JP2019172483A - Cement composite material - Google Patents

Abstract

To provide a light-weight cement composite material having rapid-hardening properties and small dry-shrinkage strain.SOLUTION: A cement composite material comprises a cement, a rapid-hardening cement admixture, a polymer for cement admixture, a retarder, and a light-weight aggregate having dry density of 1.0-2.3 g/cm, wherein the polymer for cement admixture is 4-14 pts.mass based on 100 pts.mass of the total of the cement and the rapid-hardening cement admixture. Preferably, the light-weight aggregate is a coarse aggregate having absolute dry density of 1.0-2.0 g/cm.SELECTED DRAWING: None

Description

  The present invention relates to a fast-curing and lightweight cement composite material.

  Currently, concrete structures are aging. As an example of repairing concrete structures, RC floor slabs are being implemented and spread by replacing high-quality precast concrete with floor slabs. In this construction method, it is necessary to place concrete separately when filling the joint between concrete slabs. It is desirable for the concrete to have the same properties as precast concrete. However, it is usually difficult to produce high-quality concrete compared to floor slab concrete because concrete used for filling is usually manufactured and placed on site. is there. The properties required for concrete used for filling are quick hardening for early road opening, light weight from the viewpoint of construction cost reduction by reducing weight, durability against deterioration factors, and adhesion between floor slabs. Considering dimensional stability and the like.

  In order to obtain the strength development property in a short time, a hydraulic material to which a cement or an admixture having a fast setting property is added is used. In addition, a hydraulic composition has been proposed in which a cement-mixing polymer is added to these materials to take into account quick hardening and durability (Patent Documents 1, 2 and the like).

In addition, it is known that mixing of a polymer suppresses deterioration factor penetration from the outside, and it is also known that drying shrinkage strain is reduced. Furthermore, by using a lightweight aggregate for the concrete, it is possible to expect a reduction in drying shrinkage strain due to light weight and self-healing effect.

JP 2014-58437 A Japanese Patent Laying-Open No. 2006-2673

As a result of intensive investigation into the use of a lightweight aggregate and a polymer for admixture with cement when investigating a cement composite having rapid hardening, the present inventors have found that after hardening without losing fast hardening in a certain concrete composition. It was found that a cement composite material with low drying shrinkage strain can be obtained economically. The present invention has been made based on such knowledge.
Therefore, the present invention provides a cement composite material that has fast curing and low drying shrinkage strain.

That is, the present invention provides the following [1] to [3].
[1] A cement, a fast-hardening cement admixture, a cement admixture polymer, a setting retarder, and a lightweight aggregate having an absolute dry density of 1.0 to 2.3 g / cm ³ , and the cement admixture polymer, The cement composite material which is 4-14 mass parts with respect to 100 mass parts of total amounts of a cement and a quick-hardening cement admixture.
[2] The cement composite material according to [1], wherein the lightweight aggregate is a coarse aggregate having an absolutely dry density of 1.0 to 2.0 g / cm ³ .
[3] The cement composite material according to [2], further comprising a fine aggregate having an absolutely dry density of 1.5 to 2.3 g / cm ³ .

  A lightweight cement composite material that is fast-curing and has low drying shrinkage strain can be obtained economically.

Embodiments of the present invention are described below.
The present invention is a cement composite comprising cement, a fast-hardening cement admixture, a cement admixture polymer, a setting retarder, and a lightweight aggregate having an absolutely dry density of 1.0 to 2.3 g / cm ³ .

  As the cement used in the present invention, industrially produced Portland cement can be used. For example, various portland cements such as normal, early strength, very early strength, low heat and moderate heat are listed. In addition, various mixed cements in which fly ash, blast furnace slag, silica fume, limestone fine powder, or the like is mixed with the Portland cement may be used. One kind of these cements or two or more kinds thereof may be used.

The quick-setting cement admixture used in the present invention refers to a material that accelerates hardening early by being added to cement. It is a so-called hardening accelerator for cement and concrete, for example, liquids such as nitrates, nitrites and aluminates, and powders containing calcium aluminates as active ingredients, In particular, from the viewpoint of strength development for a short time, a powder-type fast-hardening cement admixture containing calcium aluminate is preferable. These quick-hardening cement admixtures are added in an amount of 5 to 100 parts by mass with respect to 100 parts by mass of cement.

The calcium aluminates contained as an active ingredient of the rapid hardening cement admixture, if the CaO C, the _Al 2 _{O 3} A, the Na ₂ O N, the _Fe 2 _{O 3} were displayed at _{F, C} 3 A calcium displayed _{C 2 a, C 12 a 7} , C 5 a 3, CA, calcium aluminate having a mineral composition that appears when C 3 _{a 5} or CA _{2, etc.,} C 2 _AF, and _C 4 AF, etc. Aluminoferrite, calcium haloaluminate containing calcium fluoroaluminate, such as C ₃ A ₃ · CaF ₂ or C ₁₁ A7 · CaF _{2 in} which halogen is dissolved or substituted in calcium aluminate, C ₈ NA ₃ or C ₃ N ₂ calcium sodium aluminate which is displayed a _5, etc., calcium lithium aluminate, Auin _{(3CaO · 3Al 2 O 3 ·} Ca Calcium sulfoaluminate such as SO ₄ ), alumina cement, and those in which SiO ₂ , K ₂ O, Fe ₂ O ₃ , TiO _2, etc. are dissolved or combined are included. Particularly preferred are those containing calcium aluminate as an active ingredient. The calcium aluminate contained may be one kind or two or more kinds. Furthermore, from the viewpoint of stable strength development, a quick-hardening cement admixture in which calcium aluminates are combined with sulfates such as sodium sulfate, potassium sulfate, and calcium sulfate is preferable. The addition amount of the powder-type fast-hardening cement admixture containing calcium aluminate as an active ingredient is preferably 20 to 70 parts by mass with respect to 100 parts by mass of cement.

As an alternative to the cement and fast-curing cement admixture, super-fast-hardening cement such as “Jet Cement” (trade name) can also be used.

As the polymer for mixing with cement used in the present invention, any of polymers generally used for mixing with cement can be used. Preferred are vinyl acetate polymer, ethylene vinyl acetate polymer, vinyl acetate / versaic acid vinyl ester polymer, ethylene vinyl alcohol (EVA) polymer, vinyl acetate / vinyl versatate / acrylic acid ester polymer, and the like. These polymers may be either those usually marketed in the form of polymer dispersions or those marketed as re-emulsifying powder resins. Among these, styrene butadiene-based polymers are particularly preferable.

  The amount of the polymer (solid content of the polymer) is 4 to 14 parts by mass with respect to 100 parts by mass of the total amount of the cement and the quick-hardening cement admixture. By setting this amount, the amount of drying shrinkage due to the formation of the polymer film after curing is reduced without affecting the strength development. When the amount is less than 4 parts by mass, the amount of drying shrinkage strain increases. On the other hand, when the amount exceeds 14 parts by mass, strength development and durability are deteriorated. Preferably, it is 5-12 mass parts, More preferably, it is 7-11 mass parts.

  The setting retarder in the present invention has a retarding action on the setting of cement. The setting retarder may be either liquid or powder, but is preferably liquid. The reason why the setting retarder is liquid is preferable because the retarding effect can be obtained quickly. Examples of such liquid setting retarders include organic acids such as citric acid, gluconic acid, malic acid and tartaric acid, or salts thereof, boric acid such as boric acid and sodium borate, phosphate, sodium carbonate, carbonic acid. The liquid (for example, the form of aqueous solution, emulsion, suspension) which contains 1 type, or 2 or more types chosen from groups, such as inorganic salts, such as potassium, sodium bicarbonate, potassium bicarbonate, saccharides, is mentioned. Among them, when an aqueous solution containing one or more selected from the group of citric acid, citrate, tartaric acid, tartrate, and alkali metal carbonate is used, the usable life of the cement composite is long, and It is preferable because the initial strength expression is high.

The blending amount of the setting retarder is 0.05 to 2.0 mass with respect to 100 mass parts of the total amount of the cement and the quick-hardening cement admixture from the viewpoint of the pot life and initial strength development of the cement composite. Part is preferred. The pot life of the cement composite material is preferably secured for 20 minutes or more. More preferably, it is 30 minutes or more, More preferably, it is 60 minutes or more. The pot life is set and the blending amount of the setting retarder is determined so as to ensure proper workability in consideration of the temperature and the construction situation at the placement site.

The lightweight aggregate used in the present invention has an absolutely dry density of 1.0 to 2.3 g / cm ³ . By using a lightweight aggregate in this range, a cement composite that satisfies the light weight and the initial compressive strength can be obtained. As the above-mentioned lightweight aggregate, either coarse aggregate, fine aggregate, or both can be used. More specifically, it is preferable to use a lightweight aggregate having an absolutely dry density of 1.0 to 2.0 g / cm ³ as at least the coarse aggregate. Further, as the fine aggregate, it is preferable to use a lightweight aggregate having an absolutely dry density of 1.5 to 2.3 g / cm ³ , and it is particularly preferable to use these in combination. Absolute dry density of coarse aggregate is more preferably 1.0 to 1.5 g / cm ^3, more preferably 1.1~1.4g / cm ^3, particularly preferably 1.2 to 1.3 g / cm ³ . Absolute dry density is more preferably 1.5 to 2.0 g / cm ³ of fine aggregate, more preferably ^{1.6~1.8g / cm 3, 1.63~1.73g / cm} 3 is particularly preferred.

The blending amount of the lightweight aggregate is preferably 200 to 1600 kg / m ³ from the viewpoint of light weight and initial compressive strength. More preferably 400~1400kg / ^{m 3,} more preferably 450~1000kg / ^{m 3.}

The water used in the present invention is not particularly limited, and tap water or the like can be used. The blending amount of water (unit water amount) is preferably 70 to 150 kg / m ³ from the viewpoint of fresh concrete properties, initial strength development, and drying shrinkage. Moreover, it is preferable that the compounding quantity of water shall be 15-30 mass parts with respect to 100 mass parts of total amounts of the said cement and a quick-hardening cement admixture.

In the cement composite material of the present invention, various additives may be used in combination as components other than those described above as long as the features of the present invention are not impaired. Examples of this type of additive include water reducing agents, AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, cement dispersants such as fluidizing agents, foaming agents, foaming agents, waterproofing agents, rust preventive agents, Examples include shrinkage reducing agents, thickeners, water retention agents, pigments, water repellents, anti-whitening agents, antifoaming agents, fine powder of blast furnace slag, fly ash, stone powder, silica fume, and volcanic ash.

The method for kneading the cement composite is not particularly limited, but a method using a mixer is preferable from the viewpoint of production amount and homogeneous kneadability. As the mixer, a continuous mixer or a batch mixer is used. For example, a bread type concrete mixer, a pug mill type concrete mixer, a gravity concrete mixer, etc. are mentioned. The kneading time is preferably 120 seconds to 360 seconds.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these at all.

<Materials used>
(1) Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement, density: 3.16 g / cm ³ )
(2) Quick-hardening cement admixture: Calcium aluminate rapid hardening material (including calcium aluminate and sulfate; density: 2.93 g / cm ³ )
(3) Cement admixture polymer: Styrene butadiene polymer (solid content 45%, density; 1.00 g / cm ³ )
(4) Setting retarder: citrate retarder, added as aqueous solution (5) Lightweight aggregate: a) Artificial lightweight fine aggregate (absolute dry density 1.68 g / cm ³ )
b) Artificial lightweight coarse aggregate (absolute dry density of 1.25 g / cm ³ )
(6) Normal aggregate: a) Mountain sand from Kakegawa, Shizuoka Prefecture (absolute dryness 2.51 g / cm ³ )
b) Crushed stone from Sakuragawa, Ibaraki Prefecture (absolute dryness 2.61 g / cm ³ )
(7) Water: Tap water

Using the above materials, an evaluation test was performed in a 20 ° C. environment. Table 1 shows the concrete composition at that time. The unit is kg / m ³ . The amount of setting retarder added was 0.5 parts by mass (in terms of solid content) with respect to 100 parts by mass of the total amount of cement and quick-hardening cement admixture.

<Evaluation test>
(1) Compressive strength The compressive strength was measured in accordance with JIS A 1108, and the strength of a concrete specimen was measured at a material age of 6 hours in a 20 ° C environment.
(2) Drying shrinkage strain Drying shrinkage strain was measured in accordance with JIS A 1129 and measured until the age of 182 days.

<Test results>
The test results are shown in Table 2. The amount of polymer is a solid content equivalent of the polymer with respect to 100 parts by mass of the total amount of cement and fast-curing cement admixture. In the case where the polymer amount is within a predetermined range and light concrete type I is blended (Examples 1 to 4), the compressive strength is 24 N / mm ² or more at a material age of 6 hours and the dry shrinkage strain at a material age of 182 days is a polymer. Increased proportionately. A more remarkable result was obtained in the case of blending lightweight concrete type II (Example 5). On the other hand, the compression strength at the age of 6 hours does not reach 24 N / mm ² at the level (comparative examples 1 to 5) in which at least one of the blends that are usually used with the aggregate and the blend of the polymer amount outside the predetermined range is combined. Or the drying shrinkage | contraction strain | stump | stock of the age of 182 days became large compared with the Example.

Claims (3)

A cement, a fast-hardening cement admixture, a cement admixture polymer, a setting retarder, and a lightweight aggregate having an absolutely dry density of 1.0 to 2.3 g / cm ³ ; Cement composite material characterized by being 4 to 14 parts by mass with respect to 100 parts by mass of the total amount of the hard cement admixture. The cement composite according to claim 1, wherein the lightweight aggregate is a coarse aggregate having an absolutely dry density of 1.0 to 2.0 g / cm ³ . The cement composite according to claim 2, further comprising a fine aggregate having an absolutely dry density of 1.5 to 2.3 g / cm ³ .