of 9% air into mortar is obtained by the test results of Table 1. In the column headed "Amount of AE agent required for 9%>", the values obtained by this correlation equation are shown. Table 3 Note: The mortar flow was in a range of 180-200 mm for Blend A and 200- 220 mm for Blend B. 2.2 Mortar test (IT) The effect that the content of the unsaturated fatty acids in the saturated fatty acids exerts on the air-entrainment of mortar is tested. 1) Blend of mortar The mortar used for the test is the blend B shown in 1) of 2.1. Further, the amounts of each fatty acid salt used are 0.3%> by weight solids, based on cement weight. 2) Test methods The air-entrainment into mortar is tested for a variety of mix proportions of each saturated fatty acid salt, A 8 , Aio or An, and the unsaturated fatty acid salt (Big) against the saturated fatty acid salts (Aι -ι 6 ). The tests of the mortar flow and the air content are carried out by the same methods as in 2) of 2.1. 3) Test results The test results are shown in Table 4. Table 4 shows the tendency that the air content of mortar becomes larger as the content of A 8 , Aι 0 and Bι 8 becomes larger. On the contrary, A i 2 shows almost no change in air-entrainment, even if the content of Aι 2 is increased. Table 4 2.3 Mortar test (III) The compressive strength of mortar is tested in the case of the use of the saturated fatty acid alkaline metal salts with alkanolamine. 1) Blend of mortar The mortar used for the test is the blend B shown in 1) of 2.1. The amounts of saturated fatty acid salts used are 0.3% by weight solids, based on cement weight. 2) Test methods The mortar flow and the air content are tested by the same methods as in 2) of 2.1 , and the compressive strength is tested according to JIS A 1108 by means of a test sample of 5 cm diam. x 10 cm prepared according to JSCE-F506-1995. 3) Test results The test results are shown in Table 5. According to Table 5, the compressive strength of mortar to which the saturated fatty acid salts are added is 90-92% of that of the comparative example. On the contrary, the compressive strength of mortar in the case where alkanolamine or alkylenediamine are added is 93-99%, with strength development being improved. Table 5 Note *1 : The amount used was wt% of a solid equivalent based on a cement weight. Note *2: The figures in Table show the strength ratio, where the compressive strength of the comparative example is let 100. 2.4 Concrete test (I) The efflorescence-inhibiting effect of the saturated fatty acids on ultra dry-mix concrete is tested. 1) Blend of concrete The blend of ultra dry-mix concrete used for the test is shown in Table 6. Table 6 2) Mixing of concrete In the mixing of concrete, each material is measured to make the mixing volume 40 litres, and all the materials are then placed into a 50 litre pan-type forced mixing mixer, followed by mixing for 90 seconds to prepare concrete. 3) Test methods (1) Evaluation of efflorescence-inhibiting effect A cylindrical sample of 10 cm diam. x 20 cm is prepared and cured at 50°C for 24 hours after mixing out, followed by cutting 2 cm wide specimens from the centre after removing the mould. In order to prevent penetration and evaporation of water from the side of the test sample, the side is coated with wax, followed by immersing half the test sample into water at 30°C to observe visually a degree of efflorescence appearance. The judgment of the degree of the efflorescence appearance is done according to the following criteria. A (good): No efflorescence appearance B (normal): Slight efflorescence appearance C (bad): Efflorescence appearance 4) Test results The test results are shown in Table 7. According to Table 7, A 8 was evaluated as ..normal", and in each saturated fatty acid salt of Aι 0 -Aι 6 , the saturated fatty acid salts of Aj 2 -Ai 6 or Aι 2 -A] 8 and the unsaturated fatty acid salt of Big, the efflorescence-inhibiting effect is observed, and the evaluation is "good" or in case of the small amount used is "normal". Table 7 The air-entrainment and the efflorescence-inhibiting effect of the saturated fatty acid salts on concrete having a standard slump used in a concrete product are tested. 1) Blend of concrete The blend of concrete of the desired slump 8±2.5 cm and the desired air content 4.5±0.5%> which are used in the test is shown in Table 8. The amounts of water- reducing agent and/or air content-regulating agent are adjusted so that the slump and the air content fall within the desired range. Additionally, in case of PCA, the water- reducing agent is used % by weight based on a cement weight, and in case of LSA or MSA it was used by litres or millilitres per 100 kg cement Table 8 2) Mixing of concrete The mixing of concrete is carried out in the same way as 2) of 2.4. 3) Test methods The evaluation tests of the slump, air content and efflorescence-inhibiting effect of concrete are carried out by the following methods: (1) Slump: According to JIS A 1101. (2) Air content: According to JIS A 1128. (3) Evaluation of efflorescence-inhibiting effect: It is carried out in the same way as 3) of 2.4. 4) Tests results The test results are shown in Table 9. According to Table 9, the air-entraining agent was used, because each saturated fatty acid salt of Aι 2 -Aι 6 , saturated fatty acid salts of A 12 -A 16 or Aι 2 -A] had no air-entrainment. On the contrary, because the air- entrainment in concrete was too much in case of the unsaturated fatty acid salt of Big, the anti-foaming agent is used. The efflorescence-inhibiting effect is observed in either of the saturated fatty acid salt or the unsaturated fatty acid salt, and is evaluated as "normal" or "good" depending on the amount used. Further, the results of the air- entrainment are different according to the type of water-reducing agent used. Table 9 3. Stability test of solution under low temperature The aqueous solution of the fatty acid salts is allowed to stand at 0°C, and the stability of the solution is checked by visual observation of the outside. The stability of the solution under low temperature conditions is done according to the following criteria:. O (good): The solution does not change in properties and remains in a clear liquid-state. X (bad): In the solution is observed crystallization, cloudiness, a precipitate at the bottom or solidification. The test results are shown in Table 10. According to Table 10, when the blend proportion of Aι 2 and Aj is changed to give a blend proportion of A )4 not less than 60% by weight, and also in case of the changing of a blend proportion of Aι 2 and Aι 6 to give the blend proportion of Aι 6 not less than 20%o by weight, crystallization, cloudiness or solidification are confirmed in the solution. Table 10 The efflorescence-inhibiting agent of the invention is in the liquid state, which is convenient for use. It may be used not only for ultra dry-mix concrete, but can also be used for concrete having the slump in which use of an efflorescence-inhibiting agent having a conventional unsaturated fatty acid salt as a main component is difficult. Further, since it is excellent in the storage stability of the solution even under a low temperature atmosphere and also in the appearance of strength, it can be used extremely in a general way. Brief Description of Drawings Fig. 1 is a graph showing the correlation between the carbon number of the saturated fatty acids and the air content. Fig. 2 is a graph showing the correlation between the number of carbon atoms of the saturated fatty acids and the amount of the air- entraining agent necessary for entrainment of an air content of 9% by volume into mortar.

Claims: Claims 1. A liquid-state efflorescence-inhibiting agent comprising one or more Cg-Cig fatty acid alkali metal salts, wherein the content of Cι 2 -Cι 6 fatty acid alkali metal salts is not less than 80%) by weight. 2. A liquid-state efflorescence-inhibiting agent according to claim 1, which contains 5%o by weight maximum of a Cι 8 saturated fatty acid alkali metal salt. 3. A liquid-state efflorescence-inhibiting agent according to claim 1 or claim 2, which contains 10%> by weight maximum of at least one saturated fatty acid alkali metal salt having 10 carbon atoms maximum. 4. A liquid-state efflorescence-inhibiting agent according to any one of claims 1-3, which contains 15% by weight maximum of a Cι 8 unsaturated fatty acid alkali metal salt. 5. The liquid-state efflorescence inhibiting agent according to any one of claims 1-4, which contains 40-100%) of a 2 saturated fatty acid alkali metal salt, less than 60%> of a Cι 4 saturated fatty acid alkali metal salt, and less than 20% of a Cι 6 saturated fatty acid alkali metal salt, all percentages being by weight of the total agent. 6. A liquid-state efflorescence-inhibiting agent according to any one of claims 1-5, which additionally contains alkanolamine and/or alkylenediamine. 7. A cement composition comprising the liquid-state efflorescence inhibiting agent according to any one of claims 1-6. 8. A cement composition according to claim 7, additionally comprising one or more species of water-reducing agents selected from a group consisting of lignosulfonates, oxycarboxylates, polyalkylsulfonates, polycarboxylates, formalin condensates of naphthalene sulfonates, formalin condensates of melamine sulfonates, aminosulfonates, and polysaccharide derivatives. 9. A method of preventing efflorescence on surfaces of hardened cementitious materials by the incorporation of an efflorescence-inhibiting agent according to any one of claims 1-6 into a liquid cementitious mix from which the surfaces will be formed.

Inventors: IWATA RAITA, TSUCHITANI TADASHI, IWATA, RAITA, TSUCHITANI, TADASHI
Applicants: IWATA RAITA, MBT HOLDING AG, TSUCHITANI TADASHI, IWATA, RAITA, TSUCHITANI, TADASHI
Application year: 1999
Main classification: C04B24
IPC codes: C04B24, C04B28, C04B111