JP7650191B2 - A method for producing ceramic-mixed cement, a method for producing a hardenable water admixture, and a method for producing a hardened cement product. - Google Patents

Description

The present invention relates to ceramic-mixed cement, hardenable water admixtures, and hardened cement products.

Technologies for improving the compressive strength of concrete have been proposed in the past. For example, Patent Document 1 discloses a method for producing a high-strength hardened cement product in which the kneaded cement mixture is transferred to a vacuum device, where it is vibrated or stirred, and water or the like is supplied from a supply device connected to the vacuum device to prevent air from entering. Patent Document 2 discloses a method for producing a reinforced concrete structure that includes a process of mixing a liquid containing a water-soluble epoxy resin with cement or the like.

International Publication No. 2015/004723 JP 2012-106889 A

However, the manufacturing method of Patent Document 1 requires special manufacturing equipment and processes, making it difficult to put into practical use. In addition, in the manufacturing method of Patent Document 2, when epoxy resin is mixed as a concrete component, the resin material of the epoxy resin and the hardener must be mixed and adjusted, which is time-consuming and difficult to handle. Furthermore, in the manufacturing method of Patent Document 2, the mixture in which epoxy resin is mixed with cement, etc. becomes highly viscous, which impairs the fresh properties of the concrete. Impairing the fresh properties of concrete can lead to reduced workability and reduced homogeneity of the resulting concrete. Reduced homogeneity of concrete affects the compressive strength of the concrete.

The present invention aims to provide a ceramic-mixed cement, a hardening water mixture, and a hardened cement product that have improved compressive strength and practicality.

In order to solve the above problems, a ceramic mixed cement according to an embodiment of the present invention has the following configuration.
(1) A ceramic mixed cement containing porous ceramic particles having first pores on the nanometer order with a pore size of more than 10 nm and not more than 1000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm.
(2) The ceramic mixed cement according to (1) above, wherein the porous ceramic particles have a particle size of 1 mm or less as determined by sieve classification.
(3) The ceramic-mixed cement according to (1) or (2), wherein the content of the porous ceramic particles is 7% by mass to 60% by mass.

The curable aqueous admixture according to an embodiment of the present invention has the following composition.
(4) A hardenable aqueous admixture comprising the ceramic-mixed cement according to any one of (1) to (3) above, aggregate, and water.
(5) The hardenable water admixture according to (4) above, wherein the content of the ceramic mixed cement is 20% by mass to 60% by mass in terms of solid content ratio.

The hardened cement product according to an embodiment of the present invention has the following configuration.
(6) A hardened cement product obtained by hardening the hardenable water admixture described in (4) or (5) above.

The present invention provides a ceramic-mixed cement, a hardening water mixture, and a hardened cement product that have improved compressive strength and practicality.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

The ceramic mixed cement of this embodiment is a ceramic mixed cement containing porous ceramic particles having first pores on the nanometer order with a pore size of more than 10 nm and not more than 1000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm.

<Porous ceramic particles>
The porous ceramic particles (hereinafter sometimes simply referred to as ceramic particles or ceramics) have first pores on the nanometer order with a pore size of more than 10 nm and not more than 1000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm.

As the raw material for ceramics, a mixture of clay and at least one selected from the group consisting of organic sludge, diatomaceous earth, and a foaming agent is used. By mixing clay with one selected from the group consisting of organic sludge, diatomaceous earth, and a foaming agent and firing it, the ceramics can be made porous. In particular, it is preferable to include at least organic sludge, from the viewpoint that it is easy to efficiently form first pores on the nanometer order with a pore size of more than 10 nm and not more than 1000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm in the obtained ceramics.

Clay is a mineral material exhibiting clay-like properties that is generally used as a ceramic raw material, other than diatomaceous earth.
The clay may be any known clay that has been used in ceramics, and is composed of a mineral composition such as quartz, feldspar, or other clay-based materials, and the constituent minerals are preferably kaolinite as the main component, and include halloysite, montmorillonite, illite, bentonite, or pyrophyllite. Among them, frog-eye clay is an example. The clay may be blended alone or in a suitable combination of two or more types.

In the process of firing these minerals in the clay, components remaining as amorphous bodies, such as metakaolin remaining in the process of firing kaolinite to convert it to mullite, react with calcium hydroxide in the cement to form a strong crystalline structure that is insoluble in water. The crystalline structure present in the hardened cement product of this embodiment is thought to be one of the factors that improve the compressive strength of the hardened cement product.

Organic sludge is sludge containing organic matter as a main component. Any organic sludge can be used, and activated sludge derived from wastewater treatment in sewage or factories is preferred. Activated sludge is discharged from wastewater treatment equipment using the activated sludge method through coagulation and dehydration processes. By using organic sludge, the organic matter in the organic sludge is burned in the firing process, and pores on the nanometer order and micrometer order can be efficiently formed due to the path taken when the sludge is vaporized from the fired body. Furthermore, activated sludge derived from wastewater treatment, which was previously considered waste, can be reused as a raw material.
The water content of the organic sludge is, for example, preferably 5% by mass to 90% by mass, more preferably 60% by mass to 90% by mass, and even more preferably 65% by mass to 85% by mass, based on the total mass of the organic sludge. If it is within the above range, it is easy to mix it into the mixture.

When organic sludge is used, the content of organic sludge in the mixture can be determined taking into consideration the moldability of the mixture, and is, for example, preferably 0.1% to 30% by mass, more preferably 5% to 20% by mass, and even more preferably 5% to 15% by mass, relative to the total mass of the mixture. If the content of organic sludge in the mixture is within the above range, the mixture has appropriate fluidity and plasticity, and can be smoothly molded without clogging the molding device.

The mixing device used in the mixing step of the mixture is not particularly limited, and any known mixing device can be used.
Examples of the mixing device include a kneader, a mixer, and the like.

The mixture is formed into an appropriate shape, such as a columnar, plate, granular, or pellet shape, using known forming equipment such as a vacuum kneading machine, a flat plate press machine, or a flat plate extrusion machine, and then fired to obtain porous ceramics.

If necessary, the molded body may be dried before firing. The drying operation can be carried out using a known method. For example, the molded body may be dried naturally at room temperature (e.g., approximately 20°C to 30°C as a guideline) or may be dried by processing it in a hot air drying oven at 50°C to 220°C for a desired period of time.

The firing step is not particularly limited, and a known method can be used. For example, a method of firing at an arbitrary temperature using a continuous sintering furnace such as a roller hearth kiln or a batch sintering furnace such as a shuttle kiln can be mentioned. Among them, it is preferable to use a continuous sintering furnace for the firing operation from the viewpoint of productivity.
The firing temperature (maximum temperature) can be determined depending on the properties of the mixture, and is, for example, 850°C to 1200°C. If the firing temperature is equal to or higher than the lower limit, when organic sludge is used in the mixture to be fired, odorous components derived from the organic sludge are thermally decomposed and eliminated, and most of the organic matter in the organic sludge is volatilized and reduced in weight. If the firing temperature exceeds the upper limit, the entire structure of the ceramics is vitrified, and there is a risk of pore blockage.

The above process makes it possible to efficiently obtain a fired ceramic body having first pores on the nanometer order with a pore size of more than 10 nm and not more than 1000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm. The nanometer-order pores provide the ability to absorb moisture by capillary action, while the micrometer-order pores significantly improve the water retention rate of the ceramic particles, adsorbing and retaining excess moisture in the hardening water mixture within the ceramic particles while also exhibiting the effect of gradually releasing the retained water appropriately during the hardening stage, which is thought to be one of the factors that make the structure of the hardened cement product of this embodiment dense and improve the compressive strength.

The pore size can be measured by performing image processing according to the scale of image data obtained by scanning electron microscope observation. In this disclosure, the pore size of a particle is the longest diameter of the particle's pores measured using an electron microscope.

The pores formed in the porous ceramics may be independent of each other, or may be interconnected pores. It is preferable to measure the longest diameter of the pores of the particles in each independent pore.

The total porosity of the porous ceramic is preferably 35% to 85%. If the total porosity is less than 40%, the amount of excess water in the hardenable water mixture that the ceramic particles can hold may be too small. If the total porosity is more than 80%, the proportion of pores on the nanometer order may be reduced, and the effect of absorbing and gradually releasing excess water in the hardenable water mixture may be less likely to be exhibited. A more preferable total porosity is 45% to 75%.
Here, the total porosity means the ratio of all pores in the ceramic, which is calculated by the following formula:
Total porosity (%) = {1-(apparent density/true density)}×100

The porous ceramic obtained as described above is crushed to form ceramic particles. The crushing process is not particularly limited, and known methods can be used. For example, the porous ceramic obtained by firing can be crushed using a hammer mill, a biaxial rotary crusher, a jet mill, a ball mill, or an edge runner mill.

The particle size of the porous ceramic particles is preferably 1 mm or less as determined by sieve classification. By using porous ceramic particles with a particle size of 1 mm or less as determined by sieve classification, the particles penetrate into the cement and other aggregates to fill the gaps, reducing the amount of air in the hardened cement and improving the compressive strength, and when mixed with water, they weaken the dilatancy, improving workability, and at the same time making it difficult for the aggregate to separate.

Ceramic particles with a particle size of 1 mm or less as determined by sieving can be obtained by classifying the crushed ceramic particles as described above by sieving them through a sieve with a mesh size of 1 mm. It is also possible to sieve the particles, and then crush and sieve again any large particles with a particle size of 1 mm or more.

<Ceramics-mixed cement>
The cement used in this embodiment is not particularly limited, and any known cement can be used. For example, in addition to Portland cement as specified in JIS R5210, mixed cement as specified in JIS R5211 to R5213, ecocement as specified in JIS R5214, and mixtures of multiple components of these cements can be used.

The mixing ratio of the porous ceramic particles to the cement is preferably 7% to 60% by mass of the ceramic particles relative to the total mass. If the ratio of the ceramic particles is less than 7% by mass, the function of improving the compressive strength of the hardened cement product may not be fully realized. If the ratio of the ceramic particles exceeds 60% by mass, the bonding strength that the cement originally exerts may be reduced. A more preferable ratio of the porous ceramic particles is 15% to 45% by mass.

<Curing Water Mixture>
The hardenable water admixture of the present embodiment is a hardenable water admixture containing the ceramic-mixed cement, aggregate, and water.
In this embodiment, the aggregate does not include the above-mentioned ceramic-mixed cement.

The term "hardening water admixture" refers to a mixture of cement, aggregate, and water, which is generally called fresh concrete or ready mixed concrete. In this specification, the term "hardening water admixture" is not limited to concrete (fresh concrete, ready mixed concrete, etc.), but also includes admixtures for mortar that do not contain coarse aggregate.

The aggregate is not particularly limited, and known aggregates can be used. For example, fine aggregates include river sand, mountain sand, sea sand, crushed sand, silica sand, limestone aggregate, blast furnace slag fine aggregate, copper slag fine aggregate, electric furnace oxidized slag fine aggregate, mineral particles such as kaolinite and mica, and combinations of two or more of these. For example, coarse aggregates include gravel, crushed stone, limestone aggregate, blast furnace slag coarse aggregate, electric furnace oxidized slag coarse aggregate, crushed materials such as roof tiles and glass, and combinations of two or more of these. To obtain mortar, only the fine aggregates can be used, and to obtain concrete, the fine aggregates and coarse aggregates can be used in combination.

Additives such as water-reducing agents, defoaming agents, admixtures, resins, reinforcing fibers, and pigments may be mixed into the hardening water mixture without departing from the scope of the present invention.

The hardening water mixture is obtained by mixing the ceramic mixed cement, aggregate, water, and additives as necessary. There are no particular limitations on the mixing process, and known methods can be used. For example, mixing can be performed using a rotary mill or mixer. When mixing, first mix only the solids and stir (dry mix), then add water and mix. This disperses the solids evenly in the hardening water mixture, suppressing separation of the aggregate and variation in strength of the finished hardened cement.

The proportion of the ceramic mixed cement in the hardenable water mixture is preferably 20% to 60% by mass in terms of solid content ratio. The solid content ratio of the ceramic mixed cement refers to the mass ratio of the ceramic mixed cement to the components other than water in the hardenable water mixture. If the proportion of the ceramic mixed cement is less than 20% by mass, the cement hardened product may not be bonded sufficiently, resulting in a decrease in strength, and if it exceeds 60% by mass, the dilatancy of the flow behavior of the hardenable hydrate may be strongly expressed, resulting in a decrease in workability. A more preferable proportion of the ceramic mixed cement is 25% to 50% by mass.

The proportion of water in the hardening water mixture can be adjusted appropriately, taking into consideration the type and amount of water-reducing material used in combination. For example, the preferred slump value of the hardening water mixture for concrete is 15 cm to 23 cm.

<Hardened cement>
The hardened cement product of the present embodiment is obtained by curing and hardening the hardenable water mixture.

The curing process for the hardening water mixture is not particularly limited, and known methods can be used. For example, after pouring, the mixture may be left at room temperature, degassed and dehydrated by vacuuming or pressurization, or the mixture may be covered with a curing sheet containing water to promote the hydration reaction, exposed to steam, immersed in water, or heated in addition to the above.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these, and additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the spirit of the present invention.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

(Raw materials used for porous ceramic particles)
The raw materials for the porous ceramics used in the examples are as follows:

<Clay>
The clay used was frog-eye clay (produced in Gifu Prefecture).
<Organic sludge>
The organic sludge used was activated sludge discharged through coagulation and dewatering processes from a wastewater treatment facility using the activated sludge method at a dyeing factory (Komatsu Matere Co., Ltd.) The organic matter content (based on solid content) of this activated sludge was 83% by mass, the water content was 85% by mass, and the average particle size was 2.6 μm.
<Diatomaceous earth>
The diatomaceous earth used was crushed (particle size: 0.1 mm to 1.2 mm) that had been used as roofing tiles for houses and then discarded.
<Foaming Agent>
The foaming agent used was cast iron slag, which was particulate _ductile cast iron slag (sieved to a diameter of 10 mm or less) containing _SiO2 , _Al2O3 , _CaO , _Fe2O3 , FeO, MgO, MnO, _K2O and _Na2O as main components.

(Production of Porous Ceramic Particles)
The raw materials were mixed in the following proportions to obtain a plastic mixture.
Clay: 22.5% by mass,
Organic sludge: 10.0% by mass,
Diatomaceous earth: 22.5% by weight,
Foaming agent: 45.0% by mass
Next, the mixture obtained was extruded into a cylindrical shape having a diameter of 1.5 cm using a vacuum clay kneading molding machine, and the extruded cylindrical shape was cut into a length of 3 cm to obtain a cylindrical molded body.

The obtained molded body was sintered in a continuous sintering furnace at a sintering temperature of 990° C. and a residence time at the sintering temperature of 10 minutes. The obtained sintered ceramic body was cut into a cube with a side length of 20 mm, and the apparent density was measured by measuring the mass. The true density was measured with a density measuring device (Macpycno (registered trademark), manufactured by Mountec Co., Ltd.), and the total porosity was measured by the following formula. The total porosity of the obtained sintered ceramic body was 64%.
Total porosity (%) = {1-(apparent density/true density)}×100

After firing, the resulting porous ceramic lumps were crushed in a hammer mill until the maximum particle size was 10 mm or less. Next, a sieve was used, and those that passed through a sieve with 1 mm openings were used as porous ceramic particles.

The nanometer-order pores and micrometer-order pores in the obtained porous ceramic particles were observed and confirmed at 100 to 10,000 times magnification using a scanning electron microscope (SEMEDX Type H, manufactured by Hitachi High-Tech Corporation). Numerous pores were observed in the obtained particles, including first pores on the nanometer order with a pore size of more than 10 nm and not more than 1,000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm, confirming that the particles were porous. The pore size was determined by measuring the long diameter of the observed pores.

(Production of ceramic blended cement)
The obtained porous ceramic particles and normal Portland cement (manufactured by Ube Mitsubishi Cement Co., Ltd.) were mixed in a predetermined amount and stirred in a mixer to produce a ceramic-mixed cement.

(Production of hardenable water mixture)
The obtained ceramic mixed cement was mixed with a predetermined amount of silica sand No. 5 (manufactured by Toyo Materan Co., Ltd.) as fine aggregate, and dry-mixed in a mixer. A predetermined amount of water was then added and stirred to produce a hardening water mixture.

(Production of hardened cement)
The obtained hardening hydrate was cast into a formwork and cured in air at room temperature for 24 hours, then removed from the formwork, immersed in water, and cured in water at room temperature for 27 days to obtain a hardened cement product.

(Compression test)
The obtained hardened cement material having an age of 28 days was subjected to a compressive strength test in accordance with JIS A 1108 "Test method for compressive strength of concrete".

(Examples 1 to 6, Comparative Examples 1 to 2)
The blending amounts of the ceramic mixed cement obtained from the porous ceramic particles and ordinary Portland cement, the blending amounts of the hardening water admixture obtained from the ceramic mixed cement, fine aggregate and water, and the results of the compression test of the hardened cement product obtained by hardening the hardening water admixture are shown in Table 1.

As can be seen from Table 1, the compressive strength of the hardened cement products of Examples 1 to 6, in which the present invention was applied, was improved compared to Comparative Examples 1 and 2, in which no ceramics were mixed into the cement.

Examples 1 to 6, which apply the present invention, could be produced without the need for special equipment or effort, improving their practicality.

Claims (6)

A step of obtaining porous ceramics by firing a mixture containing clay and organic sludge at a maximum temperature of 850°C to 1200°C, and crushing the obtained porous ceramics to obtain porous ceramic particles having first pores on the nanometer order with a pore size of more than 10 nm and not more than 1000 nm, and second pores on the micrometer order with a pore size of more than 1 μm and not more than 70 μm ;
mixing the porous ceramic particles with cement;
A method for producing a ceramic-mixed cement comprising the steps of : The method for producing a ceramic mixed cement according to claim 1, further comprising a step of reducing the particle size of the porous ceramic particles to 1 mm or less by sieve classification. The method for producing a ceramic mixed cement according to claim 1 or 2, wherein the content of the porous ceramic particles is 7% by mass to 60% by mass based on the total mass of the ceramic mixed cement. A method for producing a hardenable aqueous admixture, comprising: obtaining a ceramic mixed cement by the method for producing a ceramic mixed cement according to any one of claims 1 to 3; and mixing the obtained ceramic mixed cement, aggregate, and water to obtain a hardenable aqueous admixture. The method for producing the hardenable water admixture according to claim 4, wherein the content of the ceramic mixed cement is 20% by mass to 60% by mass in terms of solid content ratio relative to the hardenable water admixture. A method for producing a hardened cement product, comprising the steps of obtaining a settable water admixture by the method for producing a settable water admixture according to claim 4 or 5, and then hardening the settable water admixture.