JPS5818337B2 - gypsum cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gypsum plaster 1 composition, and more particularly,
This invention relates to a gypsum-cement composition obtained by mixing α-gypsum produced by a special method, cement, and water.

In recent years, high-strength gypsum hemihydrate products have come to be made from α-gypsum as a raw material, and have been used for various molding materials in fields that take advantage of its expandability.

Grade 2 high-strength gypsum products exhibit high strength when dry, comparable to cement, but when wet, the strength decreases rapidly.

In particular, the product has the disadvantage that its water resistance strength when immersed in water is extremely reduced over time due to the water solubility of gypsum.

Therefore, for example, when the product is used for plasterboard, etc.
After a long period of time, the advantages of using α-gypsum, especially compared to plasterboard using normal β-gypsum, do not become apparent.

On the other hand, from the perspective of a non-combustible building material, plaster products are completely non-combustible, and if the water resistance of α-gypsum can be improved, the possibilities for its use in building materials will be greatly expanded. It is expected that

On the other hand, cement is used for various purposes as a basic building material due to its high strength, but in relation to gypsum, it is of the normal β type, and when mixed with gypsum, it has a β type compared to cement.
- Since the strength of the hardened gypsum is extremely low, no properties can be expected from mixing it, and it is more desirable both physically and economically to mix it with aggregate such as sand, and therefore it is not generally used.

If α-gypsum can be made into a composition mixed with cement by overcoming the above-mentioned drawbacks, it is expected that the rapid hardening of gypsum will also be a major feature.

However, cement is originally strongly alkaline, and gypsum, especially chemical gypsum, is an acidic substance mixed with acidic substances, and when mixed, it has the disadvantage of causing pseudo-setting and slowing down the hardening speed. .

The inventors of the present invention particularly anticipated mixing with alkaline cement, and when using α-gypsum obtained by calcining gypsum that has been made alkaline by adding alkali in advance as a raw material, lime etc. It has been discovered that a curable composition can be obtained which has extremely fast curing properties compared to the case where it is made alkaline by administering and mixed with cement, and the curing properties hardly change depending on the mixing ratio of cement. The present invention was achieved by discovering that the strength of objects after immersion in water is stronger than that of gypsum.

That is, the present invention is a gypsum-cement composition obtained by mixing α-gypsum, cement, and water, which is obtained by mixing an alkaline substance so that the pH after firing becomes 7 or higher and then firing the mixture once.

The present invention will be explained below using specific examples.

Gypsum is originally supposed to be neutral, but gypsum obtained by firing neutral gypsum trihydrate obtained by double decomposition or neutralization of salts cannot be stirred in water because acid remains in the crystallization water. When the pH of the aqueous layer was measured after it became cloudy, it was found to be acidic, for example p) (5,5), and in order to make the i)H after firing around 7, lime water etc. were added to bring the pH close to 10. It is necessary to use post-calcined plaster.

The α-gypsum used in the present invention is not simply prepared by mixing lime with α-gypsum produced in the usual manner, but by calcining gypsum dihydrate which has been made alkaline by adding lime in advance. Its feature is that it can be used as an alkaline α-gypsum with a pH of 7 or higher, and the preferred range of p) is 10 or higher.

However, even if the pH is 7 or more and less than 10, it is considered that if alkaline gypsum is used, the effect will be slightly reduced and the cause of the effect will not essentially change.

The method for producing α-gypsum described in the present invention is disclosed in Japanese Patent Application No. 1973-
The relationship between the pH and setting completion time of α-gypsum produced according to the method described in No. 21502 (Japanese Unexamined Patent Publication No. 49-115996), using phosphoric acid by-product gypsum, and the method described above. An example of this is shown in Table 1.

Note: In the case of phosphoric acid by-product gypsum, the amount of slaked lime added...r)H of α-gypsum obtained by calcination pH 10 where the effect of alkaline α-gypsum is most noticeable
, 5, the apparent results obtained by mixing compositions with different cement mixing ratios with water are shown in curve A in Figure 1, and as a control, normal α-gypsum with a pH of 6.0. The apparent end of is also shown as curve B.

Curve C also shows an example in which lime was added at the same time during curing so that the pH of the gypsum aqueous suspension became 11 or higher.

Also, the apparent termination of α-gypsum, which has a pH of 7.5, is also shown as a curved line.

To explain the present invention in detail according to FIG. 1, the normal α-
The apparent setting time of gypsum varies widely as the cement mixing ratio increases (curve B), but especially in small amounts of about 10%.
By adding up to this point, the curing speed decreases rapidly.

Therefore, in the present invention, which uses alkaline α-gypsum with a high pH of 10.5 (p) after firing, even if the amount of cement added increases, the hardening speed is hardly delayed and is actually accelerated. In contrast to Control Example B, the curing rate does not suddenly slow down due to the addition of a small amount of cement, but on the contrary shows a characteristic that it becomes faster (curve A).

In the case where lime is added during curing, assuming that the acidic part of the gypsum is neutralized by cement (curve C), the amount of lime necessary to bring the pH of the gypsum suspension water to 11 with lime is added during curing. However, in contrast to curve A using the α-gypsum of the invention previously prepared to a pH of 10.5, the rate of hardening is significantly retarded.

The difference in behavior between curve A and curve C is whether the force is applied before or after the lime is added.
This shows that the process of forming a hardened product during hardening is vastly different. It shows that the miscibility is severely altered.

On the other hand, the curve shows the case of α-gypsum obtained by firing to pH 7.5, but when curing only gypsum without cement, the curing speed is slower compared to α-gypsum which shows pH 10.5. However, compared to curve C in FIG. 1, it can be seen that the curing rate is generally faster and exhibits an intermediate appearance between curve A of the present invention and curve C for comparison.

In the gypsum-cement composition obtained by mixing gypsum, cement, and water obtained in this way, the gypsum hardens based on the hydration reaction of the gypsum, and the unset portion of the cement is included in the crystal lattice of the gypsum. It is thought that the apparent setting progresses due to the shape, and then the hardening of the cement progresses after a long period of aging. However, as the amount of cement mixed in increases, the mechanical strength of the gypsum when it absorbs water increases, and the rapid hardening of the cement increases. A hardened cement product is obtained.

Although the dry mechanical strength of a cured product using the gypsum-cement composition of the present invention is not necessarily greater than that of a cured product of cement alone or gypsum alone, it is possible to maintain the rapid hardening properties of gypsum while maintaining Compared to β-type gypsum, it has strong strength even when air-dried or at mixed temperatures, and it has the advantage of producing a highly economical hardened product whose hardening behavior does not change much depending on the addition ratio of cement, alkaline sand, etc. are doing.

As an example showing the performance of the composition of the present invention, water 200
0 parts of cement or cement according to the invention (p)
(100 parts of a mixture with α-gypsum showing 10.5, 5 parts of Volf and 5 parts of asbestos were added, mixed and stirred, this mixed suspension was made and dehydrated, and after molding and hardening the obtained 6,2-8. 2
Table 2 below shows the results of measuring the physical properties of a prototype mall laminated gypsum cement board after aging for 4 weeks.

Note: Refer to Example 25 below.In other words, a cured product made only of gypsum has relatively strong strength when air-dried.In particular, by using α-gypsum, a strong cured product can be obtained compared to a regular gypsum product (β gypsum). .

However, the strength of the cured product after absorbing water is extremely poor if it is made of only gypsum, so in normal gypsum boards, both sides of the gypsum are sandwiched with paper to give them strength.

As mentioned above, cured products using the gypsum-cement composition of the present invention have a curing speed that is almost the same as that of gypsum, but on the other hand, they have extremely superior water resistance strength compared to gypsum. (4 weeks) It can be seen that the hardening of the cement is progressing.

The present invention is a composition consisting of α-gypsum, cement, and water produced by the above-mentioned specific manufacturing method. The cement is mainly Portland cement and white cement, but when using a special composition such as rapid hardening cement, gypsum It may also affect the hardening of

Furthermore, in the case of alumina cement, the generation of cement bacilli due to the formation of entrigite is also considered.

The method of blending appropriate amounts of sand, wood flour, asbestos, and aggregate commonly used in cement into the gypsum-cement composition of the present invention also meets the required strength and economic efficiency of the cured product for use in the present invention71). Naturally, it is possible to further improve the physical properties by adding known additives such as those for improving the water resistance of cement or known third components such as those for improving the physical properties of the gypsum cement composition. You can also do it.

In addition, the gypsum cement composition of the present invention may be prepared by adding a known curing accelerator such as 2SO4 to the silifluoride salt or KCl used in curing gypsum to speed up curing, or by adding organic additives such as It is also possible to delay the curing by adding .

When a curing accelerator is mixed with the gypsum cement composition of the present invention, gypsum cement board can be manufactured using the composition by modifying the conventional gypsum board manufacturing process. In addition, by using it as is or by mixing it with a hardening retarder, spraying can be used as a gypsum-cement plaster for pouring materials, etc. In particular, the gypsum-cement composition of the present invention When the product is used in the above manner, the advantage of α-gypsum, particularly α-gypsum, which has excellent initial fluidity as described in Japanese Patent Application No. 1982-21502, is also exhibited.

The present invention will be specifically illustrated with reference to the experimental examples shown in the figures and tables below. However, it is well known that the water mixing ratio is a major factor controlling the mechanical strength of general gypsum products. Although the example shows a large amount of mixed water, the present invention is not limited to the mixing ratio of the example.

Example 1-7 (Experiment A in Figure 1) Add 100 g of freshly prepared α-gypsum with a pH of 10.5 to 45 g of water, and after the water is blended with the gypsum powder, the apparent final time for gypsum curing was determined. When measured based on the standard method JISR9112, the time was 19 minutes and 50 seconds.

In exactly the same way, α-gypsum 90g Portland cement 1
0 g (Example 2), α-gypsum soy portland cement 20 g (example 3), α-gypsum 6 (l portland cement 40 g (example 4), α-gypsum 40.9 portland cement 60 g (example 5) α - Gypsum 20.?Portland cement 80J (Example 6), α-gypsum 10g
A mixture of 90y of Portland cement (Example 7) was prepared, added to 45g of water, and the apparent completion time was measured based on the conventional method of plaster curing. seconds.

Example 4: 15 minutes and 10 seconds, Example 5: 15 minutes and 30 seconds, Example 6: 16 minutes and 10 seconds, and Example 7: 17 minutes and 05 seconds.

Examples 8 to 14 (Experiments shown in Figure 1 B) Using newly made α-gypsum, which showed a hydrogen ion concentration (pH) of 6.0 when 10 g of gypsum was stirred in 100 g of water, 100 g of When the α-gypsum was added to 45 g of water and the apparent completion time was measured according to a conventional method for curing gypsum, it heated up in 15 minutes (Example 8).

Next, in exactly the same manner as in Example 8, the apparent completion time was measured by a conventional method.Example 9) That is, α-gypsum 90.9
For a mixture of 10 g of Portland cement, the apparent final time was 44 minutes 20 seconds (Example 10), i.e., α-gypsum 8
45 minutes 20 seconds for 0g Portland Semen 1-20g;
(Example 11) That is, 53 minutes for 60 g of α-gypsum and 40 g of Portland cement. (Example 12) That is, 60 minutes 50 seconds for 41 gypsum and 60 g of Portland cement. (Example 13) That is, 72 minutes for 20 g of gypsum and 80 g of Portland cement. (Example 14) That is, for 90 g of gypsum 11' Portland cement, it was 96 minutes 20 seconds.

Examples 15 to 19 (Experiment C in Figure 1) Using the newly produced α-gypsum with a pH of 6.0 used in Examples 8-14, a concentration of 0.6 per 100 g of the α-gypsum was used.
J lime and 45 g of water were added (according to Table 1, the required amount of lime to raise the pH after firing from 6.0 to 10.5 is approximately 0.6 g).

) in their mixtures and in the presence of lime and water.
- The apparent completion time of the plaster was measured according to a conventional method.

That is, (Example 15) α-gypsum 100 grams, 10 g of lime, 0.6 g of lime, 61 minutes 50 seconds, (Example 17) α-gypsum, 80 g of portland cement 20J1 lime, 0.6 F, 68 minutes 20 seconds.

(Example 18) α-gypsum 4CBi'Portland cement 60J9 lime 0.6g 68 minutes, (Example 19) α-
Gypsum 2 (l portland cement soy. lime 0.6
，? A result of 98 minutes was obtained.

Examples 20 to 24 (Experiment D in Figure 1) Using α-gypsum with a pH of 7.45 obtained by adding 0.1 g of lime to 101 gypsum in advance and post-calcining it, this was used as a material. Change the mixing ratio of I-Kichi and mix 1 to 10
0J was added to 45 g of water, mixed and stirred, and then the apparent completion time was measured according to a conventional method.

(Example 20) α-gypsum 101 28 minutes 30 seconds (Example 21) α-gypsum 80g Portland cement 20g
41 minutes 10 seconds, (Example 22) α-gypsum 6CBi' Portland cement 40 g 48 minutes 50 seconds, (Example 23
) α-gypsum 40 g Portland cement 61 53 minutes 20 seconds, (Example 24) α-gypsum 20 g Portland cement 80F 58 minutes.

Example 25 100g of cement or 100g of a mixture of gypsum and cement was produced by a papermaking method similar to the manufacturing method of 8J cement board and pulp cement board. ! i' and asbestos 5g, pulp 5I water 2000c
A molded product obtained by making and dehydrating six sheets using a slurry mixed with c and C was solidified and aged for 4 weeks at room temperature, and then a molded product with a thickness of 6.2 to 8. A 2mm concrete board and a gypsum cement board were created.

Cut the second grade sample plate into width 4 crrL and length 8CrfL, and heat each 5 test pieces for bending strength measurement at 45°C±.
After drying in an air dryer at 2°C for 4 hours, the bending fracture strength was measured at an average loading rate of 20 kg/min at the loading point.

On the other hand, five other test pieces were immersed in water at room temperature for 24 hours, and then their bending fracture strength was immediately measured, and the results are shown in Table 2 above.

[Brief explanation of drawings]

The drawing shows α-gypsum and Shichimen 1- of the composition of the present invention. Curve A.= shows the relationship between the mixing ratio and the apparent completion time. D is the composition of the present invention, and curves B and C are control examples in which only α-gypsum or lime was subsequently added to α-gypsum.

Claims (1)

[Claims] 1. A gypsum-cement composition obtained by mixing α-gypsum obtained by mixing an alkaline substance and post-calcining so that the pH after firing becomes 7 or more, cement, and water.