JPH0239464B2 - SEMENTOKONWAZAINOSEIZOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new method for producing an early high-strength cement admixture mixed with insoluble anhydrite, and more specifically, relates to a method for producing a cement admixture in which insoluble anhydrite is individually crushed to a specific particle size range and then mixed with cement. It has been known that adding 1 to 15% of finely ground insoluble anhydrite to Portland cement and steam curing improves its strength. If the insoluble anhydrite is wet with the attached moisture, the adhesion of fine powder is promoted and pulverization becomes difficult. Therefore, as a countermeasure to this problem, there is a method of mixing Portland cement or Portland cement clinker with insoluble anhydrite and pulverizing the mixture, but with this method, the particle sizes of the insoluble anhydrite and cement cannot be controlled.
Even if a pulverized product is expressed as a Blaine value, it is a value of average fineness and does not indicate particle size distribution. In other words, as for the fineness that affects strength, if it is too coarse, there will be little increase in strength, and if it is too fine, the workability of the concrete will be poor, and especially during centrifugal molding, there is a disadvantage that fine gypsum powder is concentrated near the inner surface and does not work effectively. It was hot. In view of the above circumstances, the present inventors conducted various studies on the relationship between particle size and strength, the problem of adhesion between fine particles, and the selection of an effective crusher regarding the crushing of insoluble anhydrite. Regarding the relationship between composition and concrete strength, grain compositions of 44μ or more and 35% by weight or less 44-2.8μ 55-75% by weight 2.8μ or less 20% by weight or less are optimal for developing concrete strength and concrete workability. I discovered that.
In other words, insoluble anhydrite with a size of 44μ or more does not react sufficiently with Portland cement, and a smaller amount is preferable for developing strength. In addition, if there is a large amount of insoluble anhydrite with a size of 2.8μ or less, the unit water volume during concrete molding will increase, which is not favorable for developing concrete strength.In addition, during centrifugal molding, insoluble anhydrite will rise to the inner surface, resulting in poor compaction. This is not desirable because it requires energy. We have also found that by using an impact crusher (for example, a Nara free crusher) to crush insoluble anhydrite, there is less adhesion of fine particles to each other, and it is easy to crush the insoluble anhydrite into fine powders within the preferred particle size range mentioned above. Ta. In the Nara type free crusher, insoluble anhydrite enters from the center of the fixed plate and rotating plate, diffuses with the air flow, is pulverized by the impact force, and is discharged after being impact pulverized by the outer pins and screen. The particle size of anhydrite has the advantage that it can be adjusted by the rotation speed of the rotary disk, the number of impact pins, and the hole diameter of the screen, and an effective particle composition can be obtained by classification with a separator. If the material is classified using a separator and the coarse particles are returned to the crusher and subjected to closed-circuit pulverization, the production of coarse particles and fine particles is small, making it possible to increase the effective particle fraction. Furthermore, since a large amount of air is used for separator classification, the moisture adhering to the insoluble anhydrite is carried away to the outside of the pulverizer, so even if the adhering moisture is about 1%, it can be pulverized without the fine particles adhering to each other. Furthermore, by introducing hot air into the pulverizer, pulverization is easy even when the adhering moisture content is approximately 10%. Further, diethylene glycol, triethanolamine, lignin sulfonate, etc. are widely used as grinding aids for Portland cement clinker, but these have not yet been used for grinding insoluble anhydrite. It has also been found that adding surfactants such as diethylene glycol, triethanolamine, and lignin sulfonate to insoluble anhydrite reduces the recombination of fine powder and promotes pulverization.
Further, as a result of research, it has been found that high-performance water reducing agents (such as Mighty, Melment, etc.) added during concrete molding are also effective as crushing aids, similar to the above-mentioned surfactants. It was also confirmed that when a high-performance water reducer is used as a crushing aid, it remains in the insoluble anhydrite after crushing without impairing its effectiveness as a water reducer, so it works effectively as a water reducer for high-strength concrete. Combining the above knowledge, insoluble anhydrite alone or with the addition of a surfactant or a high-performance water reducing agent is pulverized to 44μ or more and 35% by weight or less, 44-2.8μ55-75
Weight%, 2.8μ or less 20% by weight or less 100 parts by weight of Portland cement cement 15-100
This led to the invention of a method for producing a cement admixture characterized by mixing parts by weight. The surfactant and high performance water reducing agent that are added when crushing insoluble anhydrite can be used in powder or liquid form, and liquid types can be used by blowing hot air into them when crushing insoluble anhydrite. . The amount added is 10 parts by weight or less as solid content per 100 parts by weight of insoluble anhydrite. The reason for limiting the amount to 10 parts by weight or less is that this type of admixture, which has insoluble anhydrite as its main component, is usually used at less than 10% of the cement, so the entire amount of high-performance water reducer used during concrete mixing was premixed. This is because the value in the case was used as the standard. Insoluble anhydrite is crushed separately and mixed into a specified particle composition with Portland cement-based cement. Portland cement-based cements include ordinary, early-strength, ultra-early-strength, medium-heat Portland cement, silica cement, and fly ash. Cement and blast furnace cement are used, and for the purpose of early strength, a mixture of early strength cement and ultra early strength cement is particularly effective. The mixing amount is 15 to 100 parts by weight of the above cement per 100 parts by weight of insoluble anhydrite. If the amount of Portland cement is less than 15 parts by weight, it will not be effective in dispersing insoluble anhydrous gypsum. In addition, if the amount exceeds 100 parts by weight, a large amount is added to the concrete, which reduces its advantages as an admixture in terms of economy and handling. The particle composition of insoluble anhydrite was determined by dispersing 2.5 g of the sample in 2 ethyl alcohol and using LEEDS &
176, 125, 88, 62, 44,
From the measurement results of 31, 22, 16, 7.8, 5.5, 3.9, and 2.8μ, the particle composition of 44μ or more, 44-2.8μ, and 2.8μ or less is determined by calculation. The method for producing the cement admixture of the present invention involves pulverizing insoluble anhydrite alone into a specific particle composition using a pulverizer, and mixing it with cement, thereby eliminating the adhesion of insoluble anhydrite fine particles to each other, and even in cases where the insoluble anhydrite particles have a certain amount of adhering moisture. To provide a cement admixture that can be easily crushed and has high concrete strength. Furthermore, the addition of surfactants and high performance water reducers during pulverization promotes the above-mentioned preferred pulverization, and in particular, the addition of high performance water reducers can further enhance the water reduction effect since they are uniformly dispersed in the cement admixture. Not only that, but the kneading work on site can be streamlined. Next, the present invention will be specifically explained with reference to Examples. Example 1 Insoluble anhydrite was pulverized using a Nara type free pulverizer model M-4 to obtain five types of pulverized products having different particle compositions.
100 parts by weight of this finely powdered insoluble anhydrite was mixed with 50 parts by weight of ordinary Portland cement to produce a cement admixture. This cement admixture was mixed with concrete according to the composition shown in Table 1, and the mixture was poured into a cylindrical specimen form with an outer diameter of 20 cm, a height of 30 cm, and a wall thickness of 4 cm.
is gravitational acceleration) for 5 minutes, medium speed 15g for 5 minutes, high speed 30
It was centrifuged for 5 minutes at g. Regarding the molded object, the first
Steam curing was performed as shown in the figure, and compressive strength tests were conducted at 1 and 7 days old. The results are shown in Table 1.

[Table] As shown in Table 1, when the particle size of insoluble anhydrite after crushing is 44μ or more and 35% by weight or less, 44-2.8μ and 55-75% by weight, and 2.8μ or less and 20% by weight or less, the compressive strength is high. Admitted. Example 2 Next, six types of cement admixtures were made by varying the type and amount of cement mixed with the crushed insoluble anhydrite used in Sample No. 3, and compressive strength tests were conducted in the same manner as described above. Ivy. The results are shown in Table 2.

[Table] As shown in Table 2, crushed insoluble anhydrite 100
It was found that when the amount of cement mixed exceeds 10 parts by weight, the compressive strength is high. Also, as for the cement to be mixed, early-strength Portland cement is better than normal Portland cement.
It was also observed that the compressive strength increased. Example 3 Next, the effect of a crushing aid and the effect of reducing water on concrete when a high performance water reducing agent or surfactant was added during crushing of insoluble anhydrite was investigated. The results are shown in Table 3. The amount of high-performance water reducing agent mixed per 1 m ³ of concrete was reduced by the amount already added when insoluble anhydrite was crushed, and the total amount was kept constant.

[Table] ※※ Diethylene glycol *** Mighty 150
As shown in Table 3, the grinding ratio was increased by adding a high-performance water reducing agent or a surfactant, so the effect of the grinding aid was recognized. In addition, the slump value remained constant even if the amount of high performance water reducer mixed per 1 m ³ of concrete was reduced, indicating that the high performance water reducer added during crushing remained intact and contributed to the water reduction effect of concrete.

[Brief explanation of drawings]

The figure is a flow sheet for atmospheric pressure steam curing after concrete forming.

Claims (1)

[Scope of Claims] 1. 100 parts by weight of insoluble anhydrite pulverized by a crusher to have a particle size of 44μ or more and 35% by weight or less 44-2.8μ 55-75% by weight 2.8μ or less 20% by weight or less, and Portland cement. A method for producing a cement admixture, characterized by mixing 15 to 100 parts by weight of cement-based cement. 2 When crushing insoluble anhydrite alone with a crusher,
Insoluble anhydrite is pulverized by adding a surfactant or a high-performance water reducing agent to obtain a particle size of 44 μ or more and 35 weight % or less 44 μ to 2.8 μ 55 to 75 weight % 2.8 μ or less 20 weight % or less, and 100 parts by weight of Portland cement is added. A method for producing a cement admixture, characterized by mixing 15 to 100 parts by weight of cement-based cement.