JPS62182143A - Cement composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cement composition, and more specifically,
The present invention relates to a cement composition that enables early strength development, especially during winter, ie, at low temperatures, by adding slaked lime and calcium carbonate to cement or mortar.

[Conventional technology]

Cement is usually made with water and aggregates such as sand or gravel.
If necessary, adhesion enhancers using polymer emulsions such as ethylene vinyl acetate, acrylic, and styrene-butadiene rubber, shrinkage reducers such as Sencora, thickeners to increase water retention, and kneaded materials may be added. Additives or additives (additives) such as a water reducing agent to increase fluidity and an AE agent (air entraining agent) characterized by the inclusion of air bubbles are added and kneaded to form a slurry.

When using such a cement slurry as a wall or floor coating material, a slurry (mortar) is prepared by adjusting the amount of aggregate and water and the particle size of the aggregate depending on the coating thickness, and then it is applied to the wall or floor. After applying the mortar to the floor, when the moisture in the mortar has been absorbed by the base and the mortar has become moderately loose (tightened), it is pressed down with a wooden pickpocket, a wooden trowel presser, a metal trowel presser, etc.

In addition, cement slurry is a self-leveling material (hereinafter referred to as
It is called "rSL material". ), which is a fluidized mortar that naturally creates a smooth floor surface by pouring it onto the floor surface.

[Problem that the invention seeks to solve]

The curing reaction of cement slurry varies greatly depending on the temperature of the slurry itself and the environmental temperature at the construction site. For example, it may take about five times longer to develop strength in winter than in summer.

During the winter, the tightening process is delayed, so in some cases, pressing may not be possible until 5 to 10 hours after application. For this reason, there is a problem in that most of the working time in a day is spent waiting for the mortar to harden, which shortens the available working time for applying the mortar to the wall.

When finishing with a coating thickness of about 1 l (for example, cement filler by the Housing and Urban Development Corporation), resin mortar that uses a polymer emulsion along with cement and aggregate is used, but resin mortar generally does not harden. It is known to be delayed and has the same problems as above and also exacerbates the above problems.

In addition, not only in winter, firmness is affected by environmental conditions such as temperature, humidity, and wind speed at the site, as well as by the dryness of the substrate.
The state of tightness varies from wall to wall as it is affected by the density of the base.

In such a case, if the pressing operation is performed earlier than the appropriate timing, the wall will not be leveled due to the movement of the mortar after the pressing operation. On the other hand, if the presser is pressed at a later time than the proper timing, a strong force will be required to press the foot, which will increase the fatigue of the worker, and if the presser is forced too much, it will tend to stick. This may result in peeling off the mortar that is present (referred to as ``massage lifting'').

Therefore, in order to solve such problems, it is desirable to be able to adjust the mortar so that it compacts at an appropriate speed depending on the type of mortar, the environment at the site, etc.

In addition, during the summer, the painted surface is exposed to direct sunlight, and depending on the drying condition of the base and the construction environment (mainly wind speed, temperature, and humidity near the wall surface), the amount of water required for the mortar to harden may vary. There is a problem in that this loss causes poor curing (referred to as "dryout").

Furthermore, depending on the environmental conditions, especially humidity and wind speed, calcium in the mortar may precipitate on the applied surface, i.e.
Efflorescence occurs, and if there is a lot of efflorescence, there is a problem that it becomes impossible to directly apply a cosmetic material (finishing material) to the surface.

In the case of SL materials, it is advantageous to construct a large area at once in order to improve construction accuracy and work efficiency.

However, if the SL material poured onto the floor remains uncured or hardened but not strong enough (state "before hardening"), the aggregate used in the SL material may In addition to the problems of sedimentation and freezing of SL materials during the severe winter,
SLL material workers and those working in the surrounding area cannot stand on the SL material before it has hardened or perform light work such as placing objects on top of it, and as a result, the SL material becomes a physical obstacle at the work site. There is a problem with becoming.

[Means and effects for solving the problems] As a result of intensive research in order to solve the problems of the prior art as described above, the present inventors have discovered that slurry kneading is possible by adding calcium carbonate together with slaked lime to cement or mortar. The present invention was completed based on the discovery that the strength from the second half of the mill to about two days later (hereinafter referred to as "initial strength") can be improved.

That is, the present invention resides in a cement composition containing slaked lime in an amount of 5 to 50 parts by weight based on cement, and calcium carbonate in an amount of 5 to 150% by weight of the slaked lime.

In the above composition range, if the amount of calcium carbonate is small with respect to slaked lime (for example about 5 to 30% calcium carbonate of slaked lime), the cement composition according to the invention exhibits very weak pseudo-setting properties. In this composition range, mainly S
The effect of initial strength is exhibited in L material. Pseudo-setting properties are lost when the SL material is flowed, that is, when a force strong enough to stir the slurry in a mortar pump or pipe is applied, or when the stirred slurry is flowed onto the floor at the pipe outlet. However, when the slurry is poured onto the floor and left to stand still, pseudo-coagulation occurs and the slurry loses its fluidity. As a result, there is an effect that separation of aggregates is reduced. When a hardening retarder is used in combination, the amount of water required for pouring the SL material decreases, so if the hardening retarder is in the range of 0.01 to 0.05% of the cement, the strength on the next day will decrease. Although the decrease is not particularly large, there is a decrease in the amount of curing shrinkage, which is thought to be due to a decrease in the amount of kneading water. Regarding hardening, the cement system containing both slaked lime and calcium carbonate according to the present invention has a higher hardness than a cement system containing neither slaked lime nor calcium carbonate, or a cement system containing either slaked lime or calcium carbonate. The speed becomes faster, and the degree of curing acceleration is more significant at low temperatures than at normal or high temperatures.

When used as a mortar for wall coating, pseudo-setting is not a problem, and the application can be performed in the same way as a normal cement-only system. There is no significant difference between the cement-only system and the water retention and pressure after application. Curing is slightly faster and there is a slight acceleration of curing at lower temperatures.

The amount of calcium carbonate is, for example, about 30-50% of slaked lime.
% by weight, the cement composition according to the invention needs to be used in combination with a set retarder when used as a SL material. If it is not used in combination with a curing retarder, it will be impossible to pour the SL material onto the floor after about 30 minutes of kneading due to its strong pseudo-setting properties.

When used as a wall coating, no significant differences are observed between the cement compositions according to the invention and cement-only systems in terms of application performance. In the examples, the amount of mixed water that can perform the same work is slightly increased with the composition according to the present invention,
Correspondingly, the coating workability is slightly improved in the composition according to the present invention.

There is a large difference in the troweling work, and it has been shown that the composition according to the present invention can be troweled in a short period of time after application.

Furthermore, when the amount of calcium carbonate increases and approaches the amount of slaked lime, that is, 50 to 100% of slaked lime, SL
Although it is not suitable as a material, when used as mortar for coating walls, the viscosity of the slurry changes relatively quickly. For this reason, when using it as mortar, it is necessary to mix a large amount of water, but this seems to be an effect, but the workability of application, especially mortar that is applied on a trowel, is affected once. The area covered by mortar relative to the movement of the trowel (hereinafter referred to as ``mortar elongation'') and the degree of surface accuracy when the mortar surface is pressed down with a trowel immediately after application (hereinafter referred to as ``trowel return''). has been improved. After further painting 3
It was confirmed that troweling can be performed even after approximately 0 minutes have elapsed and water in the mortar has not been lost to a sufficient extent for troweling.

As for curing, the composition produced by Zero-Hatsu-no-Koyo cures more quickly than the conventional example, and the degree of hardness after one day at low temperature is improved. In addition, in the example, the mortar was frozen 5 hours after application,
After thawing, the degree of adhesion was immediately checked, and it was confirmed that the adhesion strength was sufficient.

Regarding efflorescence, the examples show that the degree of efflorescence is reduced.

When the amount of calcium carbonate exceeds the amount of slaked lime (for example, about 100 to 150% calcium carbonate of slaked lime), the pseudo-setting properties become even greater, making it impossible to install on-site with ordinary cement and aggregate systems. Have difficulty. However, the base conditioner (JIS
In the field of A 6916), it is common to use it in combination with a polymer emulsion, so it can be applied on-site within about 30 minutes after kneading during the winter. In addition, for applications that require rapid initial strength rather than workability, such as construction work where sufficient construction time and curing time cannot be taken,
Cement compositions having such composition ranges are useful.

The above explanation has been made in relation to the compositions of slaked lime and calcium carbonate, but the boundaries are not clear and change gradually, and the above explanation shows a general tendency.

In the example, application by increasing the amount of mixed pure water improves workability,
It was confirmed that the ironing time was reduced. It also reduces efflorescence,
Improved resistance to summer dryout has been shown.

Ceracola is known to act as a hardening retardant as well as a swelling agent in cement systems, but when the cement composition according to the invention is further added with 1 to 25%, especially 4 to 8% by weight of the cement, Ceracola This is useful because it provides high initial strength.

〔Example〕

In the examples below, the following materials were used.

Cement: Ordinary Portland cement as specified in JIS R5201 Slaked lime: Reagent grade 1 slaked lime crushed and passed through a 200 mesh sieve Calcium carbonate: Reagent grade 1 calcium carbonate crushed and passed through a 200 mesh sieve Ceracola: Reagent grade 1 anhydrous Ceracola is crushed and passed through a 200 sieve sieve Sand: A specified in JASS 15 Plastering (Architectural Institute of Japan)
Sand of species, B species, and 0 species. When the sand used was actually sieved, the following results were obtained.

[Unit: fin (particle size) 1% (amount)] Thickener A: Water-soluble a, f lyacrylamide compound (Viscomate NS) manufactured by Showa Denko ■ Thickener B: Methyl hydroxyethyl cellulose (manufactured by Daiichi Kogyo Seiyaku ■)
Flow agent: Showa Denko side-type melamine formaldehyde condensate sulfonate (Melmet F 10) Emulsion: Showa Denko ■ Ethylene vinyl acetate emulsion (high mole emulsion, solids 45%) Retarder: Reagent 1 An investigation was conducted on the grade sodium citrate flame self-leveling material (SL material).

A cement slurry having the composition shown in Table 1 was prepared and poured. In the table, the composition is 100% cement, except that calcium carbonate is the weight % of slaked lime, and water is the weight % of the total powder, all other powders are in the system relative to cement. is expressed in weight percent relative to cement.

For each sample, check whether it is possible to run the sample at 5°C.
The presence or absence of aggregate separation at 5°C and 20°C, the compressive strength (kg/c+) after 24 hours at 5°C and 20°C, and the pot life at 5°C and 20°C were evaluated. The results are shown in Table 1.

According to Table 1 in the margin below, depending on the ratio of slaked lime and calcium carbonate,
It is shown that the initial compressive strength changes.

Regarding strength, depending on the ratio of slaked lime and calcium carbonate, there are some ratios that shorten pot life and do not have enough fast hardening effect, so by selecting an appropriate ratio,
It can be seen that the pot life is long and that a certain degree of next-day strength can be produced even during winter.

Regarding aggregate separation, aggregate separation decreases depending on the ratio of slaked lime and calcium carbonate, but since the decrease in aggregate separation shows the same direction as the shortening of pot life, from this point of view as well, the ratio of slaked lime and calcium carbonate is It turns out that there is an appropriate ratio.

In addition, it is possible to increase the amount of thickener to prevent aggregate separation, but this will delay curing and increase the amount of water required to obtain slurry with the same workability. This is not a suitable method when strength is an issue.

``Thorn'' - I researched wall coating materials. A cement mortar slurry having the composition shown in Table 2 was prepared on the same basis as in Example 1, and the slurry was applied to a concrete wall. The evaluation was based on the pot life of the slurry (observed for up to 1 hour), the time from application at 5℃ and 20℃ until it can be stretched with a trowel, and the elongation with a trowel during application (○, Δ, depending on quality). ×3-level evaluation),
Freeze resistance (Apply to concrete sidewalk boards immediately after slurry preparation, cure in an atmosphere of -20℃ 5 hours after slurry preparation, and after 7 days, heat the specimen to 50℃ to melt the ice and cause the mortar to peel off.) (Those that do not are marked as ○), trowel-stretched surface (apply mortar to the concrete wall, press with a wooden trowel after tightening the mortar, and then press with a metal trowel. Depending on the aesthetic condition of the surface, ○, △, hardness after 1 day in winter at 5°C (according to hardness)
.

A four-level evaluation of ◯, △, and ×) and efflorescence resistance (no efflorescence was rated as ◯) were performed.

From Table 2, the following is recognized. However, the ratio of calcium carbonate to slaked lime is CaC0, /Ca(01
1) Expressed as 2 ratio (or simply "ratio").

Regarding the troweling performance, the time that can be troweled changes depending on the ratio of CaC03/Ca (Oll), and the higher the ratio, the earlier the troweling becomes possible. Comparative example sample light 3
5, 36, and 37, the time until troweling was too long, whereas the composition according to the present invention shortened that time, demonstrating the effect of the combined use of slaked lime and calcium carbonate. However, when painting work at a construction site, it takes a certain amount of time to apply mortar to the wall.
It is not necessarily appropriate that the troweling time be extremely short.

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

Regarding the efflorescence resistance, it is recognized that the composition according to the present invention contains a composition that does not easily cause efflorescence.

劃”- We investigated thin coating materials that use polymer emulsions in combination.

A mortar slurry having the composition shown in Table 3 was prepared and applied to a concrete wall. In this example, in the same way as in Example 2, the pot life at 5°C (temperature that can be pressed with a trowel)
In addition to evaluating the quality of application workability and efflorescence resistance (evaluated by applying it to a concrete board at 3℃), we also evaluated its dryout resistance (evaluating it by applying it to a concrete sidewalk board at 70℃) ) was evaluated.

In the following margin, we investigated the effect of Ceracola addition on 1-3L materials. A cement slurry was prepared in the same manner as in Example 1, and a pouring operation was performed. However, in this example, the amount of Ceracola added was gradually changed, and citric acid was added except for sample N177.

In order to evaluate the effect of Ceracola addition, each sample was evaluated for strength after one day at 5°C, workability after 30 minutes of kneading, shrinkage rate of the cured product, and water resistance. The results are shown in Table 4.

As shown in Table 4 below, by adding Ceracola, the initial strength (strength after 1 day) was improved, the shrinkage rate was reduced, and workability and water resistance were ensured. However, if the amount of Ceracola exceeds 10% by weight based on the cement, there will be a problem in water resistance. However, in applications where water resistance is not an issue, it is effective to increase the initial strength by adding 10% by weight or more of Ceracola.

〔Effect of the invention〕

According to the present invention, the initial strength of cement or mortar slurry is improved by incorporating specific amounts of slaked lime and calcium carbonate into a cement composition. the result,
For example, in wall coating applications, the time required to press down after application is shortened, and in self-leveling applications, the time required to perform light work after pouring is shortened, and aggregate separation is prevented. These effects are particularly noticeable during the winter, that is, at low temperatures. In addition, the effect of suppressing dryout and efflorescence was also observed.

Claims (1)

[Claims] 1. A cement composition characterized by containing slaked lime in an amount of 5 to 50 parts by weight per 100 parts by weight of cement, and calcium carbonate in an amount of 5 to 150% by weight of the slaked lime.