JPS6261548B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an expandable admixture used to mix into various Portland cements to produce shrinkage compensating cement or chemical pre-stretching cement, and a method for producing the same. Conventionally, various types of expandable admixtures have been reported, including alumina cement plaster systems, various synthetic calcium aluminate mineral systems, and f.CaO (free lime) systems.
3CaO.3Al ₂ O ₃ .CaSO ₄ (hereinafter referred to as C ₄ A ₃ )
The main mineral phase is f.CaO, and the expandability of f.CaO is used. However, C ₄ A ₃
In the case of a system expansion material, it is natural that a large amount of SO ₃ component must be present in the blended raw material, so
There are the following manufacturing problems. That is, CaSO ₄ (hereinafter referred to as C) in the clinker and
_SO3 volatilization _{from C4A3} is 935℃ and 1250℃ respectively
This occurs at a relatively low temperature, so the
The volatilization of SO ₃ is unavoidable, and as a result, it is extremely difficult to generate a mineral phase as calculated in the formulation. In addition, it requires a huge amount of labor and equipment investment, such as the installation of a desulfurization device to collect volatile SO _3.While it is excellent as an equiexpansive admixture, it has a major drawback. In addition, in the case of f-CaO-based clinkers, known ones are f-CaO-C ₃ S-based clinkers (Note: C ₃ S is an abbreviation for tricalcium silicate (3CaOSiO ₂ )) or SO ₃ volatilization to burn out f-CaO. However, the difference in the amount of expansion depending on the curing conditions (difference in the amount of expansion between humid air curing and underwater curing) is very large, and in extreme cases, it is possible to avoid the problem of Even if they exhibit ideal expansion properties, they have the property of expanding too much and causing cracks when cured in water, which is a major drawback. Therefore, in recent years, the expansion properties of f-CaO have been controlled by adding anhydrous gypsum and have been improved to be relatively gentle, but the difference is still small compared to C ₄ A ₃ -based expansion materials. big. In addition, with this type of expanding material, f.
Since the amount of CaO and C controls the amount of expansion, the mineral phase in the partner cement mixed with it, especially f・CaO
Since extreme differences in expansion occur depending on the amount, it is troublesome that great care must be taken to ensure compatibility with the mating cement during use. The elution rate of f・CaO was controlled by using other calcium aluminate-based expansive materials such as C ₃ A, CA, C ₁₂ A ₇ , or by wrapping f・CaO with aluminate, ferrite, silicate, etc. Various ideas have been proposed, such as an f-CaO-based expansive material called F.CaO, but each has the following drawbacks. In other words, simply mixing a calcium aluminate phase into Portland cement does not provide high expansivity; it exhibits expansivity only when a large amount of SO ₃ is present, but the amount of expansion is greater than that of the f-CaO system. significantly smaller than. Furthermore, the method that purports to control the elution rate by wrapping f.CaO in various mineral phases is fundamentally f.
The disadvantage is that the elution rate of CaO is not suppressed, and the difference in curing conditions (difference in expansion amount between moist air curing and underwater curing) becomes extremely large. Therefore, as a result of experimental research, the present inventors determined that f-CaO, C ₃ A, and C, which were previously thought to be impossible to put into practical use due to expansion and coagulation problems, were the main constituent minerals. It has become clear that there is a quantitative relationship between the three that governs the amount of expansion and the difference in expansion amount due to curing conditions.Based on that knowledge, the amount used can be reduced, the strength will not decrease, and the difference in curing conditions can be reduced. We have succeeded in developing an expandable admixture that has a small amount of SO 3 and no need to worry about SO ₃ volatilization during production. That is, the present invention provides f・CaO, C ₃ A and C
are combined in a certain quantitative relationship. As mentioned above, the f-CaO-C type has been put to practical use, and the C ₃ A-C type has been researched and reported. Although the former is effective as an expanding material, it has the disadvantage that there are large differences in curing conditions and requires considerable consideration when used. Also, the latter is C ₃ A+
Since the volume expansion during the formation of ettringite represented by the reaction formula 3CaSO ₄ +32H ₂ O→C ₃ A・3CaSO ₄・32H ₂ O is utilized, the presence of f・CaO, which is particularly important in the present invention, is utilized. The need for this method was not recognized, and therefore the expansion force was small and it has not been put into practical use. If it is used forcibly, a large amount must be used because its expansion force is small, and if a large amount is used, the strength of the concrete itself will decrease. However, when f・CaO, C ₃ A, and C are combined in a fixed amount relationship as in the present invention,
The above-mentioned drawbacks can be counteracted and a product that is easy to use, that is, a product that requires little difference in curing conditions and can be used in a small amount, is obtained, and this is the first invention. Note that the above C ₃ A refers to 3CaO・Al ₂ O ₃ and
It refers to a 3CaO.Al ₂ O ₃ solid solution in which Na ₂ O, SiO ₂ , Fe ₂ O ₃ and other metals are dissolved in 3CaO.Al ₂ O ₃ . The second invention is a method for producing the expandable admixture of the first invention, and relates to a method for producing the expandable admixture without volatilization of SO ₃ during firing. The third invention is a manufacturing method for solving the problem of compatibility with the base cement, which is a daily problem in this type of technical field. Originally, when mixing an expansive material with cement to make an expansive cement, compatibility with the other base cement becomes a problem. In other words, the expandability varies greatly depending on the amount of expandable components such as f・CaO, C ₃ A, and C in the original cement, so
Cement with a small amount of C ₃ A, the amount of C ₃ A is around 8%,
The composition of the other cement, such as ordinary Portland cement with f・CaO of about 1%, white cement with C ₃ A content of 12% or more and f・CaO of more than 1%, and mixed cement such as blast furnace slag and fly ash,
Depending on the use, the compatibility may be good or bad, that is, the cement may or may not have the desired expandability, so strictly speaking, it is necessary to change the mineral composition depending on the other cement. . However, in the conventional manufacturing method of expanding materials, it is possible to control only the firing temperature, fineness, and amount of anhydrous plaster added during finishing, and it is not possible to adjust the difference in expansion amount due to the difference in expansion amount and curing conditions. It was difficult. The third invention was made to solve this problem at the same time, and when firing f・CaO-C ₃ A type clinker, there are two types of clinker: high f・CaO type and high C ₃ A type. The desired product is obtained by firing the clinker and then mixing and pulverizing it by changing the mixing ratio depending on the type and purpose of the partner cement when finishing the expanding material, or by mixing anhydrous plaster with the mixed and pulverized mixture of two types of clinker. It is something. In other words, according to this method, there is no need to manufacture expandable admixtures for each cement.
By changing the blending ratio of two types of clinker and plaster at the finishing stage, or by using a two-package system for the expanding material, it is possible to obtain an expansive admixture that matches the application, and there is currently relatively little demand for this type of admixture. This is an industrially superior manufacturing method for manufacturing products. Examples of the present invention will be described below. In the example described below, f・CaO is 70%,
Clinker A and f・CaO20 containing _C3A20 %
%, C ₃ A containing 70% is baked and mixed with C to produce an expandable composition. Table 1 shows the firing temperature of the clinker and the proportion of constituent minerals. .

[Table] Table 2 shows the relationship between f・CaO and C ₃ A in the clinker by changing the mixing ratio of clinker and anhydrous plaster.
The results of expansion tests at 7-day age when varying amounts of each were mixed at 10% into ordinary Portland cement are shown. In this case, the fineness of the expandable clinker is 2500 cm ² /g in Blaine value, and the expansion rate is expressed as the expansion rate in mm per 1 m in a 1:2 mortar using standard sand with a water-cement ratio of 0.60. And so.

[Table] Samples Nos. 1 to 3 are the cases in which anhydrous plaster was not added, and the amount of expansion was extremely small at a maximum of 0.53 mm/m. Nos. 4 to 7 are f・CaO in the expandable composition.
This is a case where the amount of C ₃ A is the same and the amount of anhydrous plaster in the expandable composition is changed to 40, 50, and 60%. According to this, all three satisfied the target expansion amount for non-shrinkage cement of 0.8 mm/m or more in wet air and 1.0 mm/m or more in water, and as the amount of anhydrous plaster increased, The difference in expansion amount in humid air becomes smaller. Nos. 8 to 12 are cases where the amount of anhydrous plaster mixed in is fixed at 50% or 60% of the expandable composition, and the mixing ratio of AB clinker is changed to vary the amounts of f・CaO and C ₃ A. However, as the amount of f·CaO in the expandable composition increases, the amount of expansion increases. Furthermore, the larger the amount of anhydrous plaster, the smaller the difference in the amount of expansion in water and in humid air. Figure 1 shows clinkers A and B in a 1:1 ratio.
This diagram shows the change in the amount of expansion when the amount of anhydrous plaster mixed in is varied from 0 to 60 with the ratio of CaO and C ₃ A constant. As the amount of anhydrous plaster added increases, the amount of expansion increases. However, it shows a maximum value between 30% and 50% of the amount of contamination. Furthermore, the ratio of water to wet air decreases as the amount of mixture exceeds 30%, and at 60% of mixing, the ratio becomes 1.0, that is, the difference between water and wet air disappears. In addition, both the expansion amount and the expansion amount ratio show the values at 7-day wood age. Figure 2 shows f・CaO, C ₃ A by fixing the amount of anhydrous gypsum at 50% and changing the ratio of clinkers A and B.
This shows the change in the amount of expansion when the amount is changed.As the amount of f・CaO increases, the amount of expansion increases, and this tendency is more remarkable in the case of underwater curing. In other words, the ratio of water to wet air increases as the amount of f・CaO increases. Note that both the expansion amount and the expansion amount ratio indicate values at 7-day wood age. The above results show that when anhydrous gypsum is not present in the expandable composition, the expanding force is small, and by mixing 40% or more of anhydrous gypsum, the expanding force can be increased, and the amount of expansion in water and in wet air is small. It can be seen that it is possible to reduce the difference. It is also clear that the expansion force increases as the amount of f·CaO in the expansion material increases. Figure 3 shows the results of an expansion test by varying the firing temperature of a blended raw material in which the amount of f・CaO and C ₃ A was 1:1.The expansion property suddenly decreased from the firing temperature of 1280°C. To increase. Note that the expansion amount is the value after 7 days of material age, and the injection amount of the expandable admixture is 10%. As can be seen from this figure, it is better to start baking at a temperature of 1200°C or higher, preferably 1350°C or higher. Table 3 shows the effect on the expansion force when the fineness of the expandable clinker and the fineness of the expandable composition are changed.As the fineness of the expandable clinker increases, the expansion force decreases. . Similarly, in the case of an expandable composition prepared by mixing and pulverizing anhydrous gypsum, the expansion power decreases as the powderiness increases. This is because the expandable clinker and the anhydrous plaster have different pulverizability, and it also depends on the plaster used, but the Blaine value is about 500 cm ² /g higher than when only the expandable clinker is crushed. Based on the above results, in carrying out the present invention, the brane value of the clinker is set to 2000 to 3500 cm ² /g, and anhydrous plaster is mixed in, or the expandable clinker and anhydrous plaster are mixed and ground to a brane value of 2500.
It can be seen that it is preferable to manufacture the expanding material by setting the density to be at least cm ² /g.

[Table] Tables 4 and 5 show cases where the expandable composition is mixed with different cements, such as sulfate-resistant cement.
In the case of cement in which CaO and C ₃ A are hardly present, not only the amount of expandable composition mixed in is increased, but also the amount of C ₃ A is increased. On the other hand, in the case of cement with a large amount of f・CaO, C ₃ A, and plaster, such as white Portland cement, by slightly reducing the amount of mixture and making a formulation with a large amount of f・CaO and C, it is possible to achieve the target expansion amount and It becomes possible to reduce the difference in the amount of expansion in humid air.

[Table] Table 5 shows examples of expansion tests when the amounts of f.CaO, C ₃ A and C were drastically changed. The Blaine value of the expandable admixture is 2500 cm ² /g.

[Table] The amounts of f・CaO, C ₃ A, and C in the expandable admixture vary widely depending on the source cement mixed.

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in expansion amount and expansion amount ratio with respect to the amount of plaster mixed into the expandable clinker in an example of the present invention, and FIG. 2 is a graph showing expansion with respect to changes in the mixing ratio of two types of clinker in an example of the present invention. FIG. 3 is a graph showing the relationship between clinker firing temperature and expandability in Examples of the present invention.

Claims (1)

[Claims] 1 f.CaO9-38%, _C3 A6-52%, C30-70
Expandable admixture consisting of %. 2 f・CaO, f・CaO whose main mineral is C ₃ A
C ₃ A type clinker is baked at 1200℃ or above, and in the final pulverization stage, C is mixed or pre-pulverized to produce f・CaO9~38%, C ₃ A6~
f・CaO−C ₃ A−C consisting of 52% and 30–70% C
A method for producing an expandable admixture, characterized by obtaining an expandable admixture. 3 First, f・CaO−C ₃ A clinker containing high f・CaO and f・CaO−C ₃ A clinker containing high C ₃ A are produced, and then both clinkers and C are mixed to produce f・CaO9~ 1. A method for producing an expandable admixture, characterized by obtaining an f.CaO-C ₃ A-C-based expandable admixture consisting of 38% C ₃ A, 6-52% C 3 A, and 30-70% C.