JP2006282479A - Recycled aggregate-modifying agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recycled aggregate-modifying agent capable of improving the strength of a concrete hardened body. <P>SOLUTION: This recycled aggregate-modifying agent contains an alkali silicate solution satisfying the following requirements (1) and (2): (1) the silicon (Si) and lithium (Li) atoms are contained and sodium (Na) atoms may be contained in the molar ratio (Na/Li) of 0 to 0.3 and the molar ratio (SiO<SB>2</SB>/Li<SB>2</SB>O) of silicon and lithium in terms of oxides of 3.0 to 4.0; and (2) Q<SB>4</SB>/Q<SB>3</SB>of 0.1 to 0.35 and Q<SB>3</SB>/Q<SB>2</SB>of 2 to 10 in the ratios (Q<SB>4</SB>/Q<SB>3</SB>and Q<SB>3</SB>/Q<SB>2</SB>) of area Q<SB>n</SB>of the structural signal corresponding to Q<SB>n</SB>structure (n=2, 3 or 4) obtained by<SP>29</SP>Si-NMR measurement of a dried material prepared from the above alkali silicate solution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a regenerated aggregate modifier, a modified regenerated aggregate using the regenerated aggregate modifier, a method for producing the regenerated aggregate, and a cured body of a hydraulic composition using the regenerated aggregate. .

  From the viewpoint of environmental conservation, in order to reuse the hardened hydraulic composition typified by concrete that has become waste, we tried to crush and classify the hardened hydraulic composition to be used as recycled aggregate. It has been.

  The cement paste / mortar part adhering around the raw aggregate of the recycled aggregate is often deteriorated in quality and has a fragile part or a porous part. Therefore, the reclaimed aggregate generally has a large water absorption rate, and it is premised that the recycled aggregate is sufficiently pre-wetted before use. For this reason, compared with the case where such a regenerated aggregate uses virgin aggregate, it is a major problem that the strength when the cured hydraulic composition is reduced and the drying shrinkage is increased. As one method for solving this problem, treatment of recycled aggregate with a silica composition has been studied.

  Non-Patent Document 1 discloses a concrete using a reclaimed aggregate immersed in a colloidal silica solution.

  Patent Document 1 describes that the strength of a mortar using an aggregate immersed in a specific silica dispersion is improved (paragraph [0129]).

Concrete engineering, Vol.37, No.11, pp27-32, 1999 JP 2004-315343 A

  When the present inventors confirmed the strength of concrete using the colloidal silica disclosed in Non-Patent Document 1 and the recycled aggregate impregnated in the specific silica dispersion disclosed in Patent Document 1, the virgin bone was confirmed. It was found that there was much room for improvement in terms of strength compared to concrete using wood.

  Accordingly, the present invention provides a recycled aggregate modifier containing an alkali silicate solution for imparting good strength to a cured body of a hydraulic composition without reducing drying shrinkage resistance, and the recycled aggregate modified. It is an object of the present invention to provide a modified recycled aggregate treated with a material, a method for producing the recycled aggregate, and a cured body of a hydraulic composition using the recycled aggregate.

  The present invention provides a regenerated aggregate modifier containing an alkali silicate solution as a means for solving the problem, wherein the alkali silicate solution comprises the following requirements 1 and 2. .

Requirement 1: Containing silicon atom (Si) and lithium atom (Li), may contain sodium atom (Na), molar ratio of sodium atom to lithium atom (Na / Li) is 0 to 0.3, the molar ratio of the oxide equivalent silicon atom and a lithium atom _(SiO 2 / _Li 2 O) is 3.0 to 4.0. In the present invention, the “atom” includes ions.

Requirement 2: Signal area Q _n ratio (Q ₄ / Q ₃ and Q ₃ ) corresponding to the Q _n structure (n = 2, 3, 4) obtained by ²⁹ Si-NMR measurement of the dried product of the alkali silicate solution / Q ₂ ), Q ₄ / Q ₃ is 0.1 to 0.35, and Q ₃ / Q ₂ is 2 to 10.

  The modified recycled aggregate modified with the recycled aggregate modifier of the present invention can be used as an aggregate of a hydraulic composition, without reducing the drying shrinkage resistance of the hydraulic composition. The compressive strength of the cured body can be improved.

<Recycled aggregate modifier>
[Alkali silicate solution]
The regenerated aggregate modifier of the present invention is greatly characterized in that a specific alkali silicate solution is used. The alkali silicate solution refers to a solution containing water obtained by dissolving silicon oxide and alkali in the presence of water.

  The alkali silicate solution used in the present invention has a component containing silicon oxide in the form of a solution, so that compared with colloidal silica, which is a dispersion of conventional inorganic fine particles, the regenerated aggregate is excellent in impregnation. It is considered that the efficiency of the curing reaction by the silicon compound adhering to is improved.

  The alkali silicate solution used in the present invention has requirements 1 and 2. Hereinafter, each requirement will be described.

Requirement 1: Containing silicon atom (Si) and lithium atom (Li), may contain sodium atom (Na), molar ratio of sodium atom to lithium atom (Na / Li) is 0 to 0.3, the molar ratio of the oxide equivalent silicon atom and a lithium atom _(SiO 2 / _Li 2 O) is 3.0 to 4.0.

  The alkali silicate solution used in the present invention improves the water resistance of silicon oxide adhering to the surface of recycled aggregate impregnated in the alkali silicate solution by making lithium atoms essential, and at the time of concrete production It is considered that the stability of the effect of modifying the recycled aggregate is improved in contact with water.

  In the alkali silicate solution used in the present invention, it is preferable that sodium atoms are mixed from the viewpoint of suppressing the increase in viscosity of the alkali silicate solution and improving the impregnation property of the alkali silicate solution into the recycled aggregate. Further, considering that the effect of improving the concrete strength by lithium atoms is not impaired, the molar ratio of sodium atoms to lithium atoms (Na / Li) is 0 to 0.3, preferably 0.001 to 0.25, More preferably, it is 0.01-0.20.

In the alkali silicate solution used in the present invention, the molar ratio of silicon atom to lithium atom in terms of oxide (SiO ₂ / Li ₂ O) does not impair the concrete strength improvement effect by lithium atoms, and the alkali silicate solution is regenerated. From the viewpoint of ensuring the impregnation property to the aggregate, it is 3.0 to 4.0, preferably 3.1 to 3.9, and more preferably 3.2 to 3.8.

Requirement 2: Signal area Q _n ratio (Q ₄ / Q ₃ and Q ₃ ) corresponding to the Q _n structure (n = 2, 3, 4) obtained by ²⁹ Si-NMR measurement of the dried product of the alkali silicate solution / Q ₂ ), Q ₄ / Q ₃ is 0.1 to 0.35, and Q ₃ / Q ₂ is 2 to 10.

This indicates that the smaller the Q ₄ / Q ₃ and Q ₃ / Q ₂ are, the lower the viscosity of the alkali silicate solution is and the better the impregnation of the recycled aggregate.
Q ₄ / Q ₃ is 0.1 to 0.35 from the viewpoint of securing water resistance, preferably 0.15 to 0.30, and more preferably 0.20 to 0.30. Q < ₃ > / Q < ₂ > is 2-10 from a viewpoint of ensuring water resistance, and 5-8 are more preferable.

(Method of measuring the _{Q n)}
(1) The alkali silicate solution is left to dry in a hot air dryer at 30 ° C. for 72 hours.
(2) ²⁹ Si-NMR measurement is performed on the dried product.
(3) The area of each signal corresponding to the following chemical shift range (TMS standard) obtained by ²⁹ Si-NMR (however, when some of the signals overlap, each signal is represented by a Gaussian function and a Lorentz type. each area of the signal) when approximated by a linear sum of the function referred to as _{"Q n} structures (n = 2, 3, 4)."
Chemical shifts Structure -85-90 ppm Q ₂ structure -92~-100ppm Q ₃ structure -105~-115ppm Q ₄ structure
(4) the ratio of _{Q 4} Structure and _{Q 3} structure to the _Q 4 _/ Q 3, the ratio of _{Q 3} structure, _{Q 2} structure _Q 3 / _{Q 2.}

(Physical significance of Q _n )
The Q _n structure is considered to have the following physical significance. That, Q _n structures, bridging oxygen atoms of the oxygen atom of the SiO ₄ tetrahedral units is a structural unit by silicon and oxygen alkali silicate dried product of (oxygen atom bonded to two silicon atoms) It corresponds to the chemical structure corresponding to the number, and _n in the Qn structure corresponds to the number of bridging oxygen atoms and corresponds to the degree of bonding of SiO ₄ units.

When Q ₄ structure is relatively larger than Q ₃ structure, the number of oxygen atoms bridging the SiO ₄ units are many, because SiO ₄ units to form a network structure, is believed to improve the water resistance of the silicon oxide.

However, it is considered that the network structure becomes excessive with only the Q ₄ structure and the Q ₃ structure, the viscosity and hydrophilicity of the alkali silicate solution are impaired, and the impregnation property of the alkali silicate solution into the recycled aggregate cannot be ensured.

Therefore, by incorporating the Q ₂ structures considered weakly binding between network structure according to Q ₄ structures and Q ₃ formed by the bond of a linear or cyclic, water resistance of the alkali silicate solution, the viscosity and hydrophilicity harmony, It is thought that moderate impregnation is ensured in the alkali silicate solution. That is, in the present invention, when Q ₂ is relatively larger than Q ₃ , the water resistance is lowered, and when it is relatively small, the permeability is lowered. Therefore, Q ₄ / Q ₃ and Q ₃ / Q ₂ are appropriately adjusted. It is possible to ensure suitable water resistance, viscosity, and hydrophilicity by balancing with each other.

  The alkali silicate solution used in the present invention ensures the workability and water resistance suitable for impregnating the recycled aggregate, and from the viewpoint of not impairing the impregnation property due to excessive viscosity, the silicon in the alkali silicate solution Atoms, lithium atoms, and sodium atoms can be adjusted to a desired content by adjusting the amount of water.

  From this point of view, it is preferable that the content of silicon atom, lithium atom, and sodium atom in the alkali silicate solution used in the present invention further satisfies requirement 3.

Requirement 3: The total content of silicon atoms and lithium atoms in the alkali silicate solution is 1 wt% or more and 30 wt% or less in terms of oxide (SiO ₂ , Li ₂ O), and includes silicon atoms and lithium atoms The total content of alkali atoms (M) is 30% by weight or less in terms of oxide (SiO ₂ , M ₂ O).

  In Requirement 3, the content of silicon atoms and alkali atoms (M) is more preferably 28% by weight or less, more preferably 25% by weight or less in terms of oxide, and the content of silicon atoms and lithium atoms in terms of oxide. Is preferably 5% by weight or more, more preferably 10% by weight or more.

  From the viewpoint of ensuring impregnation properties, the viscosity of the alkali silicate solution used in the present invention preferably does not exceed 3000 mPa · s, more preferably does not exceed 1000 mPa · s, and further does not exceed 100 mPa · s. preferable.

[Method for producing alkali silicate solution]
As the method for producing the alkali silicate solution used in the present invention, (1) ion exchange method, (2) colloidal silica method, (3) hydrothermal treatment method and the like can be applied, and among these, ion exchange method is preferable. .

(Ion exchange method)
An alkali silicate solution not containing lithium atoms (for example, sodium silicate solution) is treated with a cation exchange resin or electrodialyzed to reduce or remove the amount of sodium atoms (sodium removal treatment). Thereafter, a predetermined amount of lithium salt is added so as to satisfy Requirement 1. Moreover, a concentration process can also be performed in density | concentration adjustment.

  The alkali silicate solution containing no lithium atom before the sodium removal treatment used in the present invention is not particularly limited, and may be a commercially available one or one produced by a known method.

  As a commercial item, a sodium silicate solution (JIS standard No. 1 water glass, No. 2 water glass, No. 3 water glass or No. 4 water glass) is mentioned.

  For example, the sodium silicate solution to be subjected to sodium removal treatment is stirred while adding the cation exchange resin to the sodium silicate solution, and the sodium silicate solution and the resin are brought into contact with each other. Then, after removing sodium-on from the sodium silicate solution, a predetermined amount of lithium is added. Other methods include packing a cation exchange resin in a cylindrical column and passing sodium silicate solution through the column to remove sodium, and further promoting contact with the resin by injecting pressurized air, etc. Manufactured by applying the above.

For example, when a sodium silicate solution is removed by treatment with a cation exchange resin, the amount ratio between the cation exchange resin and the sodium silicate solution to be treated depends on the composition of the sodium silicate solution to be treated. However, in general, the amount is preferably 50 to 400 parts by weight, more preferably 80 to 320 parts by weight with respect to 100 parts by weight of the cation exchange resin.
The contact time between the sodium silicate solution and the cation exchange resin is preferably about 1 to 60 minutes. The contact between the two can be terminated, for example, by filtering the sodium silicate solution containing the resin to remove the resin. The treatment is preferably performed so that the pH after the sodium removal treatment is 10 or less, preferably 5 or less, more preferably 3.2 or less.

  Electrodialysis treatment is performed by filling sodium silicate solution into an electrodialysis layer in which a pair of electrodes are inserted at both ends, in which negative and cation exchange membranes are alternately arranged, and applying a direct current to sodium in the sodium silicate solution. This refers to the process of removing ON. The said process can be performed, for example using a commercially available electrodialysis apparatus.

When sodium silicate solution is removed by electrodialysis, a part of the treated sodium silicate solution is sampled over time after the start of treatment, and the SiO ₂ / Na ₂ O ratio is obtained to obtain a desired value. At this point, the process may be terminated.

  The lithium salt is added while stirring the sodium removal treatment solution, and further aging is continued for 30 minutes to several days. The lithium salt is not particularly limited, but lithium hydroxide is preferable from the viewpoint of solubility and transparency of the silicic acid solution after dissolution.

  The concentration step can be performed under heating at room temperature or higher. However, from the viewpoint of preventing gelation of the silicic acid solution, it is desirable to perform vacuum concentration at a temperature of 60 ° C. or lower.

(Colloidal silica method)
In this method, colloidal silica, sodium salt, and lithium salt are mixed and aged so as to have a predetermined molar ratio. As the colloidal silica, those having various particle diameters can be used.

  Although it is cloudy at the beginning of mixing, a transparent liquid can be obtained by heating at room temperature to 100 ° C. for several hours to several days.

(Hydrothermal treatment method)
In this method, silica gel, silica sol, fumed silica, amorphous silica, crystalline silica or the like is used as a silica raw material and mixed with water, sodium salt, or lithium salt, followed by hydrothermal treatment.
(Other methods)
It can also be obtained by a method in which sodium hydroxide or the like is added to a commercially available lithium silicate solution and further aged for several hours to several days under heating at room temperature to 100 ° C.

  The regenerated aggregate modifier of the present invention may be composed only of an alkali silicate solution, and may further contain other additives as required. When the recycled aggregate modifier of the present invention is composed of an alkali silicate solution and other additives, the content of the alkaline silicate solution in the recycled aggregate modifier is 85% by weight or more. Is preferable, 90% by weight or more is more preferable, and 95% by weight or more is more preferable.

  As an additive, in order to further improve the impregnation property, a surfactant can be added as long as the water resistance is not impaired. The surfactant can be added in an effective amount in the recycled aggregate modifier, preferably 0.1 to 10% by weight, more preferably 0.5 to 2.5% by weight.

  Surfactants include anionic surfactants such as lauryl sulfate salts, alkylbenzene sulfonates, dialkylsulfosuccinates, polyoxyethylene alkyl ether sulfates, maleic anhydride copolymer salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl ethers. Nonionic surfactants such as oxyethylene alkylphenol ether, polyoxyethylene / styrenated phenol ether, polyoxyethylene tribenzylated orthophenylphenol ether, polyoxyethylene polyoxypropylene octylphenol ether, polyoxyethylene alkylamine, alkyltrimethylammonium Cationic surfactants such as chloride, alkylbenzyldimethylammonium chloride, alkylamine acetate and coconut Amphoteric surfactants such as betaine.

  In addition, from the viewpoint of using the regenerated aggregate modifier of the present invention in the regenerative aggregate modification treatment, it is preferable to add a compound having a chelating ability to metal ions as a stabilizer. The stabilizing agent can be added in an effective amount in the regenerated aggregate modifier, preferably 0.01 to 5% by weight, more preferably 0.5 to 1% by weight.

  Stabilizers include ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, propylenediaminetetraacetic acid, bis (2-hydroxyphenylacetic acid) ethylenediamine, and salts thereof, aliphatic oxycarboxylic acids, condensation A phosphate etc. are mentioned. Examples of the aliphatic oxycarboxylic acid include tartaric acid, citric acid, succinic acid, gluconic acid, dihydroxyethylglycine and the like. Examples of the condensed phosphate include salts of polyphosphoric acid such as pyrophosphoric acid, triphosphoric acid, trimetaphosphoric acid, and tetrametaphosphoric acid. Specifically, sodium pyrophosphate, sodium acid pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate , Sodium hexametaphosphate, sodium acid hexametaphosphate or potassium salts thereof.

<Modified recycled aggregate>
The modified recycled aggregate of the present invention is obtained by bringing the above-mentioned recycled aggregate modifier and the recycled aggregate into contact (preferably by impregnating the recycled aggregate modifier with the recycled aggregate). As the recycled aggregate, various aggregates such as coarse aggregate and fine aggregate can be used.

  The modified recycled aggregate obtained by contacting with the recycled aggregate modifier of the present invention is superior in the compressive strength of concrete compared to the modified recycled aggregate treated with a conventional silica-containing composition, Has low dry shrinkage equivalent to or better than virgin aggregate.

  Recycled aggregates have many fine pores that cause an increase in water absorption, generally have a long age of several decades, and are inactive with cement. Recycled aggregate obtained by contact has disappearance of many sub-millimeter-sized micropores and retains reactive alkali silicate inside the pores, so that the reaction activity with cement is increased. Presumed.

  Further, the regenerated aggregate modifier of the present invention is not only the outermost layer of the regenerated aggregate but also the surface inside the micropores, so that the water absorption is reduced and the effect of reducing drying shrinkage is exhibited. It is estimated to be.

<Method for producing modified recycled aggregate>
The method for producing a modified recycled aggregate according to the present invention includes the step (I) of bringing the recycled aggregate modifier of the present invention into contact with the recycled aggregate, and the regeneration brought into contact with the recycled aggregate modifier in the step (I). There are a step (II) for obtaining a wet regenerated aggregate by filtering the aggregate and a step (III) for drying the wet regenerated aggregate after the filtration in step (II).

In step (I), as a method of bringing the regenerated aggregate modifier of the present invention into contact with the regenerated aggregate,
(A) a method of spraying a regenerated aggregate modifier while transporting the regenerated aggregate on a belt conveyor;
(B) a method of immersing a recycled aggregate into a cage-shaped container in a recycled aggregate modifier filled in a larger container;
(C) A method of introducing a recycled aggregate and a recycled aggregate modifier into a drum of a ready-mixed concrete transport vehicle (raw concrete vehicle) can be mentioned, and from the viewpoint of good efficiency of the modification effect, (b) This method is preferred.

  When the method (b) is applied, the immersion time may be arbitrarily selected depending on the treatment amount and other conditions, and the immersion time may be several seconds to several days. From the viewpoint of preventing the gelation reaction of the regenerated aggregate modifier on the surface of the material, several minutes to 24 hours are preferable.

  Furthermore, when the method (b) is applied, the pressure impregnation method is more preferably used for the purpose of improving the impregnation action. The pressure impregnation method is a method in which recycled aggregate is put into a decompressed space, dried under reduced pressure for a certain period of time, and then the recycled aggregate modifier is sucked into it and then impregnated by releasing the pressure. It is.

  Next, in step (II), the regenerated aggregate that has been contacted (preferably impregnated) with the regenerated aggregate modifier in step (I) is filtered.

  As the filter medium, it is preferable to use a container in which a woven wire net is formed into a cage shape. As a woven wire mesh, it is economical to use a wire mesh that is screened using a mesh made by weaving wire materials (hard steel wire, stainless steel wire, etc.). An arch crimp, a flat top, and a ton cap can be preferably used. What is necessary is just to select the optimal material and shape in the minimum dimension of the recycled aggregate to be filtered, the filtration amount, or the entire modification processing system. In the case of recycled aggregate, the mesh opening may be 2.5 mm or less, but if it is 0.3 mm or less, fine particles generated by friction between aggregates and the like accumulate in the filter medium. The opening is desirably in the range of more than 0.3 to 2.5 mm.

  Next, in step (III), the residue after filtration in step (II) is dried. Drying can be carried out at 0 ° C. to 105 ° C. The drying time is preferably 1 day at room temperature and about 1 hour at 105 ° C.

  The weight ratio of the regenerated aggregate modifier in the modified regenerated aggregate after drying is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% from the viewpoint of stably expressing the modification effect. 5% by weight.

  Processes (II) and (III) ensure a reaction time that contributes to the modification of the cement component contained in the recycled aggregate modifier and the paste and mortar around the recycled aggregate, and the surface moisture is evaporated. Thus, the recycled aggregate modifier can be prevented from escaping when mixed as recycled concrete.

<Hardened body of hydraulic composition>
The cured body of the hydraulic composition of the present invention is a cured body of a hydraulic composition containing hydraulic powder (cement etc.), aggregate and water, and the modified regenerated bone of the present invention is used as the aggregate. It contains materials.

  As the aggregate, the modified regenerated aggregate of the present invention can be used as all or a part of either or both of the coarse aggregate and the fine aggregate. When the modified recycled aggregate of the present invention is used as a part of coarse aggregate and / or fine aggregate, the content of the modified recycled aggregate of the present invention is 10% by weight or more in the total aggregate, and further 30 It is preferably at least 50% by weight, more than 50% by weight, further 70% by weight or more, and more preferably 90% by weight or more. In addition, a well-known aggregate (coarse aggregate and fine aggregate) can be used for the remaining aggregate.

  Known aggregates include natural coarse aggregates such as river gravel, mountain gravel and sea gravel, natural fine aggregates such as river sand, mountain sand and sea sand, crushed stone, artificial coarse aggregate such as blast furnace slag coarse aggregate, Artificial fine aggregates such as crushed sand and blast furnace slag fine aggregates, and other artificial aggregates such as artificial lightweight aggregates and heavy aggregates can be used. It is preferable to use crushed stone and crushed sand that conform to JIS A5005, which has a particularly large regenerative reforming effect.

  When the modified regenerated aggregate of the present invention is used as a raw material for the cured body of the hydraulic composition of the present invention, it can be used as an aggregate by measuring and mixing in the same manner as a normal natural aggregate.

  When the modified regenerated aggregate of the present invention is used as a raw material for the cured body of the hydraulic composition of the present invention, the regenerated aggregate modifier of the present invention (containing water) is contained in the modified regenerated aggregate. Since it adheres, it is necessary to correct | amend the quantity of the water contained in a hydraulic composition in consideration of the quantity of the water contained in the reproduction | regeneration aggregate modifier of this invention.

(1) Production of recycled aggregate modifier (alkali silicate solution) Production Example 1
60 kg of water was added and mixed with 10 kg of No. 3 sodium silicate (manufactured by Nippon Chemical Industry Co., Ltd.). While stirring the mixed solution, 15 kg of ion exchange resin: Amberlite IR120B (H) (manufactured by Organo) was added, and stirring was continued for 30 minutes. After confirming that the pH of the supernatant solution had dropped to 3.2, the ion exchange resin was separated by filtration with a SUS mesh. After 1 kg of lithium hydroxide (monohydrate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the separated solution, stirring was continued at 25 ° C. for 3 hours until the whole solution became transparent. Then, this liquid was concentrated to 16% by weight before concentration in a vacuum concentrator with heating at 40 ° C.

Production Example 2
In the operation of Production Example 1, 12 kg of ion exchange resin was used. The pH of the supernatant was 4.87.

Production Example 3
In the operation of Production Example 1, 20 kg of ion exchange resin was used. The pH of the supernatant was 3.45.

Production Example 4
In the operation of Production Example 1, 25 kg of ion exchange resin was used. The pH of the supernatant was 2.92.

Production Example 5
In the operation of Production Example 1, 25 kg of ion exchange resin was used. The stirring time was 90 minutes. The pH of the supernatant was 2.88.

Production Example 6
In the operation of Production Example 1, 9 kg of ion exchange resin was used. The pH of the supernatant was 9.80. After adding 1.065 kg of lithium hydroxide (monohydrate) (manufactured by Wako Pure Chemical Industries, Ltd.) to the solution obtained by filtering and separating the ion exchange resin with a SUS mesh, stirring is performed at 25 ° C. for 3 hours until the whole liquid becomes transparent. Continued. Then, this liquid was concentrated to 16% by weight before concentration in a vacuum concentrator with heating at 40 ° C.

Production Example 7 (Pressure impregnation method)
The recycled aggregate in an air-dried state was put into a vacuum chamber [volume 10.3 L, (inner diameter 205 mm, depth 312 mm)], and then reduced to 6.7 × 10 ⁻² Pa with a rotary pump. During decompression, the regenerated aggregate modifier was injected into the vacuum chamber until the entire aggregate was lost, and after releasing to atmospheric pressure, it was left for 10 minutes. Thereafter, filtration and drying were performed.

Comparative production example 1
A commercially available colloidal silica solution (Nissan Chemical Industries Snowtex 20L, silica concentration 20%) was used as it was.

Comparative production example 2
A commercially available sodium silicate solution (JIS No. 3 standard water glass: manufactured by Nippon Chemical Industry Co., Ltd.) was used by diluting it twice with water (alkali silicate solid content 20%).

Comparative production example 3
A commercially available lithium silicate solution (lithium silicate 45: manufactured by Nippon Chemical Industry Co., Ltd.) was used as it was (alkaline silicate solid content 20%).

Comparative production example 4
In the operation of Production Example 1, 7 kg of ion exchange resin was used. The pH of the supernatant was 10.90. After 1.424 kg of lithium hydroxide (monohydrate) (manufactured by Wako Pure Chemical Industries) was added to the solution obtained by filtering and separating the ion exchange resin with a SUS mesh, the mixture was stirred at 25 ° C. for 3 hours until the whole solution became transparent. Continued. Then, this liquid was concentrated to 16% by weight before concentration in a vacuum concentrator with heating at 40 ° C.

(2) Measuring method [gravimetric analysis of silicon atom, lithium atom and sodium atom, molar ratio]
The analysis of silicon was performed by ICP analysis, and the analysis of alkali metal was performed by atomic absorption analysis. A measurement calibration curve for each element was prepared in advance, and the element concentration was quantified (% by weight) from the emission intensity (silicon) and the absorption intensity (lithium, sodium) of the measurement element. In preparing the calibration curve, a 1000 ppm standard solution manufactured by Kanto Chemical was diluted and used.
As an ICP measuring device, HORIBA, Ltd. JY238 ULTRACE was used. As the atomic absorption spectrometer, Varian Spectr AA220 was used. From the quantitative value (wt%) of each element (silicon, lithium, sodium), the molar ratio of each atom and the oxide wt% were converted.

[Calculation of content of silicon atom, lithium atom and sodium atom]
The production example 1 is illustrated. Other production examples can be calculated in the same manner. As a result of the above analysis, 8.27% by weight of silicon, 1.21% by weight of lithium, and 0.47% by weight of sodium were obtained. From this, the oxide weight% of each atom was converted by the following formula.
Oxide of each atom (% by weight) = Quantitative value of each atom (% by weight) × (molecular weight of oxide / atomic weight)
Finally, 21.0% was calculated as the sum of the oxide weight percentages of silicon, lithium, and sodium (SiO ₂ : 17.73%, Li ₂ O: 2.60%, Na ₂ O: 0.63%). .

〔viscosity〕
The viscosity was measured using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model number B8L). About 100 ml of the alkali silicate solution was put in a screw tube (Marume No. 8), and after the rotation of the rotor, the indicator value after 2 minutes was measured and used as a measured value. The measurement was performed at 20 ° C.

〔water resistant〕
5g of alkali silicate solution is put into a glass petri dish (flat petri dish, product number: 70, diameter 75mm) and dried at 50 ° C for one day in a dryer (ADVANTEC, model number: FC-410), thereby drying and curing. Got the body. The weight (g) of the cured body was measured (W ₁ ) using an electronic balance (manufactured by METLER, model number: AB204-S), and then immersed in 50 ml of ion-exchanged water for 12 hours. Thereafter, ion-exchanged water was removed with a spoid, and again dried for 1 day at 50 ° C. in a dryer (model number: FC-410, manufactured by ADVANTEC), and the weight of the cured product was measured (W ₂ ). Thereafter, the residual dissolution rate (%) [(W ₂ / W ₁ ) × 100] was calculated and regarded as water resistance.

<Modified recycled aggregate>
The regenerated aggregate is brought to a constant air-dry state in a constant temperature and humidity chamber (the weight at this time is W ₀ ), and then immersed in a regenerated aggregate modifier (alkaline silicate solution) shown in Table 2 It was dried in a constant humidity chamber for 24 hours or more to be in an air-dried state (the weight at this time is W ₁ ). In order to examine the influence on the concrete properties by the soaking state, the soaking time was set to 3 cases of 10 minutes, 60 minutes and 24 hours. Increase rate for _{W 0} of _{W 1 ((W 1 -W 0} ) / W 0) × 100 is examples ranged also of 1-2% in any of the comparative examples.

単位量は、ＪＩＳ Ａ０２０３−３５０６に定義される。 <Hardened concrete>
[material]
The materials used for the recycled aggregate concrete were as follows, and as a coarse aggregate, a commercial product of recycled coarse aggregate (obtained in Tokyo area), a modified recycled coarse aggregate, and a crushed stone for comparison were used.
Coarse aggregate (G): Recycled coarse aggregate Surface dry density 2.35 g / cm ³ , Water absorption 7.66%
Modified recycled coarse aggregate surface dry density 2.35g / cm ³ , water absorption 5.5%
Crushed stone (Ome hard sandstone crushed stone) Surface dry density 2.71 g / cm ³ , water absorption 0.66%
Cement (C): Normal Portland cement Density 3.16g / cm ³
Fine aggregate (S): Mountain sand Surface dry density 2.64g / cm ³ , Water absorption 1.51%
Admixture: AE water reducing agent, AE agent mixed water (W): Tap water [Combination]
In any case where the modified recycled aggregate and crushed stone were used, the unit water amount and the coarse aggregate absolute volume were made the same as shown in the table below in order to examine the effect on strength and drying shrinkage.

The unit amount is defined in JIS A0203-3506.

[Test method]
A strength test (based on JIS A 1108-1999) and a drying shrinkage test (based on JIS A 1129-3-2001) were performed on the manufactured concrete. The results are shown in FIGS.

表２に、材齢２８日における改質再生骨材使用の再生骨材コンクリートの圧縮強度を示し、図１に、材齢２８日における、未処理再生骨材コンクリートの圧縮強度に対する改質再生骨材使用の再生骨材コンクリートの圧縮強度比を示す。図１から明らかなとおり、改質再生骨材を使用したコンクリートは、圧縮強度比が増加する傾向を示した。

Table 2 shows the compressive strength of recycled aggregate concrete using modified recycled aggregate at the age of 28 days, and FIG. 1 shows the modified recycled bone relative to the compressive strength of untreated recycled aggregate concrete at the age of 28 days. This shows the compressive strength ratio of recycled aggregate concrete. As is clear from FIG. 1, the concrete using the modified recycled aggregate showed a tendency for the compressive strength ratio to increase.

  FIG. 2 shows the compression strength ratio of recycled aggregate concrete using modified recycled aggregate to concrete using crushed stone at the age of 28 days. As shown in FIG. 2, in the concrete using the modified recycled aggregate, a compressive strength ratio of 90% or more could be secured.

  Table 2 shows the measurement results of the drying shrinkage strain at the age of 28 days, and FIG. 3 shows the measurement results of the dry shrinkage strain of the concrete hardened body of the reference example, the concrete hardened body of the comparative example 5, and the hardened concrete body of Example 6. Indicates. As shown in FIG. 3, dry shrinkage is greater when using untreated recycled aggregates compared to those using crushed stones, but is improved when using modified recycled aggregates. It was possible to reduce more.

The figure which shows the compressive strength ratio with respect to un-processed recycled concrete. The figure which shows the compressive strength ratio with respect to crushed stone concrete. The figure which shows heat-drying shrinkage | contraction distortion.

Claims (6)

A regenerated aggregate modifier containing an alkali silicate solution, wherein the alkali silicate solution has the following requirements 1 and 2.
Requirement 1: Containing silicon atom (Si) and lithium atom (Li), may contain sodium atom (Na), molar ratio of sodium atom to lithium atom (Na / Li) is 0 to 0.3, the molar ratio of the oxide equivalent silicon atom and a lithium atom _(SiO 2 / _Li 2 O) is 3.0 to 4.0.
Requirement 2: Signal area Q _n ratio (Q ₄ / Q ₃ and Q ₃ ) corresponding to the Q _n structure (n = 2, 3, 4) obtained by ²⁹ Si-NMR measurement of the dried product of the alkali silicate solution / Q ₂ ), Q ₄ / Q ₃ is 0.1 to 0.35, and Q ₃ / Q ₂ is 2 to 10. The recycled aggregate modifier according to claim 1, wherein the alkali silicate solution further comprises the following requirement 3.
Requirement 3: The total content of silicon atoms and lithium atoms in the alkali silicate solution is 1 wt% or more and 30 wt% or less in terms of oxide (SiO ₂ , Li ₂ O), and includes silicon atoms and lithium atoms The total content of alkali atoms (M) is 30% by weight or less in terms of oxide (SiO ₂ , M ₂ O).   2. The alkali silicate solution is obtained by a method of adding a predetermined amount of lithium atoms after reducing the amount of sodium atoms by ion exchange treatment of an alkali silicate solution containing no lithium atoms. Alternatively, the recycled aggregate modifier according to 2.   A modified recycled aggregate obtainable by contacting the recycled aggregate modifier according to any one of claims 1 to 3 with the recycled aggregate.   The step (I) of bringing the recycled aggregate modifier and the recycled aggregate according to any one of claims 1 to 3 into contact, and filtering and moistening the recycled aggregate brought into contact with the recycled aggregate modifier in the step (I) A method for producing a modified recycled aggregate comprising the step (II) of obtaining a recycled aggregate and the step (III) of drying the wet recycled aggregate after filtration in the step (II). A cured product of a hydraulic composition containing hydraulic powder, aggregate and water, wherein the aggregate contains a modified recycled aggregate obtained by the production method according to claim 5. Cured body.

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