JP7612745B2 - Mortar composition and method for producing same - Google Patents

Description

This disclosure relates to a mortar composition and a method for producing the same.

As an effort to reduce _CO2 emissions, attention has been focused on a technology that chemically produces light calcium carbonate by dissolving _CO2 in a liquid phase and reacting it with calcium. Light calcium carbonate fixes _CO2 in the form of stable calcium carbonate, and therefore directly contributes to reducing _CO2 emissions.

When immobilizing a huge amount of _CO2 as calcium carbonate, it is possible to use waste and by-products that contain a lot of calcium and are discharged in large quantities, such as waste concrete and steelmaking slag, as a calcium source.
After calcium is extracted from the waste and by-products, a large amount of extraction residue is left behind. Generally, such extraction residue is often disposed of by landfill. However, if the extraction residue can be effectively utilized, it will contribute to extending the life of final disposal sites and reducing the environmental burden.

One possible use for the extracted residue is to use the larger particle size as a partial replacement for aggregate in concrete or mortar. This will contribute to the effective use of waste and by-products.

For example, Non-Patent Document 1 proposes producing concrete by replacing part of the aggregate with crushed roofing tiles.

Manufacturing and evaluation test of concrete using crushed roof tile aggregate, Abe Kohei et al., Shimane Prefectural Industrial Technology Center Research Report, No. 47, 2011

When mortar is produced using low-reactivity waste and by-products as aggregate, there is concern that its strength development will decrease, as in the case of the concrete described in Non-Patent Document 1.

Therefore, an object of the present disclosure is to provide a mortar composition that contributes to reducing _CO2 emissions while reducing the environmental impact by effectively utilizing waste and by-products, and further has the same strength development as mortars using current cements, and is particularly excellent in early strength.

One aspect of the present disclosure is a mortar composition comprising cement, fine aggregate, and water,
The fine aggregate contains calcium-containing waste in an amount of 1.0 mass % or more and 15.0 mass % or less.
Contains less than % by weight
The calcium-containing waste material is
The insoluble residue measured in accordance with JIS R 5202:2010 is 20.0% by mass or more and 90.0% by mass or less,
Contains 5.0% by mass or more of calcium carbonate, and
The present invention aims to provide a mortar composition having a residual CaO content of 18.0 mass % or less, after subtracting the amount of CaO derived from calcium carbonate.

Another aspect of the present disclosure is a method for producing a mortar composition comprising cement, fine aggregate, and water, comprising:
A step of obtaining fine aggregate by mixing a fine aggregate material with the calcium-containing waste so that the calcium-containing waste is contained in the fine aggregate in an amount of 1.0 mass% or more and 15.0 mass% or less;
Mixing cement, the fine aggregate, and water;
The calcium-containing waste material is
The insoluble residue measured in accordance with JIS R 5202:2010 is 20.0% by mass or more and 90.0% by mass or less,
Contains 5.0% by mass or more of calcium carbonate, and
The present invention provides a method for producing a mortar composition, in which the residual amount of CaO, excluding the amount of CaO derived from calcium carbonate, is 18.0 mass % or less.

According to the present disclosure, a mortar composition and a method for producing the same are provided, which have the same strength development as mortars using current cements and are particularly excellent in early strength while reducing the environmental load by effectively utilizing waste and by-products. Furthermore, the mortar composition contains carbonates formed by fixation of _CO2 , and therefore can contribute to reducing _CO2 emissions.

Unless otherwise specified, the materials exemplified in this disclosure may be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the mortar composition according to this disclosure, the content of each component in the mortar composition means the total amount of the multiple substances present in the mortar composition, unless otherwise specified.

One embodiment of the mortar composition according to the present disclosure includes cement, fine aggregate, and water.

As the cement, any cement known in the art can be used without any particular restrictions. For example, ordinary Portland cement, high-early-strength Portland cement, moderate-heat cement, low-heat cement, oil well cement, etc. can be used. From the viewpoint of ease of availability and further improving early strength, the cement preferably contains at least one of ordinary Portland cement and high-early-strength Portland cement, more preferably contains at least ordinary Portland cement, and it is also possible to use only ordinary Portland cement.

The cement clinker in the cement contains _C3S , _C2S , _C3A , and _C4AF . The contents of _C3S , _C2S , _C3A , and _C4AF can be calculated by the Bogue formula. The Bogue formula is a widely used formula for calculating the contents of major minerals in cement clinker from the content ratios of their chemical compositions. The Bogue formula shown below can be used to calculate the contents of tricalcium silicate ( _3CaO.SiO2 , _C3S ), dicalcium silicate ( _2CaO.SiO2 , _C2S ), tricalcium _aluminate ( _3CaO.Al2O3 , _C3A ), and tetracalcium _aluminate ferroferrate ( _{4CaO.Al2O3.Fe2O3} , _C4AF ) in cement clinker. The chemical formulas represent the content ratios (mass%) of each compound indicated by chemical analysis values according to JIS _R 5204: ₂₀₁₉ "Fluorescent X-ray analysis method for cement".

<Bogue Style>
C ₃ S [mass %] = (4.07 x CaO [mass %]) - (7.60 x SiO ₂ [mass %]) - (6.72 x Al ₂ O ₃ [mass %]) - (1.43 x Fe ₂ O ₃ [mass %]) - (2.85 x SO ₃ [mass %])
C ₂ S [mass %] = (2.87 x SiO ₂ [mass %]) - (0.754 x C ₃ S [mass %])
C ₃ A [mass %] = (2.65 x Al ₂ O ₃ [mass %]) - (1.69 x Fe ₂ O ₃ [mass %])
C ₄ AF [mass%] = 3.04×Fe ₂ O ₃ [mass%]

The amount of _C3S in the cement clinker in the cement is preferably 30.0 mass% or more, more preferably 40.0 mass% or more, even more preferably 50.0 mass% or more, even more preferably 54.0 mass% or more, and particularly preferably 56.0 mass% or more. By making the value of the _C3S amount to be the above value or more, the early strength of the mortar composition during hardening can be further improved.
The amount of _C3S in the cement clinker is preferably 70.0 mass% or less, more preferably 66.0 mass% or less, even more preferably 63.0 mass% or less, even more preferably 59.0 mass% or less, and particularly preferably 57.0 mass% or less. By making the value of the amount of _C3S equal to or less than the above value, heat generation during hardening of the mortar composition can be suppressed.

The amount of _C2S in the cement clinker is preferably 5.0 mass% or more, more preferably 10.0 mass% or more, even more preferably 12.0 mass% or more, even more preferably 15.0 mass% or more, and particularly preferably 18.0 mass% or more. By making the value of the amount of _C2S equal to or more than the above value, the long-term strength of the hardened mortar composition can be further improved.
The amount of _C2S in the cement clinker is preferably 50.0 mass% or less, more preferably 40.0 mass% or less, even more preferably 35.0 mass% or less, even more preferably 30.0 mass% or less, and particularly preferably 22.0 mass% or less. By making the value of the amount of _C2S less than the above value, the early strength of the mortar composition during hardening can be further improved.

The amount of _C3A in the cement clinker is preferably 7.0 mass% or more, more preferably 8.0 mass% or more, even more preferably 8.5 mass% or more, even more preferably 9.0 mass% or more, and particularly preferably 9.5 mass% or more. By making the amount of _C3A equal to or more than the above value, it is possible to produce a mortar composition that increases the amount of waste and by-products such as coal ash that are used as a raw material for cement clinker.
The amount of _C3A in the cement clinker is preferably 13.0 mass% or less, more preferably 12.0 mass% or less, even more preferably 11.0 mass% or less, even more preferably 10.0 mass% or less, and particularly preferably 9.8 mass% or less. By making the amount of _C3A less than the above value, it is possible to further reduce the increase in the amount of heat generated when the mortar composition hardens.

The amount of _C4AF in the cement clinker is preferably 7.0% by mass or more, more preferably 8.0% by mass or more, even more preferably 9.0% by mass or more, even more preferably 9.5% by mass or more, and particularly preferably 10.0% by mass or more. By making the amount of _C4AF equal to or more than the above value, a mortar composition can be produced in which the amount of waste and by-products such as coal ash used as the raw material for the cement clinker is increased.
The _C4AF content in the cement clinker is preferably 14.0 mass% or less, more preferably 13.0 mass% or less, even more preferably 12.0 mass% or less, even more preferably 11.0 mass% or less, and particularly preferably 10.5 mass% or less. By making the _C4AF content equal to or less than the above value, the increase in the amount of heat generated during hardening of the mortar composition can be further reduced.

The cement clinker content is preferably 3% by mass or more and 70% by mass or less, more preferably 9% by mass or more and 45% by mass or less, and even more preferably 18% by mass or more and 27% by mass or less, when the mortar composition is 100% by mass.

The cement may contain gypsum. For example, gypsum dihydrate, gypsum hemihydrate, anhydrous gypsum, etc. may be used as the gypsum. One type of gypsum may be used alone, or a combination of two or more types may be used. The content of gypsum in the cement may be equivalent to the content of gypsum in general Portland cement. Specifically, the content of gypsum in the cement is preferably 0.5% by mass or more and _3.5 % by mass or less, more preferably 0.7% by mass or more and 3.0% by mass or less, and even more preferably 1.0% by mass or more and 2.5% by mass or less, based on the total amount of cement being 100% by mass, in terms of SO 3.

The cement may be commercially available Portland cement, or may be a mixture of cement clinker, gypsum, limestone and/or calcium carbonate, which have been separately ground and mixed. It may also be a mixture made by grinding two or more materials simultaneously.

The cement content in the mortar composition according to the present disclosure is preferably 5% by mass or more and 75% by mass or less, more preferably 10% by mass or more and 50% by mass or less, and even more preferably 20% by mass or more and 30% by mass or less, based on the mortar composition.
Setting the cement content to 5% by mass or more has the advantage of improving the strength development of the mortar composition, while setting the cement content to 75% by mass or less has the advantage of reducing the amount of heat generated during hardening of the mortar composition.

The fine aggregates referred to in this disclosure include calcium-containing waste and fine aggregates other than calcium-containing waste (hereinafter also referred to as "fine aggregate materials"). In this disclosure, "calcium-containing waste" refers to waste that does not have a specific use and is derived from various waste materials that are normally disposed of, and that contains calcium.

The calcium-containing waste is derived from waste materials such as waste concrete, waste mortar, waste cement paste, concrete sludge, paper sludge, blast furnace slag, converter slag, electric furnace slag, slowly cooled slag, chlorine bypass dust, coal ash, biomass ash, or incineration ash. The calcium-containing waste is not the waste materials themselves, but the residues remaining after calcium is extracted from the waste materials. In other words, the calcium-containing waste in the present disclosure is the calcium-containing waste after calcium extraction.
The waste material preferably contains calcium in an amount calculated as CaO of 5.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 20.0% by mass or more, from the viewpoint of enabling efficient recovery of calcium from the waste material and contributing to resource recycling.

In particular, the waste material is preferably one or more selected from waste concrete, waste mortar, and waste cement paste. In other words, the calcium-containing waste is preferably derived from waste material selected from waste concrete, waste mortar, and waste cement paste, and more specifically, is the residue after calcium is extracted from waste material selected from waste concrete, waste mortar, and waste cement paste. By using the residue of these waste materials as a component of fine aggregate, it is possible to effectively utilize materials that have been discarded up to now, and reduce the environmental load. In addition, the mortar composition of the present disclosure containing calcium-containing waste has a strength development level equivalent to that of ordinary Portland cement, and is particularly excellent in early strength.

The calcium-containing waste has an insoluble residue measured in accordance with JIS R 5202:2010 "Methods for Chemical Analysis of Cement" of preferably 20.0% by mass, more preferably 30.0% by mass or more, even more preferably 40.0% by mass or more, and even more preferably 50.0% by mass or more. By setting the insoluble residue of the calcium-containing waste to the above value or more, the amount of components with large particle size and low reactivity, such as sand, can be increased, and the fluidity of the mortar composition can be improved.
In addition, the calcium-containing waste has an insoluble residue of preferably 90.0% by mass or less, more preferably 75.0% by mass or less, and even more preferably 60.0% by mass or less. By setting the insoluble residue of the calcium-containing waste to the above value or less, the fine particles can be increased, and the strength development of the mortar can be improved.
The insoluble residue of the calcium-containing waste can be adjusted to the above-mentioned value by, for example, crushing, grinding, sieving, classifying, or other processes to separate soft components with relatively low strength, such as cement paste, from hard components with high crystallinity, such as sand.

The calcium-containing waste preferably contains 5.0% by mass or more of calcium carbonate, more preferably 10.0% by mass or more, more preferably 12.0% by mass or more, even more preferably 15.0% by mass or more, and even more preferably 20.0% by mass or more. By setting the calcium carbonate content in the calcium-containing waste to the above value or more, the mortar composition according to the present disclosure has a strength development equivalent to that of ordinary Portland cement, and is particularly excellent in early strength. In addition, since a sufficient amount of calcium carbonate formed by fixation of CO ₂ is contained in the calcium-containing waste, it can contribute to reducing CO ₂ emissions.
The higher the proportion of calcium carbonate contained in the calcium-containing waste, the more desirable it is from the standpoint of improving the strength development of the mortar composition according to the present disclosure; however, if the proportion of calcium carbonate is as high as about 10.0 mass %, the strength development is sufficiently improved.

The amount of calcium carbonate contained in the calcium-containing waste is measured, for example, by TG-DTA. In this measurement, the weight loss in the temperature range of 500°C to 800°C is assumed to be the decarbonation of _CO2 from calcium carbonate, and the amount of calcium carbonate can be calculated from the weight loss value.

In calcium-containing waste, the residual amount of CaO minus the amount of CaO derived from calcium carbonate is preferably 18.0% by mass or less, more preferably 15.0% by mass or less, even more preferably 12.0% by mass or less, and even more preferably 10.0% by mass or less. The residual amount of CaO means the degree of calcium extraction when calcium-containing waste is obtained from waste materials such as waste concrete and waste mortar. Setting the residual amount of CaO to the above value or less means that calcium is sufficiently extracted when calcium-containing waste is obtained from the waste materials, so it is advantageous from the viewpoint of effective use of calcium and from the viewpoint of effectively obtaining calcium carbonate by reacting calcium with CO _2. From this viewpoint, there is no particular limit to the lower limit of the residual amount of CaO, but it may be 0% by mass or more, 3.0% by mass or more, 6.0% by mass or more, or 9.0% by mass or more.
The amount of remaining CaO is measured by the following method. First, the total CaO content is calculated from chemical composition analysis using fluorescent X-rays. Next, the amount of calcium carbonate is calculated from the following formula, assuming that the weight loss at 500°C to 800°C is decarbonation from calcium carbonate, based on TG-DTA measurement.
Amount of calcium carbonate (mass%)=(Weight loss from 500°C to 800°C) (mass%)×100/44
The remaining amount of CaO after subtracting the amount of CaO derived from calcium carbonate is calculated by the following formula.
Residual amount of CaO (mass%)=Total content of CaO (mass%)−(amount of calcium carbonate) (mass%)×56/100

The calcium-containing waste preferably has an R ₂ O content defined by the following formula (1) of 2.5 mass% or less, more preferably 2.0 mass% or less, and even more preferably 1.5 mass% or less. From the viewpoint of suppressing the alkali-silica reaction, it is desirable to reduce the total amount of alkali in cement and concrete, and it is desirable to reduce the R ₂ O content of the calcium-containing waste. The R ₂ O content of the calcium-containing waste is determined by chemical composition analysis using fluorescent X-rays.
Amount of R ₂ O [mass %] = Na ₂ O + K ₂ O × 0.658 [mass %] (1)
Na ₂ O and K ₂ O represent the contents [mass %] of Na ₂ O and K ₂ O, respectively.

The calcium-containing waste has a basicity of 0.50 or more, more preferably 0.70 or more, and even more preferably 0.90 or more. In general, basicity is an index representing the reactivity of ground granulated blast furnace slag, and the higher the basicity, the higher the reactivity and the better the strength development. Similarly, the higher the basicity, the better the strength development when calcium-containing waste is added. From this viewpoint, there is no particular upper limit on the basicity, but it may be, for example, 3.0 or less, 2.0 or less, 1.5 or less, or 1.0 or less. The basicity of the calcium-containing waste is calculated from the component values of chemical component analysis by fluorescent X-rays using the following formula (2).
Basicity = (CaO + Al ₂ O ₃ + MgO) / SiO ₂ (2)
In formula (2), CaO, Al ₂ O ₃ , MgO and SiO ₂ represent the contents [mass %] of CaO, Al ₂ O ₃ , MgO and SiO ₂ , respectively.

The calcium-containing waste according to the present disclosure preferably has a predetermined particle size distribution. In detail, when the calcium-containing waste is taken as 100 parts by mass, the 0.3 mm sieve residue is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more. The 0.3 mm sieve residue of 40 parts by mass or more has the advantage that the proportion of large-grained components that can be used as aggregate is high and the fine particles are small, resulting in good fluidity.
In addition, when the calcium-containing waste is taken as 100 parts by mass, the 0.3 mm sieve residue is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less. The 0.3 mm sieve residue of 90 parts by mass or less has the advantage that the strength development is improved by containing a predetermined amount of fine particles.

The coarse particle ratio of the calcium-containing waste is preferably 1.50 or more, more preferably 1.70 or more, and even more preferably 1.90 or more. Having a coarse particle ratio of the above value or more has the advantage that the proportion of large-grained components that can be used as aggregate is high and the fine particles are low, resulting in good fluidity.
The coarse particle ratio of the calcium-containing waste is preferably 4.00 or less, more preferably 3.00 or less, and further preferably 2.50 or less.
The coarse grain ratio can be measured, for example, in accordance with JIS A 1102:2020.

Calcium-containing waste is a residue remaining after calcium is extracted from calcium-containing waste materials, and there is no particular restriction on the method for extracting calcium from the waste materials. As a method for efficiently and sufficiently extracting calcium from the waste materials, it is preferable to adopt a method in which the carbon dioxide partial pressure is made higher than atmospheric pressure. Specifically, it is preferable to adopt a method comprising the following steps (a) to (c):
(a) preparing a powder of calcium-containing waste material;
(b) A step of setting the partial pressure of carbon dioxide to more than 0.1 MPa and not more than 5.0 MPa, and dispersing or dissolving the powder in water under said partial pressure to prepare a liquid to be extracted.
(c) recovering a solid residue from the liquid to be extracted.

The powdering of the waste material in step (a) can be carried out using various conventionally known techniques. The average particle size of the powdered waste material may be set to, for example, 10 μm or more and 5 mm or less, so long as it has a large specific surface area that allows calcium to be efficiently extracted from the waste material. This step not only includes the actual crushing of the waste material, but also includes cases where finely powdered waste material containing calcium is already obtained, such as incineration ash discharged from a thermal power plant.

In step (b), by setting the partial pressure of carbon dioxide in the gas phase in contact with the liquid to be extracted within the above range, the calcium ion concentration extracted into the liquid phase can be increased, and the efficiency of recycling calcium from calcium-containing waste materials can be improved. From this perspective, it is even more preferable that the partial pressure of carbon dioxide is 0.1 MPa or more and 3 MPa or less.

The components other than carbon dioxide in the gas phase can be components generally contained in the atmosphere. That is, examples of components other than carbon dioxide in the gas phase include nitrogen and oxygen. The gas phase is conveniently a gas in which carbon dioxide has been supplied to the atmosphere to increase the partial pressure of carbon dioxide.

From the viewpoint of efficient extraction of calcium, it is preferable to carry out the (b) step by adding the pulverized waste to water under the above-mentioned carbon dioxide partial pressure and stirring for a predetermined period of time, for example, from 1 minute to 90 minutes.
From the same viewpoint, the liquid to be extracted is preferably kept at 20°C or higher and 80°C or lower, more preferably 20°C or higher and 50°C or lower, and even more preferably 20°C or higher and 30°C or lower.

In step (c), it is preferable to carry out the solid-liquid separation operation while maintaining the partial pressure of carbon dioxide in the gas phase within the above-mentioned range and the temperature of the liquid to be extracted within the above-mentioned range. The solid-liquid separation can be carried out using a conventionally known filtration technique. Seed crystals may also be added to the liquid phase.

The calcium-containing waste thus obtained preferably has an average particle size of 10 μm or more and 1000 μm or less, from the viewpoint of improving the strength development of the mortar composition according to the present disclosure. From the viewpoint of making this advantage more prominent, the average particle size of the calcium-containing waste is more preferably 300 μm or more and 600 μm or less, and even more preferably 400 μm or more and 500 μm or less.
The average particle size of the calcium-containing waste can be determined by particle size measurement by sieving, etc. As a specific method, for example, the sieving test method for aggregates in JIS A 1102:2014 can be used to measure the average particle size in the same manner as the sieving test for fine aggregates.

The fine aggregate according to the present disclosure preferably contains 1.0% by mass or more of calcium-containing waste, more preferably 2.5% by mass or more, and even more preferably 7.5% by mass or more. By containing 1.0% by mass or more of calcium-containing waste in the fine aggregate, materials that have been discarded up until now can be effectively utilized, and the environmental burden can be reduced.
The fine aggregate preferably contains 15.0% by mass or less of calcium-containing waste, more preferably 12.0% by mass or less, and even more preferably 7.5% by mass or less. When the fine aggregate contains 15.0% by mass or less of calcium-containing waste, the mortar composition according to the present disclosure has a strength development equivalent to that of ordinary Portland cement, and is particularly excellent in early strength.

The content of the calcium-containing waste in the mortar composition according to the present disclosure is preferably 0.5% by mass or more, more preferably 2.5% by mass or more, and even more preferably 5.0% by mass or more, based on the mortar composition. By setting the content of the calcium-containing waste to 0.5% by mass or more, materials that have been discarded up to now can be effectively utilized, and the environmental load can be reduced.
The content of the calcium-containing waste is preferably 12.0% by mass or less, more preferably 7.5% by mass or less, and even more preferably 5.0% by mass or less, based on the mortar composition. By setting the content of the calcium-containing waste to the above value or less, the mortar composition according to the present disclosure has a strength development at the same level as that of ordinary Portland cement, and is particularly excellent in early strength.

The fine aggregate material contained in the fine aggregate according to the present disclosure is not particularly limited, and various fine aggregates used in ordinary mortar compositions can be used. For example, fine aggregate materials that can be used include silica sand, river sand, sea sand, mountain sand, crushed sand, hard blast furnace slag fine aggregate, blast furnace slag fine aggregate, copper slag fine aggregate, and electric furnace oxidized slag fine aggregate. The fine aggregate according to the present disclosure may contain two or more of these fine aggregate materials. As defined in JIS A 0203:2014 "Terminology for Concrete", fine aggregate is an aggregate that passes entirely through a 10 mm mesh sieve and 85% or more by mass passes through a 5 mm mesh sieve.

The fine aggregate according to the present disclosure preferably has a predetermined particle size distribution. In detail, when the fine aggregate is taken as 100 parts by mass, the part passing through a 0.063 mm sieve is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.4 parts by mass or more, and even more preferably 0.5 parts by mass or more. Having the part passing through a 0.063 mm sieve of 0.1 parts by mass or more has the advantage of improving the strength development.
When the amount of fine aggregate is 100 parts by mass, the amount passing through a 0.063 mm sieve is preferably 3.0 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.8 part by mass or less, and even more preferably 0.7 part by mass or less. Having the amount passing through a 0.063 mm sieve of 1.0 part by mass or less has the advantage of improving fluidity.

The water content in the mortar composition according to the present disclosure is preferably 5.0% by mass or more and 30.0% by mass or less, more preferably 7.5% by mass or more and 20.0% by mass or less, and even more preferably 10.0% by mass or more and 15.0% by mass or less. Setting the water content within the above range has the advantage of improving fluidity and workability.

The mortar composition according to the present disclosure may contain limestone in addition to cement, fine aggregate, and water. As the limestone, for example, powders containing calcium carbonate as the main component, such as limestone, limestone powder, and limestone powder, which are generally available on the market, may be used. The limestone preferably includes limestone that conforms to the minor mixing components described in JIS R 5210:2019 "Portland cement".

The limestone content in the mortar composition according to the present disclosure is preferably 10.0 mass% or less, more preferably 5.0 mass% or less, and even more preferably 2.0 mass% or less, based on the mortar composition. By making the limestone content less than the above value, the strength development is good.
The limestone content in the mortar composition according to the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more, based on the mortar composition. By making the limestone content equal to or more than the above value, it contributes to reducing _CO2 emissions.

In addition to cement, fine aggregate, and water, the mortar composition according to the present disclosure may contain other components within the scope of the present disclosure. Examples of other components include coarse aggregate, calcium hydroxide, silica powder, other powders containing calcium (excluding gypsum and limestone), water reducers for concrete, accelerators, and retarders.

Examples of coarse aggregates include river gravel, sea gravel, mountain gravel, crushed stone, and crushed slag stone. These can be used alone or in combination. Examples of these coarse aggregates include those specified in JIS A5005:2020.

The mortar composition according to the present disclosure can be suitably obtained by a production method including the following steps (d) and (e).
(d) A step of mixing a fine aggregate material with the calcium-containing waste so that the calcium-containing waste is contained in the fine aggregate at preferably 1.0 mass % or more and 15.0 mass % or less.
(e) mixing cement, fine aggregate, and water;

The contents of this disclosure will be described in more detail below with reference to examples, comparative examples, and reference examples. However, this disclosure is not limited to the following examples. Unless otherwise specified, "%" means "% by mass."

(Examples 1 and 2 and Reference Example 1)
[Raw materials for mortar composition]
The following materials were used as raw materials for the mortar composition.

(1) Preparation of cement clinker As the cement clinker, ordinary Portland cement clinker having a mineral composition according to the Bogue formula shown in Table 1 below was used. The chemical composition of the cement used in the calculation of the Bogue formula was measured in accordance with the method described in JIS R 5204:2019 "Method for fluorescent X-ray analysis of cement".

(2) Preparation of Gypsum Gypsum satisfying the requirements described in JIS R 9151:2009 “Natural gypsum for cement” was used.

(3) Preparation of Limestone Powder The limestone (LS) used was a fine powder of limestone obtained by pulverizing limestone having a calcium carbonate content of 90% by mass or more, an aluminum oxide content of 1.0% by mass or less, and satisfying the requirements for minor mixed components described in JIS R 5210:2019 “Portland cement” (Blaine specific surface area value: 7,470 cm ² /g).

(4) Preparation of calcium-containing waste Waste concrete was crushed and sieved to obtain powder with sieving openings of 2 mm or less. The powder was then poured into pure water to obtain a dispersion.
The dispersion was airtightly packed in a pressure-resistant stirring tank type extraction apparatus, and while stirring, carbon dioxide was supplied into the apparatus and the partial pressure was increased to 1.0 MPa to extract calcium into the liquid phase. During this time, the pressure of the gas phase was monitored and the partial pressure of carbon dioxide was maintained.
Thereafter, the apparatus was subjected to solid-liquid separation into a liquid phase and an extraction residue, and the liquid phase to which the seed crystals had been added was depressurized to obtain calcium carbonate. The solid content obtained by the solid-liquid separation was recovered to obtain an extraction residue. The extraction residue was dried at 105° C. to remove moisture, and the intended calcium-containing waste was obtained.

The physical properties of calcium-containing waste are shown in Tables 2 and 3. The densities shown in these tables were measured using an automatic density meter (instrument: MAT-7000, Seishin Enterprise Co., Ltd.).

The chemical components of calcium-containing waste were determined by chemical analysis using the fundamental parameter method of fluorescent X-rays (equipment used: Rigaku ZSX-100e). Ignition loss (ig. loss) and insoluble residue were measured according to JIS R 5202:2010 "Methods for chemical analysis of cement". The calcium carbonate content of calcium-containing waste was calculated by assuming that the mass loss from 500°C to 800°C in TG-DTA measurement (equipment name: Hitachi High-Technologies STA-7300, nitrogen gas flow environment, heating rate: 10°C/min) is equal to the mass of carbon dioxide generated by decarbonation of calcium carbonate.

(5) Preparation of fine aggregate material Standard sand from the Cement Association was used as the fine aggregate material.

[Production of fine aggregate]
The fine aggregate material and calcium-containing waste were mixed in the ratios shown in Table 4 to obtain fine aggregates A and B. The particle sizes of fine aggregates A and B are shown in Table 4. For reference, the particle sizes of calcium-containing waste and standard sand of the Cement Association are also shown in Table 4. It can be seen that the calcium-containing waste has a particle size distribution relatively close to that of the standard sand. It can also be seen that the calcium-containing waste contains about 5 mass% of fine powder of 0.063 mm or less.

[Measurement of coarse particle ratio]
The coarse aggregate ratios of calcium-containing waste, standard sand, and fine aggregates A and B were measured in accordance with JIS A1102:2020. In detail, the sum of the percentages of the mass of the sample remaining on each of the 80 mm, 40 mm, 20 mm, 10 mm, 5 mm, 2.5 mm, 1.2 mm, 0.6 mm, 0.3 mm, and 0.15 mm sieves was divided by 100 to calculate the coarse aggregate ratio. The larger the coarse aggregate ratio, the coarser the particle size. The results are shown in Table 4.

[Production of mortar composition]
A base cement was obtained by adding 1.0% gypsum in terms of _SO3 to Portland cement clinker having the chemical composition shown in Table 1, mixing and grinding the mixture. A cement composition was obtained by mixing the base cement and limestone powder in the proportions shown in Table 5. The Blaine specific surface area of this cement composition was measured in accordance with the description of JIS R 5201:2015 "Physical measurement methods for cement" and found to be 3290 ^cm2 /g.
The cement composition was mixed with various fine aggregates and water to obtain mortar compositions. The types of fine aggregates used and the mixing ratios of each component were as shown in Table 5.

[Evaluation of mortar compressive strength of mortar composition]
The mortar compressive strength of the obtained mortar composition was evaluated using a 40×40×160 mm hardened mortar body in accordance with JIS R 5201. The compressive strengths of Examples 1 and 2 were evaluated as a compressive strength ratio when the compressive strength of the specimen of Reference Example 1 was taken as 100. The results are shown in Table 5.

As is clear from Table 5, the mortar compositions produced using fine aggregates in which calcium-containing waste was mixed at 5% or 10% with respect to standard sand have mortar compressive strengths equal to or greater than those of mortar compositions produced without adding calcium-containing waste. In particular, at a material age of 7 days, it can be seen that the mortar compressive strength is greatly increased by adding calcium-containing waste.

Claims (6)

A mortar composition comprising cement, fine aggregate, and water,
The fine aggregate contains calcium-containing waste in an amount of 1.0% by mass or more and 15.0% by mass or less,
The calcium-containing waste material is
The insoluble residue measured in accordance with JIS R 5202:2010 is 20.0% by mass or more and 90.0% by mass or less,
Contains 5.0% by mass or more of calcium carbonate, and
The residual amount of CaO, which is obtained by subtracting the amount of CaO derived from calcium carbonate , is 18.0% by mass or less,
When the calcium-containing waste is taken as 100 parts by mass, the 0.3 mm sieve residue is 40 parts by mass or more and 90 parts by mass or less,
When the fine aggregate is taken as 100 parts by mass, the part passing through a 0.063 mm sieve is 0.1 parts by mass or more and 3.0 parts by mass or less, and the part remaining on a 2.5 mm sieve is 0 parts by mass.
The calcium-containing waste has a coarse particle ratio of 1.50 or more and 4.00 or less,
The calcium-containing waste has an average particle size of 300 μm or more and 600 μm or less . The mortar composition according to claim 1, wherein the calcium-containing waste has an R ₂ O content of 2.5 mass% or less, the R 2 O content being represented by the following formula (1):
Amount of R ₂ O [mass %] = Na ₂ O + K ₂ O × 0.658 [mass %] (1) The mortar composition according to claim 1 or 2, wherein the calcium-containing waste is derived from a waste material selected from waste concrete, waste mortar, and waste cement paste. A method for producing a mortar composition comprising cement, fine aggregate, and water, comprising the steps of:
A step of obtaining fine aggregate by mixing a fine aggregate material with the calcium-containing waste so that the calcium-containing waste is contained in the fine aggregate in an amount of 1.0 mass% or more and 15.0 mass% or less;
Mixing cement, the fine aggregate, and water;
The calcium-containing waste material is
The insoluble residue measured in accordance with JIS R 5202:2010 is 20.0% by mass or more and 90.0% by mass or less,
Contains 5.0% by mass or more of calcium carbonate, and
The residual amount of CaO, which is obtained by subtracting the amount of CaO derived from calcium carbonate, is 18.0% by mass or less,
When the calcium-containing waste is taken as 100 parts by mass, the 0.3 mm sieve residue is 40 parts by mass or more and 90 parts by mass or less,
When the fine aggregate is taken as 100 parts by mass, the part passing through a 0.063 mm sieve is 0.1 parts by mass or more and 3.0 parts by mass or less, and the part remaining on a 2.5 mm sieve is 0 parts by mass.
The calcium-containing waste has a coarse particle ratio of 1.50 or more and 4.00 or less,
The method for producing a mortar composition, wherein the calcium-containing waste has an average particle size of 300 μm or more and 600 μm or less . the calcium-containing waste is a residue remaining after calcium is extracted from a waste material by dissolving the calcium contained in the waste material into a liquid phase,
The method according to claim 4 , wherein the waste material is at least one selected from the group consisting of waste concrete, waste mortar, and waste cement paste. Prepare a powder of waste material containing calcium;
The partial pressure of carbon dioxide is set to more than 0.1 MPa and not more than 5.0 MPa, and the powder is dispersed or dissolved in water under the partial pressure to prepare a liquid to be extracted;
The method according to claim 4 or 5 , wherein the calcium-containing waste is obtained by recovering a solid residue from the liquid to be extracted.