JPS5930665B2 - Cement composition for surface finishing - Google Patents

Description

[Detailed description of the invention] The present invention relates to cement compositions for surface finishing.

Traditionally, cement mortar has been used as a surface finishing method, and wooden acid is widely applied to the interior and exterior of civil engineering such as concrete, architectural structures, and molded objects, and is used as a method to easily and economically impart water resistance, fire resistance, and aesthetics. has been done.

However, the cement mortar used for surface finishing has defects such as shrinkage and cracking when the construction surface dries, deterioration of the construction surface, internal corrosion of the structure due to water leakage, and loss of aesthetic appearance.

Up to now, methods to improve this problem have been to use various laths as the base material, and to mix natural fibers such as straw and hemp, various synthetic organic fibers, or inorganic fine powder for an organic resin layer. However, it has not been possible to prevent cracks from occurring on the construction surface.

In addition, recently a method has been proposed in which an expansive admixture (hereinafter referred to as an expanding agent) is mixed into cement mortar, but the amount of expansion of the expanding agent to be mixed depends on the amount of cement, water, aggregate, etc. and curing conditions. changes, and the compensation effect for the drying shrinkage of cement mortar is always unstable. Also, if a large amount of expanding agent is mixed, the strength of the mortar decreases significantly, and furthermore, unreacted expanding agent will cause cement to deteriorate. If it remains in the mortar, it will expand again after the mortar has hardened, causing cracks in the mortar and further increasing costs. There has been a demand for the development of

The present inventors have conducted intensive research to solve the above problems and have completed the present invention.The purpose of the present invention is to provide a surface finishing cement composition with excellent crack prevention ability and good workability at a low cost. There is a lot to offer.

That is, in the present invention, the amount of aggregate is 2 to 4 times the weight of cement.
A cement composition for surface finishing, which contains 1 to 8% by weight of an expanding agent and 0.01 to 1% by weight of chopped strand glass fibers with a fiber length of 5 to 25 mm based on the solid content of the cement. .

The cement used in the present invention is a commercially available cement such as a general hydraulic cement, such as Portland cement, white cement, or a mixed cement such as fly ash cement, silica cement, alumina cement, or jet cement, and if necessary, silicic acid. Hydraulic substances such as calcium or gypsum are added.

Examples of the dry aggregate include sand such as silica sand, river sand, and perlite, and other materials that can be appropriately mixed include talc,
These include clay, asbestos and rock wool powders, dispersants, hardening accelerators, retarder-1 waterproofing agents, pigments, etc.

The aggregate has a diameter of 5 mm or less, preferably 2 mm or less, and is 2 to 4 times the weight of the cement, particularly preferably 2.5 to 3.5 times the weight of the cement.

If the amount of sand is less than 2 times the weight, the drying shrinkage rate of the cement mortar will be large and cracks will easily occur.

In addition, the larger the amount of sand, the lower the drying shrinkage rate and suppress the occurrence of cracks, but if it exceeds 4 times the weight, workability will be extremely reduced, construction will be difficult, and on the contrary, it will induce the occurrence of cracks. .

Expanding materials that can be applied to the present invention include, for example, bauxite lime, calcium oxide obtained by pulverizing clinker obtained by calcining gypsum, calcium sulfoaluminate (C8A)-based expanding materials whose main components are sulfuric anhydride and alumina, and limestone powder (Cab ) and anhydrous gypsum (CaSO4) as main raw materials, gypsum-based expansive material obtained by firing and pulverizing, or lime-based expansive material in which canusium oxide crystal grains are dispersed in calcium silicate crystals and glass phase, etc. The expansive material is hydrated in cement or reacted with tricalcium aluminate (3CaOjA1203) such as a gypsum-based expansive material to form ettringite (3Ca Ot A l 03°3
It has the effect of generating Ca SO, i t 32 R20), expanding the cement mortar in the hardening process, and densifying the structure.

The amount of the expanding agent mixed is 1 to 8% by weight, preferably 3 to 4% by weight, based on the cement.

If the amount of expansion material mixed is less than 1% by weight, the drying shrinkage rate will not be reduced and cracks will occur.

If it is used in an amount exceeding 8% by weight, it is not preferable because it reduces workability and increases costs.

Furthermore, the glass fiber used in the present invention is a glass fiber made of E glass or C glass, or a glass fiber coated with a resin having alkali resistance, or a glass fiber coated with Zr salt and fired, or a glass fiber containing at least 3 mol % of ZrO□. It is a glass fiber containing.

Among these glass fibers, alkali-resistant glass fibers are preferred because they are less corroded by strong alkali components in cement and maintain fiber strength over a long period of time, and particularly contain at least 5 mol%, preferably at least 9 mol%, of Z F02. Glass fibers, such as fibers obtained by melt-spinning glass having the following composition range, are desirable.

Composition (mol%) S 102 50-69ZrO29
~14 R20 (NatLi) 10-25 to 20
1~7 R'0 0~10CaF2
0-2 B203 0-7 P205 0-5 (Other metal oxides) 0-10 F2 0-3 However, the total of R20 and 20 is 14-25 mol%,
R' is an alkaline earth metal or Z n 2M n t Pb
It is.

Other metal oxides include A1203, T i02 Fe,
! Os. Ce02t 5n02 etc. and fluoride is F2
It can be converted into .

The glass fiber used in the present invention is an aggregate of single fibers, for example, 100 to 1,000 single fibers of 5 to 30μ, or several to several tens of fibers to be bundled, and then 5
It is chopped strand glass fiber cut to ~25 mm, preferably 10 to 20 mm.

If the fiber length is less than 5 mm, the desired crack prevention effect cannot be obtained, and if it exceeds 25 mm, it becomes difficult to mix uniformly into cement mortar, which reduces workability, which is not preferable.

The amount of chopped strand glass fiber mixed is 0.01 to 1% by weight, preferably 0.1 to 0.5% by weight, based on the cement solid content.

If the amount is below this range, it is not possible to prevent the occurrence of cracks, and if it exceeds this range, this will result in a decrease in workability and an increase in the price of mortar for plastering, which will be a practical problem.

Moreover, the glass fiber is not the chopped strand,
If the same amount of unbundled single fibers cut to the same length are mixed in, uniform dispersibility and workability will be poor, and the intended crack prevention effect will not be obtained.

The chopped strand glass fibers mixed into the cement mortar forcibly restrain the expansion of the cement mortar caused by the action of the mixed expanding agent, introduce self-stress into the whole, significantly reduce drying shrinkage, and prevent cracks. In addition, during construction, the initial curing is performed uniformly due to the water retention property generated between the single yarns of the chopped strand glass fibers.

Next, embodiments of the present invention will be described with reference to a specific example.

First, a predetermined amount of cement, sand, and expansive material are dry-mixed.

The amount of water to be added at this time is 30 to 90% of the cement.
It is about % by weight.

Glass fibers are added to the resulting slurry and stirred to uniformly disperse the slurry before use, or the glass fibers are premixed with cement and admixture materials and water is poured into the slurry and kneaded before use.

The mortar coating method that can be prepared in this manner includes two or three coatings of a base coat and a top coat, and the cement composition for surface finishing according to the present invention can be applied only as a base coat or a top coat as necessary. The product does not cause fluctuations in the effects and deterioration of mortar strength due to conventional expanding materials, and minimizes the amount of mixing of expanding materials and glass fibers, especially alkali-resistant glass fibers, which pose problems in terms of cost. It is a dog of extremely practical value that has preventive ability and is inexpensive and can impart water resistance and fire resistance to civil engineering, building structures, and molded objects without impairing the workability and workability of conventional cement mortar. It is something.

The present invention will be explained below with reference to Examples.

The drying shrinkage ratio shown in the examples was measured according to the following method.

Drying shrinkage rate JCEAS (Japan Cement Technology Association Standard Test Method) H-
11-1962, the sample was heated to 20±2°C, 76%RH.
The drying shrinkage rate (%) after 28 days of being kept in the atmosphere is shown.

Example 1 The amount of river sand with a maximum particle size of 3 mm was varied with respect to ordinary Portland cement, and 44% by weight of an expanding agent [calcium sulfoaluminate type, trade name Denka C8A#20 (Denki Kagaku Kogyo Co., Ltd.)] was added to water. 60% by weight was added and mixed uniformly, and further the glass composition was mol% Sio2: 68
, ZrO2: 9, Na2O: 15, 20:4
．． A strand of B2O3:4, consisting of 204 fibers with a diameter of 13μ, was cut into 13mm length and mixed with 0.3% by weight based on the solid content of the cement to prepare mortar, and the concrete wall thickness was 101nrIL. 4m x 4
Construction was carried out on the surface of m using a metal trowel.

The drying shrinkage rate of the applied mortar and the presence or absence of cracks were measured and the results are shown in Table 1.

As is clear from the above table, when the amount of river sand is 2 to 4 times the weight of cement, especially 2.5 to 3.5 times the amount of cement, the drying shrinkage rate is increased due to the synergistic effect of mixing the expanding agent and chopped strand glass fiber. The cracks were small and no cracks were observed even after 6 months.

Example 2 Ordinary Portland cement was mixed with 3 times the weight of river sand with a grain size of 3 mm or less, 70% by weight of water, and various addition amounts of the expanding agent shown in Example 1, and then the solid cement was mixed. With respect to minutes, the glass composition is 5t02 in mol%
:63. ZrO2: 121Na20: 15,
20: 55 B2O3: 5 and fiber diameter 15
Cement mortar was prepared by cutting 204 μ strands into 10 mm pieces and uniformly stirring and mixing the mixture in varying amounts.

The cement mortar was applied to each concrete wall by 4rrL.
The coating was applied to a coating thickness of 5 mm on a 3 m surface using a metal trowel, and the drying shrinkage rate and the presence or absence of cracks after 6 months were measured.

The results are shown in Table 2. As is clear from the above table, when the amount of expansion material mixed is 1 to 8% by weight, especially 3 to 4% by weight, due to the synergistic effect with the chopped strand glass fiber, the drying shrinkage rate is extremely small and cracks are observed. I couldn't.

Example 3 3.5 times the weight of river sand with a grain size of 5mvt or less compared to ordinary Portland cement, and 33.5% by weight of an expansive material [lime-based, Shokona J Onoda Expan (manufactured by Onoda Cement ■)] were added to water. was added in an amount of 80% by weight and mixed uniformly to prepare a cement mortar.

The glass composition is 5i by weight with respect to the cement mortar.
02:55. ZrO2: 13. 20:5. MgO
:8, Na-20: 15, B2O3: 4, the fiber diameter is 11μ, a strand consisting of 204 fibers,
A predetermined amount of the mixture was added by changing the cutting length, and the mixture was stirred and mixed uniformly.

The cement mortar was used as a 3 m x 3 m dog lath base.
It was constructed on a wooden wall to a thickness of 13 mm, and the workability, finish of the construction surface, and presence or absence of cracks were evaluated according to the contents shown in Table 3.The results are shown in Table 4.

As shown in the table above, the length of the chopped strand glass fiber is in the range of 5 to 25 mm, particularly 10 to 20 mm, and the amount of the glass fiber mixed is 0.01 to 1% by weight, especially o, i. When applied in the range of ~0.5% by weight, the finish of the workable surface was good and an excellent crack prevention effect was obtained.

Claims (1)

[Claims] 1. Aggregate is 2 to 4 times the weight of cement, and expansion material is 1 times the weight of cement.
Chopped strand glass fiber of ~8% by weight and fiber length of 5~25 mm is added to the solid content of the cement at 0.01~8% by weight.
A surface finishing cement composition containing 1% by weight. 2. The cement composition for surface finishing according to claim 1, wherein the amount of aggregate mixed is 2.5 to 3.5 times the weight of cement. 3. The cement composition for surface finishing according to claim 1, wherein the amount of the expanding agent mixed is 3 to 4% by weight based on the cement. 4. The surface finishing cement composition according to claim 1 or 3, wherein the expanding material is calcium sulfoaluminate. 5. Claim 1, wherein the chopped strand glass fiber contains at least 5 mol% of ZrO□
A cement composition for surface finishing as described in . 6 The fiber length of chopped strand glass fiber is 10~
The cement composition for surface finishing according to claim 1, which is 201n11L. 7. The surface finishing cement composition according to claim 1, wherein the chopped strand glass fiber is mixed in an amount of 0.1 to 0.5% by weight based on the cement solid content.