JP2001180993A - Method of preventing neutralization of concrete with weatherproof and cement composition therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preventing neutralization of concrete with weatherproof and a cement composition for preventing neutralization using artificial zeolite obtained by utilizing waste materials from industry, nature or household as valuable resources. SOLUTION: This method comprises the following steps of reacting an inorganic material comprising one or two kinds of silica and alumina by heating or compressing under alkaline condition, converting the obtained material having cation exchange function into aluminum substitution type, and blending it with cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the use of incinerated ash of general garbage, clinker ash produced as industrial waste, incinerated ash of industrial waste such as incinerated ash of activated sludge, volcanic ash, etc. By synthesizing artificial zeolite and blending it into cement or concrete as an aluminum-substituted type, it stabilizes the alkali cations in the concrete structure, and, together with the generated salt, closes the voids in the concrete structure, and contaminates wastewater containing acid. The present invention relates to a method for preventing carbonation of concrete, which prevents deterioration by eliminating the influence of acid rain.

[0002]

2. Description of the Related Art At present, collapse of concrete structures frequently occurs in various places. Concrete is made by mixing natural rock aggregate, cement and water,
Originally, the construct was usable for about 60 to 70 years. However, in recent years, the deterioration rate of concrete over time has increased, and the durability of the structure has been lost.

Until now, in order not to lose the durability of the concrete structure, a method of limiting the alkali concentration of cement or using an aggregate after washing with water has been adopted. The collapse of the concrete structure has been prevented by dissolving the contained aggregate and preventing the alkali-aggregate reaction that degrades the concrete structure. In addition, regarding the efflorescence phenomenon in which the concrete surface becomes white and the material deteriorates, an inorganic compound obtained by treating silica and alumina with an alkali is mixed into the concrete, and the sodium content in the concrete moves toward the surface layer. Thus, a method of preventing a layer of sodium carbonate from being formed by a reaction with carbon dioxide gas on the surface layer of concrete to prevent the efflorescence phenomenon in which the surface of the concrete deteriorates white has been considered.

[0004]

However, the conventional method has been conceived for the purpose of avoiding the alkali-aggregate reaction and the efflorescence phenomenon, and is a factor in the occurrence of the above-mentioned reaction and phenomenon. It was not intended to prevent carbonation of concrete. Concrete neutralization is a phenomenon in which concrete containing alkali reacts with acids such as nitric acid, sulfuric acid, and carbon dioxide present in the atmosphere, rainwater, sewage, etc., causing the alkalinity in the concrete to be lost and degraded. It is. This deterioration rate changes depending on the degree of penetration of acid into concrete. For this reason, porous concrete containing more water relative to the amount of cement tends to be neutralized, and when the neutralization reaches close to the reinforcing bar, the passive film is destroyed and corrosion of the reinforcing bar starts.

Further, when sea sand is used in concrete, it is known that the salt content in the concrete is concentrated by the neutralization caused by the acid present in the air or rainwater. ing. In this case, the salt attached to the sea sand is dissociated in the concrete to form chloride ions, but most of the salt reacts with calcium aluminate in the cement to cause Friedel's salt (3CaO.Al ₂
A crystal called O ₃ .CaCl ₂ .10H ₂ O) is formed. Therefore, in a normal case, chloride used for the above-mentioned crystal formation corrodes the reinforcing steel.

[0006] However, the acid penetrates into the inside of the concrete through the capillary space with the passage of time, and decomposes the hardened cement structure that solidifies the concrete. Friedel's salt is decomposed by this neutralization, and the immobilized salt becomes chloride ions again. As a result, the chloride ion concentration in the neutralized portion increases, and the chloride ions move into the concrete structure due to the concentration diffusion phenomenon. For this reason, chloride concentration occurs at the forefront where carbonation occurs. This means that even if the salt content in concrete is average, when carbonation reaches near the reinforcing bar, the reinforcing bar corrodes violently.
Thus, it is a big problem that concrete used everywhere in daily life collapses in a short time,
There was a need for a way to resolve the situation.

[0007]

According to the first aspect of the present invention, an inorganic material containing one or two of a silicate component and an aluminum component is added to one or two of a silica-rich material and an aluminum-rich material. The seeded substance and the aqueous alkali solution are reacted by heating or pressurizing. Next, the resulting artificial zeolite, which has a cation exchange ability, is immersed in an aluminum chloride aqueous solution, and the treated product is mixed with cement or ready-mixed concrete. And, together with the resulting salt, plug the voids in the concrete structure. According to the second aspect of the present invention, a substance having an aluminum-substituted cation exchange ability is added to the cement. According to a third aspect of the present invention, the concentration of the aqueous alkali solution at the time of the reaction is 0.5 to 4.5N. In the invention according to claim 5, the heating during the reaction is performed at 80 to 230 ° C. According to the sixth aspect of the present invention, the pressurization reaction is carried out in the autoclave at a saturated vapor pressure or lower than the saturated vapor pressure. According to the invention of claim 7, ultrasonic vibration is added to the autoclave at the time of the pressurized reaction.

[0008]

Embodiments of the present invention will be described below. The present invention relates to a method for preventing carbonation of a concrete structure, in which one or two of a silicate-enriched material and an aluminum-enriched material are added to an inorganic material containing one or two of a silicate component and an aluminum component. By reacting the mixture with an aqueous alkali solution by heating or pressurizing,
A first step of producing an artificial zeolite which is a cation exchange material, a second step of immersing the obtained artificial zeolite in an aqueous solution of aluminum chloride to form an aluminum-substituted artificial zeolite, and converting the aluminum-substituted artificial zeolite into cement After the addition, the third step involves mixing with water and forming a stable salt with the released aluminate ions and the components in the cement to produce a concrete structure.

In the first step of the present invention, the inorganic material containing a silicate component described above includes industrial waste containing silicon dioxide such as waste glass, waste ceramics, cement waste, waste refractory, clay and the like. Refers to volcanic eruptions.

The inorganic material containing an aluminum component described in the first step of the present invention refers to industrial waste containing aluminum such as waste aluminum foil, electric wire waste, waste cans, etc., and garbage separated from households. Say.

The inorganic material containing a silicate component and an aluminum component described in the first step of the present invention includes coal ash, coal ash containing a high content of unburned carbon, paper sludge incineration ash, municipal waste incineration ash, It refers to industrial waste, household waste, natural waste, etc. containing an aluminum component and a silicate component such as activated sludge incineration ash and volcanic eruption products.

The silicate-enriching material described in the first step of the present invention refers to a substance containing a high content of SiO ₂ as a component. Examples thereof include sodium silicate, silicate glass, soda-lime glass, potash glass, and barium. Examples thereof include silicate glass such as glass.

The aluminum-enriched material described in the first step of the present invention refers to a substance containing a high content of aluminum as a component, such as aluminum dross, aluminum chloride, etc., which are produced as waste in the process of dissolving aluminum. Can be exemplified.

The silicate ratio described in the first step of the present invention is a molecular ratio between silicon dioxide and alumina, which affects the type of artificial zeolite to be produced when producing artificial zeolite. is there. That is, when the slag ratio is 1.
When the ratio is 5 or less, the generated artificial zeolite has a large amount of hydroxysodalite, and when the sulphate ratio is 2.0 to 2.5, a large amount of philipsite is generated. Since the service life of the concrete structure is required to be long, the artificial zeolite to be mixed is required to have a large cation exchange capacity. Therefore, in the present application, the ion exchange capacity of the artificial zeolite to be generated is set to be 300 to 420 meq / 100 g, and the silicate ratio is set to about 4 in order to avoid the fluctuation of the silicate ratio of the cement.

The alkaline aqueous solution described in the first step of the present invention refers to an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide. In the embodiment of the present invention, the alkali concentration is 2N. The concentration is 0.
It is possible to produce artificial zeolite at 5 to 4.5N.

In the first stage of the present invention, if the heating conditions during the reaction are 80 ° C. or more, there is no problem in carrying out the present invention, but in order to shorten the reaction time, a pressure-resistant container is used. If the mixture is heated to 80 to 230 ° C. or pressurized using a saturated vapor pressure, zeolite formation is rapidly performed. In addition, when a zeolite reaction is performed using a pressure vessel, the reaction is promoted by applying ultrasonic vibration to the pressure vessel, and zeolite progresses to the inside of the particles, so the present invention employs this method. ing. Equipment used: 1L autoclave with stirring (manufactured by Toyo Koatsu Co., Ltd.) Ultrasonic oscillator (Model US-600T manufactured by Nippon Seiki Co., Ltd.)

The aluminum-substituted artificial zeolite described in the second step of the present invention refers to an artificial zeolite, which is a substance having a cation exchange ability formed in the first step, is immersed in an aluminum chloride solution, And then air-dried. The conditions for immersing the artificial zeolite in the aluminum chloride solution were such that the concentration of the aluminum chloride aqueous solution was 1 N, the liquid temperature was 90 ° C., and the immersion time was 3 hours.

In the third stage, the aluminum-substituted artificial zeolite mixed in the ready-mixed concrete ion-exchanges alkali cations in the ready-mixed concrete, and the leached aluminum ions become aluminate under high pH conditions, Reacts with calcium hydroxide generated by the hydration reaction during concrete hardening to produce calcium aluminate. At this time, if sulfate ions are present,
(3CaO.Al ₂ O ₃ .3CaSO ₄ .3H ₂ O) to deactivate the water-soluble alkali sulfate and, if the concrete contains chloride ions, Friedel salt
(3CaO.Al ₂ O ₃ .CaCl ₂ .10H ₂ O) is generated and the chloride is stabilized. When both chloride ions and sulfate ions are present, both Friedel's salt and ettrine guide precipitate. The ettrine guide, Friedel's salt, has mechanical strength and expands when forming the salt, filling the voids in the hardening concrete. The aluminum-type artificial zeolite has a particle size of 5 to 100 μm, and this substance also has an effect of filling the voids in concrete, and can be used as a substitute for silica fume. As a result, after hardening of the concrete, the intrusion of rainwater or sewage containing acid from the outside is prevented, and the neutralization of the concrete can be prevented.

Further, the third step is to prevent the neutralization of the concrete structure by mixing the artificial zeolite substituted with aluminum with cement and aggregate. Concrete materials include cement, aggregate, water, and admixture materials. Cement is a general term for a binder, and generally refers to Portland cement. In the present invention,
Although ordinary Portland cement was used as cement,
In practicing the present invention, the present invention is not limited to this embodiment. The neutralization-preventing cement having weather resistance according to the present invention belongs to hydraulic cements, and hardens continuously in water. Table 1 shows the types of Portland cement and the chemical composition (%).

[0020]

[Table 1] As shown in Table 1, the type of ordinary Portland cement has an alum ratio (SiO ₂ / Al ₂ O ₃ ) of about 4,
Contains SO ₃ . In practicing the present invention, SO ₃ is a strong insoluble salt, ettrine guide (3CaO 3).
It is necessary for producing Al ₂ O ₃ .3CaSO ₄ .3H ₂ O).

[0021] Aggregate is an inert granular material that is hardened together with cement and water to make mortar or concrete, and is classified into two types: ordinary aggregate and lightweight aggregate. Fine aggregate having a particle size of 5 mm or less having a particle size of 85% or more was used, and the content with respect to the cement was 45% by weight. It is also possible to use the artificial zeolite as an aggregate by changing the particle size of the aluminum-substituted artificial zeolite.

As the water to be added to the cement, use is made of clean fresh water free of salt or foreign matter that causes a decrease in the strength of the cement or corrodes the reinforcing steel. did.

Next, a concrete block was prepared as a concrete structure, and a comparative study on neutralization was performed. The mixing ratio of cement, aggregate, water and aluminum-substituted artificial zeolite at that time was set as follows. First, the mixing amount of the aluminum-substituted artificial zeolite was adjusted to 0.5, 1, 1 with respect to 100 parts by weight of the cement to be mixed.
0, 15, 20, 50, and 100 parts by weight. Next, the above-mentioned aluminum-substituted artificial zeolite and aggregate were mixed with cement, and water was added and kneaded to obtain ready-mixed concrete. Fine aggregate was used as the aggregate at this time.
The mixing ratio of fine aggregate and water was 45 parts by weight of fine aggregate and 50 parts by weight of water with respect to 100 parts by weight of cement. Next, the ready-mixed concrete to which the above-mentioned aluminum-substituted artificial zeolite was added was put in a mold to form a rectangular parallelepiped block having a side of 10 cm.

[0024]

Example 1 An ultrasonic transmitter was installed in a 1-liter autoclave with a stirrer, and in this pressure-resistant reaction vessel, volcanic glass from Kagoshima with an aluminium ratio of about 3.2 was ground in an automatic mortar.
After putting 0 g and 200 ml of a 2N aqueous sodium hydroxide solution and closing the lid, the mixture was heated until the internal temperature reached 90 ° C. by the saturated vapor pressure while oscillating 25 kHz ultrasonic waves at 600 W. After keeping this state for 0.5 hour,
The vapor was evacuated to atmospheric pressure and the internal reactive products were removed. The reactive product was air-dried and subjected to X-ray diffraction. As a result, philipsite was formed, and its ion exchange capacity was 420 meq / 100 g.

[0025]

Example 2 Example 1 was 6 g of waste aluminum can flakes and 20 g of glass powder (manufactured by West Japan Environmental Development Association).
Put in the pressure vessel used in step 2, add 200 ml of 2N sodium hydroxide aqueous solution and close the lid.
Heating was carried out with saturated steam until the internal temperature reached 90 ° C. while generating ultrasonic oscillation at Hz. 0.5
After keeping the time, the steam was evacuated and returned to atmospheric pressure, and the reactive products inside were removed. The reaction product was air-dried and subjected to X-ray diffraction. As a result, a philipsite was formed as in Example 1, and its ion exchange capacity was 420 meq / l.
00 g.

[0026]

Example 3 Waste glass was crushed with an automatic mortar, and 20 g thereof was used.
And 6 g of aluminum dross (obtained from Japan Light Metal Association) in the pressure vessel used in Example 1, 200 ml of 2N aqueous sodium hydroxide solution was added, and the lid was closed.
Then, the mixture was heated until the internal temperature reached 230 ° C. by the saturated vapor pressure while performing ultrasonic oscillation at 25 kHz. After maintaining this state for 10 minutes, the steam was evacuated and returned to atmospheric pressure, and the internal reactive products were taken out. The reactive product was air-dried and subjected to X-ray diffraction. As a result, as in Example 1, philipsite was formed, and its ion exchange capacity was 420
meq / 100 g. .

Next, each of the artificial zeolites obtained in Examples 1 to 3 was immersed in an aluminum chloride solution to obtain an aluminum-substituted type. The conditions for immersing the artificial zeolite in the aluminum chloride solution were such that the concentration of the aluminum chloride aqueous solution was 1 N, the liquid temperature was 90 ° C., and the immersion time was 3 hours.

Next, each of the aluminum-substituted artificial zeolites was air-dried, mixed with the aggregate together with the cement, kneaded by adding water, and a concrete block was prepared. At this time, the mixing ratio of the aluminum-substituted artificial zeolite to the cement and the aggregate was as follows. First, the mixing amount of the aluminum-substituted artificial zeolite was adjusted to 0, 5, 10, 2 with respect to 100 parts by weight of the cement to be mixed.
0, 50, and 100 parts by weight.

As the aggregate, fine aggregate is used. The mixing ratio of the fine aggregate and water to cement is 45 parts by weight of fine aggregate and 50 parts by weight of water with respect to 100 parts by weight of cement. Then, the ready-mixed concrete to which the aluminum-substituted artificial zeolite is added and the cement to which the aluminum-substituted artificial zeolite is not added are put into a mold, and one side is 10 c.
A rectangular parallelepiped block consisting of m was created.

The concrete block produced as described above was immersed in a dilute sulfuric acid aqueous solution having a pH of 5.6, which was regarded as acid rain, for 24 hours, and the effect on the concrete was observed.
As a result, regarding the concrete block containing 5% or more of the aluminum-substituted artificial zeolite, no concrete deterioration was observed in appearance. Next, as a result of applying phenolphthalein to the block cross section of the above-mentioned zeolite having a content of 0, 5, 10, 50, 100 with respect to 100 weight of the cement, those having an artificial zeolite content of 0 were partially No color development was observed on the other concrete blocks, but color development was observed on all other concrete blocks. Concrete blocks containing aluminum-substituted artificial zeolite were acid-resistant, and aluminum-substituted artificial zeolite was converted to concrete by 5% or more. It was found that the effect of preventing carbonation can be brought out to concrete structures by mixing.

[0031]

According to the present invention, by adding an aluminum-substituted artificial zeolite to cement, aluminate is generated in the hardening concrete, and the aluminate present in the concrete is insoluble in the presence of chloride ions and sulfate ions. To form a solid salt, and, together with the aluminum-substituted artificial zeolite, close the voids in the hardening concrete. The insoluble salt is Friedel's salt and ettrine guide, and the salt has an expandability, and thus has an effect of reducing voids after concrete is hardened. As a result, it becomes difficult for rainwater or sewage containing acid to penetrate into the concrete structure, and neutralization is prevented. In addition, the present invention is to effectively utilize substances that are difficult to treat, such as industrial waste, household garbage, and natural exudates.
It has a beneficial effect.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 111: 22 C04B 111: 22

Claims (7)

[Claims] 1. An inorganic material containing one or two of a silicic acid component and an aluminum component, one or two of a silicic acid-enriched material or an aluminum-enriched material, and a mixture having an adjusted silicate ratio and an aqueous alkali solution. The product obtained by immersing the obtained cation-exchange product in an aqueous solution of aluminum chloride and mixing the resulting product with the cement, and immersing the cation-exchange product in an aqueous solution of aluminum chloride A method for stabilizing an alkali cation in a concrete structure and closing a void in the concrete structure together with a generated salt. 2. A neutralization-preventing cement composition having weather resistance, wherein an aluminum-substituted cation-exchange substance is blended into cement. 3. The method for preventing carbonation of concrete according to claim 1, wherein the sulphide ratio is adjusted according to required physical properties. 4. An alkaline aqueous solution having a concentration of 0.5 during the reaction.
The method for preventing neutralization of concrete according to claim 1, wherein the pressure is from 4.5 to 4.5 N. 5. The method according to claim 1, wherein the heating during the reaction is carried out at 80 to 230 ° C. 6. The method for preventing carbonation of concrete according to claim 1, wherein the pressurization reaction is carried out in an autoclave at a saturated vapor pressure or lower than the saturated vapor pressure. 7. The method according to claim 6, wherein ultrasonic vibration is applied to the autoclave during the pressurization reaction.