KR102011335B1 - Manufacturing Method of Hybrid Shrinkage Reducing Agent for Dry Mortar - Google Patents

Abstract

The present invention relates to a crack reducing dry mortar and, more specifically, to a method of manufacturing a new organic/inorganic complex shrinkage reducing admixture which has an advantageous effect not only in crack reduction but also in condensation speed and strength enhancement, and to a crack reducing dry mortar composition preferably using the organic/inorganic complex shrinkage reducing admixture manufactured by the method. According to the present invention, the method of manufacturing an organic/inorganic complex shrinkage reducing admixture comprises: a first step of preparing an admixture composition comprising 20 to 30 wt% of a shrinkage reducing agent, 10 to 18 wt% of alkali sulfate, 10 to 20 wt% of anhydrous gypsum, 30 to 55 wt% of spherical granular industrial byproducts with SO_3 content greater than or equal to 20 wt% and free lime (free CaO) equal to or less than 15 wt%, 0.1 to 5.0 wt% of naphthalene-based dispersing agent, and 0.2 to 2.4 wt% of glycerol; a second step of putting materials except glycerol in the prepared admixture composition into a grinder to grind and mix the materials; and a third step of putting glycerol in the middle of grinding and mixing, and grinding and mixing the mixture to manufacture a ground mixture having a maximum particle size equal to or less than 100 μm. According to the present invention, the crack reducing dry mortar composition comprises 1.5 to 3.0 parts by weight of an organic/inorganic complex shrinkage reducing admixture and 150 to 300 parts by weight of a fine aggregate based on 100 parts by weight of a cement binder.

Description

Manufacturing Method of Hybrid Shrinkage Reducing Agent for Dry Mortar

The present invention relates to a crack reducing dry mortar, and more particularly, to a method for preparing a new organic-inorganic composite shrinkage reducing admixture exhibiting a beneficial effect not only in cracking reduction but also in increasing the setting speed and strength, and the organic-inorganic complex shrinkage prepared by the method. The present invention relates to a crack reducing dry mortar composition preferably using a reduced admixture.

Concrete causes cracks for various reasons, and when cracks occur in concrete structures, degradation of durability is promoted, and structural problems such as steel corrosion and freeze-thawing, as well as various problems such as leakage, whitening, and aesthetic degradation, occur. If cracks occur in concrete structures, they are repaired and repaired. In particular, cracks caused by dry contraction after concrete pouring not only incurs the cost of repair work but also indirect losses due to damage of construction company's image and delayed completion of construction review. do. Therefore, when constructing concrete structures, it is necessary to examine various material, construction, and structural measures that can suppress the occurrence of cracks caused by dry shrinkage of concrete.

Previously, the roofless floor of multi-family houses has been built with bare concrete to protect the waterproof layer by using the bucket of the tower crane. This construction method increases the construction cost due to the long duration of the tower crane, and also 15 ~ 18MPa as the bare concrete. Problems such as cracking and surface latencies have been pointed out due to the use of non-structural concrete. There are cases where 21 ~ 24MPa concrete is used to suppress the defect, but the construction cost is not only increased but also it is not a fundamental alternative to the occurrence of cracks.

Recently, in order to solve the problem of increased construction costs due to the use of tower cranes, the construction of dry mortar products after mixing tower cranes is increasing. However, this construction method uses a large amount of mixed water (typically 65-85% based on W / C) for dry mortar products without coarse aggregates for pressure feeding, which is more susceptible to cracking than concrete construction. . In particular, in Korea, the supply and demand of high quality natural aggregates is mainly used low-quality fine aggregates (crushed sand, inland sand, etc.) with high absorption rate, the use of such aggregates serves as a cause of the use of a large amount of mixed water.

In order to improve the quality of dry mortar products, there is a plan to increase the amount of binder and to use high-quality aggregates, but the increase in the amount of binder leads to an increase in the cost of manufacturing the dry mortar and, in general, the amount of dry shrinkage when the binder is increased. There is a limit to alternative crack reduction as it increases, the use of high-quality aggregate is already a problem due to the supply and demand imbalance of the aggregate can not be a realistic alternative. Considering this industrial environment, there is a need for a new dry mortar product technology capable of suppressing cracking caused by plastic shrinkage and dry shrinkage while using a large amount of mixed water.

Meanwhile, expansion agents have been introduced as a way to reduce the dry shrinkage of mortar. However, swelling agents cause volume expansion through hydration, which is usually very expensive and constrains their use in economical product manufacturing. In addition, when the expansion agent uses a large amount of mixed water, such as a roof mortar, the effect is insignificant.However, when a large amount of expansion agent is used in the roof mortar, the expansion structure is excessively expanded due to the repeated repetition of water due to rain or the like. It is not suitable because it may be destroyed.

Another method for reducing the dry shrinkage of mortars is introduced. Shrinkage reducing agents reduce shrinkage in a way that mitigates the capillary tension generated by evaporation of water in the pores of 2.5-50 nm concrete or mortar, which have the greatest effect on plastic shrinkage and dry shrinkage. The most commonly used shrinkage reducing agent can be expressed as follows, mainly glycol ether blend.

R O (AO) n R

Where A: alkalene polymer

R: hydrogen, hydroxyl, alkyl, phenyl, cycloalkyl groups

Shrinkage reducing agents as described above can reduce the plastic shrinkage and drying shrinkage and increase the permeability resistance and long-term durability, but it is pointed out that the delay in setting time and the reduction in strength expression. Therefore, when the existing shrinkage reducing agent is used for the roof mortar, the construction time may increase due to the delay of the condensation time, thereby increasing the construction cost. In addition, most shrinkage reducing agents are in the form of liquids and are difficult to utilize in the manufacture of dry mortar products.

KR 1020050105641 A KR 1020160018442 A

The present invention has been developed to improve the quality of the conventional dry mortar product, there is a technical problem to provide a new dry mortar product that can be advantageously used as a roof protection mortar by reducing cracks, shortening the setting time, increase the strength. .

In addition, the present invention is a shrinkage reducing admixture for preferably used in dry mortar products, while having a solid form that can be properly mixed and dispersed in dry mortar products while economically utilizing the existing shrinkage reducing agent, and prevents the delay of condensation and strength loss. It is intended to provide a method for producing a new organic-inorganic composite shrinkage reducing admixture that can also be expressed.

In order to solve the above technical problem, the present invention, with respect to 100 parts by weight of cement binders, organic-inorganic composite shrinkage reducing admixtures 1.5 to 3.0 parts by weight, cracked dry mortar, characterized in that the composition is composed of 150 to 300 parts by weight To provide a composition.

In addition, the present invention is 20 to 30% by weight of shrinkage reducing agent, 10 to 18% by weight of alkali sulfate, 10 to 20% by weight of anhydrous gypsum, SO ₃ content of more than 20% by weight of spherical free lime (free CaO) 15% by weight or less A first step of preparing a admixture composition comprising 30 to 55% by weight of a granular industrial by-product, 0.1 to 5.0% by weight of a naphthalene-based dispersant, and 0.2 to 2.4% by weight of glycerol; A second step of pulverizing and mixing a material other than glycerol in the prepared admixture composition into a grinder; It provides a method for producing an organic-inorganic composite shrinkage reducing admixture, characterized in that it comprises a; the third step of preparing a pulverized mixture having a maximum particle size of less than 100㎛ by adding glycerol in the middle of the pulverized mixing.

According to the present invention, the following effects can be expected.

First, it is possible to provide a new organic-inorganic composite shrinkage reducing admixture that can be economically utilizing the existing shrinkage reducing agent while being properly mixed and dispersed in a dry mortar product. In particular, the shrinkage reducing admixture of the present invention can be advantageously used for the roof mortar because it exhibits a shortening of the condensation time, the strength enhancing effect compared to the conventional shrinkage reducing agent.

Second, the dry mortar product incorporating the new organic-inorganic composite shrinkage reducing admixture can not only reduce the cracks due to shrinkage reduction, but also shorten the setting time and increase the strength, and even more than a certain amount even when the amount of mixed water is reduced. Since performance is expressed, when applied as a roof mortar, it is possible to reduce construction costs while ensuring construction and durability at the same time.

1 and 2 is a view showing a mock-up test example, respectively showing the formwork plan and the length change measurement plan.
3A to 3C are diagrams showing the results of evaluation of the crack shape of the test specimen in the Mock-Up test example, and immediately after the casting, the first and the 21st evaluation results are respectively shown.
4 is a schematic diagram of the crack shape of the test specimen in the mock-up test example and a crack length measurement result table.
Figure 5 is a graph of the measurement results for the crack length and crack width of the test specimen in the mock-up test example.
Figure 6 is a graph showing the measurement results of the length change in the Mock-Up test example.

The present invention relates to a method for producing a novel shrinkage reducing admixture and to a crack reducing dry mortar composition preferably using the shrinkage reducing admixture.

Shrinkage reducing admixture according to the present invention is a conventional shrinkage reducing agent and industrial by-products such as alkali sulfate, anhydrous gypsum, fly ash, dispersant, glycerol, etc. to be easily incorporated into dry mortar products while supplementing the disadvantages of the existing shrinkage reducing agent Grinding and mixing together is characterized by the production of shrinkage mixed with a mixed organic and inorganic.

Specifically, the organic-inorganic composite shrinkage reducing admixture includes 20 to 30% by weight of shrinkage reducing agent, 10 to 18% by weight of alkali sulfate, 10 to 20% by weight of anhydrous gypsum, and a SO ₃ content of 20% or more by free lime (Free CaO). A first step of preparing a admixture composition comprising 30 to 55% by weight of a spherical granular industrial by-product having a content of 15% by weight or less, 0.1 to 5.0% by weight of a naphthalene-based dispersant, and 0.2 to 2.4% by weight of glycerol; A second step of pulverizing and mixing a material other than glycerol in the prepared admixture composition into a grinder; Characterized in that the manufacturing process comprising; a third step of adding a glycerol in the middle of the grinding and mixing and grinding and mixing to prepare a grinding mixture with a maximum particle size of 100㎛ or less.

The first step is the raw material preparation weighing step, the raw material is prepared shrinkage reducing agent, alkali sulfate, anhydrous gypsum, industrial by-products, dispersants, glycerol.

Shrinkage reducing agent is a basic material for shrinkage reduction. It uses existing shrinkage reducing agent that acts to reduce the shrinkage phenomenon by relieving capillary tension caused by evaporation of water in the concrete of 2.5 ~ 50nm size or mortar. Just do it. Preferably, at least one selected from propylene glycol, polyoxyalkylene alkyl esters, and pentyl glycol, and it is suitable to use in a flake solid state. Shrinkage reducing agent is used 20 to 30% by weight, if less than 20% by weight shrinkage effect is insignificant, if it exceeds 30% by weight is concerned about economic loss and strength degradation.

Alkali sulphate serves to compensate the initial strength reduction and prevent the coagulation delay by shrinkage reducing agent by promoting the hydration of cement by alkali to promote the reaction of Al2O3-SiO2 or CaO-Al2O3-SiO2 binder. In addition, the formation of a large amount of expandable ettringite by the SO ₃ component has an effect of improving strength and reducing shrinkage. Alkaline sulfate is suitable to select one or more of Na ₂ SO ₄ , K ₂ SO ₄ , 10 to 18% by weight is used. If it is less than 10% by weight, the effect of compensating for strength degradation and preventing condensation delay is insignificant, and if it is more than 18% by weight, economic loss and long-term strength loss are feared.

Anhydrous gypsum, like alkaline sulphate, contributes to strength improvement and shrinkage reduction by generating a large amount of expandable ettringite by SO ₃ component. Anhydrous gypsum can be properly reacted at the initial stage when the powder is high, so it is preferable to use a powder of 5500 ~ 7500 cm 2 / g in consideration of economical efficiency. Anhydrous gypsum is used in an amount of 10 to 20% by weight. If it is less than 10% by weight, the effect of producing an expandable hydrate and initial strength is insignificant.

Industrial by-products are spherical granular materials with more than 20 wt% of SO ₃ and less than 15 wt% of free CaO. Since they have spherical grains, they contribute to efficient dispersion and mixing of shrinkage reducing agents and anhydrous gypsum during grinding mixing. do. In the absence of spherical granular industrial by-products, the organic-inorganic mixture may not aggregate and disperse during pulverization mixing. In addition, industrial by-products contain SO ₃ , which contributes to the formation of ettringite. Industrial by-products should have free CaO of 15% by weight or less. If there is a large amount of free lime, the bulky hydrate reacts immediately with water, creating a large amount of 2.5-50 nm voids, which tend to cause dry shrinkage. Because it is crazy. As an industrial by-product, fly ash is preferably used, and 30 to 55% by weight is used. If it is less than 30% by weight does not have a positive effect on the efficient dispersion mixing of shrinkage reducing agent and anhydrous gypsum, if it exceeds 55% by weight, the content of shrinkage reducing agent, alkali sulfate, anhydrous gypsum and the like decreases relatively.

The dispersant is a material that contributes to securing proper workability and reducing the amount of mixing. The naphthalene system is used and 0.1 to 5.0% by weight is used in consideration of the dispersing effect and economic efficiency.

Glycerol has a chemical formula of C ₃ H ₅ (OH) ₃ and a molecular weight of 92.09382 g / mol, which is effective in preventing aggregation of contents during grinding mixing, and also prevents rapid evaporation of moisture, thereby exerting a secondary effect of shrinkage reduction. Glycerol is used in the 0.2 ~ 2.4% by weight, but less than 0.2% by weight of the anti-aggregation effect is insignificant, if the content exceeds 2.4% by weight of the anti-aggregation adverse effect.

The second step is to grind and mix the raw materials prepared as above. All raw materials except glycerol are added to a grinder and mixed. The pulverizer may use a vibration mill, a ball mill, a cross beater mill, and the like, and the vibration mill or the ball mill have a natural drying effect due to frictional heat generated during grinding. Agglomeration may occur in the pulverization mixing process by the pulverizer. In the present invention, the coagulation phenomena is suppressed by injecting glycerol in the middle of pulverization while utilizing industrial granular products of spherical shape.

The third step is to add glycerol in the middle of the grinding and to continue the grinding mixing. Glycerol should be added in the middle of grinding to prevent flocculation.

As a result, a pulverized mixture is produced and produced, and the pulverized mixture soon becomes an organic-inorganic composite shrinkage reducing admixture. However, the pulverized mixture produced has a maximum particle size of 100 μm or less and an average particle size of 7-50 μm. If the average particle size is small, the manufacturing cost increases. If the average particle size is large, the dispersion effect of raw materials is insignificant. In addition, the grinding mixture is preferably produced with a moisture content of 0.7% or less. If the moisture content is high, aggregation may occur during storage.

The organic-inorganic composite shrinkage reducing admixture produced as described above can be commercialized as a dry mortar for roofing mortar. Dry mortar is suitable to include 1.5 to 3.0 parts by weight of organic-inorganic composite shrinkage reducing admixtures, and 150 to 300 parts by weight of fine aggregates, based on 100 parts by weight of cement binder.

In dry mortar, the cement binder is usually composed of 75-100% by weight of Portland cement, 0-25% by weight of Al2O3-SiO2 or CaO-Al2O3-SiO2-based binder, more preferably 75-95% by weight of Portland cement. %, Al 2 O 3 -SiO 2 or CaO-Al 2 O 3 -SiO 2 -based binder 5 to 25% by weight. In general, when Portland cement is less than 75% by weight, there is a problem in strength expression, and when the Al2O3-SiO2 or CaO-Al2O3-SiO2 based binder is more than 25% by weight, there is a concern that the strength is lowered, the plastic shrinkage and the dry shrinkage increase. Al 2 O 3 -SiO 2 -based or CaO-Al 2 O 3 -SiO 2 -based binders include fly ash, blast furnace slag powder, and the like. In the embodiment of the present invention, fly ash is used.

The organic-inorganic composite shrinkage reducing admixture is used 1.5 to 3.0 parts by weight with respect to 100 parts by weight of cement binder, if less than 1.5 parts by weight shrinkage effect is insignificant, if more than 3.0 parts by weight of the initial strength is feared.

The fine aggregate is used in an amount of 150 to 300 parts by weight based on 100 parts by weight of the cement binder. If it is less than 150 parts by weight, the economical efficiency is lost, and the strength is lowered and the durability is lowered while it is over 300 parts by weight. Residual aggregate is less than 10% water absorption and granulation rate of 2.1 to 4.5 is used, but a high absorption rate requires a large amount of mixed water, the strength is lowered. Larger aggregates have a negative impact on workability and pump pressure.

Hereinafter, the present invention will be described in detail with reference to Preparation Examples and Test Examples. However, the following Preparation Examples and Test Examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Preparation Example Preparation of Organic-Inorganic Composite Shrinkage Reduction Admixture

(1) preparation of raw materials

As raw materials, shrinkage reducing agents, alkali sulfates, anhydrous gypsum, industrial by-products, naphthalene-based dispersants, and glycerol were prepared. The shrinkage reducing agent is a solid pentyl glycol on flake, having a purity of 99.2%, an acidit max of 0.01, an aldehyde max of 0.05, a molecular weight of 104.15, and a specific gravity of 1.06. will be. Alkali sulfate is Na ₂ SO ₄ containing not less than 99% pure water and 0.2 wt% or less of water, and anhydrous gypsum has a powder density of 6320 cm 2 / g and a density of 2.91. Industrial by-products are fly ash consisting of 34.8 wt% CaO, 21.5 wt% SO3, 15.2 wt% SiO2, 13.7 wt% Fe2O3, 7.34 wt% Al2O3, 5.02 wt% MgO, and 4.8 wt% free lime. .

(2) Improving raw materials and adding hoppers

The raw materials were improved by the composition of 25 weight% shrinkage reducing agent, 14 weight% of alkali sulfate, 11 weight% of anhydrous gypsum, 49 weight% of industrial by-products, 0.5 weight% of naphthalene type dispersing agents, and 0.5 weight% of glycerol, and it put into the hopper.

(3) grinding machine

Glycerol was removed from the improved raw materials, and then pulverized and mixed into a grinder. The grinding machine used a vibration mill with a grinding capacity of 1.8kg / 13min, a grinding capacity of 3 to 4kg / pot × 2pot, and a grinding medium of steel bar (Vol 50%).

(4) glycerol input

Glycerol was added during grinding mixing.

(5) obtaining crushed products

The pulverized mixing was finished and the pulverized product was obtained. The pulverized product showed a maximum particle size of 93 μm, an average particle size of 23 μm, and a water content of 5.6%. Such a pulverized product immediately became an organic-inorganic composite shrinkage reducing admixture according to the present invention.

Test Example 1 Mortar Performance

1. Mortar formulation

Dry mortar was formed as shown in Table 1 below, and water was mixed with the prepared dry mortar.

Mortar combination (part by weight) division Comparative Example 1 Comparative Example 2 Example 1 Comparative Example 3 Comparative Example 4 Example 2 Binder 100 100 100 100 100 100 Shrinkage reduction admixture - 0.65 2.0 - 0.65 2.0 aggregate 257 257 257 257 257 257 Material cost
(Water cement ratio) 19%
(67.8%) 19%
(67.8%) 19%
(67.8%) 22%
(78.5%) 22%
(78.5%) 22%
(78.5%)

In the formulation of Table 1 above, the binders were 80% by weight of Portland cement (specific gravity 3.15, 3480 cm 2 / g powder) and 20% by weight fly ash (specific gravity 2.22, 3519 cm 2 / g powder). In the case of the comparative example, the shrinkage reducing admixture is a glycol-based shrinkage reducing agent, and in the case of the example, the organic-inorganic composite shrinkage reducing admixture prepared in [Production Example]. Aggregate is a standard yarn mixed with natural aggregate and crushed sand at 3: 7, with an assembly rate of 3.48 and a density of 2.54.

2. Mortar Performance

Condensation time, flow, compressive strength, and the rate of change of length were measured for the mortar blended with the composition as shown in [Table 1], and the measurement results are shown in the following [Table 2].

Mortar performance division Comparative Example 1 Comparative Example 2 Example 1 Comparative Example 3 Comparative Example 4 Example 2 Condensation time (second, minute) 390 460 405 495 575 520 Flow (mm) 240
(When hit 16 times) 240
(6 hits) 240
(6 hits) 250
(15 hits) 230
(5 hits) 230
(5 hits) 4-day compressive strength (MPa) 15.0 13.6 16.4 10.5 9.3 12.3 7 Day Compressive Strength (MPa) 16.2 16.0 18.5 11.5 11.4 14.2 28 Day Compressive Strength (MPa) 25.4 22.5 25.8 18.6 16.8 19.7 Change of length
(28 days, × 10 ^-6 )
(Measurement of length change by embedded gauge) -793 -562 -543 -868 -626 -607

As shown in Table 2, Comparative Example 2 and Comparative Example 4, in which the existing glycol-based shrinkage reducing agent was mixed, showed a change in length but a large delay in condensation and a large decrease in strength. On the other hand, Examples 1 and 2 incorporating the organic-inorganic composite shrinkage reducing admixture according to the present invention was not only more effective in reducing the length change, but also significantly reduced the setting delay, the strength performance was shown to be improved. These results are maintained even if the mixed water increases according to the construction conditions of the site as in Example 1, 2, it will be possible to bring excellent crack reduction effect in the future construction site.

Test Example 2 Mock-Up Test

1. Mortar formulation

Dry mortar was prepared for the mock-up test as shown in Table 3 below, and water was mixed with the prepared dry mortar. In the formulation of Table 3 above, the binder is 80% by weight of Portland cement (specific gravity 3.15, 3480 cm 2 / g powder) and 20% by weight fly ash (specifically 2.22, 3519 cm 2 / g powder). As for the shrinkage reduction mixed material, the organic-inorganic composite shrinkage reduced admixture manufactured in [Manufacture Example] was mixed only in the Example. Aggregate is a standard yarn mixed with natural aggregate and crushed sand at 3: 7, with an assembly rate of 3.48 and a density of 2.54.

Mortar combination (part by weight) division Plain Plain-mesh SR3 SR3-Mesh Binder 100 100 100 100 Shrinkage reduction admixture - - 2.0 2.0 aggregate 215 215 215 215 Material cost
(Water cement ratio) 20%
(63%) 20%
(63%) 20%
(63%) 20%
(63%)

The performance of the mortar blended as shown in [Table 3] was shown as [Table 4] below as a result of the measurement. It is confirmed that the final setting time is shortened by the incorporation of the shrinkage reducing admixture according to the present invention, and the compressive strength is improved.

Mortar performance division Plain, Plain-Mesh SR3, SR3-Mesh Condensation time (second, minute) 300 330 Last minute closed 240 210 Flow (mm) 180
(Measured without strike) 180
(Measured without strike) Air volume (%) 4.2 4.5 Unit volume mass 2.060kg / m3 2.050kg / m3 4-day compressive strength (MPa) 11.18 15.05 7 Day Compressive Strength (MPa) 13.31 17.06

2. Mock-UP test

Mock-UP test was carried out by pouring mortar blended as shown in [Table 3] in the formwork prepared as shown in Figure 1, was carried out separately according to the wire mesh installation. Plain and SR3 do not have wire mesh installed. Plain-Mesh and SR3-Mesh have wire mesh installed. In the mock-up test, the length change was measured according to the plan as shown in FIG. 2, and the crack shape of the test specimen was checked over time, and the crack length and the crack width were measured. The crack shape is the same as in Figures 3a to 3c, the crack length and crack width measurement results are as shown in [Table 5] and Figures 4 to 5, the length change measurement results are shown in FIG.

Crack width measurement result division Day 6 (mm) Day 14 (mm) Day 21 (mm) Day 28 (mm) Plain One 0.60 1.00 1.00 1.00 2 0.40 0.40 0.40 0.40 3 1.10 1.20 1.30 1.40 4 0.45 0.85 0.90 0.90 Average 0.64 0.86 0.90 0.93 Plain-mesh One 0.45 0.75 0.80 0.80 2 1.00 1.30 1.40 1.40 3 1.00 1.20 1.40 1.40 4 0.50 0.80 0.80 0.80 Average 0.74 1.01 1.10 1.10 SR3 One 0.06 0.15 0.15 0.15 2 0.35 0.55 0.60 0.60 3 0.35 0.40 0.40 0.40 4 0.08 0.10 0.10 0.15 Average 0.21 0.30 0.31 0.32 SR3-Mesh One - - - - 2 - - - - 3 - - - - 4 - - - - Average - - - -

As shown in the above [Table 5] and Figures 3a to 6, in the case of Plain, regardless of the presence of the wire mesh, the rapid shrinkage action occurs from the initial firing time of curing, the firing and dry shrinkage cracks were visually confirmed. In the test body (SR, SR3-Mesh) mixed with the organic-inorganic composite shrinkage reducing admixture according to the invention, it was confirmed that the result of controlling the plastic shrinkage crack with slight expansion behavior occurred at the initial firing time regardless of the presence or absence of wire mesh. . In addition, it was confirmed that a gentle amount of dry shrinkage occurred compared to the plain test specimen from the age of 4 days when the dry shrinkage action occurs in earnest.

On the other hand, in the case of Plain-Mesh, the initial curing shrinkage was smaller than that of plain, which is judged to be the result of the wire mesh restraining the initial plastic shrinkage. In SR3-Mesh, the initial expansion occurred less than SR3 due to the restraint effect of the wire mesh. In addition, as a result of comparing the total dry shrinkage at 28 days of mock-up test with or without wire mesh, SR3 showed about 75% reduction in shrinkage compared to plain, and SR3-Mesh was about compared to plain mesh. The shrinkage amount of 73% was reduced, and the shrinkage cracking performance of the dry mortar containing the organic-inorganic composite shrinkage reducing admixture was excellent. However, between 21 and 22 days of age, it is confirmed that the period of dry shrinkage is mitigated, which is the result of temporary relief of dry shrinkage due to water supply from rainfall.

Claims (4)

delete Shrinkage reducing agent 20-30% by weight, alkali sulfate 10-18% by weight, anhydrous gypsum 10-20% by weight, SO ₃ content of 20% by weight or more, spherical granular industrial by-products having 15% by weight or less free lime A first step of preparing a admixture composition comprising 30 to 55% by weight, 0.1 to 5.0% by weight of a naphthalene-based dispersant, and 0.2 to 2.4% by weight of glycerol;
A second step of pulverizing and mixing a material other than glycerol in the prepared admixture composition into a grinder;
Including a glycerol in the middle of the grinding and mixing, the third step of preparing a grinding mixture with a maximum particle size of 100㎛ or less by grinding and mixing;
The first step is made by selecting a pentyl glycol (Pentyl Glycol) as a shrinkage reducing agent, select Na ₂ SO ₄ as alkali sulfate, and select a powder of 5500 ~ 7500 cm 2 / g with anhydrous gypsum,
The second step is a method for producing an organic-inorganic composite shrinkage reducing admixture, characterized in that made using a vibrating mill or ball mill as a grinder. delete delete

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