Solid waste-based cementitious material for marine engineering plain concrete and preparation method thereof

Abstract

This invention relates to the field of civil engineering and marine engineering materials technology, specifically to a solid waste-based cementitious material for plain concrete in marine engineering and its preparation method. The solid waste-based cementitious material comprises: 50-60 parts ultrafine powder, 20-30 parts activator, 5-15 parts antifreeze agent, 10-20 parts filler, and 5-10 parts early-strength agent; the ultrafine powder includes water slag, fly ash, and steel slag; the activator includes desulfurized gypsum and silicate cement; the antifreeze agent includes denitrified fly ash and ammonium chloride; the filler is modified iron tailings powder; and the early-strength agent is one or a mixture of several of calcium chloride, magnesium chloride, and sodium chloride. This invention also provides a method for preparing the solid waste-based cementitious material for plain concrete in marine engineering. The solid waste-based cementitious material prepared by this invention has high early strength, good mechanical properties, and excellent antifreeze performance, realizing the resource utilization of solid waste in port areas.

Description

Technical Field

[0001] This invention relates to the field of materials technology in civil engineering and marine engineering, specifically to a solid waste-based cementitious material for plain concrete in marine engineering and its preparation method. Background Technology

[0002] Port-adjacent industrial clusters often rely on the advantages of coastal ports and marine resources, and their production processes consume large amounts of reclaimed water or even seawater for cooling, washing, or process water. This results in a massive amount of industrial solid waste with complex composition, low activity, and high salt content (such as desulfurization gypsum, steel slag, coal ash, and tailings). Due to their unstable properties and the presence of chloride salts and other components that can easily cause steel corrosion, these wastes are difficult to utilize on a large scale in traditional cementing systems and are mostly disposed of through stockpiling or land reclamation. This not only occupies valuable land and coastline resources but also poses a potential threat to the nearshore ecological environment, becoming a key bottleneck restricting the region's green and low-carbon transformation and sustainable development.

[0003] In marine engineering construction, there is a huge demand for plain concrete components such as breakwaters, revetments, artificial reefs, interlocking blocks, and curbs. These structures do not require reinforcement, fundamentally avoiding the risk of steel corrosion, and therefore have extremely high tolerance to harmful components such as chloride ions in solid waste-based materials. Based on this characteristic, if large quantities of port-related industrial solid waste rich in chloride salts and active ingredients can replace traditional cementitious materials and be directly used for large-scale casting of marine plain concrete components, it will not only dispose of the massive accumulation of waste, turning waste into treasure and reducing the pressure on land and shoreline occupation, but also significantly reduce project costs, meeting the construction needs of the rapid development of port and coastal infrastructure, and has enormous economic and social benefits.

[0004] Existing technologies mostly focus on the resource utilization of single types of bulk solid waste (such as fly ash, steel slag, and desulfurization gypsum), with limited research on the co-processing and comprehensive utilization of multi-source solid waste in port areas. There is an urgent need to develop a low-cost, highly controllable technological pathway for the co-utilization of multi-source solid waste, tailored to the characteristics of multi-source solid waste in port areas, to achieve deep integration of large-scale industrial solid waste disposal and green infrastructure construction in the port area. Existing solid waste materials have unstable sources and fluctuating compositions, while solid waste materials in port areas are stable, economical, and can be used in situ. However, steel slag waste in port areas is difficult to grind, has low activity, and is difficult to activate, and tailings iron ore powder also has low activity. The prepared solid waste-based cementitious materials suffer from low early strength, poor mechanical properties, and poor frost resistance. Therefore, further exploration of the efficient application of solid waste materials from port areas in the field of marine engineering has significant research and application value. Summary of the Invention

[0005] To address the challenges of effectively utilizing industrial solid waste materials in port areas, and the resulting low early strength, poor mechanical properties, and poor frost resistance in cementitious systems due to the low activity of solid waste materials, this invention provides a solid waste-based cementitious material for marine engineering plain concrete and its preparation method, thereby solving the aforementioned problems.

[0006] The technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides a solid waste-based cementitious material for plain concrete in marine engineering, comprising the following raw materials in parts by weight: 50-60 parts of ultrafine powder, 20-30 parts of activator, 5-15 parts of antifreeze agent, 10-20 parts of filler, and 5-10 parts of early strength agent.

[0008] Furthermore, the ultrafine powder is a mixture formed by ultrafine grinding of water slag, fly ash, and steel slag, with a mass ratio of water slag: fly ash: steel slag = (50-70): (30-40): (10-20); the activator is a mixture of desulfurized gypsum and silicate cement, with a mass ratio of desulfurized gypsum: silicate cement = (30-40): (60-70); the antifreeze agent is a mixture of denitrified fly ash and ammonium chloride; the filler is modified iron tailings powder; and the early strength agent is one or a mixture of calcium chloride, magnesium chloride, and sodium chloride.

[0009] Furthermore, the ultrafine powder has a specific surface area of ​​600-700 m² / kg, an activity index of ≥100% after 28 days, and a chloride ion mass fraction of ≤1%; the activator has a specific surface area of ​​400-500 m² / kg; the antifreeze has a specific surface area of ​​300-400 m² / kg; and the filler has a specific surface area of ​​500-600 m² / kg.

[0010] Furthermore, the total mass fraction of ammonium ions in the antifreeze agent is 0.1-0.3%, wherein the mass fraction of ammonium ions in the denitrification fly ash is ≤0.3%. The antifreeze agent is a mixture of denitrification fly ash and ammonium chloride. By introducing the ammonium ions contained in the denitrification fly ash itself, and combining it with the added ammonium salt components, it reacts with hydroxide ions in the strongly alkaline environment formed by the hydration reaction of the cementitious material to generate ammonia gas, thereby forming a microbubble structure. On the one hand, these microbubbles can effectively absorb and release the volume expansion pressure caused by water freezing during low-temperature freeze-thaw processes, reducing the damage to the structure caused by pore water ice expansion; on the other hand, microbubbles can improve the pore distribution inside the slurry, enhance the flexibility and crack resistance of the overall structure, effectively alleviate frost heave pressure, and improve the freeze-thaw resistance of marine concrete.

[0011] Furthermore, the water slag and steel slag in the ultrafine powder are both by-products of the blast furnace ironmaking process, and the fly ash is Grade I fly ash.

[0012] Furthermore, the desulfurization gypsum in the activator originates from the desulfurization process of power plants using recycled water or seawater for cooling, and its chloride ion mass fraction is ≤2%. The main mineral phase of the desulfurization gypsum is calcium sulfate dihydrate (CaSO4·2H2O), which can release sulfate ions (SO4) during hydration. 2- The desulfurized gypsum reacts with calcium ions in the system to form hydrate products such as ettringite. Simultaneously, the SO4 released by the desulfurized gypsum... 2- It has a certain salt activating effect on fly ash, iron tailings powder, etc., which can accelerate the dissolution and reaction of potential active mineral components, promote the secondary hydration process, and improve the cementing activity of fly ash, water slag, mineral powder and steel slag.

[0013] Furthermore, the filler-modified iron tailings powder is obtained by modifying the waste residue remaining after screening iron concentrate from the Lingang mineral processing enterprise.

[0014] Furthermore, the silicate cement in the activator is grade 42.5 ordinary silicate cement, wherein the mass fraction of the admixture is ≤5%.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned solid waste-based cementitious material, comprising the following steps:

[0016] (1) Raw material pretreatment and preparation

[0017] S1. Preparation of ultrafine powder: Weigh water slag, fly ash and steel slag according to the mass ratio (50-70): (30-40): (10-20), and put them into a vertical roller mill for ultrafine grinding until the specific surface area of ​​the mixed powder reaches 600-700m² / kg.

[0018] S2. Preparation of activator: Weigh desulfurized gypsum and silicate cement according to the mass ratio (30-40): (60-70), and grind them together to form a uniform mixture with a specific surface area of ​​400-500m² / kg.

[0019] S3. Preparation of antifreeze: Denitrified fly ash and ammonium chloride are mechanically mixed in a certain proportion, and the total mass fraction of ammonium ions in the mixture is controlled at 0.1%-0.3%;

[0020] S4. Preparation of filler: Take iron tailings waste from the Lingang ore beneficiation process and modify it to obtain modified iron tailings powder.

[0021] S5. Preparation of early strength agent: Take one or a mixture of calcium chloride, magnesium chloride, and sodium chloride to obtain the early strength agent;

[0022] (2) Precise ingredient proportioning

[0023] Weigh each component according to the following mass ratio: 50-60 parts of the ultrafine powder prepared in step S1, 20-30 parts of the activator prepared in step S2, 5-15 parts of the antifreeze prepared in step S3, 10-20 parts of the filler prepared in step S4, and 5-10 parts of the early strength agent prepared in step S5, for later use.

[0024] (3) Homogenization and mixing

[0025] The components weighed in step (2) are put into a mixer and mixed continuously until the components are evenly distributed.

[0026] Furthermore, the modification steps of the modified iron tailings powder are as follows:

[0027] S1. Take iron tailings waste from the port beneficiation process and grind it in a vertical mill to a specific surface area of ​​450-500 m² / kg to obtain pre-ground powder.

[0028] S2. Place the pre-ground powder in a high-efficiency mixer and spray it into atomized solution of a modifier solution composed of polyethylene glycol, triethanolamine and sodium lactate in a mass ratio of 1.5:1:0.5 under low-speed stirring. The total mass of the modifier is 0.8%-1.2% of the mass of the pre-ground powder to obtain a mixture.

[0029] S3. Place the mixture at 75-85℃ for aging treatment;

[0030] S4. The aged material is then subjected to final grinding in a vertical mill until the specific surface area reaches 500-600 m² / kg, yielding modified iron tailings powder. Addressing the issues of low activity and weakened interfacial transition zones in high-dosage iron tailings powder, this invention employs a compound modifier solution of polyethylene glycol, triethanolamine, and sodium lactate to modify iron tailings waste from port beneficiation. Polyethylene glycol improves wettability and dispersibility, reducing particle agglomeration; triethanolamine can complex metal ions, promote mineral activation and hydration, and also act as a grinding aid to increase the specific surface area of ​​the iron tailings powder; the synergistic effect of sodium lactate (anionic) with polyethylene glycol and triethanolamine (nonionic) enhances the potential activity of the iron tailings powder and increases the degree of secondary pozzolanic reaction.

[0031] In addition, modified tailings iron ore powder also plays a key role in the system: (1) fine filling: its micron-sized particles can effectively fill the gaps between ultrafine powder, activator and other solid waste powders, reduce the porosity of the system and increase the bulk density; (2) densification and enhancement: the good dispersibility and surface activity after modification enable it to bind more tightly with hydration products, block capillary channels, enhance the density of the slurry microstructure, and thus improve the concrete strength and frost resistance; (3) particle size optimization: its specific fineness and particle size distribution can form a continuously optimized gradation with other cementitious powders, achieve fineness complementarity, thereby reducing the amount of mixing water, improving the workability of fresh slurry and the mechanical properties and durability of hardened body.

[0032] The beneficial effects of this invention are as follows:

[0033] (1) The solid waste-based cementitious material for marine engineering plain concrete of the present invention includes ultrafine powder, activator, antifreeze agent, filler, and early strength agent. The ultrafine powder has a high specific surface area, which improves the surface activity of the material and accelerates the hydration reaction; the desulfurized gypsum in the activator can provide SO4 2- Ions promote early formation of ettringite. Furthermore, desulfurized gypsum is continuously consumed during hydration. CSH gel has a huge specific surface area, with numerous ettringite crystals filling the pores of the gel and being encapsulated by the CSH gel, optimizing the pore structure in the slurry and increasing the density of the hardened slurry. Early-strength agents accelerate the hydration reaction rate and enhance the early strength development of the material. The filler-modified iron tailings powder has good dispersibility, filling the slurry pores, improving micro-density, and enhancing the interfacial bonding force between particles and hydration products. Antifreeze agents form microbubble structures in the slurry, effectively alleviating frost heave pressure and improving the frost resistance of marine concrete. Under the synergistic effect of multiple components, this is beneficial to improving the overall performance of concrete structures.

[0034] (2) This invention uses industrial solid waste (steel slag, water slag, iron tailings, desulfurized gypsum, fly ash, etc.) in the port area as core raw materials. After being processed by grinding, surface modification and other processes, it is transformed into key components of cementitious materials. The solid waste-based cementitious materials prepared have high early strength, good mechanical properties and excellent antifreeze properties. They can digest huge amounts of accumulated waste, turn waste into treasure, effectively reduce the occupation of land and shoreline by solid waste storage and near-shore pollution, reduce raw material transportation costs, reduce engineering costs, and help the development of green and low-carbon economy in the port industry. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0036] Example 1

[0037] A solid waste-based cementitious material for plain concrete in marine engineering comprises the following raw materials in parts by weight:

[0038] 60 parts ultrafine powder, 20 parts activator, 5 parts antifreeze, 10 parts filler, and 5 parts early strength agent (calcium chloride).

[0039] A method for preparing solid waste-based cementitious materials includes the following steps:

[0040] (1) Raw material pretreatment and preparation

[0041] S1. Preparation of ultrafine powder: Weigh water slag, fly ash and steel slag according to the mass ratio of 60:30:10, and put them into a vertical roller mill for ultrafine grinding until the specific surface area is 650m² / kg, the activity index is ≥100% after 28 days, and the chloride ion mass fraction is ≤1%.

[0042] S2. Preparation of activator: Weigh out desulfurized gypsum (Cl...) according to a mass ratio of 35:65. - A homogeneous mixture of 1.5% by mass and 42.5 grade ordinary Portland cement, ground to a specific surface area of ​​450 m² / kg;

[0043] S3. Preparation of antifreeze: Denitrified fly ash with an ammonium ion content of 0.2% and ammonium chloride are mechanically mixed, and the total mass fraction of ammonium ions in the mixture is controlled to be 0.2%.

[0044] S4. Preparation of filler:

[0045] Step 1: Take iron tailings waste from the Lingang ore dressing plant and grind it in a vertical mill until the specific surface area is 450m² / kg to obtain pre-ground powder;

[0046] Step 2: Place the pre-ground powder in a high-efficiency mixer and spray it in atomized under low-speed stirring. The modifier solution is composed of polyethylene glycol, triethanolamine and sodium lactate in a mass ratio of 1.5:1:0.5. The total mass of the modifier is 0.8% of the mass of the pre-ground powder, and a mixture is obtained.

[0047] Step 3: Place the mixture at 75°C for aging treatment;

[0048] Step 4: The aged material is then subjected to final grinding in a vertical mill until the specific surface area reaches 550 m² / kg, thus obtaining modified iron tailings powder.

[0049] S5. Preparation of early strength agent: The early strength agent is calcium chloride.

[0050] (2) Precise ingredient proportioning

[0051] Weigh each component according to the following mass ratio: 60 parts of the ultrafine powder prepared in step S1, 20 parts of the activator prepared in step S2, 5 parts of the antifreeze prepared in step S3, 10 parts of the filler prepared in step S4, and 5 parts of the early strength agent prepared in step S5; set aside.

[0052] (3) Homogenization and mixing

[0053] The components weighed in step (2) are put into a biaxial zero-gravity mixer and continuously mixed for 15 minutes at a mixer speed of 200 r / min until the components are evenly distributed and a powdery finished product with consistent color and no visible impurities is obtained, namely the solid waste-based cementitious material.

[0054] Example 2

[0055] A solid waste-based cementitious material for plain concrete in marine engineering comprises the following raw materials in parts by weight:

[0056] 50 parts ultrafine powder, 30 parts activator, 5 parts antifreeze, 10 parts filler, and 5 parts early strength agent (magnesium chloride).

[0057] A method for preparing solid waste-based cementitious materials includes the following steps:

[0058] (1) Raw material pretreatment and preparation

[0059] S1. Preparation of ultrafine powder: Weigh water slag, fly ash and steel slag according to the mass ratio of 50:40:10, and put them into a vertical roller mill for ultrafine grinding until the specific surface area is 600m² / kg, the activity index is ≥100% after 28 days, and the chloride ion mass fraction is ≤1%.

[0060] S2. Preparation of activator: Weigh out desulfurized gypsum (Cl...) according to a mass ratio of 30:70. - A homogeneous mixture of 1.8% by mass and 42.5 grade ordinary Portland cement, ground to a specific surface area of ​​400 m² / kg;

[0061] S3. Preparation of antifreeze: Denitrified fly ash with an ammonium ion content of 0.1% and ammonium chloride are mechanically mixed, and the total mass fraction of ammonium ions in the mixture is controlled to be 0.1%.

[0062] S4. Preparation of filler:

[0063] Step 1: Take iron tailings waste from the Lingang ore beneficiation process and grind it in a vertical mill to a specific surface area of ​​400 m² / kg to obtain pre-ground powder;

[0064] Step 2: Place the pre-ground powder in a high-efficiency mixer and spray it in atomized under low-speed stirring. The mixture is a modifier solution composed of polyethylene glycol, triethanolamine and sodium lactate in a mass ratio of 1.5:1:0.5. The total mass of the modifier is 1.0% of the mass of the pre-ground powder, and a mixture is obtained.

[0065] Step 3: Place the mixture at 75°C for aging treatment;

[0066] Step 4: The aged material is then subjected to final grinding in a vertical mill until the specific surface area reaches 500 m² / kg, thus obtaining modified iron tailings powder.

[0067] S5. Preparation of early strength agent: The early strength agent is magnesium chloride.

[0068] (2) Precise ingredient proportioning

[0069] Weigh each component according to the following mass ratio: 50 parts of the ultrafine powder prepared in step S1, 30 parts of the activator prepared in step S2, 5 parts of the antifreeze prepared in step S3, 10 parts of the filler prepared in step S4, and 5 parts of the early strength agent prepared in step S5, for later use.

[0070] (3) Homogenization and mixing

[0071] The components weighed in step (2) are put into a biaxial zero-gravity mixer and continuously mixed for 20 minutes at a mixer speed of 250 r / min until the components are evenly distributed and a powdery finished product with consistent color and no visible impurities is obtained, which is the solid waste-based cementitious material.

[0072] Example 3

[0073] A solid waste-based cementitious material for plain concrete in marine engineering comprises the following raw materials in parts by weight:

[0074] 50 parts ultrafine powder, 20 parts activator, 15 parts antifreeze, 10 parts filler, and 5 parts early strength agent (sodium chloride).

[0075] A method for preparing solid waste-based cementitious materials includes the following steps:

[0076] (1) Raw material pretreatment and preparation

[0077] S1. Preparation of ultrafine powder: Weigh water slag, fly ash and steel slag according to the mass ratio of 70:30:20, and put them into a vertical roller mill for ultrafine grinding until the specific surface area is 700m² / kg, the activity index is ≥100% after 28 days, and the chloride ion mass fraction is ≤1%.

[0078] S2. Preparation of activator: Weigh out desulfurized gypsum (Cl...) according to a mass ratio of 40:60. - A homogeneous mixture of 0.8% (by mass) and 42.5 grade ordinary Portland cement, ground to a specific surface area of ​​500 m² / kg;

[0079] S3. Preparation of antifreeze: Denitrified fly ash with an ammonium ion content of 0.25% and ammonium chloride are mechanically mixed, and the total mass fraction of ammonium ions in the mixture is controlled to be 0.3%;

[0080] S4. Preparation of filler:

[0081] Step 1: Take iron tailings waste from the Lingang ore dressing plant and grind it in a vertical mill to a specific surface area of ​​550 m² / kg to obtain pre-ground powder;

[0082] Step 2: Place the pre-ground powder in a high-efficiency mixer and spray it in atomized under low-speed stirring. The modifier solution is a compound of polyethylene glycol, triethanolamine and sodium lactate in a mass ratio of 1.5:1:0.5. The total mass of the modifier is 1.2% of the mass of the pre-ground powder, and a mixture is obtained.

[0083] Step 3: Place the mixture at 75°C for aging treatment;

[0084] Step 4: The aged material is then subjected to final grinding in a vertical mill until the specific surface area reaches 600 m² / kg, thus obtaining modified iron tailings powder.

[0085] S5. Preparation of early strength agent: The early strength agent is magnesium chloride.

[0086] (2) Precise ingredient proportioning

[0087] Weigh each component according to the following mass ratio: 50 parts of the ultrafine powder prepared in step S1, 20 parts of the activator prepared in step S2, 15 parts of the antifreeze prepared in step S3, 10 parts of the filler prepared in step S4, and 5 parts of the early strength agent prepared in step S5; set aside.

[0088] (3) Homogenization and mixing

[0089] The components weighed in step (2) are put into a biaxial zero-gravity mixer and continuously mixed for 20 minutes at a mixer speed of 300 r / min until the components are evenly distributed and a powdery finished product with consistent color and no visible impurities is obtained, namely the solid waste-based cementitious material.

[0090] Example 4

[0091] A solid waste-based cementitious material for plain concrete in marine engineering comprises the following raw materials in parts by weight:

[0092] 50 parts ultrafine powder, 22 parts activator, 8 parts antifreeze, 15 parts filler, and 5 parts early strength agent (a mixture of calcium chloride and magnesium chloride in a 1:1 mass ratio).

[0093] A method for preparing solid waste-based cementitious materials includes the following steps:

[0094] (1) Raw material pretreatment and preparation

[0095] S1. Preparation of ultrafine powder: Weigh water slag, fly ash and steel slag according to the mass ratio of 55:35:10, and put them into a vertical roller mill for ultrafine grinding until the specific surface area is 630m² / kg, the activity index is ≥100% after 28 days, and the chloride ion mass fraction is ≤1%.

[0096] S2. Preparation of activator: Weigh out desulfurized gypsum (Cl...) according to the mass ratio of 38:62. -A homogeneous mixture of 1.0% by mass and 42.5 grade ordinary Portland cement, ground to a specific surface area of ​​480 m² / kg;

[0097] S3. Preparation of antifreeze: The preparation method is the same as in Example 1;

[0098] S4. Preparation of filler: The preparation method is the same as in Example 1;

[0099] S5. Preparation of early strength agent: The early strength agent is a mixture of calcium chloride and magnesium chloride in a mass ratio of 1:1;

[0100] (2) Precise ingredient proportioning

[0101] Weigh each component according to the following mass ratio: 50 parts of the ultrafine powder prepared in step S1, 22 parts of the activator prepared in step S2, 8 parts of the antifreeze prepared in step S3, 15 parts of the filler prepared in step S4, and 5 parts of the early strength agent prepared in step S5; set aside.

[0102] (3) Homogenization and mixing

[0103] The components weighed in step (2) are put into a biaxial zero-gravity mixer and continuously mixed for 20 minutes at a mixer speed of 300 r / min until the components are evenly distributed and a powdery finished product with consistent color and no visible impurities is obtained, namely the solid waste-based cementitious material.

[0104] Example 5

[0105] A solid waste-based cementitious material for plain concrete in marine engineering comprises the following raw materials in parts by weight:

[0106] 50 parts ultrafine powder, 20 parts activator, 8 parts antifreeze, 12 parts filler, and 10 parts early strength agent (sodium chloride).

[0107] A method for preparing solid waste-based cementitious materials includes the following steps:

[0108] (1) Raw material pretreatment and preparation

[0109] S1. Preparation of ultrafine powder: Weigh water slag, fly ash and steel slag according to the mass ratio of 65:35:15, and put them into a vertical roller mill for ultrafine grinding until the specific surface area is 680m² / kg, the activity index is ≥100% after 28 days, and the chloride ion mass fraction is ≤1%.

[0110] S2. Preparation of activator: Weigh out desulfurized gypsum (Cl...) according to the mass ratio of 32:68. - A homogeneous mixture of 1.2% by mass and 42.5 grade ordinary Portland cement, ground to a specific surface area of ​​420 m² / kg;

[0111] S3. Preparation of antifreeze: The preparation method is the same as in Example 1;

[0112] S4. Preparation of filler: The preparation method is the same as in Example 1;

[0113] S5. Preparation of early strength agent: The early strength agent is sodium chloride;

[0114] (2) Precise ingredient proportioning

[0115] Weigh each component according to the following mass ratio: 50 parts of the ultrafine powder prepared in step S1, 20 parts of the activator prepared in step S2, 8 parts of the antifreeze prepared in step S3, 12 parts of the filler prepared in step S4, and 10 parts of the early strength agent prepared in step S5; set aside.

[0116] (3) Homogenization and mixing

[0117] The components weighed in step (2) are put into a biaxial zero-gravity mixer and continuously mixed for 20 minutes at a mixer speed of 300 r / min until the components are evenly distributed and a powdery finished product with consistent color and no visible impurities is obtained, namely the solid waste-based cementitious material.

[0118] For each implementation case, a mortar test block was prepared with a water-to-binder ratio of 0.5.

[0119] The mass of each component in Examples 1-5 is shown in Table 1 below.

[0120] Table 1

[0121]

[0122] The comparative example used ordinary Portland cement material with a strength grade of 42.5 for experimental control.

[0123] The compressive strength and flexural strength of the test blocks were determined according to the standard GB / T50081—2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete; the mass loss of the test blocks after 300 freeze-thaw cycles was determined according to the standard GB / T50082—2009 Test Methods for Long-Term Performance and Durability of Ordinary Concrete; and the 28-day activity index of the ultrafine powder was determined according to the standard JG-T486-2015 Composite Admixtures for Concrete.

[0124] Examples 1-5 and the comparative examples were tested for the compressive strength, flexural strength and frost resistance of concrete. The experimental data are shown in Table 2 below.

[0125] Table 2

[0126]

[0127] As can be seen from the data in Table 2, the 3-day and 28-day flexural strength and compressive strength of Examples 1-5 of the present invention are basically at the same level as those of the comparative examples. This indicates that the solid waste-based cementitious material for marine engineering plain concrete provided by the present invention has good mechanical properties. The mass loss after 300 freeze-thaw cycles is significantly lower than that of the comparative examples, and the freeze-thaw resistance is excellent.

[0128] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A solid waste-based geopolymer cementitious material for marine engineering applications, characterized in that, The raw materials include the following parts by weight: 50-60 parts ultrafine powder, 20-30 parts activator, 5-15 parts antifreeze, 10-20 parts filler, and 5-10 parts early strength agent; The ultrafine powder is a mixture formed by ultrafine grinding of water slag, fly ash, and steel slag, with a mass ratio of water slag: fly ash: steel slag = (50-70): (30-40): (10-20); the activator is a mixture of desulfurized gypsum and silicate cement, with a mass ratio of desulfurized gypsum: silicate cement = (30-40): (60-70); the antifreeze agent is a mixture of denitrified fly ash and ammonium chloride; the filler is modified iron tailings powder; and the early strength agent is one or a mixture of calcium chloride, magnesium chloride, and sodium chloride. The modification steps for the modified iron tailings powder are as follows: S1. Take iron tailings waste from the port beneficiation process and grind it in a vertical mill to a specific surface area of ​​450-500 m². 2 / kg, to obtain pre-ground powder; S2. Place the pre-ground powder in a high-efficiency mixer and atomize it with a modifier solution composed of polyethylene glycol, triethanolamine and sodium lactate in a mass ratio of 1.5:1:0.

5. The total mass of the modifier is 0.8%-1.2% of the mass of the pre-ground powder to obtain a mixture. S3. Place the mixture at 75-85℃ for aging treatment; S4. The aged material is then subjected to final grinding in a vertical mill until the specific surface area reaches 500-600 m². 2 / kg, to obtain modified iron tailings powder.

2. The solid waste-based cementitious material for marine engineering plain concrete as described in claim 1, characterized in that, The specific surface area of ​​the ultrafine powder is 600-700 m². 2 / kg, 28-day activity index ≥100%, chloride ion mass fraction ≤1%; the activator has a specific surface area of ​​400-500 m² / kg. 2 / kg; the specific surface area of ​​the antifreeze is 300-400m². 2 / kg; the specific surface area of ​​the filler is 500-600m². 2 / kg.

3. A solid waste-based geopolymer cementitious material for marine engineering concrete as claimed in claim 1, wherein, The total mass fraction of ammonium ions in the antifreeze is 0.1-0.3%, of which the mass fraction of ammonium ions in the denitrification fly ash is ≤0.3%.

4. A solid waste-based geopolymer cementitious material for marine engineering concrete as claimed in claim 1, wherein, The ultrafine powder contains water slag and steel slag, both of which are byproducts of the blast furnace ironmaking process, and fly ash, which is Class I fly ash.

5. A solid waste-based geopolymer cementitious material for marine engineering concrete as claimed in claim 1, wherein, The desulfurized gypsum in the activator is derived from the desulfurization process of a power plant that uses recycled water or seawater for cooling, and its chloride ion mass fraction is ≤2%.

6. A solid waste-based geopolymer cementitious material for marine engineering concrete as claimed in claim 1, wherein, The filler-modified iron tailings powder is obtained by modifying the waste residue left over after screening iron concentrate in the Lingang mineral processing enterprise.

7. A solid waste-based cementitious material for plain concrete in marine engineering as described in claim 1, characterized in that, The silicate cement in the activator is grade 42.5 ordinary silicate cement, wherein the mass fraction of the admixture is ≤5%.

8. A method for preparing a solid waste-based cementitious material for marine engineering plain concrete as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Raw material pretreatment and preparation S1. Preparation of ultrafine powder: Weigh water slag, fly ash, and steel slag according to the mass ratio (50-70):(30-40):(10-20), and put them together into a vertical roller mill for ultrafine grinding until the specific surface area of ​​the mixed powder reaches 600-700 m². 2 / kg; S2. Preparation of activator: Weigh desulfurized gypsum and silicate cement according to the mass ratio (30-40):(60-70), and grind them together until the specific surface area is 400-500 m². 2 A homogeneous mixture per kg; S3. Preparation of antifreeze: Denitrified fly ash and ammonium chloride are mechanically mixed in a certain proportion, and the total mass fraction of ammonium ions in the mixture is controlled at 0.1%-0.3%; S4. Preparation of filler: Take iron tailings waste from the Lingang ore beneficiation process and modify it to obtain modified iron tailings powder. S5. Preparation of early strength agent: Take one or a mixture of calcium chloride, magnesium chloride, and sodium chloride to obtain the early strength agent; (2) Precise ingredient proportioning Weigh each component according to the following mass ratio: 50-60 parts of the ultrafine powder prepared in step S1, 20-30 parts of the activator prepared in step S2, 5-15 parts of the antifreeze prepared in step S3, 10-20 parts of the filler prepared in step S4, and 5-10 parts of the early strength agent prepared in step S5, for later use. (3) Homogenization and mixing The components weighed in step (2) are put into a mixer and mixed continuously.

9. The method for preparing a solid waste-based cementitious material for plain concrete in marine engineering as described in claim 8, characterized in that, In step (1), the modification steps of the modified iron tailings powder are as follows: S1. Take iron tailings waste from the port beneficiation process and grind it in a vertical mill to a specific surface area of ​​450-500 m². 2 / kg, to obtain pre-ground powder; S2. Place the pre-ground powder in a high-efficiency mixer and atomize it with a modifier solution composed of polyethylene glycol, triethanolamine and sodium lactate in a mass ratio of 1.5:1:0.

5. The total mass of the modifier is 0.8%-1.2% of the mass of the pre-ground powder to obtain a mixture. S3. Place the mixture at 75-85℃ for aging treatment; S4, the aged material is ground in a vertical mill to a specific surface area of 500-600 m2 / kg to obtain modified iron tailings powder. 2 / kg, modified iron tailings powder is obtained.

Images