WO2006134670A1

WO2006134670A1 - Cement admixture and cement composition

Info

Publication number: WO2006134670A1
Application number: PCT/JP2005/011203
Authority: WO
Inventors: Yoshiharu Watanabe; Kazuhiro Aizawa
Original assignee: Denki Kagaku Kogyo Kabushiki Kaisha
Priority date: 2005-06-14
Filing date: 2005-06-14
Publication date: 2006-12-21
Also published as: WO2006134711A1; MY163157A; CN101198562A; TW200710061A; CN101198562B; KR20080025680A; TWI403484B; KR100947808B1

Abstract

This invention provides a cement admixture, which, without limiting the kind of a water reducing agent, can improve a false setting property attributable to a high dissolution rate of natural anhydrous gypsum and can stably ensure high-strength developing properties, and a cement composition using the admixture. The cement admixture is characterized by comprising a natural anhydrous gypsum which, when 1 g of a natural anhydrous gypsum is brought into contact with 100 g of a 0.05% aqueous Na2HPO4 solution of 20ºC for one hr, the dissolution rate is 4 to 30% by mass/hr in terms of the concentration of SO4 ion in the aqueous solution. There is also provided a cement admixture composed mainly of a natural anhydrous gypsum and at least one member selected from fired clay minerals, clay minerals, fly ash, slaked lime, and quick lime and characterized in that, when 1 g of the natural anhydrous gypsum in the cement admixture is brought into contact with 100 g of a 0.05% aqueous Na2HPO4 solution of 20ºC for one hr, the dissolution rate is 2.7 to 30% by mass/hr in terms of the concentration of SO4 ion in the aqueous solution. The cement composition is characterized by comprising the above cement admixture added to cement.

Description

Cement admixture and cement soot composition Technical Field

The present invention relates to a cement admixture and a cement composition, and more particularly, to a cement admixture mainly composed of natural anhydrous gypsum with a defined dissolution rate and a cement composition using the admixture. Background art

Anhydrite is widely used as an admixture for atmospheric steam curing. Anhydrous gypsum varies greatly depending on its heat treatment conditions and formation process, and natural anhydrous gypsum, depending on the production area.

It is also known that the rate of dissolution of anhydrous gypsum as a high-strength admixture for atmospheric steam curing is better.

Focusing on these properties, when 100 g of 0.05% Na2HPO ₄ aqueous solution is contacted with 1 g of hydrofluoric acid-generated by-product anhydrous gypsum for 1 hour, the S0 ₄ ion concentration in the aqueous solution is 0.02 to 0.14%. A method for producing a high-strength concrete or mortar member using this has been proposed (see Patent Document 1).

Patent Document 1: Japanese Patent No. 1 2 2 1 2 8 1

In addition, natural anhydrous gypsum has a high dissolution rate, so there are inconveniences such as false coagulation when it is used in combination with naphthenic or melamine high-performance water reducing agents used in the production of high-strength concrete. Using natural anhydrous gypsum from Thailand, when 100 g of 0.05% Na2HPO ₄ aqueous solution was contacted with 1 g of natural anhydrous gypsum for 1 hour, the dissolved amount of S04 ion concentration in the aqueous solution was 0.15 to 1.5% by mass. There has also been proposed a concrete in which what is shown is blended together with a polycarboxylate-based water reducing agent having a setting delay, and a method for producing a high-strength concrete molded body using the same (see Patent Document 2). 'Patent Literature 2: Patent No. 3 3 4 3 1 6 3 Furthermore, in order to further increase the strength of the concrete clay cured by hydrostatic acid-generated by-product anhydrous gypsum and hydrofluoric acid-generated by-product anhydrous gypsum, silica flour (silica fume), silicate white clay, fly ash, etc. A cement admixture has also been proposed (see Patent Document 3).

Patent Document 3: Japanese Patent No. 1 2 3 4 4 4 8

However, hydrofluoric acid-generated by-product anhydrous gypsum was found to be the cause of chlorofluorocarbon gas breaking down the ozone layer, and an alternative technology was developed to suppress the production of hydrofluoric acid and produce by-product hydrofluoric acid by-product. There is a problem that the amount of raw anhydrous gypsum is drastically decreasing, making it difficult to use.

In addition, natural anhydrite basically has a high dissolution rate, and the dissolution rate varies depending on the origin, the depth of the veins, and the impurities contained, and the solubility varies greatly depending on the powder conditions, ensuring stable high strength performance. It is a problem that is difficult to achieve, and it is not shown by the strength development performance at a lower level than hydrous acid generation by-product anhydrous gypsum. In addition, the dissolution rate and reactivity differ depending on the temperature, so even if used in combination with a polystrength sulfonated water reducing agent, there are problems such as the occurrence of false coagulation and sudden slump loss depending on the type and amount of addition. Is inherent.

In addition, in the case of cement-mixed materials containing silica fume, silicate white clay, fly ash, etc., normal pressure such as silica fume, silicate white clay, fly ash, etc. is used for use with hydrofluoric acid by-product anhydrous gypsum which originally has a low dissolution rate. It expects a pozzolanic reaction by steam curing, and does not include the inventive idea of increasing the strength with anhydrous gypsum by controlling the dissolution rate of natural anhydrous gypsum with a high dissolution rate like the present invention, The effect is not shown either. Disclosure of the invention

Problems to be solved by the invention

The present invention is a cement admixture that can improve the pseudo-caking property due to the high dissolution rate of natural anhydrous gypsum without limiting the type of water reducing agent, and can stably ensure high strength development performance. And to provide a cement composition using the admixture. Means for solving the problem

In order to solve the above problems, the present invention employs the following means.

(1) When a 20 0.05% Na 2 HPO ₄ natural anhydrite of lg relative solution 100g of was come in contact for one hour, natural is S0 ₄ ion concentration in the aqueous solution shows the dissolution rate of 4-30 mass% Z hr A cement admixture characterized by containing anhydrous gypsum.

(2) In a cement admixture mainly composed of one or more selected from natural anhydrous gypsum and calcined clay minerals, clay minerals, fly ash, slaked lime, and quick lime, the natural anhydrous gypsum is 0.05 at 20 ° C. When lg natural anhydrous gypsum in the cement admixture is brought into contact with 100 g of% 水溶液 θ2Ν ₄ aqueous solution for 1 hour, the S0 ₄ ion concentration in the aqueous solution shows a dissolution rate of 2.7 to 30 mass% Z hr. It is a cement admixture characterized by being.

(3) The cement admixture according to (2) above, which contains a combination of one or more selected from calcined clay minerals, clay minerals, and fly ash and slaked lime and / or quicklime.

(4) calcined clay minerals. The cement admixture according to (2) or (3) above, which contains at least 80% by mass of one or more selected from clay minerals, fly ash, slaked lime, and quicklime.

(5) A cement composition, wherein the cement admixture according to any one of (1) to (4) is added to cement.

(6) The cement composition according to (5), wherein 15 parts by mass or less of the cement admixture is added to 100 parts by mass of cement in terms of natural anhydrous gypsum. The invention's effect

By using the cement admixture of the present invention, high strength can be easily obtained especially by steam curing, so that high-strength concrete piles, poles, propulsion pipes and other concrete products can be manufactured. Since strong strength can be obtained regardless of pre-tension method or post-tension method, large pre-stress can be introduced, so earthquake resistance can provide high toughness, and steam-curing can be achieved with a single atmospheric steam curing. The strength is the same as when combined with autoclave curing at atmospheric pressure and 180 ° C, so it is economical and reduces the burden on the environment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

In addition, the part and% which show the mixture ratio and addition amount which are used by this invention are a mass unit. The anhydrous gypsum used in the present invention is natural anhydrous gypsum. When 100 g of O.OS ^ Na ^ O aqueous solution at 20 g was contacted for 1 hour with stirring to such an extent that lg natural anhydrous gypsum did not precipitate, S0 ₄ ion concentration in the aqueous solution are those shows the dissolution rate of 4-30 mass% Z hr. When the dissolution rate exceeds 30% by mass Zhr, it is not preferable because the concrete kneading temperature exhibits pseudo-coagulation even at a temperature of 10 ° C or less, and the high strength development performance is reduced. If the dissolution rate is less than 4% by mass Zhr, false coagulation is not shown even if the temperature is high, but the degree of fineness becomes too small and unreacted natural anhydrous gypsum remains, resulting in a decrease in high strength development performance. It is. A preferable dissolution rate is 4 to 20% by mass. In addition, as shown in the examples described later, since the dissolution rate of natural anhydrous gypsum decreases when natural anhydrous gypsum is blended with natural anhydrous gypsum, in that case, in the admixture containing the calcined clay mineral etc. when the natural anhydrite of lg 1-hour contact against 0.05% Na2HP (¾ aqueous solution 100 _g of 20, natural anhydrous the SO ion concentration in the aqueous solution shows the dissolution rate of 2.7 to 30 wt% Z hr It is preferable to use gypsum.

Incidentally, method of quantifying s ions, a sample was taken as CAS0 ₄ natural anhydrite in the cement admixture is lg, after the dissolution operation, suction filtered have use a No.5A filter paper, Dilute the filtrate to 200 ml with pure water. Cover with a watch glass and bring to a boil. Excessively added dropwise to cause boiling is continued for 30 minutes while precipitating as BaS0 ₄ by stirring the aqueous solution of barium chloride (lOOg / 1). Then, after aging for 3 hours, filter with No. 6A filter paper, wash with warm water 8-10 times, put the filter paper into a ruppo with known weight, heat at 1000 for 30 minutes in an electric furnace, cool and weight Measure. SO * ion Dissolution amount is calculated as = ignition residue (g) x 0.411 x 100 (%).

The present inventor has found that calcined clay minerals, clay minerals, and fly ash have no strength enhancement effect due to their own pozzolanic activity, but they suppress the dissolution rate of natural anhydrous gypsum. It has been found that a high strength is obtained as a result. In the case of slaked lime and quicklime, the effect of suppressing the dissolution rate of natural anhydrous gypsum was recognized, and as a result, it was found that high strength was obtained. In addition, it has been found that when one or more kinds selected from calcined clay minerals, clay minerals, and fly ash are used in combination with slaked lime and Z or quick lime, the dissolution rate is further suppressed and higher strength is obtained. Is more preferable.

The calcined clay mineral of the present invention is an earthy clay mainly composed of aluminosilicates such as acid clay, activated clay (acid-treated acid clay), bentonite, kaolinite, chlorite, sericite, and rhodolite. Clay minerals are aluminosilicates such as acid clay, activated clay (acid clay treated with acid), bentonite, kaolinite, chlorite, sericite, and rhodolite. It is a soil-like mixture containing as a main component. Fly ash is collected from the flue of the pulverized coal fired thermal power plant and contains a large amount of silicic acid and alumina.

The amount of one or more admixture components selected from calcined clay minerals, clay minerals, fly ash, slaked lime, and quick lime is preferably 80 parts or less in a total of 100 parts of natural anhydrous gypsum and these admixture components, 10 to 70 parts are more preferred. Even if it exceeds 80 parts, the effect of suppressing the dissolution rate of natural anhydrous gypsum reaches its peak, and the high strength development performance may not change, and in addition, the blending ratio of natural anhydrous gypsum decreases, so that the same strength In order to achieve this, the amount of cement admixture added to the cement increases, which is economically undesirable.

When natural anhydrous gypsum and one or more selected from calcined clay minerals, clay minerals, and fly ash are combined with slaked lime and Z or quick lime, 40-80 parts of natural anhydrous gypsum, calcined clay minerals, clay minerals, and It is preferable that at least one selected from fly ash is 30 to 10 parts, and slaked lime and Z or quick lime is 30 to 10 parts.

The amount of the cement admixture of the present invention is preferably 15 parts or less, more preferably 2 to 10 parts in terms of natural anhydrous gypsum, with respect to 100 parts of cement. Even if it exceeds 15 parts, the strength effect may reach its peak.

The curing method may be a conventional method and is not particularly limited. In this case, it is preferable to hold at the maximum temperature of 40 to 90 ° C for 4 to 6 hours, and the time from the start of steam curing to the stop of steam curing is preferably 5 to 10 hours.

In the present invention, a necessary amount of a high-performance water reducing agent or a high-performance AE water reducing agent is used in combination.

What is marketed as a high-performance water reducing agent is mainly composed of any one of polyalkylarylsulfonate, aromatic aminosulfonate, and melamine formalin resin sulfonate. One or more of them are used.

Polyalkylaryl sulfonate-based high-performance water reducing agents include methylnaphthalene sulfonic acid formalin condensate, naphthalene sulfonic acid formalin condensate, anthracene sulfonic acid formalin condensate and so on. , Setting delay is a small water reducing agent.

The amount of the above-mentioned high-performance water reducing agent added is preferably 4% by mass or less, more preferably 1.0 to 3.0% by mass with respect to cement in the form of a commercial product.

Commercially available products of high-performance AE water reducing agents include improved types of high-performance water reducing agents, which can also be used, but as commonly called polycarboxylate-based water reducing agents, unsaturated power ruponic acid A copolymer containing a monomer as a component or a salt thereof, such as a polyalkylene glycol monoacrylate, a polyalkylene glycol monomethacrylate, a maleic anhydride and a styrene. Salt copolymers and copolymers derived from monomers copolymerizable with these monomers are the mainstream, and the water reduction rate is large with less addition than the high-performance water reducing agent system. In addition, it has air entrainment properties and large delay in setting and curing, but it has the property of having slump retention.

The amount of the high-performance AE water reducing agent added as described above is preferably 4% by mass or less, more preferably 0.7 to 3.0% by mass, based on cement in the form of a commercial product.

The cement used in the present invention is usually a mixture of various Portland cements such as early strong, moderately hot, low heat, sulfate resistance, white, or a mixture of blast furnace slag and fly ash. Ordinary, early strong, moderately hot, low heat, sulfate resistant, white cement, cement mixed with mixed cement, or cement with blast furnace slag or fly ash mixed with early strong poled land cement. Yo Yes.

The method for adding the admixture of the present invention is not particularly limited. When kneading mortar or concrete, a mixture of natural anhydrous gypsum or natural anhydrous gypsum and calcined clay mineral, etc., and a mixture of powdered and mixed powder may be added together with other mortar or concrete materials. These components may be added separately. In addition, a cement composition may be added.

The mixing method does not require a special method, and a conventional mixing method is sufficient.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not restricted to these. The materials, test items and methods used in the examples of the present invention are summarized below. Materials Used>

Cement: Ordinary Portland cement

Sand: River sand from Himekawa, Niigata (5mm below)

Meteorite: Meteorite from Himekawa, Niigata Prefecture (13-5mm)

Water reducing agent: Polyalkylaryl sulfonate high-performance water reducing agent (liquid)

Natural anhydrous gypsum: Coarse under 5 mm, CaS0 ₄ purity 98%

Calcinated clay mineral A: Clay mineral, acid clay ground product, Blaine specific surface area 7520cm ² / _g . Calcinated clay mineral B: baked clay mineral, activated clay after cooking edible oil is baked at 800 ° C Powdered rice cake, Blaine specific surface area 5510cm ² / g

Calcined clay minerals C: Fly ash, further mixed with cement admixture produced as a by-product in coal-fired thermal power plant, Blaine specific surface area 5060cm ² / g

Calcined clay minerals D: quick lime, gas baked quick lime, purity 99%, ground product, Blaine specific surface area 8550cm ² / g

Calcined clay mineral E: Slaked lime, calcined clay mineral D digested and powdered, brain specific surface area 10000cm ² / g or more

Test Items and Methods>

(1) Method for adjusting the dissolution rate of natural anhydrous gypsum

Natural anhydrous gypsum was adjusted by adjusting the powder level while changing the feed amount with a vibratory mill with two cylinders (inner diameter of 15 cm). In addition, when blending calcined clay minerals, etc., Combined.

(2) Measurement of Blaine specific surface area

According to JIS R 5201.

(3) Measurement of compressive strength

Conforms to JIS A 1132, HS A 1108. For concrete mixing, cement, cement admixture, fine aggregate, and coarse aggregate are kneaded for 20 seconds, then mixed with water-reducing agent dissolved in water and mixed for 3 minutes. Kneaded with a kneading mixer. Example 1

Table 1 shows the physical properties such as the dissolution rate of cement admixtures based on the natural anhydrous gypsum of the present invention that has been pulverized.

table 1

Using a cement admixture with adjusted dissolution rate of only natural anhydrous gypsum in Table 1, the concrete was mixed at 10 or less to reduce false setting. The basic composition of concrete is: unit cement amount 450 kg / m ³ , water amount 130 kg m ³ , fine aggregate amount 710 kg m ³ , coarse aggregate amount 1150 kg / m ³ , water reducing agent amount 9 kg / m ³ (internal allocation to water) a Caro), cement admixture to 31.5 kg m ³ (7 parts by weight per 100 parts by weight cement) replaced with fine aggregate to prepare a concrete slump 1 ~ 8 cm, were molded specimen. Pre-mold the molded specimen until it hardens to the beginning of condensation at a room temperature of 10, then raise it to 65 at a heating rate of 20 X / bi, hold it for 4 hours, and then stop the steam valve until the next day Table 2 shows the results of gradual cooling in a steam curing tank and measuring the compressive strength of the material one day. Table 2

(註) *: Concrete has a false setting

Table 2 shows that even if the natural anhydrous gypsum has a large plain specific surface area and a high dissolution rate, and even if the plain specific surface area is small and the dissolution rate is slow, the high strength development performance is lost.

And, the dissolution rate is 4 to 30% by mass hr, and the strength enhancement effect is recognized, and it is preferably 4 to 20% by mass / hr. It was also found that when the dissolution rate exceeds 30% by mass hr, pseudo-condensation was exhibited even at low temperatures, resulting in poor workability. Example 2

Table 3 shows the dissolution rate of the cement admixture obtained by mixing the cement admixture in Table 1 with 70:30 parts by mass of calcined clay. Table 3 shows that the dissolution rate of natural anhydrous gypsum decreases when calcined clay minerals are added.

Table 3

Concrete was kneaded at 20 using the cement admixture from Table 3. The basic composition of Concret-Koji is the same as in Example 1, and the cement admixture is added by replacing 45 kg m ³ with fine aggregate so that the amount of natural anhydrous gypsum is constant at 31.5 kg / m ^3. A similar test was conducted. In addition, the pre-curing was set at 20 t, and for comparison, concrete containing 13.5 kg m ³ alone of calcined clay was also added. The results are shown in Table 4.

Table 4

(註) *: Concrete has a false setting

From Table 4, it can be seen that even when the calcined clay mineral powder is added, the high strength development performance is lost whether the dissolution rate is fast or slow. In particular, even if the dissolution rate is as low as 1.0% by mass / hr, if the natural anhydrous gypsum powder is small, the reaction amount will be smaller and the effect of strength enhancement will not be observed (Experiment No. 2-10). ). In addition, the strength enhancement effect of calcined clay mineral alone (only B) is slight (comparison between Experiment No.2-1 and Experiment No.2_2), but when used in combination with natural anhydrous gypsum, the degree of fineness and dissolution rate are moderate. If this is the case, a synergistic strength increase will be shown (for example, Experiment Νο.14, Νο.1-5, Νο.1-7 and Experiment Νο.2-5, Νο.2 · 6, Νο.2 ~ 8 comparison). It was also found that when the dissolution rate exceeded 30% by mass / hr, false coagulation was exhibited even if calcined clay minerals were included, and workability deteriorated. Example 3

Table 5 shows cement admixtures in which the dissolution rate was adjusted by mixing calcined clay, etc., in the sample No. 4 in Table 1 at an arbitrary ratio. The dissolution rate of natural anhydrous gypsum is Table 5 shows that the higher the blended amount of baked clay, etc.

Using a cement admixture in Table 5, the concrete was kneaded at 20. The basic composition of Concret-Koji was the same as in Example 1, and the cement admixture was added at an arbitrary ratio to 100 parts by mass of cement, replacing with fine aggregate, and the same test as in Example 1 was conducted (伹And the pre-curing is 20). The results are shown in Table 6.

Table 6

Experiment Sample No. and blending amount Kneaded Compressive strength

o. (kg m ³ ) Temperature (in) (N / mm ² ) Remarks

3-12 No27 35.0 (7.0) 20 76.3 Invention example

3-13 No.28 39.4 (7.0) 23 79.1 Invention example

3-14 No 9 48.5 (7.0) 20 80.0 Invention example

3-15 No30 63.0 (7.0) 21 80.4 Invention example

3-16 No31 78.8 (7.0) 22 81.6 Invention example

3-17 No32 105.0 (7.0) 23 80 Invention example

3-18 No additive 20 60.9 Comparative example

3-19 No.22 9 (1.0) 20 62.0 Reference example

3-20 22ο 22 18 (2.0) 20 65.7 Invention example

3-21 No.22 36 (4.0) 20 73 Invention example

3-22 22ο 22 72 (8.0) 21 79.8 Invention example

3-23 Νο 22 90 (10.0) 21 81.9 Invention example

3-24 No.22 135 (15.0) 22 83.0 Invention example

3-25 No.22 153 (17.0) 23 83.5 Invention example

3-26 No.30 18 (2.0) 20 66.8 Invention example

3-27 No 0 36 (4.0) 20 75.7 Invention example

3-28 No.30 72 (8.0) 20 83.8 Invention example

3-29 No 0 90 (10.0) 21 85.0 Invention example

Figures in parentheses are parts by weight of natural anhydrous gypsum relative to 100 parts by weight of cement.

From Table 6, when the admixture of the present invention was added so that the amount of natural anhydrous gypsum equivalent to 100 parts by mass of cement was constant at 7 masses (Experiment No.3-1 to No.3-17), In the clay clay minerals, clay minerals, and fly ash, the components of clay clay minerals are low in pozzolanic activity, and the strength-increasing effect due to the bozolan reaction is not observed in short-term ages. Indicates high strength.

And when the ratio of natural anhydrous gypsum to calcined clay mineral is 30 Z 70 and 20/80, the strength reaches its peak, so even if natural anhydrous gypsum is less than 20 parts by mass, no increase in strength can be expected (Experiment No. 3 -10 to No.3-ll). In addition, the ratio of natural anhydrous gypsum and calcined clay minerals shows a strength effect from 95 Z 5, but as the ratio of calcined clay minerals increases, the strength gradually increases and becomes remarkable from 90/10 (Experiment No.3-1 to No.3-10). Therefore, the blending ratio of the natural anhydrous gypsum Z calcined clay mineral of the present invention is 95 Z 5-20 / 80, more preferably 90 Z 10-30 Z 70.

If the component in the calcined clay mineral is quick lime or slaked lime (Experiment No.3- 12 ~ No. 3-17) shows a tendency for strength to be higher than that of calcined clay minerals due to the effect of accelerated setting of cement by quick lime and slaked lime and the effect of increasing hydration.

Natural anhydrous gypsum Z The ratio of natural anhydrous gypsum added to cementite is changed to 50/50 at a constant ratio of calcined clay mineral (Experiment No.3-19 to No.3-25). The improvement is noticeable at 2% by mass or more, but even if added over 10 to 15% by mass, the strength reaches its peak, and if it is less than 1% by mass, the strength enhancement effect is expected to be small. Therefore, the addition amount of the cement admixture of the present invention is 15% by mass or less in terms of natural anhydrous gypsum, and preferably 2 to 10% by mass. Example 4

Table 7 shows the dissolution rates of two or more types of calcined clay mixed with cement admixture sample No. 5 in Table 1. Also in this case, it is shown that the dissolution rate of natural anhydrous gypsum decreases as the blending ratio of baked clay increases.

Table 7-

Concrete was mixed at 30 using the cement admixtures in Table 7. The basic composition of the concrete was the same as in Example 1, and the cement admixture was 45 kg m ³ -the same amount as in Example: L was added, replacing the fixed amount with fine aggregate. 30). The results are shown in Table 8. Table 8

From Table 8, when the admixture of the present invention is added to 10 parts by mass with respect to 100 parts by mass of cement, the dissolution rate of natural anhydrous gypsum decreases as the blending ratio of calcined clay minerals increases. Therefore, the higher the blending ratio, the higher the strength, but even if it is too much, the strength tends to decrease when the absolute amount of natural anhydrous gypsum decreases. When the ratio of clay minerals is in the range of 80 Z 20-40 / 60, the strength enhancement effect is remarkably shown (Experiment No.4-11). Example 5

A test similar to Example 4 was performed using the cement admixture of Table 7. However, the type of water reducing agent was changed from the polyalkylaryl sulfonate water reducing agent, which is a high performance water reducing agent, to the polycarboxylate water reducing agent, which is a high performance AE water reducing agent, and the amount added was 5.85. kg m ³ (slump of 1 to 8 cm is obtained with this addition amount). The results are shown in Table 9. Table 9

Table 9 shows that even when polycarboxylate-based water reducing agents are used, the same strength is obtained as when polyalkylaryl sulfonate-based water reducing agents are used, and the higher the content of baked clay minerals, the higher the strength. As shown, the strength tends to decrease when the absolute amount of natural anhydrous gypsum decreases even if the amount is too much, and the ratio of natural hydrous gypsum Z calcined clay mineral, etc. A strength increase effect is shown in the range of 60 (Experiment No. 5-4 to No. 5-11). Industrial applicability

The present invention is a cement admixture mainly composed of natural anhydrous gypsum whose dissolution rate is defined as described above, or the natural anhydrous gypsum and calcined clay mineral, viscosity; fc mineral, fly ash, slaked lime, and quick lime. It is a cement admixture containing one or more of the above, and it is a cement composition that can achieve high strength using these admixtures, so it is possible to increase the strength of civil engineering structures, concrete piles, poles, fume Used for pipes and other concrete products produced by steam curing.

Claims

The scope of the claims

1.20. When an lg of natural anhydrous gypsum is in contact with 100 g of 0.05% Na2HPO ₄ aqueous solution for 1 hour, the natural anhydrous gypsum shows a dissolution rate of 4 to 30% by mass of S0 ₄ ion concentration in the aqueous solution. A cement admixture characterized by containing.

2. A cement admixture mainly composed of one or more selected from natural anhydrous gypsum and calcined clay minerals, clay minerals, fly ash, slaked lime, and quick lime, wherein the natural anhydrous gypsum is a 0.05% Na2HPO ₄ aqueous solution at 20. when the natural anhydrite of lg in the cement admixture relative to 100g 1-hour contact, wherein a is S0 ₄ ion concentration in the aqueous solution shows a dissolution rate of 2.7 to 30 wt% / hr Cement-mixed material.

3. The cement admixture according to claim 2, containing at least one selected from calcined clay minerals, clay minerals, and fly ash and slaked ash and / or quicklime.

4. The cement admixture according to claim 2 or 3, characterized by containing at least 80% by mass of one or more selected from calcined clay minerals, clay minerals, fly ash, slaked lime, and quick lime. .

5. A cement composition, wherein the cement admixture according to any one of claims 1 to 4 is added to the cement.

6. The cement composition according to claim 5, wherein 15 parts by mass or less of the cement admixture in terms of natural anhydrous gypsum is added to 100 parts by mass of cement.