KR101285699B1 - Method of quick lime and Crack inhibitor using the same - Google Patents

Abstract

The present invention is prepared by (1) calcined limestone gemstones at 1200 to 1300 ℃ 24 to 30 hours, (2) calcium oxide (CaO) content in quantitative analysis (XRD) of 82% or more, loss of ignition (lg-loss ) is 5% or less, (3) digestion test (hydration reaction heat) the maximum exothermic temperature (Tmax) is 45 ℃ or less, the maximum temperature reaching time (Tmax time) at the time is to be 30 minutes or more, and (4) particle size distribution The present invention relates to a method for producing undercalcined lime having a particle size range of 90 to 100%, 100 to 170 mesh, 60 to 70%, and 325 mesh to 40%, and a crack preventing agent using the same.

Description

Method for preparing undercalcined lime and a crack inhibitor using the same {Method of quick lime and Crack inhibitor using the same}

The present invention relates to a method for producing undercalcined lime which is one of the components of cement mortar for preventing cracking of buildings and a crack preventing agent using the same.

Drying of Ondol Floors of Apartment Houses Various methods for reducing cracks are being applied in the construction of cement mortar. Among them, physical methods of mixing wire mesh, metal lath, and fiber reinforcement are used. It has been pointed out that the crack prevention effect by the dry shrinkage of cement mortar is insignificant and that the construction of the cement mortar cannot be performed quickly by one additional process. In addition, there are patents and products related to various crack preventing materials and shrinkage reducing materials as chemical additives to reduce cracks, but most of them do not understand the condensation characteristics of dry cement mortar, so the reaction of crack preventive materials is too fast or too fast compared to dry cement mortar. As it reacts late, it does not play a role at the time of reducing or compensating shrinkage, so the crack reduction performance against plastic shrinkage or dry shrinkage is insignificant. Most of the crack preventive materials invented and designed include ordinary quicklime and underlime lime as main binders. However, in reality, there is no specialized manufacturing technology for the detailed composition for reducing the cracking and understanding of plasticity and dry shrinkage of cement. In the case of most of the prior patents, the technology mainly manufactures by additionally mixing other bitumen, anhydrous gypsum, and fly ash or magnesia waste refractories in addition to general quicklime and undermineralized lime. In the sector, it is difficult to apply in the actual industrial sector.

Republic of Korea Patent No. 10-0544062 "Crack preventer composition / silk rod for cement mortar (2006)" is a calcined lime obtained by calcining limestone ore at a temperature of 950 ℃ to 1100 ℃ for 50 to 60 hours, As it is rather low, the overall plasticity is not high, and it causes a decrease in production according to the long time of firing time, and also by mixing the fly ash with anhydrous gypsum produced during the hydrofluoric acid manufacturing process at a certain ratio. Secondary mixing of raw materials causes excessive process costs, which is why it is not applied in an effective way.

Republic of Korea Patent No. 10-0473507 and "Cement expansion material / silk rod (2005)" 13 to 71% by weight of industrial quicklime, calcium ash content of more than 90% by weight, fly ash 4 to 71% by weight, and sulfur trioxide (SO3) content Patent for the composition of the expansion material for cement consisting of 12 to 43% by weight of flue gas desulfurization, which is 40 to 55% by weight and dehydrated. It is not being applied in a way.

Republic of Korea Patent Registration No. 10-0515090 "cement expansion material composition using magnesia waste refractories derived from steel mill furnaces" is a cement expansion material composed of about 75 to 8wt% magnesia waste refractory and 15 to 25wt% of a small amount of underlime lime Due to the nature of the by-products, the quality deviation of magnesia waste refractories is not consistently applied, and additional process costs are generated by mixing two raw materials at a constant ratio, and thus they are not applied in an effective manner.

In the case of conventional cement mortar, cement and sand were supplied separately from the site, and site casting was performed by hand beam or by machine beam using a small mixer for each part. The mechanized construction of dry cement mortar is being done rapidly. Mechanized construction is a method in which dry cement mortar manufactured in a factory is mixed, conveyed, and poured in a continuous manner on site to finish a large area in a short time. It is one of the public methods that I receive.

On the other side of this advantage, however, there is a problem that causes quality deterioration due to rapid construction, mass casting, etc. Among them, the plastic shrinkage cracks occurring early (especially within 24 hours after casting) and long-term related to durability Dry shrinkage cracks that occur throughout the country are pointed out as the biggest problem. Particularly in the case of plastic shrinkage cracking, the amount of dough is placed very high in order to facilitate the mechanized construction of dry cement mortar, which appears to be 3 to 4 hours later than the general cement mortar. Contraction is even greater. This plastic shrinkage crack occupies more than 80% of the shrinkage occurring in the whole life, and how it corresponds to the initial plastic shrinkage has a great influence on the dry shrinkage that appears after curing.

This cracking problem of dry cement mortar causes secondary defects such as cracking, breakage and degradation of durability, and deformation and discoloration of the surface finish material at the cracked area. The tenants are directly or indirectly distrusting the entire construction industry.

The present invention is to solve the above problems, the present invention is produced by calcining limestone ore at 1200 to 1300 ℃ 24 to 30 hours, calcium oxide (CaO) content of 82% or more, loss of ignition (lg-loss ) 5% or less, the maximum heat generation temperature (Tmax) should be 45 ℃ or less, the maximum temperature reaching time (Tmax time) should be 30 minutes or more, and the particle size distribution is 90 to 100% for 100Mesh passage and 60 to 70 for 170mesh passage. It is a problem solving means to achieve the present invention to provide a method for producing under-lime lime having a particle size range of 40 to 50% and a crack preventing agent using the same.

Undercalcined lime of the present invention is used to add 2 to 10wt% of the cement weight ratio of dry cement mortar product alone without mixing with other anhydrous gypsum and filler, in this case to compensate for the initial firing shrinkage and dry shrinkage of the dry cement mortar By transferring the maximum expansion force to the dry cement mortar without losing the expansion force of the expansion material, the amount of cracking after construction is significantly reduced, and unlike the existing patent, there is no secondary mixing process that occurs additionally due to the use of undersized lime alone. Indicates that there is.

1 digestion test process of the present invention.
2 is a diagram of digestive digestibility according to the degree of plasticity of the present invention
Figure 3 Detailed measurement of the expansion and contraction reaction of the present invention
Figure 4 crack inhibitor expansion performance test chart mixed with underlime lime of Example 1 of the present invention
5 is a crack inhibitor expansion performance test chart mixed with underlime lime of Example 2 of the present invention
Figure 6 crack inhibitor expansion performance test chart mixed with underlime lime of Example 3 of the present invention
7 is a crack inhibitor expansion performance test chart mixed with underlime lime of Example 4 of the present invention
8 is a crack inhibiting agent expansion performance test chart mixed with underlime lime of Example 5 of the present invention
9 to 11 crack prevention site construction photos of the present invention

The present invention is prepared by calcining limestone ore at 1200 to 1300 ℃ 24 to 30 hours, calcium oxide (CaO) content of 82% or more, lg-loss 5% or less, the maximum heating temperature (Tmax) is 45 ℃ or less, the maximum temperature reaching time (Tmax time) should be 30 minutes or more, and the particle size distribution has a particle size range of 90 to 100% for 100Mesh passage, 60 to 70% for 170mesh passage, and 40 to 50% for 325mesh passage. The present invention relates to a method for producing an undersized lime having an undercut and a crack preventing agent using the same.

Quicklime theoretically requires a heat of 422 kcal / kgCaCO3, and is prepared by pyrolysis of calcium carbonate (CaCO3), which is the main component of limestone, into calcium oxide (CaO) and carbon dioxide (CO2) at a temperature of about 900 ° C.

Limestone Decomposition -Decomposition of limestone (CaCO3)
CaCO3 → CaO + CO2 ‥‥‥ (1) (900 ~ 1000 ℃)

-Decomposition of Dolomite CaCO 3 · MgCO 3)
CaCO3, MgCO3 → CaCO3, MgO + CO2 ‥‥‥ (2) (760 ~ 800 ℃)
CaCO3MgO → CaOMgO + CO2 ‥‥‥ (3) (850 ~ 900 ℃)

-Decomposition of Magnesite (MgCO3)
MgCO3 → Mg + CO2 ‥‥‥ (4) 550 ~ 600 ℃

The theoretical method of manufacturing quicklime described above requires more heat due to various variables such as heat loss of the kiln or impurities content of raw materials during production for industrial use, and in general, the temperature of about 1000 to 1100 ° C in quicklime processors Quicklime is manufactured in the range. In this case, the produced quicklime is characterized by fine crystals of calcium oxide (CaO), large specific surface area, large porosity, small volume specific gravity, and high reactivity.

In the case of ordinary quicklime, it is characterized by the rapid reaction within a few seconds to several minutes from the initial contact with water in the reactive section, and the immediate termination of the quicklime reacts with water if the firing time at a higher temperature is longer. The content of calcium oxide (CaO) can be increased, but the reactivity and reaction time are rather delayed.

In the quicklime manufacturing plant, the degree of calcination can be judged by lgloss, and in general quicklime products, it is about 10 to 15%, and in this case, the quicklime composition has a calcium oxide (CaO) content of about 70 to 75 %, Uncalcined calcium carbonate (CaCO3) content is about 15 to 20%, and other impurities (MgO, SiO2) content is about 5 to 10%. Such quicklime undergoes a rapid hydration expansion reaction in the initial 5 to 15 minutes when reacted with water, and the reaction is terminated immediately thereafter. Since this is done in a shorter time than the time required for mechanized construction of dry cement mortar, the effect on the expansion force after the drying cement mortar is insignificant.

However, when calcining quicklime by maintaining the heating temperature and the settling time higher than the firing temperature of the products generally produced, the degree of calcining becomes high, and the loss of ignition (lgloss) of about 3 to 6% can be produced. have. In this case, the composition of the underlime lime has a calcium oxide (CaO) content of about 80 to 85%, an uncalcined calcium carbonate (CaCO3) content of about 10 to 15%, and other impurities (MgO, SiO2) content of about 5 to About 10%. When the undercalcite reacts with water, the hydration product of calcium oxide (CaO), which is an increased hydration expansion composition than ordinary quicklime, is developed at the initial plastic shrinkage time that occurs after the mechanized construction of dry cement mortar. Ca (OH) 2) gives a suitable expansion force according to the formation and crystal growth reaction, and the dry shrinkage that occurs in long-term aging after 30 days of age is the hydration product of magnesium oxide (MgO) produced by the decarbonation of dolomite Dry shrinkage of cement was compensated for the production of phosphorus (Mg (OH) 2) and the crystal growth reaction.

In the present invention, as described above, by appropriately adjusting the expansion composition and the reaction time of the hydration expansion reaction of the quicklime, which is changed due to the significant increase in the firing temperature than the manufacture of the quicklime, a crack prevention material suitable for dry cement mortar was developed. As it is transferred to a cement factory within a short time after firing and crushing in a production plant, it is stored in a silo to secure product stability against weathering for atmospheric moisture, which is the biggest disadvantage of quicklime products. In addition, it has developed the ideal crack prevention material of dry cement mortar by giving the same or more expansion force with the addition amount lower than the expansion agent.

In the present invention, the calcination of general quicklime for steelmaking, which accounts for most shipments from quicklime companies, increases the ignition loss (lg-loss) of 5% or less, calcium oxide (CaO) content of 82% or higher, and unfired carbonic acid. It is composed of under-lime lime composition with calcium (CaCO3) content of less than 8% and other impurities (MgO, SiO2) content of about 5 to 10%.

The evaluation method for the degree of plasticity (degree) of undercalcined lime should be carried out according to the [digestion test method] of FIG. 1 below, and the measuring method is 400 ± 50rpm stirrer with 400g of water and 100g of quicklime at 25 ° C water temperature. After mixing for 30 seconds, the water temperature in the upper 2cm range of the mixed slurry is evaluated by measuring. Through extinguishing reactivity test to measure exothermic temperature and time, the maximum reaction temperature (Tmax) should be below 45 ℃ and the time to reach maximum reaction temperature (TmaxT) should be more than 30 minutes.

In addition, in the present invention, the manufactured undercalcin is used as a crack prevention material for dry cement mortar as a powder form product, and 100% mesh passes 80% to 100%, 170mesh passes 60% to 80%, and 325mesh passes 40% to 60 It has a particle size distribution in the range of%, and is used alone in the dry cement mortar blending without any other additives, and the amount thereof is adjusted in the range of 2 to 10% of the cement weight ratio.

In the case of general quicklime, the decarbonate reaction proceeds only on the outer surface in the appropriate temperature range, and a small amount of externally activated calcium oxide (Ca) undergoes a rapid reaction when reacted with water, and thereafter, an unbaked calcium carbonate ( CaCO3) does not react, so in the digestibility test, the maximum exothermic temperature (Tmax) reacts abruptly at 45 to 50 ° C., but the reaction occurs rapidly after the maximum exothermic temperature reaching time (TmaxT) is about 10 to 15 minutes. Is terminated. Considering that the first-generation casting time of the dry cement mortar of MDU is about 10 to 15 minutes, the reaction peaks in the pumped hose, and the reaction ends within the actual household after that.

However, the demineralized lime of the present invention has a decarbonation reaction proceeding to the inside by increasing the sintering temperature, and at this time, the voids generated by the external CO2 are not activated and are densified again, and the decarburization reaction proceeds to the inside. The content of calcium (CaO) is produced in a larger amount than normal quicklime. The tissue and composition of the underlime quicklime, as shown in Figure 3 below, does not cause a sudden reaction when the high CaO component is in contact with water, but gradually reacts with water to continuously produce Ca (OH) 2 as a hydrated crystal. Done. In this case, in the digestibility test, the maximum fever temperature (Tmax) is 45 ° C. or less, and the maximum fever temperature attainment time (TmaxT) appears at about 30 to 35 minutes. Considering that the first-generation casting time of the dry cement mortar of apartment houses is about 10 to 15 minutes, it is stable to reduce the initial plastic shrinkage cracking occurring at the time of casting and early curing, since the reaction starts sufficiently within the household after the hose movement. It can secure the cracks and significantly reduce the incidence of cracking in the initial plastic shrinkage of dry cement mortar. Dry shrinkage that occurs in long-term aging after 30 days of age is largely caused by increasing the degree of sintering as dolomite (CaCO _{3 and} MgCO ₃ ) is made of magnesium oxide (MgO) at 800 ° C to increase the plasticity. Dry shrinkage of cement was compensated for by the formation of hydration product (Mg (OH) 2) by magnesium oxide (MgO) and the crystal growth reaction.

Limestone Decomposition -Hydration expansion reaction of calcium oxide (CaO)
CaO + H2O = Ca (OH) 2 .......... (5)

-Hydration expansion reaction of dolomite (MgO)
MgO + H2O = Mg (OH) 2 .......... (5)

General quicklime burns limestone with anthracite coal at about 1000 ~ 1100 ℃ in a vertical large furnace, but the higher temperature is 1,200 for firing underlime lime as crack prevention material of dry cement mortar in the present invention. When calcined at 1300 ° C., the decomposition reaction of quicklime proceeds further to the inside to increase calcium oxide (CaO) content, and higher heat is applied thereto to cause melting of the pores in which carbon dioxide (CO2) falls off and melting. Done. The calcined calcined lime at such a high temperature is suitable for application as a crack prevention material of dry cement mortar because it reacts more slowly when reacted with water, unlike conventionally manufactured quicklime.

However, as the calcination rate of the quicklime is reduced as the cracking material of the dried cement mortar, the calcination of the undercalcin, which is more than the decarboxylation reaction, gradually melts and the clinker phenomenon increases. Production of shaft kilns in the form of turntable gravity ejectors is difficult, and most of them are caused by impurities in raw materials or fuels. These impurities (SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , Na ₂ O, K ₂ O, P, S, etc.) promote fusion between calcium oxide (CaO) particles, shrinkage between particles and changes in crystal structure and Blocks are formed while reducing the specific surface area and reactivity.

In the case of limestone firing, what kind of material is produced by reacting impurity with quicklime depends on the temperature at that time, the content of impurities, and the kind.

-SiO ₂ is meta calcium silicate (CaSiO ₃ )

S is calcium sulfate (CaSO ₄ -H ₂ O type)

P is from calcium phosphate (CaPO ₄ ) to calcium diphosphate (Ca ₂ P ₂ O ₇ )

-F is produced calcium fluoride (CaF ₂ ) and the like.

-Al ₂ O ₃ , Fe ₂ O ₃ depends on the conditions at that time, but Al ₂ O _{3 ·} Fe ₂ O ₃ , 2CaO _· Al ₂ O _{3 ·} Fe ₂ O _{3 ,}

Complex calcium compounds such as 4CaO _, Al ₂ O _{3 ,} Fe ₂ O _{3 ,} 2CaO _and Fe ₂ O ₃ are produced.

In particular, in the case of dolomite (CaCO _{3 ·} MgCO ₃ ), MgO already begins to lose its reactivity due to perericase at 800 ° C., and thus, limestone containing MgCO ₃ as an impurity in limestone is more difficult when it is lightly under-fired. For example, the melting point of 2CaO-SiO ₂ in CaO-SiO ₂ compounds is 2130 ° C, and crystals have already begun to form at temperatures around 1280 ° C. In addition, impurities in limestone react with lime at low temperatures near 900 ~ 930 ℃, but they bind strongly when the temperature rises to form complex compounds such as silicate, aluminate, and ferrite.

The rotary crusher of the rotary crusher breaks the molten undercalcinated block against the melted clinker of the undercalcined lime produced during the production of such undercalcined lime.

Hereinafter, the present invention will be described in detail with reference to examples.

Examples 1-5

Limestone ore is first pulverized to 25 to 40mm, and 1600kg is added. Anthracite coal with a total calorific value of 68,000kcal is gradually increased to 114 to 122kg as shown below, and the baking temperature inside the kiln is 24 to 30 hours at 1200 ℃ to 1300 ℃. The calcined calcined lime was produced.

division Limestone
(kg) hard coal
(kcal / kg) Remarks Example 1

1600

114 Example 2 116 Example 3 118 Example 4 120 Example 5 122

Example 6

  The cracking inhibitor was prepared by mixing 100 kg (6.6 wt% of the cement weight) of the 6.6 kg cemented lime produced in Example 3 above.

 Example 7

Cracking agent was prepared by mixing 100 kg (7.9 wt% of the weight of cement) 7.9 kg cement prepared in Example 3 above.

Example 8

The cracking inhibitor was prepared by mixing 100 kg (6.6 wt% of the cement weight) of the 6.6 kg cemented lime produced in Example 4 above.

Example 9

Cracking agent was prepared by mixing 100 kg (6.6 wt% of cement weight) of 7.9 kg of cemented lime prepared in Example 4 above.

 Example 10

The cracking inhibitor was prepared by mixing 100 kg (6.6 wt% of the cement weight) of the 6.6 kg cemented lime prepared in Example 5 above.

Example 11

Cracking agent was prepared by mixing 100 kg (6.6 wt% of cement weight) of 7.9 kg of cemented lime prepared in Example 5 above.

  Undercalcium of the present invention is calcium oxide (CaO) content of 82% or more, uncalcified limestone (CaCO3) content of 8% or less, the degree of sintering is composed of 5% or less on the basis of lgloss loss,

It can be seen that the particle size distribution is undermineralized in the range of 80% to 100% through 100Mesh, 60% to 80% through 170mesh, and 40% to 60% through 325mesh.

It can be seen that the maximum temperature (Tmax) of the water temperature is less than 45 ℃, the time of reaching the maximum temperature (Tmax) 30 minutes or more by reacting 400 g of the undercalcined with 100 g of 25 ° C water.

Experimental Example  One.

Limestone ore is first crushed to 25 to 40mm and 1600kg is added, and the anthracite coal of 68,000kcal is gradually increased from 114 to 122kg as shown in the table below.The firing temperature inside the kiln is increased from 1200 ℃ to 1300 ℃ for 24 hours. The sintering performance for dry shrinkage of reactivity and dry cement mortar according to the degree of sintering by firing for 30 hours was confirmed as shown in Table 4.

With increasing anthracite coal from sample 1 to sample 5, the decarbonate reaction of limestone proceeded actively, resulting in a low CaCO3 content, a proportionally increased CaO content, and a comparison of lg-loss. Example 1 was 12.95%, and Examples 2, 3, 4, and 5 in the order of increasing the anthracite gradually reduced the ignition loss (by KS L 5120 test method) was confirmed that the plasticity was increased.

 Comparison of Quicklime Composition According to Firing Degree division Limestone
(kg) hard coal
(kcal / kg) Total calories
(kcal) CaO
(%) CaCO3
(%) Ignition loss
(lg-loss) Example 1 1600 114 775,200 70.26 22.33 13.44 Example 2 116 788,800 73.16 20.70 10.9 Example 3 118 802,400 77.03 13.45 7.62 Example 4 120 816,000 82.04 8.42 4.13 Example 5 122 829.600 84.21 3.21 2.61

As a test method to check the reactivity according to the degree of calcining of quicklime, the results of the digestibility test showed that the loss of ignition (chemical analysis method of KS L 5120 Portland cement), which is the basis of the degree of calcining, is more than 5% as shown in FIG. 2 and Table 5. In Examples 1, 2, and 3, which were not calcined until the inside of quicklime, the pores developed by the decarboxylation reaction on the outer surface showed rapid reactivity when reacted with water, and this initial reaction was immediately followed by all the reactions. It can be terminated immediately and a sudden temperature loss can be confirmed. On the other hand, the samples of Examples 4 and 5, whose ignition loss (chemical analysis of KS L 5120 Portland cement) is less than 5%, have a lower maximum temperature (Tmax) when reacted with the initial water than the samples 1 to 3, The maximum temperature reaching time (Tmax-T) shows a prolonged pattern, which proceeds slowly when reacting with water as the decarburization reaction proceeds from the outside to the inside, while the external pores of the under-calcium melt at high temperatures. When used as an expansion material for cement mortar, it gives sufficient expansion force in middle and long-term age after the initial age.

 Quicklime Digestibility Test Results According to Firing Degree division Tmax Tmax
Time to reach Example 1 46.3 10 "20 Example 2 44.2 17 "40 Example 3 43.7 31 "40 Example 4 40.6 46 "20 Example 5 36.7 49 "20

Demonstration  2.

The final application of the dry cement mortar to the present invention as a swelling material is a test for evaluating dry shrinkage, and the 1M length change test was conducted in the same manner as in FIG. 3.

Cracking agent prepared by adding 2 to 10wt% of the cement weight ratio during dry cement mortar blending in comparison with the expansion material (lime-anhydrite-free gypsum), which is conventionally used in Example 1 for the underlime lime tested in Experimental Example 1 (dry cement mortar) The expansion performance of was compared as shown in FIG.

 Experimental Example 3.

Cracking agent prepared by adding 2 to 10wt% of the cement weight ratio during dry cement mortar blending in comparison with the expansion material (quick lime-anhydrous gypsum), which is used in Example 2 for the underlime lime tested in Experimental Example 1 (dry cement mortar) The expansion performance of was compared as shown in FIG.

Experimental Example  4.

Cracking agent prepared by adding 2 to 10wt% of the cement weight ratio during dry cement mortar blending in comparison with the expansion material (lime-anhydrite-free gypsum), which is used in Example 3 for the underlime lime tested in Experimental Example 1 (dry cement mortar) The expansion performance of was compared.

Experimental Example  5.

Cracking agent prepared by adding 2 to 10wt% of the cement weight ratio during dry cement mortar blending in comparison with the expansion material (quick lime-anhydrous gypsum), which is conventionally used for the underlime lime example 4 verified in Experimental Example 1 (dry cement mortar) The expansion performance of was compared as shown in FIG.

Experimental Example  6.

Cracking agent prepared by adding 2 to 10wt% of the cement weight ratio during dry cement mortar blending in comparison with the expansion material (general quicklime-anhydrite gypsum), which is used in Example 5 for the underlime lime tested in Experimental Example 1 (dry cement mortar ) Was compared with the expansion performance.

As a result of the test results of Experimental Examples 2 to 6 as described above, compared to the conventionally used crack inhibitors (expandable material; ordinary quicklime-anhydrous gypsum), all samples of the undercalcined calcining conditions of Examples 1 to 5 of Experimental Example 1 with excellent expansion performance It can be applied as a crack preventing material, in particular, the samples of the firing conditions of Examples 4 and 5 can be applied as a crack preventing material with excellent expansion performance with a very small addition amount compared to the existing.

Experimental Example  7.

Example 3 verified in Experiment 1 The same calcium calcite (CaO) content, calcined limestone (CaCO3) content 13.45% ignition loss (lgloss) 7.62 % Of cement samples in dry cement mortar formulations compared to the existing crack-preventing materials (quick lime-anhydrous gypsum) compared to the existing samples of undermineralized lime (Tmax) 42.8 ° C and 31 min (TmaxT) at the digestibility test. Thirty households (equilibrium -127m2) were actually cast for each test condition of the apartment houses under construction in Cheongna district, Seo-gu, Incheon, with 6.6wt% and 7.9wt% weight ratios (see Fig. 9). The amount generated was measured, and the results are shown in Table 6 below.

Exam conditions
Crack generation amount (m / flat) 4 weeks 6 weeks of age 8 weeks of age Existing Cracking Agent 0.15 0.31 0.45 Example 6 0.14 0.29 0.41 Example 7 0.12 0.25 0.36

Experimental Example  8.

The calcium oxide (CaO) content 82.04%, the uncalcined limestone (CaCO3) content 8.42%, and the ignition loss (lgloss) 4.13% of the sample of undercalcined lime with a maximum temperature (Tmax) of 43.2 ° C and a maximum temperature reaching time (TmaxT) of 36 minutes in comparison with the existing crack preventing material (quick lime-anhydrous gypsum) during formulation of dry cement mortar With the test conditions adding 6.6wt% and 7.9wt% of the cement weight ratio, 30 households (equilibrium -108m2) were actually cast for each test condition of the apartment houses under construction in Cheongna district, Seo-gu, Incheon (see Fig. 10). The crack incidence was measured and the results are shown in Table 7 below.

Exam conditions
Crack generation amount (m / flat) 4 weeks 6 weeks of age 8 weeks of age Existing Cracking Agent 0.09 0.23 0.37 Example 8 0.03 0.13 0.21 Example 9 0.00 0.07 0.14

Experimental Example 9.

Example 5 verified in Experiment 1 In the same way as the firing conditions, calcium oxide (CaO) content 84.21%, uncalcined limestone (CaCO3) content 3.21%, and lgloss In comparison with the existing crack preventing material (quick lime-anhydrous gypsum), the sample of undercalcinated with 2.61%, the maximum temperature (Tmax) 40.4 ° C and the maximum temperature reaching time (TmaxT) 44 minutes in the digestibility test was mixed with dry cement mortar. Thirty households (equilibrium -127m2) for each test condition were cast in actual mechanized construction for the D-House, which is being constructed in Baekhyeon-dong, Bundang-gu, Seongnam-si, Gyeonggi-do, with the test conditions adding 6.6wt% and 7.9wt% of the cement weight ratio. 11) The crack incidence was measured and the results are shown in Table 8 below.

Exam conditions
Crack generation amount (m / flat) 4 weeks 6 weeks of age 8 weeks of age Existing Cracking Agent 0.13 0.25 0.39 Example 10 0.50 0.09 0.14 Example 11 0.00 0.04 0.10

As a result of the production of undercalcined lime according to the degree of plasticity as a crack prevention material of dry cement mortar, which is constructed by mechanized construction of the ondol floor of a multi-family house, it was applied to the actual multi-unit housing site. In comparison with the crack incidence of ash, excellent crack reduction performance was confirmed.

Claims (3)

In the method for producing undercalcined lime,
Limestone ore is calcined at 1200 ℃ to 1300 ℃ for 24 to 30 hours,
Calcium oxide (CaO) content of more than 82%, uncalcined limestone (CaCO3) content of less than 8%, the degree of calcination is produced by less than 5% on the basis of the loss (lgloss) . The method according to claim 1, wherein the under-lime reacts with the under-lime lime 400g and 25 ℃ 100g water, the maximum temperature (Tmax) of the water temperature is less than 45 ℃, the maximum temperature (Tmax) reaching time is characterized in that more than 30 minutes Method for preparing underlime lime. In the method used as a crack inhibitor,
Limestone ore is calcined at 1200 ℃ to 1300 ℃ for 24 to 30 hours,
Calcium oxide (CaO) content is 82% or more, uncalcined limestone (CaCO3) content is 8% or less, and the degree of calcination is less than 5% based on lgloss. Mixing to 10wt% to use as a crack preventing agent.

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