KR100881343B1 - Admixture for cement mortar and cement mortar having the same - Google Patents

Abstract

An admixture for cement mortar is provided to improve workability by optimizing the hydration retarding work and air entraining work due to the adsorption of cement and to increase sag resistance, bending compressive strength and adhesion strength. An admixture for cement mortar comprises (1) hydroxypropylmethylcellulose having the methyl group replacement ratio of 26-32 weight% and the hydroxypropyl group replacement ratio of 0.5-3 weight% or less; (2) at least one kind of cellulose ether of hydroxyethylmethylcellulose having the methyl group replacement ratio of 26-32 weight% and the hydroxypropyl group replacement ratio of 0.5-3 weight% or less; and (3) methyl cellulose having the methyl group replacement ratio of 27-33 weight% or less.

Description

Admixture for cement mortar and cement mortar having the same}

The present invention relates to a cement mortar admixture and cement mortar comprising the same, and more particularly, by minimizing the hydration retardation action and air entrainment of the cement, it is possible to express high strength of the cement mortar and improve the deflection resistance. An admixture for cement mortar and a cement mortar comprising the same.

Various cellulose ether (CE) derivatives prepared using natural cellulose pulp have been widely used as admixtures for cement mortar under the names of thickeners, water refining agents, or material separation reducing agents.

The main reason why these cellulose ethers are used as admixtures for cement mortar is that the cellulose ethers incorporated into the cement mortar do not condense for a predetermined time by performing three basic functions of repair, thickening and air entraining. This improves the properties, prevents separation of materials and increases the strength of the hardened mortar. Here, the term "curing" refers to a concept including a resultant crystal and a process in which cement is hydrated to express strength. Condensation refers to the point at which cement mortar loses its fluidity and becomes impossible to work.

However, these cellulose ethers have a disadvantage of delaying the hydration reaction of cement and inhibiting the initial strength expression of cement mortar. In addition, when a large amount of cellulose ether is used, excessive air inflow may be caused to weaken the sag resistance of the mortar and also lower the final strength of the mortar after curing. The delay of the hydration reaction and the air entrainment of the cement becomes larger as the amount of the cellulose ether added increases.

In particular, in line with the ISO certification system, regulations on the performance of finishing mortars, including tile cement mortar, have been strengthened.However, a method of increasing the amount of cellulose ether added as a way to increase the strength by increasing the water retention of mortar Although it may be considered, the amount of addition of the cellulose ether is limited due to the above disadvantages.

 As a method for minimizing the hydration retardation effect of the cement as described above, a technique using an organic / inorganic hydration accelerator (JP-A-2006-327865, 2006-056763), or in addition to cellulose ether, A technique using a water-soluble thickener (Japanese Patent Laid-Open No. 2001-348256) having a small amount of adsorption is used, and a technique using an antifoaming agent as a means for reducing excessive air intake (Japanese Patent Laid-Open No. 2006-206753 , 2003-313069, 2006-056763) are generally used.

However, in the case of using organic / inorganic accelerators, the hydration reaction time may be too fast or the expected effect may not be obtained due to the slight variation in the amount of addition, which makes it difficult to control the working time or lower the economic efficiency. There is this. Here, the workable time means a time for the cement mortar to maintain the fluidity capable of working. On the other hand, when the antifoaming agent is used to reduce the amount of incoming air, there may be an effect of reducing the amount of incoming air, but it is often accompanied by the adverse effect of delaying the hydration reaction of cement or impairing workability, and also economic efficiency is deteriorated There are disadvantages.

It is an object of the present invention to provide a cement mortar admixture capable of increasing sag resistance, flexural compressive strength and adhesive strength while improving workability by optimizing hydration delay and air inflow amount due to adsorption to cement.

It is another object of the present invention to provide a cement mortar admixture that can reduce the production cost of cement mortar by reducing the use of additional admixtures such as hydration accelerators or antifoaming agents.

It is still another object of the present invention to provide a cement mortar admixture capable of shortening the air of construction work by enabling rapid progress of a post-process by rapid curing of cement mortar.

Still another object of the present invention is to provide a cement mortar comprising the admixture for cement mortar.

The present invention to solve the above problems,

(1) hydroxy propyl methylcellulose having a methyl group substitution rate of 26 wt% or more and 32 wt% or less, and a hydroxy propyl group substitution rate of 0.5 wt% or more and less than 3 wt%; And

(2) at least one cellulose ether of hydroxyethyl methylcellulose having a methyl group substitution rate of 26% by weight to 32% by weight and a hydroxyethyl group substitution rate of 0.5% by weight or more and less than 3% by weight; And

(3) The admixture for cement mortar containing methylcellulose whose methyl group substitution rate is 27 weight% or more and 33 weight% or less is provided.

According to one embodiment of the invention, in the case of containing the three cellulose ethers of (1), (2), and (3), the compounding ratio is (1) :( 2), (1) :( It is 1: 99-99: 1 as a weight ratio of 3) and (2) :( 3), respectively, and when it contains two types of cellulose ethers of said (1) and (3), the compounding ratio is (1): When it is 1: 99-99: 1 as a weight ratio of (3), and contains two types of cellulose ethers of said (2) and (3), the compounding ratio is 1: 2 as a weight ratio of (2) :( 3). 99-99: 1.

According to another embodiment of the present invention, the viscosity of the aqueous solution of cellulose ether having a concentration of 2% by weight in the admixture for cement mortar is 1,000 ~ 70,000mPa.

According to another embodiment of the present invention, the cement mortar admixture further comprises ether starch (Starch ether).

According to another embodiment of the present invention, the amount of the starch ether added is 9: 1 to 4: 6 as a weight ratio of the cellulose ether: ether starch.

In addition, the present invention to solve the above problems,

It provides a cement mortar comprising a admixture according to any one of the above embodiments.

According to one embodiment of the invention, the total amount of admixture is 99.9: 0.1 to 97: 3.0 as a weight ratio of cement: admixture.

According to the present invention, it is possible to provide a cement mortar admixture capable of increasing sag resistance, flexural compressive strength and adhesive strength while improving workability by optimizing hydration delay and air inflow amount due to adsorption to cement.

In addition, according to the present invention, it is possible to provide a cement mortar admixture that can reduce the cost of manufacturing cement mortar by reducing the use of additional admixtures such as a hydration reaction accelerator or antifoaming agent.

In addition, according to the present invention, the admixture for cement mortar can be provided to enable the rapid progress of the post-process by the rapid curing of the cement mortar can shorten the air of the building construction.

In addition, according to the present invention, a cement mortar including the admixture for cement mortar may be provided.

Hereinafter will be described in detail with respect to the cement mortar admixture according to a preferred embodiment of the present invention.

The admixture for cement mortar according to the present embodiment includes (1) hydroxypropylmethyl cellulose having a methyl group substitution rate of 26 wt% or more and 32 wt% or less, and a hydroxypropyl group substitution rate of 0.5 wt% or more and less than 3 wt% and (2) At least one cellulose ether of hydroxyethylmethyl cellulose having a methyl group substitution rate of 26 wt% or more and 32 wt% or less and a hydroxyethyl group substitution rate of 0.5 wt% or more and less than 3 wt%, and (3) a methyl group substitution rate of 27 wt% or more. At least two cellulose ethers selected from the group consisting of methyl cellulose that is up to 33% by weight.

When the cellulose ether is added as a admixture to the cement mortar as described above, the cellulose ether performs a repair, a hydration retardation, and an air inlet action, which will be described in more detail as follows.

Conservative

Mortars for building finishes that use cement as a binder typically have very thin construction thicknesses of about 1 mm to 30 mm. Therefore, a drastic water movement occurs in the absorbent base and the atmosphere immediately after construction, which is called dry out. In the case of tile cement, it is reported that more than 80% of the non-beams dry out in one day. However, for sufficient strength development, it is important to maintain the water necessary for the hydration of cement for a long time in the mortar. Therefore, it is important to design the mortar formulation so that the maximum hydration reaction proceeds within the time when sufficient amount of water is present inside the mortar.

The cellulose ether is to hold the water required for the hydration of the cement for a long time, that is, to perform the repair action.

Hydration Reaction

When cellulose ether is mixed with cement mortar and bibim water, it quickly dissolves in bibim water and develops viscosity. At this time, some unsubstituted OH group of the cellulose ether is adsorbed to Ca ²⁺ ions on the surface of the cement particles, which interferes with the contact between the cement and water, thereby inhibiting the hydration reaction of the cement.

This hydration retardation acts to extend the working time (housework time) of the mortar (Japanese Patent Laid-Open No. 2000-203915), but excessive retardation prevents sufficient hardening of the cement and ultimately the strength of the mortar. It causes the deterioration.

In general, the working time of the cement mortar is about 1 hour after the mortar bibim is sufficient, it is preferable to allow the hydration reaction of the cement to proceed quickly once the construction is completed. However, when the cellulose ether is used in a large amount of 1% by weight or more based on the weight of the cement, the degree of hydration reaction is significantly longer depending on the degree of substitution of the cellulose ether, but it is significantly longer than 5 hours. Sometimes you lose.

Therefore, in order to increase the strength through rapid hydration reaction after construction, it is desirable to design the cement mortar to minimize the amount of cellulose ether adsorbed to the cement within the range to ensure the water retention and working time.

The amount of cellulose ether adsorbed on the cement depends on the substitution rate of the cellulose ether. In general, the amount of cellulose ether adsorbed on the cement decreases as the methyl group substitution rate increases.

Air inlet

Cellulose ether is a kind of surfactant having both hydrophilic and hydrophobic groups at the same time to perform the air inlet action by the surfactant action when the cement mortar.

The amount of air drawn as described above is greatly influenced by the substitution rate of cellulose ether, especially the hydroxypropyl group substitution rate or the hydroxyethyl group substitution rate, and the higher these substitution rates, the higher the air introduction amount. Introduced fine bubbles serve to improve the workability by reducing the friction between aggregates by the ball bearing action in the mortar.

However, excessive air inflow results in lowering the strength of the hardened cement mortar, and also reduces the sag resistance of the cement mortar, that is, the slip resistance, and thus the amount of inlet air in the range in which workability is secured. It is desirable to design cement mortar in a direction that minimizes this.

The present invention is to obtain a cement mortar having high strength expression characteristics and excellent sag resistance by optimizing the various actions of the cellulose ether as described above, hydroxy propyl methyl cellulose (HPMC) having a specific degree of substitution and It provides a admixture for cement mortar comprising at least one cellulose ether of hydroxy ethyl methyl cellulose (HEMC) having a specific degree of substitution, and methyl cellulose (MC) having a specific degree of substitution. will be.

Hereinafter, the admixture for cement mortar according to the present embodiment and the cement mortar including the same will be described in detail.

The hydroxypropyl methyl cellulose of the above (1) has a methyl group substitution rate of 26 wt% or more and 32 wt% or less, particularly 28 wt% or more and 30 wt% or less, and a hydroxypropyl group substitution rate of 0.5 wt% or more and less than 3.0 wt%, In particular, it is preferable that they are 1.0 weight% or more and 2.5 weight% or less. Here, when the methyl group substitution rate is less than 26% by weight, the hydration reaction delay time of the cement is long, and when it exceeds 32% by weight, the productivity decreases. In addition, when the hydroxypropyl group substitution rate is less than 0.5% by weight, the air entrainment is excessively reduced resulting in a decrease in the compressibility of the cement mortar and a decrease in the open time, more than 3.0% by weight In this case, the effect of increasing the strength by suppressing air intake cannot be expected. Here, the open time means the maximum open time that the adhesive strength of the cement mortar can satisfy the relevant adhesive strength regulations.

 The hydroxypropyl ethyl cellulose of the above (2) has a methyl group substitution rate of 26 wt% or more and 32 wt% or less, particularly 28 wt% or more and 30 wt% or less, and a hydroxyethyl group substitution rate of 0.5 wt% or more and less than 3 wt%, particularly It is preferable that they are 1.0 weight% or more and 2.5 weight% or less. Here, the reason for limiting the numerical range of the methyl group substitution rate and the hydroxyethyl group substitution rate is the same as in the case of hydroxypropylmethyl cellulose of the above (1).

 It is preferable that the methyl cellulose of said (3) is 27 weight% or more and 33 weight% or less, especially 29 weight% or more and 31% weight or less. In this case, when the methyl group substitution rate is less than 27%, the solubility is poor and there is a problem in viscosity expression, and the hydration reaction of cement is delayed, and when it exceeds 33% by weight, the productivity is significantly decreased due to the long grinding time during product production. .

 In addition, the viscosity of the cellulose ether is preferably 1,000 to 70,000 mPa s, in particular 4,000 to 50,000 mPa s based on the aqueous solution of cellulose ether having a concentration of 2% by weight. If the viscosity is less than 1,000 mPa · s, the repair ratio is insufficient in the normal use range, if the viscosity exceeds 70,000 mPa · s, the amount of air introduced is too large, there is a fear that the strength of the cement mortar after curing hardened, and the amount of cellulose ether added There is a problem that the cost increases because it increases.

 When all of said (1), (2), and (3) is contained, the compounding ratio is as weight ratio of (1) :( 2), (1) :( 3), (2) :( 3), respectively. It is preferable that it is 1: 99-99: 1, More preferably, it is 30: 70-70: 30, Most preferably, they are 40: 60-60: 40, respectively.

 When it contains said (1) and (3), it is preferable that it is 1: 99-99: 1 as a weight ratio of (1) :( 3), More preferably, it is 30: 70-70: 30. , Most preferably, it is 40: 60-60: 40.

 When it contains said (2) and (3), it is preferable that it is 1: 99-99: 1 as a weight ratio of (2) :( 3), More preferably, it is 30: 70-70: 30. , Most preferably, it is 40: 60-60: 40.

 The admixture for cement mortar having the above configuration may further include ether starch. As the ether starch, modified ether starch such as hydroxypropyl starch or carboxy methyl starch may be used. The reason for adding the ether starch as the admixture for cement mortar is to increase the wettability and open time of the adhesive surface by increasing the compressibility of the mortar and suppressing skinning phenomenon. However, when the amount of the ether starch is added too much, water retention is lowered, which is not preferable because sufficient hydration of cement is not secured.

It is preferable that the addition amount of the said ether starch is 9: 1-4: 6 as weight ratio of the said cellulose ether: ether starch, More preferably, it is 9: 1-6: 4.

On the other hand, the present invention provides a cement mortar comprising a admixture according to the present embodiment. In this case, the total addition amount of the admixture is preferably used in large amounts to ensure water retention as the thickness of the cement mortar to be constructed is thin, and in general, the weight ratio of cement to admixture is preferably 99.9: 0.1 to 97: 3. . If the added amount is less than 0.1, it is not preferable because of lack of water retention, and if it exceeds 3.0, the strength of cement mortar is lowered, which is not preferable.

In addition, the cement mortar of the present invention includes cement and aggregate. As the cement, hydraulic cement such as Portland cement, fly ash cement, aluminous cement, or the like may be used, and color cement may be used. If necessary, hemihydrate gypsum, slaked lime, calcium carbonate, dolomite plaster, and / or clay may be used together. As the aggregate, steel sand, mountain sand, silica sand, lightweight aggregate (for example, pearlite) and the like may be used. In addition, emulsions and / or fibrous materials may be added.

The amount of the aggregate is preferably 30 to 300% by weight relative to the weight of the cement, but the present invention is not limited thereto.

In addition, the cement mortar is kneaded in a predetermined manner by adding water, but water is added in an amount sufficient to ensure workability of the cement mortar which is usually required.

Meanwhile, the cement mortar may include tile cement mortar, tile joint mortar, mason mortar, grout mortar, reinforced concrete repair mortar, cement finishing mortar for repair construction or cement using cement as a binder.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1-4 and Comparative Examples 1-3

Preparation Example 1 Preparation of Cement Mortar

Cement (Acea Cement Co., Ltd., Portland Cement): sand: powder resin (ethylene vinyl acetate-based resin, Wacker company, trade name: RE5012T) was prepared by mixing in a weight ratio of 35: 65: 5.

Preparation Example 2 Addition of Admixture

The cellulose ether and / or ether starch were mixed in the mixing ratios of the following Table 1, respectively, and added to the cement mortar samples prepared in Preparation Example 1 at a ratio of 1.5% by weight to the weight of cement, and then dried.

Preparation Example 3 Mixing of Cement Mortar

Water was poured into each of the dry beam cement mortar samples and mixed for 1 minute and 30 seconds using a mechanical mixer. At this time, water was added in an appropriate amount such that each cement mortar had the same viscosity (550 m 50 mPa s).

Evaluation example

The physical properties of the prepared cement mortar were measured in the following manner.

(1) Intake air amount measurement: measured according to KSF2475. That is, this was determined by the formula of the amount of air introduced (%) = (the specific gravity of cement mortar-the apparent specific gravity of cement mortar) / (the apparent specific gravity of cement mortar) * 100.

(2) Slip measurement: measured according to EN1308.

(3) Setting time measurement: Setting time was measured according to KSL5108.

(4) Open time measurement: The open time of tile cement was measured using absorbent tiles according to EN1346.

(4) Adhesion strength and compressive strength measurement: Tile adhesion strength was measured for 3 days, 7 days and 28 days according to EN1348. At this time, curing was performed only dry curing. In addition, the compressive strength was measured according to KSF2476.

Composition and Weight Ratio of Admixtures Evaluation results HPMC-1 HEMC-1 MC SE Water content Air volume (%) Skid (mm) Setting time (h / min) Open time (min) Adhesive strength (MPa) Compressive strength (MPa) 3 days 7 days 28 days 3 days 7 days 28 days Example 1 60 - 40 - 0.23 16 0.26 7/20 20 0.87 1.12 1.14 25.0 40.0 50.0 Example 2 - 60 40 - 0.235 17.6 0.32 7/05 20 0.88 1.20 1.15 23.0 38.0 49.0 Example 3 45 - 30 25 0.26 20.5 0.12 7/00 30 0.93 1.19 1.22 20.0 35.0 45.0 Example 4 - 45 30 25 0.27 21.6 0.21 6/45 30 0.96 1.17 1.32 19.5 33.6 43.5 Example 5 20 25 30 25 0.26 21.0 0.15 6/50 30 0.95 0.19 1.35 20.2 34.5 44.3 Comparative Example 1 100 - - - 0.25 22.1 0.45 8/15 20 0.71 1.09 1.12 19.3 29.3 38.6 Comparative Example 2 - 100 - - 0.255 23.3 0.49 7/20 20 0.76 1.13 1.11 18.2 28.1 36.7 Comparative Example 3 50 50 - - 0.25 22.0 0.4 7/05 20 0.82 1.15 1.13 20 30 40

Composition and Weight Ratio of Admixtures Evaluation results HPMC-2 HEMC-2 MC SE Water content Air volume (%) Skid (mm) Setting time (h / min) Open time (min) Adhesive strength (MPa) Compressive strength (MPa) 3 days 7 days 28 days 3 days 7 days 28 days Comparative Example 4 100 - - - 0.26 24 1.56 13/00 20 0.72 0.92 1.05 15.0 25.0 31.0 Comparative Example 5 - 100 - - 0.265 25 1.78 15/30 20 0.69 0.89 1.06 14.0 23.0 30.0 Comparative Example 6 - - 100 - 0.24 15.4 0.23 6/40 10 0.65 0.79 0.85 32.4 50.0 62.0 Comparative Example 7 - 75 - 25 0.27 24 0.41 14/05 30 0.74 0.93 1.07 16.0 26.0 32.0

Definitions of terms described in Table 1 and Table 2 are as follows.

① HPMC-1: Hydroxypropylmethyl cellulose having a methyl group substitution rate of 29% by weight, hydroxypropyl group substitution rate of 2.0% by weight, and a 2% aqueous solution having a viscosity of 15,000 CPS.

② HEMC-1: Hydroxyethylmethyl cellulose having a methyl group substitution rate of 29% by weight, hydroxyethyl group substitution rate of 2.0% by weight, and a 2% aqueous solution having a viscosity of 15,000 CPS.

③ HPMC-2: Hydroxypropylmethyl cellulose having a methyl group substitution rate of 23% by weight, hydroxypropyl group substitution rate of 8.5% by weight, and a 2% aqueous solution having a viscosity of 15,000 CPS.

④ HEMC-2: hydroxyethylmethyl cellulose having a methyl group substitution rate of 23% by weight, hydroxyethyl group substitution rate of 8.5% by weight, and a 2% aqueous solution having a viscosity of 15,000 CPS.

⑤ MC: methyl cellulose whose methyl group substitution rate is 30% by weight and the viscosity of 2% aqueous solution is 15,000CPS

⑥ SE: hydroxypropyl starch with viscosity of 6000% of 10% aqueous solution

⑦ Water content: weight of water / weight of cement mortar

Referring to Tables 1 and 2 above, in the case of Examples 1 to 4, the amount of incoming air is generally smaller, the sliding resistance, that is, the sag resistance is larger, and the setting time is shorter than that of Comparative Examples 1 to 5 and 7. And the off time is similar, and the adhesive strength and the compressive strength were excellent. As the condensation time is shortened as described above, the rapid progress of the post-process is possible, and the air of the building construction can be shortened. In addition, it is possible to secure fast setting time, excellent adhesive strength and compressive strength without additional admixtures such as a hydration accelerator or antifoaming agent, thereby reducing the cost of manufacturing cement mortar. In the case of Comparative Example 6 using only one methyl cellulose (MC) as a admixture, the other properties were comparable or better than those of Examples 1 to 5, but the open time and the adhesive strength were very poor.

Although the present invention has been described with reference to the examples, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (7)

(1) hydroxypropylmethyl cellulose having a methyl group substitution rate of 26% by weight to 32% by weight and a hydroxypropyl group substitution rate of 0.5% by weight or more and less than 3% by weight; And (2) at least one cellulose ether in hydroxyethylmethyl cellulose having a methyl group substitution rate of 26% by weight to 32% by weight and a hydroxyethyl group substitution rate of 0.5% by weight or more and less than 3% by weight; And (3) The admixture for cement mortar containing methyl cellulose whose methyl group substitution rate is 27 weight% or more and 33 weight% or less. The method of claim 1, In the case of containing the three kinds of cellulose ethers of (1), (2) and (3), the compounding ratio is (1) :( 2), (1) :( 3), (2) :( 3 Is 1:99 to 99: 1, respectively, and when two cellulose ethers of (1) and (3) are contained, the mixing ratio is 1:99 as the weight ratio of (1) :( 3). When it is -99: 1, and when it contains two types of cellulose ethers of said (2) and (3), the compounding ratio is 1:99-99: 1 as a weight ratio of (2) :( 3), It is characterized by the above-mentioned. Admixture for cement mortar. The method of claim 1, The admixture for cement mortar, characterized in that the viscosity of the aqueous solution of cellulose ether having a concentration of 2% by weight is 1,000 ~ 70,000mPa. The method of claim 1, Admixture for cement mortar characterized in that it further comprises starch ether (Starch ether). The method of claim 4, wherein The amount of the starch ether is added, the admixture for cement mortar, characterized in that 9: 1 to 4: 6 by weight ratio of the cellulose ether: ether starch. Cement mortar comprising admixture according to any one of claims 1 to 5. The method of claim 6, The total amount of the admixture is cement mortar, characterized in that 99.9: 0.1 ~ 97: 3 as a weight ratio of cement: admixture.