JPH0796461B2 - Special cement with adjusted particle size - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a super-rapid hardened special cement that has been adjusted in particle size to improve fluidity, shrinkability, and rapid temperature rise and can be used in mass concrete. It is a thing.

<Conventional technology> Conventional cement with ultra-rapid hardening is 11CaO ・ 7Al ₂ O ₃・ C.
aF _2, SO a 3CaO · SiO ₂ with clinker and converted to SO ₃ to the main mineral ₃ / Al ₂ O ₃ = anhydrite of 0.7 to 1.8 and CaO translated at 1-20%
Of quicklime or slaked lime. Since the fluidity of this super rapid hardening cement disappears in a short time, a superplasticizer and a coagulation modifier are used. In addition, since ethrin guide is produced as an initial hydration product, it has expandability and large drying shrinkage. Since this ultra-rapid hardening cement shows a high hydration heat generation rate from the initial stage, the temperature of the concrete rises sharply and temperature cracks occur, so that it cannot be used as mass concrete. As described above, the conventional ultra-rapid setting cement has some drawbacks when used, such as poor fluidity, large drying shrinkage, and unusable for mass concrete. The conventional clinker for super rapid hardening cement has more rapid hardening,
The clinker has a high fineness. Therefore, there are many fine powder parts. This fine powder part has a very large specific surface area, so that the hydration reaction is very large. As a mineral composition, 11CaO ・ 7Al ₂ O ₃ has a very large hydration reactivity.
・ CaF ₂ is present in a very large amount in the fine powder part compared to the part with a large particle size, and there are many differentiating alkali components (Na ₂ O, K ₂ O) that have the effect of promoting the hydration reaction of cement. The hydration reaction rate is very fast due to the presence in the part. Therefore, if a large amount of fine clinker powder is present in the cement, the hydration reaction rate of the cement will be excessively increased, making handling of ultra-rapid cement extremely difficult. In addition, since 11CaO ・ 7Al ₂ O ₃・ CaF ₂ is present in a large amount in the fine powder portion, a large amount of ettringite is produced in the very early stage by reacting with gypsum, but ettringite completes production in the early stage. And dry shrinkage increases, which causes shrinkage cracks. Also, this 11CaO ・ 7Al ₂ O ₃
・ CaF ₂ has a very high hydration heat value from the initial stage because of its fast hydration reaction. Therefore, the temperature of the concrete rises sharply when it is placed as concrete, especially in mass concrete. Therefore, it causes cracks due to thermal expansion. In addition, a superplasticizer and a coagulant are used in super-rapid setting cement to adjust the fluidity and coagulation, but in the fine powder part of the clinker, the admixture addition amount must be increased in order to adsorb these admixtures. It has become obsolete.

As described above, the fine powder portion of the ultra-rapid hardening clinker has a very bad influence on the properties of the cement when the amount thereof is too large. However, if the fine powder portion is removed from the ultra-rapid clinker, the originally useful property of rapid hardening will be impaired.

<Problems to be Solved by the Invention> The present inventors have made various studies for the purpose of obtaining an ultra-rapid setting cement that does not have these drawbacks.

<Means for Solving Problems> As a result, it has been clarified that the cause of these drawbacks is that there are many fine powder parts of the clinker in the cement. Therefore, the present inventors have conducted diligent research on a cement using a clinker in which the amount of the fine powder portion of the ultra-rapid clinker is adjusted, and have a high fluidity, a low dry shrinkage property, and a special cement that does not lose the rapid hardening property. Developed and
The present invention has been accomplished.

That is, the present invention provides a mineral _{composition, 11CaO · 7Al 2 O 3 ·} C
aX ₂ (X is halogen, preferably fluorine) or / and 60 to 5 wt% of 12CaO · 7Al ₂ O ₃ and 80 to ₃₀ of 3CaO · SiO ₂ .
Having a Blaine specific surface area of 3000 to 6000 (cm ² / g)
The particle size of clinker for ultra-rapid hardening cement is 5 μm
The following is 1 to 3% by weight, preferably 10 to 25% by weight, 30 μm
This is a special cement that is prepared by adding gypsum to the residue adjusted to 8% by weight or less.

<Working> Usually, ultra-rapid hardening clinker contains about 35-45% by weight of particles with a particle size of 5 μm or less. Although the fluidity of the cement containing (type II anhydrous gypsum compounded so that the SO ₃ / Al ₂ O ₃ ratio = 0.7 to 1.8) is greatly increased, the cement is connected for a long time, and the drying shrinkage is also very small, In particular, by setting it to 10 to 25% by weight, the rapid hardening property is not impaired. In addition, the initial hydration calorific value is considerably lowered, and the temperature rise of concrete is considerably suppressed. Further, since the fluidity is improved and the adsorption by the fine powder portion is reduced, the use amount of the fluidizing agent and the coagulation adjusting agent can be very small.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

Example 1 A clinker for ultra-rapid hardening cement having a Blaine value of 4000
It is crushed to (cm ² / g) and it is No. 1 to 7 depending on the particle size.
Types (classified particle size 30μm or more, 30-18μm, 18-12μm,
(12 to 8 μm, 8 to 5 μm, 5 μm or less, 1 μm or less) is classified by using a classifier, and the particle size distributions of Nos. 1 to 6 are shown in FIG. Further, the chemical composition, mineral composition, and amount of pores in the clinker by the salicylic acid treatment of the clinker of each particle size were examined, and the results are shown in Tables 1 and 2. Table 1 shows the chemical composition of clinker with different particle sizes. Table 2 shows the mineral composition of clinker calculated from the chemical composition of Table 1. According to these, when the classified particle size is 30 μm or more, the composition is almost the same as that of the original clinker, but when the classified particle size is 30 μm or less, there is a difference in composition depending on the particle size. As the particle size decreases, Al ₂ O ₃ as the chemical composition increases, SiO decreases, and a small amount of CaO decreases. Also,
Alkali components (Na ₂ O, K ₂ O) as trace components are often found in the smaller particle size. The changes in the mineral composition corresponding to these changes in the chemical composition are due to the extremely high hydration reactivity of 11CaO ・ 7.
Al ₂ O ₃ · CaF ₂ becomes very large as the particle size becomes small, and 3CaO · SiO ₂ decreases. This 11CaO ・ 7Al ₂ O ₃
・ The ratio of CaF ₂ and 3CaO ・ SiO ₂ (11CaO ・ 7Al ₂ O ₃・ CaF ₂ / 3CaO
・ SiO ₂ ) increases as the particle size increases when the ratio of particles with a classification particle size of 5 μm or less is 1.00.
At ~ 18 μm, it is almost doubled to 1.90, and it is clear that the difference in composition depending on the particle size is very large. Of this mineral composition, 11CaO ・ 7Al ₂ O ₃・ CaF ₂ , 4CaO ・ Al ₂ O ₃・ Fe ₂ O ₃ can be quantified as the residue when the clinker is dissolved with salicylic acid, and the amount can be calculated. It is almost the same as the calculated amount.

In this way, 11CaO ・ 7Al ₂ O ₃ is contained in the fine powder part of the clinker.
・ Since CaF ₂ and alkaline components are present in a large amount, various adverse effects can be seen.

Example 2 With respect to the clinker shown in Table 1, the results of measuring the hydration heat rate and the cumulative hydration heat value are shown in FIGS. As described in detail above, clinker having a classification particle size of 5 μm or less has a high hydration reactivity of 11CaO · 7Al ₂ O ₃ · CaF ₂
The presence of a large amount of water, the large specific surface area, and the large amount of alkali components that promote the hydration reaction make the hydration heat generation rate very high immediately after contact with water, and the appearance of the second peak is also very high. It is fast and expensive. As the particle size increases, the rate of heat of hydration immediately after contact with water decreases and the appearance of the second peak also decreases. The one with all particle size (No.8) is
Due to the presence of the fine powder portion, the hydration heat generation rate immediately after contact with water is fast, but the second peak is gradual. According to the cumulative calorific value of hydration, those with a small particle size start up quickly and have a large amount. In addition, those with all particle sizes are broader although the initial stage is somewhat earlier.

Example 3 The crushed clinker used in Example 1 is shown in Table 3 in which the amount of the clinker prepared by classification is determined to be 5 μm or less. In addition, the hydration exothermic rate and cumulative hydration exothermic amount of this clinker were measured, and the results are shown in FIG.
Shown in. According to this, what removed the fine powder part,
The hydration heat generation rate immediately after contact with water is very small, and the second peak is slightly slower, but the peak height is quite high. The larger the removed amount, the smaller the hydration heat generation rate immediately after contact with water, and the second peak is slightly delayed. From these facts, it is clear that the hydration heat generation rate of the fine powder portion in the clinker immediately after contact with water is very fast, and the initial hydration is very suppressed by removing this fine powder portion. However, the subsequent hydration exothermic rate is even faster. In this way, by adjusting the fine powder portion, it is possible to hold down immediately after contact with water and accelerate hydration thereafter.

Example 4 Type II anhydrous gypsum was added to the clinker shown in Table 3 so that the molar ratio of SO ₃ and Al ₂ O ₃ (SO ₃ / Al ₂ O ₃ ) was 1.2 to obtain a cement. The property was measured using a B-type viscometer. The result is shown in FIG. According to this, the viscosity of No. 1 temporarily increases in the very early stage, but then gradually decreases, gradually increases as the age advances, and becomes high in about 1 hour. In the case of No.2, the temporary increase in viscosity at the initial stage is slow, and it is generally slow. N
The one of o.4 has a low viscosity up to 1 hour, but shows a rapid increase in viscosity thereafter. No. 5 is somewhat slower than No. 4 but rises more rapidly. As described above, the one in which the fine powder portion is appropriately removed has a low viscosity in the initial stage and is easy to handle, and when the viscosity starts to rise, it rapidly rises.

Example 5 Table 4 shows the handling time, the measurement result of the compressive strength and the amount of the retarder for the cement composed of the clinker and the type II anhydrous gypsum shown in Table 3. Mortar molding for strength measurement was performed in a room at 20 ° C. ± 1 ° C. and a temperature of 80%, aged in air for up to 1 day after demolding, and then aged in water to measure the compressive strength at each age. S / C = 2.0, W / C = 65%, specimen size 4 ×
Performed at 4 x 16 cm. The handling time was defined as the time when the penetration depth of the conical needle was constant, using mortar under the same conditions as the strength measurement. In terms of compressive strength, those that develop strength in the early stages are those of Nos. 1 to 4, but this is because the presence of the fine powder portion accelerates the initial hydration, which shortens the handling time and reduces the strength from the beginning. This is because it becomes to show expression. Nos. 2 to 3 having an appropriate amount of fine powder have a handling time of 30 to 60 minutes, are easy to handle, and exhibit high strength from the initial stage. On the other hand, even those with a small amount of fine powder show strength development one day after the age,
As the material ages, high strength is obtained without fine particles for a long time.

Example 6 FIG. 7 shows the results of measuring the dry shrinkage rate of cements using the clinker of Table 3 whose particle size was adjusted. The measurement was performed using a test piece under the same conditions as the strength measurement, with a measurement width of 10 cm on the basis of one day after kneading. No. 1 has a large amount of dry shrinkage, but No. 2 with a small amount of fine powder is somewhat smaller. And, No. 4 except for the fine powder part is the smallest. From these facts, it can be seen that the dry shrinkage amount is greatly reduced by removing the fine powder portion.

Example 7 The clinker shown in Table 3 and type II anhydrous gypsum (SO ₃ / Al ₂ O ₃ =
Table 5 shows the change in the flow value when the setting modifier was added to the cement consisting of 1.2). Mortar is sand / cement = 2.0, water / cement = 65%, curing temperature 20 ℃
And No. 1 with no particle size adjustment shows almost no fluidity with no addition, the flow value is 105, and
Almost no effect is seen with a small amount of addition. It shows fluidity when added as much as 0.30%. On the other hand, Nos. 3 and 5 in which the fine powder portion was reduced by adjusting the particle size show a large flow value even without addition, and show a sufficient flow value by adding a small amount of the coagulation modifier. Thus, by adjusting the fine powder portion, sufficient fluidity can be obtained with a small amount of the coagulation modifier.

Example 8 The clinker used in Example 1 had a Blaine value of 6000 (cm ² / cm ²
It was ground to g) and classified according to particle size. The classified particle size and the amount of classified clinker of 5 μm or less are shown in Table 6, and the clinker and type II anhydrous gypsum (SO
Table 7 shows the handling time of the cement composed of ₃ / Al ₂ O ₃ ), the measurement result of the compressive strength, and the amount of the retarder. No. 7 compared to those in Table 3 crushed to a Blaine value of 4000 (cm ² / g)
However, the handling time is considerably fast and handling is difficult because the size is 5 μm or less. Even with No.8, more than 30% still have less than 5 μm and handling is poor. But No.9
After that, the handling time is sufficient.

<Effects of the Invention> As described above, the ultra-rapid hardening cement of the present invention is extremely useful because it can improve fluidity and contractility and suppress a rapid temperature rise. Therefore, there is an advantage that the use amount of the fluidizing agent and the coagulation adjusting agent can be very small.

[Brief description of drawings]

Fig. 1 shows the particle size distribution of the classified clinker, Figs. 2 and 4 show the heat generation rate of the particle size (partial) adjusted clinker, Figs. 3 and 5 show its cumulative heat of hydration, and Fig. 6 shows the fluidity of the fine powder partially adjusted clinker.
FIG. 7 shows the drying shrinkage, respectively.

Claims (1)

[Claims] 1. A mineral composition of 11CaO.7Al ₂ O ₃ .CaX
₂ (X is a halogen) or / and 12CaO · 7Al ₂ O ₃ is 60 to
The particle size of the clinker for ultra-rapid cement having a Blaine specific surface area of 3000 to 6000 (cm ² / g) having 5 wt% and 3 CaO / SiO ₂ of 80 to 30 wt% is 1 to 3 wt% when the particle size is 5 μm or less, 30
A special cement made by adding gypsum to a product adjusted to have a 0 μm residue of 8% by weight or less.