KR102536071B1 - Methods for Preparing Shrinkage Reduced Concrete Compositions - Google Patents

Abstract

The present invention relates to technology of reducing the shrinkage of a concrete composition by reducing the surface tension of concrete mixing water through the mixing of polyol. The present invention relates to a method for preparing a concrete composition comprising a binder, mixing water, coarse aggregate, fine aggregate, and a water-reducing agent, wherein the concrete composition further comprises ether polyol for reducing shrinkage, which is prepared by: a step (a) of stirring at least one starting material selected from polyfunctional alcohol or polyfunctional amine and at least one catalyst selected from alkoxide or hydroxide of alkali metal to produce a mixture; a step (b) of adding alkylene oxide to the mixture to produce a reactant through an epoxide reaction; and a step (c) of adding a catalyst adsorbent and water to the reactant and stirring and filtering the mixture to remove the catalyst and impurities. The molecular weight of the polyol is adjusted within the range of 200 to 2,000, and the polyol content is adjusted within the range of 0.5 to 2.0 wt%, compared to the binder, thereby controlling the surface tension of a mixture consisting of the polyol, mixing water, and a water-reducing agent under the condition of the temperature of 20℃ to 30 to 55 mN/m.

Description

Methods for preparing shrinkage reduced concrete compositions {Methods for Preparing Shrinkage Reduced Concrete Compositions}

The present invention relates to a technique for reducing shrinkage of a concrete composition by reducing the surface tension of concrete mixing water by mixing polyol, and provides a method for preparing a concrete composition for reducing shrinkage using an ether polyol for reducing shrinkage.

The causes of concrete cracks are classified as shown in [Reference Figure 1] below.

[Reference Figure 1]

Among the above causes of cracking, cracks caused by material factors can be caused by the quality of raw materials such as cement and aggregate, and excessive unit quantities. The volume change of concrete occurs due to this, and this volume change causes cracks.

Shrinkage of concrete can be classified into plastic shrinkage, self-shrinkage, drying shrinkage, and carbonization shrinkage depending on the cause and mechanism, and various studies are being conducted to reduce such shrinkage. The following [Reference Figure 2] schematically shows the occurrence time of each contraction.

[Reference Figure 2]

Plastic Shrinkage has a great influence depending on the construction area and is a matter that must be controlled by construction management.

Carbonation shrinkage is a matter that requires long-term management of buildings because it is caused by the reaction between calcium hydroxide, a hydration product, and carbon dioxide and moisture in the atmosphere.

Autogenous Shrinkage occurs when the volume of concrete decreases as the relative humidity in the pores decreases as the hydration reaction proceeds, and it can be controlled by optimizing the water-cement ratio and curing method.

On the other hand, drying shrinkage, in which moisture adsorbed to hydrated cement evaporates and decreases in volume, is identified as a materially controllable factor through expansion materials and shrinkage reducing agents. It is to provide a technical idea for reducing drying shrinkage by applying polyol as a shrinkage reducing agent to reduce the surface tension of concrete mixing water.

1. Registered Patent No. 10-1834539 "Low Shrinkage Low Carbon Green Cement Composition Containing Carbon Mineralized Fly Ash and Early Steel Expansion Material and Concrete Applying the Same" 2. Registered Patent No. 10-2148007 "Ultra high strength concrete composition with reduced shrinkage and manufacturing method of ultra high strength concrete using the same" 3. Registered Patent No. 10-1818143 "Non-shrinkage cement mortar composition"

The present invention provides a polyol that can be applied as a concrete shrinkage reducing agent and a manufacturing method thereof, and a shrinkage reducing concrete composition manufacturing method for controlling the surface tension of the polyol, mixing water and water reducing agent mixture by adjusting the molecular weight and content of the polyol Its purpose is to provide

The present invention is a method for producing a concrete composition comprising binder, mixing water, coarse aggregate, fine aggregate, and water reducing agent, wherein the concrete composition includes (a) a starting material of at least one of polyfunctional alcohol or polyfunctional amine and an alkali metal Stirring at least one catalyst of an alkoxide or a hydroxide to form a mixture; (b) generating a reactant through an epoxide reaction by adding alkylene oxide to the mixture; and (c) adding and stirring a catalyst adsorbent and water to the reactant, followed by filtering to remove the catalyst and impurities; Further comprising an ether polyol for a shrinkage reducing agent prepared through, adjusting the molecular weight of the polyol within the range of 200 to 2,000, and adjusting the polyol content within the range of 0.5 to 2.0 wt% compared to the binder, the polyol, formulation It provides a shrinkage-reducing concrete composition manufacturing method characterized by controlling the surface tension of the water and water reducing agent mixture at 20 ° C. to 30 to 55 mN / m.

The polyfunctional alcohol is ethylene glycol, propylene glycol, dipropylene glycol, glycerine, trimethanolpropane, pentaerythritol, dipentaerythritol (Dipentaerythritol), alpha methyl glucoside (α-methylglucoside), xylitol (Xylitol), sorbitol (Sorbitol) and sugar (Sucrose) may be any one or more,

The multifunctional amine is ortho-toluene diamine (o-toluene diamine), trimethanol amine (Triethanol amine), ethylene diamine (Ethylene diamine), diphenyl methane diamine (Diphenyl methane diamine) and diethylene triamine It may be any one or more of them.

In addition, the alkali metal alkoxide is any one or more of sodium methoxide (CH ₃ ONa) and potassium methoxide (CH ₃ OK),

The hydroxide may be any one or more of potassium hydroxide (KOH) and sodium hydroxide (NaOH).

In addition, the alkylene oxide may be any one or more of ethylene oxide, propylene oxide, and butylene oxide.

In addition, at least one of magnesium silicate and aluminum silicate may be used as the catalyst adsorbent.

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In addition, the water reducing agent may be included in an amount of 0.5 to 1.5 wt% compared to the binder.

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According to the present invention, by preparing a polyol that can be applied as a concrete shrinkage reducing agent, and controlling the surface tension of the concrete polyol, the mixing water, and the water reducing agent mixture through adjusting the molecular weight and content of the polyol, the shrinkage reduction effect of the concrete composition can be obtained. .

[Figure 1] is a graph comparing the amount of drying shrinkage for each molecular weight of polyol.
[Figure 2] is a graph showing the relationship between the surface tension of the mixture of polyol, mixing water and water reducing agent and the amount of concrete drying shrinkage (age 28 days).

In general, polyols are prepared from petroleum-based raw materials and are compounds having two or more -OH groups prepared through addition or condensation of epoxides to compounds having active hydrogens (-OH, -COOH, -NH ₂ ). These polyols are classified into polyether polyol, polyester polyol, and other polyols (Polycarbonate Polyol, Acryl Polyol, Flame retardant polyol, etc.), and are prepared by changing the starting material and molecular weight according to the use. do.

The ether polyol for reducing shrinkage provided by the present invention,

(a) generating a mixture by stirring a starting material of at least one of polyfunctional alcohol or polyfunctional amine and at least one catalyst of alkali metal alkoxide or hydroxide; and

(b) generating a reactant through an epoxide reaction by adding alkylene oxide to the mixture; and

(c) adding and stirring a catalyst adsorbent and water to the reactant, followed by filtering to remove the catalyst and impurities; It is manufactured including.

1. Step (a)

Step (a) is a step of generating a mixture by stirring a starting material of at least one of polyfunctional alcohol or polyfunctional amine and at least one catalyst of alkali metal alkoxide or hydroxide.

The polyfunctional alcohol is ethylene glycol, propylene glycol, dipropylene glycol, glycerine, trimethanolpropane, pentaerythritol, dipentaerythritol Dipentaerythritol, α-methylglucoside, xylitol, sorbitol, and sucrose can be selected and applied.

The multifunctional amine is ortho-toluene diamine (o-toluene diamine), trimethanol amine (Triethanol amine), ethylene diamine (Ethylene diamine), diphenyl methane diamine (Diphenyl methane diamine) and diethylene triamine Any one or more of them can be selected and applied.

As the alkali metal alkoxide, one or more of sodium methoxide (CH ₃ ONa) and potassium methoxide (CH ₃ OK) may be selected and applied.

As the hydroxide, any one or more of potassium hydroxide (KOH) and sodium hydroxide (NaOH) may be selected and applied.

2. Step (b)

The step (b) is a step of generating a reactant (polyol) through an epoxide reaction by adding alkylene oxide to the mixture.

The epoxide reaction is performed for 1 to 8 hours after adding alkylene oxide to the mixture produced in step (a) under conditions of a temperature of 80 to 150° C. and a pressure of -1 kg/cm ² G. In this epoxide reaction process, the reaction is performed by stirring the starting material and the catalyst.

The alkylene oxide has 2 or more carbon atoms, and one or more of ethylene oxide, propylene oxide, and butylene oxide may be selectively used.

The flow rate of the alkylene oxide injection is preferably maintained at 700 to 1,500 kg/hr, and the reaction pressure after injection is maintained at 4.5 kg/cm ² G or less.

The basic reaction mechanism for generating a reactant (polyol) by adding alkylene oxide to the starting material by the steps (a) and (b) is shown in [Scheme 1] below.

[Scheme 1]

3. Step (c)

The step (c) is a step of removing the catalyst and impurities (unreacted alkylene oxide, etc.) by filtering after adding and stirring a catalyst adsorbent and water to the reactants.

The stirring operation is preferably performed after an aging time of about 30 minutes has elapsed after completion of the reaction according to the step (b), and is performed at 50 to 130 ° C. for 30 minutes to 5 hours to sufficiently achieve the catalyst adsorption reaction. After that, the filtration process proceeds.

Metal silicate systems such as magnesium silicate and aluminum silicate may be used as the catalyst adsorbent.

The stirring and reaction process of steps (a) to (c) may be performed using a stainless steel autoclave pressure reactor. It is preferable to apply the present invention after sufficiently washing the reactor and the stirrer with a solvent such as methanol or acetone.

Thereafter, the catalyst and the catalyst adsorbent are removed by filtering the reactants using a filter press, a sparkler filter, or the like.

The filtered reactant is dehydrated at 50 to 150 ° C. to remove moisture and low boiling point substances present in the reactant. At this time, the dehydration pressure is preferably maintained at 50 Torr or less.

Thereafter, an antioxidant may be purchased at 80° C. or less and mixed for 30 minutes to complete the preparation of a polyol for shrinkage reducing agent.

The polyol for shrinkage reducing agent prepared by the above method has a functional group number (average number of hydroxyl groups per molecule of polyol) of 2 or more, a hydroxyl number of 50 to 1,000 mgKOH/g, and a molecular weight (weight average molecular weight, below Same) 100 to 5,000.

On the other hand, when the aforementioned starting material, catalyst, alkylene oxide, catalyst adsorbent, water (after dehydration), and a composition including an antioxidant (hereinafter, abbreviated as 'composition') are 100 parts by weight, the alkylene oxide is a reactant. It is preferable to contain 10 to 95 parts by weight in 100 parts by weight. If the content is less than 10 parts by weight, the reactivity and physical properties are deteriorated, and if it exceeds 95 parts by weight, the viscosity is relatively increased, causing problems in use as a shrinkage reducing agent.

The alkali metal alkoxide or hydroxide catalyst is preferably used in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the composition. If the content is less than 0.1 parts by weight, the reaction time becomes longer and productivity decreases, and if it exceeds 5.0 parts by weight, it is difficult to control the reaction heat and the process for removing the catalyst becomes long, so there is a problem in that the efficiency of the manufacturing process is reduced.

It is preferable to add 0.1 to 5.0 parts by weight of the catalyst adsorbent based on 100 parts by weight. If the added amount is less than 0.1 parts by weight, the amount is too insignificant, and the adsorption capacity of the catalyst is reduced, making adsorption separation and removal difficult.

An ether polyol having a viscosity of 20 to 1,000 cPs and a molecular weight of 100 to 5,000 can be prepared by the above method. However, the ether polyol for application as a shrinkage reducing agent for concrete is preferably prepared in the range of viscosity 50-500 cPs and molecular weight 200-2,000 in consideration of concrete mixing and rheological properties.

[Table 1] below shows the ether polyol for the shrinkage reducing agent prepared by the above method in parts by weight according to the components administered in the manufacturing process.

Components and reaction conditions introduced for the preparation of each test example are as follows.

- Starting material: A polyfunctional alcohol (dipropylene glycol or glycerin) as a starting material,

- Catalyst: Potassium hydroxide (KOH)

- Alkylene oxide: propylene oxide

- Catalyst adsorbent: mixed magnesium silicate and aluminum silicate

[Table 1]

[Table 2] below shows the measured physical properties of each test example of the polyol for reducing shrinkage.

[Table 2]

The appearance was observed as a colorless and transparent liquid in all test examples as a result of visual observation.

Hereinafter, the measurement method for each item is as follows.

- Color: Measured by APHA Color test method

- CPR: CPR measurement method (JIS K 80063, ASTM D 6437-05) applied measurement

- Moisture: Measured with a Karl Fischer moisture meter (ASTM D4672-87, JIS K 0068)

- pH: measured with a pH meter

- Acid value: Measured by applying JIS K 8004 test method

- Hydroxyl value: Measured using the acetic anhydride-pyridine method (JISK 8004-1961, JISK 3342-1961, JISK 3361-1963)

- Viscosity: Measured at 25℃ using Spindle type viscometer DV-Ⅲ from Brookfield

- Specific gravity: measured at 25℃ using a hydrometer

Among the above measurement items, the hydroxyl number is an index indicating the amount of reactive hydroxy groups that can participate in the reaction, and is the number of mg of KOH required to neutralize acetic acid bound to an acetyl compound obtained from 1 g of polyol.

Measuring instruments for the application of the acetic anhydride-pyridine method are Erlenmeyer flask (200ml), air cooling tube (30cm), pipette (5ml, 10ml), burette (50ml) and oil bath,

(1) Put the polyols of Test Examples 1 to 8 and 5ml of acetic anhydride-pyridine method mixture in an Erlenmeyer flask, shake it more than 5 times, attach a cooler and react in an oil bath for 1 hour and 30 minutes

(2) The process of adding 1 ml of distilled water, shaking it more than 5 times, and leaving it in an oil bath for 10 minutes to promote hydrolysis

(3) After taking it out of the oil bath and leaving it at room temperature for 10 minutes, the inner wall of the cooler was washed with 10 ml of acetone, shaken more than 5 times, and then titrated with 0.5N NaOH standard solution by adding 3 to 4 drops of phenolphthalein indicator.

The hydroxyl value for each test example was calculated by [Equation 1] below.

[Equation 1]

Hydroxyl value = [(B-A) × F × 28.05 / S] + acid value

S: amount of sample

B : 0.5N NaOH (ml) required for blank

A: 0.5N NaOH (ml) required for this test

Acid value: acid value of the sample used in this test

The above shrinkage reducing agent ether polyol (hereinafter abbreviated as 'polyol') is incorporated into the concrete composition to lower the surface tension of the mixing water and reduce the amount of concrete drying shrinkage.

Accordingly, the present invention provides a concrete composition containing a binder, mixing water, coarse aggregate, fine aggregate, and a water reducing agent, wherein the polyol is contained in an amount of 0.5 to 2.0 wt% relative to the binder. When the amount of the polyol added exceeds 2.0 wt% compared to the binder, condensation is delayed due to -OH (hydroxyl group) present at the end of the polyol, and compressive strength is reduced.

Under the condition that the polyol content is the same within the above content range, as the polyol molecular weight increases, the surface tension of the blending water decreases and the drying shrinkage of concrete decreases. Under the condition of the same polyol molecular weight, concrete drying shrinkage decreased as the polyol content increased.

[Table 3] below is a concrete mixing table applied to the examination of concrete physical properties according to the molecular weight of the added polyol. 172 kg of water and 300 kg of binder (cement 270 kg, fly ash 30 kg) are mixed per unit volume of 1㎥, water-binder ratio (W/B) 57 wt%, fine aggregate ratio (S/a) 53 vol% was combined with The water reducing agent (AD) was added at 1 wt% compared to the binder.

[Table 3]

[Table 4] shows the results of measuring the surface tension of each molecular weight of polyol, the number of blends, and the surface tension of a mixed solution of polyol and water reducing agent. The polyol content was controlled at 1 wt% compared to the binder. Polyol molecular weights are written in parentheses (the same below). As a surface tension measurement method, 「Du Nouy Ring Method」 was applied.

[Table 4]

[Table 5] summarizes the examination of changes in physical properties of concrete according to the molecular weight of polyol. In each test example, slump and compressive strength by age were found to be at the same level.

[Table 5]

[Table 6] and [Figure 1] below compare the drying shrinkage by molecular weight of polyols. The trend of reducing drying shrinkage according to the increase in molecular weight can be confirmed.

[Table 6]

The surface tension of the mixture of the polyol, the mixing water and the water reducing agent can be controlled by the molecular weight and content of the polyol, and within the above-mentioned polyol content and molecular weight range, the surface tension of the mixture is controlled at 30 to 55 mN/m at 20 ° C. can do.

The attached [Figure 2] is a graph showing the relationship between the surface tension of the mixture and the amount of concrete drying shrinkage (age 28 days). According to the regression analysis based on the graph of [Fig. 2], the following [Equation 1] is derived, and the amount of concrete drying shrinkage can be predicted from the surface tension of the mixed solution by [Equation 1].

[Equation 1]

y=7.77x -162.47

y: Concrete drying shrinkage (age 28 days)

x: Mixture surface tension

Although the present invention has been described in relation to the test examples as mentioned above, various modifications and variations are possible within the scope without departing from the gist of the present invention, and can be used in various fields. Accordingly, the claims of the present invention include modifications and variations that fall within the true scope of the foregoing invention.

Not applicable

Claims (9)

A method for producing a concrete composition comprising a binder, mixing water, coarse aggregate, fine aggregate and water reducing agent,
In the concrete composition, (a) generating a mixture by stirring a starting material of at least one of polyfunctional alcohol or polyfunctional amine and at least one catalyst of an alkali metal alkoxide or hydroxide; (b) generating a reactant through an epoxide reaction by adding alkylene oxide to the mixture; and (c) adding and stirring a catalyst adsorbent and water to the reactant, followed by filtering to remove the catalyst and impurities; Further comprising an ether polyol for a shrinkage reducer prepared through,
The molecular weight of the polyol is adjusted within the range of 200 to 2,000, and the polyol content is adjusted within the range of 0.5 to 2.0 wt% compared to the binder,
A method for producing a concrete composition with reduced shrinkage, characterized in that for controlling the surface tension of the polyol, mixing water and water reducing agent mixture at 30 to 55 mN / m at 20 ° C.
In paragraph 1,
The polyfunctional alcohol is ethylene glycol, propylene glycol, dipropylene glycol, glycerine, trimethanolpropane, pentaerythritol, dipentaerythritol (Dipentaerythritol), alpha methyl glucoside (α-methylglucoside), xylitol (Xylitol), sorbitol (Sorbitol) and sugar (Sucrose) at least one of,
The multifunctional amine is ortho-toluene diamine (o-toluene diamine), trimethanol amine (Triethanol amine), ethylene diamine (Ethylene diamine), diphenyl methane diamine (Diphenyl methane diamine) and diethylene triamine Shrinkage reduction concrete composition manufacturing method, characterized in that any one or more of.
In paragraph 1,
The alkali metal alkoxide is any one or more of sodium methoxide (CH ₃ ONa) and potassium methoxide (CH ₃ OK),
Shrinkage-reducing concrete composition manufacturing method, characterized in that the hydroxide is at least one of potassium hydroxide (KOH) and sodium hydroxide (NaOH).
In paragraph 1,
Shrinkage-reducing concrete composition manufacturing method, characterized in that the alkylene oxide is at least one of ethylene oxide, propylene oxide and butylene oxide.
In paragraph 1,
The method for producing a concrete composition with reduced shrinkage, characterized in that the catalyst adsorbent is at least one of magnesium silicate and aluminum silicate.
In paragraph 1,
The shrinkage reducing concrete composition manufacturing method, characterized in that the water reducing agent is contained 0.5 to 1.5 wt% compared to the binder.
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