Solid waste-based delayed coagulation micro-expansive cement and preparation method thereof

Abstract

The invention provides solid waste-based delayed coagulation micro-expansive cement and a preparation method thereof, and belongs to the technical field of building materials. The solid waste-based delayed coagulation micro-expansive cement is prepared from the following raw materials in percentage by mass: 40%-50% of Portland cement clinker, 0.04%-0.06% of a delayed coagulation type grinding aid, 8%-12% of high-calcium steel slag, 10%-16% of slag, 8%-16% of fly ash, 8%-12% of modified phosphogypsum and 8%-12% of calcium-containing powder, wherein a preparation method of the modified phosphogypsum comprises the following steps: uniformly mixing phosphogypsum with phosphorus tailings subjected to high-temperature calcination, and storing for 10-30 days to obtain a mixture; and mixing the mixture with high-calcium steel slag, grinding, and drying to obtain the modified phosphogypsum. The solid waste-based delayed coagulation micro-expansive cement has the advantages of stable delayed coagulation effect, shrinkage compensation effect, continuous increase of later strength and the like; wherein the initial setting time of the solid waste-based delayed coagulation micro-expansive cement is 350 to 380 minutes, and the final setting time of the solid waste-based delayed coagulation micro-expansive cement is 420 to 460 minutes; 28-day compressive strength is greater than or equal to 45 MPa; the 28-day dry shrinkage rate is less than or equal to 0.09%; and the 28-day linear expansion rate is less than or equal to 0.5%.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a solid waste-based retarding and slightly expanding cement and a preparation method thereof. Background Art

[0002] In recent years, the construction of modern expressways in China has developed rapidly. In the pavement structure of expressways, the base course is the structural layer directly under the surface course, mainly playing the roles of bearing weight and spreading load stress. The quality of the pavement base course materials directly affects the quality and service performance of the pavement. Cement-based stabilized base courses are widely used in highway construction due to their advantages such as high strength, good water stability, and good frost resistance. However, the existing cement-based stabilized base courses have a large dry shrinkage coefficient, and the paved base courses are prone to cracking. Once the base course cracks, it will be reflected to the pavement, causing pavement cracking and damage. During the pavement construction process, repairing and reworking the cracked base course requires a large amount of manpower and material resources, resulting in huge losses. So far, the cracking problem of cement stabilized base courses has not been effectively solved. A large number of studies have found that cement is the main factor affecting the cracking of cement stabilized base course materials, and the cracking intensifies with the increase of the cement content. If the content is too low, the strength will be too low, and it is easily damaged after rolling. On the other hand, to meet the construction time requirements of cement stabilized base courses, the initial setting time of cement needs to be more than 6 h.

[0003] General silicate cement has large shrinkage and is extremely prone to shrinkage when used in road bases, which will further cause reflective cracks on the pavement, resulting in pavement damage. At the same time, due to the too fast setting time of ordinary cement, the cement adaptability becomes poor, the slump loss of concrete is large, and the fluidity is quickly lost, causing difficulties in construction. Moreover, the premature setting causes strength loss during the rolling and forming of the base course, resulting in a short delay rolling time for cement stabilized materials, having an adverse impact on construction management and affecting the pavement construction quality. In order to meet the requirements of delayed forming during road base construction and compensating for the cracks caused by dry shrinkage, the cement used for road bases must have a long setting time and slightly expanding properties. According to this characteristic, in addition to meeting the conventional indexes such as fineness, strength, and soundness, the cement used for road bases also has special requirements for setting time, slight expansibility, anti-shrinkage, and anti-cracking properties.

[0004] To sum up, in order to solve the above problems, the present invention provides a cement with retarding and slightly expanding properties and a preparation method thereof. Summary of the Invention

[0005] Aiming at the above deficiencies of the prior art, the present invention provides a solid waste-based retarding and slightly expanding cement and a preparation method thereof. The retarding and slightly expanding cement not only meets the conventional indexes of general cement, but also has retarding and slightly expanding properties, anti-shrinkage and anti-cracking properties and stable quality. In addition, the present invention makes full use of industrial solid waste, improving the environmental quality while reducing the production cost.

[0006] To achieve the above object, the specific technical solution of the present invention is as follows:

[0007] A solid waste-based retarding and slightly expanding cement, the raw materials of which are calculated by mass percentage, including: 8% - 10% of calcium-containing powder; 40% - 50% of portland cement clinker, 0.04% - 0.06% of retarding grinding aid, 8% - 12% of high-calcium steel slag, 10% - 16% of slag, 8% - 16% of fly ash, 8% - 12% of modified phosphogypsum, 8% - 12% of calcium-containing powder;

[0008] Among them, the preparation method of the modified phosphogypsum includes the following steps: mixing phosphogypsum with phosphorus tailings after high-temperature calcination evenly, storing for 10 - 30 days to obtain a mixture; mixing the mixture with high-calcium steel slag for grinding and drying to obtain modified phosphogypsum.

[0009] Furthermore, the residue on 200 µm sieve of the modified phosphogypsum does not exceed 6%, the free moisture does not exceed 2%, the pH value is controlled at 8 - 12, and the extension value of the setting time (compared with natural gypsum) is controlled at 60 - 90 min.

[0010] The present invention uses raw materials including calcium-containing raw materials, aluminosilicate raw materials, iron-containing raw materials and auxiliary materials to make portland cement clinker; uses industrial solid wastes - phosphorus tailings and high-calcium steel slag to modify phosphogypsum, and compound the modified phosphogypsum with portland cement clinker, fly ash, high-calcium steel slag, slag, calcium-containing powder and retarding grinding aid to prepare solid waste-based retarding and slightly expanding cement. The synergistic effect of each component makes the prepared solid waste-based retarding and slightly expanding cement have the advantages of stable retarding effect, compensation for shrinkage, continuous growth of later strength, etc.; among them, the initial setting time of the solid waste-based retarding and slightly expanding cement is 350 - 380 min, and the final setting time is 420 - 460 min; the compressive strength at 3 days ≥ 20 Mpa; the compressive strength at 28 days ≥ 45 MPa; the dry shrinkage rate at 28 days ≤ 0.09%; the linear expansion rate at 7 days ≥ 0.15%, and the linear expansion rate at 28 days ≤ 0.5%.

[0011] The retarding principle of the solid waste-based retarding and slightly expanding cement provided by the present invention is as follows: The present invention incorporates industrial solid wastes such as phosphogypsum and phosphorus tailings into the portland cement clinker formulation. P, S, and F in them are dissolved in the clinker minerals and have a retarding effect after dissolving in water, prolonging the setting time compared with conventional clinker. The retarding grinding aid contains organic compounds such as ethylene glycol, triethanolamine, monoethanol diisopropanolamine, and triisopropanolamine. These compounds have the characteristics of polarity, asymmetric structure and the existence of positive and negative charge centers, and are easily adsorbed on the Ca 2+The active site saturates and breaks the valence bonds to shield the aggregation force between particles to prevent aggregation from occurring. It can eliminate the electrostatic adsorption on the surface of the grinding media, improve the over-grinding phenomenon of cement particles, thus showing a promoting effect on the grinding process, reducing the particle size ratio of <3 μm, and slowing down the initial hydration rate. Sodium gluconate is added as a retarder to the retarding grinding aid. Due to its multiple hydroxyl active groups (five hydroxyl groups), it can bind more firmly to the hydrogen bonds between the hexagonal hydrate layers of calcium aluminate hydrate, thus prolonging the induction period. At the same time, the presence of its carboxylic acid group (one carboxyl group) increases its complexation with Ca2, reduces the concentration of [Ca2], and delays the formation of crystal nuclei. Moreover, in the crystal nuclei of the generated Ca(OH)2, the proportion of octahedral crystals decreases, while the amorphous Ca(OH)2 increases, hindering the crystal development, thus having a more obvious retarding effect. Due to the influence of the Ca(OH)2 generated during the hydration of C3S in the modified phosphogypsum and cement, ettringite (C3A·3CaSiO4·31H2O) is formed during the hydration of C3A and coats on the surface of C3A. The coating layer continuously thickens and breaks under the expansion of ettringite, forming a barrier on the surface of the cement, thus preventing the rapid hydration of the cement.

[0012] The retarding effects of natural gypsum and desulfurized gypsum are not strong. After adding them, the setting time of the cement is too short to meet the requirements, while the setting time of unmodified phosphogypsum is too long and unstable. After the phosphogypsum is modified, the calcined phosphogypsum tailings contain highly active CaO and MgO, which react with soluble phosphorus and fluorine to form inert and insoluble substances, neutralizing the acidic impurities. By grinding and drying with high-calcium steel slag, the composition of the phosphogypsum is further stabilized, and the crystal structure is improved, and the retarding effect is greatly improved and controllable within a stable range. During the same hydration cycle, most of the dihydrate gypsum in the modified phosphogypsum is converted into hemihydrate gypsum, with stronger reaction activity. Compared with natural gypsum or desulfurized gypsum, the generated sulfate ions are more likely to react with cement minerals such as C3A, and the formed ettringite protective layer is faster. Therefore, its retarding ability is stronger. Secondly, eutectic phosphorus is a phenomenon of isomorphous substitution in which phosphate ions replace sulfate ions during the crystallization of calcium sulfate dihydrate in phosphogypsum. During the hydration process of cement, eutectic phosphorus dissolves out with the dissolution of phosphogypsum and becomes soluble phosphorus. The trace soluble phosphorus generated in the modified phosphogypsum reacts with the hydroxide generated by the hydration of the cement to form insoluble phosphorus and fluoride salts, which will adhere to the surface of the cement clinker particles, delaying the hydration rate of the cement and extending the setting time of the cement compared with natural gypsum or desulfurized gypsum. Therefore, the modified phosphogypsum obtained in the present invention can stably achieve the retarding effect, and then combined with the retarding components of the grinding aid for adjustment, the setting time of the cement can be stably controlled within the target range.

[0013] The principle of the micro-expansion property (compensating shrinkage effect) of the solid waste-based retarding and slightly expanding cement provided by the present invention is as follows:

[0014] First, reduce the proportion of C3A and increase the proportion of C4AF in the clinker mineral composition to endow it with certain anti-shrinkage properties. Retarding components in the formula, such as modified phosphogypsum, generate ettringite after cement hydration, which has a micro-expansion property. Magnesium oxide and free calcium oxide in cementitious material components such as clinker, fly ash, and high-calcium steel slag powder also have expansibility after hydration, ultimately forming expansion elements (AFt + f-CaO + MgO). These components can produce a micro-expansion effect during the hydration process, thereby compensating for the shrinkage during the cement hardening process. Products such as calcium hydroxide (Ca(OH)2) generated during cement hydration can react with other components to form hydration products with a larger volume under specific conditions (such as when an appropriate amount of active admixture is incorporated), thereby filling the tiny pores in the cement hardened body and reducing shrinkage. Reactive silica (SiO2) and alumina (Al2O3) in fly ash can react with calcium hydroxide generated by cement hydration to form a denser C-S-H gel (calcium silicate hydrate). This gel has good volume stability and helps reduce shrinkage.

[0015] Further, in the preparation method of the modified phosphogypsum, the calcination temperature of the phosphogypsum tailings is 850 - 1000 °C.

[0016] Further, in the preparation method of the modified phosphogypsum, the mass ratio of the phosphogypsum is 60% - 75%; the mass ratio of the phosphogypsum tailings after high-temperature calcination is 5% - 10%; the mass ratio of the high-calcium steel slag is 15% - 30%.

[0017] Further, the raw materials of the Portland cement clinker include main components SiO2, Fe2O3, Al2O3, CaO, MgO, as well as trace elements K, Na, S, Cl, P, F, meeting the requirements of corresponding quality standards; the chemical composition of the Portland cement clinker, by mass fraction, includes C3S 54% - 62%, C2S 17% - 21%, C3A 5% - 7%, and C4AF 10% - 14%.

[0018] Further, the raw materials of the Portland cement clinker include: 78% - 88% calcareous raw materials, 5% - 13% aluminosilicate raw materials, 2% - 4.5% ferrous raw materials, and 3% - 7% auxiliary materials.

[0019] Even further, the calcareous raw materials include limestone and calcium-containing waste residues; the aluminosilicate raw materials include shale and / or sandstone; the ferrous raw materials include at least one of steel slag, iron tailings, and copper slag; the auxiliary materials include phosphogypsum, phosphogypsum tailings, and phosphorus slag.

[0020] Even further, in the calcareous raw materials, the mass ratio of the limestone to the calcium-containing waste residues is (5 - 8):(2 - 5).

[0021] Furthermore, the calcium-containing waste residue in the calcium raw material includes at least one of mud cake, calcium-containing powder (obtained by dust collection of the powder generated from the production of manufactured sand and aggregate), and high-calcium slag; the calcium-containing powder is obtained by dust collection of the powder generated from the production of manufactured sand and aggregate.

[0022] Furthermore, the mass ratio of phosphogypsum, phosphorous tailings, and phosphorous slag in the auxiliary material is (2 - 4):(6 - 8):(1 - 10).

[0023] Further, the preparation method of the Portland cement clinker includes the following steps: mixing the calcium raw material, aluminosilicate raw material, iron raw material, and auxiliary material in proportion, obtaining raw meal fines with an average particle size of 25 - 30 µm and a residue on 80 µm sieve of 10% - 15% after grinding and drying, calcining the raw meal fines at a high temperature of 1400 - 1450 °C for 0.5 - 1.5 h, and rapidly cooling to obtain the Portland cement clinker.

[0024] Further, the main component of the retarder grinding aid is an alcohol amine liquid grinding aid, and the raw materials of the retarder grinding aid include: 8% - 12% ethylene glycol, 6% - 10% triethanolamine, 6% - 12% monoethanol diisopropanolamine, 16% - 20% triisopropanolamine, 6% - 12% sodium gluconate, and 44% - 48% water.

[0025] Furthermore, the raw materials of the retarder grinding aid include: 10% ethylene glycol, 8% triethanolamine, 8% monoethanol diisopropanolamine, 18% triisopropanolamine, 10% sodium gluconate, and 46% water.

[0026] Further, the slag is a powder obtained by grinding granulated blast furnace slag to a specific surface area of 100 - 300 m 2 / kg.

[0027] Further, the fly ash is a powder with a residue on 45 µm sieve of 10% - 60%.

[0028] Further, the high-calcium steel slag is a powder obtained by grinding low-grade high-calcium steel slag to a specific surface area of 150 - 350 m 2 / kg.

[0029] Furthermore, the calcium-containing powder is obtained by dust collection of the powder generated from the production of manufactured sand and aggregate.

[0030] The preparation method of the solid waste-based retarder micro-expansion cement includes the following steps:

[0031] The Portland cement clinker, slag, and steel slag are respectively pre-ground and then mixed, and then modified phosphogypsum, fly ash, calcium-containing powder, and retarding grinding aid are added and mixed, and ground to a specific surface area of 400 - 450 m 2 / kg to obtain the solid waste-based retarding and slightly expanding cement.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The retarding and slightly expanding cement provided by the present invention has the advantages of stable retarding effect and good slightly expanding performance, solves the problems of unqualified expansion rate, large fluctuation of setting time, difficult to control, and low early strength of existing cement, and can ensure stable performance while meeting the technical requirements.

[0034] 2. On the premise that the performance of the retarding and slightly expanding cement provided by the present invention meets the standards, the maximum amount of solid waste used can reach 70%, and the production cost is lower than that of general cement.

[0035] 3. The retarding and slightly expanding cement provided by the present invention makes extensive use of industrial solid waste and low-grade ores. Through the application of industrial solid waste and the mineralization effect of phosphorus and fluorine, the phosphogypsum is modified by using phosphorus tailings and high-calcium steel slag, turning waste into treasure, solving the problem of comprehensive utilization of industrial solid waste such as phosphorus chemical industry, making full use of the existing raw materials and production equipment of enterprises, reducing the production cost, and having environmental protection benefits such as saving materials and making use of waste. Specific Embodiments

[0036] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0037] The present invention provides a solid waste-based retarding and slightly expanding cement, and its raw materials by mass percentage include: 40% - 50% of Portland cement clinker, 0.04% - 0.06% of retarding grinding aid, 8% - 12% of high-calcium steel slag, 10% - 16% of slag, 8% - 16% of fly ash, 8% - 12% of modified phosphogypsum, and 8% - 12% of calcium-containing powder;

[0038] Among them, the preparation method of the modified phosphogypsum includes the following steps: mixing the phosphogypsum with the phosphorus tailings after high-temperature calcination evenly, storing for 10 - 30 days to obtain a mixture; mixing the mixture with high-calcium steel slag for grinding and drying to obtain the modified phosphogypsum; in the following specific embodiments, the drying is completed by the waste heat in the cement kiln exhaust gas. While drying, the mixture can also absorb CO2 in the exhaust gas, further achieving the effect of environmental protection and low carbon.

[0039] In some examples, in the preparation method of the modified phosphogypsum, the calcination temperature of the phosphogypsum tailings is 850-1000 °C.

[0040] In some examples, in the preparation method of the modified phosphogypsum, the mass ratio of the phosphogypsum is 60%-75%; the mass ratio of the phosphogypsum tailings after high-temperature calcination is 5%-10%; the mass ratio of the high-calcium steel slag is 15%-30%.

[0041] The raw materials of the Portland cement clinker include the main components SiO2, Fe2O3, Al2O3, CaO, MgO, and trace elements K, Na, S, Cl, P, F, meeting the requirements of the corresponding quality standards; in some examples, the chemical composition of the Portland cement clinker, by mass fraction, includes C3S 54%-62%, C2S 17%-21%, C3A 5%-7%, and C4AF 10%-14%.

[0042] In some examples, the raw materials of the Portland cement clinker include: 78%-88% calcareous raw materials, 5%-13% aluminosilicate raw materials, 2%-4.5% ferrous raw materials, and 3%-7% auxiliary materials.

[0043] In some examples, the calcareous raw materials include limestone and calcium-containing waste residues, and the mass ratio of the limestone to the calcium-containing waste residues is (5-8):(2-5); the aluminosilicate raw materials include one or a mixture of two of shale and sandstone; the ferrous raw materials include one or a mixture of at least two of steel slag, iron tailings, and copper slag; the auxiliary materials include phosphogypsum, phosphogypsum tailings, and yellow phosphorus slag, and the mass ratio of the phosphogypsum, phosphogypsum tailings, and yellow phosphorus slag is (2-4):(6-8):(1-10).

[0044] In some examples, the preparation method of the Portland cement clinker is as follows: Mix the calcareous raw materials, aluminosilicate raw materials, ferrous raw materials, and auxiliary materials in proportion, and after grinding and drying, obtain raw meal fines with an average particle size of 25-30 µm and a residue on a 80 µm sieve of 10%-15%. Calcinate the raw meal fines at a high temperature of 1400-1450 °C for 0.5-1.5 h, and rapidly cool to obtain Portland cement clinker.

[0045] In some examples, the slag is powder obtained by grinding granulated blast furnace slag to a specific surface area of 100-300 m 2 / kg.

[0046] In some examples, the fly ash is powder with a residue on a 45 µm sieve of 10%-60%.

[0047] In some examples, the high-calcium steel slag is obtained by grinding low-grade high-calcium steel slag to a powder with a specific surface area of 150 - 350 m 2 / kg.

[0048] In some examples, the raw materials of the retarding grinding aid include: 8% - 12% ethylene glycol, 6% - 10% triethanolamine, 6% - 12% monoethanol diisopropanolamine, 16% - 20% triisopropanolamine, 6% - 12% sodium gluconate, and 44% - 48% water.

[0049] In the following specific examples, the retarding grinding aid is obtained by mixing 10% ethylene glycol, 8% triethanolamine, 8% monoethanol diisopropanolamine, 18% triisopropanolamine, 10% sodium gluconate, and 46% water; the specific surface area of the slag powder is 230 m 2 / kg; the specific surface area of the high-calcium steel slag powder is 300 m 2 / kg; the fly ash is a powder with a 45 µm sieve residue of 30%; the calcium-containing powder is obtained from the dust collection of building aggregates and manufactured sand; Table 1 shows the main chemical components of the raw materials used in the following specific examples.

[0050] Table 1: Main chemical composition of raw materials (wt%)

[0051]

[0052] Example 1

[0053] A solid waste-based retarding and slightly expanding cement is prepared as follows:

[0054] (1) Prepare Portland cement clinker: Select calcareous raw materials, aluminosilicate raw materials, ferrous raw materials, and auxiliary materials with mass percentages of 82%, 10.8%, 3%, and 4.2% respectively; the above raw materials are ground and dried to obtain raw meal fines with an average particle size of 26 µm and an 80 µm sieve residue of 12%. The raw meal fines are calcined at 1400 °C for 1 h and then rapidly cooled to obtain Portland cement clinker.

[0055] The composition of the calcareous raw materials is: 65% high-calcium limestone and 35% calcium-containing waste residue (the calcium-containing waste residue is high-calcium slag);

[0056] The composition of the aluminosilicate raw materials is: 50% shale and 50% sandstone;

[0057] The composition of the ferrous raw materials is: 100% iron tailings;

[0058] The composition of the auxiliary materials is: 57% phosphorus tailings, 14% phosphogypsum, and 29% yellow phosphorus slag.

[0059] (2) Preparation of modified phosphogypsum: Mix phosphogypsum evenly with phosphogypsum tailings calcined at 900 °C, and store the mixture in a warehouse for 15 days to obtain a mixture; grind the mixture and high-calcium steel slag in a mill to a certain fineness, and use the waste heat in the exhaust gas of the cement kiln for drying. While drying, the mixture absorbs CO2 in the exhaust gas to obtain modified phosphogypsum with setting retardation and slight expansion properties; among them, the dosage ratios of the phosphogypsum, phosphogypsum tailings after high-temperature calcination, and high-calcium steel slag are 70%, 8%, and 22% respectively.

[0060] (3) Weigh 45% of Portland cement clinker, 0.05% of setting retarder grinding aid, 15% of slag powder, 10% of high-calcium steel slag powder, 8.95% of modified phosphogypsum, 11% of fly ash, and 10% of calcium-containing powder.

[0061] (4) Pre-grind Portland cement clinker, slag, and steel slag separately and then mix them, then add modified phosphogypsum, fly ash, calcium-containing powder, and setting retarder grinding aid, and grind them through a ball mill until the specific surface area of the cement is 420 m 2 / kg, and the residue on a 45 μm sieve is 6.2% to obtain solid waste-based setting retarder and slightly expanding cement.

[0062] The loss on ignition of the Portland cement clinker is 0.24%, the free calcium oxide is 1.15%, the sulfur trioxide is 0.52%, and the alkali content is 0.54%. The chemical composition of the Portland cement clinker is calculated by mass fraction: C3S 58%, C2S 19.8%, C3A 5.5%, C4AF 12.5%.

[0063] Example 2

[0064] A solid waste-based setting retarder and slightly expanding cement, the preparation steps are as follows:

[0065] (1) Preparation of Portland cement clinker: Select calcareous raw materials, aluminosilicate raw materials, ferrous raw materials, and auxiliary materials according to mass percentages of 82%, 10.8%, 3%, and 4.2% respectively. After grinding and drying the above raw materials, obtain raw meal fines with an average particle size of 26 µm and a residue on an 80 µm sieve of 12%. The raw meal fines are calcined at 1400 °C for 1 h and obtained Portland cement clinker through rapid cooling.

[0066] The composition of the calcareous raw materials is: 80% high-calcium limestone, 20% calcium-containing waste residue (the calcium-containing waste residue is high-calcium slag);

[0067] The composition of the aluminosilicate raw materials is: 100% sandstone;

[0068] The composition of the ferrous raw materials is: 100% iron tailings;

[0069] The composition of the auxiliary materials is: 30% phosphogypsum tailings, 20% phosphogypsum, 50% yellow phosphorus slag.

[0070] (2) Preparation of modified phosphogypsum: Mix phosphogypsum evenly with phosphogypsum tailings calcined at 900 °C, and store the mixture in a warehouse for 30 days to obtain a mixture; grind the mixture and high-calcium steel slag in a mill to a certain fineness, and use the waste heat in the exhaust gas of the cement kiln for drying. While drying, the mixture absorbs CO2 in the exhaust gas to obtain modified phosphogypsum with setting retardation and micro-expansion properties; among them, the dosage ratios of the phosphogypsum, phosphogypsum tailings after high-temperature calcination, and high-calcium steel slag are 65%, 5%, and 30% respectively.

[0071] (3) Weigh 40% of Portland cement clinker, 0.05% of setting retarder grinding aid, 16% of slag powder, 10% of high-calcium steel slag powder, 12% of modified phosphogypsum, 10.95% of fly ash, and 11% of calcium-containing powder.

[0072] (4) Pre-grind Portland cement clinker, slag, and steel slag separately and then mix them, and then add modified phosphogypsum, fly ash, calcium-containing powder, and setting retarder grinding aid and mix them. Grind them through a ball mill until the specific surface area of the cement is 440 m 2 / kg, and the residue on a 45 μm sieve is 5.5% to obtain solid waste-based setting retarder and micro-expansion cement.

[0073] The loss on ignition of the Portland cement clinker is 0.21%, the free calcium oxide is 0.95%, the sulfur trioxide is 0.56%, and the alkali content is 0.58%. The chemical composition of the Portland cement clinker is, by mass fraction: C3S 60.2%, C2S 18.6%, C3A 6.0%, C4AF 12.0%.

[0074] Example 3

[0075] A solid waste-based setting retarder and micro-expansion cement, the preparation steps are as follows:

[0076] (1) Preparation of Portland cement clinker: Select calcareous raw materials, aluminosilicate raw materials, ferrous raw materials, and auxiliary materials with mass percentages of 82%, 10.8%, 3%, and 4.2% respectively. After grinding and drying the above raw materials, obtain raw meal fines with an average particle size of 26 µm and a residue on an 80 µm sieve of 12%. Calcine the raw meal fines at a high temperature of 1400 °C for 1 h, and obtain Portland cement clinker through rapid cooling.

[0077] The composition of the calcareous raw materials is: 50% high-calcium limestone, 50% calcium-containing waste residue (the calcium-containing waste residue is high-calcium slag);

[0078] The composition of the aluminosilicate raw materials is: 100% shale;

[0079] The composition of the ferrous raw materials is: 100% iron tailings;

[0080] The composition of the auxiliary materials is as follows: 50% phosphorus tailings slag, 25% phosphogypsum, and 25% yellow phosphorus slag.

[0081] (2) Prepare modified phosphogypsum: Mix phosphogypsum evenly with phosphorus tailings slag calcined at 900 °C, and store the mixture in a warehouse for 15 days to obtain a mixture; grind the mixture and high-calcium steel slag in a mill to a certain fineness, and use the waste heat in the exhaust gas of the cement kiln for drying. While drying, the mixture absorbs CO2 in the exhaust gas to obtain modified phosphogypsum with setting retardation and micro-expansion properties; among them, the dosage ratios of the phosphogypsum, phosphorus tailings slag after high-temperature calcination, and high-calcium steel slag are 75%, 10%, and 15% respectively.

[0082] (3) Weigh 50% of Portland cement clinker, 0.05% of setting retarder grinding aid, 10% of slag powder, 10% of high-calcium steel slag powder, 8% of modified phosphogypsum, 13.95% of fly ash, and 8% of calcium-containing powder.

[0083] (4) Pre-grind Portland cement clinker, slag, and steel slag separately and then mix them. Then add modified phosphogypsum, fly ash, calcium-containing powder, and setting retarder grinding aid and mix them. Grind through a ball mill until the specific surface area of the cement is 420 m 2 / kg, and the residue on a 45 μm sieve is 6.4% to obtain solid waste-based setting retarder micro-expansion cement.

[0084] The loss on ignition of the Portland cement clinker is 0.23%, the free calcium oxide is 1.0%, the sulfur trioxide is 0.52%, and the alkali content is 0.55%. The chemical composition of the Portland cement clinker is calculated by mass fraction as follows: C3S 59.2%, C2S 19.5%, C3A 6.2%, and C4AF 12.3%.

[0085] Comparative Example 1

[0086] A solid waste-based cement, the preparation steps of which are basically the same as those of Example 1, except that step (2) is missing, that is, the phosphogypsum is not modified. The raw materials of the cement are: 45% of Portland cement clinker, 0.05% of setting retarder grinding aid, 15% of slag powder, 10% of high-calcium steel slag powder, 8.95% of phosphogypsum, 11% of fly ash, and 10% of calcium-containing powder.

[0087] Comparative Example 2

[0088] A solid waste-based cement, the preparation steps of which are basically the same as those of Example 1, except that a common cement grinding aid (an alkanolamine liquid grinding aid currently used by cement enterprises in the market) is used. The raw materials of the cement are: 45% of Portland cement clinker, 0.05% of common cement grinding aid, 15% of slag powder, 10% of high-calcium steel slag powder, 8.95% of modified phosphogypsum, 11% of fly ash, and 10% of calcium-containing powder.

[0089] Comparative Example 3

[0090] A solid waste-based cement has the same preparation steps as in Example 1, except that in the process of preparing modified phosphogypsum in step (2), an equal amount of initial phosphogypsum tailings is used to replace the phosphogypsum tailings after high-temperature calcination.

[0091] Comparative Example 4

[0092] A solid waste-based cement has the same preparation steps as in Example 1, except that step (2) is as follows: Phosphogypsum, phosphogypsum tailings after calcination at 900 °C, and high-calcium steel slag are ground in a mill to a certain fineness, and dried using the waste heat in the cement kiln exhaust gas. While drying, the mixture absorbs CO2 in the exhaust gas to obtain modified phosphogypsum; among them, the dosage ratios of the phosphogypsum, phosphogypsum tailings after high-temperature calcination, and high-calcium steel slag are 70%, 8%, and 22% respectively.

[0093] Test the performance of the solid waste-based retarding and slightly expanding cement of Examples 1 to 3 and Comparative Examples 1 to 4: Determine the setting time of the cement according to the GB / T1346-2011 standard; test the 3-day and 28-day strengths according to the GB / T 17671-2021 standard; determine its 7-day and 28-day expansion rates according to JC / T 313-2009; determine the 28-day dry shrinkage rate of cement mortar according to JC / T 603-2004. The test results are shown in Table 2.

[0094] Table 2: Performance test results of the solid waste-based retarding and slightly expanding cement of Examples 1 to 3 and Comparative Examples 1 to 4

[0095]

[0096] In summary, the present invention uses raw materials including calcareous raw materials, aluminosilicate raw materials, ferrous raw materials, and auxiliary materials to make Portland cement clinker; uses calcined phosphogypsum tailings and high-calcium steel slag to modify phosphogypsum, and compound the modified phosphogypsum with Portland cement clinker, fly ash, steel slag, slag, calcium-containing powder, and retarding grinding aids to prepare solid waste-based retarding and slightly expanding cement. The synergistic effect of each component makes the prepared solid waste-based retarding and slightly expanding cement have the advantages of stable retarding effect, compensating shrinkage effect, and continuous growth of later strength; among them, the initial setting time of the solid waste-based retarding and slightly expanding cement is 350 - 380 min, and the final setting time is 420 - 460 min; the 3-day compressive strength ≥ 20 Mpa; the 28-day compressive strength ≥ 45 MPa; the 28-day dry shrinkage rate ≤ 0.09%; the 7-day linear expansion rate ≥ 0.15%, and the 28-day linear expansion rate ≤ 0.5%.

[0097] The above specific embodiments have described the implementation of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solutions of the present invention, and these simple variations all fall within the protection scope of the present invention.

Claims

1. A solid waste-based retarding slightly expansive cement, characterized in that, Its raw materials, by mass percentage, include: 40% - 50% of portland cement clinker, 0.04% - 0.06% of retarding type grinding aid, 8% - 12% of high-calcium steel slag, 10% - 16% of slag, 8% - 16% of fly ash, 8% - 12% of modified phosphogypsum, and 8% - 12% of calcium-containing powder; Among them, the preparation method of the modified phosphogypsum includes the following steps: Mix phosphogypsum and phosphorus tailings after high-temperature calcination evenly, store for 10 - 30 days to obtain a mixture; Mix the mixture with high-calcium steel slag for grinding and drying to obtain modified phosphogypsum.

2. The waste-based retarding slightly expansive cement according to claim 1, characterized in that In the preparation method of the modified phosphogypsum, the mass ratio of the phosphogypsum is 60% - 75%; the mass ratio of the phosphorus tailings after high-temperature calcination is 5% - 10%; the mass ratio of the high-calcium steel slag is 15% - 30%.

3. A solid waste-based retarder and slightly expansive cement according to claim 1, characterized in that, Its raw materials, by mass percentage, are: 45% of portland cement clinker, 0.05% of retarding type grinding aid, 10% of high-calcium steel slag, 15% of slag, 11% of fly ash, 8.95% of modified phosphogypsum, and 10% of calcium-containing powder.

4. A solid waste-based retarding and slightly expanding cement according to claim 1, characterized in that, The chemical composition of the portland cement clinker, by mass fraction, includes C3S 54% - 62%, C2S 17% - 21%, C3A 5% - 7%, and C4AF 10% - 14%.

5. A solid waste-based retarding and slightly expanding cement according to claim 4, characterized in that, The raw materials of the portland cement clinker include: 78% - 88% of calcareous raw materials, 5% - 13% of aluminosilicate raw materials, 2% - 4.5% of ferrous raw materials, and 3% - 7% of auxiliary materials.

6. The retarder micro-expansion cement based on solid waste according to claim 5, characterized in that, The calcareous raw materials include limestone and calcium-containing waste residue; the aluminosilicate raw materials include shale and / or sandstone; the ferrous raw materials include at least one of steel slag, iron tailings, and copper slag; the auxiliary materials include phosphogypsum, phosphorus tailings, and yellow phosphorus slag.

7. A solid waste-based retarding and slightly expanding cement according to claim 4, characterized in that, The preparation method of the portland cement clinker includes the following steps: Mix the calcareous raw materials, aluminosilicate raw materials, ferrous raw materials, and auxiliary materials evenly, obtain raw meal fine powder after grinding and drying, and calcine the raw meal fine powder at a high temperature of 1400 - 1450 °C and then cool it rapidly to obtain portland cement clinker.

8. A solid waste-based retarding and slightly expanding cement according to claim 1, characterized in that, The raw materials of the retarding type grinding aid include: 8% - 12% of ethylene glycol, 6% - 10% of triethanolamine, 6% - 12% of monoethanol diisopropanolamine, 16% - 20% of triisopropanolamine, 6% - 12% of sodium gluconate, and 44% - 48% of water.

9. The solid waste-based retarder micro-expansion cement according to claim 8, characterized in that, The raw materials of the retarding type grinding aid include: 10% of ethylene glycol, 8% of triethanolamine, 8% of monoethanol diisopropanolamine, 18% of triisopropanolamine, 10% of sodium gluconate, and 46% of water.

10. The preparation method of a solid waste-based retarding and slightly expanding cement according to any one of claims 1 to 9, characterized in that, It includes the following steps: Pre-grind the portland cement clinker, slag, and steel slag respectively and then mix them, then add modified phosphogypsum, fly ash, calcium-containing powder, and retarding type grinding aid and mix them, and obtain solid waste-based retarding slightly expansive cement through grinding.

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