JP2006182568A - Hardening accelerator and quick-hardening cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hardening accelerator with which a desired relatively long pot life can be secured even after adding water, setting proceeds rapidly after the lapse of the pot life, the setting period from starting of setting to completing of setting is made equal to or shorter than that by a conventional hardening accelerator, and the early strength developing property after hardening can be also enhanced, when it is admixed into a hydraulic composition such as cement, mortar, and concrete and which can be stored for a long period of time. <P>SOLUTION: The hardening accelerator contains calcium aluminate particles each having a hydrate coating layer, unslaked lime and/or slaked lime. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rapid hardening material for accelerating the hardening of a hydraulic substance such as cement or a mortar or concrete containing the hydraulic substance.

In emergency construction of concrete and mortar-based buildings, in order to harden in a short time, a mixture of a quick-hardening admixture with ordinary cement is often used, and a quick-hardening cement is often used. · 7Al ₂ O _3, calcium aluminate such as _{11CaO · 7Al 2 O 3 · CaF} 2, 4CaO · 3Al 2 O 3 · SO 3, 3CaO · Al 2 O 3 has been widely used. Calcium aluminates produce ettringite by a hydration reaction in the presence of calcium sulfate contained in gypsum and cement. This ettringite has the effect of promoting hardening and enhancing the expression of strength for a short time. On the other hand, calcium aluminates have high reaction activity that requires consideration for storage, and when calcium aluminates are used as they are in cement, mortar, concrete, etc., the setting start time from the time of water injection is considerably accelerated. After water injection, construction work had to be completed in a short time, which was a work restriction. For this reason, coagulation retarders such as organic acids such as gluconic acid, gluconate, citric acid and citrate and inorganic compounds such as silicofluoride, boric acid, borate and phosphate have been used in combination. The retarder can prevent at least instantaneous condensation after water injection, and can secure a desired construction work time. (For example, refer to Patent Document 1) However, since the use of a retarder has a strong retarding effect on the setting property of the cement itself, it is difficult to shorten the setting time of the setting, and the short-term strength is also reduced. There was a tendency, and there was a problem when it was necessary to complete the construction in a short period of time. If the reaction activity of calcium aluminates can be selectively suppressed, the pot life (time from the time of water injection to the start of condensation in the hydraulic composition) can be secured and the reduction in the setting speed can be suppressed. There is a possibility that condensation can be completed in a short time. As calcium aluminate in which the reaction activity is suppressed, those obtained by modifying the surface of calcium aluminate grains with water or fatty acid in advance are known. (For example, see Patent Documents 2 and 3.)
JP-A 61-155239 Japanese Patent Laid-Open No. 2-97443 JP-A-53-125431

  Calcium aluminates whose surfaces have been modified with water, fatty acids, etc., are used as a reaction layer of a modifying substance such as water or fatty acids and calcium aluminate is formed on the surface layer of calcium aluminate grains. The quick-hardening cement, mortar, and concrete obtained in this way can secure the desired pot life depending on the degree of modification and prevent the setting time from being delayed. End up. The tendency to decrease the rapid hardness becomes more prominent as the pot life is secured longer. The present invention solves such a problem, and it is possible to sufficiently secure the pot life required for work, and after the pot life has passed, the condensation rapidly progresses, and the time from the start to the completion of the condensation is reached. It is an object of the present invention to provide a hardened material that is not inferior to conventional hardened materials, has high early strength development after curing, and can be stored for a long time.

  As a result of repeated studies for solving the above problems, the present inventors have moderately suppressed mainly the initial reaction activity of calcium aluminate by using calcium aluminate grains on which a specific coating layer is formed. In addition to securing the pot life, the use of quick lime or slaked lime in combination with calcium aluminate to accelerate the setting speed after the start of setting has a short effect after the pot life has passed, with little effect on the reserved pot life. Thus, the present invention was completed because the setting was completed and high strength was exhibited.

  That is, the present invention is the following (1) to (4) rapid hardening material and (5) rapid hardening cement composition. (1) A hardened material containing calcium aluminate particles having a hydrate coating layer and quicklime and / or slaked lime. (2) A hardened material comprising 100 parts by weight of calcium aluminate particles having a hydrate coating layer and 3 to 10 parts by weight of quicklime and / or slaked lime. (3) The rapid hardening material according to (1) or (2), further comprising at least one of aluminum sulfate, alkali metal sulfate, and alkali metal carbonate and calcium sulfate. (4) The rapid hardening material according to any one of (1) to (3), further comprising calcium sulfate. (5) A quick-hardening cement composition comprising the quick-hardening material and cement according to any one of (1) to (4).

  By using the hardened material of the present invention, cement, mortar, concrete, etc. with a short setting time and high early strength that can be used for emergency work can be easily obtained, and it is indispensable for construction work. It is possible to give time for a relatively long time. Moreover, since the quick-hardened material of the present invention is remarkably excellent in durability against weathering, it can flexibly cope with various usage situations.

The rapid hardwood of the present invention uses calcium aluminate particles having a hydrate coating layer. Here, calcium aluminate is a general term for a compound containing CaO and Al ₂ O ₃ as main chemical components, a solid solution, glassy material, or a mixture of any of these, and is not limited as long as it has hydration activity. Specifically, for _{example, 12CaO · 7Al 2 O 3,} 11CaO · 7Al 2 O 3 · CaF 2, 4CaO · 3Al 2 O 3 · SO 3 , etc. can be mentioned, or alumina cement. The particle diameter of the calcium aluminate particles to be used is not particularly limited, but is preferably 0.3 to 200 μm. More preferably, those having a particle size distribution such that the 150 μm sieve residue is 2% by weight or less are suitable. If the particle size exceeds 200 μm, the reaction activity may be too low to provide sufficient rapidity, and if the particle size is less than 0.3 μm, it is difficult to form a desired hydrate coating layer by a general-purpose method. Hydrate coating layer coating the particulate calcium aluminate is not particularly limited, for _{example, CaO · Al 2 O 3 ·} 10H 2 O, 2CaO · Al 2 O 3 · 8H 2 O, 3CaO · Al 2 O 3 · 6H _{2 O, 3CaO · Al 2 O} 3 · 8H 2 O, 4CaO · Al 2 O 3 · 13H 2 O, 4CaO · Al 2 O 3 · 19H 2 O, Al 2 O 3 · 3H 2 CaO of O, etc. and Al ₂ O ₃ and H ₂ O, or those made of Al ₂ O ₃ and H ₂ O and the like. The hydrate coating amount is preferably 0.3 to 5% by weight, and more preferably 0.5 to 4% by weight of the calcium aluminate grains including the hydrate coating layer. If the hydrate coating amount is less than 0.3% by weight, the initial reaction activity suppressing action of calcium aluminate is weakened and the pot life may not be secured. If it exceeds 5% by weight, the coating layer thickness becomes too thick. Therefore, a significant delay in the hydration reaction of calcium aluminate and early strength development may be reduced. Covering the entire surface of the calcium aluminate grains as much as possible, the hydrate coating layer can effectively suppress the initial reaction activity of the calcium aluminate, and can effectively suppress the weathering of the calcium aluminate. This is desirable because the performance hardly deteriorates even if stored for a long time without taking a preservative treatment.

  The method for forming the hydrate coating layer on the calcium aluminate grains is not limited. To give a relatively simple example, calcium aluminate powder is charged into a blender and corresponds to a weight of approximately 0.2 to 3.5% of the weight of calcium aluminate charged at a temperature of about 5 to 25 ° C. What is necessary is just to mix, spraying water to spray with a sprayer. The coating layer formed on the calcium aluminate particles is preferably composed only of a hydrate, but even in a coating layer in which other components coexist in addition to the hydrate, the effect of the present invention is not substantially impaired. If it does not matter. As an example of this, there may be mentioned a case in which the calcium aluminate is sprayed using water in which a shrinkage reducing agent and a dispersing agent that can be used for mortar and concrete are previously dissolved.

  The quick-hardened material of the present invention essentially uses one or both of quick lime and slaked lime. Preferably slaked lime is used. By using quicklime and slaked lime, the calcium ion concentration in the liquid can be quickly saturated at the start of the hydration reaction after water injection. There is an action to supplement the reaction, and when calcium aluminate begins to hydrate, hydration proceeds rapidly, and the setting time can be shortened. Quicklime and slaked lime are used in an amount of 3 to 10 parts by weight based on 100 parts by weight of calcium aluminate having a hydrate coating layer. If it is less than 3 parts by weight, it is difficult to shorten the setting time, and if it exceeds 10 parts by weight, it may be difficult to ensure the pot life. When using quicklime and slaked lime in combination, the use ratio between the two is not limited, but it is preferable to use more slaked lime than quicklime.

  Furthermore, the rapid hardening material of the present invention is any one of aluminum sulfate, alkali metal sulfate, and alkali gold crude carbonate in addition to calcium aluminate particles having a hydrate coating layer and quick lime and / or slaked lime. It is preferable to blend seeds or two or more. Aluminum sulfate, alkali metal sulfate, and alkali metal carbonate have a hardening promoting effect on cement and enhance early strength development. In either case, the alkali metal species and alkaline earth metal species are not limited. The amount of aluminum sulfate, alkali metal sulfate, and alkali gold crude carbonate used is preferably 0.1 to 12 parts by weight per 100 parts by weight of calcium aluminate particles having a hydrate coating layer. If it is less than 0.1 part by weight, the blending effect cannot be obtained, and if it exceeds 12 parts by weight, the long-term strength development property may be lowered.

In addition, the quick-hardened material of the present invention is allowed to contain components other than those described above unless the effects of the present invention are substantially lost. If an example of such a component is given, it will be easy to adjust the hydration reaction, and it is recommended to contain calcium sulfate because it can enhance the medium- to long-term strength development. Any calcium sulfate can be used, but it is particularly preferable to use 10 to 50 parts by weight of anhydrous gypsum having a Blaine specific surface area of 7000 cm ² / g or more per 100 parts by weight of calcium aluminate particles having a hydrate coating layer. This is preferable because it provides a function for adjusting the hydration reaction.

  The method for producing a rapid hardwood of the present invention includes, for example, a predetermined amount of calcium aluminate particles, quick lime and slaked lime in which a hydrate coating layer has been previously formed, and further, if necessary. However, it is not limited to the method shown here, although it can obtain easily if it mix | blends an appropriate quantity of these ingredients, and dry-mixes, for example with mixers, such as a Henschel mixer, a ribbon mixer, and a spray mixer.

  The rapid-hardening cement composition of the present invention comprises the rapid-hardening material and cement according to the present invention. The blending ratio is preferably 20 to 200 parts by weight, more preferably 30 to 100 parts by weight, based on 100 parts by weight of cement. If it is less than 20 parts by weight of the rapid-hardening material, it is difficult to impart rapid hardening, and early strength development becomes low. As long as the cement used is a hydraulic cement, any cement may be used as long as it is not an alumina cement. Examples of cements that are relatively suitable for use include ordinary portland cement, early-strength portland cement, ultra-high-strength portland cement, various portland cements such as moderately heated portland cement, blast furnace cement, fly ash cement, silica aluminate and other calcium aluminates. Examples include various mixed cements that are not mainly composed of components, and special cements such as white cement and eco-cement. Further, instead of such cement, for example, a powder containing cement clinker pulverized material and gypsum may be used.

  The rapid-hardening cement composition comprising the rapid-hardening material and cement can be generally handled as cement at least in use. In addition, the quick-hardening cement composition of the present invention may contain other components in addition to the quick-hardening material and cement as long as the effects of the present invention are not lost. For example, aggregates, fibers, pigments, Inorganic fine powder such as limestone and silica, pozzolanic reactive fine powder, shrinkage reducing agent, expansion material, rust preventive agent, antifoaming agent, air entraining agent, thickener, dispersant and water reducing agent (including high performance water reducing agent), Examples include those containing admixtures / materials such as white flower inhibitor and thickener and water. In this case, the rapid-hardening cement composition can be handled in substantially the same manner as, for example, mortar and concrete. In addition, when it is desired to ensure a particularly long pot life of the present rapid-hardening cement composition, it becomes possible to contain a setting retarder, and in this case, an appropriate amount, for example, about 0.1 to 0.5 with respect to 100 parts by weight of cement. If the weight part is used, the deterioration of the early strength development and the noticeable delay of the setting time do not occur, and a pot life of, for example, about 0.5 to 3.5 hours can be secured sufficiently.

  The manufacturing method of the rapid-hardening cement composition of this invention is not specifically limited. For example, a quick-hardening cement composition composed of the above-mentioned quick-hardening material and cement, or one or two or more of inorganic fine powder, pozzolanic reactant fine powder and setting retarder added to the quick-hardening material and cement. In the case of the quick-hardening cement composition, it is preferable to add a predetermined amount of each material to a kneader such as a Henschel mixer and dry-mix, and in the quick-hardening cement composition containing other components, all the materials other than water are used. It is preferable that the materials are put all at once into a mixing / kneading machine such as a twin-screw mixer, mixed and stirred as appropriate, and then poured for kneading for about 1 to 5 minutes. The amount of water to be blended is recommended to be 30 to 65 parts by weight of water with respect to 100 parts by weight of cement and the present hard material.

Hereinafter, the present invention will be described in detail by way of examples.
As calcium aluminate particles, a mixture of CaO and Al ₂ O ₃ in a molar ratio of 12: 7 was baked at about 1600 ° C. in the air, and then naturally cooled in a baking apparatus, and then pulverized. Crystalline 12CaO · 7Al ₂ O ₃ particles adjusted to about 4000 g / cm ² or alumina cement (Brain specific surface area of 5100 cm ² / g, manufactured by Taiheiyo Materials Co., Ltd.) was used. Put 50000 g of the calcium aluminate particles in a Laedige mixer, and while rotating the mixer, add 250 g of water by spraying over about 2 minutes with a sprayer and spin-mix for another 10 minutes. The mixture was left for 3 hours to form a hydrate coating layer on the surface of the calcium aluminate particles.

12CaO · 7Al ₂ O ₃ particles (A1) having a hydrate coating layer, alumina cement particles (A2) having a hydrate coating layer, and alumina cement particles (A3) having no coating layer formed. Three types of calcium aluminate are used, and any one of these materials is selected from lithium carbonate, slaked lime, quicklime, type II anhydrous gypsum, aluminum sulfate, and potassium sulfate (all are commercially available reagents). A rapid hardwood (invention products H1 to H7, reference products H10 and H20) was prepared by batch charging into a Roedige mixer and mixing for about 3 minutes. The obtained quick-hardened material was packed and sealed so that there was as little gap as possible in the plastic bag. Some rapid-hardening materials (part of the product H2 of the present invention) were left for 28 weeks in a constant temperature and humidity chamber maintained at a temperature of 20 ° C. and a humidity of 70% without being filled with vinyl.

  The Hobart mixer so that the blended amount shown in Table 3 is applied to the hardwood, ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) and fine aggregate (specific gravity 2.69, land sand produced in Ogasa, Shizuoka Prefecture) Mixed. Next, a solution obtained by dissolving the amounts of citric acid and sodium heptonate described in Table 2 in the amount of water described in Table 2 is added to the mixture in the Hobart mixer, and the mixture is further kneaded for about 1 minute. S1-S9 and reference products S10-S12) were obtained. For the preparation of a part of the composition (the product S9 of the present invention), a hard material left for 28 weeks in the above-mentioned constant temperature and humidity chamber was used.

  The obtained slurry-like composition was subjected to a setting test according to a method according to “JIS C 5201“ Physical testing method for cement ”, and the initial setting time and the final setting time from the time of water injection were measured. Further, the slurry-like composition was filled into a predetermined mold within 5 to 10 minutes after the completion of kneading to prepare a 40 × 40 × 160 mm curing test body. The compressive strength was measured for each specimen at a material age of 2 hours, 3 hours, and 1 week. The compressive strength was measured by a method based on “Physical testing method for cement” of JIS R 5201. The above results are shown in Table 3.

  From Table 3, the composition using the quick-hardening material of the present invention can secure a relatively long pot life of 30 minutes or more, and after the pot life has elapsed, the setting rapidly progresses and the setting takes place in a very short time. Completed and can have high early strength development. In addition, it can be seen that even if the properties are stored for a long time under high humidity, they are hardly lost and have excellent weathering durability.

Claims (5)

A hardened material comprising calcium aluminate particles having a hydrate coating layer and quick lime and / or slaked lime. A rapid hardwood comprising 100 parts by weight of calcium aluminate particles having a hydrate coating layer and 3 to 10 parts by weight of quicklime and / or slaked lime. The rapid hardening material according to claim 1 or 2, further comprising at least one of aluminum sulfate, alkali metal sulfate, and alkali metal carbonate. Furthermore, the rapid-hardening material in any one of Claims 1-3 formed by containing calcium sulfate. A rapid-hardening cement composition comprising the rapid-hardening material according to any one of claims 1 to 4 and cement.