Solid waste based cementing material and preparation method thereof

Abstract

The invention discloses a solid waste based cementing material and a preparation method thereof, and belongs to the technical field of building materials. The solid waste-based cementing material is prepared from the following components in percentage by mass: 35-45% of calcined carbide slag, 15-25% of blast furnace slag, 15-25% of steel slag, 5-10% of coal cinder and 10-15% of carbide slag, wherein the content of CaO in the calcined carbide slag is not lower than 65 wt.%, and the content of Ca (OH) 2 in the carbide slag is not lower than 70 wt.%. According to the invention, the high-activity waste-based cementing material is obtained through reasonable selection and dosage allocation of the slag solid waste, and the solid waste-based cementing material does not need to be added with a conventional strong alkali activator, so that the cost is greatly saved. The solid waste-based cementing material provided by the invention adopts cheap all-solid waste materials as raw materials, and the preparation method is simple, so that the solid waste-based cementing material is very beneficial to large-scale popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a solid waste-based gelling material and a preparation method thereof. Background Art

[0002] Solid waste-based cementitious materials (SWBCMs) are materials with cementitious properties (hydraulic or air-hardening) produced using industrial solid waste or construction waste as primary raw materials through physical, chemical, or activation treatment techniques. These materials can partially or completely replace traditional cement, offering significant environmental and resource utilization benefits.

[0003] Solid waste-based cementitious materials are mostly composed of non-clinker base materials and active stimulants. Some varieties contain other admixtures. Non-clinker base materials fall into two main categories: pozzolanic materials and slag-based materials. Solid waste-based cementitious materials primarily exploit the potential activity within non-clinker base materials to create a cementitious material that undergoes a relatively complete hydration reaction.

[0004] The potential activity of pozzolanic cementitious materials primarily stems from amorphous silica, alumina, and metakaolin. Different pozzolanic materials can be further categorized based on the activators used. Lime-based pozzolanic cementitious materials use a Ca(OH)2-type activator, while geopolymers use a NaOH-type activator.

[0005] The potential activity of cementitious materials based on slag materials mainly comes from calcium-silicon-aluminum glass. According to different activators, they can be divided into: gypsum slag cementitious materials composed of slag materials and Ca(OH)2 type active activators, and alkali slag cementitious materials composed of slag materials and NaOH type active activators.

[0006] For cementitious materials based on slag materials, due to the low reaction activity of slag materials, they need to rely on strong alkaline activators (such as NaOH, water glass, Ca(OH)2, etc.), which have problems of high corrosiveness and high cost, and their large-scale application is limited; and the strength of concrete prepared with this type of cementitious materials is often far inferior to that of traditional cementitious materials (cement), making it difficult to meet engineering needs. Summary of the Invention

[0007] To address the above technical issues, the present invention provides a solid waste-based cementitious material and a method for preparing the same. By selecting and compounding slag-based solid waste, a completely solid waste-based cementitious material formula is obtained. This solid waste-based cementitious material does not require the addition of conventional strong alkaline activators, significantly saving costs. Furthermore, by selecting the right slag type and controlling the amount of slag used, the activity of the solid waste-based cementitious material is effectively enhanced, enabling the production of higher-strength concrete.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention is to provide a solid waste-based cementitious material, which comprises, by weight percentage, 35-45% of calcined carbide slag, 15-25% of blast furnace slag, 15-25% of steel slag, 5-10% of coal slag and 10-15% of carbide slag;

[0010] The CaO content in the calcined carbide slag is not less than 65wt.%; the Ca(OH)2 content in the carbide slag is not less than 70wt.%.

[0011] The raw materials used for the solid waste-based cementitious material of the present invention are all solid waste materials, among which calcined carbide slag is the main source of CaO, blast furnace slag is used to supplement SiO2, Al2O3 and activity, steel slag is used to supplement Fe2O3 and part of CaO, and coal slag is used to adjust the ratio of SiO2 and Al2O3. Since the four components provided by the present invention are combined according to specific percentages to obtain a composition that is relatively close to ordinary Portland cement (controlling the lime saturation coefficient LSF = 0.9~1.0, the silicon rate SR = 2.0~3.0, and the aluminum rate IM = 1.0~2.5), the combined cementitious material has higher activity. The components also contain carbide slag with a high Ca(OH)2 content, which acts as an alkali activator to fully activate the activity of calcined carbide slag, blast furnace slag, steel slag and coal slag.

[0012] Preferably, the CaO content in the blast furnace slag is 35-45wt.%, the SiO2 content is 30-40wt.%, and the Al2O3 content is 8-15wt.%.

[0013] Preferably, the content of CaO in the steel slag is 40-50 wt.%, the content of iron oxide is 10-25 wt.%, and the content of SiO2 is 10-20 wt.%.

[0014] Preferably, the content of SiO2 in the coal slag is 40-60 wt.%, and the content of Al2O3 is 20-30 wt.%.

[0015] Preferably, the calcined carbide slag, the blast furnace slag, the steel slag, the coal slag and the carbide slag are all dry powders, and the specific surface area is not less than 400m2 / kg, and the moisture content does not exceed 5wt.%.

[0016] Preferably, the calcined carbide slag is obtained by calcining carbide slag at a temperature of 800-900° C. for not less than 5 minutes.

[0017] The second technical solution of the present invention is to provide a method for preparing the above-mentioned solid waste-based gelling material, comprising the following steps:

[0018] The solid waste-based gelling material is obtained by uniformly mixing the dry powders of the calcined carbide slag, the blast furnace slag, the steel slag, the coal slag and the carbide slag in predetermined proportions.

[0019] The third technical solution of the present invention is to provide an application of the above-mentioned solid waste-based cementitious material in the preparation of concrete.

[0020] The fourth technical solution of the present invention is to provide an application of the above-mentioned solid waste-based gelling material in the preparation of solid filling materials.

[0021] The beneficial technical effects of the present invention are as follows:

[0022] (1) The present invention provides a solid waste-based gelling material, wherein the raw materials of the solid waste-based gelling material are all solid waste materials.

[0023] (2) The present invention obtains a highly active waste-based gelling material by rationally selecting and adjusting the amount of slag solid waste. The solid waste-based gelling material does not require the addition of conventional strong alkaline activators, which greatly saves costs.

[0024] (3) The solid waste-based cementitious material provided by the present invention is a cheap all-solid waste material, and the preparation method is simple, which is very conducive to large-scale promotion and application. DETAILED DESCRIPTION

[0025] Carbide slag is an industrial waste residue produced when calcium carbide (CaC2) is hydrolyzed to produce acetylene (C2H2). Its main component is calcium hydroxide. About 1.2 tons of dry-based carbide slag is produced for every ton of acetylene produced.

[0026] The main components of carbide slag include Ca(OH)2.

[0027] The mineral phase of carbide slag is mainly calcium hydroxide.

[0028] The characteristics of carbide slag are strong alkalinity (pH 12-13), a moisture content of up to 40-50%, and a powdery state after drying.

[0029] At present, the main treatment and utilization methods of carbide slag are:

[0030] (1) Lime replacement: used for flue gas desulfurization, acid wastewater treatment and / or soil remediation.

[0031] (2) As a building material raw material: production of cement (instead of limestone) and gypsum board (compounded with phosphogypsum).

[0032] (3) Production of chemical products: calcium carbonate (reacts with CO2), calcium chlorate (used as snow-melting agent).

[0033] (4) Used for carbon capture: Calcium hydroxide reacts with CO2 to form calcium carbonate, achieving carbon fixation.

[0034] Blast furnace slag is a byproduct of blast furnace smelting during the ironmaking process. When iron ore, coke, and flux (such as limestone) are reduced at high temperatures to produce pig iron, the gangue and fuel ash in the ore combine with the flux to form a molten slag. Upon cooling, it forms a glassy or crystalline solid. Approximately 300 million tons of blast furnace slag are produced annually worldwide, and its resource utilization is crucial to the sustainable development of the metallurgical industry.

[0035] The main components of blast furnace slag include CaO, SiO2 and Al2O3.

[0036] The mineral phases of blast furnace slag are mainly dicalcium silicate (C2S) and gehlenite, and the cooling method affects its morphology (for example, water-quenched slag is glassy, while slowly cooled slag is crystalline).

[0037] The characteristics of blast furnace slag are high hardness (Mohs hardness 5-6) and density 2.8-3.0g / cm 3 , has potential gelling activity, especially the water-quenched slag can react with cement hydration products after grinding.

[0038] At present, the main treatment and utilization methods of blast furnace slag are:

[0039] (1) Cement replacement: Ground blast furnace slag (GGBS) can replace 30-70% of cement, reducing the heat of hydration and improving the resistance to sulfate attack.

[0040] (2) As road construction material: used as asphalt mixture aggregate or roadbed filler, with both wear resistance and drainage properties.

[0041] (3) Production of microcrystalline glass: High-strength, corrosion-resistant building decoration materials can be produced through high-temperature remelting.

[0042] (4) Used for soil improvement: rich in calcium and silicon, it can adjust the pH value of acidic soil and supplement trace elements.

[0043] Steel slag is a solid waste generated during the steelmaking process, primarily from converters, electric furnaces, or refining furnaces. Its composition is complex and fluctuates widely. Global annual production is approximately 180 million tons, with a utilization rate of less than 70%. Its handling is more difficult than blast furnace slag.

[0044] The main components of steel slag include CaO, FeO and SiO2.

[0045] The mineral phases of steel slag are mainly tricalcium silicate (C3S), dicalcium silicate (C2S) and RO phase (FeO-MgO-MnO solid solution).

[0046] The characteristics of steel slag are high hardness (Mohs hardness 6-7) and density 3.0-3.6g / cm 3 , containing expansive components (f-CaO expands more than 3 times in volume when in contact with water).

[0047] At present, the main treatment and utilization methods of steel slag are:

[0048] (1) Metal recovery: Magnetic separation is used to extract iron-containing particles (iron grade 50-60%) and return them to the steelmaking process.

[0049] (2) Used in road engineering: After aging and stabilization, it can be used as asphalt aggregate or roadbed material, and the f-CaO content must be controlled to be less than 3%.

[0050] (3) As a cement admixture: Partially replace cement clinker, but stability issues need to be resolved (such as steam pressure curing).

[0051] (4) For carbon sequestration: Utilize the high calcium content of steel slag to capture CO2, generate calcium carbonate and solidify heavy metals.

[0052] Coal ash is the bottom ash produced after coal is burned in coal-fired power plants or industrial boilers. Globally, over 1 billion tons are produced annually, and its utilization is crucial to reducing pollution from stockpiles.

[0053] The main components of coal slag include SiO2 and Al2O3.

[0054] The mineral phase of coal slag is mainly a glass phase formed by rapid cooling after high-temperature melting.

[0055] The characteristics of coal slag are porous and irregular particles, a wide range of particle sizes, and a low bulk density (about 700-1200 kg / m 3 ), the water absorption rate is relatively high (up to 15-25%).

[0056] At present, the main treatment and utilization methods of coal slag are:

[0057] (1) As a building material: It can replace natural sand or gravel to prepare lightweight concrete; after being ground, it can be used as an auxiliary cementitious material to reduce the amount of cement used; it can be mixed with clay or cement and sintered to produce environmentally friendly bricks or hollow blocks; it can replace traditional sand and gravel to be used for filling road or railway subgrades.

[0058] (2) As an adsorption material: using porous structures to adsorb heavy metals or organic pollutants in wastewater.

[0059] (3) Used for soil improvement: regulating soil pH and supplementing nutrients such as silicon and calcium.

[0060] Potentially active solid wastes, such as slag and steel slag, are mostly used in concrete in the form of admixtures and additives, but the amount of solid waste that can be absorbed is small. Therefore, previous researchers have conducted extensive research on solid waste-based cementitious materials, aiming to stimulate the activity of solid waste and thereby produce cementitious properties. However, due to the large fluctuations in the physical and chemical properties of raw materials, high activation costs, and lack of experience among construction workers, solid waste cementitious materials are not yet widely used. However, the advantages of developing solid waste-based cementitious materials are also very obvious. For example, solid waste-based cementitious materials can consume large amounts of stored industrial solid waste while reducing greenhouse gas emissions during cement production.

[0061] Based on the characteristics of various solid wastes, the inventors have developed a specific combination of all-solid waste-based cementitious materials. The main consideration is to make a reasonable combination based on the characteristics of different solid wastes so that the combined mixture is as close to silicate cement as possible in terms of components. On this basis, an alkali activator is further added to obtain a highly active solid waste-based cementitious material.

[0062] The technical concept provided by this invention may enable the design of more solid waste combinations to obtain other types of solid waste-based cementitious materials. If cost is not a consideration, replacing the alkaline activator carbide slag in this invention with other mature industrial alkaline activators should also achieve the technical objectives of this invention.

[0063] Currently, research on all-solid waste-based cementitious materials is not mature. The high-activity all-solid waste-based cementitious materials provided by the present invention have the potential to replace low-grade cement and can meet the technical needs of general projects with low strength requirements.

[0064] Solid waste-based cementitious materials offer significant competitive advantages over traditional building materials. First, their raw materials are derived from solid waste, ensuring full resource utilization and environmental friendliness. Second, they can significantly improve concrete performance, such as strength and durability. Furthermore, they offer excellent pricing, bringing significant economic benefits to related companies.

[0065] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0066] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0067] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0069] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0070] The calcined carbide slag, blast furnace slag, steel slag, coal slag, carbide slag and coal gangue used in the examples and comparative examples of the present invention are all dry powders (with a moisture content of no more than 5 wt.%).

[0071] The calcined carbide slag used in the embodiments of the present invention and the comparative examples was prepared by calcining the carbide slag at 900° C. for 10 min and then mechanically grinding it to obtain a CaO content of 75 wt.% and a specific surface area of 467 m 2 / kg.

[0072] The blast furnace slag used in the examples of the present invention and the comparative examples has a CaO content of 37 wt.%, a SiO2 content of 33 wt.%, and an Al2O3 content of 11 wt.%.

[0073] The steel slag used in the examples of the present invention and the comparative examples has a CaO content of 43 wt.%, an iron oxide (FeO) content of 14 wt.%, and a SiO2 content of 16 wt.%.

[0074] The coal slag used in the examples of the present invention and the comparative examples has a SiO2 content of 51 wt.% and an Al2O3 content of 22 wt.%.

[0075] The Ca(OH)2 content of the carbide slag used in the embodiments of the present invention and the comparative examples is 82wt.%.

[0076] The coal gangue used in the comparative example of the present invention has a SiO2 content of 53 wt.% and an Al2O3 content of 20 wt.%.

[0077] Example 1

[0078] Preparation of solid waste-based cementitious materials:

[0079] 40 wt.% of calcined carbide slag, 20 wt.% of blast furnace slag, 20 wt.% of steel slag, 10 wt.% of coal slag and 10 wt.% of carbide slag are added into a horizontal plow mixer for mechanical mixing. The plow speed is set to 100 rpm, the fly cutter speed is set to 2000 rpm, and the mixing time is 10 min to obtain a uniform solid waste-based cementitious material.

[0080] Example 2

[0081] Preparation of solid waste-based cementitious materials:

[0082] 37 wt.% of calcined carbide slag, 25 wt.% of blast furnace slag, 17 wt.% of steel slag, 6 wt.% of coal slag and 15 wt.% of carbide slag were added into a horizontal plow mixer for mechanical mixing. The plow speed was set to 100 rpm, the fly cutter speed was set to 2000 rpm, and the mixing time was 10 min to obtain a uniform solid waste-based cementitious material.

[0083] Example 3

[0084] Preparation of solid waste-based cementitious materials:

[0085] 42 wt.% of calcined carbide slag, 16 wt.% of blast furnace slag, 21 wt.% of steel slag, 8 wt.% of coal slag and 13 wt.% of carbide slag were added into a horizontal plow mixer for mechanical mixing. The plow speed was set to 100 rpm, the fly cutter speed was set to 2000 rpm, and the mixing time was 10 min to obtain a uniform solid waste-based cementitious material.

[0086] Comparative Example 1

[0087] Preparation of solid waste-based cementitious materials:

[0088] Compared with Example 1, the only difference is that the carbide slag in the raw materials is omitted.

[0089] Comparative Example 2

[0090] Preparation of solid waste-based cementitious materials:

[0091] Compared with Example 1, the only difference is that the coal slag is replaced by coal gangue of equal mass.

[0092] Concrete was prepared using the solid waste-based cementitious materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 and ordinary Portland cement (32.5). The activity of each cementitious material was evaluated by measuring the properties of the concrete prepared in each group.

[0093] Concrete formula: 375 parts of the cementitious material to be compared, 375 parts of fly ash, 350 parts of water, 400 parts of quartz sand and 1.5 parts of polycarboxylic acid high-efficiency water-reducing agent (parts are by weight).

[0094] Compressive strength determination:

[0095] The prepared compressive test block was 50 mm × 50 mm × 50 mm in size and was tested using a YAW-200B compression testing machine with a loading speed of 0.9 kN / s. The load was continuously applied until the test block failed, and the failure value was recorded. The compressive strength of the specimen was calculated according to formula (1). The calculation results are shown in Table 1.

[0096]

[0097] In formula (1), f m,cu is the compressive strength (MPa); N u is the ultimate load (N); A is the pressure-bearing area of the specimen (mm 2 ).

[0098] Tensile strength determination:

[0099] A dog-bone specimen with a middle cross-section of 30 mm × 13 mm and a length of 80 mm was prepared and tested using a WDW-100 microcomputer-controlled electronic universal testing machine. The dog-bone specimen was placed in the fixture and the machine speed was adjusted to 0.4 mm / min for loading. During the loading process, attention was paid to the overall trend of the values and the damage of the specimen. When the overall value trend dropped significantly or large-spacing cracks appeared on the surface of the specimen, loading was stopped and the data was saved. Based on the collected load, the ultimate tensile strength σ was calculated according to formula (2) tu , the calculation results are shown in Table 1.

[0100]

[0101] In formula (2), σ is the tensile stress (MPa); F is the tensile load (N); s is the width of the specimen (mm); and t is the thickness of the specimen (mm).

[0102] Table 1 Performance test results

[0103]

[0104] As can be seen from Table 1, the solid waste-based cementitious material prepared by the present invention has a high activity. Although still lower than that of ordinary Portland cement, it can meet general engineering needs and has the potential to replace cement. Furthermore, if the carbide slag component of the solid waste-based cementitious material of the present invention is omitted, its activity is greatly reduced, indicating that the alkali-activated component has a significant impact on the activity of the solid waste-based cementitious material. Replacing the coal slag with coal gangue, which has a similar content of the main component, also reduces the activity of the solid waste-based cementitious material to a certain extent, possibly due to certain differences in the mineral phases of the two.

[0105] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A solid waste-based gelling material, characterized in that: The components are calculated by mass percentage: 35-45% of calcined carbide slag, 15-25% of blast furnace slag, 15-25% of steel slag, 5-10% of coal slag and 10-15% of carbide slag; The CaO content in the calcined carbide slag is not less than 65wt.%; the Ca(OH)2 content in the carbide slag is not less than 70wt.%.

2. The solid waste-based gelling material according to claim 1, characterized in that: The blast furnace slag has a CaO content of 35-45 wt.%, a SiO2 content of 30-40 wt.%, and an Al2O3 content of 8-15 wt.%.

3. The solid waste-based gelling material according to claim 1, characterized in that: The steel slag has a CaO content of 40-50 wt.%, an iron oxide content of 10-25 wt.%, and a SiO2 content of 10-20 wt.%.

4. The solid waste-based gelling material according to claim 1, characterized in that: The content of SiO2 in the coal slag is 40-60 wt.%, and the content of Al2O3 is 20-30 wt.%.

5. The solid waste-based gelling material according to claim 1, characterized in that: The calcined carbide slag, the blast furnace slag, the steel slag, the coal slag and the carbide slag are all dry powders, and the specific surface area is not less than 400m 2 / kg, and the moisture content does not exceed 5wt.%.

6. The solid waste-based gelling material according to claim 1, characterized in that: The calcined carbide slag is obtained by calcining carbide slag at a temperature of 800-900° C. for not less than 5 minutes.

7. A method for preparing the solid waste-based gelling material according to any one of claims 1 to 6, characterized in that: The following steps are involved: The solid waste-based gelling material is obtained by uniformly mixing the dry powders of the calcined carbide slag, the blast furnace slag, the steel slag, the coal slag and the carbide slag in predetermined proportions.

8. Use of the solid waste-based cementitious material according to any one of claims 1 to 6 in the preparation of concrete.

9. Use of the solid waste-based gelling material according to any one of claims 1 to 6 in the preparation of solid filling materials.

Images