JP3485122B2 - Cement composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seawater-resistant cement composition for producing hardened cement paste, such as cement paste, mortar and concrete, which has excellent resistance to seawater erosion.

[0002]

BACKGROUND OF THE INVENTION The following compositions have been conventionally proposed as seawater-resistant cements. For example, JP-A-49
No. 51312, 3C in cement
aO ・ Al ₂ O ₃ (C ₃ A) amount and 4CaO ・ Al ₂ O ₃
There is a technique of firing the cement clinker by limiting the amount of Fe ₂ O ₃ (C ₄ AF) and adding a small amount of flux.

Further, as disclosed in Japanese Examined Patent Publication (Kokoku) No. 57-10055, the weight ratio of both C ₃ A and C ₄ AF is regulated together with the limitation of the amount of C ₃ A and ₃ CaO.SiO ₂ (C ₃ S).
There is a technique of preparing cement by adding activated siliceous fine powder and a large amount of gypsum to a cement clinker containing 60% by weight or more of cement. Further, as disclosed in Japanese Examined Patent Publication No. 56-31296, the content of blast furnace slag and gypsum in each cement in a cement clinker containing 60 to 70% by weight of C ₃ S and 4% by weight or less of C ₃ A. Of 60 to 70% by weight and 3.0 to 4.5% by weight in terms of SO ₃ are added to prepare cement.

By the way, the techniques disclosed in Japanese Patent Laid-Open No. 49-51312 and Japanese Patent Publication No. 57-10055 are C
_In order to solve the difficulty of firing caused by the decrease in the amount of liquid phase in the clinker accompanying the decrease in the amounts of ₃ A and C ₄ AF, a flux is incorporated. However, the addition of CaF ₂ (fluorite), which is usually used as a flux, decomposes and melts in the low temperature range CaO-SiO ₂ -Ca.
In the kiln with the new suspension preheater, which is the mainstream of the current firing mode, the cyclone of the preheater is clogged because of the formation of the F ₂ compound, which often causes a problem in continuous stable operation. In addition, the addition of flux requires the installation of new supply equipment in the raw material crushing process.

Under these circumstances, a seawater-resistant cement which can be produced without using flux has been desired.
In addition, the technique of Japanese Patent Publication No. 56-31296 is a cement in which a large amount of blast furnace slag is mixed, such as 60 to 70% by weight, so that the progress of neutralization of concrete is fast,
There was a problem in terms of durability, such as corrosion of the reinforcing bars of reinforced concrete structures.

Therefore, there has been a demand for seawater-resistant cement made of Portland cement which does not contain blast furnace slag or blast furnace cement having a small amount of blast furnace slag mixed therein.

[0007]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a cement composition which is rich in seawater and does not contain flux and does not contain blast furnace slag or has a small amount of blast furnace slag. This object of the present invention is a composition of cement produced without using a flux,
_{3CaO · SiO 2, 2CaO · SiO} 2, 3CaO ·
Al ₂ O _3, comprising a compound composition of _{4CaO · Al 2 O 3 · Fe} 2 O 3 ( _{where, 4CaO · Al 2 O 3 ·} Fe 2 O
Excluding those in which ₃ is 7% by weight or less. ) , SiO
The weight ratio of ₂ and Al ₂ O ₃ is 8 or more, and 3CaO ・ Si
_{O 2, 2CaO · SiO 2,} 3CaO · Al 2 O 3 and 3CaO · SiO ₂ 20 to 45 parts by weight per 100 parts by weight of _{4CaO · Al 2 O 3 · Fe} 2 O 3, 2C
Achieved by a cement composition, characterized in that the proportion of aO.SiO ₂ is 45 to 72 parts by weight.

Particularly, 3CaO / SiO₂, 2CaO ・ S
iO₂, 3CaO ・ Al₂O₃, 4CaO / Al₂O₃
・ Fe₂O₃A compound composition of
₂And Al₂O₃Characterized in that the weight ratio with
It is achieved by the cement composition. In addition, this
Ment composition (especially seawater resistant cement composition)
And 3CaO / SiO₂, 2CaO / SiO₂, 3Ca
O ・ Al₂O₃And 4CaO ・ Al ₂O₃・ Fe₂O₃
When the total amount of Fe is 100 parts by weight, Fe₂O₃Is 2.
It is preferably from 0 to 4.2 parts by weight.

The addition of 5 to 60% by weight of blast furnace slag becomes more preferable.

The present invention will be described in detail below. For the erosion of hardened cement by seawater, chloride ion (Cl
^- ) And sulfate ion (SO ₄ ^2- ). Chlorine ion reacts with calcium hydroxide (Ca (OH) ₂ ) which is a hydration product of C ₃ S or 2CaO · SiO ₂ (C ₂ S) to generate calcium chloride (CaCl ₂ ) having a high solubility. It is believed that the leaching causes the cured body to become porous and deteriorate.

Sulfate ions react with hydrates of C ₃ A and C ₄ AF and calcium hydroxide to react with ettringite (C).
_{3 A · 3CaSO 4 · 32H 2} O) to generate, by volume expansion at this time, the cured body is inflated, it is thought to disintegrate. Incidentally, C ₄ AF are sulfate resistance is greater than C ₃ A, seawater resistance C ₃ reported that similarly small and A there.

Therefore, in order to obtain a cement composition excellent in seawater resistance, the amount of calcium hydroxide produced is small and C ₃
It will be sufficient if the content of A or C ₄ AF is small. By the way, the present invention does not use a flux in order to enable production of a clinker by continuous stable operation,
Moreover, for the purpose of improving the durability of hardened cement such as concrete, a seawater-resistant cement composition having a slow neutralization rate was developed.

In Japanese Patent Publication No. 57-10055, the compounds C ₃ A and C ₄ which are compounds susceptible to seawater erosion.
Although the total amount of AF is set to 10% by weight or less, a cement clinker containing at least 60% by weight of C ₃ S is used as a constituent component of the seawater-resistant cement, and the fourth column, the fourth to the fifteenth columns of the publication.
As described in the first line, it is essential to use an inorganic flux (flux) represented by CaF ₂ (fluorite) in firing the clinker. The reason why a flux is required in this technique is that by reducing the content of C ₃ A and C ₄ AF, the amount of liquid phase in the clinker firing is reduced, and the formation reaction of cement compounds, especially C ₃ S is hindered. This is because the reaction CaO, that is, the amount of free CaO, increases, and it becomes difficult to produce high-quality cement.

On the other hand, the present inventor has found that the formulation containing a small amount of C ₃ A and C ₄ AF is used for the purpose of producing a cement excellent in seawater resistance without using a flux. As a result of research on the chemical composition that makes it possible to burn a clinker with a small amount of CaO, and the cement that uses it has excellent seawater resistance, SiO ₂ and Al ₂ O in the chemical components in the cement were found.
₃ and the weight ratio of _{(SiO 2 / Al 2 O 3} , activity factor) the desired physical properties as those higher came to find that there tends to be obtained.

As a result of further examination, C ₃ S, C ₂ which is a constituent compound of cement (Portland cement).
The composition ratio of S, C ₂ A, C ₄ AF is optimized, and the activity coefficient is 8 or more, preferably 8 to 15, more preferably 8 to 1.
3, particularly preferably 9-12 cement (Portland cement) is extremely excellent in seawater resistance and free C
It has been found that it can be a high-quality cement with low aO.

That is, the Portland cement having an activity coefficient of less than 8 had a large decrease in strength of the cement hardened body due to seawater curing and was inferior in seawater resistance. Conversely, Portland cement with an activity coefficient of more than 15 is Al ₂ O.
_{3 The} amount was small, the amount of liquid phase in the clinker was small, the clinker did not become agglomerates, but became fine particles or powder, and there was a tendency that it was difficult to operate the rotary kiln and clinker cooler stably.

The coefficient of activity of conventional cement is
As shown in Table A below, it is approximately 2.5 to 6.0. Table A Portland chemical composition (%) Activity coefficient Cement type SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO SO ₃ Normal 22.0 5.2 3.0 64.3 2.0 4.23 Early strength 20.9 4.8 2.8 65.1 2.8 4.35 Super early strength 20.0 4.9 2.7 65.3 3.6 4.08 Moderate heat 23.5 4.1 4.0 63.7 1.8 5.73 Sulfate resistant 22.5 3.5 4.3 64.8 1.8 6.43 White 23.3 4.7 0.2 66.1 2.4 4.96 ASTM standard type IV 24.0 4.4 3.9 61.0 1.9 5.45 Furthermore, the activity coefficient is in the range of 8 to 15, And Fe ₂ O ₃ / in the chemical composition of Portland cement
(C ₃ S + C ₂ S + C ₃ A + C ₄ AF) (hereinafter Fe ₂
O ₃ ratio) is from 2.0 to 4.2 wt%, more preferably 2.2 to 3.8 wt%, particularly preferably 2.3 to 3.5
It has also been found preferable to be in the range of weight percent. That is, when the Fe ₂ O ₃ ratio is out of the above range, C ₄ AF / (C ₃ S calculated by the Borg equation is used.
+ C ₂ S + C ₃ A + C ₄ AF) is 6% by weight or less or 12% by weight or more. In the former case, it is not possible to produce a high-quality cement with free CaO in the clinker of 1% by weight or less, and in the latter case. Seawater resistance deteriorated.

According to the present invention, a good quality Portland cement having excellent seawater resistance and less free CaO was obtained without using flux. The reason is considered as follows. It was First, the reason why the cement composition of the present invention has excellent seawater resistance is
By making O ₂ / Al ₂ O ₃ larger than ordinary cement, the amount of Al ₂ O ₃ for SiO ₂ content is reduced, and the compound is inferior in seawater resistance to C ₂ S, which is a compound excellent in seawater resistance. It was understood that the ratio of C ₃ A and C ₄ AF was small. Also, since the amount of C ₂ S, which is a compound containing a large amount of solid solution components, increases, Al ₂ O which forms a solid solution with this
₃ and Fe ₂ O ₃ content increased, and C ₃ A and C ₄ AF
It was understood that the actual amount of water was less than that calculated by the Borg equation, which further improved the seawater resistance.

Next, the reason why it is possible to obtain a high-quality cement with a small amount of free CaO without using a flux is that SiO ₂ / Al ₂ O ₃ is high.
It can be mentioned that the amount of C ₂ S relative to C ₃ S tends to increase. That is, C ₃ S is a compound whose generation rate is extremely slow when the amount of liquid phase is small, but C ₂ S is a compound which is sufficiently generated by solid phase reaction even in the absence of liquid phase, With less C ₃ S and more C ₂ S than cement, C ₃ A and C
₄ It was understood that a good quality clinker with a small amount of free CaO can be baked even with a small amount of AF.

C ₂ S produces less calcium hydroxide (Ca (OH) ₂ ) which is corroded by chloride ions than C ₃ S, as shown by the following hydration reaction formula.
₂ S intensive cement, becomes excellent in seawater by this. 2 (2CaO ・ SiO ₂ ) + 4H ₂ O → 3CaO ・ 2S
iO ₂ · 3H ₂ O + Ca (OH) ₂ 2 (3CaO · SiO ₂ ) + 6H ₂ O → 3CaO · 2S
iO ₂ · 3H ₂ O + 3Ca (OH) ₂ Next, in the compound composition of cement, 3CaO · Si
_{O 2, 2CaO · SiO 2,} 3CaO · Al 2 O 3 and 3CaO · SiO ₂ 20 to 45 parts by weight per 100 parts by weight of _{4CaO · Al 2 O 3 · Fe} 2 O 3, 2C
The reason why the ratio of aO.SiO ₂ is 45 to 72 parts by weight is to make a more preferable cement in consideration of strength development when a general-purpose seawater-resistant cement is manufactured and put into practical use. .

That is, the compounds that contribute to the strength development of cement are mainly C ₃ S and C ₂ S. Then, when the activity coefficient was 8 to 15 and the Fe ₂ O ₃ ratio was about 2 to 3% by weight, the amount of C ₃ S and C ₂ S was changed and the result was examined. As a result, C ₃ S / (C ₃ S + C ₂ S + C ₃ A + C ₄ AF)
(Hereinafter, C ₃ S ratio) is 20 to 45% by weight, C ₂ S /
(C ₃ S + C ₂ S + C ₃ A + C ₄ AF) (hereinafter C ₂ S
If the clinker compound composition is designed so as to obtain cement having a ratio of 45 to 72 % by weight, free CaO
A good quality clinker having a content of 1% by weight or less could be fired, and the cement obtained by adding gypsum to this had good strength development at all ages and was extremely excellent in seawater resistance.

If the C ₃ S content exceeds 45% by weight and is too high, and the C ₂ S content is less than 45 % by weight, which is too low, the reaction rate of C ₃ S is slow with respect to the clinker composition having a small liquid phase. Is too much, the amount of free CaO increases,
It was difficult to obtain good quality cement. Also, C ₃ S
The proportion is too low, less than 20% by weight, and the C ₂ S proportion is
If it exceeds 72 % by weight and is too large, the strength of the initial age of the cured product tends to be extremely reduced. It is considered that this is because C ₃ S has a high hydration activity in the early age and, conversely, C ₂ S is a compound having a low hydration activity in the early age.

From the practical aspects such as the concrete construction speed, the required strength after 3 days of age is 50 kgf / cm.
If it is about ² , the C ₃ S ratio is preferably 20% by weight or more. The C ₃ S ratio is more preferably 22
-42% by weight, particularly preferably 22-37% by weight, C ₂
More preferably, the S ratio is 55 to 72% by weight.

However, when the construction period can be extended, the C ₃ S ratio becomes less than 20% by weight, and the C ₂ S ratio becomes
There is no problem even if it exceeds 72 % by weight. In particular, when constructing a huge mass concrete structure, C ₂ S is a compound having a small amount of heat of hydration and is excellent in strength development in long-term age. In some cases, it is preferable from the viewpoint of preventing the occurrence of cracks due to temperature rise.

Next, by combining the above-mentioned seawater-resistant cement composition with blast furnace slag, a relatively small amount of blast furnace slag is mixed, the seawater resistance is excellent, and the blast furnace cement with a slow neutralization rate is used. We conducted experiments and studies based on the idea that Blast furnace cement, when the mixing ratio of blast furnace slag is 60 to 70% by weight or more,
It is known that the rate of neutralization increases rapidly. Therefore, the blast furnace cement with 60% by weight or less of the cement content after mixing the blast furnace slag was examined.

Conventionally, as described in Japanese Patent Publication No. 56-31296, column 3, line 28 to column 4, line 4, the greater the amount of blast furnace slag mixed in cement, the more chloride is formed. Although the cement has improved resistance to sulphate and has no effect on sulphate resistance and has excellent seawater resistance, when the amount of blast furnace slag mixed is less than 60% by weight, sulphate resistance and chloride resistance It has been said that the water resistance of the seawater deteriorates and the seawater resistance deteriorates.

However, according to the research by the present inventor,
A blast furnace cement excellent in seawater resistance could be obtained with a slag mixing amount of 60% by weight or less. The reason for this is that in the cement (Portland cement) having the above composition, the seawater resistance of itself is improved, so the effect of contributing to seawater resistance is synergistic even if a small amount of slag is added. Thought to appear in.

That is, the amount of blast furnace slag added is 5 to 60.
The cement composition of the present invention, which is used in a weight percentage (desirably 25 to 45 wt%), exhibits even higher strength development in seawater curing, and has excellent overall durability including resistance to neutralization. It can be said to be seawater blast furnace cement. The cement composition of the present invention may be produced by crushing clinker, blast furnace slag and an appropriate amount of gypsum separately, or after crushing in an appropriate combination and then mixing them, or by producing an appropriate amount of clinker and blast furnace slag. It may be produced by adding gypsum and mixing and pulverizing.

In the present invention, gypsum is mixed with SO in cement.
The reason for setting 0.5 to 4.5% by weight in terms of ₃ is as follows. Gypsum is indispensable for normalizing setting and hardening of cement, and is usually added in an amount of 0.5 to 2.5% by weight in terms of SO ₃ in cement.
And the clinker is originally 0.5-1.0 wt% SO.
_{Since 3} minutes are included, the amount of SO _{3 in} the cement is 1.5
It is about 3.5% by weight. Therefore, also in the present invention, the lower limit of the amount of gypsum added is set to 0.5% by weight in terms of SO ₃ in cement.

On the other hand, seawater resistance is
SO₃It is better that the amount, that is, the amount of plaster added, is large to some extent
It is known. In the present invention,
SO ₃Good enough seawater resistance, even if the amount is about 2% by weight
Shows SO, but due to the above reasons, SO₃Sea resistance if the amount increases
It is expected that the water content will be further improved. But Naga
, SO in cement according to Japanese Industrial Standards₃Maximum amount
Even if there are many values, it is 4.5% by weight.
Was selected as 4.5% by weight.

The present invention will be described below with reference to specific examples.

[0032]

[Example] Limestone, depending on the manufacturing equipment of the cement plant,
Add gypsum to a clinker fired using silica stone, a clayey raw material, and an iron oxide raw material as a raw material for compounding, and obtain a fineness of 325.
Seawater resistance test was conducted on Portland cement having the chemical composition and the compound composition (according to Borg formula) of [Table 1] obtained by crushing to 0 to 3450 cm ² / g.

[0033]

[Table 1]

JIS R 5201 is used as the test specimen for the test.
Using a mortar prepared according to the "physical test method for cement", after curing with tap water at a temperature of 20 ° C for 6 days, curing with Kalle's prescription artificial seawater shown in [Table 2] was performed for 1 year. The artificial seawater was replaced with freshly prepared seawater every 2 weeks until the age of 3 months and then every 1 month thereafter.

[0035]

[Table 2]

Since it takes a long period of time to evaluate the resistance to seawater, after curing the artificial seawater for one year, it is possible to dry and wet the artificial seawater soaked at 20 ° C. for 24 hours and dried at 70 ° C. for 24 hours as one cycle. Repeated accelerated seawater resistance test (accelerated test) was performed up to 26 cycles. When the test was interrupted, the dried sample was sealed in a plastic bag and stored in a room at 20 ° C., and the test was continued again from immersion in artificial seawater. or,
The artificial seawater used was replaced with new one every 6 cycles.

Table 3 shows the results of the compressive strength test of the specimens at a predetermined material age.

[0038]

[Table 3]

According to this, the strength of the Portland cement of Example 1 continued to increase up to one year of age by curing in artificial seawater at 20 ° C., and even after the accelerated test, there was no occurrence of cracks or reduction in strength, It can be seen that it shows excellent seawater resistance. On the other hand, the ordinary Portland cement of Comparative Example 1 showed a decrease in strength after 6 months of artificial seawater curing material at 20 ° C., cracking occurred in 13 cycles of the accelerated test, and the seawater resistance was poor. . The sulfate-resistant Portland cement of Comparative Example 2 showed a decrease in strength after one year of curing in artificial seawater at 20 ° C, and the strength gradually decreased in the accelerated test, which also tended to be inferior in seawater resistance. It was

Furthermore, the product of the present invention has a strength value of 400 kgf / cm ² or more after 26 cycles of the accelerated test, shows a higher strength than the cement of the comparative example, and is capable of constructing an excellent seawater-resistant concrete structure. Can be done. Also obtained in the same manner as in Example 1, using a cement plant manufacturing facility,
Breakdown of four types of cement with different compound compositions [Table 4]
Table 5 shows the mortar compressive strength test results according to JIS R5201.

[0041]

[Table 4]

[0042]

[Table 5]

According to this, as the amount of C ₃ S increases,
That is, the lower the amount of C ₂ S, the higher the compressive strength up to 28 days old. In addition, the Portland cement of Example 1 has a commercially available fineness of 4520 cm ² / g and an SO ₃ amount of 2.0%.
The results of seawater resistance test of blast furnace cement prepared by mixing 25 wt% and 45 wt% of the blast furnace slag powder in Table 1 are shown in Table 4 as Examples 4 and 5 . For comparison, the test results of blast furnace cement type A and blast furnace cement type B manufactured by Chichibu Cement Co., Ltd. are shown as Comparative Example 3 and Comparative Example 4. The method for producing the test piece and the test method for seawater resistance are the same as in Example 1 and Comparative Examples 1 and 2.

[0044]

[Table 6]

According to this, in the blast furnace cement type A of Comparative Example 3 in which about 25% by weight of blast furnace slag was mixed with ordinary Portland cement, cracks were generated in the specimen at the age of one year in artificial seawater at 20 ° C. However, the strength was gradually decreased, and the strength was gradually decreased by the accelerated test, resulting in poor seawater resistance.
Further, the B type blast furnace cement B of Comparative Example 4 in which about 45% by weight of blast furnace slag was mixed with ordinary Portland cement did not cause cracks in the specimen, but the strength was gradually decreased by the accelerated test and the seawater resistance was improved. It tended to be inferior.

On the other hand, the products of the present invention shown in Examples 4 and 5 have the same blast furnace slag mixing amount as those of the blast furnace cement type A of the comparative example 3 and the blast furnace cement type B of the comparative example 4.
The artificial seawater was cured at 0 ° C., and the strength was continuously increased in the subsequent accelerated test, showing excellent seawater resistance. It should be noted that the strength is further increased by the addition of the blast furnace slag as compared with Example 1.

In other words, the product of the present invention is JIS R 521.
When the amount of blast furnace slag of type A and type B of 1 "blast furnace cement" is 5 to 60% by weight, a concrete structure having a low neutralization rate and excellent seawater resistance can be constructed.

[0048]

[Effect] By using the cement composition of the present invention, a cement hardened product such as cement paste, mortar and concrete having excellent resistance to erosion of seawater can be produced, which greatly contributes to seaside and ocean development. You can

The excellent seawater resistance means that the cement composition of the present invention has resistance to erosion of sulfate ions and chlorine ions, and the cement composition of the present invention is also applicable as a sulfate resistant cement or a chloride resistant cement. I can.

─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Mitsuo Tanaka 2-1-1 Tsukimi-cho, Kumagaya-shi, Saitama Chichibu Cement Co., Ltd. Central Research Laboratory (56) Reference JP-A-2-120261 (JP, A) ) JP-A-5-213653 (JP, A) JP-A-50-126023 (JP, A) JP-A-49-51312 (JP, A) JP-A-7-144941 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C04B 2/00-32/02 C04B 40/00-40/06

Claims (6)

(57) [Claims] 1. A composition of cement produced without using a _{flux, 3CaO · SiO 2, 2CaO ·} SiO 2, 3CaO ·
Al ₂ O _3, comprising a compound composition of _{4CaO · Al 2 O 3 · Fe} 2 O 3 ( _{where, 4CaO · Al 2 O 3 ·} Fe 2 O
Excluding those in which ₃ is 7% by weight or less. ) Are those, in a weight ratio of SiO ₂ and Al ₂ O ₃ is 8 or _{more, 3CaO · SiO 2, 2CaO ·} SiO 2, 3CaO ·
Al ₂ O ₃ and _{4CaO · Al 2 O 3 · Fe} 2 3CaO · SiO 2 per 100 parts by weight of the sum of O ₃ is from 20 to 4
5 parts by weight, 2CaO.SiO _{2 in} a proportion of 45 to 72 parts by weight, a cement composition. _2. 3CaO.SiO ₂ , 2CaO.SiO
_{2, 3CaO · Al 2 O 3} , 4CaO · Al 2 O 3 · F
The cement composition according to claim 1, comprising a compound composition of e ₂ O ₃ , wherein the weight ratio of SiO ₂ and Al ₂ O ₃ is 8 to 15. 3. CaO.SiO ₂ , 2CaO.SiO
_{2, 3CaO · Al 2 O 3} , 4CaO · Al 2 O 3 · F
e ₂ O ₃ containing a compound composition of 3CaO.
_{SiO 2, 2CaO · SiO 2,} 3CaO · Al 2 O 3
And the total amount of 4CaO ・ Al ₂ O ₃・ Fe ₂ O ₃ is 100.
Fe ₂ O ₃ is 2.0 to 4.2 parts by weight in the case of parts by weight.
Cement composition. 4. The cement composition according to claim 1, wherein the blast furnace slag is added in an amount of 5 to 60% by weight. 5. Gypsum is 0.5 in terms of SO _{3 in} cement.
~ 4.5% by weight is added, The cement composition according to any one of claims 1 to 4. 6. A fineness of 3250 to 3450 cm ² / g
The cement composition according to any one of claims 1 to 5, wherein the cement composition is a cement composition.