JP2011207651A - Smart materialized artificial lightweight aggregate, method for producing the same and concrete-kneaded matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the technique by which the drying of a cement matrix is suppressed, and the increase of the durability in a concrete structure is brought out by using a porous artificial lightweight coarse aggregate which can be substituted for the whole or most of coarse aggregate to be blended into concrete.SOLUTION: The smart materialized artificial lightweight aggregate is obtained by storing water and a silicate-based chemical reacted with the hydration product of cement into the internal voids of a porous artificial aggregate obtained by firing with coal ash and shale fine powder as the main raw material. Particularly, as the chemical, the one present in a gelled state at least at the part exposed to the surface is a suitable object.

Description

  The present invention relates to an artificial lightweight aggregate that has been made into a smart material (SLA) by impregnating and storing water and a drug in a void of a porous artificial lightweight aggregate, a manufacturing method thereof, and a smart material thereof The present invention relates to a concrete kneaded material using modified artificial lightweight aggregate.

  There is a concern that the durability of concrete in the structure will decrease as drying and aging progress. In recent years, in order to improve the durability of concrete structures, various techniques have been developed to increase the strength and durability of concrete by using a reduction in water-cement ratio and the addition of admixtures. On the other hand, concrete undergoes a drying phenomenon due to moisture movement from the inside depending on curing conditions and external environmental conditions, and generates visible cracks, micro-level micro voids and micro cracks (hereinafter referred to as micro cracks). In order to suppress such fine voids and microcracks in concrete, sufficient curing after placing is required, but in practice, long-term curing is often difficult.

  If moisture can be gradually and stably supplied from the inside of the concrete into the cement matrix, it is considered that the trouble caused by the drying phenomenon can be suppressed. At the same time, if a chemical that reacts with the substances in the cement matrix to form a dense reaction product can be gradually and stably supplied from inside the concrete, it is considered effective for improving the durability of the concrete structure. It is done.

  Patent Document 1 discloses a technique for generating a gel substance on the surface layer portion of a porous lightweight aggregate. This gel substance functions as a “waterproof plug” (page 3, left column, line 17 of Patent Document 1), and the lightweight aggregate is resistant to water absorption so that moisture that causes frost damage does not enter the lightweight aggregate. It imparts sex. Therefore, this technique cannot supply moisture and other substances into the cement matrix from inside the concrete.

  Patent Document 2 describes a technique in which a porous aggregate body is impregnated with a repair liquid that closes a crack generated in concrete. This aggregate is covered with a coating film. When a crack occurs in the concrete, the aggregate coating film located at the crack is destroyed, and water glass and various resin repair solutions are released into the crack. (Patent Document 2, paragraph 0015, FIG. 2). Therefore, this technique cannot gradually supply moisture and chemicals into the cement matrix.

Patent Document 3 discloses a technique in which an aggregate includes a chemical that reacts with calcium hydroxide in a hardened cement body to generate a water-insoluble substance. As one of the techniques, it is described that a drug is impregnated into an aggregate of a porous body, and an example thereof is shown as Example 1. However, only 150 of this drug-containing aggregate is added to 1 m ^{3 of} concrete (see the same paragraph 0028), and the particles of the drug-containing aggregate are lower than the other aggregate particles in the hardened concrete. It is thought that it is dispersed by density. According to the technique of Patent Document 3, since the self-healing substance is gradually released and mainly reacts with calcium hydroxide precipitated after the cement component is hardened, the initial purpose (inhibition of hydration reaction, large mixer) It is said that self-healing action can be achieved in the hardened cement body by avoiding contamination of the cement. However, Patent Document 3 does not disclose a technique that can replace most of the coarse aggregate blended in the concrete with a drug-containing aggregate and can suppress the drying of the cement matrix over a long period of time.

  Patent Document 4 discloses a chemical holding material in which a drug is held in a porous aggregate obtained by firing expansive shale. As an example of using this chemical retaining material for aggregates for concrete, artificial aggregates impregnated with surface tension relaxants such as lower alcohol compounds and glycol ethers are mixed into conventional sand and fine aggregates. It is described that the concrete can be manufactured, thereby reducing the shrinkage of the concrete product due to hardening (paragraph 0016 of Patent Document 4). However, no method has been shown to realize the suppression of drying of the cement matrix and the densification of the structure.

Japanese Patent Publication No. 6-88853 JP-A-10-194801 JP 2002-97045 A JP 2004-224728 A

Hiroshi Kasai, 3 others, “Properties of high-performance concrete using coal ash artificial aggregate (J-light)”, Kashima Giken annual report, Vol.53, (2005), p.157-166

  The present invention uses a porous artificial lightweight coarse aggregate that can replace all or most of the coarse aggregate to be blended in concrete, thereby suppressing the drying of the cement matrix and increasing the durability of the concrete structure. Is to provide technology that brings

  The above-mentioned purpose is a smart material-made artificial light weight that contains water and silicic acid-based chemicals that react with hydrated products of cement in the internal voids of porous artificial aggregates fired with coal ash and shale fine powder as the main raw materials. Achieved by aggregate. In particular, there is provided a drug that exists in a gelled state at least at a portion exposed on the surface. The inside may be completely gelled.

The porous artificial bone (material) for storing the drug has a moisture content of 30% or less, an absolute dry density of 2.5 g / cm ³ or less, and a maximum diameter of voids observed in the cross section of 2.0 mm or less. Is exemplified as a suitable target. The maximum diameter of the void is determined by calculating the equivalent circle diameter by obtaining the area of each void appearing in the cross-sectional image and adopting the maximum value.

  As a manufacturing method of the above-mentioned smart materialized artificial lightweight aggregate, after freeze-drying the porous artificial aggregate calcined with coal ash and shale fine powder as the main raw material, the drug is added under reduced pressure together with an aqueous solvent. A technique is provided for impregnating the internal voids of the artificial aggregate to the maximum impregnation rate. In the case of gelling the chemical solution, a technique of bringing the artificial bone material impregnated with the drug into contact with the gelling agent is employed.

  When a concrete kneaded material is obtained using the above-mentioned smart materialized artificial lightweight aggregate, it is preferable to use the smart materialized artificial lightweight aggregate in 80 to 100% by mass of the total coarse aggregate.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the micro crack by aged deterioration of a concrete structure can be suppressed, and it becomes possible to achieve high durability at a comparatively low cost in the concrete structure of various uses.

The conceptual diagram which shows the mechanism in which a concrete structure is made highly durable by the smart material-ized artificial lightweight aggregate. The figure which shows the structure of an isothermal moisture release apparatus. The graph which shows the impregnation rate measurement result using a vacuum impregnation method. The graph which illustrates the time-dependent change of a moisture moisture release rate. The graph which shows the relationship between relative humidity and an equilibrium impregnation rate. The graph which shows the relationship between relative humidity and a diffusion coefficient (calculation result). The figure which shows the test body preparation condition for relative humidity and a dry strain measurement. SEM reflected electron image showing an example of microcrack observation. The graph which shows distribution of the relative humidity inside a test body. The graph which shows the measurement result of the dry distortion of 10 mm in depth from a dry surface. The graph which shows the measurement result of compressive strength. The graph which shows the measurement result of a micro space | gap and a micro crack. The graph which shows a gas permeability test result. The graph which shows a promotion neutralization test result. The graph which shows the relationship between the acceleration | stimulation neutralization depth and the fine space | gap and microcrack in the depth of 10 mm of a test body. An example of the cross-sectional SEM photograph of the porous artificial bone material (raw material) applied to this invention.

(Porous artificial aggregate)
In the present invention, a porous artificial bone material fired using coal ash and shale fine powder as main raw materials is used as a material for storing a drug described later. Coal ash can be used as an industrial by-product. An artificial aggregate obtained by baking the above raw material at a high temperature and then slowly cooling it to room temperature is chemically stable and has a strength that can be used as a lightweight aggregate. In particular, the water content is 30% or less (preferably 10 to 25%), the absolute dry density is 2.5 g / cm ³ or less (preferably 1.0 to 2.0 g / cm ³ ), and the voids observed in the cross section The thing with the largest diameter of 2.0 mm or less is illustrated as a suitable object. In particular, the gap having a maximum diameter of less than 0.5 mm is more suitable, and the gap may be managed so as to be 0.3 mm or less. As this type of artificial aggregate, for example, a trade name developed by the applicants; J Lite (Non-patent Document 1) can be applied.

  FIG. 16 illustrates a cross-sectional SEM photograph of an artificial lightweight aggregate applicable in the present invention. The left and right pictures are different types of artificial lightweight aggregates. It has many voids, and the maximum diameter of the voids observed in the cross section is 2.0 mm or less, and especially the left one (J light) is extremely fine.

[Drug]
Silica-based chemicals that react with cement hydration products are used as the chemicals stored in the gaps in the artificial aggregate (material). For example, active silica or colloidal silica from which alkali has been removed from a ground improvement material or a grout material, or a surface reinforcing agent for concrete can be used. It is preferably used as a chemical solution having a silicic acid (SiO ₂ ) concentration in an aqueous solvent of 40% or less (preferably 10 to 35%), low viscosity, and easy to impregnate the artificial bone. The water in the aqueous solvent impregnated into the aggregate with the chemical becomes a water supply source for maintaining the water retention of the cement matrix. The silicic acid component reacts with the hydrated product of the cement, and the cement matrix is densified by the reaction product. In addition, a reactive drug that has not reacted in the initial stage contributes to the persistence of the reaction over a long period of time.

  As other chemicals, a high water retention agent can be added. Examples of the high water retention agent include one-component or two-component special thickeners that react with water, and examples include two-component thickeners of alkylallylsulfonate and alkylammonium salts. .

[Manufacturing method of smart material-made artificial lightweight aggregate]
When impregnating the internal space of the porous artificial bone with the drug, heat the porous artificial bone (raw material) or freeze-dry it (F-Dry), It is preferable to employ a method of supplying the drug to the particles of the porous artificial aggregate together with the water solvent. It is preferable that the viscosity is low at the time of impregnation, but as a product of a smart material-made artificial lightweight aggregate, it is preferable that the impregnated material is gelled because it is easy to handle. As the gelation treatment, a technique of bringing the artificial bone material impregnated with the drug into contact with the gelling agent can be suitably employed. Thereby, the smart material-ized artificial lightweight aggregate which exists in the state which the chemical | medical agent exposed to the aggregate particle surface at least gelatinized can be obtained. Examples of the gelling agent include sodium hydrogen carbonate (NaHCO ₃ ), alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra), carbon dioxide (CO ₂ ), and the like. The concentration of these gelling agents is preferably extremely thin.

[Concrete mix]
The smart material-made artificial lightweight aggregate obtained as described above inherently has characteristics as an artificial lightweight aggregate. Therefore, all or most of coarse aggregate (for example, 80 mass) in various concretes. % Or more) can be replaced with the artificial material lightweight aggregate. The smart materialized artificial lightweight aggregate may be kneaded by the same technique as that of a normal artificial lightweight aggregate to obtain a concrete kneaded product. As powder components, fly ash, silica fume, blast furnace slag, and the like, which are industrial by-products, may be blended as cement substitutes.

  FIG. 1 conceptually shows the mechanism by which a concrete structure is made highly durable according to the present invention.

We made an artificial lightweight aggregate made into a smart material and investigated its characteristics.
1. Experimental design Table 1 shows the experimental elements and levels. One type of artificial lightweight aggregate and three types of impregnation solutions were used. Chemical solution A is an ultrafine silicic acid solution with a concentration of 30%, and chemical solution B is impregnated with chemical solution A and then immersed in an aqueous solution of sodium hydrogencarbonate (NaHCO ₃ ) (concentration 0.2%) for gelation. Is intended.

2. Materials Used and Various Test Methods Artificial lightweight aggregates used were artificial lightweight aggregates (J-light) with an absolute dry density of 1.53 g / cm ³ made mainly of coal ash and shale fine powder.
(1) Impregnation rate test (vacuum impregnation method)
In the impregnation rate test, a vacuum impregnation method was used to impregnate all the voids inside the artificial lightweight aggregate with the solution. Artificial lightweight aggregate is freeze-dried (F-Dry) for 24 hours. Three dry samples of about 500 g are put in a container and the solution is supplied in a vacuum state, and the mass of the sample becomes constant. Until impregnation. The impregnation rate was a ratio obtained by dividing the surface dry mass of the impregnated sample by the absolute dry mass.

(2) Isothermal moisture release test The isothermal moisture release test was performed using a device composed of a shunt-type relative humidity generator, an electronic balance, and a personal computer. A block diagram of the test apparatus is shown in FIG. A sample of 50 g prepared using the vacuum impregnation method was placed in a stainless steel basket, the atmosphere temperature in the sample chamber was set to 20 ° C., and air with a predetermined relative humidity was supplied at an accuracy of ± 1% at 10 L / min. The relative humidity was 95%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 0%. During the test, the change in mass due to moisture desorption of the artificial lightweight aggregate impregnated with the solution was continuously measured.

3. Experimental results and discussion (1) Impregnation rate The results of the impregnation rate of water and chemicals using the vacuum impregnation method are shown in FIG. The impregnation rate of each sample was approximately equal at about 18% (wt /%). It was confirmed that impregnation was possible up to an impregnation rate of about 18% by using the vacuum impregnation method.

(2) Isothermal moisture release test FIG. 4 illustrates the change in moisture moisture release rate of an artificial lightweight aggregate sample impregnated with water and a chemical solution. The moisture moisture release rate is a ratio obtained by dividing the amount of moisture dissipated from the impregnated sample by the surface dry mass. Although the moisture moisture release rate showed a tendency to gradually increase with the passage of time, it was confirmed that the artificial lightweight aggregate impregnated with the chemical solution is superior in water retention as compared with the artificial lightweight aggregate impregnated with water.

Curve fitting was performed using the following equation (1) from the result of the moisture moisture release rate of each sample, and the equilibrium impregnation rate and the moisture diffusion coefficient were obtained. The equilibrium impregnation rate is defined since the impregnation solution is a chemical solution other than water, and corresponds to the equilibrium water content.
m (t) = a [1-bexp (−ct)] (1)
Here, m (t) is an estimated value (wt /%) of the moisture desorption rate after the elapsed time t, a is an estimated value (wt /%) of the moisture desorption rate after an infinite time has elapsed, and b is the sample The coefficient relating to the shape (spherical), c is a coefficient obtained by the equation of c = D _θ π ² / A ² (A is the radius of the sample, mm), the moisture diffusion coefficient (D _θ ). Since the coefficient a represents the equilibrium impregnation rate (θe) estimated by moisture release, the equilibrium impregnation rate (θr) remaining in the artificial lightweight aggregate was calculated using the following equation (2).
θr = Mc _max −θe (2)
Here, Mc _max is an impregnation rate by a vacuum impregnation method, and θe is an equilibrium impregnation rate estimated by moisture release.

  The result of the equilibrium impregnation rate is shown in FIG. In any sample, the equilibrium impregnation rate tends to decrease as the relative humidity decreases, but the equilibrium impregnation rate of the artificial lightweight aggregate impregnated with the chemical solution is 80% relative humidity compared to the artificial lightweight aggregate impregnated with water. It can be seen that it is about twice as large in the following regions and is excellent in moisture retention.

  The calculation result of the diffusion coefficient is shown in FIG. Since there is no great difference in the diffusion coefficient of any of the samples, it is considered that the artificial lightweight aggregate impregnated with the chemical solution has excellent water retention mainly due to the high equilibrium impregnation rate.

We made a concrete kneaded material using artificial lightweight aggregate made of smart material and investigated the properties of the concrete obtained by placing it.
1. Experimental design Table 2 shows the experimental factors and levels. The water-cement ratio is 50%, and concrete is natural concrete using natural aggregate, lightweight concrete using water-impregnated artificial lightweight aggregate, artificial lightweight aggregate (SLA) impregnated with the above chemicals A and B A total of five types of concrete were used: concrete using SLA, and concrete in which 10% of the volume of fine aggregate was replaced with fly ash using SLA. Here, the concrete using SLA is called SLA concrete. Three types of symbols JC, JCV, and JCF described in Table 2 correspond to examples of the present invention. Test items were fresh test, relative humidity, dry strain, compressive strength, fine voids and microcracks, air permeability, and accelerated neutralization test.

2. Mixing and materials used Table 3 shows the concrete mixing and Table 4 shows the physical properties of the materials used. Based on the mix of ordinary concrete using natural aggregate, the unit water amount, unit cement amount and fine aggregate amount were fixed, and the volume of coarse aggregate was replaced with artificial lightweight aggregate.

3. Test Items and Methods (1) Kneading and Various Fresh Tests For mixing of concrete, a 100 L pan mixer was used for each preparation, and the materials were all added and kneaded for 90 seconds. After kneading, fresh tests such as slump, air volume, and concrete temperature were performed, and test specimens used for each test were prepared. Table 5 shows the test body dimensions and curing conditions in the following test items.

(2) Relative humidity and dry strain The test body for measuring relative humidity and dry strain was 100 × 100 × 100 mm. FIG. 7 shows the status of the preparation of both specimens. A test specimen for measuring relative humidity was a brass bar (φ7 mm × 100 m) fixed to the mold, and the brass bar was extracted just before being hardened after placing the concrete and sealed at 20 ° C. until the age of 7 days. After that, a high-precision ultra-small humidity sensor (manufactured by Shineisha, polymer resistance type, THP-B6, φ6 mm, ± 3% RH) is attached, and five of the six specimens are sealed using aluminum foil tape. The whole surface was air-dried under the conditions of 20 ° C. and 60% relative humidity. The test piece for dry strain measurement was equipped with a dry strain gauge (manufactured by Kyowa Dengyo Co., Ltd., single-shaft 2-wire type, KM-30-120-H1-11, length 30 mm) and cast concrete. After performing sealing curing at 20 ° C. until 7th day, one-sided air drying curing was performed under the conditions of 20 ° C. and 60% relative humidity. In both cases, relative humidity and strain at a depth of 10, 50, and 90 mm from the dry surface were measured at a predetermined age.

(3) Compressive strength Two types of specimens for compressive strength were used: a cylindrical specimen having a diameter of φ100 × 200 mm and a prismatic specimen having a size of 100 × 100 × 100 mm. Cylindrical test specimens were prepared using a summit mold, and the curing conditions were two types: standard water curing and air drying curing at 20 ° C. and 60% relative humidity after 20 ° C. sealing up to 7 days of age. A prismatic specimen was prepared using a copper mold, and was subjected to one-sided air-curing at 20 ° C. and 60% relative humidity after standard water curing and 20 ° C. sealing curing until the age of 7 days. The compressive strength test was performed according to JIS A1108.

(4) Fine voids and microcracks Test specimens for measuring fine voids and microcracks were 100 x 100 x 100 mm, sealed and cured at 20 ° C until the age of 7 days, and then air-dried at 20 ° C and 60% relative humidity. Went. Samples for measurement of microscopic voids and microcracks were obtained by cutting and collecting a cubic sample of about 12 × 12 × 12 mm using a diamond cutter at a depth of 10, 50, 90 mm from the dry surface at the age of 28 days, It was immersed for 24 hours and subjected to nitrogen drying. The sample is embedded in a low-viscosity epoxy resin, and the observation surface is dry-polished using water-resistant abrasive paper # 1000, # 2000, # 3000, # 5000 and a diamond paste of 0.25 μm to give carbon conductivity to give electrical conductivity. Carried out. The measurement was performed by observing a backscattered electron image (BEI) using a scanning electron microscope (SEM) equipped with a backscattered electron detector. The observation conditions of the reflected electron image were an acceleration voltage of 15 keV, a working discrepancy of 10 mm, and a magnification of 500. The observation range was a cement matrix portion of the sample (12 × 12 × 12 mm), and was randomly set at 10 locations on the age of 28 days. The size of one image is 245 × 184 μm and 2048 × 1536 pixels, and one pixel is 0.12 μm. The observed backscattered electron image was subjected to image processing using the difference in luminance due to the difference in atomic number, and separated into unhydrated cement, hydrated product, and voids (diameter of 10 μm or less). In addition, the fine voids and microcracks in the void image were discriminated by particle analysis (resolution: 0.5 μm), and the average area was calculated. An example of microcrack observation by SEM reflected electron images is shown in FIG.

(5) Air permeability test and accelerated neutralization test The air permeability test was performed in accordance with RIREM TC116-PCD using a PVC mold of φ150 mm x 50 mm, and the thickness of the test body in other tests was 100 mm. In order to match them, the casting surface and bottom surface of the two specimens were stacked and sealed after demolding, and sealed at 20 ° C. until the age of 7 days. Then, one surface drying (bottom surface) was performed on 20 degreeC and 60% of relative humidity conditions. In the test, nitrogen gas was used, and the air permeability coefficient was obtained from the flow rate after the nitrogen gas flow became steady.
The accelerated neutralization test body was 100 × 100 × 400 mm, sealed and cured at 20 ° C. until the age of 7 days, and then subjected to side-surface air curing at 20 ° C. and a relative humidity of 60% until the age of 28 days. The test conditions were a temperature of 20 ± 2 ° C., a relative humidity of 60 ± 5%, and a CO ₂ concentration of 5 ± 0.2%. The measuring method of the accelerated neutralization depth was based on JIS A1152, and was measured at a predetermined age.

4). Experimental results and discussion (1) Fresh test Table 6 shows the results of the fresh test of concrete. The same amount of high-performance water reducing agent was added. The slump for all formulations showed 20 ± 1.5 cm and no difference between the formulations was observed. In addition, the amount of air was in the range of 4.5 ± 1.0% for all formulations, and no significant difference was observed between SLA concrete and ordinary concrete.

(2) Relative humidity and drying strain FIG. 9 shows the distribution of relative humidity inside the specimen. The relative humidity distribution in all the blended concrete tended to decrease with age, from the inside of the specimen toward the dry surface. The relative humidity of ordinary concrete decreased sharply from the dry surface from the age of 7 days when the drying was started, and the deepest part of the test specimen tended to be less than 100% relative humidity after the age of 28 days. The relative humidity distribution of SLA concrete and lightweight concrete at age 91 days was 80% at a depth of 10 mm from the dry surface, 100% in the interior after 50 mm, and a relative humidity of 10% or more larger than that of ordinary concrete. It was confirmed that SLA concrete was excellent in water retention compared to ordinary concrete, as was lightweight concrete.

  FIG. 10 shows the measurement results of the drying strain having a depth of 10 mm from the dry surface. The drying strain of ordinary concrete increased rapidly from the age of 7 days at the start of drying, and was about −600 μm at the age of 91 days. The dry strain of lightweight concrete and SLA concrete gradually increased with age, and was about −200 μ at the age of 91 days, showing a difference of 400 μ compared with ordinary concrete. SLA concrete, like lightweight concrete, was confirmed to have reduced drying strain because it has higher water retention than normal concrete.

(3) Compressive strength The measurement result of the compressive strength is shown in FIG. The compressive strength of the standard underwater curing of the cylindrical specimens tends to increase with age in all the concretes. Among SLA concrete, JC and JCV are about 10-15% lower than ordinary concrete, but JCF is 5-5%. It was about 10% higher. Moreover, the compressive strength of SLA concrete tended to exceed that of lightweight concrete. The compressive strength of the air-cured curing at 20 ° C. and 60% relative humidity of the cylindrical specimen was slightly decreased with the age of ordinary concrete, but lighter concrete and SLA concrete showed a tendency to increase, and the age of 91 In the day, it increased more than equivalent to ordinary concrete. This is considered that the moisture of the artificial lightweight aggregate was released as the material ages and contributed to the hydration reaction of the cement. In addition, the compressive strength of the standard underwater curing of the prismatic specimens was the same tendency as that of the cylindrical specimens in all concretes. Compared to lightweight concrete, the results were equivalent or better. This is thought to be because the fine structure was densified by the chemical solution reacting with the hydrated product together with the continuous water supply due to the high water retention of SLA concrete, leading to an increase in compressive strength.

(4) Fine voids and microcracks The measurement results of fine voids and microcracks on the age of 28 days are shown in FIG. Many fine voids and microcracks are present in the vicinity of the dry surface from the inside of the test specimen, and many are generated with drying. SLA concrete showed a tendency to reduce fine voids and microcracks compared to ordinary concrete, and in particular, the microcrack suppression performance near the surface was superior to that of lightweight concrete.

(5) Air permeability test and accelerated neutralization test The results of the air permeability test are shown in FIG. The air permeability coefficient tended to decrease with age. The air permeability coefficient of SLA concrete tended to be an order of magnitude smaller than that of ordinary concrete, and a result excellent in air resistance was obtained.
The results of the accelerated neutralization test are shown in FIG. The accelerated neutralization depth tended to become deeper with age. The accelerated neutralization depth of SLA concrete was 1/2 or less that of ordinary concrete, which was smaller than that of lightweight concrete. This is because SLA concrete has high water retention, and further contributes to the reduction of fine voids and microcracks due to the reaction between the chemical solution and the hydrated product, and the accelerated neutralization depth is considered to have decreased. Here, since the neutralization proceeds from the surface of the concrete, the relationship between the accelerated neutralization depth and the fine voids and microcracks at a depth of 10 mm of the specimen was examined. The result is shown in FIG. The accelerated neutralization depth is considered to have an influence on the neutralization rate from the relationship with the fine voids and microcracks.

  As described above, it was found that SLA concrete has higher water retention than ordinary concrete, and the compressive strength gradually increases due to the reaction of the chemical solution. In addition, it was confirmed that the concrete structure is highly durable, for example, microcracks caused by drying are reduced, and the accelerated neutralization depth is reduced due to a decrease in the air permeability coefficient.

Claims (6)

  A smart materialized artificial lightweight aggregate that contains water and a silicic acid-based chemical that reacts with the hydrated product of cement in the internal voids of a porous artificial aggregate calcined using coal ash and shale fine powder as the main raw materials.   The artificial material lightweight aggregate according to claim 1, wherein the drug is present in a state where at least a portion exposed on the surface is gelled. The porous artificial bone (material) for storing the drug has a moisture content of 30% or less, an absolute dry density of 2.5 g / cm ³ or less, and a maximum diameter of voids observed in the cross section of 2.0 mm or less. The artificial material lightweight lightweight aggregate according to claim 1 or 2.   After freeze-drying the porous artificial aggregate calcined with coal ash and shale fine powder as the main raw material, the agent is impregnated to the maximum impregnation rate in the internal void of the artificial aggregate under reduced pressure with an aqueous solvent, The manufacturing method of the smart material-ized artificial lightweight aggregate of Claim 1.   After freeze-drying the porous artificial aggregate calcined with coal ash and shale fine powder as the main raw material, the above-mentioned agent is impregnated to the maximum impregnation rate in the internal void of the artificial aggregate under reduced pressure with an aqueous solvent, The method for producing a smart materialized artificial lightweight aggregate according to claim 2, wherein the artificial aggregate after impregnation with the drug is brought into contact with a gelling agent.   The concrete kneaded material which used the smart material-ized artificial lightweight aggregate in any one of Claims 1-3 for 80 to 100 mass% of the total coarse aggregate.