Ternary low-calcium mineral-based high-activity auxiliary cementing material and preparation method thereof

Abstract

The invention relates to a ternary low-calcium mineral-based high-activity auxiliary cementing material and a preparation method thereof, and belongs to the technical field of building materials, the material is a # imgabs0 # ternary low-calcium mineral-based high-activity auxiliary cementing material, and is prepared by uniformly mixing calcium, siliceous and sulfur raw materials in proportion, and then sequentially carrying out high-temperature calcination, cooling, grinding and semi-dry carbonation. The 7-day activity index is greater than 80%, and the 28-day activity index is greater than 95%. All devices used in the preparation method are conventional equipment in the prior art, and the process is simple and convenient; the used raw materials are relatively common, so that the method is suitable for industrial production and has important significance on low carbon and energy conservation of the cement; the SCM prepared through carbonation not only reduces early hydration heat release of cement, but also contains a small amount of # imgabs 1 # to improve the early strength of the cement, and C2S hydration improves the middle and later strength of the cement; amorphous silica gel generated by carbonation can react with a cement hydration product Ca (OH) 2 to generate C-S-H, high-activity calcium carbonate and calcium sulfate are beneficial to formation and stabilization of ettringite, and the strength of cement is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials and relates to a highly active supplementary cementitious material (SCM), in particular to a Ternary low-calcium mineral-based high-activity SCM and preparation method thereof. Background Art

[0002] The cement industry is an important basic industry of my country's national economy, and silicate cement occupies the main part of the cement market. The content of alite in silicate clinker exceeds 60%, which requires the consumption of many high-quality mineral resources. The main raw materials for the preparation of silicate clinker, ore and clay, are non-renewable resources. At present, it takes 1.3 tons of limestone and 0.3 tons of clay to produce one ton of clinker in my country. The cement industry is highly dependent on non-renewable natural resources. Secondly, the drying, crushing, grinding and calcining of raw materials, the decomposition of raw calcium carbonate, the high-temperature calcination of clinker minerals (1450℃) and the ball milling with mixed materials in the cement preparation process not only consume a large amount of coal and electricity resources, but also emit a large amount of carbon dioxide. The cement industry is facing great pressure to save energy and reduce emissions. Under this circumstance, realizing green cement manufacturing is an effective way to achieve this goal.

[0003] One method to reduce cement usage and save cement preparation costs is to add SCM to cement, which can not only reduce cement hydration heat, regulate cement strength, but also improve the durability of cement and concrete. Common SCMs include natural volcanic ash, fly ash, silica fume, ground blast furnace slag, limestone powder, metakaolin, calcined clay, etc. However, the dosage of most low-activity SCMs in cement is very limited, such as low-calcium fly ash, limestone powder, etc. In particular, limestone powder does not participate in the hydration reaction in cement, but only plays a filling role. If the dosage is greater than 10%, the porosity of the cement matrix will increase and the strength will decrease significantly. For slag with a higher activity index, its dosage in cement can reach 50-70%. In the implementation of national mega-construction projects in some remote areas, such as the Qinghai-Tibet Railway, Ningxi Railway, western airports, tunnels and viaducts, due to the harsh climate, high-strength and high-durability composite cementitious materials are required to ensure the quality of the building, service life and reduce maintenance costs. Therefore, highly active SCM is indispensable. However, due to differences in regional environment, resource distribution and industrial structure adjustment, the output of highly active slag, silica fume, etc. has gradually decreased, prices have continued to rise, and regional distribution is uneven. Take slag as an example. It is mainly distributed in East China and North China, while the output of slag in Northeast, Northwest and Southwest China is very small, which means that a lot of transportation costs need to be invested. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a highly active SCM, namely, a Ternary low-calcium mineral-based high-activity SCM and its preparation method. The raw materials used in the present invention are relatively common and suitable for local collection. The amount and quality of the limestone used are lower than those of ordinary Portland cement clinker, and it can absorb industrial solid wastes such as phosphogypsum, reducing pollution to the environment. Secondly, the calcination temperature of low-calcium clinker is 200-350°C lower than that of silicate clinker, which reduces more coal consumption, and can absorb part of CO2 during the carbonation process. In addition, the clinker has a low calcination temperature and good grindability, which can save electricity consumption for clinker grinding. The high-activity auxiliary cementitious material (SCM) prepared by the carbonation of clinker in the present invention has a 28d activity index greater than 95%, which can replace mineral powder for the preparation of high-performance composite cementitious materials, and is of great significance for energy conservation and emission reduction in the cement industry.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A ternary low-calcium mineral-based high-activity auxiliary gelling material, the ternary low-calcium mineral-based high-activity auxiliary gelling material is The ternary low-calcium mineral-based high-activity auxiliary cementitious material is prepared by mixing calcium, silicon and sulfur raw materials in proportion, grinding the calcined low-calcium clinker and subjecting it to carbonation treatment.

[0007] A method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material, wherein firstly, calcium raw material, silicon raw material and sulfur raw material are used as reaction raw materials, mixed in proportion, and then calcined at high temperature, cooled, ground and semi-dry carbonated in sequence to obtain the material, wherein the 7-day activity index is greater than 80% and the 28-day activity index is greater than 95%. Specifically, the following steps are included:

[0008] S1. According to the designed clinker mineral composition, the raw materials are mixed to prepare the raw material, the calcination temperature is 1100-1250℃, the insulation time is 0.5-6h, and the rapid cooling is obtained. Ternary low calcium clinker, specifically dicalcium silicate (C2S)-calcium sulfosilicate -Calcium sulphoaluminate Polymeric system. In ternary low-calcium clinker, C2S accounts for 20-80wt%, Accounting for 10-60wt%, The proportion is 0-30wt%, and the rest is impurity phase.

[0009] May contain and One or two of them; C2S may contain β-C2S, α' L-C2S, γ-C2S, amorphous C2S or C2S solid solution; calcium carbonate may include one or more of calcite, aragonite, vaterite or amorphous calcium carbonate; gypsum may include one or both of dihydrate gypsum or hemihydrate gypsum; the amorphous phase includes one or more of amorphous silica gel, CSH gel and amorphous calcium carbonate.

[0010] S2. Prepared in S1 The ternary low calcium clinker is ground to a specific surface area between 300-400m 2 / kg, and then the ground powder is uniformly wetted with water at a liquid-to-solid ratio of 0.01-0.3 to obtain pretreated powder.

[0011] S3. Using 99% CO2 gas or industrial flue gas containing 10-50% CO2, the reaction time is 2-240min, and the pretreated powder obtained in S2 is carbonated and ground to obtain high-activity SCM, that is, ternary low-calcium mineral-based high-activity SCM.

[0012] Furthermore, in the S3, the SCM prepared by carbonation of the clinker contains C2S, Calcium carbonate, gypsum and amorphous phase; among them, The content is 10-60wt%, The content is 0-30wt%, the C2S content is 20-80wt%, the calcium carbonate content is 0-30wt%, the gypsum content is 0-20wt%, and the amorphous phase content is 0-40wt%.

[0013] Furthermore, in the S1, the preparation of low-calcium clinker effectively utilizes industrial solid waste, wherein: the calcium raw material is carbide slag or low-grade limestone, the silicon raw material is sandstone or clay or fly ash, and the sulfur raw material is fluorite or phosphogypsum or desulfurized gypsum. In parts by weight, the reaction raw materials contain the following components: 50-80 parts of carbide slag or low-grade limestone, 5-50 parts of sandstone or clay or fly ash, 5-30 parts of phosphogypsum or fluorite or desulfurized gypsum, and the total mass of all raw materials is 100 parts.

[0014] The raw materials used are mainly industrial solid waste, and CO2 in industrial flue gas can be fully utilized, which alleviates the accumulation of waste, realizes the resource utilization of waste, reduces the carbon emission of industrial flue gas, and prepares highly active SCM, reduces the amount of cement used, and has the advantages of low production cost, energy-saving and environmentally friendly preparation process, etc. The CaO content in the low-grade limestone or carbide slag is 40.0-70.0wt%, the SiO2 content in the sandstone, clay or fly ash is 30.0-80.0wt%, and the SO3 content in the fluorite, phosphogypsum or desulfurized gypsum is 40.0-50.0wt%.

[0015] Further preferably, in the S1, the raw material composition of the low-calcium clinker, calculated by weight, includes 60-75 parts of carbide slag or low-grade limestone, 5-25 parts of sandstone or clay or fly ash, 5-15 parts of phosphogypsum or fluorgypsum or desulfurized gypsum, and the total weight of all raw materials is 100 parts.

[0016] Furthermore, in S1, low-calcium clinker is obtained by rapid cooling, and the purpose of rapid cooling is to prevent the excessive generation of γ-C2S due to untimely cooling, which may cause the clinker hydration activity to decrease; the rapid cooling specifically refers to calcining and keeping the clinker warm for a corresponding period of time, quickly taking it out of the high-temperature furnace, and rapidly cooling it with a fan.

[0017] Furthermore, in S2: grinding the clinker to a specific surface area of ​​300-400m 2 / kg, the purpose is: the larger specific surface area can ensure that the clinker powder is fully in contact with CO2 gas, thereby improving the carbonation efficiency. In this step, the clinker calcination temperature is low, the grindability is good, and power consumption can be saved. In this step, the carbonation liquid-solid ratio is 0.01-0.3, which should not be too large or too small. Under a larger liquid-solid ratio, too much water blocks the CO2 gas molecule transmission channel, which is not conducive to carbonation. If the liquid-solid ratio is too small, the water necessary for the carbonation reaction cannot be guaranteed, causing the reaction to stagnate.

[0018] Furthermore, in said S1: the high temperature calcination of clinker, the calcination temperature is preferably 1150-1200°C, and the holding time is preferably 1-4h.

[0019] Furthermore, in S2: the specific surface area of ​​the clinker after grinding is preferably 350-400m 2 / kg, the liquid-to-solid ratio is preferably 0.05-0.2.

[0020] Furthermore, in S3: the carbonation treatment condition is to introduce 99% carbon dioxide or industrial flue gas with a carbon dioxide concentration of preferably 20%-30%, and the reaction time is preferably 5-120 min.

[0021] Furthermore, after the S3 carbonation treatment, the SCM needs to be dried and further ground to a specific surface area of ​​400-800m 2 / kg to release more silica gel wrapped by calcium carbonate and further improve the activity index of SCM. Further grinding is because the clinker powder will condense into fine particles after carbonation. The fine particles after carbonation have almost no strength and are easy to grind. Secondary grinding helps to further improve the activity index of SCM.

[0022] The devices used in the present invention for preparing the high-activity SCM are all conventional equipment in the prior art, the preparation process is simple and convenient, and is suitable for industrial production.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) In the present invention, ternary low-calcium clinker is prepared at low temperature using raw materials such as carbide slag, low-grade limestone, fly ash, sandstone, phosphogypsum, etc. The presence of not only reduces the amount of calcium raw materials, but also further reduces the clinker burning temperature, and highly absorbs industrial solid wastes such as phosphogypsum, alleviating the pollution to the environment. Carbonation treatment eliminates some of the free calcium oxide and free magnesium oxide remaining in the clinker, and at the same time prepares highly active SCM, which is of great significance for cement low-carbon energy conservation.

[0025] (2) Since the clinker is mainly composed of low-activity minerals, the early hydration heat of cement is effectively reduced. The lattice structure improves its later hydration activity; secondly, the carbonation product nano calcium carbonate particles act as nucleation sites to promote cement hydration, and the gypsum and calcium carbonate produced by the carbonation of clinker promote the formation and stability of calcium sulfonate; in addition, amorphous silica gel can react with cement hydration product Ca(OH)2 to generate CSH, which improves the strength of cement and is beneficial to the durability of cement. The specific analysis is as follows:

[0026] In the present invention, the low-calcium clinker prepared from industrial solid waste contains a small amount of Its rapid hydration improves the early strength of cement, and the slow hydration of C2S provides the mid- to late-stage strength of cement. This mineral has good carbonation activity. C2S and Carbonation produces amorphous silica gel, calcium carbonate and gypsum. Silica gel reacts with calcium hydroxide (Ca(OH)2) produced by cement hydration to produce CSH, which further increases the strength of cement paste. The consumption of Ca(OH)2 also accelerates the Ca in C2S. 2+ The leaching of aluminum ore in cement further accelerates its hydration rate. In addition, the gypsum generated by the reaction reacts with the cement hydration product calcium aluminate (C3AH6) to promote the formation of calcium sulfonate, thereby improving the strength and durability of cement. Hydration produces CSH and ettringite. Calcium-containing minerals The carbonation of C2S generates calcite, aragonite, vaterite and amorphous calcium carbonate, which can provide nucleation sites for cement hydration, promote the precipitation of Ca(OH)2 and CSH on its surface, and further accelerate hydration. Calcium carbonate reacts with C3A to generate CO3-AFm, which inhibits the conversion of ettringite to SO4-AFm, thereby stabilizing ettringite and improving cement strength and durability.

[0027] In the present invention, the prepared high-activity SCM is used to replace mineral powder and cement, which not only reduces the amount of cement used, saves high-quality ore resources, but also alleviates the excess cement production capacity.

[0028] In the present invention, the clinker calcined at high temperature and the product after carbonation have very good grindability, which not only saves power consumption, but also improves the carbonation efficiency, ensuring that the SCM prepared by carbonation has a higher activity index.

[0029] In the present invention, the early stage of clinker calcination emits a certain amount of CO2, and the clinker carbonation can absorb the CO2 in the industrial flue gas, thereby realizing carbon capture, utilization and storage, further reducing carbon emissions, and being beneficial to energy conservation and emission reduction. DETAILED DESCRIPTION

[0030] To further illustrate the purpose and technical solution of the present invention, specific embodiments are given below for further explanation.

[0031] The various raw materials, instruments and equipment used in the present invention are all commercially available products or can be prepared by existing methods. In the present invention, the silicate clinker used is from Dalian Cement Group Co., Ltd. In the present invention, parts by weight can be mg, g, kg and other weight units commonly used in the art, or multiples thereof, such as 10 times, 100 times, etc.

[0032] The following is specifically described by Examples 1-12:

[0033] In the present invention, the ingredients of the raw materials used are shown in Table 1.

[0034] Table 1 Analysis of raw material oxide groups (%)

[0035]

[0036]

[0037] Comparative Example 1

[0038] Raw material ratio: 63 parts of carbide slag, 25 parts of sandstone, 5.5 parts of fluorgypsum, and 6.5 parts of fly ash.

[0039] Preparation method:

[0040] S1. Dry the above raw materials in an oven at 100℃ for 24h, crush and grind the raw materials to a specific surface area between 200-300m 2 / kg, and weigh according to the proportion, put it in a steel tank, add water to cover the raw materials, place it in a planetary ball mill and stir for 20 minutes to fully mix, the speed is 30r / min. The mixed slurry is placed in an oven to dry the moisture, and about 5% of water is added to mix evenly, and then pressed into a Φ50mm×5mm round cake by a tablet press. The dried cake is placed in a high-temperature furnace for calcination, heated to 1000℃ at a heating rate of 10℃ / min, and then heated to 1200℃ at a rate of 5℃ / min, kept warm for 2h, and the clinker block is taken out and rapidly cooled to room temperature.

[0041] S2. Place the clinker block in a steel tank, set the planetary ball mill speed to 30r / min, and ball mill for 15 minutes until the material specific surface area reaches about 800m 2 / kg.

[0042] The ratio of the amount of calcium oxide in the clinker that reacts with CO2 to the total amount of calcium oxide in the clinker is recorded as the degree of carbonation. Taking the degree of carbonation as a variable, the 7d and 28d activity indexes of the prepared SCM were tested according to GB / T 18046-2017 "Granulated blast furnace slag powder for cement, mortar and concrete". The setting time of the cement prepared using the SCM was tested according to GB / T 1346-2011 "Test methods for water consumption, setting time and stability of cement standard consistency". The results are shown in Table 2.

[0043] The 7d activity index of SCM prepared by this method is 83.2%, and the 28d activity index is 92.1%.

[0044] Example 1

[0045] The raw material proportions of S1 and S2 are the same as those of Comparative Example 1.

[0046] S3. Mix the ground powder with water at a liquid-to-solid ratio of 0.1, and carbonate the pre-treated powder using industrial flue gas containing about 10% CO2 for 2 minutes. Then dry the carbonated powder and grind it again to a specific surface area of ​​about 800m 2 / kg.

[0047] The 7d activity index of SCM prepared by this method is 84.3%, and the 28d activity index is 97.6%.

[0048] Example 2

[0049] The raw material proportions of S1 and S2 are the same as those of Comparative Example 1.

[0050] S3. Mix the ground powder with water at a liquid-to-solid ratio of 0.1, and carbonate the pre-treated powder using industrial flue gas containing about 30% CO2 for 2 minutes. Then dry the carbonated powder and grind it again to a specific surface area of ​​about 800m 2 / kg.

[0051] The 7d activity index of SCM prepared by this method is 85.6%, and the 28d activity index is 98.5%.

[0052] Example 3

[0053] The raw material proportions of S1 and S2 are the same as those of Comparative Example 1.

[0054] S3. Mix the ground powder with water at a liquid-to-solid ratio of 0.1, and carbonate the pre-treated powder using industrial flue gas containing about 40% CO2 for 2 minutes. Then dry the carbonated powder and grind it again to a specific surface area of ​​about 800m 2 / kg.

[0055] The 7d activity index of SCM prepared by this method is 88.5%, and the 28d activity index is 101.2%.

[0056] Comparative Example 2

[0057] Raw material ratio: 64 parts of carbide slag, 21 parts of sandstone, 7 parts of fluorgypsum, and 8 parts of fly ash.

[0058] S1 and S2 are the same as those in comparative example 1, wherein the clinker calcination temperature is 1200°C and the temperature is kept for 1 hour.

[0059] The 7d activity index of SCM prepared by this method is 83.4%, and the 28d activity index is 91.7%.

[0060] Example 4

[0061] The raw material proportions of S1 and S2 are the same as those of Comparative Example 2.

[0062] S3. Mix the ground powder with water at a liquid-to-solid ratio of 0.2, and carbonate the pretreated powder using 99% CO2 gas for 5 minutes. Then dry the carbonated powder and grind it again to a specific surface area of ​​about 800m 2 / kg.

[0063] The 7d activity index of SCM prepared by this method is 90.8%, and the 28d activity index is 102.6%.

[0064] Example 5

[0065] The raw material proportions of S1 and S2 are the same as those of Comparative Example 2.

[0066] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.2, and the pre-treated powder is carbonated using 99% CO2 gas for 60 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0067] The 7d activity index of SCM prepared by this method is 97.6%, and the 28d activity index is 107.4%.

[0068] Example 6

[0069] The raw material proportions of S1 and S2 are the same as those of Comparative Example 2.

[0070] S3. The ground powder was evenly mixed with water at a liquid-to-solid ratio of 0.2, and the pre-treated powder was carbonated using 99% CO2 gas for 240 minutes. The carbonated powder was then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0071] The 7d activity index of SCM prepared by this method is 86.4%, and the 28d activity index is 98.2%.

[0072] Comparative Example 3

[0073] Raw material ratio: 66 parts of limestone, 18 parts of clay, 5 parts of fly ash, and 11 parts of desulfurized gypsum.

[0074] S1 and S2 are the same as comparative example 1, wherein the clinker calcination temperature is 1150°C and the temperature is kept for 4 hours.

[0075] The 7d activity index of SCM prepared by this method is 82.5%, and the 28d activity index is 90.3%.

[0076] Example 7

[0077] The raw material proportions of S1 and S2 are the same as those of Comparative Example 3.

[0078] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.01, and the pre-treated powder is carbonated using 99% CO2 gas for 60 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0079] The 7d activity index of SCM prepared by this method is 83.1%, and the 28d activity index is 95.3%.

[0080] Example 8

[0081] The raw material proportions of S1 and S2 are the same as those of Comparative Example 3.

[0082] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.05, and the pre-treated powder is carbonated using 99% CO2 gas for 60 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0083] The 7d activity index of SCM prepared by this method is 85.0%, and the 28d activity index is 101.4%.

[0084] Example 9

[0085] The raw material proportions of S1 and S2 are the same as those of Comparative Example 3.

[0086] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.1, and the pre-treated powder is carbonated using 99% CO2 gas for 60 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0087] The 7d activity index of SCM prepared by this method is 91.2%, and the 28d activity index is 104.3%.

[0088] Comparative Example 4

[0089] Raw material ratio: 55 parts limestone, 5.5 parts clay, 26.5 parts fly ash, 13 parts desulfurized gypsum

[0090] S1 and S2 are the same as comparative example 1, wherein the clinker calcination temperature is 1250°C and the temperature is kept for 6 hours.

[0091] The 7d activity index of SCM prepared by this method is 90.5%, and the 28d activity index is 98.6%.

[0092] Example 10

[0093] The raw material proportions of S1 and S2 are the same as those of Comparative Example 4.

[0094] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.1, and the pre-treated powder is carbonated using industrial flue gas containing about 30% CO2 for a reaction time of 240 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0095] The 7d activity index of SCM prepared by this method is 96.2%, and the 28d activity index is 105.2%.

[0096] Embodiment 11

[0097] The raw material proportions of S1 and S2 are the same as those of Comparative Example 4.

[0098] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.2, and the pre-treated powder is carbonated using industrial flue gas containing about 30% CO2 for a reaction time of 240 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m2 / kg.

[0099] The 7d activity index of SCM prepared by this method is 88.7%, and the 28d activity index is 101.5%.

[0100] Example 12

[0101] The raw material proportions of S1 and S2 are the same as those of Comparative Example 4.

[0102] S3. The ground powder is uniformly mixed with water at a liquid-to-solid ratio of 0.3, and the pre-treated powder is carbonated using industrial flue gas containing about 30% CO2 for a reaction time of 240 minutes. The carbonated powder is then dried and ground again to a specific surface area of ​​about 800m 2 / kg.

[0103] The 7d activity index of SCM prepared by this method is 94.5%, and the 28d activity index is 104.8%.

[0104] Table 2 Activity index of SCM at different carbonation degrees and setting time of the prepared cement

[0105]

[0106] Analysis and discussion:

[0107] As shown in Table 2, four different compositions of clinker were used for carbonation test. Carbonation was performed under different CO2 concentrations. As the CO2 concentration increased, the carbonation degree of the clinker gradually increased. Three-element low-calcium clinker, and The content is higher and the calcination temperature is lower. From the experimental results, as the carbonation time increases, the carbonation degree of the clinker gradually increases. The clinker used in Comparative Example 3 and the corresponding embodiments mainly consists of C2S and And within the range of lower liquid-to-solid ratio, as the liquid-to-solid ratio increases, the carbonation degree of the clinker gradually increases; while the comparative example 4 and the corresponding embodiments adopt Three-element low-calcium clinker, and The content is higher, the calcination temperature is higher, and the insulation time is longer. Therefore, the early hydration heat release of cement is higher than the other three, and the setting time is shorter, but with the increase of liquid-solid ratio, the carbonation degree of clinker increases first and then decreases.

[0108] Combined with the overall data analysis, the activity index of SCM shows a trend of increasing first and then decreasing with the increase of its carbonation degree. When the carbonation degree of clinker is 48.3%, SCM has the highest 7-day and 28-day activity indexes, which are 97.6% and 107.4% respectively. The heat release of silicate cement clinker hydration for 120h is about 280J / g. SCM significantly reduces the early hydration heat release of cement. Compared with uncarbonated SCM, moderately carbonated SCM accelerates cement hydration and slightly increases the hydration heat release. When the carbonation degree of clinker is low, the content of silica gel generated is small and insufficient to provide sufficient hydration activity. If the carbonation degree is too high, too much C2S and other minerals will be consumed, reducing the 28d activity of SCM. Secondly, the large calcium carbonate particles generated by excessive carbonation cover the surface of clinker minerals, hindering their further hydration, and also greatly reducing the filling effect of SCM materials on cement stone pores. Different degrees of carbonation determine the proportion of calcium carbonate, silica gel and C2S in low-carbon cementitious materials. For different clinker systems, the high activity index of SCM can only be guaranteed by seeking the appropriate carbonation degree. In addition, as the carbonation degree increases, the amount of gypsum produced by the reaction increases, which will correspondingly increase the initial and final setting time of cement.

[0109] The above description of the specific exemplary embodiments of the present invention is for illustration and illustration. These descriptions should not be construed as limiting the present invention to the precise form disclosed. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application. After reading the above description of the present invention, those skilled in the art may make several changes or modifications to the present invention without departing from the concept of the present invention, and these equivalent forms also fall within the scope defined by the claims attached to the present application.

Claims

1. A ternary low-calcium mineral-based high-activity auxiliary cementitious material, characterized in that: The ternary low-calcium mineral-based high-activity auxiliary gelling material is The ternary low-calcium mineral-based high-activity auxiliary cementitious material is prepared by mixing calcium, silicon and sulfur raw materials in proportion, grinding the calcined low-calcium clinker, and grinding it again after carbonation treatment.

2. A method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material, characterized in that: The preparation method firstly uses calcium raw material, silicon raw material and sulfur raw material as reaction raw materials, mixes them in proportion, and then sequentially performs high-temperature calcination, cooling, grinding and semi-dry carbonation to obtain the product, and includes the following steps: S1. According to the designed clinker mineral composition, the raw materials are mixed to prepare the raw material, the calcination temperature is 1100-1250℃, the insulation time is 0.5-6h, and the rapid cooling is obtained. Ternary low calcium clinker, of which C2S accounts for 20-80wt%, Accounting for 10-60wt%, It accounts for 0-30wt%, and the rest is impurity phase; S2. Prepared in S1 The ternary low calcium clinker is ground to a specific surface area between 300-400m 2 / kg, and then the ground powder is evenly wetted with water at a liquid-to-solid ratio of 0.01-0.3 to obtain a pretreated powder; S3. Carbonate the pre-treated powder obtained in S2 with CO2 gas or industrial flue gas with a CO2 concentration of 10-40% for 2-240 minutes. After carbonation, grind again until the specific surface area reaches 400-800m 2 / kg, releasing more silica gel wrapped by calcium carbonate, and obtaining a ternary low-calcium mineral-based high-activity SCM, whose 7-day activity index is greater than 80% and 28-day activity index is greater than 95%.

3. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 2, characterized in that: In the S1, the calcium raw material is carbide slag or low-grade limestone, the silicon raw material is sandstone or clay or fly ash, and the sulfur raw material is fluorite or phosphogypsum or desulfurized gypsum; in terms of weight parts, the reaction raw materials contain the following components: 50-80 parts of carbide slag or low-grade limestone, 5-50 parts of sandstone or clay or fly ash, 5-30 parts of phosphogypsum or fluorite or desulfurized gypsum, and the total mass of all raw materials is 100 parts.

4. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 3, characterized in that: In the S1, the CaO content in the low-grade limestone or carbide slag is 40.0-70.0wt%, the SiO2 content in the sandstone, clay or fly ash is 30.0-80.0wt%, and the SO3 content in the fluorite, phosphogypsum or desulfurized gypsum is 40.0-50.0wt%.

5. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 2, characterized in that: The S1 In ternary low calcium clinker, May contain and One or two of them; C2S may contain β-C2S, α' L -C2S, γ-C2S, amorphous C2S or C2S solid solution; calcium carbonate may include one or more of calcite, aragonite, vaterite or amorphous calcium carbonate; gypsum may include one or both of dihydrate gypsum or hemihydrate gypsum; the amorphous phase includes one or more of amorphous silica gel, CSH gel and amorphous calcium carbonate.

6. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 2, characterized in that: In the S3, the phases of SCM prepared by carbonation include C2S, Calcium carbonate, gypsum and amorphous phase; among them, The content is 10-60wt%, The content is 0-30wt%, the C2S content is 20-80wt%, the calcium carbonate content is 0-30wt%, the gypsum content is 0-20wt%, and the amorphous phase content is 0-40wt%.

7. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 3, characterized in that: In the S1, the raw material composition of the low-calcium clinker, by weight, includes carbide slag or low-grade limestone, preferably 60-75 parts, sandstone or clay or fly ash, preferably 5-25 parts, phosphogypsum or fluorgypsum or desulfurized gypsum, preferably 5-15 parts, and the total weight of all raw materials is 100 parts.

8. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 2, characterized in that: In S1, the calcination temperature of the high-temperature calcined clinker is preferably 1150-1200° C., and the insulation time is preferably 1-4 hours.

9. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 2, characterized in that: In S2, the specific surface area of ​​the clinker after grinding is preferably 350-400m 2 / kg, the liquid-to-solid ratio is preferably 0.05-0.

2.

10. The method for preparing a ternary low-calcium mineral-based high-activity auxiliary cementitious material according to claim 2, characterized in that: In the above S3: the carbonation treatment condition is to introduce carbon dioxide gas with a concentration of 99%, or industrial flue gas with a carbon dioxide concentration of 20-30%, and the reaction time is preferably 5-120 minutes.

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