JP2007223819A - Belite-mixed cement and method of producing concrete product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide belite-mixed cement having high strength and a method of producing a concrete product having the same high strength using the belite mixed cement. <P>SOLUTION: The belite mixed cement having high strength contains a first cement composition consisting essentially of alite and a second cement composition consisting essentially of belite and the specific surface area of the second cement composition is controlled to 5,000-9,000 cm<SP>2</SP>/g. The belite-mixed cement having high strength is prepared by mixing both compositions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a belite mixed cement and a method for producing a concrete product using the belite mixed cement.

  In cements that require low heat generation during hydration and early strength development, the first cement composition containing an aluminate phase and a ferrite phase mainly composed of alite having early strength development. And a second cement composition containing, as a main component, belite that suppresses heat generation during hydration and also containing an aluminate phase and a ferrite phase, belite mixed cement is used. .

In the first cement composition, the specific surface area is 3000 to 6000 cm ² / g, and in the second cement composition, the specific surface area is 2500 to 4000 cm ² / g.

By using belite mixed cement having the above structure, heat generation during hydration can be suppressed, cracking due to temperature rise accompanying heat generation, etc. can be prevented, and early strength development can be realized simultaneously (patent) Reference 1).
Japanese Patent No. 3040985

  However, when using the belite mixed cement described in Patent Document 1 of the background art for exterior materials, roof tiles, and the like that require high strength, first, steam curing is performed to express strength by alite. In addition to suppressing heat generation during hydration by further promoting autoclave curing, the strength is further increased by promoting the expression of belite, which has the effect of increasing cement strength by autoclave curing. I am doing so.

  However, in the above autoclave curing, since the reactivity in the crystallization reaction during the development of the strength of belite is low, the strength of the belite cannot be efficiently developed. In some cases, it was difficult to increase the strength.

  The present invention solves the above-mentioned problems of the background art, and by efficiently expressing the strength of belite in autoclave curing, the belite mixed cement having high strength and the same belite mixed cement are used. An object of the present invention is to provide a method for manufacturing a concrete product.

In order to solve the above problems, the invention described in claim 1 of the present application contains a first cement composition mainly composed of alite and a second cement composition mainly composed of belite. The second cement composition has a specific surface area of 5000 to 9000 cm ² / g.

The invention according to claim 2 of the present application is characterized in that, in the belite mixed cement according to claim 1, the specific surface area of the first cement composition is 3000 to 4000 cm ² / g.

  The invention described in claim 3 of the present application is characterized in that it is a method for producing a concrete product in which autoclave curing is performed after molding using the belite mixed cement according to claim 1 or 2 described above.

In the belite mixed cement according to the first aspect of the present invention, the specific surface area of the second cement composition containing belite as a main component is increased to 5000 to 9000 cm ² / g, whereby belite crystals in autoclave curing are obtained. By improving the reactivity of the conversion reaction and efficiently developing the strength of the belite, a belite mixed cement having high strength can be provided.

In the belite mixed cement of the invention according to claim 2 of the present application, in particular, by setting the specific surface area of the first cement composition mainly composed of alite to 3000 to 4000 cm ² / g, By performing the strength development with alite more efficiently, the strength of the belite mixed cement including the subsequent autoclave curing can be further increased.

  And the strength of a concrete product can be greatly raised by shape | molding concrete products using the said belite mixing cement, and performing autoclave curing after that.

The belite mixed cement which is an embodiment of the present invention has a first cement composition mainly composed of alite and a second cement composition mainly composed of belite. The specific surface area of the cement composition is set to 5000 to 9000 cm ² / g.

The specific surface area of the first cement composition may be 3000 to 4000 cm ² / g.

  Hereinafter, the belite mixed cement of this embodiment will be described in more detail. First, the 1st cement composition which has aerite as a main component has intensity | strength expression property independently, and has the property similar to what is called Portland cement.

  First, the role of the first cement composition is to develop an appropriate strength by steam curing and to withstand internal stress due to a rapid reaction in the subsequent autoclave curing. There is no need to include belite.

  However, even if belite is included, the content ratio is 20% by weight (hereinafter, simply referred to as “%”) in order to have no significant effect on strength development during steam curing during the production of concrete products. There is no particular problem if it is as follows.

  The content of the aluminate phase and ferrite phase is not particularly specified, but the content of the aluminate phase that affects the initial hardening reaction is 10% or less during the production of concrete products, and the aluminate phase The total of the phase and the ferrite phase is 25% or less.

Further, the specific surface area of the first cement composition is preferably pulverized so as to be 3000 to 4000 cm ² / g so that the alite can efficiently develop strength in steam curing.

Specifically, if the specific surface area of the first cement composition is less than 3000 cm ² / g, strength development during steam curing is delayed, and it may not be possible to withstand subsequent autoclave curing. .

On the other hand, when the specific surface area of the first cement composition is greater than 4000 cm ² / g, the hydration reaction of alite proceeds excessively during mixing of the first cement composition and water during the production of concrete products. For this reason, the generated calcium silicate hydrate (CSH) covers the unreacted portion of alite and may hinder the progress of the subsequent hydration reaction.

Further, when the specific surface area of the first cement composition is larger than 4000 cm ² / g, the specific surface area of the aluminate phase contained in the first cement composition is similarly increased, that is, the particle size of the aluminate phase is increased. As a result, the reactivity becomes higher, and as a result, the fluidity may decrease due to rapid hardening of the aluminate phase after mixing the first cement composition and water. It is not preferable.

  Next, in the second cement composition mainly composed of belite, the content ratio of alite is preferably 10% or less, and the aluminate content and ferrite phase content are particularly specified. However, like the first cement composition, the content of the aluminate phase is 10% or less, and the total of the aluminate phase and the ferrite phase is 25% or less.

  Next, the second cement composition blended as described above is fired at a temperature of about 1200 to 1500 ° C., and is generated by the transition of the crystal structure of belite during cooling after firing. In order to prevent so-called dusting, the firing temperature is preferably set to 1400 ° C. or higher, and it is necessary to rapidly cool after firing.

  In this case, it may be necessary to adjust the amount of calcium so that alite is not generated during firing. However, in order to prevent the formation of alite, Since sting is likely to occur, the silicic acid component contained in the second cement composition is one that does not contain a crystalline material such as quartz.

  At this time, as the silicic acid component, it is preferable to use fly ash (FA) or viscosity or soft silica containing moderately alumina or iron, and waste building materials using them.

Furthermore, the second cement composition needs to be pulverized so that the specific surface area of the second cement composition is 5000 to 9000 cm ² / g in order to make belite react efficiently during autoclave curing.

When the specific surface area of the second cement composition is smaller than 5000 cm ² / g, the reactivity of the crystallization reaction of belite becomes low during the autoclave curing, while the specific surface area of the second cement composition is reduced. In order to make it larger than 9000 cm ² / g, it takes a very long time for pulverization, and this particularly leads to an increase in cost.

  Next, in the case of mixing the first cement composition and the second cement composition, in particular, without using a pulverizing and mixing method such as a ball mill for increasing the specific surface area of the first cement composition. In addition, a Henschel mixer having a high-speed rotating blade is used.

  In addition, in the case of mixing in a small amount, the first cement composition and the second cement composition are put into a plastic bag or the like and shaken about 10 times while containing air so that they can be easily mixed with each other. Both can be mixed by stirring.

  The above mixing produces belite mixed cement. In the above configuration, examples and comparative examples of the present invention will be described below.

Example 1
In Example 1, as shown in Table 1, a commercial Portland cement having a specific surface area of 3300 cm ² / g was used as the first cement composition.

  On the other hand, the second cement composition is a clinker which is an intermediate product after firing by adding calcium, iron, etc. to the ceramic-based waste building material, firing at a temperature of 1400 ° C. for 1 hour (hr), and then rapidly cooling. Was generated.

200 g of this clinker was weighed, 4% of gypsum was added, and a ball mill having a capacity of 500 cc, a ball diameter of 20 mm and a number of balls of 20 was used, and pulverized at 250 rpm for 1 hour (hr). As shown in FIG. 1, a second cement composition having a specific surface area of 6500 cm ² / g was obtained.

  The composition of the second cement composition is alite: 0.9%, belite: 74.8%, aluminate phase: 9.2%, and ferrite phase: 14.3%. It is the main component.

  Next, the first cement composition and the second cement composition were mixed at a mixing ratio shown in Table 1 to produce a belite mixed cement. At this time, the first cement composition and the second cement composition are respectively put into a plastic bag prepared in advance at a predetermined mixing ratio, and about 10 times while containing air so that they can be easily mixed with each other. Mixing was performed by shaking and stirring.

  Next, after adding sufficient water to the pulp and stirring the mixture with a mixer for 1 minute to disentangle the pulp fibers, the above belite mixed cement, fly ash (FA) and silicic acid are added, and the solid content concentration is increased. While adding water to 8%, the slurry was produced by stirring so as to be sufficiently uniform.

  At this time, the blending ratio in the state excluding water is: Belite mixed cement: 40%, FA: 40%, silicic acid: 10%, and pulp: 10%.

Next, the slurry was filtered by suction, and when a filtrate could not be obtained, press molding was performed at a pressure of 30 kg / cm ² while adjusting the amount of the slurry to form a plate-like sheet having a thickness of 12 mm.

  Next, as shown in Table 2, the sheet was subjected to steam curing at a temperature of 80 ° C. for 24 hours (hr) to promote the development of alite strength. In this steam curing, the humidity was set to 90%. Thereafter, the autoclave curing was further performed for 6 hours (hr) at a temperature of 180 ° C. to promote the crystallization reaction of belite, and further the strength development was performed, thereby producing a concrete product using belite mixed cement. . The pressure during the autoclave curing was set to 10 atmospheres.

  Then, after steam curing and autoclave curing, each sample was cut into a size of 160 mm in length, 40 mm in width (width) and 12 mm in thickness using a running saw or the like, and a sample for bending strength test was created.

  Next, a three-point bending strength test was performed on the created sample at a span of 100 mm and a speed of 2 mm / min, and the bending strength shown in Table 2 was calculated using equation (1).

k = 3 × s × m / (2 × h × w ² ) (1)
Here, k: bending strength (MPa), m: bending fracture load (N), s: span (mm), h: lateral (width) dimension (mm), and w: thickness.

As shown in Table 2, in Example 1, high bending strength is obtained after the autoclave curing. This is because the specific surface area of the second cement composition is increased to 6500 cm ² / g by finely pulverizing the second cement composition mainly composed of belite. It is considered that the reactivity was improved, and as a result, the strength of belite was efficiently developed.

Further, by setting the specific surface area of the first cement composition to 3300 cm ² / g, in the steam curing performed before the autoclave curing, the strength expression by alite can be efficiently performed. It seems that the strength of belite mixed cement including autoclave curing could be further increased.

(Example 2)
In the second embodiment, only matters different from the first embodiment will be described, and the description of the first embodiment will be used for those having the same configuration, effects, and the like.

  The difference between Example 1 and Example 1 is that, as shown in Table 1, the mixing ratio of the first cement composition is 80% and the mixing ratio of the second cement composition is 20%. It is in place.

  Based on the above differences, the belite mixed cement of Example 2 will be described below.

  About the structure of a 1st cement composition and a 2nd cement composition, it is the same as that of the said Example 1. FIG.

  Next, the first cement composition and the second cement composition were mixed at a mixing ratio shown in Table 1 to produce a belite mixed cement. At this time, similarly to Example 1, the first cement composition and the second cement composition are respectively charged at a predetermined mixing ratio into a plastic bag prepared in advance, and air is easily mixed with each other. While mixing, the mixture was stirred by shaking about 10 times.

  After the first cement composition and the second cement composition are mixed, they are the same as in Example 1 above.

  As shown in Table 2, in Example 2, the bending strength after steam curing is higher than that in Example 1, but the final bending strength after autoclave curing is lower than that in Example 1.

  In this Example 2, since the mixing ratio of the first cement composition that develops strength during steam curing is higher than that of Example 1, the reactivity of alite contained in the first cement composition is increased. As a result, the bending strength after steam curing increased, but the mixing ratio of the second cement composition mainly composed of belite, which affects the strength after autoclave curing, is as low as 20%. It is considered that the bending strength after curing was lower than that in Example 1.

(Example 3)
In the third embodiment, only matters different from the first embodiment will be described, and the description of the first embodiment will be used for those having the same configuration, effects, and the like.

The part of Example 3 different from Example 1 is that, as shown in Table 1, the specific surface area of the first cement composition is 5000 cm ² / g, and the specific surface area of the first cement composition is as described above. It is higher than Example 1.

  Based on the above differences, the belite mixed cement of Example 3 will be described below.

The first cement composition uses a commercially available Portland cement having a specific surface area of 3300 cm ² / g as in Example 1 above. However, by using 20 ball mills and pulverizing at a rotational speed of 250 rpm, the specific surface area is set to 5000 cm ² / g. On the other hand, the configuration of the second cement composition is the same as that of Example 1 above.

Next, the first cement composition having a specific surface area of 5000 cm ² / g and the second cement composition were mixed at the mixing ratio shown in Table 1 to produce a belite mixed cement. At this time, the first cement composition and the second cement composition are respectively put into a plastic bag prepared in advance at a predetermined mixing ratio, and about 10 times while containing air so that they can be easily mixed with each other. Mixing was performed by shaking and stirring.

  After the first cement composition and the second cement composition are mixed, they are the same as in Example 1 above.

  As shown in Table 2, the bending strength after steam curing in Example 3 was higher than that in Example 1 and further above Example 2, but the final bending strength after autoclave curing was as described above. Lower than Example 1 and Example 2.

In this Example 3, since the specific surface area of the first cement composition is 5000 cm ² / g as described above, which is higher than those in Examples 1 and 2, the reaction of this alite. As a result, the strength expression at the time of steam curing increased, and as a result, the bending strength after steam curing is considered to have increased.

  In addition, during steam curing, the generated calcium silicate hydrate (CSH) contributes to the development of strength. This calcium silicate hydrate is contained in the second cement composition. By covering the surface, the reactivity of belite is lowered during the subsequent autoclave curing, and as a result, the bending strength after the autoclave curing is considered to be decreased.

(Comparative Example 1)
In the first comparative example, only matters different from the first example will be described, and the description of the first example will be used for those having the same configuration, effects, and the like.

The difference between the first comparative example and the first example is that, as shown in Table 1, the second cement composition is not mixed and is composed of only the first cement composition. That is, this comparative example 1 is made of a commercially available Portland cement having a specific surface area of 3300 cm ² / g.

  Based on the above differences, the commercially available Portland cement of Comparative Example 1 will be described below.

  Add sufficient water to the pulp, stir it with a mixer for 1 minute to defibrillate the pulp fibers, and then add the first cement composition composed of the above commercially available Portland cement, fly ash (FA) and silicic acid Then, a slurry was generated by stirring the mixture so that it was sufficiently uniform while adding water so that the solid content concentration became 8%.

  At this time, the blending ratio in the state excluding water is 40% commercially available Portland cement (first cement composition), FA: 40%, silicic acid: 10%, and pulp: 10%. After the slurry is generated, it is the same as in Example 1 above.

  As shown in Table 2, the bending strength after the autoclave curing in Comparative Example 1 was lower than in Examples 1 to 3 above.

  In this comparative example 1, since the second cement composition containing belite is the main component that develops strength during the autoclave curing, the bending strength after the autoclave curing is the second cement composition. It is thought that it was lower than the above Examples 1 to 3 included.

  Therefore, in order to improve the bending strength after autoclave curing, it seems necessary that the second cement composition containing belite as a main component is included.

(Comparative Example 2)
In this comparative example 2, only the matters different from the above-described example 1 will be described, and the description of the above-described example 1 will be used for those having the same configuration, operational effects, and the like.

The part where this comparative example 2 differs from the said Example 1 is a place where the specific surface area of a 2nd cement composition is 3500 cm < ² > / g as shown in Table 1, and is lower than the said Example 1. .

  Based on the above differences, the belite mixed cement of Comparative Example 2 will be described below.

  The configuration of the first cement composition is the same as in Example 1 above. Next, the second cement composition is an intermediate product after calcination by adding calcium, iron, and the like to the ceramic-based waste building material, followed by firing at a temperature of 1400 ° C. for 1 hour (hr) and then quenching. Generated clinker.

200 g of this clinker was weighed, 4% of gypsum was added, a ball mill with a capacity of 500 cc, a ball diameter of 20 mm, and a ball number of 20 was used. ^The mixture was pulverized to ² / g to obtain a second cement composition.

  The composition of the second cement composition was the same as in Example 1 above: alite: 0.9%, belite: 74.8%, aluminate phase: 9.2%, and ferrite phase: 14. 3%, and belite is the main component.

  After the second cement composition is generated, it is the same as in Example 1 above.

  In Comparative Example 2, both the bending strength after steam curing and the bending strength after autoclave curing are lower than those in Example 1 above.

In Comparative Example 2, the specific surface area of the second cement composition was set to 3500 cm ² / g, which was smaller than that of Example 1, so that the specific surface area of the aluminate phase contained in the second cement composition was the same. It is thought that it became small.

Here, since the aluminate phase reacts with alite during steam curing and contributes to the development of strength, the specific surface area of the aluminate phase contained in the second cement composition is reduced. It seems that the bending strength after steam curing was reduced because the reactivity of the aluminate phase was lower than in Example 1. Also, the specific surface area of the second cement composition was made smaller than in Example 1 above. Since the specific surface area of belite, which is the main component of the second cement composition, is similarly reduced, the reactivity of belite is reduced during autoclave curing. As a result, the bending strength after autoclave curing is reduced. It is thought that it decreased.

  As described above, as shown in Examples 1 to 3 and Comparative Examples 1 and 2, the specific surface area of the second cement composition is increased, and an appropriate amount thereof is mixed with the first cement composition. By this, since the bending strength after autoclave curing can be improved, a belite mixed cement having high strength can be provided.

Claims (3)

A first cement composition mainly composed of alite and a second cement composition mainly composed of belite. The specific surface area of the second cement composition is 5000 to 9000 cm ² / Belite mixed cement characterized by being g. 2. The belite mixed cement according to claim 1, wherein the first cement composition has a specific surface area of 3000 to 4000 cm < ² > / g.   A method for producing a concrete product, characterized by performing autoclave curing after molding using the belite mixed cement according to claim 1 or 2.