Cement composition, self-leveling material or repair material

Abstract

To provide a cement composition comprising Portland cement and hemihydrate gypsum, which can form a mortar hardened body having excellent dimensional stability in water.SOLUTION: There is provided a cement composition comprising a hydraulic component composed of Portland cement and hemihydrate gypsum and a fine aggregate. The total amount of soluble silica and soluble alumina, measured in accordance with JIS A 1145:2017 [Method of test for alkali-silica reactivity of aggregates by chemical method], is less than 50 mmol / L per 25 g of a fine aggregate. The content of the fine aggregate is 30 to 80 mass% based on the total amount of the cement composition. The content of the Portland cement is 20 to 60 mass% and the content of the hemihydrate gypsum is 40 to 80 mass%, based on the total amount of the hydraulic component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement composition and a self-leveling or repair material. [Background technology]

[0002] Generally, cement compositions are required to have excellent workability, sufficient compressive strength after hardening, and excellent dimensional stability. In particular, materials such as self-leveling materials and repair materials require excellent rapid hardening properties to shorten construction periods, and also require extremely good dimensional stability to prevent cracking and peeling from the adhesive surface after hardening.

[0003] Against this background, compositions containing Portland cement and gypsum hemihydrate have been the subject of much research, as they are expected to provide excellent rapid hardening properties and good dimensional stability in air due to the hemihydrate, as well as sufficient strength development due to the Portland cement.Patent Document 1 discloses a cement composition that contains Portland cement and gypsum hemihydrate as a material containing Portland cement and gypsum hemihydrate, and further contains a predetermined amount of inorganic fine powder, typified by calcium carbonate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-172801 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional cement compositions containing Portland cement and gypsum hemihydrate, dimensional stability, one of the important properties, has not been fully investigated, and there is still room for improvement. In addition to drying shrinkage, which is a common problem with general construction materials that use Portland cement, cement compositions containing Portland cement and gypsum hemihydrate are concerned about deterioration of dimensional stability under water immersion conditions (underwater dimensional stability), which is an issue specific to gypsum hemihydrate.

[0006] Therefore, a main object of the present invention is to provide a cement composition containing Portland cement and gypsum hemihydrate, which is capable of forming a hardened mortar having excellent underwater dimensional stability. [Means for solving the problem]

[0007] As a result of extensive research conducted by the present inventors to solve the above problems, they discovered that the underwater dimensional stability of the resulting hardened mortar can be improved by using a specific fine aggregate in a cement composition containing a hydraulic component consisting of Portland cement and gypsum hemihydrate, adjusting the content of the fine aggregate to fall within a specific range, and adjusting the content of Portland cement and the content of gypsum hemihydrate to fall within a specific range, thereby completing the present invention.

[0008] The present invention provides the cement compositions described in [1] to [4] and the self-leveling material or repair material described in [5]. [1] A cement composition comprising a hydraulic component consisting of Portland cement and hemihydrate gypsum, and fine aggregate, The fine aggregate has a total dissolved silica content and dissolved alumina content of less than 50 mmol / L per 25 g of fine aggregate, as measured in accordance with JIS A 1145:2017 "Test method for alkali-silica reactivity of aggregate (chemical method)", The content of the fine aggregate is 30 to 80 mass% based on the total amount of the cement composition, The content of the Portland cement is 20 to 60 mass% and the content of the hemihydrate gypsum is 40 to 80 mass% based on the total amount of the hydraulic components. Cement compositions. [2] The proportion of the dissolved silica content is 60% or more based on the total amount of the dissolved silica content and the dissolved alumina content. [1] The cement composition according to [1]. [3] The content of the hydraulic component is 15 to 70 mass% based on the total amount of the cement composition. [1] or [2]. The cement composition according to [1] or [2]. [4] Further containing at least one additive selected from the group consisting of a fluidizing agent, a thickening agent, a setting retarder, and an antifoaming agent; The cement composition according to any one of [1] to [3]. [5] A cement composition according to any one of [1] to [4] and water. Self-leveling or repair material. [Effects of the Invention]

[0009] According to the present invention, there is provided a cement composition containing Portland cement and gypsum hemihydrate, which is capable of forming a hardened mortar having excellent underwater dimensional stability. Also, according to the present invention, there is provided a self-leveling material or repair material using such a cement composition. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0011] Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a composition contains multiple substances corresponding to each component, the amount used or content of each component means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0012] [Cement composition] The cement composition of this embodiment contains a hydraulic component consisting of Portland cement and hemihydrate gypsum, and fine aggregate. The cement composition of this embodiment can form a hardened mortar that has excellent underwater dimensional stability, and therefore can be suitably used as a floor underlayment material (such as a self-leveling material) or repair material applied to the floor surface of a structure.

[0013] <Hydraulic component> Examples of Portland cement include ordinary Portland cement, early-strength Portland cement, extra-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement. Also, blended cements such as blast-furnace cement, fly ash cement, and silica cement can be used as a substitute for Portland cement. From the viewpoint of rapid hardening, the Portland cement is preferably ordinary Portland cement, early-strength Portland cement, or extra-early-strength Portland cement.

[0014] The Blaine specific surface area of ​​Portland cement is preferably 3000 to 6000 cm 2 / g, more preferably 4000 to 5000 cm 2 / g, more preferably 4200 to 4800 cm 2 / g. The Blaine specific surface area of ​​Portland cement is a value measured in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement." Portland cement with a specific surface area in this range tends to have improved fluidity and rapid hardening properties when combined with gypsum hemihydrate.

[0015] The content of Portland cement is 20 to 60 mass %, preferably 30 to 57 mass %, and more preferably 40 to 55 mass %, based on the total amount of hydraulic components. When the content of Portland cement is within this range, good fluidity and good rapid hardening properties tend to be more reliably obtained in addition to good underwater dimensional stability.

[0016] Examples of gypsum hemihydrate include α-gypsum hemihydrate, β-gypsum hemihydrate, and a mixture of α-gypsum hemihydrate and β-gypsum hemihydrate.

[0017] The Blaine specific surface area of ​​the hemihydrate gypsum is preferably 2000 to 12000 cm 2 / g. The Blaine specific surface area of ​​gypsum hemihydrate refers to a value measured in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement." When the specific surface area of ​​gypsum hemihydrate is in this range, dimensional stability in water, high fluidity, and rapid hardening tend to be further improved when combined with Portland cement.

[0018] The content of gypsum hemihydrate is 40 to 80 mass%, preferably 43 to 70 mass%, and more preferably 45 to 60 mass%, based on the total amount of hydraulic components. When the content of gypsum hemihydrate is in this range, good fluidity and good rapid hardening properties tend to be more reliably obtained in addition to good underwater dimensional stability.

[0019] The content of the hydraulic component is preferably 15 to 70 mass %, more preferably 20 to 55 mass %, and even more preferably 25 to 45 mass %, based on the total amount of the cement composition.

[0020] <Fine aggregate> The total amount of dissolved silica and dissolved alumina in the fine aggregate, measured in accordance with JIS A 1145:2017 "Test method for alkali-silica reactivity of aggregate (chemical method)", is less than 50 mmol / L per 25 g of fine aggregate.

[0021] The amount of dissolved silica is the value measured in accordance with JIS A 1145:2017 "Testing Methods for Alkali-Silica Reactivity of Aggregates (Chemical Method)." The amount of dissolved alumina is the value quantified by ICP atomic emission spectrometry after dissolving alumina from fine aggregate in accordance with "8.1 Reaction Procedure between Alkali and Test Sample" of JIS A 1145:2017 "Testing Methods for Alkali-Silica Reactivity of Aggregates (Chemical Method)."

[0022] The fine aggregate may be any fine aggregate commonly used in the fields of mortar and concrete, provided that the total amount of dissolved silica and dissolved alumina is less than 50 mmol / L per 25 g of fine aggregate. Examples of such fine aggregate include silica sand, limestone sand, river sand, sea sand, mountain sand, and crushed sand.

[0023] From the viewpoint of dimensional stability in water, the total amount of dissolved silica and dissolved alumina is less than 50 mmol / L, preferably 48 mmol / L or less, more preferably 45 mmol / L or less, even more preferably 42 mmol / L or less, particularly preferably 39 mmol / L or less, especially preferably 36 mmol / L or less, and most preferably 32 mmol / L or less, per 25 g of fine aggregate. The lower limit of the total amount of dissolved silica and dissolved alumina per 25 g of fine aggregate can be, for example, 1 mmol / L or more, 5 mmol / L or more, or 10 mmol / L or more.

[0024] From the viewpoint of dimensional stability in water, the amount of dissolved silica is preferably 40 mmol / L or less, more preferably 35 mmol / L or less, and even more preferably 30 mmol / L or less, per 25 g of fine aggregate. The lower limit of the amount of dissolved silica per 25 g of fine aggregate can be, for example, 10 mmol / L or more, 15 mmol / L or more, or 20 mmol / L or more.

[0025] From the viewpoint of dimensional stability in water, the amount of dissolved alumina is preferably 30 mmol / L or less, more preferably 25 mmol / L or less, even more preferably 20 mmol / L or less, particularly preferably 15 mmol / L or less, particularly preferably 10 mmol / L or less, and most preferably 5 mmol / L or less, per 25 g of fine aggregate. The lower limit of the amount of dissolved alumina per 25 g of fine aggregate can be, for example, 0.1 mmol / L or more, 0.5 mmol / L or more, or 1 mmol / L or more.

[0026] From the viewpoint of dimensional stability in water, the proportion of dissolved silica is preferably 60% or more, more preferably 65% ​​or more, even more preferably 70% or more, particularly preferably 75% or more, especially preferably 80% or more, and most preferably 85% or more, based on the total amount of dissolved silica and dissolved alumina. The upper limit of the proportion of dissolved silica in the total amount of dissolved silica and dissolved alumina can be, for example, 99% or less, 97% or less, or 95% or less, based on the total amount of dissolved silica and dissolved alumina.

[0027] The fine aggregate preferably has a maximum particle size of 0.85 mm or less, and the content of coarse particles with a particle size greater than 0.6 mm in the fine aggregate is 5 mass % or less. The particle size of the fine aggregate refers to a value measured in accordance with the sieving test method for aggregate specified in JIS A 1102:2014 "Sieving test method for aggregate." In addition, in this specification, "coarse particles with a particle size greater than 0.6 mm" refers to the mass fraction (%) of fine aggregate that is retained on a sieve with 0.6 mm meshes.

[0028] The water absorption of the fine aggregate is preferably 3.0% or less. The water absorption of the fine aggregate refers to a value measured in accordance with the method for measuring the water absorption of fine aggregate (unit: %) specified in JIS A 1109:2020 "Testing Method for Density and Water Absorption of Fine Aggregate." The water absorption of the fine aggregate is more preferably 2.75% or less, even more preferably 2.60% or less, and particularly preferably 2.50% or less. The lower limit of the water absorption of the fine aggregate can be 0% or more.

[0029] The content of the fine aggregate is 30 to 80 mass %, preferably 33 to 75 mass %, and more preferably 35 to 70 mass %, based on the total amount of the cement composition. By having the content of the fine aggregate in this range, excellent dimensional stability in water and good fluidity can be obtained.

[0030] <Admixture> The cement composition of this embodiment may further contain an admixture. From the viewpoint of preventing delayed formation of ettringite, the admixture is preferably an admixture with a low alumina content. Examples of admixtures include calcium carbonate and calcium hydroxide. As calcium carbonate, pulverized limestone can be suitably used. The calcium carbonate is not particularly limited as long as it is an inorganic powdery substance containing calcium carbonate as the main component, and pulverized waste concrete, kansui stone, chemically purified calcium carbonate, etc. can be used.

[0031] The content of the admixture is preferably 4 to 28 mass%, more preferably 7 to 25 mass%, and even more preferably 10 to 22 mass%, based on the total amount of the cement composition. When the content of the admixture is within this range, good fluidity, resistance to material separation, and rapid hardening tend to be obtained in addition to good underwater dimensional stability.

[0032] <Additives> The cement composition of the present embodiment may further contain at least one additive selected from the group consisting of a fluidizing agent, a thickening agent, a setting retarder, and an antifoaming agent.

[0033] Examples of the fluidizing agent include commercially available fluidizing agents that also have a water-reducing effect, such as formaldehyde condensates of melamine sulfonic acid, casein, calcium caseinate, polycarboxylic acid compounds, polyether compounds, and polyether polycarboxylic acid compounds. The fluidizing agent is preferably a commercially available fluidizing agent such as a polyether compound or a polyether polycarboxylic acid compound.

[0034] The content of the fluidizing agent is preferably 0.01 to 5.0 mass%, more preferably 0.02 to 3.0 mass%, still more preferably 0.03 to 2.0 mass%, and particularly preferably 0.05 to 1.5 mass%, based on the total amount of the cement composition. When the content of the fluidizing agent is within this range, good fluidity tends to be obtained.

[0035] Examples of the thickener include commercially available thickeners such as cellulose compounds, protein compounds, latex compounds, and water-soluble polymer compounds.

[0036] The viscosity (20°C) of a 2% by mass aqueous solution of the thickener is preferably 50 to 100,000 mPa·s, more preferably 100 to 80,000 mPa·s, even more preferably 200 to 30,000 mPa·s, and particularly preferably 300 to 3,000 mPa·s. The viscosity is a value measured at 20°C using a B-type viscometer on a 2% by mass aqueous solution of the thickener.

[0037] The content of the thickener is preferably 0.01 to 2.0 mass%, more preferably 0.02 to 1.0 mass%, even more preferably 0.04 to 0.8 mass%, and particularly preferably 0.05 to 0.5 mass%, based on the total amount of the cement composition. When the content of the thickener is within this range, good resistance to material separation tends to be obtained.

[0038] Examples of setting retarders include hydroxycarboxylic acids (tartaric acid, citric acid, malic acid, gluconic acid, malic acid, etc.), acids such as phosphoric acid, and alkali metal salts and alkaline earth salts of these acids.

[0039] The content of the set retarder is preferably 0.01 to 2.0 mass%, more preferably 0.02 to 1.0 mass%, even more preferably 0.04 to 0.8 mass%, and particularly preferably 0.05 to 0.5 mass%, based on the total amount of the cement composition. When the content of the set adjuster is within this range, good fluidity and good rapid hardening properties tend to be obtained.

[0040] Examples of antifoaming agents include synthetic substances such as silicone compounds, alcohol compounds, fatty acid ester compounds, and polyether compounds, natural substances derived from plants, and mineral oils. From the viewpoint of cost and availability, the antifoaming agent is preferably a silicone compound, a fatty acid ester compound, or a polyether compound. Adding an antifoaming agent to a cement composition tends to provide a good surface condition and rapid hardening.

[0041] The content of the antifoaming agent is preferably 0.01 to 5.0 mass%, more preferably 0.02 to 2.0 mass%, still more preferably 0.04 to 1.0 mass%, and particularly preferably 0.05 to 0.5 mass%, based on the total amount of the cement composition. When the content of the antifoaming agent is within this range, good surface condition and good rapid hardening properties tend to be obtained.

[0042] The cement composition of the present embodiment may further contain other additives, such as a shrinkage reducing agent and resin powder.

[0043] [Mortar material] The mortar material of this embodiment contains the above-mentioned cement composition and water. The mortar material of this embodiment can be manufactured (prepared) by mixing and kneading the above-mentioned cement composition with a predetermined amount of water. The mortar material of this embodiment has good fluidity, so that when applied to the floor surface of a structure, a horizontal and flat floor surface can be easily formed. A mortar material with workability can be obtained by appropriately changing the amount of water blended when preparing the mortar material. The mortar material of this embodiment can be suitably used as a self-leveling material or repair material.

[0044] Examples of water include tap water, distilled water, deionized water, etc. The amount of water to be added is preferably 20 to 30 parts by mass, more preferably 20 to 29 parts by mass, even more preferably 21 to 28 parts by mass, and particularly preferably 21 to 27 parts by mass, per 100 parts by mass of the cement composition.

[0045] [Hardened mortar] The hardened mortar of this embodiment can be obtained by hardening the above-mentioned mortar material. The hardened mortar has rapid hardening properties that allow light walking on the surface early, appropriate compressive strength, and underwater dimensional stability, and therefore can be used as a floor underlayment material (e.g., a self-leveling material) or repair material for structures in buildings such as schools, apartment buildings, convenience stores, and hospitals.

[0046] [evaluation] <Underwater dimensional stability> Underwater dimensional stability can be evaluated by measuring the dimensional change of a hardened mortar when immersed in water, in accordance with the length change measurement method described in JASS 15M-103 "Quality Standard for Self-Leveling Materials" of the Architectural Institute of Japan (General Incorporated Association). According to JIS A 1129-2:2010 "Contact Gauge Method," the length of the hardened mortar is measured immediately after removal from the formwork and after subsequent immersion in water for a specified age. The change in length during immersion relative to the length immediately after removal can be defined as the underwater dimensional change. From the perspective of underwater dimensional stability, the underwater dimensional change at 28 days is preferably in the range of -1000 μm / m (shrinkage) to 1000 μm / m (expansion). A material that satisfies this range of underwater dimensional change at 28 days can be evaluated as having excellent underwater dimensional stability. [Example]

[0047] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0048] [Materials used] The materials used in the examples and comparative examples are shown below. (1) Hydraulic component (1-1) Portland cement Portland cement [PC] (high-early-strength Portland cement, Blaine specific surface area 4620 cm 2 / g) (1-2) Hemihydrate gypsum ·β Hemihydrate gypsum [HH] (Brain specific surface area 4380cm2 / g)

[0049] (2) Fine aggregate The following fine aggregates were used. The dissolved silica content was measured in accordance with JIS A 1145:2017, "Testing Methods for Alkali-Silica Reactivity of Aggregates (Chemical Method)." The dissolved alumina content was measured by dissolving alumina from the fine aggregate in accordance with "8.1 Reaction Procedure between Alkali and Test Sample" in JIS A 1145:2017, "Testing Methods for Alkali-Silica Reactivity of Aggregates (Chemical Method)," and quantifying it using ICP atomic emission spectrometry. Table 1 shows the dissolved silica content, dissolved alumina content, total amount of dissolved silica and dissolved alumina, reduction in alkali concentration, and the ratio of dissolved silica to the total amount of dissolved silica and dissolved alumina per 25g of each fine aggregate. Fine aggregate A (silica sand, maximum particle size 850 μm or less, 0.1% by mass of coarse particles with particle sizes greater than 0.6 mm, water absorption rate 2.2%) Fine aggregate B (silica sand, maximum particle size 850 μm or less, coarse particles with particle sizes greater than 0.6 mm 0.1% by mass, water absorption rate 1.4%) Fine aggregate C (silica sand, maximum particle size 850 μm or less, 0.1% by mass of coarse particles with particle sizes greater than 0.6 mm, water absorption rate 2.2%) Fine aggregate D (silica sand, maximum particle size 850 μm or less, 0.1% by mass of coarse particles with particle sizes greater than 0.6 mm, water absorption rate 1.2%) Fine aggregate E (silica sand, maximum particle size 850 μm or less, coarse particles with particle sizes greater than 0.6 mm 0.1% by mass, water absorption rate 0.29%)

[0050] [Table 1]

[0051] (3)Admixture Calcium carbonate [CC] (Blaine specific surface area 4480 cm 2 / g)

[0052] (4) Admixture The admixtures consist of a superplasticizer, a thickener, a setting retarder, and an antifoaming agent, and Table 2 shows the mixing ratios (mass%) of the admixtures. · Fluidizing agent (polyether polycarboxylic acid compound) Thickener (viscosity of 2% by weight aqueous solution at 20°C: 1017 mPa·s) ·Set retarder (sodium tartrate) Antifoaming agent (polyether type)

[0053] [Table 2]

[0054] [Preparation of cement composition] The above materials (total amount: 10 kg) were mixed in the proportions shown in Table 3 to prepare the cement compositions of Examples 1 to 5 and Comparative Examples 1 to 4. The materials were mixed for 5 minutes using an Eirich mixer. The mass ratios of Portland cement and hemihydrate gypsum in the hydraulic component are shown in Table 4.

[0055] [Table 3]

[0056] [Table 4]

[0057] [Preparation of mortar material] The mortar materials of Examples 1 to 5 and Comparative Examples 1 to 4 were prepared by blending water with the cement compositions of Examples 1 to 5 and Comparative Examples 1 to 4. The mortar materials were prepared in a constant temperature and humidity chamber set at a room temperature of 20°C and a humidity of 65% RH. The amount of water blended in the mortar materials was 26 parts by mass per 100 parts by mass of the cement composition.

[0058] [Measurement of dimensional change in water] The underwater dimensional change was measured in accordance with the length change measurement method specified in JASS 15M-103, "Quality Standards for Self-Leveling Materials," published by the Architectural Institute of Japan (AIJ). The dimensional change was measured when the hardened mortar was immersed in water. The length of the hardened mortar was measured immediately after removal from the formwork and after immersion in water for a specified age, in accordance with JIS A 1129-2:2010, "Contact Gauge Method." The change in length after immersion in water relative to the length immediately after removal was recorded as the underwater dimensional change. Measurements of the underwater dimensional change were performed in a constant temperature and humidity chamber set at a room temperature of 20°C and a humidity of 65%. The underwater dimensional change at 28 days is shown in Table 5.

[0059] [Table 5]

[0060] As shown in Table 5, the mortar materials of Examples 1 to 5 had a smaller positive dimensional change in water and suppressed expansion of the hardened mortar materials than the mortar materials of Comparative Examples 1 to 4. These results confirmed that the cement composition of the present invention can form a hardened mortar material with excellent dimensional stability in water.

Claims

1. A cement composition comprising a hydraulic component consisting of Portland cement and hemihydrate gypsum, and fine aggregate, The fine aggregate has a total amount of dissolved silica and dissolved alumina measured in accordance with JIS A 1145:2017 "Test method for alkali-silica reactivity of aggregate (chemical method)" of less than 50 mmol / L per 25 g of fine aggregate, The content of the fine aggregate is 30 to 80 mass% based on the total amount of the cement composition, The content of the Portland cement is 20 to 60 mass% and the content of the hemihydrate gypsum is 40 to 80 mass% based on the total amount of the hydraulic components. Cement compositions.

2. The proportion of the amount of dissolved silica is 60% or more based on the total amount of the amount of dissolved silica and the amount of dissolved alumina. The cement composition of claim 1.

3. The content of the hydraulic component is 15 to 70 mass% based on the total amount of the cement composition. The cement composition of claim 1.

4. Further containing at least one additive selected from the group consisting of a fluidizing agent, a thickening agent, a setting retarder, and an antifoaming agent; The cement composition of claim 1.

5. The cement composition according to any one of claims 1 to 4 and water are included. Self-leveling or repair material.

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