KR100303235B1 - crack retardant mixture for cement mortar and cement mortar by using it for heating floor(on-dool) - Google Patents

Abstract

The present invention relates to cement mortar used in the floor of the house, the purpose is that the initial shrinkage does not occur and the shrinkage reducing material that can be used according to the seasonal characteristics with high expression rate of 28 days compressive strength and for finishing plastering using this reducing material In providing a composition of cement mortar.

The present invention for achieving the above object

Quicklime: 10-30 weight, Gypsum: 20-40 weight, Coal ash: 10-20 and the shrinkage reducing material for cement mortar composed of the remaining petroleum coke combustor

(a) cement: 70-85 weight and

(b) Quicklime: 10 to 30 wt%, gypsum: 20 to 40 wt%, coal ash: 10 to 20 and shrinkage reducing material composed of combustion materials of the remaining petroleum coke: 15 to 30 wt% of the raw material blended, granulation rate (FM) The technical gist of cement mortar for ondol finishing finishing composed of sand of 2.8 or more is considered to be the technical basis.

Description

Shrink retardant for cement mortar and cement mortar for plastering with ondol finishing {crack retardant mixture for cement mortar and cement mortar by using it for heating floor (on-dool)}

The present invention relates to a cement mortar used in a house floor, and more particularly, to a shrinkage reducing material capable of preventing cracking due to dry shrinkage of a simeth mortar and a cement mortar using the reducing material.

In recent years, as the construction of houses has increased quantitatively and the houses have become higher and larger, the mechanized construction of cement mortar pumping and plastering on the floor is rapidly spreading. Mechanized construction is a situation in which excessive water is added for the convenience of pump pumping, so serious crack defects of about 1m / pyeong occur after construction.

These cracks are caused by shrinkage during cement condensation and are most affected by the composition of cement, the powder of cement, the amount of water, and the like. In order to prevent shrinkage cracking of cement, it is known to use an expansion cement that can expand to a degree that compensates for dry shrinkage.

K, S, M and O types are developed and used in the United States, Japan, etc., and they are used in cement as (3CaO · Al ₂ O ₃ · CaSO ₄ ) · CaO · CaSO ₄ , (3CaO · Al ₂ O ₃ ) And one of CaSO ₄ , CaO, or CaSO ₄ are mixed in an appropriate amount to secure the expandability of the cement. The expansion cement expands by (1) swelling by absorbing moisture during the formation of etringite (3CaO.3CaSO ₄ .32H ₂ O), or (2) CaO added to form crystals of calcium hydroxide. It is known to become.

By the way, the expansion cement known so far is difficult to apply as a cement mortar for finishing the floor of the general housing complex. Therefore, a technique has been attempted to mix and use a shrinkage reducing material that is essentially blocking the cause of cracks by compensating for shrinkage by chemically introducing expansion force corresponding to the shrinkage amount of cement mortar into cement.

A representative example thereof is a shrinkage reduction mortar for ondol finishing plastering proposed by the present inventor and proposed in Korean Unexamined Patent Publication No. 1996-34119. The mortar is composed of petroleum coke combustors and cement, which are wastes generated in oil refineries. However, this shrinkage reduction mortar is difficult to obtain sufficient plastering time due to the shortening of the initial setting time, the early cracking may occur, and the 28-day compressive strength expression is slow, and the differential mixing due to seasonal characteristics is difficult. Disadvantages of shrinkage reduction mortar are believed to be due to the following causes.

(1) initial crack

In the petroleum coke combustor, CaO, SiO ₂ and Al ₂ O ₃ are the main constituents, and the main component CaO includes 40 to 50 gypsum (CaSO 4) components combined with sulfur dioxide during petroleum coke combustion. An example of petroleum coke combustor is shown in Table 1 below.

Chemical composition (weight) CaO SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ MgO K ₂ O Na ₂ O ₃ Test Methods 75.9 12.44 3.38 0.33 0.55 0.11 0.19 KSL 5120-90 I.C.P. analysis Powder level (mm) 1.18 or higher 1.18-0.6 0.6 to 0.25 0.25-0.177 0.177 to 0.125 0.125 to 0.105 0.105-0.075 Less than 0.075 2.1 5.8 24.6 16.7 17.2 7.5 9.8 16.3

As can be seen in Table 1, the petroleum coke combustor is low in powder, it is estimated that the initial crack occurs due to the surface powder is lowered by the phenomenon that the particles are floating on the surface (latency phenomenon). Of course, there is an advantage that the surface is smooth after finishing due to the latent phenomenon.

In addition, the petroleum coke combustor contains a lot of CaO, and the high heat of hydration of CaO shortens the initial setting time, thereby securing sufficient plastering time (at least about 4 hours and 30 minutes of plastering time). As such, it was analyzed that an initial crack occurred.

(2) 28-day intensity expression rate

Gypsum contained in petroleum coke combustor contains a large amount of hemihydrate gypsum and dihydrate gypsum, which caused coagulation delay, resulting in about 70 days of strength development.

(3) Seasonal Characteristics

As such, shrinkage reduction mortar for plastering ondol is mainly composed of petroleum coke combustor and cement, so it is not possible to control the initial setting time of mortar during summer and winter, especially in summer when delay of initial setting time is required. There is a disadvantage of falling characteristics.

The present invention was devised in a series of studies to improve the shortcomings of shrinkage reduction mortar made from petroleum coke combustors, the initial crack does not occur, as well as the high expression rate of 28 days compressive strength and seasonal characteristics The present invention proposes a composition of shrinkage reducing materials capable of differential blending and a composition of cement mortar for plastering ondol finishing using the materials.

1 is a graph showing the change in length for each type of plaster

2 is a graph showing the change in length according to the composition of the shrinkage reducing material

The shrinkage reducing material of the present invention for achieving the above object is composed of quicklime: 10-30 weight, gypsum: 20-40 weight, coal ash: 10-20 and the remaining petroleum coke combustion material.

In addition, the cement mortar for plastering ondol finishing of the present invention,

(a) cement: 70-85 weight and

(b) Quicklime: 10 to 30 wt%, gypsum: 20 to 40 wt%, coal ash: 10 to 20 and shrinkage reducing material composed of combustion materials of the remaining petroleum coke: 15 to 30 wt% of the raw material blended, granulation rate (FM) It is composed of sand of 2.8 or more.

Hereinafter, the present invention will be described in detail.

[Reduction Reduction Material]

In the petroleum coke combustor used in the present invention, when the limestone and petroleum coke are combusted in a fluidized bed combustion boiler or a lime kiln, the petroleum coke is burned entirely, and the sulfides contained in the petroleum coke are combined with the gypsum component of the lime. It is a byproduct formed from ash. Petroleum coke combustors usually occur when a mixture of 30 to 70 weight of limestone and 30 to 70 of petroleum coke is combusted at high temperature (about 800 ° C). Petroleum coke is a heavy oil (bunker C) Use the residual oil that comes out when the diesel is extracted from Yu). Therefore, as shown in Table 1, the petroleum coke combustor mainly contains CaO, SiO ₂ , Al ₂ O ₃ , and CaO contains gypsum (CaSO 4) component combined with sulfur dioxide during petroleum coke combustion. 40-50 exists.

In the present invention, (1) quicklime, (2) gypsum, to improve the initial crack, 28-day strength expression, seasonal characteristics that occur when using the petroleum coke combustor as cement mortar for ondol finishing (3) Coal ash is blended at the proper mixing ratio, which has its characteristics.

(1) quicklime (CaO)

Quicklime has expandability and can be effectively used as a shrinkage reducing material. In the present invention, the quicklime is added to adjust the powder level based on the expansion characteristics. If the particle size of quicklime is used to less than 100 mesh (mesh) or more, it can be confirmed that when the cement mortar is used, the surface powder is increased to prevent the occurrence of initial cracking. Quicklime usually has a CaO of 80 to 90 and a particle size of less than 100 mesh (mesh) of 10 or less. Therefore, in order to make 100 mesh or less into 40 or less, it is necessary to mix quicklime with high powder density, but in this invention, quicklime dust is used. Quicklime dust is produced during quicklime production, with 100 mesh residue of 40 or more and CaO content of 50-70. Accordingly, in the present invention, the quicklime and the quicklime dust are appropriately mixed so that 100 mesh or less is 40 or less. Since the quicklime dust has a low CaO content, the heat of hydration can be lowered, which is effective in preventing the initial coagulation crack.

In the present invention, the quicklime is added to the shrinkage reducing agent in 10 to 30 weight, which is less than 10 wt% of the quicklime, so that the surface powder is low, so if the inhibitory effect of the initial cracking is less than 30, it is disadvantageous to long-term cracking. Because.

(2) gypsum

In the present invention, the gypsum is added to suppress the long-term shrinkage cracking caused by the lack of the production amount of the Ettling gate effective in the expansion while the quicklime is contained in the petroleum coke combustion material, the addition amount is 20 to 40 desirable. The reason is that when the gypsum is less than 20 wt%, it is difficult to expect the additive effect, and when the gypsum exceeds 40 wt%, secondary expansion may occur when moisture is penetrated from the outside after curing.

In the present invention, gypsum can be any gypsum, hydrated gypsum, hemihydrate gypsum, it is preferable to use anhydrous gypsum in winter and hydrated gypsum in summer. The reason is that Isu gypsum has a longer initial setting time than anhydrous gypsum and is advantageous in summer.

(3) fly ash

Coal ash in the present invention serves to prevent the initial crack by reducing the heat of hydration of the petroleum coke combustion material. In addition, it improves the fluidity of mortar to play a role as a water reducing material. Coal ash is preferably blended 10 to 20, which is less than 10 when the mixing ratio of coal ash is insignificant, and when it exceeds 20, it reduces the expandability of the shrinkage reducing material.

[Cement mortar]

Cement mortar of the present invention

(a) cement: 70-85 weight and

(b) Quicklime: 10 to 30 wt%, gypsum: 20 to 40 wt%, coal ash: 10 to 20 and shrinkage reducing material composed of combustion materials of the remaining petroleum coke: 15 to 30 wt% of the raw material blended, granulation rate (FM) It is composed of sand of 2.8 or more.

In this case, the shrinkage reducing material is preferably mixed with cement in a mixing ratio of 15 to 30 weight, because less than 15 weight is less inflating effect, and if it exceeds 30, it may overexpand.

In addition, although the mixing ratio of the raw material and sand which consist of a shrinkage reducing material and cement is a conventional method, it is usually 1: 2.5-3. Importantly, the granulation rate of sand is set to 2.8 or higher, in order to prevent the initial cracking by increasing the mortar powder when cement mortar is applied.

Cement mortar of the present invention can be added to the air entrainer, water reducing agent, thickener in the usual way to facilitate pump pressure and finishing plastering.

Hereinafter, the present invention will be described in detail through examples.

Example 1

Gypsum of Table 2 per ton of dry mortar was mixed 40kg (unit quantity 15-16) for each type, and the settling time for each gypsum was measured in Table 3 and the length change rate was shown in FIG. The setting time was measured on the basis of the initial time at 20 ℃ temperature. In addition, the length of the mortar specimen was cured for 24 hours in a constant temperature and humidity chamber of 20 ℃, 95 RH, demolded and measured the initial length using a length change meter, and after the measurement again put into a constant temperature and humidity chamber of 20 ℃, 60 RH It was measured after curing at predetermined intervals of measurement, that is, 7 days and 28 days.

division Manufacturing method One Gypsum plaster 2 days drying in the air, free water removal 2 Half gypsum 2 hours at 120 ℃ 3 Anhydrous Gypsum A 1 hour firing at 500 ° C in a kiln 4 Anhydrous Gypsum B 1 hour firing at 800 ° C in a kiln 5 Anhydrous Gypsum C Firing at about 900 to 1,200 ° C

Formulation No One 2 3 4 5 Condensation (hour: minute) 9:03 8:40 6:00 6:40 9:42

As shown in Table 3, coagulation and expression were performed in the order of anhydrous gypsum (500 ℃), anhydrous gypsum (800 ℃), hemihydrate gypsum, dihydrate gypsum, anhydrous gypsum (above 900 ℃). In particular, in the case of anhydrous gypsum (above 900 ℃), the condensation delay phenomenon was remarkable, which was judged as the quality effect of gypsum firing and calcined gypsum.

As shown in FIG. 1, the length change (expansion and contraction) of each gypsum showed the same level of expansion rate for the three types of anhydrous gypsum, but slightly diminished in the case of hemihydrate gypsum and dihydrate gypsum. The reason for this is that the content of SO ₃ in the three species causing expansion reaction decreases in the order of the same level but in the order of hemihydrate gypsum and dihydrate gypsum.

Example 2

50 kg of shrinkage reducing materials containing petroleum coke combustors, quicklime, gypsum and coal ash (Dangjin Thermal Power Plant) as shown in Table 5 were mixed 50 kg per ton of dry mortar (15 to 16 units) and the coagulation time was measured. It is shown in Figure 2 and measured the length change rate. Quicklime was used by mixing the quicklime dust and quicklime B grade in 1: 1 in Table 4, and the granulation rate of sand was 2.8.

division Chemical composition (weight) CaO SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ MgO Ig-Loss Quicklime Dust 60.84 11.47 2 2 5.39 18.3 Quicklime Class B 80.26 7.8 One One 1.2 8.7 division Particle Size Distribution (Remaining) 300㎛ 150 μm 75 μm Pan Quicklime Dust 14 16 16 54 Quicklime Class B 10 10 32 48

division Petroleum coke combustors quicklime Anhydrous Gypsum (500 ℃) Coal ash One 100 - - - 2 70 10 20 - 3 50 10 20 20 4 50 20 10 20 5 30 - 50 20 6 30 10 40 20 7 30 20 30 20 8 30 30 20 20 9 30 40 10 20

division One 2 3 4 5 6 7 8 9 Condensation time (hours: minutes) 5:05 5:20 5:40 5:45 6:15 6:00 6:00 6:15 6:50

As shown in Table 6, it was found that the condensation time was delayed in the case of using quicklime, anhydrous gypsum and coal ash rather than using 100 petroleum coke combustors as shrinkage reducing materials.

In the case of using 30 petroleum coke combustors (No 5, 6, 7, 8, 9), it was found that the setting time was increased when the mixing ratio of quicklime was high.

Example 3

5 to 25 shrinkage reducing materials having the composition of Table 7 in cement 5 were mixed, mixed with sand to form mortar, and the physical properties of the mortar were measured and shown in Table 8.

The change of length of mortar was made by specimen and the change of length according to drying condition and age was measured. The mixing amount of mortar was tested by specifying the amount of 100 ± 5 flow rate defined in KSL 5220 Cement-based dry mortar with general mortar. .

material Binder (Cement + Shrinkage Reducing Material) Sand (dry sand) water Compounding cost 280 720 155

Amount of weight reduction in binders Flowchart () Air volume () Compressive strength (kgf / cm ² ) Length change (× 10 ^-5 ) 7 days 28 days 7 days 28 days 5 98 13.8 175 248 245 -320 10 96 14.2 171 235 420 -270 20 94 14.5 159 220 525 85 25 90 14.7 140 208 640 110 General mortar (cement + sand) 100 13.0 180 255 -410 -920

Mortar containing 10 shrinkage reducing materials showed little change in length and expected to have the desired cracking effect.However, in the case of actual processing, cracking appeared and 20-25 containing shrinkage reducing materials with expansion effect. No cracks appeared. This is believed to be due to the expansion of the shrinkage reducing material compensated for the shrinkage of the cement during the drying process.

After the shrinkage reducing material of the present invention prepared according to the above embodiment was put into a general cement mortar and a conventional blender (cement weight ratio 25) and poured into 50 places of ondol floors and living rooms (31 pyeong) of a construction under construction with a thickness of 50 mm. The crack occurrence by dry shrinkage was observed. Since mortar finishes the floor finishing work by pressing the trowel four or five times after pouring for 1-2 hours, there was little occurrence of plastic shrinkage cracking. After curing for 2 months, there was no dry shrinkage crack on each floor of the ondol, so heating was run for 1 month after covering some households with monolium and cardboard to observe the change after heating. As a result, there was no discoloration of monolium and a sheet of paper, but a crack occurred rarely. The mortar of the cracked part was found to be a result of insufficient heating pipe coating thickness (within 15 mm of coating thickness). As a result of the in-site casting, the shrinkage reducing material according to the present invention showed little cracking and had an effect of suppressing dry shrinkage cracking of mortar for ondol finishing.

As described above, in the present invention, the initial crack does not occur, as well as the 28-day compressive strength expression rate is high, and has a useful effect of providing a cement mortar exhibiting excellent properties for the ondol finisher by differentially mixing according to seasonal characteristics.

Claims (6)

Quicklime: 10 to 30 wt%, gypsum: 20 to 40 wt%, coal ash: 10 to 20 and shrinkage reducing material for cement mortar composed of the remaining petroleum coke combustors. The shrinkage reducing material for cement mortar according to claim 1, wherein the quicklime has a particle size of less than 100 mesh. The method according to claim 1 or 2, wherein the quicklime is (a) 100 mesh residues of 10 or less, and CaO of 80-90 (b) Shrinkage reduction material for symmetal mortar, characterized in that the 100 mesh (mesh) residue content is more than 40, CaO content is used by mixing the quicklime dust of 50-70. The shrinkage reducing material for cement mortar according to claim 1, wherein the gypsum is anhydrous gypsum in winter and dihydrated gypsum in summer. (a) cement: 70-85 weight and (b) Quicklime: 10 to 30 wt%, gypsum: 20 to 40 wt%, coal ash: 10 to 20 and shrinkage reducing material composed of combustion materials of the remaining petroleum coke: 15 to 30 wt% of the raw material blended, granulation rate (FM) Ondol finishing plaster mortar made of sand of 2.8 or more. [6] The cement mortar for finishing plaster of claim 5, wherein the quicklime has a particle size of 100 mesh or less.