JP2010195622A - Water reducing agent composition and mortar or concrete using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water reducing agent composition which solves the problem that, in accordance with the lot and brand of the cement to be used, the fluidity of mortar or concrete admixed with a polycarboxylate based water reducing agent is remarkably different(reduced), and to provide mortar or concrete using the same. <P>SOLUTION: (1) The water reducing agent composition comprises: a polycarboxylate based water reducing agent: and cyanamide. (2) The mortar or concrete is obtained by adding a water reducing agent composition comprising cyanamide of 2 to 30 pts.mass to 100 pts.mass of the solid content of the polycarboxylate based water reducing agent based on 100 pts.mass of the cement or a cement bonder by 0.12 to 1.5 pts.mass in terms of a solid content. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a water reducing agent composition. Specifically, it is a water-reducing agent composition containing cyanamide in a polycarboxylate-based water reducing agent, which further enhances the dispersion effect of the polycarboxylate-based water reducing agent and is used in civil engineering / building structures and secondary products. It improves the fluidity of mortar and concrete.

In recent years, the performance of water reducing agents used in mortar and concrete, in particular, polycarboxylate-based water reducing agents has been dramatically improved.
However, the polycarboxylate-based water reducing agent has a problem that the fluidity (mortar flow value, concrete slump and slump flow value) differs significantly depending on the lot, brand, and type of cement used.
That is, even the same cement and the same factory vary depending on the lot, and varies depending on the factory, manufacturer, and cement type.

One of the reasons why the fluidity is remarkably different depending on the cement is that sulfate ions instantly dissolved from the sodium sulfate and potassium salts contained in the cement hinder the adsorption of the polycarboxylate-based water reducing agent. In order to improve this, Ca, Sr, Ba and Pb chlorides, nitrates, nitrites, sulfites that trap sulfate ions and produce salts with a lower dissolution rate than sodium and potassium salts, It is known that highly soluble alkaline earth salts such as thiosulfate and organic acid salts are effective (see Patent Document 1). In addition, in order to improve fluidity and initial strength, one or more of calcium sulfite, calcium nitrate, calcium formate, calcium thiocyanate and calcium acetate are added to cement, pozzolanic fine powder, water, water reducing agent, and cement. A cement slurry containing it has also been proposed (see Patent Document 2). However, these proposals are not sufficient for the decrease in fluidity due to the cement lot and brand used.
The present invention solves the problem that the fluidity of mortar or concrete to which a polycarboxylate-based water reducing agent is added is significantly reduced depending on the lot, brand, and type of cement used.

Japanese Patent Laid-Open No. 11-180746 JP 2002-037653 A

  The present invention solves the problem that the fluidity of mortar or concrete to which a polycarboxylate-based water reducing agent is added differs significantly (decreases) depending on the lot, brand, and type of cement used. The present invention has been completed by finding out that it can be achieved by containing cyanamide in an acid salt water reducing agent.

  That is, the present invention provides (1) a water-reducing agent composition comprising a polycarboxylate-based water reducing agent and cyanamide, and (2) a solid of a polycarboxylate-based water reducing agent in 100 parts by mass of cement or cement binder. A mortar or concrete obtained by adding 0.12 to 1.5 parts by mass of a water reducing agent composition containing 2 to 30 parts by mass of cyanamide with respect to 100 parts by mass.

The present invention solves (1) compatibility problems such as deterioration of fluidity of mortar or concrete to which a polycarboxylate-based water reducing agent is added depending on the lot, brand, and type of cement. Workability can be obtained. In addition, cement with higher fluidity can achieve greater fluidity. (2) If the unit water amount, flow value, slump and slump flow value are kept constant, the amount of polycarboxylate-based water reducing agent added can be reduced. (3) Improves dispersibility even for agglomeration of pozzolanic fine powder, and provides high fluidity and improves strength. (4) To manufacture civil engineering structures and concrete secondary products. Thus, since an ultra-high strength of 100 N / mm ² or more can be easily obtained, there is an effect that an economical and advantageous design is possible with high durability.

  The present invention will be described in detail below.

The polycarboxylate salt water reducing agent of the present invention is a water reducing agent generally called a high performance AE water reducing agent, and is a copolymer or a salt thereof containing an unsaturated carboxylic acid monomer as one component. For example, polyalkylene glycol monoacrylate, polyalkylene glycol monomethacrylate, a copolymer of maleic anhydride and styrene, a copolymer of acrylic acid or methacrylate, and a monomer copolymerizable with these monomers. And a copolymer derived from a monomer.
Specifically, BASF Pozzolith Co., Ltd. trade name “Leo Build SP8SV / 8RV, 8HV, 8HU etc. Leo Build SP8 Series”, Nippon Seika Co., Ltd. trade name “Sea Kament 1100NT, 1100NTR etc. Series”, Takemoto Yushi ( Co., Ltd. trade name "Tupol HP series, Chupole SR, Chupole SSP-104, Chupole NV-G series", Grace Chemicals Co., Ltd. trade name "Super 200, 300, 1000 series", Kao Co., Ltd. trade name "Mighty 21WH, 21LV, 21VS, 21HF, 21HP, Mighty 3000S, 3000H Series", Floric Co., Ltd. trade name "SF500 series such as SF500S, SF500R, SF500H, SF500SK", other general purpose, high strength, Super high Those commercially available as for degrees is used.

The present invention is a water reducing agent composition containing cyanamide in these polycarboxylate-based water reducing agents, and contains 2 to 30 parts by mass of cyanamide with respect to 100 parts by mass of the solid content of the polycarboxylate-based water reducing agent. It is preferable to do so. Regardless of cement with low fluidity or large cement, if the cyanamide is less than 2 parts by mass, sufficient fluidity improvement effect cannot be obtained, and even if it exceeds 30 parts by mass, the fluidity improvement effect reaches its peak. 6 parts by mass or more is more preferable, and 8 to 25 parts by mass is most preferable.
Polycarboxylate-based water reducing agents are usually synthesized at a pH of 2 to 3, but caustic soda is added to prevent rusting and corrosion of metal in production facilities and storage facilities to a pH of 7 to 7. 8 weak alkalinity. However, the water reducing agent composition of the present invention is produced by adjusting the pH to the range of 3-6. The reason is that cyanamide is stable in the range of pH 3 to 6 in an aqueous solution, and when the pH is less than 3 or more than 6, it changes to dicyandiamide or the like, and the fluidity improving effect is lowered.
Therefore, when the commercially available polycarboxylate-based water reducing agent to be used is weakly alkaline, the pH is adjusted to 3 to 6 with acetic acid, formic acid, gluconic acid or the like. If a synthetic product having a pH of less than 3 is used directly, adjust with caustic soda.
The addition amount of the water reducing agent composition of the present invention is 0.12 to 1.5 in total of solid content of cyanate (solid content) and solid content of polycarboxylate-based water reducing agent with respect to 100 parts by mass of cement or cement binder. Part by mass. If the amount is less than 0.12 parts by mass, sufficient fluidity improving effect is not shown, and even if 1.5 parts by mass or more is blended, the fluidity improving effect reaches a peak. 2 parts by mass is more preferable.

  In addition, as an example of the manufacturing method of cyanamide used by this invention, lime nitrogen is melt | dissolved in a hot water, Carbon dioxide gas is blown into the filtrate, and calcium ion is precipitated as calcium carbonate, and it filters. Cyanamide in the filtrate crystallizes when cooled, so it can be easily taken out as a solid, but it is uneconomical to redissolve as a water reducing agent composition. It is more economical to use the aqueous solution with the cyanamide concentration adjusted as it is. These are usually the same as those marketed as liquid fertilizers.

  The cement used in the present invention is usually mixed cement and ecocement such as Portland cement and fly ash cement, blast furnace slag cement, such as early strength, moderate heat, low heat, white color, sulfate resistance. From the viewpoint of fluidity, mixed cement, low heat, medium heat, and sulfate-resistant cement are preferable, and from the viewpoint of initial strength, early strength, super early strength, medium heat cement, and mixed cement are preferable.

The cement binder of the present invention is a mixture of spherical particles of pozzolanic fine powder that promotes fluidity improvement effect, gypsum used as a high-strength admixture, and the like.
Spherical particle-shaped pozzolanic fine powder classifies silica fume generated during the production of silicon alloys and metal silicon in electric furnaces, silica fume derived from zirconia, and fly ash by-produced from pulverized coal-fired thermal power plants to 10-20 microns or less Coal gasification fly ash, a fused silica fine powder produced as a by-product from a thermal power plant that burns gasified coal. These are used in combination with polycarboxylate-based water reducing agents and are often used in the production of high fluidity / high strength mortar or concrete.
Among pozzolanic fine powders, silica fume that promotes or develops both fluidity and high strength is the most important component, but because it is an ultrafine powder of several microns or less, it easily aggregates in mortar or concrete. Moreover, since it is granulated in order to improve transport efficiency, it has the subject that dispersibility falls more and the improvement effect of fluidity | liquidity cannot fully be exhibited. However, when used together with the water reducing agent composition of the present invention, the dispersion effect is increased and the fluidity improving effect is also increased. As a result, when the necessary fluidity is made constant, the addition of the water reducing agent composition Since the amount can be reduced and the reactivity is improved, the strength is increased, so that more economical mortar and concrete can be produced.
Usually, 40 parts by mass or less of one or more spherical pozzolanic fine powders are blended with 100 parts by mass of cement.

Gypsum used as a high-strength admixture is type II anhydrous gypsum, and other fine powders such as metakaolin and silicified wood incinerated ash (not non-flowable) that have not been improved in fluidity but heat treated clay minerals. Crystalline SiO ₂ is the main component), diatomaceous earth, opal silica powder and the like increase the strength and can be used as appropriate.
Anhydrous gypsum has a large strength effect in a small amount, and is usually blended in an amount of 6 parts by mass or less based on 100 parts by mass of cement.

The method for adding the water reducing agent composition of the present invention is not particularly limited, and when kneading mortar or concrete, it is added together with cement, binder, aggregate, etc., dissolved in water (simultaneous addition method), Cement, binder, aggregate, and water are kneaded first, and then added as a water reducing agent composition stock solution (post-addition method) and kneaded.
There are no particular limitations on the types and maximum dimensions of fine aggregates and coarse aggregates used in the production of mortar and concrete, and the blending ratios are suitably used in combination according to the purpose and application.

In the present invention, when kneading mortar or concrete, a coagulation regulator, an antifoaming agent, and a shrinkage reducing agent and / or an expanding material can be used as appropriate in order to reduce self-shrinkage, thereby increasing bending strength and toughness. Therefore, organic fibers, metal fibers, glass fibers, and other reinforcing fibers can be used.
The curing of the mortar or concrete according to the present invention may or may not be steam-cured, and can be cured by autoclave, and may be cured on-site in a placed state, and is not limited to the curing method. is there.
The molding method is not particularly limited, and casting by high flow, vibration molding using an appropriate slump, centrifugal force molding, solid pressure vibration pressing molding, and the like are possible.

  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 are summarized below.

"Materials used"
Polycarboxylate-based water reducing agent: manufactured by Grace Chemicals, solid content concentration 27% by mass, pH 4.0, for high strength / ultra high strength (in the table, solid content is abbreviated as PC)
Cyanamide: Cyanamide aqueous solution: Cyanamide solid content concentration of 36% by mass adjusted to a solid content concentration of 27% by mass for easy handling (pH adjusted to 4.0 with acetic acid), Denki Kagaku Kogyo Co., Ltd. Made (abbreviated as CN as the solid content of cyanamide in the table)
Highly soluble inorganic salt: calcium acetate monohydrate (reagent). Type of comparison cement or cement binder (abbreviated as C or CI in the table)
CI: Ordinary Portland cement (brand with the smallest pick-up flow value according to JIS R 5201 selected from five brands)
C-II: Cement binding material in which 25 parts by mass of granular silica fume is blended with 100 parts by mass of ordinary portland cement of CI C-III: 25 parts by mass of granular silica fume in 100 parts by mass of ordinary portland cement of C-I Binder C-IV containing 2 parts by weight of styrene and anhydrous gypsum: normal Portland cement (a brand with the largest flow-up value according to JIS R 5201 selected from 5 brands) 25 parts by mass of granular silica fume in 100 parts by mass Cement binder aggregate containing 2 parts by weight of anhydrite and anhydrous gypsum: fine aggregate from Himekawa, Niigata (those adjusted to 1.2 mm or less and normal 5 mm underneath and coarse aggregate from Himekawa, Niigata, crushed stone, Maximum dimension (13mm)

"Test items and methods"
Measurement of mortar flow: According to JIS R 5201. However, the spread due to self-flow when it was pulled out was measured. The measurement was performed on a 50 × 50 × 2 tcm acrylic plate placed on the flow table.
Molding of mortar and strength measurement method: Compressive strength is cast mold or table vibration mold (when flow value is small) in a 5 × 10 cm mold, standard curing in the room at 20 ° C. until the next day, demolding and 70 The steam was cured at 24 ° C. for 24 hours, and after cooling, the strength was measured.
Measurement of concrete slump: Measured according to JIS A 1101. However, when fluidized, the lateral spread was measured as a slump flow value.
Molding of concrete, measurement of compressive strength: compressive strength is molded into a mold of φ10 × 20cm, table vibration molded, standard cured until 20 days in a room at 20 ℃, demolded, steam cured at 70 ℃ for 24 hours, and then cooled The strength was measured.

"Mortar or concrete mixing method"
Cement or cement binder, fine aggregate, fine aggregate and coarse aggregate were kneaded for 30 seconds, and then kneaded water in which the water reducing agent composition of the present invention was dissolved was added and kneaded. In the case of mortar, 1 L was mixed with a mortar mixer according to JIS R 5201, and concrete was mixed with 10 L for an omni mixer.

"Example 1"
C-II and C-III cement binders are used, and 80 parts by mass of fine aggregate below 1.2 mm is blended with respect to 100 parts by mass (unit amount 1210 kg / m ³ ). The mortar flow value and the compressive strength were measured by changing the ratio of solid content of the polycarboxylate-based water reducing agent and the solid content of cyanamide and the addition amount thereof to 16% by mass. For comparison, calcium acetate, which has been conventionally known as a highly soluble inorganic salt having an effect of improving fluidity, was also used. The results are shown in Table 1.
The water content in the polycarboxylate-based water reducing agent and the cyanamide aqueous solution was incorporated into the water binder ratio as kneaded water.

From Table 1, when a C-II cement binder containing silica fume using a cement having a small flow value is used, the flow value of the comparative example of the polycarboxylate-based water reducing agent of Experiment No. 1-1 is as follows: In the comparative example of Experiment No. 1-2 in which conventionally known calcium acetate is added, the increase is about 50 mm.
Experiments No. 1-3 to No. 1 of Examples in which the solid content of the polycarboxylate-based water reducing agent was the same as in the comparative example using the C-II cement binder, and the solid content of cyanamide was changed. -11, the flow value suddenly increases as the amount of cyanamide is increased, and the mass ratio of solid content / cyanamide (solid content) of the polycarboxylate-based water reducing agent is more remarkable than 100/2. Demonstrate. Furthermore, 100/6 or more is more preferable, and 100/8 or more is still more preferable. Even if the amount of cyanamide is increased more than the ratio of 100/30, the flow value does not increase more than that and reaches a peak. Therefore, the solid content / cyanamide (solid content) mass ratio of the polycarboxylate-based water reducing agent is most preferably 100/8 to 100/25. It is also shown that the strength increases as the flow value increases.
In experiments No.1-12 to No.1-19 using C-III cement binder containing silica fume and anhydrous gypsum, the solid content of polycarboxylate-based water reducing agent / the mass ratio of cyanamide (solid content) Despite this, the flow value tends to be slightly higher than in the case of C-II containing only silica fume, and SO ₄ ions generated by dissolution of anhydrous gypsum do not decrease the flow value, and the strength is around 20 N / mm ^2. It turns out that it becomes high.
Using the cement with the largest flow value, and using C-IV cement binder containing silica fume and anhydrous gypsum in the same way as C-III, the solid content of cyanamide was reduced with the solid content of polycarboxylate water reducing agent constant. In the experiment No.1-20 to No.1-27 of the changed example, as in the case of the binder using the cement having a small flow, the solid content / cyanamide (solid content) of the polycarboxylate-based water reducing agent The mass ratio is more remarkable than 100/2. Furthermore, 100/6 or more is more preferable, and 100/8 or more is still more preferable. Even if the amount of cyanamide is increased more than the ratio of 100/30, the flow value does not increase more than that and reaches a peak. Therefore, the solid content / cyanamide (solid content) mass ratio of the polycarboxylate-based water reducing agent is most preferably 100/8 to 100/25. Moreover, the tendency for intensity | strength to become higher than the case of C-III is also shown with the improvement of a flow value.
Using a C-II cement binder with cement having a small flow value, the mass ratio of solid content / cyanamide (solid content) of the polycarboxylate-based water reducing agent is 100/20, and the total amount added is In the changed Experiment Nos. 1-28 to 1-33, 0.5 parts by mass is equivalent to 0.810 parts by mass of the polycarboxylate-based water reducing agent of Experiment No. 1-1, which is a comparative example. A flow value is obtained, and an equivalent flow value is obtained with a small amount. Furthermore, the flow value increases rapidly as the amount added is increased, but it reaches a peak at 1.5 parts by mass, and 1.2 parts by mass or less is most preferable economically.

"Example 2"
Using CI cement, using the concrete composition in Table 2, the polycarboxylate-based water reducing agent solid content / cyanamide (solid content) mass ratio was 100/0 and 100/20, and the addition amount was changed. Compressive strength of slump and standard curing material age 7 days was measured. In addition, the fine aggregate used the normal fine aggregate for concrete of 5.0 mm or less. The results are shown in Table 3.

  Table 3 shows that the present water reducing agent composition is 0.12% by mass, comparing the experiments No. 2-1 to No. 2-6 of the comparative example with the experiments No. 2-7 to No. 2-12 of the invention example. The increase in slump and the increase in strength are observed at 0.15 parts by mass, and a slump of 0.20 parts by mass or more in the case of the polycarboxylate-based water reducing agent alone is obtained at 0.15 parts by mass. That is, it is economical because 0.05 parts by mass on the basis of the active ingredient and 0.19 parts by mass in terms of aqueous solution may be required. As the amount of addition increases, the difference between the two slumps increases, indicating that mortar or concrete can be produced more economically. In addition, the compressive strength tends to increase as the dispersion effect increases.

In the present invention, (1) compatibility problems such as a decrease in fluidity of mortar or concrete to which a polycarboxylate-based water reducing agent is added are solved depending on the lot, brand, and type of cement, and good workability is obtained. (2) If the unit water amount and flow value, slump and slump flow value are constant, the amount of polycarboxylate-based water reducing agent can be reduced, which is economical. (3) Agglomeration of pozzolanic fine powder In contrast, dispersibility is improved, high fluidity is obtained, and strength is improved. (4) When manufacturing civil engineering structures and secondary concrete products, ultra-high strength of 100 N / mm ² or more is achieved. Since it can be easily obtained, it is highly durable and economical and advantageous design can be achieved. Therefore, it is widely used in the civil engineering and construction fields.

Claims (2)

  A water reducing agent composition comprising a polycarboxylate-based water reducing agent and cyanamide.   A water reducing agent composition containing 2 to 30 parts by mass of cyanamide with respect to 100 parts by mass of a solid content of a polycarboxylate-based water reducing agent in 100 parts by mass of cement or cement binder is 0.12 to 1 in terms of solids. Mortar or concrete added by 5 parts by mass.