Low-clinker cementing material, and preparation method therefor and use thereof

Abstract

Provided in the present disclosure are a low-clinker cementing material, and a preparation method therefor and the use thereof. The cementing material is formed by mixing a variety of raw materials, the variety of raw materials comprising, in percentage by mass on a dry basis, 30-50% of calcined high-iron bauxite tailings, 10-20% of dolomite, 35-45% of Portland cement clinker, and 4-6% of gypsum. The low-clinker cementing material prepared in the present disclosure can be used for preparing concrete according to the mixing proportion thereof in conventional C30-grade concrete; and all the mechanical properties of the prepared concrete can reach the grade C30, but the content of the Portland cement clinker is lower, which is conducive to carbon emission reduction in the cement industry. The raw materials in the present disclosure are green and low-carbon, have extremely high pozzolanic activity in a cementing material system, and can improve the mechanical properties and durability of the cementing material. The present disclosure achieves the efficient utilization of solid waste and bulk natural minerals that are easily available, and is free of direct emissions of CO2 during the process of processing, thereby being green, low-carbon and environmentally-friendly and having significant economic effects.

Description

Low-clinker cementitious material and its preparation method and application

[0001] Related applications

[0002] This disclosure claims priority to the Chinese patent application filed with the Patent Office of China on November 16, 2023, with application number CN202311537108.X and invention name “Low-clinker cementitious material and its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present disclosure relates to the technical field of cement concrete production, in particular to the field of low-clinker cementitious materials for concrete, and specifically to low-clinker cementitious materials and preparation methods and applications thereof. Background Art

[0004] General-purpose Portland cement is currently the largest and most widely used inorganic non-metallic cementing material in various construction projects. Design specifications for buildings and structures generally require the use of ordinary Portland cement or Portland cement with a P.O. 42.5 or higher grade in concrete mix design. However, according to GB 175, "General-purpose Portland Cement," the high-carbon-emitting Portland cement clinker ratio factor is excessively high for ordinary Portland cement with a P.O. 42.5 or higher grade (clinker + gypsum ≥ 80%) or Portland cement (clinker + gypsum ≥ 95%). Direct CO2 emissions from the Portland cement industry primarily arise from carbonate decomposition and coal combustion during Portland cement clinker production. Direct CO2 emissions from my country's cement industry account for over 13% of total societal CO2 emissions, placing immense pressure on the industry to reduce CO2 emissions. On the premise of ensuring that the total demand for cement supply for rapid economic and social development does not decrease, further reducing the amount of silicate cement clinker in concrete and further reducing the content of high-carbon emission silicate cement clinker in concrete are the most realistic and effective means to achieve the "carbon peak" goal of the building materials industry.

[0005] C30 grade concrete is currently the most widely used concrete grade in the concrete industry. Conventional mix designs typically utilize P.O42.5 grade ordinary Portland cement, along with either traditional fly ash or slag powder, either singly or in combination, to reduce costs and improve concrete properties. However, with the implementation of policies related to carbon peak in the building materials industry, the cement industry needs to reduce carbon emissions by lowering the clinker ratio in Portland cement. Furthermore, the concrete industry, while reducing the clinker ratio in cement, still hopes to use traditional fly ash and slag powder when using low-clinker cement.

[0006] Therefore, it is of great significance to design a preparation method and application of low-clinker cementitious materials for C30 grade concrete.

[0007] Summary of the Invention

[0008] The present disclosure aims to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of the present disclosure is to provide a low-clinker cementitious material for C30 grade concrete, a second objective is to reduce carbon emissions in the cement industry, and a third objective is to provide a method for preparing the low-clinker cementitious material.

[0009] To achieve the above-mentioned objectives, the present disclosure provides, on the one hand, a low-clinker cementitious material, which is formed by mixing a plurality of raw materials. The plurality of raw materials, calculated by dry weight percentage, include 30% to 50% of calcined high-iron bauxite tailings, 10% to 20% of dolomite, 35% to 45% of Portland cement clinker and 4% to 6% of gypsum.

[0010] Optionally, the activity index of the calcined high-iron bauxite tailings is ≥100%, wherein the total mass percentage of the three oxides Fe2O3, SiO2 and Al2O3 is ≥95%; and the mass percentage of Fe2O3 is >15% and <20%.

[0011] Alternatively, the calcined high-iron bauxite tailings are obtained by calcining at 700° C. to 800° C. for 0.5 h to 1.5 h and then rapidly cooling.

[0012] Optionally, the CaMg(CO3)2 grade of the dolomite is not less than 90%.

[0013] Optionally, the gypsum includes one or more of natural gypsum, phosphogypsum, desulfurized gypsum and titanium gypsum.

[0014] Another aspect of the present disclosure provides a method for preparing a low-clinker cementitious material, wherein the cementitious material is the above-mentioned cementitious material, and the method comprises the following steps:

[0015] Weigh various raw materials according to the dry mass percentage of the materials;

[0016] Spray the grinding aid into the raw materials weighed according to the proportion and grind them together;

[0017] After being ground to the required standards, the materials are discharged from the mill and stored to obtain low-clinker cementitious materials.

[0018] Optionally, the amount of the grinding aid is 0.5% to 1% of the total mass of the grinding raw material.

[0019] Alternatively, the grinding aid is made by mixing a plurality of raw materials, wherein the plurality of raw materials include, by mass percentage, 45% to 50% of calcium formate, 45% to 50% of naphthalene sulfonate water reducer and 3% to 5% of triethanolamine.

[0020] Alternatively, the standard conditions include: grinding the raw material to a particle size of 45 μm with a sieve residue of less than 20% and a specific surface area of ​​≥600 m 2 / kg.

[0021] Optionally, the 28-day compressive strength of the mortar of the low-clinker cementitious material is ≥42.5 MPa.

[0022] In another aspect, the present disclosure provides an application of a low-clinker cementitious material in C30 grade concrete, wherein the low-clinker cementitious material is prepared by the above method.

[0023] Alternatively, the dosage of the components of the C30 grade concrete includes: the dosage of cementitious materials of the C30 grade concrete is 310-340 kg / m 3 , low clinker cementitious material dosage 220~280kg / m 3 The total amount of fly ash and slag powder is 60-110kg / m 3 ; The cement clinker content in the concrete is ≤100kg / m 3 .

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1) The low-clinker cementitious material disclosed herein uses a large amount of low-carbon emission materials, and the high-carbon emission silicate cement clinker content in concrete is low, which can help reduce carbon emissions in the cement industry and increase the green and low-carbon properties of concrete, and has broad application prospects.

[0026] 2) In the process of calcining the bulk industrial solid waste high-iron bauxite tailings disclosed in the present invention, no carbonate decomposition produces carbon dioxide, and carbon-neutral alternative fuels or direct use of green electricity can be used, which is a green and low-carbon material; the calcined high-iron bauxite tailings contain amorphous aluminum oxide, silicon dioxide and iron oxide, and have extremely high volcanic ash activity in the cementitious material system.

[0027] 3) The raw material dolomite disclosed in the present invention is a natural mineral material with huge reserves and low price in my country. In the cementitious material system, it can react with calcium hydroxide and aluminum phase, the cement hydration product, and amorphous silica and aluminum oxide in calcined high-iron bauxite to produce carbon aluminate hydration products and layered double hydroxides (LDH), which can improve the mechanical properties and durability of the cementitious material.

[0028] 4) The present disclosure realizes the efficient utilization of solid waste and bulk natural readily available minerals; at the same time, the processing process does not directly emit CO2, and the green, low-carbon, environmental protection and economic effects are significant.

[0029] 5) The low-clinker cementitious material disclosed herein has high strength and low cement clinker content, and can be combined with traditional fly ash and slag powder to prepare C30 grade concrete. It is seamlessly connected with the traditional C30 grade concrete production process, and the amount of cement clinker in the concrete is further reduced, thereby reducing the CO2 load. DETAILED DESCRIPTION

[0030] Hereinafter, the low-clinker cementitious material disclosed herein and its preparation method and application will be described in detail with reference to exemplary embodiments.

[0031] Exemplary embodiment 1

[0032] This exemplary embodiment provides a low-clinker cementitious material, which is formed by mixing multiple raw materials. The raw materials, calculated by dry weight percentage, include 30% to 50% of calcined high-iron bauxite tailings, 10% to 20% of dolomite, 35% to 45% of Portland cement clinker, and 4% to 6% of gypsum. For example, the dry weight percentage of the calcined high-iron bauxite tailings may be 31%, 40%, 45%, or 49%, etc., the dry weight percentage of the dolomite may be 11%, 13%, 15%, or 19%, etc., the dry weight percentage of the Portland cement clinker may be 36%, 40%, or 44%, etc., and the dry weight percentage of the gypsum may be 4.5%, 5%, or 5.5%, etc.

[0033] The calcined high-iron bauxite has an activity of ≥100%. This means that when it replaces 30% of cement, the resulting cementitious material has mechanical properties comparable to or superior to pure cement. Therefore, it can replace at least 30% of the clinker in cement. However, increasing the content of calcined high-iron bauxite decreases the mixability of cement, so the maximum clinker replacement should not exceed 50%. The synergistic hydration effect of limestone and calcined clay has been widely reported, and calcined clay and limestone can produce a synergistic hydration effect. The combined addition of the two systems can maintain the mechanical properties of low-clinker cement.

[0034] This disclosure uses dolomite as a replacement for limestone, referencing the empirically optimized ratio of limestone to calcined clay, typically between 1:1 and 3. The calcium carbonate in the dolomite synergistically hydrates with the calcined clay and the aluminum phase in the cement clinker to form a carbonoaluminate hydration product. Furthermore, the MgCO₃ in the dolomite reacts with Ca(OH)₂ to form a hydrotalcite phase, which improves cement performance. Cement hydration in this system is relatively slow, and gypsum primarily serves as a stimulator for clinker hydration, while its setting-regulating effect is relatively weak, resulting in a relatively low addition level.

[0035] In this embodiment, the calcined high-iron bauxite tailings are calcined at 700°C to 800°C for 0.5h to 1.5h and then rapidly cooled to obtain the tailings. For example, the calcination temperature can be 701°C, 720°C, 780°C or 799°C, and the calcination time can be 0.6h, 1.2h or 1.4h. The mineral phase in high-iron bauxite is mainly kaolinite. Kaolinite minerals generally undergo dehydroxylation and decomposition between 550 and 650 degrees Celsius, and the products are amorphous silicon dioxide and aluminum oxide with high hydration activity. However, the degree of crystallization of kaolinite, the particle size of the raw materials, and the presence of impurity mineral phases will all lead to changes in the mineral decomposition temperature. Therefore, the calcination activation temperature is generally increased, and the high-temperature residence time is extended to ensure that the clay minerals can be fully decomposed and activated. Rapid cooling is mainly to avoid crystallization of the amorphous component during the cooling process, which reduces its activity.

[0036] According to the test method of GB / T2847 "Pozzolanic mixed materials for cement", the activity index of the calcined high-iron bauxite tailings is ≥100%, such as 100%, 105%, 110% or 115%, etc.; the total mass proportion of the three oxides Fe2O3, SiO2 and Al2O3 in the calcined high-iron bauxite tailings can be ≥95%, such as 95%, 98% or 99%, etc.; the mass percentage of Fe2O3 is >15% and <20%, such as 16%, 17% or 19%, etc. The higher the content of silicon dioxide and aluminum oxide in the calcined high-iron bauxite tailings, the better, indicating that the oxide components that can participate in cement hydration are high; the limitation of the ferric oxide content mainly limits the range of raw materials. Those with low ferric oxide content are no longer tailings, but will become other important industrial raw materials; the raw materials with high iron content disclosed in the present invention are difficult to be directly used in other fields.

[0037] In this embodiment, the CaMg(CO3)2 grade of the dolomite is not less than 90%, for example, 90%, 95%, or 99%. Dolomite is a natural ore, and mining often introduces soil and other components that are detrimental to cement performance; therefore, the primary mineral grade is limited. The gypsum includes one or more of natural gypsum, phosphogypsum, desulfurized gypsum, and titanium gypsum.

[0038] Exemplary embodiment 2

[0039] This exemplary embodiment provides a method for preparing a low-clinker cementitious material, wherein the low-clinker cementitious material is the cementitious material described in exemplary embodiment 1, and the method comprises the following steps:

[0040] S01: Weigh various raw materials according to the dry mass percentage of the materials.

[0041] In this embodiment, 30% to 50% of calcined high-iron bauxite tailings, 10% to 20% of dolomite, 35% to 45% of Portland cement clinker and 4% to 6% of gypsum are weighed and set aside, based on the dry mass percentage of the materials.

[0042] S02: Spray grinding aids to mix and grind the raw materials weighed according to the proportion.

[0043] In this embodiment, weighed raw materials are passed through an iron removal device and then transported to a powder system for mixing and grinding. During the grinding process, a grinding aid is sprayed in. The grinding aid is a mixture of multiple raw materials, which include, by weight, 45% to 50% calcium formate, 45% to 50% naphthalene sulfonate water reducer, and 3% to 5% triethanolamine. For example, the mass percentage of calcium formate can be 46%, 47% or 49%, the mass percentage of naphthalene sulfonate water reducer can be 46%, 48% or 49%, and the mass percentage of triethanolamine can be 3.5%, 4% or 4.9%. Calcium formate is a cement early strength agent. The early strength of the cement disclosed herein is too low, so calcium formate is added mainly to improve the early strength. Generally, when calcium formate accounts for 0.5% of the total cement volume, the cost performance is the highest. The cement disclosed herein has poor workability and high water demand, so naphthalene sulfonate water reducer is added to the grinding aid, which has a better dispersion effect on calcined activated clay minerals. Triethanolamine is the most important grinding aid in the field of cement grinding, and the general addition amount is less than 0.5‰, that is, less than 0.05%. The amount of the grinding aid used accounts for 0.5% to 1% of the total mass of the grinding raw materials.

[0044] S03: After grinding to meet the standards, the material is discharged from the mill and stored in the warehouse to produce low-clinker cementitious materials.

[0045] In this embodiment, the mixed grinding raw materials are ground to a 45 μm sieve residue of less than 20% and a specific surface area of ​​600 to 700 m 2 / kg after being discharged from the mill and stored in the warehouse to obtain low clinker cementitious materials. The above-mentioned sieve residue refers to the proportion of the sieve material. Generally, the 45μm sieve residue of cement is less than 20%, and the specific surface area is about 300-330m 2 / kg. The cement disclosed herein has high iron bauxite particles that retain the loose porous layered structure of kaolinite minerals, with a relatively high specific surface area. Dolomite is easy to grind and is easier to grind than cement clinker. Therefore, the particle size of this cement is not much different from that of conventional cement, but the specific surface area can generally be 600-700m 2 / kg. For example, the specific surface area of ​​the mixture after grinding can be 601m 2 / kg、620m 2 / kg or 699m 2 / kg, etc.

[0046] In this embodiment, the 28-day compressive strength of the prepared low-clinker cementitious material mortar is ≥42.5 MPa, such as 43.5 MPa, 45.3 MPa or 48.9 MPa.

[0047] Exemplary embodiment 3

[0048] This exemplary embodiment provides an application of a low-clinker cementitious material in C30 grade concrete.

[0049] The low-clinker cementitious material is prepared by the method described in Example 2. According to JGJ55 "Code for Design of Ordinary Concrete", the amount of the components of the C30 grade concrete includes: the amount of cementitious material per cubic meter of C30 grade concrete is 310-340 kg / m 3 , low clinker cementitious material dosage 220~280kg / m 3 The total amount of fly ash and slag powder is 60-110kg / m 3 For example, the cementitious material dosage of C30 grade concrete is 315kg / m 3 、330kg / m 3 or 335kg / m 3 The amount of low clinker cementitious material can be 221kg / m 3 , 245kg / m 3 , 260kg / m 3 or 279kg / m 3 etc. The total amount of fly ash and slag powder can be 61kg / m 3 , 70kg / m 3 , 90kg / m 3 or 109kg / m 3 The above ratios are calculated according to the standard method for concrete mix design. The cement clinker content in the concrete is ≤100kg / m 3 , for example 100kg / m 3 , 95kg / m 3 or 90kg / m 3 At the same time, the clinker content in the concrete must be guaranteed to be ≥90kg.

[0050] In order to better understand the above exemplary embodiments of the present disclosure, they are further described below with reference to specific examples.

[0051] Example 1

[0052] According to the dry weight percentage of the materials, 30% of calcined high-iron bauxite tailings, 20% of dolomite, 45% of silicate cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0053] Example 2

[0054] According to the dry weight percentage of the materials, 35% of calcined high-iron bauxite tailings, 15% of dolomite, 45% of Portland cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0055] Example 3

[0056] According to the dry weight percentage of the materials, 40% of calcined high-iron bauxite tailings, 10% of dolomite, 45% of Portland cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0057] Example 4

[0058] According to the dry weight percentage of the materials, 35% of calcined high-iron bauxite tailings, 20% of dolomite, 40% of silicate cement clinker and 5% of gypsum raw materials are weighed and transported to the grinding system for mixed grinding after passing through the iron removal device. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0059] Example 5

[0060] According to the dry weight percentage of the materials, 40% of calcined high-iron bauxite tailings, 15% of dolomite, 40% of Portland cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0061] Example 6

[0062] According to the dry weight percentage of the materials, 45% of calcined high-iron bauxite tailings, 10% of dolomite, 40% of Portland cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0063] Example 7

[0064] According to the dry weight percentage of the materials, 40% of calcined high-iron bauxite tailings, 20% of dolomite, 35% of Portland cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0065] Example 8

[0066] According to the dry weight percentage of the materials, 45% of calcined high-iron bauxite tailings, 15% of dolomite, 35% of silicate cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0067] Example 9

[0068] According to the dry weight percentage of the materials, 50% of calcined high-iron bauxite tailings, 10% of dolomite, 35% of Portland cement clinker and 5% of gypsum raw materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixed grinding. During the grinding, a grinding aid accounting for 1% of the weight of the raw materials entering the mill is sprayed. The materials are ground to a 45μm sieve residue of less than 20% and a specific surface area of ​​​​≥600m 2 / kg is then discharged from the mill and stored to produce low-clinker cementitious materials.

[0069] Comparative Example 1

[0070] P.O42.5R ordinary Portland cement (which meets the requirements of GB 175 "General Portland Cement") is used for comparison.

[0071] According to the dry mass percentage of the materials, 75% of Portland cement clinker, 5% of gypsum, 8% of limestone and 10% of other mixed materials are weighed; after passing through the iron removal device, they are transported to the grinding system for mixing and grinding. During the grinding, triethanolamine grinding aid accounting for 0.5‰ of the mass of the raw materials entering the mill is sprayed; the materials are ground to a specific surface area of ​​≥330m 2 / kg is then discharged from the mill and stored to produce P.O42.5R ordinary Portland cement.

[0072] Experimental example

[0073] The low-clinker cementitious materials prepared in Examples 1-9 and the P.O. 42.5R ordinary Portland cement prepared in Comparative Example 1 were subjected to raw material composition ratio and performance analysis. The raw material composition ratio data for the low-clinker cementitious materials prepared in Examples 1-9 and the P.O. 42.5R ordinary Portland cement prepared in Comparative Example 1 are shown in Table 1.

[0074] Table 1 Comparison of low clinker cementitious materials and comparative cement raw material ratios

[0075] It can be seen from the data in Table 1 above that the clinker content of the low-clinker cementitious material silicate cement prepared in the examples of the present disclosure is reduced by 30% to 40% compared with the P.O42.5R ordinary silicate cement prepared in Comparative Example 1.

[0076] The mortar fluidity and mechanical properties of the low-clinker cementitious materials prepared in Examples 1-9 and the P.O42.5R ordinary Portland cement prepared in Comparative Example 1 were analyzed, and the test results are shown in Table 2.

[0077] Table 2 Performance test results of low clinker cementitious materials and comparative cement

[0078] The data in Table 2 demonstrates that the low-clinker cementitious materials produced in Examples 1-9 exhibit lower 3-day mechanical properties, but exhibit significantly greater improvements in 28-day flexural and compressive strengths. The 28-day compressive strengths meet the compressive strength requirements of 42.5-grade general-purpose Portland cement. Compared to low-clinker cementitious materials for C30 concrete made with the same grade of P.O42.5R ordinary Portland cement, these materials significantly reduce the amount of cement clinker used while meeting the compressive strength requirements, significantly reducing CO2 emissions.

[0079] The cementitious materials or cements prepared in Examples 1-9 and Comparative Example 1 of the present disclosure were used to prepare C30 grade concrete to illustrate the effectiveness of the present disclosure. The sand, stone, water, and admixtures used in the examples and comparative examples were identical, all being commercially available conventional materials. The concrete mix ratios and preparation conditions were identical in the examples and comparative examples.

[0080] Application Example 1

[0081] According to JGJ 55 "Ordinary Concrete Design Code", C30 grade concrete was designed and prepared, with a total amount of cementitious materials of 330kg / m 3 , wherein: the amount of low clinker cementitious material prepared in Example 2 is 220kg / m 3 , in line with GB / T1596 "Fly ash used in cement and concrete" Class I fly ash 40kg / m 3 , in line with GB / T18046 "Granulated blast furnace slag powder for cement, mortar and concrete" S95 grade slag powder 70kg / m 3 The content of Portland cement clinker in the prepared C30 grade concrete is 99kg / m 3 .

[0082] Application Example 2

[0083] According to JGJ 55 "Ordinary Concrete Design Code", C30 grade concrete was designed and prepared, with a total amount of cementitious materials of 330kg / m 3 , wherein: the amount of low clinker cementitious material prepared in Example 5 is 250kg / m 3 , in line with GB / T1596 "Fly ash used in cement and concrete" Class I fly ash 30kg / m 3 , S95 grade slag powder 50kg / m3 in accordance with GB / T 18046 "Granulated blast furnace slag powder for cement, mortar and concrete" 3 The content of Portland cement clinker in the prepared C30 grade concrete is 100kg / m 3 .

[0084] Application Example 3

[0085] According to JGJ 55 "Ordinary Concrete Design Code", C30 grade concrete was designed and prepared, with a total amount of cementitious materials of 330kg / m 3 , wherein: Example 9 prepared low clinker cementitious material dosage 280kg / m 3 , in line with GB / T1596 "Fly ash used in cement and concrete" Class I fly ash 15kg / m 3 , in line with GB / T18046 "Granulated blast furnace slag powder for cement, mortar and concrete" S95 grade slag powder 35kg / m 3 The content of Portland cement clinker in the prepared C30 grade concrete is 98kg / m 3 .

[0086] Comparative Application Example 1

[0087] According to JGJ 55 "Ordinary Concrete Design Code", C30 grade concrete was designed and prepared, with a total amount of cementitious materials of 330kg / m3 , wherein: the amount of P.O42.5R ordinary Portland cement prepared in Comparative Example 1 is 220kg / m 3 , in line with GB / T1596 "Fly ash used in cement and concrete" Class I fly ash 40kg / m 3 , in line with GB / T18046 "Granulated blast furnace slag powder for cement, mortar and concrete" S95 grade slag powder 70kg / m 3 The content of Portland cement clinker in the prepared C30 grade concrete is 165kg / m 3 .

[0088] The mix proportions of the low-clinker cementitious material prepared in the examples of the present disclosure used in C30 grade concrete and the mechanical properties of the prepared concrete are listed in Table 3.

[0089] Table 3 Commercial concrete mix ratio and compressive strength

[0090] As can be seen from the data in Table 3, the low-clinker cementitious material disclosed herein can be used to prepare concrete together with traditional fly ash and slag powder according to the conventional C30 grade concrete mix ratio. The mechanical properties of the prepared concrete can reach the C30 grade, but the content of silicate cement clinker in the concrete is lower.

[0091] Although the present disclosure has been described above with reference to exemplary embodiments, it will be apparent to those skilled in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.

Claims

1. A low-clinker cementitious material, characterized in that: The cementitious material is mixed with a variety of raw materials, which include 30% to 50% of calcined high-iron bauxite tailings, 10% to 20% of dolomite, 35% to 45% of silicate cement clinker and 4% to 6% of gypsum in terms of dry basis weight percentage.

2. The cementitious material according to claim 1, characterized in that The activity index of the calcined high-iron bauxite tailings is ≥100%, wherein the total mass percentage of the three oxides Fe2O3, SiO2 and Al2O3 is ≥95%; the mass percentage of Fe2O3 is >15% and <20%.

3. The cementitious material according to claim 2, characterized in that The calcined high-iron bauxite tailings are obtained by calcining at 700° C. to 800° C. for 0.5 h to 1.5 h and then rapidly cooling.

4. The cementitious material according to claim 1, characterized in that The CaMg(CO3)2 grade of the dolomite is not less than 90%.

5. The cementitious material according to claim 1, characterized in that: The gypsum includes one or more of natural gypsum, phosphogypsum, desulfurized gypsum and titanium gypsum.

6. A method for preparing a low-clinker cementitious material, characterized in that: The gelling material is the gelling material according to any one of claims 1 to 5, and the method comprises the following steps: Weigh various raw materials according to the dry basis mass percentage of the materials; Spraying grinding aids to mix and grind the raw materials weighed according to the proportion; After being ground to the required standard, the material is discharged from the mill and stored in a warehouse to obtain low-clinker cementitious material.

7. The preparation method according to claim 6, characterized in that: The amount of the grinding aid is 0.5% to 1% of the total mass of the grinding raw material; The grinding aid is mixed with a variety of raw materials, which include, by mass percentage, 45% to 50% of calcium formate, 45% to 50% of naphthalene sulfonate water reducer and 3% to 5% of triethanolamine.

8. The preparation method according to claim 6, characterized in that: The compliance conditions include: grinding the raw material to a particle size of 45 μm with a sieve residue of less than 20% and a specific surface area of ​​≥ 600 m 2 / kg.

9. The preparation method according to claim 6, characterized in that: The 28-day compressive strength of the mortar of the low-clinker cementitious material is ≥42.5MPa.

10. Application of low-clinker cementitious material in C30 grade concrete, characterized in that: The low-clinker cementitious material is prepared by the method described in any one of claims 6 to 9; The dosage of the components of the C30 grade concrete includes: the dosage of cementitious materials of the C30 grade concrete is 310-340 kg / m 3 , low clinker cementitious material dosage 220~280kg / m 3 , the total amount of fly ash and slag powder is 60~110kg / m 3 ; The cement clinker content in the concrete is ≤100kg / m 3 .

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