A method for morphology control of solid waste-based core-shell artificial aggregate

Abstract

The application discloses a kind of solid waste-based core-shell artificial aggregate morphology control method, aggregate morphology includes spheroidal and non-spheroidal.This method includes six major steps of solid waste powder activity excitation, water pretreatment, particle forming, particle morphology control, particle densification, maintenance enhancement, by selecting different water content, water demand ratio of solid waste powder material, and adjusting the inclination angle of granulator, rotation speed, water spraying frequency, water spraying amount, powder adding frequency and powder adding amount etc.Granulation parameters, prepare spheroidal and non-spheroidal artificial aggregate.The application method is simple, environmental benefit is good, and the aggregate of different morphology can be controlled.Spheroidal aggregate has high sphericity, good fluidity, but weak adhesion with cement paste, and is suitable for pumping concrete.Non-spheroidal aggregate has irregular shape, low sphericity, good adhesion, and is suitable for pavement concrete, precast concrete and other concrete with lower fluidity requirement.

Description

Technical Field

[0001] This invention belongs to the field of artificial aggregate technology, specifically relating to a method for controlling the morphology of solid waste-based core-shell artificial aggregates, including spherical and non-spherical aggregates. Background Technology

[0002] Aggregates are one of the main components of concrete, accounting for over 60% of its volume. With the increasing scarcity of natural sand and gravel resources, artificial aggregates have the potential to partially replace them. Simultaneously, with the growing pressure to treat bulk solid waste such as fly ash, sludge, industrial tailings, smelting slag, and recycled powder, the resource-based utilization of solid waste to produce artificial aggregates has attracted widespread attention. This can not only alleviate the current shortage of natural sand and gravel aggregates but also improve the utilization rate of solid waste and reduce CO2 emissions, which is of great significance to the sustainable development of the concrete industry.

[0003] Currently, most artificial aggregates are spherical in shape. These aggregates have high sphericity and good fluidity, making them suitable for pumped concrete. However, the spherical structure leads to poor interfacial bonding between the aggregate and cement paste, and the transition zone between the aggregate and cement paste is easily damaged, resulting in low compressive strength in the prepared concrete. Non-spherical aggregates, due to their irregular shape and low sphericity, can significantly improve the bonding performance between the aggregate and cement paste. However, the fluidity of the concrete prepared with non-spherical aggregates is inferior, making them suitable for pavement concrete, precast concrete, and other concretes with lower fluidity requirements.

[0004] Existing patents already cover the preparation of spherical and non-spherical artificial aggregates. CN114031323A, CN112194400A, and CN112707663A use a disc granulation method to prepare core-shell type artificial aggregates, which are spherical aggregates. CN112661430 uses a disc method to prepare irregularly shaped artificial aggregates. However, these patents can only produce artificial aggregates with one morphology and cannot control the morphology of the artificial aggregates to prepare artificial aggregates with different morphological requirements.

[0005] Spherical and non-spherical aggregates each have their own advantages and disadvantages, and are applied in different fields. Therefore, by designing the performance of solid waste powders and improving the process, it is of great significance to develop a method for controlling the morphology of solid waste-based core-shell artificial aggregates, and to prepare aggregates with different morphologies to meet the needs of different application fields and realize the resource utilization of solid waste powders. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention aims to provide a method for controlling the morphology of solid waste-based core-shell type artificial aggregates through solid waste powder performance design and process improvement. This method can produce near-spherical and non-spherical aggregates, meeting the needs of different application fields and broadening the application range of artificial aggregates.

[0007] To achieve its objectives, the present invention employs the following technical solution.

[0008] The raw materials of the solid waste-based core-shell type artificial aggregate of the present invention are composed of the following parts by mass: 6-20 parts of core material, 300-400 parts of solid waste powder material, 50-120 parts of binder, 50-60 parts of water, 1-5 parts of grinding aid, and 1-5 parts of additive.

[0009] The core material includes one or more of the following: recycled sand, polystyrene, expanded perlite, coal gangue, and waste residue.

[0010] The solid waste powder material includes one or more of the following: sludge, steel slag powder, nickel slag, lead core tailings, red mud, recycled micro powder, stone powder, etc.

[0011] The solid waste powder material has a moisture content of 0.1-2% and a water requirement of 20-120%.

[0012] The binder includes one or more of the following: fly ash, cement, clay, alkali activator, bentonite, etc.

[0013] The grinding aid includes one or more of triethanolamine, sodium tripolyphosphate, polyacrylate, glycol, etc.

[0014] The additives include one or more of sodium hydroxide, calcium hydroxide, sodium sulfate, sodium silicate, and calcium chloride.

[0015] The grinding aid is an analytical chemical reagent. The additive is an analytical chemical reagent.

[0016] The morphology control method for solid waste-based core-shell type artificial aggregates of the present invention includes the following steps:

[0017] (1) Activation of solid waste powder: The solid waste powder material, binder and grinding aid are mixed evenly to obtain a mixed powder;

[0018] (2) Water pretreatment: Add additives to the water and stir evenly;

[0019] (3) Particle forming: The core material is added to the disc granulator, and then some of the mixed powder obtained in step (1) is added. Atomized water is sprayed evenly on the particles to initially form particles. The particle size is controlled to be 5-8 mm.

[0020] (4) Particle morphology control: According to the different morphology requirements of artificial aggregates, the remaining mixed powder is added to the disc granulator and sprayed with mist water. Different water content and water requirement ratio of powder materials are selected, and different spraying frequencies, powder addition frequencies, spraying water volume and powder addition volume are adjusted to finally form particles with different morphologies, with particle sizes ranging from 5 to 20 mm. The added mixed powder and sprayed water are the mixed powder and water remaining after use in step (3).

[0021] (5) Dense particles: The particles roll continuously in the granulator without adding any powder materials or water.

[0022] (6) Curing and strengthening: The particles obtained in step (5) are cured by a non-calcination process to obtain aggregates with different morphologies.

[0023] In step (1), the mixed powder is pre-dried and crushed before use, and then ground by a ball mill to a particle size ≤0.075mm.

[0024] The amount of mixed powder added in step (3) is 15-35% of the total mass of the mixed powder.

[0025] In step (3), the amount of water sprayed in mist accounts for 15-35% of the total water used.

[0026] During granulation, the disc granulator is tilted at an angle of 45 to 60° and rotates at a speed of 30 to 40 r / min.

[0027] In step (4), particles with different morphologies can be produced by adjusting the water spraying frequency, powder addition frequency, water spraying volume, and powder addition volume. When the water spraying frequency and powder addition frequency are low, and the water spraying volume and powder addition volume are large each time, spherical particles can be prepared. When the water spraying frequency and powder addition frequency are high, and the water spraying volume and powder addition volume are small each time, non-spherical particles can be prepared.

[0028] Furthermore, by using solid waste powder materials with a moisture content of 0.2-1% and a water requirement ratio of 20-90%, and controlling the water spraying frequency and powder addition frequency to 1 time / 20s-1 time / 60s, with each powder addition amount being 1-3% of the powder material and each water spraying amount being 1-3% of the total water volume, spherical aggregates can be obtained.

[0029] Furthermore, by using solid waste powder materials with a moisture content of 0.7-2% and a water requirement ratio of 70-120%, and controlling the water spraying frequency and powder addition frequency to 1 time / 3s to 1 time / 5s, with each powder addition amount being 0.2-1% of the powder material and each water spraying amount being 0.2-1% of the total water volume, non-spherical aggregates can be obtained.

[0030] In step (6), the non-calcination curing process is selected from one or more of cold curing, carbonization curing, and steam curing.

[0031] The core-shell structured aggregate of this invention consists of a core material encapsulated by a powder material. Different properties and sizes of aggregates can be controlled by adjusting the type and size of the core material and the type and size of the shell material.

[0032] This invention provides a method for controlling the morphology of core-shell type artificial aggregates, which can prepare spherical and non-spherical aggregates. The produced spherical aggregates have high sphericity and good flowability, making them suitable for pumped concrete. The produced non-spherical aggregates have irregular shapes, low sphericity, and good bonding properties, making them suitable for pavement concrete, precast concrete, and other concretes with lower flowability requirements. The artificial aggregates with different morphologies prepared by this invention can meet the needs of different application fields, thus broadening the application range of artificial aggregates. Attached Figure Description

[0033] Figure 1 The raw materials for different morphological aggregates prepared in this invention are recycled micro powder (a) and recycled sand (b);

[0034] Figure 2 Schematic diagrams of spherical aggregate (a) and non-spherical aggregate (b) prepared according to the present invention;

[0035] Figure 3 The diagram shows cross-sectional views of different morphological aggregates prepared according to the present invention, wherein (a) is a spherical artificial aggregate and (b) is a non-spherical artificial aggregate.

[0036] Figure 4 This is a particle size distribution diagram of the regenerated micro powder (RFP) used in this invention and after grinding for 30 minutes (30minRFP). Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and should not be construed as limiting the present invention or its application or use in any way. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The present invention will now be described in detail with reference to embodiments, so that those skilled in the art can understand the present invention.

[0039] The raw materials used in this embodiment are as follows (by weight): 6-20 parts recycled sand, 300-400 parts recycled micro-powder, 50-120 parts cement, 50-60 parts water, 1-5 parts grinding aid, and 1-5 parts additive. The grinding aid is triethanolamine, and the additive is calcium chloride. The granulation equipment is a disc granulator. The moisture content of the recycled micro-powder required for preparing spherical aggregates is 0.2-1%, and the water requirement ratio is 20-95%. The moisture content of the recycled micro-powder required for preparing non-spherical aggregates is 0.7-2%, and the water requirement ratio is 95-120%.

[0040] 1. Preparation of spherical artificial aggregates

[0041] (1) Grind the regenerated micro powder and triethanolamine in a planetary ball mill for 30 minutes, and then mix them evenly with cement to obtain a mixed powder material; Figure 4 The particle size distribution of regenerated micropowder (RFP) and regenerated micropowder after grinding with triethanolamine for 30 min (30 min RFP) is shown in Table 1. Table 1 shows the composition of the regenerated micropowder.

[0042] Table 1. Composition of regenerated micro powder

[0043] chemical composition CaO SiO <![CDATA[SO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> MgO other Ingredient content 57.71 16.73 7.63 6.38 5.40 2.06 2.02 0.63 1.44

[0044] (2) Add calcium chloride to water and stir well.

[0045] (3) Place all the recycled sand into the granulator, start the granulator, tilt it at 50°, and rotate it at 40 r / min. Continuously add powder material and spray water evenly onto the particles. Initially form particles with a diameter of 5-8 mm. The amount of powder material added and water sprayed should be 15-35% of the final required amount of powder material and total water. This stage lasts 5-8 minutes.

[0046] (4) Continue adding powder material to the granulator and evenly spray mist water onto the granules. The spraying frequency and powder adding frequency are 1 time / 20s to 1 time / 60s. The amount of powder added each time is 1 to 3% of the powder material, and the amount of water sprayed each time is 1 to 3% of the total water volume. Finally, granules with a particle size of 5 to 20 mm are formed. The added powder material and sprayed water are the remaining portion. This stage lasts for 8 to 10 minutes.

[0047] (5) The granules continue to roll in the granulator without adding any powder material or water. This stage lasts for 3 to 5 minutes.

[0048] (6) Carbonize and cure the particles obtained in step (5), wherein the carbon dioxide concentration is 20-70%, the temperature is controlled at 20±1℃, and the humidity is controlled at 70±5%.

[0049] After the above six steps, spherical aggregates are obtained, such as... Figure 2As shown in (a).

[0050] The aggregates underwent performance testing. The sphericity of the aggregates was determined using a 3D scanner to acquire 3D data, followed by spherical harmonic reconstruction. Product performance is as follows:

[0051]

[0052] Sphericity can be defined as the ratio of the surface area of ​​a sphere of the same volume as the particle to the actual surface area of ​​the particle, which characterizes the degree to which the particle shape approximates a standard sphere. Its value ranges from 0 to 1, and the closer it is to 1, the closer the particle is to a sphere. The specific calculation formula is shown in Equation (1).

[0053]

[0054] In the formula, S is the aggregate surface area and V is the particle volume.

[0055] 2. Preparation of non-spherical aggregates

[0056] Repeat steps (1) to (6) above, except in step (4) the water spraying frequency and powder addition frequency are changed to once / 3s to once / 5s, and the powder addition amount and water spraying amount are changed to 0.2% to 1% of the powder material each time, and 0.2% to 1% of the total water amount each time, to obtain non-spherical aggregates such as Figure 2 As shown in (b).

[0057] The aggregate was subjected to performance testing, and the product performance is as follows:

[0058]

Claims

1. A method for morphology control of solid waste-based core-shell type artificial aggregate, characterized in that... Includes the following steps: (1) Activation of solid waste powder: The solid waste powder material, binder and grinding aid are mixed evenly to obtain a mixed powder; (2) Water pretreatment: Add additives to the water and stir evenly; (3) Particle forming: The core material is added to the disc granulator, and then some of the mixed powder obtained in step (1) is added. Atomized water is sprayed evenly on the particles to initially form particles. The particle size is controlled to be 5~8mm. The amount of mixed powder added in step (3) is 15-35% of the total mass of the mixed powder, and the amount of water sprayed in mist accounts for 15-35% of the total water used; (4) Particle morphology control: According to the different morphology requirements of artificial aggregates, the remaining mixed powder is added to the disc granulator and sprayed with mist water: use solid waste powder materials with a moisture content of 0.2~1% and a water demand ratio of 20~90%, and control the water spraying frequency and powder addition frequency to 1 time / 20s~1 time / 60s, the amount of powder added each time is 1~3% of the powder material, and the amount of water sprayed each time is 1~3% of the total water volume to obtain spherical aggregates; use solid waste powder materials with a moisture content of 0.7~2% and a water demand ratio of 70~120%, and control the water spraying frequency and powder addition frequency to 1 time / 3s~1 time / 5s, the amount of powder added each time is 0.2~1% of the powder material, and the amount of water sprayed each time is 0.2~1% of the total water volume to obtain non-spherical aggregates; the particle size is 5~20mm; The added mixed powder and sprayed water are the remaining mixed powder and water after step (3) is used; (5) Dense particles: The particles continuously roll in the granulator; (6) Curing and strengthening: The particles obtained in step (5) are cured by a non-calcination process to obtain aggregates with different morphologies; The core material includes one or more of the following: recycled sand, polystyrene, expanded perlite, and waste residue; The solid waste powder material includes one or more of the following: sludge, steel slag powder, nickel slag, lead core tailings, red mud, recycled micro powder, and stone powder. The adhesive is cement; The grinding aid includes one or more of triethanolamine, sodium tripolyphosphate, polyacrylate, and glycol; The additives include one or more of sodium hydroxide, calcium hydroxide, sodium sulfate, sodium silicate, and calcium chloride.

2. The morphology control method according to claim 1, characterized in that: The raw materials of the solid waste-based core-shell artificial aggregate are composed of the following parts by mass: 6-20 parts core material, 300-400 parts solid waste powder material, 50-120 parts binder, 50-60 parts water, 1-5 parts grinding aid, and 1-5 parts additives.

3. The morphology control method according to claim 1, characterized in that: In step (1), the mixed powder is pre-dried and crushed before use, and then ground to a particle size ≤0.075mm by a ball mill.

4. The morphology control method according to claim 1, characterized in that: During granulation, the disc granulator is tilted at an angle of 45~60° and rotates at a speed of 30~40 r / min.

5. The morphology control method according to claim 1, characterized in that: In step (6), the non-calcination curing process is selected from one or more of cold curing, carbonization curing, and steam curing.

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