KR19990088043A - Cement composition - Google Patents

Abstract

The present invention calcinates a cement clinker containing CaO crystals having a hardening effect of cement in advance, and adds and mixes gypsum dihydrate or alkali sulfate with it to maintain fluidity until concrete is poured. After pouring it, the cement composition showing high strength at early stage is to be obtained. Cement clinker composed mainly of 3CaO · SiO ₂ -gap material-CaO crystal is composed of two gypsum or two gypsum and sulfuric acid. Cement clinker is a super-rigid cement composition pulverized with alkali. The cement clinker has a silicic acid ratio of 2.0-5.0, an iron ratio of 0.5-4.0, a CaO grain size of 13 ?? m or more, and a CaO crystal mass of the cement clinker. 3 to 10% by weight relative to the amount, the cement powder is characterized in that the Blaine specific surface area of 3000-6000 cm ² / g.

Description

Cement composition {CEMENT COMPOSITION}

The present invention mainly relates to the cement composition used in the civil engineering and construction fields, especially in the case of mortar and concrete, the required fluidity is obtained and the change over time is small, the molding of concrete products or the transportation, pouring, finishing of concrete The present invention relates to a cement composition having properties such as maintaining fluidity within a sufficient time and expressing high strength early and reducing demolding time after pouring concrete.

Applicant has already proposed PCT / JP97 / 04239 as a cement composition that has the necessary fluidity to transport, place and finish raw concrete, express high strength early and reduce demolding time after placing concrete. .

The present invention is a so-called dead burning quicklime powder having a slow hydration rate for a portland cement or a mixed cement or a cement composition in which alkali sulfate is added and mixed thereto. After the casting and pouring, the high strength was developed early to accelerate the turnover of the formwork, and also to allow the product to be shipped early with no steam curing or with some steam curing.

However, according to the cement composition of the present invention, light calcined lime produced in a completely different process from the base Portland cement clinker must be used. In addition, there is a problem in that a large amount of fuel is required to produce this light lime.

The present invention calcined the cement clinker containing the CaO crystals having the effect of promoting the hardening of the cement in advance, and added and mixed with two gypsum or alkali sulfate therein to maintain fluidity until the concrete is poured. Afterwards, it is intended to obtain a cement composition exhibiting high strength at an early stage.

1 is a diagram showing the relationship between the firing conditions of clinker and the grain size of CaO.

Fig. 2 is a graph showing the relationship between the CaO crystal grain size in the clinker and the exothermic curve of mortar.

3 is a view showing the relationship between the firing conditions of clinker and the compressive strength of mortar.

4 is a graph showing the relationship between the CaO crystallite amount and the CaO crystal grain size.

5 is a graph showing the relationship between the CaO crystallite amount and the compressive strength of mortar.

Fig. 6 is a graph showing the relationship between the CaO crystal amount and the compressive strength of mortar.

Fig. 7 shows the relationship between the firing conditions of the clinker and the amount of CaO crystals.

8 is a graph showing the relationship between the Na ₂ SO ₄ addition rate and the mortar compressive strength of the cement component.

9 is a diagram showing the effect of the addition of Na ₂ SO ₄ on the exothermic properties of mortar.

10 is a diagram showing the relationship between the cementity of cement and the compressive strength of mortar.

11 is a diagram showing the influence of material age on the compressive strength of mortar.

Fig. 12 is a graph showing the relationship between water cement ratio and mortar compressive strength and flow;

13 is a diagram showing the effect of material age and curing conditions on the compressive strength of concrete.

The present invention is a super-rigidity cement composition obtained by grinding a cement cement comprising 3CaO.SiO ₂ -spacer material-CaO crystal as the main mineral composition with two gypsum dihydrate, and the silicic acid ratio of the cement clinker. 2.0-5.0, iron ratio is 0.5-4.0, CaO grain size is 13 ?? m or more, CaO crystal is 3-10% by weight relative to the total amount of cement clinker, and cement powder is 3000- in surface area of Blaine. Cement composition characterized in that it is 6000 cm ² / g (Claim 1), 3CaO · SiO ₂ -Gap material-Cement clinker whose main mineral composition is CaO crystals. As for the cement clinker, the silicic acid ratio is 2.0-5.0, the iron ratio is 0.5-4.0, the CaO grain size is 13 ?? m or more, the CaO crystal amount is 3-10% by weight relative to the total amount of the cement clinker, Blaine) and with a specific surface area 3000-6000cm ² / g, the addition amount of the alkali sulfate is Cement composition (claim 2) and claim 2 added to the cement clinker according to claim 2, characterized in that the content of the pure cement clinker excluding the amount of CaO in the cement clinker and the added 2 gypsum in anhydride conversion 0.5-3.0% by weight. Cement composition (claim 3), wherein the alkali sulfate is sodium sulfate or potassium sulfate.

The present invention provides a super-rigid cement composition obtained by grinding a cement clinker containing 3CaO.SiO ₂ -spacer material-CaO crystals as a main mineral composition with two gypsum dihydrates. The ratio, iron ratio, CaO grain size, CaO crystal amount, and cement powder are also defined.

First, the form and amount of CaO crystals remaining in the cement clinker will be described. In general, although CaO is obtained by calcining limestone, it is known that the hydration reaction rate varies depending on the degree of densification.

In other words, the densified well is called light CaO, and when contacted with water, the hydration reaction proceeds while gradually generating heat. On the other hand, combustion CaaO, which is light in density, immediately reacts with water and generates heat. In order to promote the hardening of the cement using the heat of CaO, at least medium or larger CaO must be used.

This is because when CaO of combustion is mixed with cement and water is added thereto, the hydration reaction takes place immediately to generate heat, the hardening reaction of the cement proceeds rapidly, and the fluidity of the cement decreases rapidly. Therefore, it is indispensable to delay the hydration reaction of the CaO crystals remaining in the cement clinker to some extent. To this end, it is necessary to sinter the cement clinker sufficiently at a high temperature to increase the grain size of CaO to a small state.

Therefore, using the raw materials shown in Table 1, various cement clinkers were prepared according to the mixing conditions shown in Table 2, and the CaO crystal grain size was measured by a scanning electron microscope and a reflecting microscope. The results are shown in FIG.

TABLE 1

Raw material of clinker

SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO lg. loss Total Limestone 0.11 0.61 0.11 54.68 0.97 42.62 99.10 clay 50.40 35.50 0.27 0.01 0.01 13.80 99.99 burr 98.62 0.56 0.03 0.39 0 0 99.60 Iron oxide 0 0 100 0 0 0 100

TABLE 2

Clinker Raw Material Blending

Formulation No. One 2 3 4 5 6 7 8 Limestone (%) Clay (%) Quartzite (%) Iron oxide (%) 79.627.0411.411.93 80.226.8011.111.87 81.006.4810.731.79 81.796.1510.341.72 82.505.869.991.65 83.005.659.741.61 83.435.489.531.56 83.955.289.251.52 CaO (%) SiO ₂ (%) Al ₂ O ₃ (%) Fe ₂ O ₃ (%) MgO (%) Others (%) 66.9522.874.683.131.191.18 67.6822.314.573.051.201.19 68.6421.584.422.941.221.20 69.6320.824.262.851.231.21 70.5120.144.122.751.251.23 71.1419.654.022.691.261.24 71.6919.243.942.621.271.24 72.3618.703.842.571.281.25 Hydroponics 2.182.931.50.94 2.262.931.50.97 2.372.931.51.02 2.492.931.51.07 2.612.931.51.12 2.702.931.51.16 2.782.931.51.19 2.882.921.51.24

As shown in Fig. 1, it can be seen that the CaO crystal grain size becomes larger in the case where the maximum temperature at the time of firing is 1,500 ° C than in the case of 1450 ° C. Cement was made using the clinker thus obtained, and the exothermic test was performed.

That is, two hydrated gypsum was added to the cement clinker calcined at 1450 ° C. and the cement clinker calcined at 1500 ° C., respectively, and the cement was pulverized to 5000 cm ² / g with a specific surface area of the brain. 1 part by weight of this cement, 2 parts by weight of sand (particle size 2.5 or less), 0.37 part by weight of water, and 0.01 part by weight of a water reducing agent (Mighty 150, Co., Ltd.) were used as mortar. In addition, the sand used CaO crystals in the clinker as sand components and subtracted the volume fraction. The result of the exothermic test of the mortar is as shown in FIG.

As shown in Fig. 2, when the CaO crystal grain size is 13 ?? m or more, it can be seen that the temperature rise after mortar kneading is small and the predetermined fluidity can be secured. As for the compressive strength, as shown in Fig. 3, when the CaO crystal grain size is 13 ?? m or more, the daily compressive strength of the cement mortar (curing in humid air at 20 ° C, particle size 1.5cm, height 3.0cm) ) Is also large, and the cement hardening body is excellent in the expression of the initial strength. In this way, in the present invention, a cement clinker having a CaO grain size of 13 ?? m or more is used.

Next, regarding the amount of CaO crystals in the cement clinker, cement clinkers having different amounts of CaO crystals were calcined by the formulations shown in Table 2 using the raw materials shown in Table 1, and cement powders were prepared in the same manner as described above to form the cement powder. The relationship between the crystal amount and the grain size of CaO was investigated. The result is shown in FIG. 4 shows the relationship between the amount of CaO crystallized in the cement clinker and the particle size of the CaO crystallized in the cement clinker made under the same firing conditions. According to this, it can be seen that when the CaO crystal amount is 3-10% by weight, the crystal grain size is 13 ?? m or more.

Next, in the adjusted cement powder, when the CaO crystal is regarded as the cement component (mortar compound ①), and the mixture of clinker and dihydrate gypsum remaining after the CaO crystal is regarded as the admixture is used as the cement component (mortar compound ② ), When CaO crystal is regarded as a mixed material and anhydrous sodium sulfate is added 1.0% by weight to the cement component (mortar mix ③), 1 part by weight of cement component: sand (2.5 mm or less), 2 parts by weight of water. 0.37 parts by weight: mortar kneaded at a ratio of 0.01 part by weight of a water reducing agent (Mighty-150).

In the case of mortar compound ②, CaO crystal was considered, and in the case of mortar compound ③, CaO crystal and sodium sulfate were regarded as a part of sand, and each raw material was mix | blended with the same volume of sand removed. Similar tests were also performed on mortars using ordinary Portland cement and crude steel Portland cement which are commercially available for comparison. These test results are shown in FIG. 5 and FIG.

As shown in Figs. 5 and 6, in the case of the mortar compound ① and the mortar compound ②, although the amount of CaO crystallization in the cement clinker increases and the compressive strength increases even if the firing conditions are changed, the amount of CaO crystal is 5-7% by weight. It falls as an upper limit and when CaO crystal quantity becomes 10-12 weight%, CaO crystal quantity may be lower than zero thing. In addition, when sodium sulfate is added as shown in the mortar mixture ③, the strength is remarkably increased, but when the CaO crystal amount is 5-7% by weight, the maximum value of the strength is also shown.

When sodium sulfate is added, the strength is large compared to the CaO crystal amount being 0 even when the CaO crystal amount is 12% by weight.

As described above, the amount of CaO crystals having a great effect of promoting the hydration of the cement component of the present invention, i.e., the component composed of 3CaOSiO ₂ and the spacer material and increasing the initial strength, is 3-10% by weight of the total amount of cement clinker. As%, it can be seen that it is 5-7% by weight that can express the maximum effect.

Mortar mix ① and mortar mix ② are both nos. 4 and No. Cement compositions using a cement clinker of 5 (5.1 wt% and 7.1 wt% CaO crystals) indicate that the mortar daily strength is 2.3-2.5 times higher than that of ordinary portland cement, which is extremely excellent.

Cement clinker containing such a CaO crystal is obtained by densifying the raw material mixture at a temperature of 1500 ° C or higher. That is, as shown in FIG. 1, when the highest temperature of densification is 1450 ° C, the CaO grain size is not only small as compared with the case where the highest temperature of densification is 1500 ° C, and as shown in FIG. Even when a raw material is used, a large amount of CaO crystals are present.

In the case of the maximum temperature of densification 1450 ℃ is, it is possible by X-ray diffraction confirmed the 2CaO · SiO ₂ in the cement clinker, when the maximum temperature of the high-density low changes from 2CaO · SiO ₂ to 3CaO · SiO ₂ It is thought that the ratio is small. In addition, as shown in FIG. 2, when the maximum temperature is 1450 ° C., the CaO crystals are considered to be in a combustion state because they exhibit a tendency to generate heat prematurely in the case of 1500 ° C., and mortar It is not preferable from the point which ensures fluidity, such as these. Therefore, in this case, strength expression becomes poor and cannot be used in the present invention.

In the clinker mixing condition, the results of the examination of the silicic acid ratio and the iron ratio will be described. No. 1 of Table 2 using the raw materials of Table 1 The CaO crystal grain size in the clinker obtained by changing the silicic acid ratio and iron ratio on the basis of the mixing condition of 4 and holding at a calcination temperature of 1500 ° C. for 20 minutes is shown in Table 3. That is, the silicic acid ratio is in the range of 2.0-4.0 and the iron ratio is in the range of 0.5-3.5, and as shown in Table 3, the CaO grain size is 14.3 ?? m or more, which satisfies the CaO grain size required by the present invention. The CaO grain size is 13 ?? m or more, preferably 13-30 ?? m, more preferably 13-20 ?? m.

TABLE 3

Effect of Silicate Ratio and Iron Ratio on Grain Size

Hydroponics 2.52.930.51.07 2.52.932.51.06 2.52.933.51.05 2.52.01.51.13 2.54.01.51.01 CaO grain size (?? m) 15.5 14.3 14.6 17.1 17.2

On the other hand, when the silicic acid ratio becomes around 1.0 and the Al ₂ O ₃ and Fe ₂ O ₃ components increase, the clinker melts, and the firing by rotary kiln or the like becomes difficult. Therefore, the silicic acid ratio is in the range of 2.0-4.0 and the iron ratio is in the range of 0.5-3.5, and more practically, the values of silicic acid ratio (before and after 2.7) and iron ratio (before and after 1.9) which are close to those of ordinary crude steel portland cement are adopted. desirable.

Sodium sulfate is as follows. As shown in FIG. 5 and FIG. 6, it is recognized that sodium sulfate has an effect of promoting hardening and increasing initial strength even with a cement composition containing no CaO crystal amount. 5 and 6, however, it is recognized that the greater the amount of CaO crystals in the cement composition, the greater the strength-promoting effect and the synergistic effect of CaO crystals and sodium sulfate on the promoting effect of the hydration reaction.

For Cement clinker of 5.1 wt% (No. 4 in Table 2), the amount of CaO crystal obtained under the firing conditions of heating temperature of 20 ℃ / min, maximum temperature of 1500 ℃ and maximum temperature holding time of firing clinker is 20 ℃ / min. The experiment was conducted to investigate how the addition amount to the pure cement component of sodium sulfate (content of clinker component minus CaO crystal amount and added dihydrate gypsum) affects the hardening of the cement, and the results are shown in FIG. 8.

As a result, the amount of sodium sulfate added was 0-7% by weight, and the mortar compressive strength (test body having a particle size of 1.5 cm and a height of 3.0 cm) after half day in 20 ° C humid air was increased up to 2% by weight. It can be seen that there is a tendency to decrease slightly.

In addition, the compressive strength of the same mortar after 1 day in humid air at 20 ° C. showed a decrease in strength at an amount of 1% by weight or more, and a content of about 7% by weight of the added mortar has almost the same compressive strength as that without sodium sulfate.

In other words, when a large amount of sodium sulfate is added, the curing promoting effect of the initial stage of about half day is recognized, but the subsequent increase in compressive strength is deteriorated. However, it can be said that the addition of 0.5-3% by weight of sodium sulfate in the mortar compressive strength after 1 day in 20 ° C humid air exerts a remarkable effect on promoting the hardening of cement.

On the other hand, when the alkali is mixed in a large amount, there is a concern that it will cause an alkali aggregate reaction. Therefore, in the present invention, the amount of sodium sulfate added is 0.5-3% by weight based on the pure cement component. In addition, although potassium sulfate was examined, the effect was slightly inferior to that of sodium sulfate in the curing promoting effect, but almost the same effect could be expected.

It is known that these alkali sulfates generally act as a hardening accelerator for cement, but in the present invention, it is considered that the hardening promoting effect acts synergistically by the hydration of CaO crystals.

Figure 9 shows the results of the exothermic test of the cement mortar. This figure shows that 1 part by weight of cement: 2 parts by weight of sand (less than 2.5 mm): 0.37 parts by weight of water: 0.01 parts by weight of water-reducing agent, and cement mortar (wherein the content of CaO crystals and sodium sulfate in the clinker is used as sand components). The same volume of sand was removed to obtain mortar mixture ③).

According to this, mortars containing CaO crystals exhibited a large temperature rise and peak peaks with respect to cement mortars containing no CaO crystals. However, when sodium sulfate was further added to cement mortars containing CaO crystals, the temperature peaks were faster. Appears.

Next, the powder diagram of the cement composition is demonstrated. The amount of CaO crystals obtained at firing conditions of a heating rate of 20 ° C./min, a maximum temperature of 1500 ° C., and a maximum temperature holding time of 20 minutes was converted into SO _{3 by} converting 2 gypsum into SO ₃ in a cement clinker of 5.1% by weight (No. 4 in Table 2). 1% by weight of sodium sulfate and 1% by weight based on the pure cement component were ground. Using this, the same mortar (mortar mixture ③) was made, which was subjected to a compressive strength test after 1 day in 20 ° C humid air. The result is shown in FIG.

In general, the compressive strength of mortar hardening body increases as the surface area of the grain ratio, which is an index of powder degree, increases to 3300 cm ² / g, which is the same as that of ordinary portland cement, and the difference is greater than about 3800 cm ² / g. As the cement composition of the present invention appears in this range. In addition, since grinding to 5500 cm ² / g or more entails economic difficulties, it is preferable that the surface ratio of the blain ratio of the cement composition of the present invention is 3800-5500 cm ² / g.

EXAMPLE

(Example 1)

Using the raw material shown in Table 1, the No. A small amount of water was kneaded into the clinker mixture powder of 4 to prepare a spherical pellet having a particle diameter of about 1 cm. The temperature was raised to 1500 ° C. at a temperature increase rate of 20 ° C. in an electric furnace for 1 minute, and the temperature was maintained for 20 minutes in that state, followed by quenching to room temperature. The cement clinker was crushed to 4580 cm ² / g by a grinder, and CaO crystals were quantified by chemical analysis (CAJS 1-01-1972). As a result, the amount of CaO crystals was 5.09 wt%. To the weight of the pure cement component except for the CaO crystal component in the clinker, 2 weight% of dihydrate stone powder was added in terms of SO ₃ , and 1 weight% of sodium sulfate anhydride was added to some of the cement components. The compressive strength of the mortar test specimen (1.5 cm in diameter and 3.0 cm in height) was measured in the moist air of the cement composition thus prepared for 0.5 days, 1 day, 3 days, 7 days and 28 days of material age.

The mortar is composed of 1 part by weight of cement, 2 parts by weight of sand (2.5 mm or less), 0.37 part by weight of water, and 0.01 part by weight of water reducing agent (Mighty 150), and the CaO crystal component is regarded as part of the cement (mortar mixture ①) and , CaO crystals and sodium sulfate were considered to be part of the sand (mortar mix ③) and tested. In addition, kneading was performed by hand dough. In addition, the same strength test was carried out for ordinary Portland cement commercially available for comparison. These results are shown in FIG.

As shown in FIG. 11, the cement composition obtained by the present invention exhibits remarkable strength at the initial stage of material age, and also exhibits superior strength compared to commercially available cement on the day of material age 28. In particular, when sodium sulfate is added, the strength is significantly higher than that in the case where no sodium sulfate is added.

(Example 2)

Of the cement composition described in Example 1, a mortar test body having a diameter of 5 cm and a height of 10 cm (a CaO crystal and sodium sulfate were regarded as a part of sand by using 1% by weight of sodium sulfate in advance and pulverized), and the volume thereof was removed from the sand. Formulation ③) The flow test for the water / cement ratio of the hardened | cured material and the compressive strength test (1 day of material age in 20 degreeC humid air) were done.

For comparison, a test of ordinary Portland mortar containing 6 wt% of light quicklime powder as a blend and 1 wt% of sodium sulfate was also performed. In addition, kneading was performed using the mortar mixer. The result is shown in FIG. As shown in Fig. 12, the cement mortar according to the present invention is excellent in fluidity and high in initial strength as opposed to mortar in which quicklime powder is added to ordinary cement mortar.

(Example 3)

The compressive strength test of the concrete was done using the cement composition described in Example 1. The mix of concrete was carried out as Table 4 below. This concrete obtained the required fluidity of 8 cm slump.

TABLE 4

The formulation of concrete

W / C (%) s / a (%) slump(%) Ad / C (%) Unit weight (kg / m ³ ) W ^{* 1} C S G Ad ^{* 2} Invention 38.0 43.5 8.0 1.35 148.9 424.5 825 1,107 5.40 Comparative product ^{* 3} 38.0 36.8 10.5 0.75 188 500 641 1,114 3.75

* 1 minus the water in the water reducing agent

* 2 Mighty 150 (flower king product, moisture 58.0%)

* 3 crude steel portland cement

The test body was produced as follows. (1) After pouring concrete of the compound shown in Table 4, it is demolded after being left in 20 ° C humid air until 1 day, and then cured in the same humid air, and the compressive strength at 1, 7 and 28 days of material age is measured. Obtained. ② After placing concrete of the same compound using the same cement composition, put it in the curing kiln immediately, and inject steam, increase the temperature to 60 ℃ in 1 hour, and perform simple curing (simple steam curing) to stop the steam supply. Fig. 13 shows the relationship between the material age and the compressive strength when demolding in the room after 4 hours of injecting water into the room.

In addition, in FIG. 13, as a comparative example, the strength of the concrete up to 24 hours (one day) was measured using the same simple steam curing process for concrete in which 100 kg / m ³ of unit cement amount was mixed using crude steel portland cement land. Indicates.

As shown in FIG. 13, it turns out that the concrete using the cement composition of this invention expresses high strength 30 Mpa or more in the short time of material age 4 hours after pouring, and improves the strength smoothly after that. In addition, in the concrete using the crude steel portland cement and having a unit cement amount of 100 kg / m ^3, the concrete using the cement composition of the present invention is superior in the initial strength even when the same simple curing is performed.

(Example 4)

The cementation composition of the present invention used in Example 3 was subjected to a restraint expansion test (A method) according to JIS A 201 (1995), ^whereby an amount of expansion of 156 x 10 ^-6 was expressed. Therefore, the cement composition in this invention can be said to be a new expansion cement.

Since the cement composition of the present invention is as described above, according to the present invention, it is possible to maintain the fluidity within a time that is sufficient for the molding of concrete products and the construction of the flowable concrete, while expressing the required strength early and dismantling the formwork. In addition, in the manufacture of concrete products, it is possible to express the shipping strength early without performing steam curing, and also to demould in a short time by slight steam curing, thereby increasing the rotation of the formwork.

In addition, according to the present invention, by integrating quicklime prepared by a separate process in advance as free lime in clinker plasticity without post-adding, it can be supplied in the same manner as in the manufacturing process of ordinary portland cement, and contributes greatly to the cement concrete industry. I think of doing.

Claims (3)

3CaO · SiO ₂ -Spacer-A super-rigid cement composition obtained by grinding a cement clinker containing CaO crystals as the main mineral composition together with two gypsum dihydrates, and the silicic acid ratio of the cement clinker is 2.0-. 5.0, iron ratio is 0.5-4.0, CaO grain size is 13 ?? m or more, CaO crystal is 3-10% by weight relative to the total amount of cement clinker, and cement powder is 3000-6000cm ² / Cement composition, characterized in that g. 3CaO · SiO ₂ -Spacer-Cement clinker made by adding two gypsum and alkali sulfate to a cement clinker whose CaO crystal is the main mineral composition. Cement clinker has a silicic acid ratio of 2.0-5.0 and an iron ratio of 0.5. -4.0, CaO grain size is 13 ?? m or more, CaO crystal amount is 3-10% by weight relative to the total amount of cement clinker, the cement powder is 3000-6000 cm ² / g of the specific surface area of the grain, and the amount of alkali sulfate added is cement Cement composition, characterized in that 0.5 to 3.0% by weight of anhydrous in terms of the content of the pure cement clinker and the added dihydrate gypsum except the amount of CaO crystal in the clinker. 3. The cement composition according to claim 2, wherein the alkali sulfate added to the cement clinker is sodium sulfate or potassium sulfate.