JP2009215110A - Unslaked lime powder for expansive material, expansive material for concrete, water-hardening type binding material, concrete, and method of constructing concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an unslaked lime powder for an expansive material for an early stage form removal concrete capable of materializing sufficient expansion by hydration in a concrete structure even if a form is removed in an early stage of 2-3 days after placing concrete, and drastically reducing the generation of dry shrinkage and cracks. <P>SOLUTION: The unslaked lime powder for the expansive material is an unslaked lime powder having an ignition loss of not greater than 6 mass%, containing not less than 90 mass% of CaO, having a Brain specific surface area of 3,000-7,000 cm<SP>2</SP>/g, and a BET specific surface area of the unslaked lime powder having a particle size within the range of 90 μm-1 mm of not greater than 2.0 m<SP>2</SP>/g wherein a second heat evolving peak in a hydration heat evolving rate curve obtained by measuring a mixed powder using an isothermal conduction type calorimeter is appeared only on and after 2 hours after when contacting water, the mixed powder consisting of 75 mass% of a mixture of 75 mass% of the unslaked lime and 25 mass% of anhydrous gypsum, and 25 mass% of an ordinary portland cement. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to quick lime powder for an expansion material that can reduce the occurrence of shrinkage cracks in early-stage demolding concrete used for construction work such as a concrete structure, an expansion material including the quick lime powder, and a hydraulic property including the expansion material The present invention relates to a binding material, early demolding concrete, and a method for constructing a concrete structure using the concrete.

  In the construction of concrete structures, first, cement, aggregate, chemical admixture, etc., and concrete mixed with a predetermined amount of water measured and mixed in a pre-assembled formwork, after curing for a predetermined period of time By removing the mold (demolding), a process of obtaining a concrete structure made of hardened concrete is performed. In recent construction works for civil engineering and building structures, there is a strong demand for shortening the construction period as well as the workability of fresh concrete and the strength characteristics and durability of the hardened body. For this reason, it is desired to remove the mold release as soon as possible after securing a predetermined strength to the concrete structure. The demolding time varies depending on the placing conditions (temperature, design strength, etc.), but is required to be 2 to 3 days after placing concrete. In this way, concrete that can advance the time of demolding is called early demolding concrete.

  On the other hand, after demolding, the concrete structure usually shrinks as the drying proceeds from the surface thereof, and when the shrinkage stress exceeds the tensile strength of the concrete, cracking occurs. In order to reduce the cracks, it is necessary to add an amount of expansion sufficient to compensate for the amount of drying shrinkage of the concrete, or to reduce the amount of drying shrinkage by blending a predetermined concrete admixture with concrete. . As a concrete admixture for that purpose, expansion materials and shrinkage reducing agents are known.

Among these, the expansion material includes a material that expands with a hydration reaction, and compensates for drying shrinkage of the concrete structure by hydration expansion. Such an expansion material is put into practical use as various admixtures for concrete. As materials having hydration expansibility, calcium sulfoaluminate (3CaO · 3Al ₂ O ₃ · CaSO ₄ ), calcium aluminate (CaO · Al ₂ O ₃ ), anhydrous gypsum (CaSO ₄ ), calcium oxide (CaO) )It has been known. These materials are produced by preparing a single component or a plurality of component raw materials and pulverizing a clinker obtained by firing. The expansion rate and expansion amount of the expansion material are controlled by controlling the composition of the material generated in the clinker and the clinker structure, and by adding one or more materials such as anhydrous gypsum powder and quicklime powder. It is performed by mixing (for example, patent documents 1 to 3). In order to control the expansion speed and expansion amount of the expansion material, advanced manufacturing technology and quality control are required, and therefore, a commercially available expansion material is expensive.

  In order to compensate for the amount of drying shrinkage of concrete structures, it is necessary to achieve a predetermined expansion amount for a short period of time, for example, during the form retention period and concrete curing period, but this requires advanced technology. Is done. Conventionally, in order to obtain a predetermined expansion amount in a short period of time, it has been dealt with by simply increasing the blending amount of the above-mentioned various expansion materials. However, since such an expandable material hydrates in the medium to long term, the hydration expansion reaction often proceeds after the concrete is sufficiently hardened, thereby destroying the concrete structure that has been firmly formed. , There is a risk that the strength will decrease. In an extreme case, the unit amount of the expansion material becomes excessive, which may cause excessive expansion and cracking, and the structure may collapse. In order to avoid such an abnormal expansion phenomenon, it is required to complete the hydration reaction of the expanded material during the curing period by taking a sufficient curing period, resulting in difficulty in shortening the construction period and reducing the construction cost. It was.

On the other hand, quick lime powder has been used as an inexpensive expansion material for a long time, and it is known that the amount of expansion is increased by combining quick lime powder and anhydrous gypsum powder (for example, Non-Patent Document 1). Improvement of the expansion material utilizing this inexpensive material has been studied, and a technique for obtaining a larger expansion amount by setting the specific surface area and hydration heat generation characteristics of quicklime powder within a predetermined range is disclosed (Patent Document) 4, 5).
Japanese Patent Laid-Open No. 48-12325 Japanese Patent No. 3494238 Japanese Patent Publication No.53-13650 Japanese Patent Application Laid-Open No. 2004-299989 JP 2005-162565 A Masao Sato et al., “On the enhancement effect of gypsum powder on the expansion of“ dead-fired ”lime,” Cement Technology Annual Report, No. 29, pp. 118-121 (1975)

  The present invention is for early demolding concrete that can exhibit sufficient hydration expansion in a concrete structure even after demolding at an early stage after about 2 to 3 days after placing, and can greatly reduce subsequent drying shrinkage and cracking. Quick lime powder for expansive material, expansive material for early demolding concrete containing the quick lime powder, hydraulic bond material using expansive material for early demolding concrete, early demolding concrete and construction of concrete structure using the concrete Provide a method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors are able to sufficiently dry-shrink the concrete even after early casting (after about 2 to 3 days) after casting the concrete. We have found an expansion material for early demolding concrete based on quick lime powder that can express an expansion amount that can be compensated for. Moreover, the quick lime powder used for this early-stage demolding concrete expansion material was characterized, and the appropriate character was found.

That is, the quick lime powder for an expanding material of the present invention is a quick lime powder for an expanding material having a loss on ignition of 6% by mass or less, containing 90% by mass or more of CaO, and having a brain specific surface area of 3000 to 7000 cm ² / g. Thus, the Blime specific surface area of the quicklime powder having a particle size in the range of 90 μm to 1 mm, that is, the specific surface area by nitrogen gas adsorption is 2.0 m ² / g or less. Further, the quick lime powder for inflating material of the present invention is further obtained by using an isothermal conduction calorimeter for a mixed powder of 75 mass% of a mixture of 75 mass% of quick lime powder and 25 mass% of anhydrous gypsum and 25 mass% of ordinary Portland cement. In the hydration exotherm rate curve measured in the above, the second exothermic peak is quicklime powder for inflating material, which appears only after 2 hours after water contact.

  The present invention is also an early-stage demolding concrete expansion material containing quick lime powder for expansion material and anhydrous gypsum powder, wherein the ratio of quick lime: anhydrous gypsum is 30:70 to 90:10. It is an expansion material for concrete.

  The present invention further relates to a concrete composition comprising a hydraulic binder material and water, wherein the hydraulic binder material includes the above-mentioned expansion material and cement, and the content of the expansion material is that of the expansion material and cement. It is an early demolding concrete composition which is 3-9 mass% with respect to the total amount, and has a water / (cement + expansion material) mass ratio of 45-60%.

  Further, the present invention is a concrete which is cast and cured using the above-mentioned early demolding concrete composition, and is demolded until the expansion of the early demolding concrete composition converges, that is, at a material age of 2 to 3 days. It is a construction method of a structure.

  When the expansive material for early-stage demolding concrete of the present invention is used, even if the mold is demolded about 2 to 3 days after casting, the concrete exhibits sufficient hydration expansion, and the subsequent drying shrinkage and cracking are greatly generated. It is possible to obtain early-stage demolding concrete that can be reduced significantly. Such early demolding concrete can shorten the construction period of the concrete structure. Furthermore, the occurrence of cracks in the concrete structure can be suppressed, and the durability of the concrete structure can be improved.

  The quick lime powder for expansion material of the present invention is adjusted so that the hydration activity is suppressed by increasing the firing time by increasing the firing time at a high temperature exceeding 1100 to 1200 ° C., which is called hard calcined quick lime. As its specific characteristics, the loss on ignition is 6% by mass or less, and CaO is contained by 90% by mass or more. The loss on ignition is a small amount of undecomposed calcium carbonate or calcium hydroxide produced on the surface of quick lime particles by so-called weathering due to the hydration or carbonation reaction of calcined quick lime powder with moisture and carbon dioxide in the atmosphere. And weight loss due to decomposition of calcium carbonate when ignited. When the ignition loss is large, the reaction activity of quicklime decreases, so if this is 6% by mass or less, the amount of free calcium oxide contributing to expansion will not decrease. When the CaO is 90% by mass or more, a necessary expansion amount can be obtained. Here, in order to make CaO 90 mass% or more, the purity of the limestone which is a raw material shall be 90 mass% or more. Thereby, since the amount of free CaO in quicklime does not reduce, the fall of the amount of expansion can be suppressed.

The quick lime powder for inflating material of the present invention can be obtained by pulverizing a mass that has been fired at a high temperature as described above. The appropriate powder specific surface area is the range whose Blaine specific surface area (BL specific surface area) prescribed | regulated by JISR5201: 1997 is 3000-7000 cm < ² > / g. In addition, as a character of quicklime powder related to expansion characteristics, the particle size that passes through a sieve with a nominal aperture of 1 mm specified by JIS Z 8801-1: 2000 and remains on a sieve with an aperture of 90 μm specified by the same standard is from 90 μm. The specific surface area (BET specific surface area) by nitrogen gas adsorption of quicklime powder in the range of 1 mm is 2.0 m ² / g or less.

Here, “the BET specific surface area of quicklime powder having a particle size in the range of 90 μm to 1 mm” as defined in the present invention means the degree of firing of the quicklime ingot, which is the raw material of quicklime powder, that is, the degree of densification of the powder This is a numerical value reflecting (porosity), which is different from the particle size (distribution) of the powder and the BET specific surface area of the whole powder, which is a numerical value reflecting the porosity. In the present invention, quicklime is produced by firing limestone, which is a rock mainly composed of calcium carbonate (CaCO ₃ ). During the firing process, the carbonic acid in the limestone is dissociated to produce calcium oxide, and this decarbonation makes the calcined mass porous. As the firing time becomes longer, crystal grains grow due to the progress of sintering and crystal growth, and the ingots become denser. The calcined mass thus obtained is pulverized to obtain quicklime powder. At this time, the BET specific surface area of the whole powder is affected by both the powder particle size distribution and the porosity of the powder particles, but the influence of the porosity appears strongly at the initial stage of sintering, and as the sintering proceeds The effect of porosity is no longer reflected. In other words, for quick lime powder with small crystal grains and a low degree of firing, the BET specific surface area of the whole powder reflects the porosity of the quick lime ingot than the particle size distribution, but with hard calcined quick lime with large crystal grains and a high degree of firing. This is not necessarily the case, and a value reflecting the porosity can be obtained only for the BET specific surface area of quicklime powder having a particle size in the range of 90 μm to 1 mm obtained by sieving.

When the brane specific surface area of quicklime powder exceeds 7000 cm ² / g, the hydration reaction rate becomes too fast, and effective expansion to compensate for shrinkage may not be obtained, but at 7000 cm ² / g or less. In some cases, the hydration reaction rate is an appropriate value, and an effective expansion to compensate for the shrinkage can be obtained. Further, when the specific surface area of the brane is less than 3000 cm ² / g, coarse particles are likely to be generated, and the unhydrated product may be hydrated for a long time to cause a pop-out phenomenon. In the case of 3000 cm ² / g or more, these phenomena are not a problem. In order to control the Blaine specific surface area within the above range, the number of revolutions of the mill, the amount of grinding, etc. in the step of pulverizing quicklime (burned ingot) are controlled.

In addition, when the BET specific surface area of the quick lime powder having a particle size in the range of 90 μm to 1 mm exceeds 2.0 m ² / g, the reaction activity of the quick lime powder becomes too high, the hydration reaction rate increases, and shrinkage occurs. There may be a problem that effective expansion to be compensated cannot be obtained, but these are appropriate values at 2.0 m ² / g or less. In order to control the BET specific surface area to 2.0 m ² / g or less, hard calcined lime having a high firing temperature and a long firing time can be suitably used.

  Further, the quick lime powder for expanding material of the present invention further comprises a mixed powder of 75% by weight of a mixture of 75% by weight of quick lime powder for expanding material and 25% by weight of anhydrous gypsum and 25% by weight of ordinary Portland cement. In the hydration exothermic rate curve measured using a meter, the second exothermic peak is quick lime powder for intumescent material that appears only after 2 hours after water contact. If the second exothermic peak is not shown or it occurs within 2 hours after water contact, it will not be possible to give appropriate expansion during concrete hardening. In addition, the measurement of the isothermal conduction calorimeter occurs when the sample powder and water are put into independent sample containers in the apparatus, and the sample powder and water are mixed in the apparatus by an external operation. Measure the calorific value. Therefore, “water contact” means a point in time when the sample powder comes into contact with water. Although the difference between quicklime that shows the second exothermic peak and quicklime that is not shown is not clear, it is related to the reactivity of quicklime, and when the quicklime touches water and hydrates (first peak) I think that this may be due to film formation, subsequent film destruction, and resumption of hydration (second peak). Accordingly, since the second exothermic peak appears in the hydration exothermic rate curve after 2 hours after water contact, it is effective to control the calcining degree of quicklime.

  The expansion material for early demolding concrete of the present invention includes the above-mentioned quick lime powder and anhydrous gypsum powder. 30-90 mass% is preferable, and, as for the content rate of quicklime powder, 40-80 mass% is more preferable. Although the expansion effect increases with the increase in the content of quicklime powder, the increase in the expansion effect of quicklime becomes small when the content of quicklime powder exceeds 90% by mass. The content of the anhydrous gypsum powder is preferably 10 to 70% by mass, and more preferably 20 to 60% by mass. Therefore, the ratio of quicklime: anhydrite in the expansive material for early demolding concrete is preferably 30:70 to 90:10, and more preferably 40:60 to 80:20.

The anhydrous gypsum powder in the expansive material for early demolding concrete of the present invention may use natural anhydrous gypsum of the quality that is usually used industrially for cement production or anhydrous gypsum produced as a by-product in chemical industrial processes. it can. Moreover, the hydration expansion | swelling of quicklime powder comes to express moderately by using anhydrous gypsum powder together. The purity of calcium sulfate in the anhydrous gypsum powder is preferably about 50 to 57% by mass based on SO ₃ , and a small amount, for example, about 5% by mass of dihydrate gypsum may coexist. To generate hydration expansion of quicklime powder more effectively, Blaine specific surface area of the anhydrite powder 3000 cm ² / g or more, preferably in the range of 3500~7000cm ² / g. If the Blaine specific surface area is out of this range, it is not preferable because the hydration rate of the quicklime powder is not properly adjusted.

  The expansion material for early demolding concrete of the present invention preferably comprises quick lime powder and anhydrous gypsum powder. It is preferable not to contain an aluminate-based expansion component such as Auin because it expands in the long term.

  Moreover, this invention is an early demolding hydraulic binder material containing said expansion | swelling material and cement. As the cement, ordinary Portland cement, early-strength Portland cement, intermediate Portland cement, or mixed cement can be used.

In the early demolding hydraulic binder material of the present invention, the amount of the expansion material added to the total amount of the early demolding concrete expansion material and cement is the component of the expansion material, particularly quick lime powder and anhydrous gypsum powder. Although it varies depending on the ratio, it is 3 to 9% by mass, more preferably 4 to 8% by mass. If the amount is less than 3% by mass, the amount of expansion sufficient to compensate for shrinkage cannot be expressed. If the amount exceeds 9% by mass, the strength of the concrete structure may be reduced. There is no problem. The unit amount of the expansion material in the concrete varies depending on the unit cement amount, but generally corresponds to 10 to ³⁰ kg / m ³ .

  The concrete of the present invention can be obtained by kneading the above hydraulic binding material with aggregate, water and an AE water reducing agent. The mass ratio of water / (cement + expansion material) in the concrete can be suitably used in the range of 0.45 to 0.60.

  Furthermore, the present invention is a method for constructing a concrete structure, wherein the concrete is cast and cured using the above concrete, and is demolded at a material age of 2 to 3 days when the expansion of the concrete converges. Even if the concrete of the present invention is demolded at an early age such as 2 to 3 days after placement, it is possible to construct an excellent concrete structure in which shrinkage cracking hardly occurs.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  Five types of quicklime powders having different characteristics shown in Table 1 were used. A1 and A2 are the above-mentioned hard calcined quicklime, and A4 and A5 are called soft calcined quicklime. Soft calcined lime is produced by calcining limestone at a high temperature of 900 to 1400 ° C. in a relatively short time, and has a large specific surface area and high reactivity. A3 is quick lime powder that has been significantly weathered and has a loss on ignition of as much as 13%.

As anhydrous gypsum powder, hydrofluoric acid anhydrous gypsum shown in Table 2 was used.

  As the cement, ordinary Portland cement (sold by Ube Mitsubishi Cement Co., Ltd.) conforming to JIS R 5210: 2003 was used.

  A powder with a particle size of 90 μm to 1 mm was collected after passing the quick lime powder described in Table 1 through a nominal aperture of 1 mm defined by JIS Z8801-1: 2000 and remaining on a sieve having a nominal aperture of 90 μm defined by the same standard. . The specific surface area (BET specific surface area) of the powder by nitrogen gas adsorption was measured. BELSORP-mini manufactured by Nippon Bell Co., Ltd. was used for the measurement. Moreover, the scanning electron microscope (SEM) photograph of the powder particle | grains which remain | survives on the 90 micrometer sieve of quicklime classification A1 and A4 is shown in FIG. 1 and FIG. Here, after the particles remaining on the sieve were embedded in an epoxy resin, they were cut and polished, and SEM observation was performed at a magnification of 3000 times. In A1, quicklime crystal grains grow well, while in A4, no remarkable growth of quicklime is observed, and it is recognized that fine voids exist on the particle surface.

  Moreover, the mixture powder which mixed 75 mass% of quicklime powder of Table 1 and 25 mass% of anhydrous gypsum of Table 2, and the sample powder which mixed 75 mass% of this mixture and 25 mass% of normal Portland cement were prepared. About these both, the hydration exothermic rate in 20 degreeC was measured using the twin type | mold conduction calorimeter (Tokyo Riko Co., Ltd. TCC-26). The measurement conditions were a water powder ratio of 5, a powder of 2 g, and a water of 10 g, and distilled water was used as the water.

  In accordance with JIS A 6202: 1997 Annex 1 in accordance with the expansibility test method of expansive material using mortar, the test specimen was prepared and measured, and the rate of change in mortar length at age 7 days under restraint conditions The expandability of the expansion material was evaluated.

  In FIG. 3, the hydration exothermic rate curve of the mixture of 75 mass% of quicklime powder of Table 1 and 25 mass% of anhydrous gypsum of Table 2 is shown. Moreover, the hydration exothermic rate curve at the time of mixing 75 mass% of this mixture and 25 mass% of normal Portland cement is shown in FIG.

  Table 3 shows a BET specific surface area of quick lime powder having a particle size ranging from 90 μm to 1 mm, a mixed powder of 75% by weight of a mixture of 75% by weight of quick lime powder and 25% by weight of anhydrous gypsum and 25% by weight of ordinary Portland cement. The second peak appearance time in the hydration exothermic rate curve using an isothermal conduction calorimeter is shown.

  As shown in FIG. 3, when any quicklime powder was used, the first exothermic peak was shown within 1 hour after water contact, and the second peak did not appear thereafter.

  As shown in FIG. 4, in the hydration exothermic rate curve measured under the condition of mixing ordinary Portland cement, unlike FIG. 3, the first exothermic peak is shown within 1 hour after water contact, but then the second exothermic peak is reached. It turns out that there exists quicklime which shows a peak (A1, A2). In other words, it suggests that the hydration reaction of quicklime is affected by the coexistence of cement, and that the effect varies depending on the quicklime.

  The inventors examined in detail the relationship between the heat generation characteristics and the expansion characteristics of the quicklime character and expansion material. As a result, as shown in Table 3, it was found that the BET specific surface area of quick lime powder having a particle size of 90 μm to 1 mm is related to the appearance time of the second exothermic peak in the hydration exothermic rate.

  Table 4 shows the expansion characteristics when the kind of quicklime powder and the blending ratio of quicklime powder and anhydrous gypsum powder are changed.

  As shown in Table 4 and FIG. 5, in a fixed condition where the mixing ratio of quicklime: anhydrite is 75:25, when the quicklime powder (A1) is used, the rate of change in length is the largest (Example 1), then Quicklime powder (A2) was large (Example 2), and quicklime powder (A3) to quicklime powder (A5) showed almost the same value (Comparative Examples 1 to 3).

Further, comparing the BET specific surface area of the quick lime powder having a particle size of 90 μm to 1 mm shown in Table 3 with the appearance time of the second exothermic peak of the hydration heat generation rate, the quick lime powder having a large expansion has a particle size of It can be seen that the BET specific surface area of the quicklime powder in the range of 90 μm to 1 mm is 2.0 m ² / g or less, and the second exothermic peak appears after 2 hours. This relationship cannot be found from the BET specific surface area of the entire quick lime powder shown in Table 1, and in particular, for the quick lime powder having a particle size in the range of 90 μm to 1 mm, which is considered to maintain the porosity of the quick lime calcined mass. It can be known and evaluated only by the BET specific surface area and the hydration exothermic rate curve measured under the condition where the interaction with the cement occurs.

  As for the mortar using the expansion material prepared by changing the blending ratio (mass basis) of the quicklime powder (A1) and the anhydrous gypsum powder (B1), the length change increased with the increase of the ratio of the quicklime powder. Moreover, favorable expansion | swelling was obtained in the range whose quicklime powder ratio is 30 mass% to 90 mass%. In addition, when the ratio of the quicklime powder of an expansion material is 90 mass%, the mixing ratio of quicklime powder is a length change rate substantially the same as 70 mass%, and even if it mix | blends a large amount of quicklime powder, expansion | swelling of expansion | swelling is carried out. It can be seen that no further increase can be expected. Practically, it can be said that the ratio of quicklime powder in the expanded material is preferably 40 to 80% by mass.

  In FIG. 6, the time-dependent change of the mortar length change using the expansion material prepared by changing the mixture ratio (mass basis) of quicklime powder (A1) and anhydrous gypsum powder (B1) is shown. From this, it can be seen that the expansion has converged within the age of 3 days. That is, since the expansion reaction converges in about 2 to 3 days after placing the concrete, the mold can be removed at an early stage.

  The expansion characteristics when using the expansion material of the present invention were evaluated by preparing concrete compositions. Table 5 shows the materials used, and Table 6 shows the concrete composition.

  Concrete is forced to a capacity of 50 L, and coarse aggregate, fine aggregate, cement and expansion material are put into a shaft mixer, and after kneading for 30 seconds, a predetermined amount (0.25% by mass with respect to the powder) AE water reducing agent) was added and mixed for 90 seconds. The kneading amount was 45L.

  As shown in FIG. 7, the expansion characteristic is a 10 × 10 × 40 cm concrete specimen restrained by a restraint composed of a round steel (PC steel bar) and a 19 mm-thick steel plate disposed at both ends thereof. Evaluated. The strain was measured using a strain gauge attached to the center of the round steel. Three kinds of round steels having a diameter of 6 mm, 10 mm, and 20 mm were used, and the amount of expansion was measured under the condition that the ratio of restrained steel was changed to 0.2, 0.8, and 3.2%. The kneaded concrete was placed in a mold with a restraint shown in FIG. 7 and compacted, and then the mold was removed after 10 hours. Moreover, in order to measure the unconstrained expansion amount, in order to eliminate the influence of restraint from the mold as shown in FIG. 8, a mold with a Teflon sheet and a polystyrene board was used, and an embedded strain gauge was used. Was embedded in concrete and the strain was measured. Under either restraint or unconstrained condition, from the time of placing until the end of measurement, the concrete specimen was cured with a wrap so as not to cause drying, and the strain was measured.

  FIG. 9 shows the rate of change in length of concrete using the expansion material of the present invention. From this, it was confirmed that very large expansion was obtained under unconstrained conditions, and that expansion was also exhibited under conditions where large restraints were applied. Moreover, it has confirmed that expansion | swelling substantially converged by material age 1 day.

  By using the expandable material of the present invention, for example, a concrete structure or member that does not easily crack due to drying shrinkage is constructed even after demolding after a very short curing period such as 2 to 3 days of age. be able to.

It is a figure which shows the reflected-electron image which observed the quicklime powder particle | grains A1 which remained on the 90 micrometer sieve with the scanning electron microscope. It is a figure which shows the reflected-electron image which observed the quicklime powder particle | grains A4 which remained on the 90 micrometer sieve with the scanning electron microscope. It is a figure which shows the hydration exothermic rate curve of the expansion | swelling material which mixed 75 mass% of various quicklime powders, and 25 mass% of anhydrous gypsum. It is a figure which shows the hydration exothermic rate curve of the mixed powder of 75 mass% of mixtures of various quicklime powders 75 mass% and anhydrous gypsum 25 mass%, and normal Portland cement 25 mass%. It is a figure which shows the length change rate of the mortar using the expansion material which mixed 75 mass% of various quicklime powders, and 25 mass% of anhydrous gypsum. It is a figure which shows the length change rate of the mortar using the expansion material prepared by changing these ratios (mass basis) using quicklime powder (A1) and anhydrous gypsum powder (B1). It is a figure which shows the outline | summary of the restraint tool for restraint expansion-strain measurement, and the specimen for restraint expansion-strain test. It is a figure which shows the outline | summary of the test piece for unconstrained strain measurement. It is a figure which shows the length change in the unconstrained and restraint conditions of the concrete which added the expansion | swelling material.

Claims (5)

Quick lime powder for inflating material containing 6% by mass or less of ignition loss and 90% by mass or more of CaO and having a Blaine specific surface area of 3000 to 7000 cm ² / g and having a particle size in the range of 90 μm to 1 mm. Quick lime powder for expanding material, wherein the powder has a BET specific surface area of 2.0 m ² / g or less.   The second exothermic peak in the hydration exothermic rate curve obtained by measuring 75% by mass of a mixture of 75% by mass of quicklime powder and 25% by mass of anhydrous gypsum and 25% by mass of ordinary Portland cement using an isothermal conduction calorimeter The quicklime powder for inflatable materials according to claim 1, which appears only after 2 hours after water contact.   An early demolding concrete expansion material comprising the quick lime powder for expansion material according to claim 1 or 2 and anhydrous gypsum powder, wherein the ratio of quick lime: anhydrous gypsum is 30:70 to 90:10. Expansion material for mold concrete.   A concrete composition comprising a hydraulic binder material and water, wherein the hydraulic binder material comprises the expansion material according to claim 3 and cement, and the content of the expansion material is a total amount of the expansion material and cement. An early demolding concrete composition having a water / (cement + expansion material) mass ratio of 45 to 60% with respect to 3 to 9% by mass.   A method for constructing a concrete structure, wherein the early demolding concrete composition according to claim 4 is cast and cured, and demolding by the time when the expansion of the early demolding concrete composition converges.