Cement composition comprising a low-temperature firing clinker

Abstract

Cement composition comprising low-firing temperature clinker The invention relates to a new cement composition having the same fresh properties as general cement clinkers and good early and medium- to long-term strength development characteristics. The cement composition comprises cement clinker fired at a relatively lower temperature and with an increased amount of waste. In the cement clinker, the total content of C3A and C4AF is greater than or equal to 22%, the content of C3S is greater than or equal to 60% according to Bogue formulas, and the iron modulus (IM = Al2O3 / Fe2O3) is less than or equal to 1.3. The cement composition has an SO3 content of 2.3 to 3.3% by mass relative to the total amount of cement clinker and gypsum. Figure for abstract: none

Description

Title of the invention: Cement composition comprising a low-temperature firing clinker Technical field

[0001] The present invention relates to a novel cement composition. More specifically, the present invention relates to a novel cement composition, comprising a cement clinker capable of being manufactured with firing at a lower temperature than general cement clinkers, and exhibiting a good strength development characteristic both in the initial period and in the medium and long term period. State of the art

[0002] The cement industry is a typical mass-production and mass-consumption industry and needs to save resources and energy. For example, the manufacture of general Portland cement clinker, the most mass-produced cement clinker, requires firing raw materials having predetermined chemical compositions at 1450 degrees Celsius to 1550 degrees Celsius; and firing is the most energy-consuming process. Therefore, reducing the firing temperature results in energy saving. In order to reduce the firing temperature of clinker, a cement clinker having an increased content of C4AF (4CaOAl2O3Fe2O3), one of the main mineral components of Portland cement clinker, was developed (Patent Document 1: JP 2012-224504A).

[0003] In the context of current global environmental problems, the efficient utilization of waste and various by-products has been an important issue. Due to the characteristics of the cement industry and cement manufacturing plants, waste and by-products can be safely and efficiently used as raw materials and fuels for the manufacture of cement clinkers. The waste and by-products generally have a high content of Al2O3. The above cement clinker with an increased amount of C4AF contains a greater amount of Al2O3 than usual Portland cement clinkers and is therefore suitable for the utilization of waste and by-products. In this respect, the cement clinker according to patent document 1 is superior.

[0004] When Portland cement clinkers are simply ground and mixed with water, they quickly begin to stiffen and lose their fluidity. This is because C3A, one of the main components of Portland cement, reacts rapidly with water and generates hydrates precipitating on the surface of the particles. In order to lengthen the rapid setting period, gypsum has been added, for example, during the process of finishing grinding. To the above Portland cement clinker having increased C4AF content is added gypsum at 2.0 ± 0.2% by reducing SO3 to adjust the setting period (e.g., Patent Document 1: JP 2012-224504A). State of the art documents

[0005] [Patent document 1] JP 2012-224504A Summary of the invention

[0006] The present invention relates to a cement composition comprising a cement clinker having a total C3A and C4AF content greater than or equal to 22%, a C3S content greater than or equal to 60%, both according to the Bogue formulae, and an iron modulus (LM. = Al2O3 / Fe2O3) less than or equal to 1.3, and gypsum, characterized in that the SO3 content is 2.3 to 3.3% by mass relative to the total amount of cement clinker and gypsum.

[0007] The composition may further comprise one or more of a group consisting of blast furnace slag, siliceous mixture, fly ash and limestone.

[0008] The cement composition may be characterized by an SO3 content of 2.3 to 2.7% by mass relative to the total amount of cement clinker and gypsum. Problem to be solved by the invention

[0009] The cement clinker according to Patent Document 1 can be fired at a relatively lower temperature and consumes a relatively higher amount of waste containing A12O3. However, compared with general Portland cements, Portland cement clinkers having a total amount of C3A and C4AF of about 20% or less, its medium and long-term strength is slightly lower at about 28 days. In addition, in order to shorten the construction cycle, it has been requested to improve the initial strength up to an age of about 7 days, corresponding to the removal of the formwork. Therefore, the cement composition, fired at a relatively lower temperature and having consumed a large amount of waste containing A12O3, must exhibit good strength development characteristics in the initial period and the medium and long-term periods. Ways to solve the problem

[0010] The present inventors have worked diligently to solve the above problem. From the above low-temperature fired cement clinker, the inventors have discovered a new cement composition having the same fresh properties as general cement clinkers and superior early and medium- and long-term strength development characteristics to general cement clinkers. Here, "fresh properties" refers to the fluidity of the mortar before hardening and the setting property of the cement. The setting property is evaluated specifically by the initial time until the take begins and the final time until the take is completed.

[0011] The cement composition according to the invention comprises a cement clinker having a total amount of C3A and C4AF greater than or equal to 22%, a C3S content greater than or equal to 60%, both according to the Bogue formulas, and an iron modulus (LM. = Al2O3 / Fe2O3) less than or equal to 1.3 and gypsum. The cement composition is characterized in that the SO3 content is 2.3 to 3.3% by mass relative to the total amount of cement clinker and gypsum. The SO3 content is adjustable by the SO3 content in the cement clinker itself and the gypsum content added to the cement clinker. Advantageous effects of the invention

[0012] The cement composition according to the present invention comprises cement clinker which can be manufactured by low-temperature firing and has absorbed a large amount of waste, has fresh properties equivalent to general Portland cements, and has a good early strength development characteristic and a medium and long-term strength development characteristic both equivalent to or superior to those of general Portland cements. Brief Description of the Drawing

[0013] [Fig.l] [Fig.l] shows a characteristic diagram representing the DX diagrams of the cement compositions of the embodiments and comparative examples. Means for carrying out the invention

[0014] The contents of C3A, C4AF, C3S and C2S in the present invention are determined by Bogue formulas. Bogue formulas have been used with different indices and moduli to calculate the approximate chemical composition of the main components of cement clinkers from analysis values ​​of the major chemical components and are well known in the art. For reference, the calculation of the mineral contents of cement clinker by Bogue formulas is described below. The unit for components such as CaO is mass%, and the unit for the contents of C3S, etc. is also mass%. In addition to the main components including CaO, SiO2, Al2O3 and Fe2O3, cement clinkers also contain small contents of MgO, K2O and other components, and Bogue formulas calculate without considering the small contents. As a result, the total content of C3S and C4AF is sometimes less than 100%.

[0015] C3S content = (4.07 x CaO) - (7.60 x SiO2) - (6.72 x A12O3) - (1.43 x Fe2O3)

[0016] C2S content = (2.87 x SiO2) - (0.754 x C3S)

[0017] C3A content = (2.65 x A12O3) - (1.69 x Fe2O3)

[0018] C4AF content = 3.04 x Fe2O3.

[0019] The iron modulus (IM) is calculated from the analysis values ​​of the major chemical components, as well as the hydraulic modulus (HM), silica modulus (SM), activity index (AI), and lime saturation degree (LSD). The iron modulus has been used for clinker manufacturing management, along with other moduli and indices, and is well known to those involved in the industry. For reference, the calculation of the iron modulus, etc., is described below. In the calculation of the iron modulus (IM), hydraulic modulus (HM), etc., the unit for components such as CaO is mass%.

[0020] Hydraulic modulus (HM) = CaO / (SiO2 + A12O3 + Fe2O3)

[0021] Silica modulus (SM) = SiO2 / (Al2O3 + Fe2O3)

[0022] Iron modulus (IM) = Al2O3 / Fe2O3

[0023] Activity index (AI) = SiO2 / Al2O3

[0024] Lime saturation degree (LSD) = CaO / (2.8 x SiO2 + 1.2 x A12O3 + 0.65 x Fe2O3).

[0025] The values ​​of “CaO”, “SiO2”, “A12O3” and “Fe2O3” in the formulas can be measured according to JIS R 5202 “Chemical Analysis of Portland Cement” and JIS R 5204 “X-ray Fluorescence Analysis of Cement”, etc.

[0026] In the cement clinker according to the invention, the total content of C3A and C4AF is greater than or equal to 22%. If the total content decreases below 22%, it becomes difficult to obtain cement clinker having good properties such as strength development characteristics with a relatively lower firing temperature. As described later, the C3S content of the cement clinker according to the invention is greater than or equal to 60%. Therefore, the total content of C3A and C4AF is limited to 40%. The total content of C3A and C4AF is preferably less than or equal to 28%, and more preferably less than or equal to 27%. In this specification, the unit for C2S, C3S, C3A and C4AF is mass%.

[0027] The C3S content is very important in the invention for the strength development characteristics of the cement composition (hereinafter simply referred to as "cement"). If the C3S content decreases below 60%, with the total content of C3A and C4AF, the C2S content, and the iron modulus, etc., within the specified range, good strength development characteristics cannot be obtained. It is preferable that the C3S content is 61% or more.

[0028] The C2S content is not particularly limited, but it is important for the fluidity and early strength development of the cement. When the content is 8% or more, the fluidity is good, and when it is 11% or less, a sufficient early strength development characteristic is obtained. For good fluidity and early strength development characteristic initial strength, the C2S content is preferably 8 to 10% and, in particular, 9 to 10%.

[0029] The cement clinker according to the invention must have an iron modulus (LM.) of up to 1.3. If the iron modulus exceeds 1.3, the cement clinker, satisfying the other requirements, does not have a sufficient strength development characteristic (more specifically, a mortar strength development characteristic, etc.). In addition, if the iron modulus exceeds 1.3, the period between the setting of the cement and the end of setting generally becomes too long, so the iron modulus must be less than or equal to 1.3. The more preferable range of the iron modulus is 1.0 to 1.3.

[0030] The hydraulic modulus and the silica modulus are not particularly limited. In order to obtain a good balance between the different physical properties, the hydraulic modulus is preferably 1.8 to 2.2, and is particularly preferably 1.9 to 2.1. The silica modulus is preferably 1.0 to 2.0, and is particularly preferably 1.1 to 1.7.

[0031] The methods for manufacturing the cement clinker according to the invention are not particularly limited. By preparing and mixing known cement raw materials (clinker) in a predetermined ratio and then firing them according to a known method (for example, in an SP kiln or an NSP kiln), the cement clinker according to the present invention is obtained.

[0032] The preparation and mixing of cement raw materials are carried out according to known methods. For example, the compositions of waste, by-products and other raw materials (such as limestone, quicklime, slaked lime, etc. as a source of CaO, silica sand, etc., as a source of SiO2, clay, etc., as a source of Al2O3, a source of iron, etc.) are measured in advance, the mixing ratio of the raw materials is calculated so that the composition of the cement clinker complies with the specified conditions, and then the raw materials are mixed in the mixing ratio.

[0033] The raw materials of the cement clinker according to the invention are those used in the manufacture of general Portland cement clinkers. It is preferable in the invention to use raw materials comprising waste and by-products.

[0034] It is preferable in the invention to use wastes and by-products for their effective use in the manufacture of cement clinker. Examples of usable wastes and by-products include: blast furnace slag, steel slag, non-ferrous metal slag, coal ash, sewage sludge, water purification sludge, papermaking sludge, earthmoving waste, spent molding sand, soot and dust, incinerated fly ash, molten fly ash, kiln dust, Portland cement manufacturing, wood chips, clay waste, slag, used tires, seashells, municipal waste and their incinerated ashes. Some of these materials are used both as a cement component and as a source of thermal energy.

[0035] The cement clinker according to the invention contains a relatively higher amount of C3A and C4AF comprising aluminum. Therefore, compared to general cement clinkers, larger amounts of waste and by-products having a high aluminum content can be used.

[0036] The cement clinker according to the invention is made into cement in the same way as general cement clinkers, by grinding it with gypsum, or by mixing gypsum with the ground cement clinker. The cement manufactured may be ordinary Portland cement, early strength Portland cement, very early strength Portland cement, etc. In addition, the cement clinker according to the invention may be used as a component of various blended cements and solidifiers such as soil solidifiers.

[0037] Dihydrated gypsum, hemihydrated gypsum, anhydrous gypsum, etc., can be used as the gypsum source without any particular restriction. They are known as a gypsum source suitable for cement manufacturing. According to the invention, gypsum is added such that the SO3 content in the total of the cement clinker and the added gypsum is 2.3 to 3.3 mass%. If the SO3 content therein is less than 2.3% or more than 3.3 mass%, the resulting strength development characteristic is poor. For example, in Comparative Example 1 (SO3 content of 2.17%) in Table 3, the compressive strength of the mortar on the first day is low. In Comparative Examples 2 and 3, where the SO3 content exceeds 3.3%, the compressive strength of the mortar is low in the initial period from the first to the seventh day, and the long-term compressive strength at the 28th day is also low.Preferably, the SO3 content should be 2.3% to 3.2%. From the strength development point of view, it is particularly desirable to have an SO3 content of 2.3% to 2.7%. Embodiment 1 in Table 3 (SO3 content: 2.54%) has a higher SO3 content than Comparative Example 1 but exhibits a higher compressive strength than Comparative Example 1, always from the first day 1 to the 28th day. In addition, Embodiment 1 always exhibits a higher mortar compressive strength than Embodiment 2 and Comparative Examples 2, 3 (all with an SO3 content above 2.7%). In other words, when the SO3 content is between 2.3 and 2.7% by mass, the mortar compressive strength is exceptionally high. In this specification, when a range is . indicated as 2.3 to 2.7% by mass, this means, for example, at least 2.3% by mass and at most 2.7% by mass.

[0038] The cement composition according to the invention may comprise one or more of limestone, fly ash, blast furnace slag and a siliceous material. In this case, the total content of limestone, blast furnace slag, fly ash and siliceous material is less than or equal to 10% of the total cement composition.

[0039] It is preferable that the fineness of the powder of the cement clinker, gypsum, limestone and other mixing materials is adjusted so that the cement composition has a Blaine specific surface area of ​​2800 to 4500 cm2 / g.

[0040] As for the grinding to prepare the fineness of the powder, known methods can be used without restriction. The cement clinker and the other components can be ground separately and then mixed, or the components can be mixed together and then ground. Ball mills, vertical mills, etc. can be used as grinders.

[0041] The cement composition according to the invention can be used as Portland cement, and in particular, a cement according to the JIS standard. Portland cement includes ordinary Portland cement, early strength Portland cement and very early strength Portland cement. In addition to Portland cement, it can also be used as a component of various blended cements and as a solidifier such as a soil solidifier. Embodiments

[0042] The present invention is described in more detail with reference to embodiments, but the present invention is not limited to such embodiments.

[0043] Industrial raw materials containing waste were mixed to obtain a general Portland cement clinker (Cl) and a cement clinker according to the invention (C2) after firing. Cement clinker Cl was fired at 1450 degrees Celsius and cement clinker C2 was fired at 1350 degrees Celsius. The firing temperatures, mineral compositions and moduli of the cement clinkers are shown in Table 1.

[0044] To the general cement clinker (Cl), gypsum equivalent to 2.2 mass% SO3 was added, then mixed and ground until a Blaine specific surface area of ​​3200+50 cm2 / g was obtained (reference example). Five types of cement compositions were manufactured by adding gypsum to the cement clinker (C2): one having an SO3 content of 2.0% (comparative example 1); 2.5% (embodiment 1), 3.0% (embodiment 2); 3.5% (comparative example 2); and 4.0% (comparative example 3). The chemical compositions of the cement compositions are shown in Table 2.

[0045] Cement clinkers were processed into cements as described above, the compressive strengths of the mortars at a specified age were measured to evaluate the strength development characteristics. To evaluate the fresh properties, the setting times of the cements and the fluidities of the mortar were measured. The results are shown in Table 3.

[0046] (1) Chemical compositions of raw materials, cement clinkers and Cement compositions: measured by X-ray fluorescence analysis according to JIS R 5204.

[0047] (2) Compressive strength of mortar: measured according to JIS R 5201.

[0048] (3) Cement setting time: measured according to JIS R 5201.

[0049] In Table 3, times such as 2:00 mean 2 hours and 0 minutes, and so on.

[0050] (4) Mortar spread: measured according to JIS R 5201.

[0051] [Tables 1] Cement clinker Fired at (°C) Mineral composition according to Bogue formulas (%) Clinker moduli and index C3S C2S C3A c4af C3A + c4af HMSMIM Cl 1450 61.5 12.3 9.7 8.9 18.6 2.19 2.42 1.88 C2 1350 61.4 11.0 7.2 15.9 23.1 2.05 1.77 1.15

[0052] [Tables2] Cement clinker Chemical composition of cement (%) SO3 SiO2 ai2o (Fe2O; CaO MgC Na2O k2o TiO2 p205 MnC SrO Cl Ref. 0.06 0.04 0.0 1 Emb C2 2.54 19, 41 5.78 5.15 62, 95 2.07 0.28 0.35 0.28 0.17 0.07 0.04 0.0 1 Emb Z !C2 3, 17 5.76. 5.15 62, 41 2.05 0.27 0.35 0.27 0.17 0.07 0.04 0.0 1 Com pl C2 2.17 19, 57 5.85 5.30 63, 13 2.09 0.27 0.30 70.70 0.04 0.0 1 Com p.2 C2 3.55 19.09 5.71 5.09 62, 18 2.03 0.27 0.34 0.27 0.17 0.07 0.04 0.0 1 Com p.3 C2 4.089 .0.565 88 2.01 0.26 0.34 0.26 0.17 0.07 0.04 0.0 1

[0053] [Tables3] SO3 content (%) Compressive strength of mortar (N / mm2) Setting time Spread of mortar (mm) 1st day 3rd day 7th day 28th day Initial Final Ref. 2.21 13.4 29.4 46.2 61.8 2h00 3hl5 160.4 Pack.l 2.54 16.4 34.5 46.3 65.5 lh45 3h35 174.2 Pack. 2 3.10 14.3 32.8 46.1 60.1 2h00 3h45 170.2 Comp.l 2.17 12.6 32.0 45.5 62.5 2h00 3h50 178.8 Comp.2 3.55 12.3 31.0 42.4 57.0 lh55 3h50 171.1 Comp.3 4.09 10.3 24.3 40.5 55.4 2h00 3h55 162.9

[0054] The reference example illustrates the results of an ordinary cement composition fired at a standard temperature. Therefore, the results of the embodiments and comparative examples are discussed with reference to the results of the reference example.

[0055] Embodiments 1 and 2, according to the present invention, have SO3 contents of 2.3 to 3.3% by mass. Embodiment 1 exhibited resistance to higher compression after the first day, the third day and the 28th day and a higher mortar spread than those of the reference example. The compressive strength after the 7th day was substantially the same between Embodiment 1 and the reference example. Embodiment 2 had a higher compressive strength after the first day and the third day and a higher mortar spread than those of the reference example. Embodiment 2 and the reference example had substantially the same compressive strength after the 7th day and the 28th day. Embodiments 1 and 2 met the required setting time for Portland cement.

[0056] Compared with the reference example, the spreading of the mortar of Comparative Examples 1 to 3 gave good results, the setting properties were also in accordance with the quality standards for ordinary Portland cement and the fresh properties were better than before. However, in Comparative Example 1 with the SO3 content less than 2.3%, the compressive strengths after the 1st day and the 7th day were lower than the reference example. In Comparative Example 2 with the SO3 content more than 3.3%, the compressive strengths after the 1st, 7th and 28th days were lower than those of the reference example. In Comparative Example 3 with an even higher SO3 content, the compressive strengths were still lower than the reference example.

[0057] When the SO3 content was 2.3-3.3 mass%, high mortar compressive strength was obtained at the initial age, and particularly high mortar compressive strength was obtained when the SO3 content was 2.3-2.7 mass%. The inventors hypothesized the following mechanism for this. Gypsum in the cement composition reacted with C3A and C4AF and water and produced calcium sulfoaluminate hydrates such as ettringite (3CaO • A12O3 • 3CaSO4 • 12H2O) and monosulfate (3CaO • A12O3 • CaSO4 • 12H2O). [Fig.l] shows the DX diagrams of Embodiments 1 and 2, and Comparative Examples 1 to 3, on the third day, in the range of 2 theta(0) = 9 to 10 degrees.

[0058] In Embodiments 1 and 2 and Comparative Examples 1 to 3, ettringite peaks were confirmed and the peak intensity increased as the SO3 content increased. On the other hand, monosulfate peaks were confirmed in Embodiments 1 and 2, as well as in Comparative Example 1. The monosulfate peak was particularly high in Embodiment 1. Thus, the SO3 content caused changes in the ettringite and monosulfate content in the calcium sulfoaluminate hydrates.

[0059] In Table 3, when the gypsum content increased from Comparative Example 1 to Comparative Example 3, the initial compressive strength of the mortar decreased. However, when the SO3 content was 2.3 to 3.3 mass%, the compressive strength increased exceptionally. The improvement in the compressive strength of the mortar was particularly marked when the SO3 content was 2.3 to 2.7 mass%. If we examine how the formation of calcium sulfoaluminate hydrates changed the strength development characteristic, when only ettringite was formed, the strength development characteristic was not high. On the contrary, when both ettringite and monosulfate were formed, the strength development characteristics improved.Moreover, when the SO3 content was 2.3–2.7 mass%, monosulfate was generated significantly, and therefore, the ratio of ettringite to monosulfate was suitable for the best strength development characteristic.

[0060] As described above, the cement composition according to the invention has no negative effect on fresh properties, compared to general Portland cement compositions, and has equivalent or better initial and medium and long-term strength development characteristics than general Portland cement compositions.

Claims

Claims

1. Cement composition comprising a cement clinker having a total C3A and C4AF content greater than or equal to 22%, a C3S content greater than or equal to 60%, both according to the Bogue formulas, and an iron modulus (LM. = Al2O3 / Fe2O3) less than or equal to 1.3, and gypsum, characterized in that the SO3 content is 2.3 to 3.3% by mass relative to the total amount of cement clinker and gypsum.

2. The cement composition of claim 1, further comprising one or more of a group consisting of blast furnace slag, siliceous mixture, fly ash and limestone.

3. Cement composition according to claim 1, characterized in that the SO3 content is 2.3 to 2.7% by mass relative to the total amount of cement clinker and gypsum.

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