JPS6149260B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fast-setting cement that quickly develops high strength not only at room temperature but also at low temperatures, and which exhibits less efflorescence. Conventionally, 10-20wt _% 3CaO・_3Al2O3・_CaSO4
(hereinafter referred to as _C3A3・C) and more than 8wt% _of calcium sulfate (hereinafter referred to as C) and a small amount of free
It has been known that adding alkali metal salts to ultra-early hardening cement containing CaO increases compressive strength, and that early strength can be obtained even at curing temperatures as low as 3°C. (Japanese Patent Application Laid-open No. 52-82928) However, in this case, although alkali metal salts are added, early strength can be obtained at low temperatures, but on the other hand, efflorescence of the alkali salts occurs on the surface after the cement hardens, resulting in poor aesthetic appearance. The range of use was limited because it caused significant damage. Therefore, the present inventors conducted research in search of a fast-hardening cement that does not impair the aesthetic appearance due to the occurrence of efflorescence and also provides early high strength even at _{low temperatures} . _A fast-setting cement ( _hereinafter referred to as A If an alkali metal compound (called cement) is added together with a colloid of aluminum hydroxide or a compound that generates aluminum hydroxide upon hydrolysis, the amount of efflorescence generated can be greatly reduced, and it can be used even at low temperatures. The present invention was completed based on the knowledge that a fast-setting cement that exhibits high strength can be obtained at an early stage. That is, the gist of the present invention is that an alkali metal compound and a compound that produces aluminum hydroxide upon hydrolysis are added to A cement, or A cement, an alkali metal compound, and a colloid of aluminum hydroxide are mixed at the time of use. Found in fast-setting cement. C ₃ A ₃・C is 10-40% by weight, C is 8% by weight
As mentioned above, in order to produce cement in which the molar ratio of C to _C3A3・C is 1.5 to _6.5 and contains free CaO at 7% by weight or less, CaO such as limestone and quicklime is required.
_Al2O3 sources, bauxite, clay, blast furnace slag _, etc.
source, phosphoric acid dihydrate, excretion etc.
Calcinate a mixture of CaSO ₄ sources etc. in a predetermined ratio,
The resulting clinker may be pulverized, or a material containing individually produced C ₃ A ₃ .C and C, as well as quicklime, may be mixed in a desired proportion. In this case, the cement fineness is Blaine value 4.000
It is preferable that it is at least cm ² /g; as a result, in the following cases, strength development may be delayed and abnormal expansion may occur after curing. Calcium sulfate may have bimolecular water of crystallization, half water of crystallization, or be anhydrous. Carbonates, sulfates, bicarbonates, silicates, phosphates, aluminates, etc. are used as alkali metal compounds, and the amount added should be 2% by weight or less based on the cement. preferable. If it exceeds 2% by weight, it is not preferable because it results in rapid setting that is not compatible with the construction speed, and furthermore, high strength cannot be obtained. The amount of the compound that produces aluminum hydroxide upon hydrolysis varies depending on the amount of the alkali metal compound added, but 5% by weight or more is not preferred because it causes too rapid setting. These include aluminum chloride, aluminum sulfate, and various types of alum. In addition, when using colloidal aluminum hydroxide, it is accompanied by water, so it is not possible to mix this colloid with A cement and an alkali compound in advance before use. Must be mixed before use. 10-40% by weight _{of C3A3}・C contained in cement
, the molar ratio of calcium sulfate and C ₃ A ₃ ·C was determined to be 1.5 to 6.5 in the ratio of 8% by weight or more of calcium sulfate and 7% by weight or less of free quicklime based on the following experiment. It is. In other words, limestone, bauxite, and phosphoric acid production by-product dihydrate are converted into C ₃ A ₃・C.
10-40% by weight, 8% or more of C, free CaO
is 7% by weight or less, and the molar ratio of C/C ₃ A _3.C is 1, 2, 4, 6, 8, 10. After mixing and pulverizing the resulting blended composition,
The mixture was granulated into pellets, which were then calcined at 1300°C for 1 hour. 2% by weight of aluminum sulfate of reagent grade 1 and 0.5% by weight of sodium carbonate were added to the obtained clinker.
In addition, it is ground with a ball mill and the Blaine value is approximately 4500.
A fast-setting cement of cm ² /g was obtained. The obtained cement was subjected to chemical analysis and X-ray diffraction analysis,
Furthermore, the strength test according to JISR5201 was conducted at 5℃ and 20℃.
The test was carried out on products that were molded in a constant temperature room at ℃ and cured at each temperature. According to X-ray diffraction analysis, the fast-hardening cement obtained contains C ₃ A ₃・C,
It was identified that C and free CaO were contained. Other minerals include β−2CaO・SiO ₂ (β
−C ₂ S) and 4CaO・Al ₂ O ₃・Fe ₂ O ₃ (hereinafter referred to as C ₄ AF) were generated. The weight percentage of produced minerals was determined from the chemical analysis values of fast-setting cement according to Borg's calculation formula, which is commonly used in cement chemistry. The molar ratio of C and C ₃ A ₃ ·C was determined from these calculated weight ratios. As an example of the results obtained, the strength characteristics after curing at 5° C. are shown in FIG. Furthermore, almost the same strength characteristics were exhibited even after curing at 20°C. The results of this strength test revealed that excellent early strength was obtained when the molar ratio of C to C ₃ A ₃ .C was between 1.5 and 6.5, and that outside this range the strength was so low that it was not suitable for practical use. The characteristics of the hydraulic action of the fast-setting cement of the present invention are as follows:
The specified cement mainly produces ettringite, and when it hardens, hardly any calcium hydroxide, which is often found in the hydration of Portland cement, is produced, and due to the synergistic effect of the alkali metal compound and aluminum hydroxide gel, it can be used even at low temperatures. This seems to be due to the fact that the curing speed is accelerated, and the hardened structure is densified by the addition of aluminum hydroxide gel, suppressing the movement of water, which is the driving force behind the occurrence of efflorescence. . As a result, the fast-setting cement of the present invention has the characteristics shown below. (1) No special heating equipment is required even during low-temperature construction. (2) Construction period can be shortened regardless of outside temperature. (3) Even in winter, sludge, industrial waste sludge,
Solidification of sludge, etc. can be done quickly. (4) Concrete with excellent aesthetic appearance can be obtained with almost no efflorescence. Next, the present invention will be explained with reference to examples. Parts and % in the text below indicate parts by weight and % by weight, respectively. Example 1 53 parts of limestone, 8 parts of bauxite, 22 parts of phosphoric acid byproduct plaster, and 17 parts of Kanto loam were mixed,
It was fired in a siliconite electric furnace at 1300°C for 1 hour. The obtained clinker was ground in a ball mill to obtain cement with a Blaine value of approximately 4500 cm ² /g. The composition _of this cement is _C3A3・C21.4%,
C 20.9%, CaO 6.6%, βC ₂ S 37.0%,
C ₄ AF 12.3%, MgO 0.3%, and C/
The molar ratio of C ₃ A ₃ ·C was 4.4. To this cement, sodium carbonate and aluminum sulfate shown in Table 1 were further added in portions and mixed uniformly to obtain a fast-setting cement. The obtained fast-hardening cement was heated to 5% according to JIS R5201.
It was molded and cured in a constant temperature room at ℃, and after 4 hours it was removed from the mold and the compressive strength of the mortar was determined. The obtained results are the first
Shown in the table.

[Table] Example 2 2% aluminum sulfate was added to the cement obtained in Example 1, and 0.5% of the various alkali metal compounds shown in Table 2 were added.
The obtained fast-setting cement was subjected to a mortar compressive strength test according to Example 1. The results obtained are shown in Table 2.

[Table] As a comparative example, the compressive strength of the mortar without using an alkali metal compound was 98 Kgf/cm ² . Example 3 590 parts of limestone, 490 parts of flue gas desulfurized dihydrate, 300 parts of red bauxite and 55 parts of Kanto loam were mixed and ground in a ball mill, and then ground in a test rotary kiln.
Clinker was obtained by firing at 1250°C to 1300°C. To this clinker were added 2% of industrial sulfuric acid sodium chloride and 1% of sodium carbonate, and the mixed composition was ground in a ball mill to obtain fast-setting cement. During grinding, 0.05% diethylene glycol was added to the grinding aid. The fineness of the fast-hardening cement obtained was determined and chemical analysis was performed, and the results are shown in Table 3.

[Table] Also, according to X-ray diffraction analysis, the minerals produced in this fast-setting cement are mainly calcium sulfoaluminate (C ₃ A ₃ C), 30.2%, anhydrous plaster (C), 30.0%, and quicklime (CaO), 4.5%. %, dicalcium silicate (β-C ₂ S) 19.2%, and aluminoferrite tetroxide (C ₄ AF) 12.2%. The molar ratio of C/C ₃ A ₃ ·C was 4.4. Next, concrete was prepared using this fast-setting cement, and a compressive strength test was conducted. The mix of concrete is shown in Table 4. Concrete was formed in a constant temperature room at 5°C in accordance with JIS A1132, and cured in a humid environment at 5°C. Compressive strength test is JIS
It was carried out at room temperature according to A1108. Comparative Example 1 is a quick-hardening cement manufactured according to Example 3 by adding only 1% of soda carbonate without adding aluminum sulfate to the clinker of Example 3, and Comparative Example 2 is ordinary Portland cement (Nippon Cement). Concrete was prepared under the same conditions as in Example 3, except that aluminum sulfate was not used, and a compression test was conducted. The test results obtained are shown in Table 5.

[Table] Comparative Example 1 is a fast-setting cement that does not contain aluminum sulfate. Comparative Example 2 used ordinary Portland cement.

[Table] Example 4 The same concrete mixture as in Example 3 was prepared in a constant temperature room at 20°C, and after curing for 1 day, it was removed from the mold, and after curing in water for 1 day, it was taken out and placed in a constant temperature water tank at 20°C without draining the water. They were placed on the upper rack and observed for the development of efflorescens. As a result, efflorescence did not occur in the concrete made of the fast-setting cement of the present invention, but in the concrete of Comparative Example 1, translucent needle-shaped crystals of about 1 mm were formed all over the next day, especially in the upper part. Admitted. In the concrete of Comparative Example 2, thin white powdery efflorescence occurred. A similar test was conducted on the same concrete mixture as in Example 3 at 5°C, but no efflorescence occurred.

[Brief explanation of the drawing]

Figure 1 shows C/C ₃ A ₃・C in fast-setting cement.
The relationship between (molar ratio) and the compressive strength of mortar made from this cement at a curing temperature of 5° C. and a material age of 4 hours is shown.

Claims (1)

[Claims] 1 3CaO・3Al ₂ O ₃・CaSO ₄ is 10-40% by weight, calcium sulfate is 8% by weight or more, calcium sulfate and
Aluminum hydroxide is added to cement (referred to as A cement), which has a molar ratio of 3CaO・3Al ₂ O ₃・CaSO ₄ of 1.6 to 6.5 and contains 7% by weight or less of free quicklime (referred to as A cement) and aluminum hydroxide by hydrolysis. An early-hardening cement made by adding the resulting compound, or by mixing an alkali metal compound and an aluminum hydroxide colloid with A cement at the time of use.