Cement composition

Abstract

The present invention provides a cement composition which has fresh properties equivalent to those of conventional cement compositions and exhibits early strength development properties and medium to long term strength development properties equivalent to or better than those of conventional cement compositions in cases where a cement clinker, with which it is possible to lower the burning temperature during the production and to increase the amount of waste to be used in comparison to conventional cement clinkers, is used. This cement composition contains gypsum and a cement clinker that has a total amount of C3A and C4AF of 22% or more and a C3S amount of 60% or more as calculated by Bogue equations, and an iron ratio (I.M. = Al2O3 / Fe2O3) of 1.3 or less. The cement composition has an SO3 content of 2.3-3.3 mass% relative to the total amount of the cement clinker and gypsum.

Description

Cement composition

[0001] The present invention relates to a cement composition. More specifically, the present invention relates to a cement composition that uses cement clinker that can be fired at a lower temperature than conventional cement compositions, and that exhibits good strength development in the early stages and over the medium to long term.

[0002] The cement industry is a mass production and mass consumption industry, and resource and energy conservation are of utmost importance. For example, Portland cement, which is the most mass-produced cement, requires raw materials adjusted to a specific chemical composition to be burned at high temperatures of 1450 to 1550°C to produce clinker, and the burning process is the most energy-intensive process. In other words, if the burning temperature of clinker can be reduced, it will lead to energy savings. To reduce the burning temperature of clinker, it is necessary to reduce the amount of C, the main mineral in clinker. ４ AF(4CaO・Al ２ O ３ Fe ２ O ３ (Patent Document 1) Furthermore, in relation to recent global environmental issues, the effective use of waste and by-products has become an important issue. Taking advantage of the characteristics of the cement industry and cement manufacturing facilities, it is considered effective to use or treat waste as raw materials or fuel during cement manufacturing, from the viewpoint of safe and mass disposal. Waste and by-products contain Al ２ O ３ Many of them have a high content of C ４ In the system for increasing AF, the Al content of the cement clinker ２ O ３ Since the content is higher than that of conventional Portland cement clinker, it becomes possible to use more waste and by-products than with conventional Portland cement clinker. In this respect, the clinker described in Patent Document 1 is also superior.

[0003] On the other hand, when Portland cement clinker is simply crushed and mixed with water, it suddenly begins to harden and loses its fluidity. This is due to the fact that C, one of the Portland cement compounds, ３This is because A reacts rapidly with water, precipitating hydrates on the particle surface. In order to adjust this extremely fast setting time, gypsum is added during the finish grinding process to produce cement. ４ Even with Portland cement clinker with increased AF, the current practice is to adjust the setting time by adding gypsum to the clinker so that the amount of SO3 in the Portland cement is 2.0±0.2%, just as in the past (see, for example, Patent Document 1).

[0004] JP 2012-224504 A

[0005] The clinker described in Patent Document 1 can certainly be burned at a low temperature and ２ O ３ However, the amount of waste containing C that has been widely used up until now can be increased. ３ A and C ４ Compared to Portland cement clinker with a total AF content of 20% or less, the medium- to long-term strength of the material at an age of about 28 days tends to be slightly lower. Also, in order to shorten the construction cycle, it is required to improve the initial strength up to an age of about 7 days, which corresponds to the time when the formwork is removed. In other words, Al, which can be burned at low temperatures, ２ O ３ Even in cement compositions using clinker, which allows for the use of a large amount of waste material, there is a demand for cement compositions that exhibit good strength development in the early, mid- to long-term.

[0006] The present inventors have conducted extensive research to solve the above problems, and have discovered a cement composition using the above clinker that exhibits fresh properties equivalent to those of conventional cement compositions, and that is superior to conventional cement compositions in terms of early and medium- to long-term strength development, thereby completing the present invention. Note that "fresh performance" refers to the fluidity of the mortar before hardening and the setting properties of the cement, and can be evaluated specifically by the initial time until setting begins and the final time until setting is complete.

[0007] The present invention uses C calculated by the Borg method. ３ A and C ４ The total amount of AF is 22% or more, C ３ The S content is 60% or more, and the iron content (I.M. = Al ２ O３ / Fe ２ O ３ A cement composition containing cement clinker and gypsum, wherein the ratio of SO 2 to the total amount of the cement clinker and gypsum is 1.3 or less. ３ The cement composition contains 2.3 to 3.3 mass% of SO. ３ The content is the SO contained in the cement clinker. ３ The amount of gypsum added to the cement clinker is adjusted.

[0008] According to the present invention, even in the case of a cement composition using cement clinker that can be produced at a lower firing temperature and with a larger amount of waste material than conventional cement clinkers, the cement composition has fresh properties equivalent to those of conventional Portland cement and exhibits excellent early and medium- to long-term strength development that is equivalent to or better than that of conventional Portland cement.

[0009] 1 is a characteristic diagram showing XRD patterns of cement compositions of Examples and Comparative Examples.

[0010] C in the present invention ３ A, C ４ A.F., C. ３ S and C ２ The amount of S is determined by the Bogue formula.

[0011] The Bogue formula is used alongside coefficients and ratios to calculate the approximate composition of major compounds using major chemical analysis values, and is well known to those skilled in the art. However, just to be sure, the method for calculating the amount of each mineral in clinker using the Bogue formula is described below. The units of components such as CaO are in mass %, and C ３ The amount of S is also expressed in mass%. Clinker contains CaO, SiO ２ , Al ２ O ３ , Fe ２ O ３ In addition to the main components, MgO, K ２ The Borg formula does not take these minor components into account when calculating the C ３ S amount ~ C ４ The total amount of AF is 100% by mass or less. ３S amount = (4.07 x CaO) - (7.60 x SiO ２ ) - (6.72 × Al ２ O ３ ) - (1.43 × Fe ２ O ３ ) C ２ S amount = (2.87×SiO ２ ) - (0.754 x C ３ S) C ３ A amount = (2.65×Al ２ O ３ ) - (1.69 × Fe ２ O ３ ) C ４ AF amount = 3.04×Fe ２ O ３

[0012] The iron percentage (I.M.), along with the hydraulic percentage (H.M.), silica percentage (S.M.), activity index (A.I.), and lime saturation (LSD), is calculated using the values ​​of the main chemical components and is used as one of the number of times and ratios as a characteristic value for managing clinker production. It is a coefficient well known to those skilled in the art, but just to be sure, the calculation method for the iron percentage will be described below along with other coefficient values. In calculating the iron percentage (I.M.), hydraulic percentage (H.M.), etc., the units for components such as CaO are in mass %. Hydraulic percentage (H.M.) = CaO / (SiO ２ +Al ２ O ３ +Fe ２ O ３ ) Silicate ratio (S.M.) = SiO ２ / (Al ２ O ３ +Fe ２ O ３ ) Iron rate (I.M.) = Al ２ O ３ / Fe ２ O ３ Activity Coefficient (A.I.) = SiO ２ / Al ２ O ３ Lime saturation (L.S.D.) = CaO / (2.8×SiO ２ +1.2 x Al ２ O ３ +0.65×Fe ２ O ３) In addition, "CaO" and "SiO ２ ", "Al ２ O ３ " and "Fe ２ O ３ " can be measured by a method conforming to JIS R 5202 "Chemical analysis method for Portland cement" or JIS R 5204 "Fluorescence X-ray analysis method for cement", respectively.

[0013] As described above, in the cement clinker used in the present invention, C ３ A, C ４ The total amount of AF must be 22% or more. If the amount of these is less than 22%, it becomes difficult to obtain a cement clinker with good physical properties such as strength development by firing at a low temperature. As will be described later, the C of the cement clinker of the present invention ３ The amount of S is 60% or more. ３ A and C ４ The upper limit of the total amount of AF is 40%, preferably 28% or less, more preferably 27% or less. ２ S.C. ３ S.C. ３ A, C ４ The unit of AF is mass %.

[0014] C ３ The amount of S is extremely important for the strength development of the cement composition of the present invention (hereinafter simply referred to as "cement"). If this amount is less than 60%, ３ A and C ４ The total amount of AF and C ２ Even if the S content and iron content are within the specified ranges, good strength development cannot be obtained. ３ The S content is preferably 61% or more.

[0015] C ２ The amount of S is not particularly limited, but is important for the fluidity and early strength development of cement. If the amount is 8% or more, the fluidity will be good, and if it is 11% or less, sufficient early strength development will be obtained. From the viewpoint of fluidity and early strength development, more preferable C is ２ The range of the S content is 8 to 10%, and particularly preferably 9 to 10%.

[0016] The most important thing about the cement clinker used in the present invention is that the iron content (I.M.) is 1.3 or less. If the iron content exceeds 1.3, sufficient strength development (more specifically, mortar strength development, for example) cannot be obtained even if other requirements for the cement clinker used in the present invention are satisfied. Furthermore, if the iron content exceeds 1.3, the time from the start to the end of setting tends to become too long, and from this point of view as well, the iron content is set to 1.3 or less. A more preferable range of the iron content is 1.0 to 1.3.

[0017] The hydraulic ratio and silicic acid ratio are not particularly limited, but in order to obtain an excellent balance of various physical properties, the hydraulic ratio is preferably 1.8 to 2.2, particularly preferably 1.9 to 2.1, and the silicic acid ratio is preferably 1.0 to 2.0, particularly preferably 1.1 to 1.7.

[0018] The method for producing the cement clinker used in the present invention is not particularly limited, and the cement clinker can be easily obtained by preparing and mixing known cement (clinker) raw materials in predetermined proportions so as to achieve the above mineral ratios and coefficients, and then burning the mixture by a known method (for example, an SP kiln or an NSP kiln).

[0019] The cement raw materials may be prepared and mixed by any known method. For example, waste, by-products, and other raw materials (CaO sources such as limestone, quicklime, and slaked lime, SiO sources such as silica stone, etc.) may be mixed in advance. ２ Al from sources, clay, etc. ２ O ３ Fe source, iron source, etc. ２ O ３ The composition of the raw materials (sources, etc.) is measured, and the blending ratio of each raw material is calculated from the proportion of each component in these raw materials so that the blending ratio falls within the above range, and the raw materials are blended in that ratio.

[0020] The raw materials used in the production of the cement clinker used in the present invention are the same as those used in the production of conventional cement clinker, and are not particularly limited. Of course, waste materials, by-products, etc. can also be used.

[0021] In the production of the cement clinker used in the present invention, it is preferable to use one or more waste materials, by-products, etc., from the viewpoint of promoting the effective utilization of waste materials, by-products, etc. Specific examples of usable waste materials and by-products include blast furnace slag, steelmaking slag, non-ferrous slag, coal ash, sewage sludge, water purification sludge, papermaking sludge, construction waste soil, foundry sand, soot and dust, incineration fly ash, molten fly ash, chlorine bypass dust, wood chips, waste clay, slag, waste tires, shells, municipal waste and its incineration ash (some of these can be used as both a cement raw material and a thermal energy source).

[0022] In particular, the cement clinker used in the present invention is C ３ A and C ４ It contains a large amount of AF, a mineral whose constituent element is aluminum. Therefore, compared to conventional cement clinker, it has the advantage of being able to be produced using more waste and by-products that are high in aluminum.

[0023] The cement clinker used in the present invention can be prepared into cement by grinding it together with gypsum or grinding it separately and then mixing it, just like conventionally known cement clinkers. Examples of such cement include ordinary Portland cement, high-early-strength Portland cement, and ultra-high-early-strength Portland cement. In addition to being used as Portland cement, it can also be used as a component of various blended cements and solidifying materials such as soil solidifying materials.

[0024] Regarding the gypsum to be used, any known gypsum as a raw material for cement production, such as gypsum dihydrate, gypsum hemihydrate, anhydrous gypsum, etc., can be used without any particular limitation. For the cement clinker used in the present invention, SO 2 is used based on the total amount of the cement clinker and gypsum. ３ Gypsum is added so that the amount is 2.3 to 3.3% by mass. ３ When the amount is less than 2.3 mass % or more than 3.3 mass %, the strength development is poor. ３ When the amount was 2.17% by mass, the mortar compressive strength on the first day was low. ３In Comparative Examples 2 and 3, where the amount exceeds 3.3 mass%, the initial compressive strength of the mortar is low from day 1 to day 7, and the long-term compressive strength of the mortar is also low on day 28. ３ The amount is set to 2.3 mass % to 3.2 mass %. ３ The amount is preferably 2.3 to 2.7 mass %. ３ Amount: 2.54% by mass) is higher than that of Comparative Example 1. ３ Although the amount is large, the mortar compressive strength is high at all times from the 1st day to the 28th day. ３ The mortar compressive strength was higher at all time points than in Example 2 and Comparative Examples 2 and 3, where the amount exceeded 2.7% by mass. ３ At an amount of 2.3 to 2.7 mass%, the mortar compressive strength becomes exceptionally large. In this specification, when a range such as 2.3 to 2.7 mass% is indicated, it means 2.3 mass% or more and 2.7 mass% or less.

[0025] The cement composition of the present invention may contain, in addition to limestone, fly ash and / or blast furnace slag and / or siliceous admixture, in which case the total amount of limestone and blast furnace slag and the fly ash and / or siliceous admixture is 10 mass% or less of the total composition.

[0026] The above cement clinker, gypsum and other admixtures have a fineness of 2800 to 4500 cm in terms of Blaine specific surface area. ２ It is preferable that the molecular weight is adjusted to be / g.

[0027] The pulverization method for preparing the powder to the desired fineness can be any known technique without particular limitation, and the components can be pulverized separately and then mixed, or can be mixed and then pulverized. As the pulverizer, a ball mill, a vertical mill, etc. can be used.

[0028] The cement composition of the present invention can be used as a Portland cement slurry, particularly Portland cement conforming to JIS standards. Examples of such Portland cement include ordinary Portland cement, high-early-strength Portland cement, and ultra-high-early-strength Portland cement. In addition to being used as Portland cement, the composition can also be used as a component of various blended cements and solidifying materials such as soil solidifying materials.

[0029] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0030] Industrial raw materials including waste were used to prepare conventional cement clinker (C1) and cement clinker (C2) for use in the present invention on a burned basis, and the raw materials were burned at 1450°C and 1350°C, respectively, to obtain cement clinker. The burning temperatures during burning, and the mineral composition and coefficient values ​​according to the Bogue formula of the clinker obtained after burning are shown in Table 1.

[0031] Conventional cement clinker (C1) is SO ３ Gypsum was added so that the conversion was 2.2 mass %, and the specific surface area measured by the Blaine method was 3200 ± 50 cm ２ The cement clinker (C2) was mixed and ground to a concentration of 0.01g / g to produce a cement composition (Reference Example). ３ Five types of cement compositions were produced by adding gypsum to the cement in an amount equivalent to 2.0 mass% (Comparative Example 1), 2.5 mass% (Example 1), 3.0 mass% (Example 2), 3.5 mass% (Comparative Example 2), and 4.0 mass% (Comparative Example 3). The chemical compositions of the resulting cement compositions are shown in Table 2.

[0032] After the cement clinker was made into cement using the above method, the mortar compressive strength at a specified age was measured to determine strength development, and the cement setting time and mortar flow were measured to determine fresh properties, using the methods described below. The results of each measurement item are shown in Table 3. (1) Measurement of the chemical composition of raw materials, cement clinker, and cement composition: Measured using fluorescent X-ray analysis in accordance with JIS R 5204. (2) Measurement of mortar compressive strength: Measured using a method in accordance with JIS R 5201. (3) Cement setting time: Measured using a method in accordance with JIS R 5201. Times such as 2:00 mean 2 hours and 0 minutes, etc. (4) Measurement of mortar flow: Measured using a method in accordance with JIS R 5201.

[0033]

[0034]

[0035]

[0036] The Reference Example shows the results of firing a conventional cement clinker of a standard composition at a standard temperature. In other words, the results of each Example and Comparative Example will be discussed based on the results of this Reference Example.

[0037] Examples 1 and 2 are SO ３ The content is 2.3 to 3.3 mass% according to the present invention, and Example 1 is superior to the Reference Example in compressive strength and mortar flow after 1, 3, and 28 days, and the compressive strength after 7 days is equivalent to the Reference Example. Example 2 is superior to the Reference Example in compressive strength and mortar flow after 1 and 3 days, and the compressive strength after 7 and 28 days is equivalent to the Reference Example. The setting time also met the quality standards for Portland cement.

[0038] On the other hand, in Comparative Examples 1 to 3, the mortar flow showed good results compared to the Reference Example, the setting also met the quality standards of ordinary Portland cement, and the fresh properties were better than those of conventional cement. ３ Comparative Example 1, in which the content is less than 2.3% by mass, is inferior to the Reference Example in compressive strength after 1 and 7 days. ３Comparative Example 2, in which the content was more than 3.3% by mass, was inferior to the Reference Example in compressive strength after 1, 7 and 28 days. ３ Comparative Example 3, which contains an even larger amount, is inferior to the Reference Example in compressive strength after 1 to 28 days.

[0039] SO ３ The inventors have assumed that the mechanism by which a high mortar compressive strength is obtained at an early age when the content is 2.3 to 3.3 mass%, and an especially high mortar compressive strength is obtained when the content is 2.3 to 2.7 mass%, is as follows. ３ A, C ４ AF reacts with water to form ettringite (3CaO·Al ２ O ３ 3CaSO ４ ・12H ２ O), monosulfate (3CaO.Al ２ O ３ CaSO ４ ・12H ２ 1 shows the XRD patterns of Examples 1 and 2 and Comparative Examples 1 to 3 at an age of 3 days in the region of 2θ=9 to 10°.

[0040] In Examples 1 and 2 and Comparative Examples 1 to 3, ettringite peaks were confirmed, and SO ３ As the content increases, the peak intensity of ettringite increases. On the other hand, monosulfate peaks are also observed in Examples 1 and 2 and Comparative Example 1, and the monosulfate peak intensity is particularly large in Example 1. That is, ３ The ratio of ettringite and monosulfate produced in calcium sulfoaluminate hydrate changes depending on the content.

[0041] In Table 3, when the gypsum content was increased from Comparative Example 1 to Comparative Example 3, the compressive strength of the mortar at the early age decreased. ３ The compressive strength exceptionally improves in the range of 2.3 to 3.3 mass%, and the improvement in the compressive strength of the mortar is particularly remarkable in the SO ３The content was in the range of 2.3 to 2.7 mass%. Consider the effect of calcium sulfoaluminate hydrate formation on strength development. SO ３ In the range of the content, the strength development was not high. On the other hand, SO ３ In the range of SO ３ It is estimated that the ratio of ettringite to monosulfate produced in the range of 2.3 to 2.7 mass % content was particularly suitable for improving strength development compared to other ranges.

[0042] From the above, it can be confirmed that the cement composition of the present invention does not adversely affect the fresh properties as compared with conventional cement compositions, and has the effect of improving the initial and medium- to long-term strength development to the same or greater extent than conventional cement compositions.

Claims

1. C calculated by the Bogue formula ３ A and C ４ The total amount of AF is 22% or more, and the C ３ S amount is 60% or more, and the iron ratio (I.M. = Al ２ O ３ / Fe ２ O ３ ) is 1.3 or less, and a cement composition containing cement clinker and gypsum, wherein the SO ３ content is 2.3 to 3.3% by mass based on the total amount of cement clinker and gypsum.

2. The cement composition according to claim 1, further comprising at least one admixture selected from the group consisting of blast furnace slag, siliceous admixture, fly ash, and limestone.

3. The SO content is 2.3 to 2.7% by mass based on the total amount of cement clinker and gypsum. ３ The cement composition according to claim 1, wherein the SO content is 2.3 to 2.7% by mass based on the total amount of cement clinker and gypsum.

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