JP2003277111A - Hardening accelerator and cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a hardening accelerator for cement which exhibits stable hardening acceleration effect without depending on the kinds and brands of cement, and to obtain a cement composition. <P>SOLUTION: The hardening accelerator contains slaked lime and at least one or more kinds selected from thiosulfate, formate, nitrate and nitrite. The blending proportion between the slaked lime and at least one or more kinds selected from thiosulfate, formate, nitrate and nitrite is controlled to 97/3 to 5/95 by a mass ratio. Further, 100 pts.mass of cement is blended with the hardening accelerator of 0.2 to 10 pts.mass to compose the cement composition. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hardening accelerator for cement, and more specifically, to a hardening accelerator and cement composition for cement which accelerates the setting hardening of cement paste, mortar or concrete to develop early strength. Yes, it is used for the rationalization of construction of civil engineering structures, early opening (road paving, etc.) and early demolding of secondary concrete products.

[0002]

2. Description of the Related Art Conventionally, the design strength of concrete for civil engineering and building structures is manifested at a material age of 28 days or 91 days, but until the strength becomes such that the formwork can be removed and the next concrete can be placed. It takes a few days to a week. Also,
It takes about one week to develop a temporary opening strength of 3.5 N / mm ² (bending strength) on roads. If the strength with which the formwork can be removed and the next concrete can be poured or the temporary open strength can be developed earlier, more economical and rational construction becomes possible. Even for secondary concrete products, if the steam curing time is shorter and demoldable strength can be developed, the manufacturing cycle of the product can be increased, and an economical and rational production plan is possible. Further, since the manifestation property of concrete strength is affected by temperature, a cement and a cement hardening accelerator that develop strength particularly early in winter are required. For this purpose, super early strength cement that develops strength faster than early strength cement was developed as One Day Cement in the mid-1940s and was JIS standardized, but now it is manufactured excluding one company. The reality is that they do not.

[0003]

A large number of inorganic compounds and organic compounds are known as hardening accelerators for cement. As inorganic compounds, classical chlorides such as calcium chloride, nitrates and nitrites, highly soluble sulfates and sulfites and aluminum compounds such as alums and alumite,
There are thiosulfates, thiocyanates, and chromates, and in addition, as a quick-setting agent that is stronger than a curing accelerator,
Alkali metal carbonates, bicarbonates, silicates and aluminates are known. Formate salts, acetate salts, and amino acid compounds are known as organic compounds, and triethanolamine is known as an accelerator. However,
These hardening accelerators have some effect on ordinary Portland cement, but may be effective depending on the brand for early-strength Portland cement, which has a faster hydration reaction rate than ordinary Portland cement.
In some cases, it may not be present at all, and in some cases, early strength may be reduced. Further, there is a problem that even if a plurality of curing accelerators are combined, the effects of any one of the curing accelerators are biased and a synergistic effect cannot be found. On the other hand, a method of utilizing slaked lime for early demolding of concrete products for steam curing has already been proposed (Japanese Patent Publication No. 57-1186).
Although this method is used, concrete is prepared by adding insoluble anhydrous gypsum and slaked lime and / or soft calcinated lime to cement, and steam-cured at a temperature 35 to 55 ° C higher than the kneading temperature for a short time. It is to obtain demolding strength, and there is no description that a synergistic hardening promoting action can be achieved by the combined use of slaked lime and a specific hardening accelerator among hardening accelerators. The present inventor has conducted intensive studies as a purpose of providing a cement hardening accelerator that exhibits a stable hardening promoting action regardless of the type and brand of cement, and by combining specific components among many hardening accelerators. The inventors have found that it can be achieved and completed the present invention.

[0004]

Means for Solving the Problems That is, the present invention is a hardening accelerator containing slaked lime and at least one selected from thiosulfates, formates, nitrates and nitrites. And a curing accelerator which makes the compounding ratio of at least one selected from thiosulfates, formates, nitrates and nitrites 97/3 to 5/95 by mass ratio. Furthermore, it is a cement composition characterized by mix | blending the said hardening accelerator so that it may become 0.2-10 mass parts with respect to 100 mass parts of cement.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The slaked lime of the present invention is particularly limited
Not quick lime (mainly calcium oxide Ca
O) digested (main component is calcium hydroxide Ca
(OH) ₂) May be used even if it contains some impurities.
It is possible. In addition, calcined dolomite and free lime (f-C
aO) containing commercial expansive material digested
Good. The slaked lime of the present invention has the same fineness as that of cement.
Blaine specific surface area (JIS R5201) 3000 cm
²/ G or more is acceptable, but finer one shows more hardening promoting action
Because it is 5000 cm²/ G or more is preferable, 6000c
m²/ G or more is more preferable.

The hardening accelerators used in combination with the slaked lime of the present invention are thiosulfates, formates, nitrates and nitrites, and alkali metal salts of sodium and potassium thereof,
And alkaline earth metal salts of calcium and magnesium. These are not particularly limited, and those commercially available for industrial use can be used. Incidentally, it is the above-mentioned four kinds of coagulation accelerators that show a synergistically stable hardening-promoting action in combination with slaked lime. A synergistic effect cannot be obtained with a combination of only (such as salt). Further, in the combination of slaked lime and thiosulfate of the present invention, the degree of synergistic effect also differs depending on the type of thiosulfate and the like, and the difference is also shown depending on whether it is an alkali metal salt or an alkaline earth metal salt. Alkali metal salts have a higher early strength than alkaline earth metal salts, but tend to suppress long-term strength growth. Alkaline earth metal salts have a lower early strength but do not hinder long-term strength growth. Show a trend. From the above, in the present invention, a preferable combination can be selected depending on whether the initial strength is emphasized or the long-term strength is emphasized.

In the hardening accelerator of the present invention, slaked lime and
The mixing ratio of thiosulfate etc. (as anhydrous salt) is 9 by mass.
7/3 to 5/95 is preferable, and 0.2 to 10 parts by mass is preferably mixed with 100 parts by mass of cement.
More slaked lime and less thiosulfate, etc. than this blending ratio, or less slaked lime and more thiosulfate, the synergistic promoting effect will be smaller, so 96 / 4-10 / 90 is more preferable. Is 95 / 5-2
It is 0/80.

The hardening accelerator of the present invention is preferable because the hardening effect is small when the addition amount is 0.2 parts by mass or less with respect to 100 parts by mass of cement at room temperature curing, and the elongation of strength is further suppressed when it exceeds 10 parts by mass. Absent. Further, even in the case of steam curing, if the amount is less than 0.2 parts by mass, it is difficult to obtain the demolding strength early, and if it exceeds 10 parts by mass, the strength at the time of demolding does not largely decrease, but the elongation of the strength thereafter is hindered. In any curing method, it is preferably 0.5 to 8 parts by mass, more preferably 1 to 6 parts by mass.

In the present invention, the type of cement used is not particularly limited, but ordinary Portland cement, early strength Portland cement, super early strength Portland cement, moderate heat Portland cement, white Portland cement, sulfate resistant salt Various portland cements such as portland cement and low heat-generating portland cement, and mixed cements such as blast furnace slag cement, fly ash cement, and silica cement, and the higher the hydraulic hardness, the higher the early strength tends to be.

In the present invention, general water reducing agents such as lignin sulfonate, polyol and oxycarboxylate, high performance water reducing agents and high performance AE water reducing agents are also used. Of these, high performance water reducing agents such as polyalkylallyl sulfonates and melamine resin sulfonates, which have a large water reduction rate, and high performance AE water reducing agents, which are polycarboxylic acid salts, are preferable.

In the present invention, in order to further increase the strength of concrete, a high-strength admixture containing gypsum as a main component, silica fume or metakaolin, and active silica such as fly ash classified to 20 μm or less as a main component. The high-strength admixture can be used together. further,
Commercially available expansive materials can also be used together to reduce cracking and to produce chemically prestressed concrete.

In the present invention, the method of using the hardening accelerator is not particularly limited, but (1) a method of adding a mixture of ground slaked lime and thiosulfate, etc. when mixing concrete, , (2) a method in which both are mixed and crushed and added when mixing concrete, and (3) what is suspended in mixing water and made into a slurry state can be added when mixing concrete. . Among them, considering the handling property of promoting the hardening promoting action and weighing and inputting to the mixer, concrete is prepared by suspending slaked lime or thiosulfate in a part of the mixing water at a concentration that does not separate into concrete. The method of adding when mixing is more preferable.

In the present invention, no special method is required for adding and mixing to concrete, and a conventional mixer is used and a hardening accelerator is added to the mixer together with other concrete materials. It can be mixed at the mixing time.

[0015]

EXAMPLES The present invention will now be described in detail with reference to examples, but the invention is not limited thereto.

Example 1 700 g of commercially available early-strength Portland cement, 1120 g of river sand from Himekawa, Niigata, 200 g of water, and 10 g of high-performance water-reducing agent stock solution (polyalkylallyl sulfonate type) in 100 g of cement were used. The slaked lime and thiosulfate were added in different types and blending ratios. The slaked lime, thiosulfate and the like were lightly mixed into the cement in a powder state, and added to the outer portion (added in place of sand) and kneaded. The kneaded mortar was molded into a triple mold of 4 × 4 × 16 cm, and the strength was measured for standard age 1 day (1 piece) and 28 days (2 pieces). The method of mixing the mortar, molding the sample, and measuring the compressive strength was based on the physical test method for cement according to JIS R5201. The formulations of slaked lime and thiosulfate and the measurement results are shown in Tables 1, 2 and 3.

"Materials used""Slakedlime": Gas-fired quick lime digested, Ca
Content of (OH) ₂ is 98% by mass A-1: Blaine specific surface area 3200 cm ² / g A-2: Blaine specific surface area 5110 cm ² / g A-3: Blaine specific surface area 6090 cm ² / g A-4: Blaine ratio Surface area 8120 cm ² / g “Thiosulfate etc.” B: Anhydrous sodium thiosulfate, industrial commercial product C: Calcium formate, industrial commercial product D: Calcium nitrate, industrial commercial product E: Sodium nitrate, industrial commercial product F : Calcium nitrite, reagent G: potassium aluminate, industrial commercial product (comparative example) H: magnesium sulfate, industrial commercial product (comparative example) "Cement brand" a: a company a early strength Portland cement b: b company Early strength Portland cement c: Company c Early strength Portland cement d: Company d Early life Portland cement e: Company a Normal portland cement

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

From Table 1, the mass ratio of slaked lime to thiosulfate is more than 97/3, and the amount of slaked lime is less than that of thiosulfate, or less than 5/95. The expression of 1-day intensity was small even when
It can be seen that the 1-day strength is remarkably increased in the range of the mass ratio of / 3 to 5/95, more preferably 96/4 to 10/90, and further preferably 95/5 to 20/80.
(Experiments No.1-2 to No.1-22). Also, from Tables 1 and 2, the alkali metal salt and the alkaline earth metal salt tend to have a higher 1-day strength than the alkali metal salt, but the 28-day strength is higher than the alkaline earth metal salt. Can be understood (Experiment No. 1-3
~ No. 1-12, Experiment No. 1-14 ~ No. 1-22, Experiment No. 2-3 ~ No. 2-
12). Furthermore, with accelerators and quick-setting agents other than the thiosulfate of the present invention, the combined effect with slaked lime is not shown (Experiment No. 2-
17, No. 2-18). The daily strength of the slaked lime gradually increases as the fineness increases, but when the fineness exceeds 5000 cm ² / g, it almost reaches saturation (Experiment No. 1-18, No. 2-14 to No. 2-1).
6). From Table 3, the addition amount of the hardening accelerator to 100 parts by mass of cement increases the 1-day strength at 0.2 parts by mass or more, but when it exceeds 10 parts by mass, the 1-day and 28-day strengths also decrease sharply. Therefore, further addition is expected to reduce the strength. Therefore, it is preferably 0.5 to 8 parts by mass, more preferably 1 to 6 parts by mass (Experiment No. 3-1).
~ No.3-8). Depending on the brand of cement, a combination of ordinary curing accelerators such as thiosulfate or thiosulfate and formate may or may not show a curing acceleration effect, and some brands may have reduced strength. However, when combined with the slaked lime of the present invention, a stable strength promoting effect is obtained regardless of the brand (Experiment No. 3-9 to No. 3-21).

Example 2 Experiment No. 1-1 to No. 1-12 and No. 3-1 to No. 3-8 of Example 1 were set to have an air content of 2% (volume) and 1 m ³ . Table 4 shows the results obtained by mixing concrete with coarse aggregate (gravel having a maximum size of 25 mm) in such a manner that kneading was performed to prepare a test piece, and measuring the strength at 1-day and 28-day age in standard curing. The slaked lime, thiosulfate and the like were lightly mixed into cement in a powder state and kneaded by adding an outer split. In addition, I did not adjust the slump by adding water to keep the water ratio unchanged.
The slump was in the range of 5-12 cm. The method for producing the specimen and the method for measuring the strength are described in JIS A 1132 and JIS.
According to A 1108.

[0023]

[Table 4]

From Table 4, it can be seen that the concrete strength is almost the same as the mortar strength.

Example 3 Experiments No. 4-13 to No. 4-20 of Example 2 were carried out by mixing slaked lime and thiosulfate with a part of the water and mixing them when mixing the concretes. The same test as in Example 2 was performed. The results are shown in Table 5.

[0026]

[Table 5]

From Table 5, the curing accelerator of the present invention exhibits higher strength when it is suspended and added as a slurry than when it is added as a powder (Experiments No. 4-13 to No. 4-20, No.5-1 ~ No.
5-8).

Example 4 The high-strength Portland cement of Company a of Experiment No. 4-1 and Experiments No. 4-13 to No. 4-20 of Example 2 was changed to ordinary Portland cement of Company a and mixed. Horizontal type φ10
Molded in a capless formwork of × 20 cm, 1 at 20 ℃
After curing for an hour, cure at 45 ° C for 1 hour, then 70
Table 6 shows the demolding strength after steam curing at 2 ° C. for 2 hours, removal after standing for 0.5 hour cooling, and strength after 7 days of air drying curing at 20 ° C. in a room. The slaked lime, thiosulfate and the like were lightly mixed into cement in a powder state and kneaded by adding an outer split.

[0029]

[Table 6]

From Table 6, as in the case of standard curing, the curing accelerator shows the effect of the addition rate with respect to the demolding strength even when steam curing, and the strength does not decrease so much even if the addition amount increases, but the material ages 7 days. It can be seen that the strength decreases when the addition amount of the hardening accelerator to 100 parts by mass of cement exceeds 8 parts by mass, and further decreases when it exceeds 10 parts by mass.

[0031]

EFFECTS OF THE INVENTION By using the cement hardening accelerator of the present invention, a stable hardening promoting action is obtained regardless of the type and brand of cement, and early strength is increased. Similar early strength development can be obtained in steam curing. When used for civil engineering structures, it takes less time to splice, which allows economical and rational construction. Rational production planning can be done at the concrete product factory. And other effects.

Claims (3)

[Claims] 1. A hardening accelerator comprising slaked lime and at least one selected from thiosulfates, formates, nitrates and nitrites. 2. A blending ratio of slaked lime and at least one selected from thiosulfates, formates, nitrates and nitrites in a mass ratio of 97/3 to 5/95. Item 1. A curing accelerator according to item 1. 3. The method according to claim 1, with respect to 100 parts by mass of cement.
Alternatively, a cement composition comprising the curing accelerator of 2 in an amount of 0.2 to 10 parts by mass.