JPH0717428B2 - Plastering cement composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cement composition for plastering, and more specifically, by adding slaked lime and calcium carbonate to cement or mortar, particularly in winter, that is, at low temperature. The present invention relates to a cement composition for plastering that enables early development of strength.

[Conventional technology]

Cement is usually water and aggregates such as sand and gravel,
Adhesion enhancer with polymer emulsion such as ethylene vinyl acetate, acrylic, styrene butadiene rubber, etc., if necessary, shrinkage reducing agent mainly for gypsum, thickener for increasing water retention, flow of kneaded material Additives or additives (additives) such as a water-reducing agent for increasing the property and AE agent (air entraining agent) characterized by containing air bubbles, and kneaded to be used as a slurry.

When such a cement slurry is used as a wall coating or floor coating material, a slurry (mortar) is prepared by adjusting the amount of aggregate and water mixed and the particle size of the aggregate according to the coating thickness. After applying it to the floor surface, when the water content in the mortar is absorbed by the substrate and the dryness (tightness) is moderate, pressing work such as fixed wood scraping, wooden iron presser, and iron iron presser is performed.

In addition, the cement slurry is a self-leveling material (hereinafter,
It is called "SL material". ), Which is a fluidized mortar, which gives a naturally smooth floor by flowing over the floor surface.

[Problems to be solved by the invention]

The curing reaction of the cement slurry depends on the temperature of the slurry itself,
It greatly changes depending on the environmental temperature at the construction site, and for example, strength development in the winter period may take about 5 times as much as strength development in the summer period.

Since tightening is delayed during the winter, in some cases, it may be necessary to wait 5 to 10 hours after application to perform the pressing work. For this reason, most of the working time per day is spent on the waiting time until the mortar is tightened, and the workable time for applying the mortar to the wall becomes short.

When finishing with a coating thickness of about 1 mm (for example, cement filler by the Housing and Urban Development Corporation), resin mortar that uses a polymer emulsion together with cement and aggregate is used, but with resin mortar, hardening is generally delayed. Are known and have problems similar to those mentioned above and also contribute to the problems mentioned above.

Also, not only during the winter season, tightening is affected by environmental conditions such as temperature, humidity and wind speed at the site, and the dry condition of the base,
The tightness varies from wall to wall because it is affected by the compactness of the base.

In such a case, if the pressing work is performed earlier than the proper pressing timing, the wall will not be flattened due to the movement of the mortar after the pressing work. On the other hand, if the work is carried out at a later time than the timing of the proper presser work, a strong force is required to perform the work clamp, which increases the fatigue of the worker and causes the work to stick when the work force is forced. It may result in peeling off the existing mortar (called "fir-floating").

Therefore, in order to solve such a problem, it is desirable to be able to adjust the mortar so that the tightening occurs at an appropriate speed depending on the type of the mortar, the environment of the site, and the like.

In the summer, direct sunlight is applied to the coated surface, and depending on the dry condition of the base and the construction environment (mainly the wind speed at the construction site, the temperature, and the humidity near the wall surface), even the water necessary for the mortar to harden. However, there is a problem that curing failure (referred to as “dryout”) is caused.

Further, depending on environmental conditions, particularly humidity and wind speed, the protrusion of calcium in the mortar to the coated surface, that is,
There is a problem that white sinter occurs, and if this is large, it becomes impossible to directly apply a material having a cosmetic property (finishing material) to the coated surface.

In the case of SL material, it is advantageous to construct a large area at once to improve the construction accuracy and work efficiency. However, if the SL material that has flowed to the floor is in an uncured state or is in a state where it is hardened but does not have sufficient strength (the state “before the end of curing”) for a long time, the aggregate used in the SL material There is a problem of sedimentation of the SL material and freezing of the SL material in the severe winter, and the SL material construction worker and those who work in the vicinity cannot get on the SL material before curing and put things on it. There is also a problem that the SL material becomes a physical obstacle at the work site because light work cannot be performed.

[Means and Actions for Solving Problems]

As a result of intensive studies to solve the problems of the conventional techniques as described above, the present inventor has added calcium carbonate together with slaked lime to cement or mortar to obtain a strength (hereinafter, referred to as “ The present invention has been completed by finding that the strength can be improved especially in the winter period.

That is, the present invention is a plastering cement composition containing 5 to 40 parts by weight of slaked lime with respect to cement and 5 to 150% by weight of calcium carbonate.

When the amount of calcium carbonate in the above composition range is small with respect to slaked lime (for example, about 5 to 30% calcium carbonate of slaked lime), the plastering cement composition according to the present invention exhibits a very weak pseudo-caking property. In this composition range
The initial strength effect is exhibited in SL material. The pseudo-coagulation property is lost when SL material is flown, that is, when a strong force is applied to the slurry such that the slurry is stirred in the mortar pump or pipe, or when the stirred slurry is flowed to the floor surface at the pipe outlet. However, when the slurry is flowed on the floor and left standing, pseudo-aggregation appears and the fluidity of the slurry is lost. As a result, there is an effect that the separation of aggregate is reduced. When the hardening retarder is used together, the amount of water required for the work of flowing the SL material decreases, so if the amount of the hardening retarder is within the range of 0.01 to 0.05% relative to the cement, the decrease in strength on the next day of the work is particularly large. However, there is a decrease in the curing shrinkage amount, which is considered to be due to the decrease in the kneading water amount. Regarding hardening, as compared with a cement-only system containing neither slaked lime nor calcium carbonate, or a cement system containing either slaked lime and calcium carbonate, the cement system containing both slaked lime and calcium carbonate according to the present invention is harder. The speed is high, and the degree of hardening promotion is remarkable at low temperature as compared with normal temperature and high temperature.

When used as a mortar for wall coating, the pseudo-caking property does not pose a problem, and the same coating operation as that for a normal cement-only system can be performed. There is no significant difference in the water drainage and the presser foot after coating from the cement-only system. The cure is slightly faster and a slight acceleration of cure at low temperatures is seen.

When the amount of calcium carbonate increases, for example to the extent of about 30 to 50% by weight of slaked lime, the cement composition according to the invention is
When used as an SL material, it must be used in combination with a set retarder. If it is not used in combination with a curing retarder, the pseudo-caking property is so strong that it is impossible to flow the SL material to the floor surface after about 30 minutes after kneading.

When used as a wall coating material, there is no significant difference in the coating operation between the plastering cement composition of the present invention and the cement-only system. In the examples, with the composition according to the present invention, the amount of mixed water capable of performing the same work is slightly increased, and accordingly, the workability of application is slightly improved with the composition according to the present invention.

There is a great difference in the work for suppressing the iron, and it has been shown that the composition according to the present invention can suppress the iron in a short time after application.

When the amount of calcium carbonate further increases and approaches the amount of slaked lime, that is, 50 to 100% of slaked lime, it is not suitable as an SL material, but when it is used as a mortar applied to a wall, it becomes Viscosity changes appear relatively early. For this reason, when using it as a mortar, it is necessary to increase the amount of mixed water, which seems to be the effect, but with regard to the workability of application, especially the mortar for applying work on the iron, The area where the mortar is applied to the movement of the mortar (hereinafter referred to as "mortar elongation") and the degree of surface accuracy when the mortar surface is pressed with a trowel immediately after the application (hereinafter referred to as "trowel back"). Has been improved. Furthermore, it was confirmed that the iron could be suppressed even when the water in the mortar was not sufficiently lost to suppress the iron in about 30 minutes after application.

Regarding the curing, the composition according to the present invention cures faster than the conventional example, and the degree of hardness after one day at a low temperature is improved. In the example, the mortar was frozen 5 hours after application,
After that, it was thawed and the degree of adhesion was immediately confirmed, and it was confirmed that the adhesive strength was sufficient.

With respect to white sinter, the examples show that the degree of white sinter is reduced.

When the amount of calcium carbonate exceeds the amount of slaked lime (for example, about 100-150% calcium carbonate of slaked lime),
The pseudo-caking property is further increased, and it is difficult to perform on-site construction with ordinary cement and aggregate systems. But usually
Substrate conditioner used with a coating thickness of 1 mm or less (JIS A 6916)
In the field, since it is generally used in combination with a polymer emulsion, on-site construction is possible about 30 minutes after kneading in winter. A cement composition for plastering in such a composition range is useful in applications requiring an initial strength that is more rapid than in workability, such as work in which construction time and curing time cannot be sufficiently taken.

Although the above has been described in relation to the composition of slaked lime and calcium carbonate, the boundary is not clear and changes gradually, and the above description shows a general tendency.

In the example, the coating workability is improved by increasing the kneading water amount,
It was confirmed that the iron holding time was shortened. Also, the reduction of white flower,
Improved resistance to dryout in summer has been shown.

Gypsum is known to act as a set retarder as well as a swelling agent in cement systems, but if gypsum is added to the cement composition according to the present invention in an amount of 1 to 25% by weight, particularly 4 to 8% by weight of cement. It is useful because a high initial strength can be obtained.

〔Example〕

 The following materials were used in the following examples.

Cement: Ordinary Portland cement specified in JIS R5201 Slaked lime: Grinded reagent grade 1 slaked lime and passed through a 200 mesh sieve Calcium carbonate: Grinded reagent grade 1 calcium carbonate and passed through a 200 mesh sieve Gypsum: Anhydrous gypsum of first grade reagent was crushed and passed through a 200-mesh sieve Sand: JASS 15 Class A, B specified by plaster work (Architectural Institute of Japan)
Seed and C type sand. When the sand used was actually sieved, the following results were obtained.

Thickener A: Water-soluble polyacrylamide compound (Viscomate NS) manufactured by Showa Denko KK Thickener B: Methyl hydroxyethyl cellulose (Cesca MHEC) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. Superplasticizer: Showa Denko KK Melamine formaldehyde condensate sulfonate (Melmet F10) Emulsion: Showa Denko KK ethylene vinyl acetate emulsion (high molar emulsion, solid content 45%) Retarder: Reagent first grade sodium citrate Example 1 Self-leveling material (SL material) I checked. Cement slurries having the compositions shown in Table 1 were prepared and cast. In the table, the composition is based on 100% cement, the weight percentage of calcium carbonate is based on slaked lime, and the weight ratio of water is based on the total weight of all powders. It was However, the amount of calcium carbonate is shown in% by weight with respect to cement in the system where slaked lime is not used.

Whether or not sinking is possible for each sample, 5 ℃
The presence or absence of aggregate separation at 5 ° C. and 20 ° C. after 24 hours of compressive strength (kg / cm ² ) and the pot life at 5 ° C. and 20 ° C. were evaluated. The results are shown in Table 1. In Table 1, sample Nos. 1 to 10 are examples of the present invention.
Nos. 11 to 15 are comparative examples.

From Table 1, according to the ratio of slaked lime and calcium carbonate,
It is shown that the initial compressive strength is changed.

Regarding strength, depending on the ratio of slaked lime and calcium carbonate, there is a ratio that the pot life is shortened and the effect of quick hardening is not sufficient, so by selecting an excessive ratio,
It can be seen that the pot life can be taken and that the strength of the next day can be increased to some extent even in the winter.

Regarding the aggregate separation, the aggregate separation decreases depending on the ratio of slaked lime and calcium carbonate, but the reduction of aggregate separation shows the same direction as the shortening of the pot life. You can see that there is an aptitude ratio.
In addition, it is possible to increase the amount of thickener to prevent the aggregate separation, but because hardening is delayed and the amount of water required to obtain a slurry with the same workability increases, a certain level of initial strength in winter is obtained. If it matters, it is not a suitable method.

Example 2 A wall coating material was investigated. A cement mortar slurry having the composition shown in Table 2 was prepared according to the same criteria as in Example 1, and the slurry was applied to the concrete wall. Evaluation is the pot life of the slurry (up to 1 hour observation), the time from application at 5 ° C and 20 ° C until the iron can be pressed, and the iron elongation during application (○, △, × depending on the quality) Three-stage evaluation),
Freezing resistance (Apply on the concrete sidewalk immediately after adjusting the slurry, cure 5 hours after adjusting the slurry in an atmosphere of -20 ° C, and after 7 days, heat the specimen to 50 ° C to melt the ice, The one that does not peel off is marked with ○, the iron pressing surface (mortar is applied to the concrete wall, the wooden mortar is pressed after the mortar is tightened, and then the gold iron pressing is carried out according to the aesthetic condition of the surface, ○, △, Hardness (4 grades of ◎, ○, △, × depending on the hardness) after 1 day of the winter period at 5 ° C, and resistance to white sinter (no white sinter was observed) And).

In Table 2, sample Nos. 21 to 31 are examples of the present invention, and sample Nos. 32 to 36 are comparative examples.

The following can be recognized from Table 2. However, the ratio of calcium carbonate to slaked lime is expressed as a CaCO ₃ / Ca (OH) ₂ ratio (or simply “ratio”).

Regarding the iron pressing ability, the iron pressing possible time changes depending on the CaCO ₃ / Ca (OH) ₂ ratio, and the higher the ratio, the earlier the iron pressing becomes possible. In each of the samples Nos. 34, 35 and 36 of Comparative Examples, the time required for iron pressing was too long, whereas the composition according to the present invention shortened the time, and the effect of the combined use of slaked lime and calcium carbonate was It is shown. However, when applying the paint at the construction site, it takes a certain amount of time to apply the mortar to the wall, so it is not always appropriate that the iron pressing time is extremely short.

In the freeze resistance test after 5 hours of slurry preparation, among the compositions according to the present invention, those having a short iron pressing time showed that the mortar adhered sufficiently to the concrete sidewalk board after melting.

It is recognized that the composition according to the present invention also includes a composition that is unlikely to cause white bloom in terms of resistance to white bloom.

Example 3 A thin coating material used in combination with a polymer emulsion was investigated.
Mortar slurries having the compositions shown in Table 3 were prepared and applied to concrete walls. In this example, in the same manner as in Example 2, the pot life at 5 ° C. (possible iron pressing time), the quality of the coating workability, and the sinter resistance (evaluated by coating on a concrete plate at 3 ° C.) In addition to the evaluation, the dry-out resistance (applied to a concrete sidewalk board in an environment of 70 ° C and evaluated) was evaluated.

In Table 3, sample Nos. 41 to 43, 45 to 47, 49 to 54
Is an example of the present invention, and sample Nos. 44, 48, 55 to 58 are comparative examples.

Example 4 The effect of adding gypsum was investigated in SL material. Example 1
A cement slurry was prepared in the same manner as in (1) and was then poured. However, in this example, the amount of gypsum added was gradually changed, and citric acid was added except for sample No.67.

In order to evaluate the effect of adding gypsum, each sample was evaluated for strength after 1 day at 5 ° C., workability after 30 minutes of kneading, shrinkage of the cured product, and water resistance. The results are shown in Table 4. The samples in Table 4 are all examples of the present invention.

As can be seen from Table 4, by adding gypsum, the initial strength (strength after 1 day) is improved, the shrinkage rate is reduced, and workability and water resistance are secured. However, if the amount of gypsum exceeds 10% by weight with respect to the cement, there is a problem in water resistance. However, it is effective to add 10% by weight or more of gypsum to increase the initial strength in applications where water resistance is not a problem.

[Effects of the Invention] According to the present invention, the initial strength of the cement or mortar slurry is improved by adding a specific amount of slaked lime and calcium carbonate to the plastering cement composition. As a result, for example, in wall coating applications, the time until pressing after application is shortened, and in self-leveling material applications, the time until light work after sinking work is shortened, and aggregate Separation is prevented, especially these effects are significant during the winter, ie at low temperatures. In addition, the effect of suppressing dryout and expression of white flower was also observed.

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Claims (1)

[Claims] 1. A plastering cement composition for plastering, comprising 5 to 40 parts by weight of slaked lime based on 100 parts by weight of cement, and 5 to 150% by weight of calcium carbonate.