JPH10265249A - Cement admixture and cement composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress cracking by using a high performance water-reducing agent, one or more selected from among an alkali metallic sulfite, an alkali metallic hydrogensufite, an alkali metallic pyrosulfate, an alkali metallic pyrosulfite and calcium sulfite, and gypsum. SOLUTION: This cement admixture contains a high performance water- reducing agent contg. one or more selected from among a polyalkylallylsulfonate polymer, melamine-formaldehyde resin, a sulfonate polymer and an arom. aminosulfonate polymer, one or more selected from among an alkali metallic sulfite, an alkali metallic hydrogensulfite, an alkali metallic pyrosulfate, an alkali metallic pyrosulfite and calcium sulfite, and gypsum. The water-reducing agent, the sulfite, etc., and gypsum are added to 100 pts.wt. cement by 0.4-3.0 pts.wt. (expressed in terms of solid), 0.05-2.0 pts.wt. (expressed in terms of anhydride) and 1-15 pts.wt. (expressed in terms of CaSO4 ), respectively. It is preferable that 1-15 pts.wt. activated silica and/or 2-15 pts.wt. pozzolan material is further added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture for mortar and concrete used in civil engineering and building structures and secondary concrete products, and a cement composition using the same. More specifically, the present invention relates to a cement admixture which improves a mortar flow or a concrete slump with time when a high-performance water reducing agent is used, and further improves strength and durability, and a cement composition using the same. .

[0002]

2. Description of the Related Art Conventionally, high-performance water reducing agents such as polyalkylallyl sulfonate, melamine formalin resin sulfonate, and aromatic amino sulfonate polymer have been used as lignin sulfonate or polyol type. Water reducing agent,
Compared with general water reducers such as oxycarboxylate-based water reducers, etc., the water reduction rate is large, and even if added in a relatively large amount, it does not cause abnormal setting or excessive delay of the cement and has low air entrainment It is suitable for the production of high-strength concrete for civil engineering and building structures and the production of high-strength concrete products.

[0003] However, these high-performance water reducing agents have a large amount of slump deterioration with time, and provide a stable slump concrete when the concrete is kneaded and mixed by a ready-mixed plant and transported and poured by an agitator vehicle in the field construction. However, in extreme cases, the amount of slump declined over time was too large to make it impossible to discharge from the agitator vehicle. In a concrete product factory, the time required for work is relatively 30 hours.
It is often used in the manufacture of high-strength concrete products even if the amount of slump declines over time because it is short, not more than about a minute.However, if the process takes a long time to process due to troubles, it must be discarded. There were problems such as not becoming.

[0004] Basically, concrete has a higher elastic modulus with a higher strength, and therefore has a daily difference in temperature (which may be 80 ° C or higher during the daytime in summer and 30 ° C or lower at nighttime) or a wet / dry condition. There is also a problem that cracks are likely to occur when subjected to repeated stress of expansion and contraction (weather resistance).

The inventor of the present invention has proposed a method for producing a high-strength concrete in which the amount of slump of concrete to which a high-performance water reducing agent has been added has been reduced over time and cracks have been improved when exposed and cured outdoors. (Japanese Patent Publication No. 1-53225). A method was proposed in which a silica powder (silica fume, blast furnace slag, fly ash, activated clay, diatomaceous earth, opal silica, etc.) was used in combination with the carbonate and type II anhydrous gypsum. However, in this proposal, since a strong delay component such as citrate is included as a method of improving the amount of aging such as slump, the setting hardening is slow in winter construction, and depending on the outside air temperature, the hardening is 2-3 times.
In addition to the fact that it takes days, the construction is delayed, and the time until the start of setting is prolonged. During this time, there is a problem that water evaporates from the concrete surface and cracks due to plytic shrinkage occur frequently.

The present inventor has set out the following in order to solve the above problems.
That is, while improving so as to reduce the amount of concrete slump with time, the expression of the initial strength is improved, and the occurrence of cracks when subjected to repeated stress of expansion and contraction due to daily temperature differences and dry and wet, Furthermore, as a result of earnest research from a comprehensive point of view, such as reducing the occurrence of cracks when receiving repeated stress and salt damage at the same time,
The inventors have found that the problem can be solved by using a specific material, and have completed the present invention.

[0007]

That is, the present invention provides:
(1) A high-performance water reducing agent and one of alkali metal sulfites, alkali metal bisulfites, alkali metal pyrosulfites, alkali metal pyrosulfites and calcium sulfites
A cement admixture characterized by containing a seed or two or more and gypsum; (2) a cement admixture according to (1), further comprising an activated silica and / or a pozzolanic substance; (3) For 100 parts by weight of cement,
0.4 to 3.0 parts by weight of a high-performance water reducing agent in terms of solid content, alkali metal sulfite, alkali metal bisulfite, alkali metal pyrosulfate, alkali metal pyrosulfite, and calcium sulfite One or two or more
5 to 2.0 parts by weight, and plasters in the range of 1 to 1 in terms of CaSO ₄
5 parts by weight of a cement composition,
(4) Further, based on 100 parts by weight of cement, 1 to 15 parts by weight of active silica and / or 2-1 to
The cement composition according to (3), which contains 5 parts by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Examples of the high-performance water reducing agent used in the present invention include those containing, as a main component, any one of a polyalkylallyl sulfonate type, a melamine formalin resin sulfonate type, and an aromatic amino sulfonate type polymer. And although there is also a mixed type of these, these may be used as a single item, and furthermore, these two or more types may be arbitrarily mixed and used. As examples of some of the high performance water reducing agents that are generally commercially available, polyalkylallyl sulfonate-based high performance water reducing agents include methyl naphthalene sulfonic acid formalin condensate, naphthalene sulfonic acid formalin condensate, and anthracene Salts such as sulfonic acid formalin condensate and the like, and commercially available products thereof include "F
T-500 ", Kao Corporation brand name" Mighty 100 ",
"Mighty 150" series, etc., Daiichi Kogyo Seiyaku Co., Ltd. brand name "Cell Flow 110P", etc., Takemoto Yushi Corporation brand name "Pole Fine 510N", etc., and Nippon Paper Industries brand names "Sunflow PS", "Sun Flow HS700 "
Etc. are typical. As the aromatic aminosulfonate salt, Fujisawa Pharmaceutical Company name “FP-200”
There is a series. Further, commercially available melamine formalin resin sulfonate-based high-performance water reducing agents include "FT-3S" (trade name, manufactured by Denka Grace Co., Ltd.) and "Mol Master 10" and "Mol Master 20" (trade names, manufactured by Showa Denko KK). No.

The alkali metal sulfite, alkali metal bisulfite, alkali metal pyrosulfate, alkali metal pyrosulfite and calcium sulfite used in the present invention include, for example, potassium sulfite, sodium sulfite, Potassium sulfite, sodium bisulfite, potassium pyrosulfate, sodium pyrosulfate, potassium pyrosulfite,
Examples thereof include sodium pyrosulfite and calcium sulfite (hereinafter, referred to as sulfites), and one or more of them can be used in combination.

By using a specific amount of a high-performance water reducing agent and sulfites in combination, it has an effect of improving a large decrease in concrete slump with time, which is a basic problem of the high-performance water reducing agent, and This achieves the trade-off of improving the expression of the initial strength.

The mixing ratio of the high-performance water reducing agent to the sulfites is 0.4 to 3.0 parts by weight in terms of solids, and the sulfites and the like are anhydrous equivalents per 100 parts by weight of cement. In the range of 0.05 to 2.0 parts by weight. And when the compounding amount of the high-performance water reducing agent is small, the effect of improving the amount of decrease in the slump over time by increasing the compounding amount of sulfites and the like increases, and conversely, when the compounding amount of the high-performance water reducing agent is large. Shows the effect of improving the amount of aging, such as slump, even when the amount of sulfites is small. The mixing ratio of the high-performance water reducing agent is 0.5 to 2.
5 parts by weight, sulfites and the like are preferably blended in a range of 0.1 to 1.5 parts by weight, and the high-performance water reducing agent is 0.7 to 2.0 parts by weight in terms of solid content, It is most preferable to add them in such a range as to be 0.2 to 1.0 part by weight.

When the amount of the high-performance water reducing agent is less than 0.4 part by weight with respect to 100 parts by weight of cement, even if the amount of sulfites and the like is increased, the effect of improving the amount of change with time such as slump is small. If the amount is more than 0 parts by weight, breathing or the like is liable to occur and the strength and durability are impaired, which is not preferable. If the amount of sulfites is less than 0.05 part by weight with respect to 100 parts by weight of cement, the effect of improving the amount of slump with time and the effect of improving the initial strength are small.
When the amount exceeds 0 parts by weight, the effect of accelerating the setting is increased, and the effect of improving the amount of aging such as slump is reduced, and
It is not preferable because cracking easily occurs during long-term outdoor exposure curing.

Sulfites and the like also have the effect of increasing the water-reducing property of the high-performance water reducing agent, and there is a slight difference in the effect of improving the amount of slump with time depending on the type. Among them, potassium sulfite is preferred. Sodium bisulfite, and the others show almost the same improvement.

The use of a high-performance AE water reducing agent containing a polycarboxylate as a main component in the present invention has a high water-reducing rate and a slump-retaining action by itself. On the contrary, it is not preferable because conversely, the water reduction rate may be lowered and the slump holding performance may be impaired. In addition, the use of lignin sulfonate in the present invention means that sulfites and the like only show an action as an accelerator even for general water reducing agents such as lignin sulfonate, and the amount of slump decrease with time increases. Not preferred.

As the gypsum used in the present invention, one or more of gypsum type II, gypsum dihydrate, gypsum hemihydrate and gypsum type III can be used. Gypsum also promotes the effect of improving the amount of slump with time, but in particular, type II anhydrous gypsum has the effect of increasing the initial strength in combination with sulfites and the like to increase the strength over the long term. Most preferred.

The activated silica used in the present invention includes silica fume, calcined ash of silicified wood, metakaolin which is a calcined product of kaolin mineral, and aerosil, all of which are amorphous silicon oxide or alumina silicate. Compound. Silica fume is an ultra-fine powder that is one order smaller than cement generated when metal silicon or silicon alloy is produced in an electric furnace. The ash of silicified wood is the firing of rice straw, chaff, bamboo, reeds, etc. It is ash. Metakaolin is a kaolinite such as kaolinite, dickite, halloysite or the like calcined at 500 ° C. or higher. Aerosil is an ultrafine powder of synthesized silicon oxide. These can be used alone or in combination of two or more.

Activated silica, unlike other pozzolanic substances, has a high hydration activity, increases the initial and long-term strength, greatly increases the resistance to cracks due to the daily temperature difference and the repetitive stress between dry and wet, and also contains sulfites and the like. It does not have a significant adverse effect on the effect of improving the amount of slump with time that the slump has. Among these, silica fume and metakaolin are more preferable in consideration of performance, economy, stable supply, and the like.

Further, the pozzolanic substance used in the present invention is an alumina siliceous clay mineral such as acid clay, activated clay, pyroferrite, zeolite, kaolin mineral and the like, and its calcined product at 500 ° C. or higher (excluding metakaolin). ), Diatomaceous earth and its calcined product, fly ash, and blast furnace slag, and one or more of these can be used. In addition, bentonite is not preferable because it has a swelling property and a small amount of addition increases the unit water amount and lowers the strength.

The pozzolanic substance has less hydration activity than activated silica, and therefore has little effect of increasing the initial strength and long-term strength. However, the pozzolanic substance enhances salt resistance, cracking resistance due to diurnal range and repeated stress of dry and wet, and sulfites. Does not have a significant effect on the effect of reducing the amount of decrease in the slump with time. Furthermore, in the coexistence of sulfites and gypsum, there is a quantitative range that shows a peak in intensity when used in combination with active silica, and the effect of simply using a pozzolanic substance and active silica is not a matter of moderation. Among the pozzolanic substances, those obtained by calcining clay minerals (excluding metakaolin) and fly ash are more preferable in consideration of performance, economy, supply stability and the like.

When two or more of gypsum, activated silica and pozzolan are used in combination, the effect of each of them alone increases synergistically as the number of constituent components increases.

When the gypsum is used in combination with the activated silica, the activated silica increases the initial and long-term strength in a smaller amount to promote the strengthening, and at the same time, has a resistance to cracks due to a daily difference in temperature and repeated stresses between dry and wet. And the adverse effect on the effect of improving the amount of slump decrease with time of sulfites is also reduced.

In the case of using gypsum and a pozzolanic substance together, the degree of various effects is lower than in the case of using together with activated silica.
It has the same effect.

When the active silica and the pozzolanic substance are used in combination, as described above, there is a quantitative range that shows a peak in intensity, and a higher intensity can be obtained than in the case of using each alone.

Further, the combined use of gypsum (particularly, type II anhydrous gypsum) and the three components of activated silica and pozzolanic substance promotes an increase in initial strength and a long-term high strength with a smaller amount of use, and at the same time, a temperature reduction. It exhibits crack resistance due to daily range and repeated stress of dry and wet.

The mixing ratio of the gypsum is as follows:
Regarding 00 parts by weight, regardless of whether active silica and pozzolanic substances are used in combination or not, the amount is 1 to 15 parts by weight in terms of CaSO _4. However, the strength is preferably 2 to 10 parts by weight, more preferably 4 to 8 parts by weight, at room temperature curing. 2-15 parts by weight when steam curing
4 to 10 parts by weight are more preferred. And cement 10
If the amount of gypsum is less than 1 part by weight with respect to 0 part by weight, the effect of promoting the improvement of the amount of change with time such as slump is small, and
If the amount exceeds the weight part, even if steam curing is performed, it is not possible to further increase the strength, and if an appropriate amount of a high-performance water reducing agent and sulfites are used, long-term outdoor exposure curing will cause cracking. It is not preferable because it may be easy.

The mixing ratio of activated silica is 100
1 to 15 parts by weight, preferably 2 to 12 parts by weight, and most preferably 4 to 10 parts by weight with respect to parts by weight. As the amount of addition increases, the strength is increased. If the amount of active silica is less than 1 part by weight, the amount of increase in strength is small even when used in combination with gypsum with respect to 100 parts by weight of cement. Even so, the action of improving elongation of strength and cracking is stagnated, which is not economically preferable.

The mixing ratio of the pozzolanic substance is as follows:
The amount is 2 to 15 parts by weight, preferably 4 to 12 parts by weight, more preferably 6 to 10 parts by weight with respect to 0 parts by weight. With respect to 100 parts by weight of cement, if the pozzolanic substance exceeds 15 parts by weight, the unsintered clay mineral may significantly increase the unit water volume, which is not preferable. If it is less than 2 parts by weight, it is used in combination with gypsum or activated silica. No addition effect is shown.

When the active silica and the pozzolanic substance are used in combination with each other, the amount of the active silica and the pozzolanic substance may be the same as the total amount of the active silica and the pozzolanic substance. is there. The present invention is not limited to the concrete mixing conditions. In other words, the maximum aggregate size, fine aggregate ratio, unit cement amount, and water cement ratio are factors that greatly affect strength and durability, but from the viewpoint of comparison against immiscibility under the same conditions, They are not bound at all.

Examples of the cement used in the present invention include various portland cements such as ordinary, fast, super fast, white, moderate heat, and low heat (belite cement), and blast furnace slag, fly ash, etc. Or various mixed cements in which silica powder is blended, and slag-based hydraulic compositions in which slag is blended to JIS standard values or more. In addition, the slag-based hydraulic composition in which the slag is blended to the JIS standard value or more is a blast furnace slag powder exceeding 70 parts by weight, and 98 parts by weight, and the rest is Portland cement, or a part of the cement is slaked lime or quicklime. It has been replaced.

The admixture of the present invention is added when kneading mortar or concrete, and the kneading method is not particularly limited, and may be a conventional method. The method is not particularly limited. Therefore, each component may be added separately when kneading the mortar or concrete irrespective of whether it is solid or liquid, and when using a powdered high-performance water reducing agent, it is preliminarily mixed with other components in a powder state. It may be added, or the sulfites may be dissolved in a liquid high-performance water reducing agent, etc., and added separately from other solid components. Alternatively, it may be suspended in the whole amount and added to the mixer. In order to reduce the amount of water per unit to obtain concrete with the same slump and to have a good effect on strength, knead the mortar or concrete with an admixture in which all components are mixed (using high-performance water reducing agent as well as powder). The method of addition at the time is most preferable. Although the reason for this is not clear, it may be due to the fact that the dissolution rate of the powdery high-performance water reducing agent, sulfites, and the like is slower than when the liquid is made liquid.

[0031]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Using the basic mix of concrete shown in Table 1, the combination of high performance water reducing agent, sulfites, gypsum, activated silica, and pozzolanic substance was combined, and the mix amount was changed to 100 parts by weight of cement and divided into concrete. The mixture was added and kneaded, and various tests were performed. The mixing of the concrete was carried out using a planetary type forced mixing mixer with a capacity of 100 liters.
One liter of concrete was mixed. The order of charging the materials is as follows: crushed stone, sand, cement (in this embodiment, since the admixture of the present invention uses powder, the components are mixed once to form an admixture. And kneaded for 10 seconds, then added water and kneaded for 90 seconds. The cement used was ordinary Portland cement, and the fine aggregate and crushed stone were from the Himekawa basin, Niigata Prefecture.

[0032]

[Table 1]

Hereinafter, various materials used in the examples will be collectively shown. <Materials> Cement: Made by Denki Kagaku Kogyo Co., Ltd., ordinary Portland cement Aggregate: River sand, crushed stone from Himekawa, Niigata Prefecture Water: Groundwater "High-performance water reducing agent" A: Polyalkylallyl sulfonate, manufactured by Daiichi Kogyo Seiyaku Product name "Cell Flow 110P", powdered B: Melamine formalin resin sulfonate, trade name "Molemaster 10" manufactured by Showa Denko KK, powdered "sulfites etc." a: Potassium sulfite: industrial b. Sodium bisulfite: industrial c. Potassium bisulfite: industrial d. Sodium sulfite: industrial use e. Calcium sulfite: Reagent 1st grade f. Sodium pyrobisulfite: industrial g. Potassium pyrobisulfite: industrial h. Sodium pyrosulfite: industrial i. Potassium pyrosulfite: Industrial “gypsum” a. Type II anhydrous gypsum (hydrofluoric acid generating by-product gypsum, Blaine specific surface area: 6000 cm ² / g) b. Gypsum: Industrial (Brain specific surface area 6500cm ² /
g) C. Hemihydrate gypsum: heat treatment of b at 140 ° C. (Brain specific surface area 10,000 cm ² / g or more) d. Type III anhydrous gypsum: heat treated at 200 ° C. (Brain specific surface area 10,000 cm ² / g or more) “Active silica” α. Silica fume: Efaco, Egypt, BET specific surface area 19.2 m ² / g β. Incinerated ash of silicified wood (rice straw): BET specific surface area 1.0
m ² / g γ. Metakaolin: A product obtained by firing [SEM clay] (trade name, manufactured by Kanto Bentonite Mining Co., Ltd.) at 700 ° C. and pulverized to a Blaine specific surface area of 8150 cm ² / g ε. Aerosil: Nippon Aerosil Co., Ltd., BET specific surface area 160 m ² / g “Pozzolanic substance” Kaolin: Product name manufactured by Kanto Bentonite Mining [SE
M clay] to a Blaine specific surface area of 8050 cm ² / g II. Heat-treated acid clay: Kanto Bentonite Mining Co., Ltd. Acid clay is calcined at 1000 ° C and Blaine specific surface area is 5500cm
Pulverized to ² / g III. Heat treated product of zeolite: Zeolite G35 product of Kanto Bentonite Mining Co., Ltd. calcined at 1000 ° C. and pulverized to a Blaine specific surface area of 6500 cm ² / g IV. Diatomaceous earth: Kanto bentonite mining company [Celi
teFC] pulverized to a specific surface area of 7000 cm ² / g Fly ash: Tohoku Electric Power Co., Inc., Blaine specific surface area 3,500 cm ² / g VI. Blast furnace slag: Nippon Steel Chemical Co., Ltd., Brain specific surface area 4,500 cm ² / g

EXAMPLE 1 Concrete mixed with different types and amounts of high-performance water reducing agent, sulfites, and gypsum was mixed with slump in a room at a temperature of 20 ± 3 ° C. and a change in slump with time, and φ10 × 20
28-year-old, 28-year-old column-shaped test specimen
The compressive strength was measured for one day and one year. In addition, cracks of the specimen were also observed. In addition, when the slump fluctuates due to the amount of the water reducing agent and other components in mixing the concrete, the unit water amount was adjusted so that the slump was within the range of the design value, and the unit water amount was recorded. The results are shown in Tables 2 to 4.

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

As can be seen from Tables 2 to 4, the slump of the high-performance water reducing agent alone caused a large decrease with time, and no working time was obtained (Experiment Nos. 1-1 to 1-7). When salts and the like are used, it is shown that the amount of reduction with time can be improved in the range of 0.05 to 2.0 parts by weight, such as sulfites, with respect to 100 parts by weight of cement (Experiment No. 1-8 to Experiment No. .1
-16). Furthermore, it is shown that the use of gypsum in an amount of 1 part by weight or more based on 100 parts by weight of cement can further reduce the amount of slump with time (Experiment Nos. 1-12 and No. 1-26). In addition, with regard to strength, by using in combination with the sulfites of the present invention rather than adding gypsum alone, the initial strength is increased while maintaining the slump, and a high strength is obtained in relation to the reduction of the unit water amount. (Experiment No. 1-34 and Experiment No. 1-35 to Experiment No. 1-42). At room temperature, the added amount of gypsum significantly increases from 2 parts by weight to 100 parts by weight of cement and peaks at 4 to 8 parts by weight. It is shown that the weather resistance is particularly deteriorated when the content is more than 12 parts by weight (Experiment Nos. 1-26 and 1-3)
Four).

Example 2 Experiment No. 1 of Example 1 1-34, No.1-26 to 1-33 concrete was formed into a cylindrical specimen of φ10 × 20cm, placed in front for 6 hours, heated to 75 ° C in 3 hours, kept for 4 hours, and then steamed. Stop the valve and let it cool down naturally in the curing tank until the next day.
A specimen of φ10 × 20 cm, which was cured by exposing outdoors without steam curing, was measured for compressive strength at the age of 28 days and 1 year, and cracks of the specimen were also observed. Table 5 shows the results.

[0040]

[Table 5]

In the case of steam curing, higher strength can be obtained by using in combination with the sulfite of the present invention than in the case of adding gypsum alone (comparison between Experiment Nos. 2-1 and 2-4). ). And, with respect to 100 parts by weight of cement, the strength is remarkably increased from 2 to 4 parts by weight of the gypsum, and the initial and long-term strength increases as the amount added increases, but the elongation becomes slow at 10 parts by weight or more, and If the amount exceeds the weight part, the weather resistance tends to be deteriorated. Therefore, in the combined use of gypsum with sulfites, etc., from the viewpoint of improvement of the amount of slump decrease over time, strength development at room temperature or steam curing, and weather resistance, 100 parts by weight of cement, gypsum 1 to 15 parts by weight is effective, at room temperature is 2 to 10 parts by weight,
4 to 8 parts by weight are more preferred. Especially in steam curing,
Preferably 12 parts by weight, most preferably 4 to 10 parts by weight.

Example 3 Experiments Nos. 1-12, Nos. 1-26 to 1-33, and Nos. 1-
Using concrete of 38, changing the type and amount of activated silica and mixing the concrete, kneading the concrete, the time-dependent change of the slump as in Example 1 and the standard cured one-day old specimen of φ10 × 20 cm cylindrical specimen. The 28-day compressive strength was measured, and the 28-year-old specimen, which had been standard-cured, was repeatedly immersed in water and dried by heating. The 1-year-old compressive strength was measured and the specimen surface was observed for cracks. The results are shown in Tables 6 and 7.
The repeated test of immersion in water and drying by heating was 80 days for 3 days.
C., and immersed in running tap water for 4 days. This is repeated as one cycle. Therefore, it is a severer test method than the outdoor exposure test, and 52 cycles are repeated for one year of the material (365 days).

[0043]

[Table 6]

[0044]

[Table 7]

As can be seen from Tables 6 and 7, when the high-performance water reducing agent of the present invention, a sulfite or the like, gypsum and active silica are used in combination, the initial and long-term strengths are synergistically improved and cracks are improved. When the added amount of gypsum is small, the added amount of activated silica is 1 part by weight with respect to 100 parts by weight of cement, the increase in strength is small, and cracks occur (experiment)
No. 3-2) shows that the generation is reduced even by 1 part by weight by adjusting the amount of added gypsum to an appropriate strength (Experiment No. 3-21). Therefore, the preferred amount of active silica used is
It is 1 to 15 parts by weight with respect to 100 parts by weight of cement, and is preferably 12 parts by weight or less (〜2 parts by weight), more preferably 4 to 10 parts by weight in view of long-term strength elongation.

Example 4 Experiment No. 1 of Example 1 1-12, No. Experiment of 1-38 and Example 3
No. Using concrete of 3-22 to 3-25, changing the type and amount of pozzolanic substance, using sulfites, gypsum, activated silica, and combining gypsum and activated silica with the same test items as in Example 3 The test was performed. Tables 8 and 9 show the results.
Shown in

[0047]

[Table 8]

[0048]

[Table 9]

From Tables 8 and 9, it can be seen that when the pozzolanic substance is used in combination with sulfites or gypsum, the effect of improving the strength and the like is greater than when the active silica is used in place of the pozzolanic substance. But increase the initial and long-term strength as in the case of silica fume (Experiment N
o. 4-2, Experiment No. 4- 3-Experiment No. 4-10 comparison). When a system is used in which the high-performance water reducing agent of the present invention, sulfites and the like, gypsum, activated silica and a pozzolanic substance are used in combination, the initial and long-term strengths are further increased and the cracks are also improved with a combination of each component in a smaller amount. Is shown.

Example 5 Experiment No. 4 of Example 4 4-15-Experiment No. Using concrete of 4-18, take out only the powdered high-performance water reducing agent in this admixture, knead it and dissolve it in the entire amount of water, mix the other components once with cement, mix crushed stone, sand , Cement (excluding the high-performance water reducing agent, including the present admixture component), and the concrete was kneaded and mixed in the same manner as in Example 1, and the test was performed with the same test items as in Example 2. .
Table 10 shows the results.

[0051]

[Table 10]

In order to obtain a design slump, Experiment No. 1 was conducted by mixing with a powdered high-performance water reducing agent. 4-15-Experiment No. Since the unit water amount increases by 10 to 15 kg / m ³ in each case than in the case of 4-18, it was shown that this admixture was more preferable to be used as an admixture using a powdered high-performance water reducing agent. . However, as shown in Table 10, even when the high-performance water reducing agent is used as a liquid separately from other components, the basic performance of the admixture is exhibited, the demolding strength after steam curing is increased, and This shows that concrete with good long-term strength and good weather resistance can be produced.

[0053]

As described above, the amount of slump decrease with time can be improved and concrete with good workability can be produced. Regardless of the curing method, the initial and long-term strength is increased, and high strength is obtained. At the same time, it reduces the occurrence of cracks even under severe conditions such as curing outdoors and curing in water. Therefore, by using the admixture of the present invention and the cement composition using the same, it is possible to construct a highly durable and high-strength structure and to manufacture a concrete product.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // C04B 103: 32 103: 60

Claims (4)

[Claims] 1. A high-performance water reducing agent, and one or more of an alkali metal sulfite, an alkali metal bisulfite, an alkali metal pyrosulfate, an alkali metal pyrosulfite, and calcium sulfite, A cement admixture characterized by containing gypsum. 2. The cement admixture according to claim 1, further comprising an activated silica and / or a pozzolanic substance. 3. A high-performance water reducing agent of 0.4 to 3.0 parts by weight in terms of solids, 100 parts by weight of cement, alkali metal sulfite, alkali metal bisulfite, alkali metal pyrosulfate One or more of salts, alkali metal pyrosulfites, and calcium sulfites may be used in an amount of 0.05 to 2.
A cement composition comprising 0 parts by weight and 1 to 15 parts by weight of gypsum in terms of CaSO ₄ . 4. Further, based on 100 parts by weight of cement,
4. A cement composition as claimed in claim 3, comprising 1 to 15 parts by weight of activated silica and / or 2 to 15 parts by weight of a pozzolanic substance.