JP3040985B1 - Low heat generation type early strength cement and low heat generation type early strength concrete - Google Patents

Abstract

An object of the present invention is to provide a low heat generation type early-strength cement which has a small temperature rise when mass concrete is used, and has an early strength development of 7 days of material age equal to or more than that of using early-strength Portland cement. In addition, in combination with the low heat-generating type early-strength cement, the present invention provides concrete with improved early strength at 7 years of age, increased adiabatic temperature, and the like. SOLUTION: This invention provides a low heat generation type early-strength cement comprising a mixture of 75-90% by weight of early-strength Portland cement and 10-25% by weight of high-belite cement. Limestone powder can be added to the cement. In addition, it is preferable to mix concrete with a high-performance AE water reducing agent containing a sulfonate as a main component or an accelerator containing a nitrogen-based inorganic compound as a main component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low heat type early-strength cement and a low heat type early-strength concrete which require early strength development and minimize the occurrence of temperature cracks. This type of cement and concrete can be applied, for example, to relatively high-strength concrete such as PC girder during winter construction and small-scale mass concrete members.

[0002]

2. Description of the Related Art So-called early strength Portland cement is
It has been used for the purpose of securing early strength at the time of construction in winter and shortening the period of staying formwork. On the other hand, in the “Chapter 17 Mass Concrete” of the Japan Society of Civil Engineers Standard Standard Construction Book enacted in 1996, the formula for calculating the adiabatic temperature rise of concrete using early-strength Portland cement was described for the first time. Examples of application to mass concrete, which is a problem, have increased. In order to minimize the temperature cracks in such members and to secure the required durability, conventionally, measures such as carefully performing curing (watering curing, mat curing) and the like have been taken exclusively in construction. Was.

[0003]

In the prior art, there has been no development or invention of a cement composition which focuses on essentially suppressing the heat generated by hydration of the cement while maintaining the early strength. . For this reason, there has been no other choice but to take measures against temperature cracks during the construction. Therefore, the cost of measures for controlling the temperature crack has increased, and the cost has been increased due to the extension of the construction period. In addition, in order to obtain high-strength concrete, it is necessary to increase the amount of cement. However, in this case, a vicious cycle has been caused in that the calorific value of the concrete further increases.

[0004] Therefore, there is a demand for a low heat generation type early-strength cement that reduces the heat of hydration of the early-strength Portland cement itself and has an early strength development property equal to or higher than that of the early-strength Portland cement.

[0005] An object of the present invention is to provide a mass concrete having a temperature rise smaller than that of the early-strength Portland cement, and having an early strength development at 7 days of age equal to or greater than that of the early-strength Portland cement. An object of the present invention is to provide a heat-generating type early-strength concrete, and to provide a low heat-generating type early-strength concrete capable of satisfying the design standard strength of a 7-year-old road specification by minimizing the amount of cement as much as possible.

[0006]

SUMMARY OF THE INVENTION The present invention is characterized in that it comprises a mixture of 75-90% by weight of early-strength Portland cement and 10-25% by weight of high-belite cement, and has a low heat generation type of early-strength. It relates to cement. Also,
The present invention relates to a low-heating type early-strength cement comprising the low-heating type early-strength cement and limestone powder.

[0007] The present invention also provides a low heat-generating type early-strength cement comprising any one of the above-mentioned low heat-generating type early-strength cements and a high-performance AE water reducing agent containing a sulfonate as a main component. It is related to strong concrete.

[0008] Further, the present invention provides a low heat generation type early-strength concrete, wherein any of the above-mentioned low heat generation type early-strength cements and an accelerator mainly containing a nitrogen-based inorganic compound are mixed. It is related to.

The inventor of the present invention has found that by mixing 10 to 25% by weight of high-belite cement with 75 to 90% by weight of early-strength Portland cement, it is possible to increase the mass concrete compared to the case of the early-strength Portland cement alone. In addition to the fact that the temperature rise in the case of the above can be reduced, it has been found that an early strength exceeding that in the case of using the early strength Portland cement is exhibited. Since high-belite cement is a cement with low early strength, such effects have been surprising and unforeseen by those skilled in the art.

Accordingly, the present invention has succeeded in providing a low heat-generating type early-strength cement which exhibits strength higher than that of early-strength portland cement at an early stage and hardly causes temperature cracking.

In "Characteristics of Belite Cement Mixed with Ordinary or Early-Strength Cement" (Concrete Engineering Annual Report, Vol. 18, No. 1, 1996), 20 and 30 are added to belite cement. , 40% by weight of early-strength Portland cement can be used to improve the early strength of belite cement at low temperatures. However, in this document,
It has been described and suggested that the addition of a small amount of high-belite cement mainly containing early-strength Portland cement improves the early strength of concrete beyond that of early-strength Portland cement, and reduces the adiabatic temperature rise. Not.

Hereinafter, the present invention will be described more specifically. Early strength Portland cement is 60-70% by weight of 3Ca
O · SiO ₂ , 5-15% by weight of 2CaO · SiO ₂ ,
5-15% by weight of 3CaO.Al ₂ O ₃ , 5-15% by weight of 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ , and 4-6
Preferably contains a weight% of gypsum _{(CaSO 4 · 2H 2 O)} , Blaine specific surface area 3000-6000Cm ²
/ G is preferred.

[0013] The high belite cement is described in JIS R5201 in 1997 as low heat Portland cement. As for the fresh properties of concrete using high belite cement, the fluidity of the paste is higher, the pumping performance is excellent, and the ultimate adiabatic temperature rise is higher than that of ordinary Portland cement or concrete using early-strength Portland cement. Has decreasing properties. However, there are concerns about the extension of the construction (curing) period due to the delay in strength development at the early age, and the durability when exposed to use conditions from a young age.

The high belite cement comprises 15-40% by weight of 3CaO.SiO ₂ , 75-45% by weight of 2CaO.
· SiO _2, 0-6 _{wt% 3CaO · Al 2 O 3,} 0
-12% by weight of _{4CaO · Al 2 O 3 · Fe} 2 O 3, and preferably contains 3-7 weight% gypsum _{(CaSO 4 · 2H 2 O)} , Blaine specific surface area 2500-40
Those having a size of 00 cm ² / g are preferred.

The proportion of high belite cement is 10% by weight.
As described above, by setting the content to 25% by weight or less, the early strength of the cement of the present invention exceeds the early strength of the early-strength Portland cement. Furthermore, it was found that the adiabatic temperature rise of the cement of the present invention was clearly improved as compared with the adiabatic temperature rise of the early-strength Portland cement.

From the viewpoint of further reducing the adiabatic temperature rise, the proportion of the high belite cement is more preferably 15% by weight or more, and even more preferably 20% by weight or more.

Limestone powder is added to the cement of the present invention.
And thus a low heat generation type high strength filler
Can provide cement, lower heat generation due to filler effect
Can improve sex and early strength. Limestone powder
Limestone powder for cleat admixtures is preferred. Its composition
Is preferably CaCO 2_ThreeWith a purity of 90% by weight or more
And 5% by weight or less of MgO and SO_ThreeIs 0.5 weight
% Or less, and AlO _ThreeIs 1.0% by weight or less.
The limestone powder preferably has a moisture content of 1.0% by weight or less.
And the methylene blue adsorption amount is 1.0 mg / g or less.
Preferably, the plane specific surface area is 2500 cm^Two
/ G or more. Limestone powder addition amount and
Then, 100 parts by weight of the low heat type early-strength cement of the present invention
On the other hand, it is preferable to add 1 to 15 parts by weight. 1 weight
If less than 15 parts by weight, the effect of improving early strength is poor, and 15 parts by weight
This is because if it exceeds, the long-term strength decreases.

The cement of the present invention can be mixed with a high-performance AE water reducing agent containing a sulfonate as a main component. Thereby, the initial strength of the concrete can be further improved, and the amount of increase in the adiabatic temperature can be further reduced. This is an effect of improving the early strength of concrete, especially when using the cement of the present invention, in concrete containing a large ratio of water cement (the ratio of cement is small), as compared with the use of high-strength Portland cement alone. This is because the water-cement ratio for obtaining the required early strength increases, and as a result, the unit cement amount of concrete can be reduced.
In addition, it has been found that such an effect is more excellent in the high-performance AE water reducing agent containing a sulfonate as a main component than in other types of generally used high-performance AE water reducing agents. . The amount of the high-performance AE water reducing agent containing a sulfonate as a main component is preferably 0.5 to 2.0 parts by weight based on 100 parts by weight of the cement of the present invention. If the amount is less than 0.5 part by weight, the water reducing effect is small, and even if the amount exceeds 2.0 parts by weight, the above-mentioned effects are leveled off and remain unchanged.

Further, an accelerator containing a nitrogen-based inorganic compound as a main component can be mixed with the cement of the present invention. Thereby, the early strength of the concrete can be further improved, and the rise in the adiabatic temperature can be further reduced. This is similar to the case of the high-performance AE water reducing agent containing a sulfonate as a main component. Compared to the use of concrete, the effect of improving the early strength of the concrete is large, which increases the water-cement ratio for obtaining the required early strength, and as a result, the unit cement amount of the concrete can be reduced. is there. In addition, the mixing amount of the accelerator containing the nitrogen-based inorganic compound as a main component is based on 100 parts by weight of the cement of the present invention.
0.5-1.5 parts by weight is preferred. If the amount is less than 0.5 part by weight, the accelerating effect is small, and if it exceeds 1.5 parts by weight, the strength tends to be adversely affected.

The sulfonate is preferably a polyalkylallyl sulfonate, a naphthalene sulfonate, or an alkylallyl sulfonate-modified lignin copolymer, and particularly preferably a polyalkylallyl sulfonate.

As the high-performance AE water reducing agent containing the polyalkylallyl sulfonate as a main component, commercially available “Mighty 2000S”, “Mighty 2000R” and “Mighty 2000WH” (Kao Corporation, Yamasou Chemical Co., Ltd.)
Is particularly preferred.

[0022] Accelerators are admixtures that promote the setting and hardening of concrete. As the nitrogen-based inorganic compound, nitrates, nitrites, and thiocyanates are preferable, and calcium salts thereof are particularly preferable.

[0023]

EXAMPLES (Experiment A) Table 2 shows the results of the measurement of the strength development under standard underwater curing using concrete of each mixing ratio and composition shown in Table 1. However, each formulation N
o. In Examples 1, 2, and 3, as the admixture, a commonly used polycarboxylic acid ether-based high-performance AE
A water reducing agent was used.

[0024]

[Table 1]

[0025]

[Table 2]

As can be seen from the results in Table 2, the compressive strength of the cements 2 and 3 according to the present invention at the age of 7 days is as follows:
Since it exceeded the value of the early strength Portland cement which should be a reference, it was found that it had excellent properties in early strength development.

(Experiment B) It was measured how the mixing ratio of the high belite cement to the early strength Portland cement affects the compressive strength of concrete at the age of 7 days. Formula A of Experiment A Based on the concrete compounding of 40% water cement ratio using the early-strength Portland cement of 1-, the concrete cast by changing the proportion of the early-strength Portland cement and the proportion of the high belite cement as shown in Table 3 Cured in the same manner as in Experiment A. About each concrete, the compressive strength at the age of 7 days was measured, and the measurement results are shown in Table 3. From these results, at 7 days of age, 5% of high belite cement was added.
It was found that the compressive strength of the obtained concrete clearly exceeded the compressive strength of the concrete using the early-strength Portland cement by adding at least 10% by weight, more preferably at least 10% by weight.

[0028]

[Table 3]

(Experiment C) It was measured how the mixing ratio of the high belite cement to the early strength Portland cement affects the adiabatic temperature rise. Formula A of Experiment A The ratio of the early-strength Portland cement and the ratio of the high-belite cement were changed as shown in Table 3 based on the concrete mixture of 40-% water-cement using 1-high-strength Portland cement as shown in Table 3 (however, high belite was used). (Excluding the composition with 1% by weight of cement)
The adiabatic temperature rise of the cast concrete was measured, and the measurement results are shown in FIG. As a result, the amount of temperature rise was flat after 10 days, and 5% by weight of high-belite cement was added to the early-strength Portland cement more than that of the early-strength Portland cement alone. It has been found that, while the amount of temperature rise is increased, the amount of adiabatic temperature rise can be clearly reduced by adding 10% by weight or more of high belite cement.

As described above, even if 5% by weight of a low heat-generating high belite cement is added, the amount of temperature rise does not decrease and 1%.
It is impossible for a person skilled in the art to predict that the temperature rise is reduced only when 0% by weight is added. These results, combined with the strength test results of Experiment B, support that the optimum addition amount of the high belite cement to the early-strength Portland cement is 10% by weight or more and 25% by weight or less.

(Experiment D) In Experiment A, the composition N
o. 75 parts by weight of early Portland cement of No. 2: 100 parts by weight of cement composition of 25 parts by weight of high belite cement and 0.6 parts by weight of a high-performance AE water reducing agent (based on polyalkylallyl sulfonate as a main component) ) Or concrete mixed with 1.5 parts by weight of an accelerator mainly composed of calcium nitrite, and the early strength under standard underwater curing was measured. Table 4 shows the measurement results.

[0032]

[Table 4]

As can be seen from Table 4, a high performance AE water reducing agent containing polyalkyl sulfonate as a main component or an accelerator containing calcium nitrite as a main component is mixed with concrete using the cement of the present invention. By,
Nos. In Tables 1 and 2 Compared to the case where a concrete using the cement of the present invention, which is a concrete compound of 2-, is mixed with a generally used high-performance AE water reducing agent containing a polycarboxylic acid ether as a main component, the material is 7 days old. Not only the early strength but also the strength at the age of 28 days was significantly improved.

Next, the water-to-cement ratio satisfying the specifications of the road specification was determined for the cement of the present invention and the early strength Portland cement alone. The method of finding is to obtain in advance a correlation equation between the water-cement ratio and the compressive strength at the age of 7 days for each cement, and from this correlation equation, determine the water equivalent to the required specification (compressive strength value at the age of 7 days). This was performed by a method for determining the cement ratio. Furthermore, set the unit water volume (158k
g / m ³ ) and the unit cement amount. Table 5 shows the results.
Shown in

[0035]

[Table 5]

It should be noted that, for concrete having a design standard strength of 40 N / mm ² described in the road specification, if the age of the introduced material for prestressing is 3 days, 32 N at the age of 3 days.
/ Mm ² is required, and if the material age that satisfies the design standard strength is 7 days, 50 N / mm
A compressive strength of ² (assuming a premium factor of 1.25) is required.

The water-cement ratio that satisfies the required strength of the concrete having the design standard strength of 40 N / mm ² at the age of 7 days is determined by the formulation No. of the present invention. 2-49.4%, Formulation N
o. No. 2 was 47.0%, which was mixed with a high-performance AE water reducing agent containing polycarboxylate ether as a main component.
The water-cement ratio is significantly higher than that of 2-.
In addition, Compound No. 1-
And a water cement ratio of 44.1%. 1-
It was found to exceed each of the water cement ratios of 46.2%. In the case of a high-performance AE water reducing agent containing a polyalkyl sulfonate as a main component, the effect is particularly remarkable.
Therefore, the formulation No. In 2- and 2-, while achieving the required strength, the water-cement ratio can be greatly increased, and as a result, the amount of unit cement is reduced. Resistance can be further improved.

[0038] The above description indicates that the low heat generation type early-strength cement of the present invention can be used in combination with a high performance AE water reducing agent containing polyalkyl sulfonate as a main component or an accelerator containing calcium nitrite as a main component. In particular, concrete having a high water-cement ratio is caused by a large elongation of strength, and it is nothing but a remarkable effect of this combination.

(Experiment E) Formulation No. 1-, 2-
, 2-, 2- and limestone powder as another cement of the present invention (75 parts by weight of early strength Portland cement, 20 parts by weight of high belite cement, 5 parts by weight of limestone powder). Using 3-, the adiabatic temperature rise (° C.) of the concrete was measured, and the measurement results are shown in FIG.

As can be seen from FIG. 2, the cement according to the present invention was formulated using the conventional No. Portland cement. In comparison with No. 1- For Nos. 2 and 3, about 4-6 ° C. 2-, 2- is about 10-1
2 ° C. (ie, about 6-20% of the ultimate adiabatic temperature rise for Formulation No. 1), it is possible to reduce the adiabatic temperature rise, thus improving the resistance to thermal cracking.

That is, the concrete using the low heat generation type early-strength cement of the present invention has a lower adiabatic temperature rise amount than the concrete using the early-strength Portland cement. The concrete mixed with the high performance AE water reducing agent based on the polyalkyl sulfonate of the present invention or the accelerator based on calcium nitrite using the cement of the present invention is a polycarboxylic acid generally used. The effect of the combination that the amount of adiabatic temperature rise can be further reduced compared to concrete mixed with a high-performance AE water reducing agent containing ether as a main component is also recognized.

(Experiment F) Formulation No. For each of the cements 1 and 2, concrete was obtained using the respective formulation examples in Table 6,
The relationship between the elapsed time of each concrete and the auto-shrinkage strain was measured. The result is shown in FIG. In FIG. 1-
And No. As can be seen from the comparison with 2-, when the cement of the present invention is used, the autogenous shrinkage strain of the concrete is remarkably improved as compared with the use of the conventional high-strength Portland cement. In addition, No. 2- and No. 2-
As can be seen from the comparison with the concrete, the high-performance AE water reducing agent containing a polyalkylsulfonic acid salt as a main component of the present invention is mixed with a generally used high-performance AE water reducing agent containing a polycarboxylic acid ether as a main component. The self-shrinkage strain is improved as compared with the mixed concrete, and the effect of the combination with the cement of the present invention is also confirmed from this experimental result.

[0043]

[Table 6]

[0044]

As described above, the low heat generation type early-strength cement of the present invention has a small temperature rise when mass concrete is used, and has an early strength of 7 days of age that exceeds the case of using early-strength Portland cement. It has expressibility. Further, by combining with a high-performance AE water reducing agent containing a sulfonate as a main component or an accelerator containing a nitrogen-based inorganic compound as a main component, the compressive strength of a 7-year-old material can be increased particularly when the water-cement ratio is large. Is large, the water-cement ratio for obtaining the compressive strength of 7 days of age that satisfies the design standard strength of the road specification is increased, and as a result, the unit cement amount is reduced. Can be. The self-shrinkage strain of the concrete using the cement of the present invention is smaller than that of the case of using the early-strength Portland cement. Shrinkage strain can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the measurement results of the adiabatic temperature rise when the replacement mixture ratio of high belite cement to early-strength Portland cement is changed between 0-30% by weight.

FIG. 2 shows the composition No. of the comparative example. No. 1 and formulation No. 1 within the scope of the present invention. It is a graph which shows the measurement result of adiabatic temperature rise about 2-, 2-, 2-, and 3-.

FIG. 3 shows composition No. of Comparative Example. No. 1 and formulation No. 1 within the scope of the present invention. It is a graph which shows the measurement result of self-shrinkage strain about 2- and 2-.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C04B 24:22 22:08) 111: 76 (72) Inventor Yuichi Odabe 585 Tomimachi, Funabashi-shi, Chiba Sumitomo Osaka Cement Co., Ltd. Cement・ Concrete Research Institute (56) References JP-A-8-175854 (JP, A) JP-A-5-70192 (JP, A) JP-A-7-277803 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C04B 7/02 C04B 7/345

Claims (4)

(57) [Claims] 1. A low heat type early-strength cement comprising a mixture of 75-90% by weight of early-strength Portland cement and 10-25% by weight of high-belite cement. 2. A low heat generation type early-strength cement comprising the low heat generation type early-strength cement according to claim 1 and limestone powder. 3. A low heat generation type early strength cement comprising a low heat generation type early strength cement according to claim 1 and a high performance AE water reducing agent containing a sulfonate as a main component. concrete. 4. A low-heating type early-strength concrete, wherein the low-heating type early-strength cement according to claim 1 or 2 is mixed with an accelerator mainly composed of a nitrogen-based inorganic compound.