CN114591013B - Artificial aggregate of river sludge and preparation method thereof - Google Patents

Abstract

The invention discloses a river sludge artificial aggregate and a preparation method thereof. The artificial aggregate has the following characteristics: the core-shell-type concrete composite material comprises, by mass, 10-15% of cement, 55-70% of river sludge, 9-25% of quartz tailings, 6-10% of fly ash, 1-3% of sodium carbonate doped with an activator and 1-3% of a shell layer component, wherein the core-shell-type concrete composite material comprises, by mass, 10-15% of the cement, 55-70% of the river sludge, 9-25% of the quartz tailings, and 1-3% of ground steel slag powder; secondly, the quartz tailings, the fly ash and the admixture are directly mixed according to the proportion and then are ball-milled to prepare a dry excitant, so that the excitability activity is ensured; thirdly, a highly automatic extrusion balling method is adopted, so that the balling efficiency is high and the cost is low; fourthly, the artificial aggregate is maintained by adopting a sintering-free hydrothermal synthesis process, and compared with the traditional clay sintered aggregate, the production mode can save energy by 80 percent. According to the method, quartz and clay components in river sludge are used for synthesizing Tobermorite (TOB) and pomegranate single click or click input characters at the position under the conditions that the temperature is 180-200 ℃ and the saturated vapor pressure is 1.0-1.5 MPa. Minerals, which makes the ceramic aggregate have the advantages of high strength and heat insulation.

Description

A kind of river silt artificial aggregate and preparation method thereof

technical field

The invention relates to a method for preparing sinter-free artificial aggregate by using river silt as a main raw material by extrusion molding, and belongs to the field of artificial aggregate for light-structure concrete.

Background technique

The river silt in the Yangtze River Basin is a kind of unconsolidated fine and soft particles that accumulate in large quantities in the Yangtze River Basin, especially in the middle and lower reaches. Its composition is extremely complex, including inorganic non-minerals, biological residues, organic precipitates and iron-magnesium colloids and more than ten kinds of components. As a common solid waste, the sedimentation of river sludge has many hazards. Taking the Yangtze River Delta region as an example, these sludges often lead to black and odorous water bodies, which seriously affects the development of local fisheries and agriculture. In addition, they also raise the position of the riverbed. , which increases the risk factor during the flood season, and even accumulates in key terrain, which affects the normal navigation of large ships and greatly reduces the shipping value of the Jiangnan water network. In order to deal with this serious problem, governments at all levels have organized and carried out dredging projects under the call of the national strategy for many times. These projects produce tens of millions of tons of silt every year and bring serious environmental pressure. Taking Taihu Lake in the lower reaches of the Yangtze River Basin as an example, the total area of Taihu Lake exceeds 2500km ³ , and the average deposition depth exceeds 0.5m. In 2007, the government issued the “Taihu Lake Water Pollution Control Plan” alone, which produced 30 million m ³ of silt.

In the face of the mountains of excavated river silt, how to better dispose of it has become an urgent problem. Commonly used methods include landfilling, agricultural utilization or as building materials, etc., all have great limitations. For example, direct landfilling covers an excessively large area, which is extremely likely to cause secondary pollution; used as farmland fertilizer or wetland backfill, silt The demand is too small, and the processing cycle is too long; as building materials, the current sintered wall bricks or swelled aggregates have high energy consumption, which does not conform to the national energy-saving strategy. Therefore, we urgently need a more worthy of promotion of silt resource utilization to solve the huge pressure on the environment caused by the current mass production of river silt.

In recent years, the introduction of new building material technology has brought new solutions to the efficient resource utilization of river silt. A large number of previous studies have shown that the mineral composition of dewatered river silt has many similarities with the clay produced by weathering. The generation of river silt is the result of the weathering of minerals in the upper reaches of the river, the weathering of surface sand and gravel and the deposition of fine particles downstream with rain, or the long-term erosion of rock and gravel in the river bed by water erosion. The product of this process is essentially clay, so the river silt is It has extremely high utilization value in the preparation of new building materials. The characteristics of clay minerals themselves also make their raw materials have a large plasticity index and good cohesion, which are suitable for industrial granulation into balls. At present, a large number of related researches mainly focus on the use of river silt to prepare new wall sintered bricks, or to replace shale to prepare sintered aggregates, etc. These methods can solve the problem of silt utilization to a certain extent, but their energy consumption is too high, exhaust gas Problems such as serious emissions and pollution limit the promotion and application of products.

SUMMARY OF THE INVENTION

The purpose of this invention is to provide a kind of artificial aggregate of river silt and preparation method thereof.

An artificial aggregate of river silt and a preparation method thereof, firstly, the calcium-silicon ratio of the raw material is controlled to be 0.18-0.32; secondly, the used river silt is dehydrated to a moisture content of 40±2% through preliminary pressure filtration, and no additional water is required in the molding process. According to the mass percentage of artificial aggregate, cement: river silt: quartz tailings: fly ash = 10-15: 55-70: 9-25: 6-10, of which, sodium carbonate is 1.0-3.0% by mass of artificial aggregate Incorporation in an additive manner involves the following six steps:

first step:

The dry quartz tailings, fly ash and admixture sodium carbonate are mixed according to the mixing ratio and then ground in a ball mill, and the fineness reaches 300 mesh and the sieve residue is less than 15%, thereby obtaining a dry activator for river silt;

Step 2:

Mix the three main raw materials, cement, river sludge (after dehydration by pressure filtration) and dry activator, and put them into a trough mixer specially designed for stirring viscous materials, and stir them thoroughly for 10-15 minutes. This process does not require additional water, and the mixture will be gradually enter a plastic state;

third step:

Pour the stirred plastic material into the rotary extrusion granulator, the material is slowly extruded from the bushing die with a diameter of 10cm, and after being interrupted by the external rotating blade, a 5-10mm long cylindrical section is obtained and falls into the In a disc balling machine that continuously rotates downstream;

the fourth step:

The ground steel slag powder and the cylindrical segment extruded from the rotary granulator in the third step are added to the rotating disc balling machine. In this process, the amount of steel slag added needs to be properly adjusted. The specific range is controlled at 6% to 10% of the mass of the artificial aggregate, and the steel slag powder is continuously added until the shell layer of the aggregate is completely formed, and the rolling is continued until it turns into a regular spherical shape, and then rolling 5-10min, when the aggregate surface is smooth and no adhesion, and the particle size of the pellets is 5-15mm, the granulation process is completed;

the fifth step:

The sludge aggregate after the above-mentioned cladding is placed in a cool place for natural conservation;

Step 6:

The material after natural curing is placed in an autoclave, and the continuous hydrothermal synthesis reaction is carried out under the conditions of temperature 180-200 ° C and saturated steam pressure 1.0-1.5 MPa, so that the internal calcium-silicon-aluminum water quaternary system is reacted. The artificial aggregate can be obtained by generating high temperature hydration phase tobermorite (TOB) and water garnet.

Preferably, in the third step, the drop height of the extruded cylindrical segment body should not be higher than 1m, which can be connected to the rotating disc-type ball-forming machine by an obliquely long trough.

Preferably, in the fifth step, the shelled material is placed in a cool place for natural curing for 24 hours.

Preferably, the fly ash is national first-class fly ash; the quartz tailings are tailings with a particle size smaller than 0.125mm produced by the magnetic separation process of quartz sand; The steel slag powder is a finely ground converter steel slag powder, the fineness is required to be 300 mesh, and the sieve residue is less than 15%.

Compared with the prior art, the present invention has the following advantages:

(1) In addition to cristobalite, the river silt also contains a large number of other minerals such as plagiochlorite, muscovite, and illite. These minerals are all typical clay minerals, have the unique surface adsorption and water swellability of clay, their plasticity index exceeds 12, and have very good ball-forming plasticity, and the artificial aggregate preparation process proposed by the present invention has a high degree of industrialization; (2) The silt artificial aggregate of the present invention has a regular spherical shape, high sphericity, and a concentrated distribution of particle diameters between 10 and 15 mm. Compared with irregularly shaped crushed stones, spherical aggregates can effectively improve the stress concentration of concrete under compression. The aggregate is in a uniform state of stress in the concrete, and the ultimate load is greatly improved, while the crushed stone is easy to form a stress concentration at the sharp corner edge and is subjected to multi-directional shear force, and the strength of the concrete decreases instead; (3) The raw materials used in the silt artificial aggregates of the present invention are industrial solid waste or tailings, and the acquisition cost is relatively low, and at the same time, a new idea is opened for solving the problem of solid waste accumulation; (4) The silt artificial aggregates of the present invention are The core-shell structure is formed by plastic kneading, extrusion granulation and steel slag powder water absorption to form a core-shell structure. The structural modification of the surface layer has two major advantages. One is to improve the stress structure of a single aggregate, and the point stress is evenly dispersed into surface stress to effectively prevent the problem of aggregate splitting under force, thereby improving the cylinder compressive strength of the aggregate itself. The second is to provide an active surface. A firm interface bonding force is generated between the aggregates, thereby eliminating the weak interface area of the concrete; (5) In the synthesis system of the clay material, the silt artificial aggregate of the present invention abandons the traditional sintering process and adopts the steaming process. Press synthesis process, and successfully prepared man-made silt aggregates that meet the national light aggregate specifications. The improvement of the process greatly reduces the production energy consumption of the present invention. Under the theoretical energy conversion rate, artificial aggregates of the same quality can be synthesized. Compared with the sintering process, the autoclaving process can reduce the energy consumption by 80%, which is in line with national energy conservation and emission reduction, and is green Sustainable long-term development strategy; (6) The performance of the silt artificial aggregate of the present invention is very excellent. The apparent density is lower than 1900kg/m ³ , the bulk density is lower than 1000kg/m ³ , and the cylinder compressive strength is between 16-22MPa. The 2h water absorption rate is 5-10%, and the mass loss of the freeze-thaw cycle is less than 5%. The firmness test results are rated as the national class I standard according to GB14685-2011 "Pebbles and Crushed Stones for Construction". (7) The silt artificial aggregate of the present invention has excellent thermal performance, and the thermal conductivity of ordinary crushed stone concrete is 1.71W/(m·K) under the same mixing ratio, and the concrete after the crushed stone is replaced by the same volume of silt aggregate The thermal conductivity is only 0.85W/(m·K), and the thermal insulation performance can be improved by 50%.

Description of drawings

Fig. 1 is the XRD analysis pattern of the river silt.

Figure 2 is a schematic diagram of the structure of tobermullite (TOB).

Figure 3 is a SEM of the tobermullite (TOB) crystal morphology.

Figure 4 is a SEM of the crystal morphology of water garnet.

Fig. 5 is a flow chart of the preparation of the artificial aggregate of river silt according to the present invention.

Detailed ways

In order to better understand the technical content of the present invention, specific embodiments are given and described below in conjunction with the accompanying drawings.

Aspects of the invention are described herein with reference to the accompanying drawings, in which embodiments of the invention are shown. Embodiments of the invention are not necessarily intended to include all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in greater detail below, can be implemented in any of a number of ways, as the concepts and embodiments disclosed herein do not limited to any implementation. Additionally, some aspects of the present disclosure may be used alone or in any suitable combination with other aspects of the present disclosure.

The artificial aggregate of the present invention has the following characteristics: firstly, the composition gradient contains two parts: the inner core and the shell layer, and the composition of the inner core is 10% to 15% of cement, 55% to 70% of river silt, and quartz tail. 9% to 25% of ore, 6% to 10% of fly ash, 1% to 3% of sodium carbonate as an external activator, and the shell composition is ground steel slag powder; the second is quartz tailings, fly ash and external admixtures The dry activator is prepared by ball milling after direct mixing according to the proportion, which ensures the activation activity; the third is the use of a highly automated extrusion method, which has high efficiency and low cost; the fourth is the use of a sinter-free hydrothermal synthesis process Compared with the traditional clay sintered aggregate, this production method can save energy by 80%.

The principle and design concept of the present invention are:

(1) The Yangtze River Delta region is located in the middle and lower reaches of the Yangtze River Basin. There are many tributaries of the Yangtze River with complex topography, and for a long time, a large amount of rock weathering has flowed into the river channel with rainwater. In addition, changes in agricultural production habits make it easier for river silt to accumulate in this area. The present invention develops and utilizes raw materials containing clay minerals by a hydrothermal synthesis process, and aims to reduce energy consumption and recover solid waste.

(2) Multi-system hydrothermal synthesis reaction

The EDS results of the river silt show that the main element is SiO ₂ , which accounts for more than 50% of the relative mass, and the total proportion of the remaining three elements, Al ₂ O ₃ , Fe ₂ O ₃ and MgO, reaches 30%. Combined with the XRD results, it can be seen that there are various phases such as cristobalite, clinochlorite, illite, and muscovite, among which clinochlorite, illite, and muscovite belong to clay minerals. The experimental results show that clay minerals are involved in the final phase. The hydrothermal synthesis reaction of the hydration system is a calcium-silicon-aluminum-oxygen quaternary reaction system. The main hydration products of the reaction are well-crystallized tobermorite (TOB) and water garnet. Among them, TOB is mainly generated by transition of CSH (B), TOB is CSH (B) with good crystalline state, with layered chain structure (Fig. 2), high strength, SEM is usually fibrous or needle-like (see Fig. 3) . The hydrated garnet is mainly synthesized from muscovite and clinochlorite in river silt as aluminum sources. Water garnet is octahedral particles in SEM (see Figure 4), and also has high strength, and the presence of a small amount can improve the strength of artificial aggregates.

(3) The sludge aggregate is prepared by the present invention, and the quartz tailings, fly ash and external admixture are mixed and ball-milled to prepare a dry activator, which can improve the mixing uniformity. Clay itself has fine particles, but because of its negative surface charge, it is easy to agglomerate with other particles, so it is not easy to disperse. This process can play a key role in regulating viscosity and controlling the efficiency of ball formation.

(4) The silt artificial aggregate of the present invention has a core-shell structure, the cladding component is ground steel slag powder, and the mass of the cladding ash accounts for 6-10% of the mass of the artificial aggregate. The cladding process can modify the surface structure of the aggregate, make the surface rough, and form an active interface, so that an active interface between the aggregate and the matrix is formed inside the concrete, which effectively prevents the cracks from spreading at the interface when the concrete is compressed.

(5) The silt artificial aggregate of the present invention adopts the extrusion molding method to prepare the silt aggregate, which makes full use of the characteristics of high viscoplasticity of river silt. Using this method to prepare artificial aggregate can greatly improve the preparation efficiency and molding uniformity, and the degree of industrialization is extremely high.

The present invention uses river silt as a raw material, carries out the preparation of silt artificial aggregates, tests the main mineral phases of the silt, and the XRD diffraction pattern shows (see Fig. 1) that the main phases are cristobalite and muscovite, illite, and oblique green mud. Clay non-metallic minerals such as stone.

The preparation process of the present invention will be described below with reference to FIG. 5 . The chemical composition of the raw materials used is shown in Table 1.

Table 1 Main chemical components of river silt, quartz tailings and fly ash (wt.%)

Example 1:

A silt artificial aggregate of the present invention, the specific mass ratio is: cement: river silt: quartz tailings: fly ash = 15:70:9:6; sodium carbonate dosage 3.0wt% (calcium-silicon ratio 0.23 ), and its specific preparation process comprises the following steps:

first step:

90kg of dry quartz tailings, 60kg of fly ash and 30kg of sodium carbonate are mixed according to the coordination and then placed in a ball mill for grinding, and the sieve residue of the 300-mesh raw material is less than 15%, thereby obtaining a dry activator for river silt;

Step 2:

Weigh 150kg of cement, 700kg of river silt (after dehydration by filter press), and 150kg of dry activator, and put them into a tank mixer specially designed for stirring viscous materials, and stir them fully for 10 minutes. No additional water is needed in this process, and the mixture will gradually enter plastic state;

third step:

Pour the stirred plastic material into the rotary extrusion granulator, the material is slowly extruded from the bushing die with a diameter of 10cm, and after being interrupted by the external rotating blade, a cylindrical section with a length of 5-10mm is obtained and falls into the In a disc balling machine that continuously rotates downstream;

the fourth step:

Add 60kg of ground steel slag powder together with the cylindrical section extruded from the third-step rotary granulator into the rotating disc balling machine, continue to add steel slag powder until the shell layer of the aggregate is completely formed, and continue to roll until it becomes regular After rolling for 10 minutes, the granulation process is completed when the surface of the aggregate is smooth and there is no adhesion, and the particle size of the pellet is 5-15mm;

the fifth step:

The sludge aggregate after the above-mentioned cladding is placed in a cool place for natural conservation;

Step 6:

The material after natural curing was placed in an autoclave, and the continuous hydrothermal synthesis reaction was carried out for 10 hours under the conditions of a temperature of 180 ° C and a saturated vapor pressure of 1.0 MPa, so that the internal calcium-silicon-aluminum water quaternary system was reacted to generate a high-temperature hydration phase. Bermulite (TOB) and water garnet can obtain the artificial aggregate.

The artificial aggregate prepared by this example has a 2h water absorption rate of 9.1%, an apparent density of 1.79g/cm ³ , a cylinder compressive strength of 18.8MPa, a softening coefficient of 0.87, and a freeze-thaw cycle mass loss of only 0.4%, reaching the national construction level The frost resistance standard of the aggregate; the mass loss of the solidity test is -1.3%, reaching the national class I standard of the solidity of the aggregate for construction.

Example 2:

A silt artificial aggregate of the present invention, the specific mass ratio is: cement: river silt: quartz tailings: fly ash = 10:55:25:10; sodium carbonate dosage 1.0wt% (calcium-silicon ratio 0.25 ) its specific preparation process comprises the following steps:

first step:

Mix 250kg of dry quartz tailings, 100kg of fly ash and 10kg of sodium carbonate according to the coordination and then place them in a ball mill for grinding, and the fineness of the raw materials is less than 15% of 300 mesh sieves, thereby obtaining a dry activator for river silt;

Step 2:

Weigh 100kg of cement, 550kg of river silt (after dehydration by filter press), and 350kg of dry activator, and put them into a trough mixer specially designed for stirring viscous materials, and stir them fully for 15 minutes. No additional water is required in this process, and the mixture will gradually enter plastic state;

third step:

Pour the stirred plastic material into the rotary extrusion granulator, the material is slowly extruded from the bushing die with a diameter of 10cm, and after being interrupted by the external rotating blade, a cylindrical section with a length of 5-10mm is obtained and falls into the In a disc balling machine that continuously rotates downstream;

the fourth step:

Add 100kg of ground steel slag powder and the cylindrical section extruded from the third-step rotary granulator into the rotating disc balling machine, continue to add steel slag powder until the shell of the aggregate is completely formed, and continue to roll until it turns into a regular Then roll for 5 minutes, and complete the granulation process when the surface of the aggregate is smooth and without adhesion, and the particle size of the pellet is 5-15mm;

the fifth step:

The sludge aggregate after the above-mentioned cladding is placed in a cool place for natural conservation;

Step 6:

The material after natural curing was placed in an autoclave, and the continuous hydrothermal synthesis reaction was carried out for 10 hours under the conditions of temperature of 200 ° C and saturated vapor pressure of 1.5 MPa, so that the internal calcium-silicon-aluminum water quaternary system was reacted to form a high-temperature hydration phase. Bermulite (TOB) and water garnet can obtain the artificial aggregate.

The artificial aggregate prepared by this example has a 2h water absorption rate of 8.9%, an apparent density of 1.85g/cm ³ , a cylinder compressive strength of 18.5MPa, a softening coefficient of 0.91, and a freeze-thaw cycle mass loss of only 1.28%, reaching the national construction level. The frost resistance standard of the aggregate; the mass loss of the solidity test is -4.9%, which reaches the national class I standard of the solidity of the aggregate for construction.

Example 3:

A silt artificial aggregate of the present invention, the specific mass ratio is: cement: river silt: quartz tailings: fly ash = 12:63:17:8, sodium carbonate dosage 2.0% (calcium-silicon ratio 0.27) , and its specific preparation process includes the following steps:

first step:

Mix 170kg of dry quartz tailings, 80kg of fly ash and 20kg of sodium carbonate according to the coordination and then place them in a ball mill to grind, and the sieve residue of the raw material fineness of 300 meshes is less than 15%, thereby obtaining a dry activator for river silt;

Step 2:

Weigh 120kg of cement, 630kg of river silt (after filter press dehydration), and 250kg of dry activator, put them into a tank mixer specially designed for stirring viscous materials, and stir them thoroughly for 12 minutes. This process does not require additional water, and the mixture will gradually enter plastic state;

third step:

Pour the stirred plastic material into the rotary extrusion granulator, the material is slowly extruded from the bushing die with a diameter of 10cm, and after being interrupted by the external rotating blade, a cylindrical section with a length of 5-10mm is obtained and falls into the In a disc balling machine that continuously rotates downstream;

the fourth step:

Add 80kg of ground steel slag powder together with the cylindrical section extruded from the third-step rotary granulator into the rotating disc balling machine, continue to add steel slag powder until the shell layer of the aggregate is completely formed, and continue to roll until it becomes regular After rolling for 8 minutes, the granulation process is completed when the surface of the aggregate is smooth and there is no adhesion, and the particle size of the pellet is 5-15mm;

the fifth step:

The sludge aggregate after the above-mentioned cladding is placed in a cool place for natural conservation;

Step 6:

The material after natural curing was placed in an autoclave, and the continuous hydrothermal synthesis reaction was carried out for 10 hours under the conditions of a temperature of 180 ° C and a saturated vapor pressure of 1.0 MPa, so that the internal calcium-silicon-aluminum water quaternary system was reacted to generate a high-temperature hydration phase. Bermulite (TOB) and water garnet can obtain the artificial aggregate.

The artificial aggregate prepared by this example has a 2h water absorption rate of 9.9%, an apparent density of 1.86g/cm3, a cylinder compressive strength of 21.9MPa, a softening coefficient of 0.95, and a freeze-thaw cycle mass loss of only 0.4%, which is suitable for national construction. Aggregate frost resistance standard; solidity test mass loss -1.3%, reaching the national construction aggregate solidity class I standard.

Comparative Example 4:

In this comparative example, artificial aggregates are prepared by selecting a scheme other than the reasonable ratio and ratio proposed by the present invention, which is in sharp contrast with Examples 1-3. The specific mass ratio is: cement: river silt: quartz tailings: fly ash = 14:80:3:3, sodium carbonate dosage is 3.5%, and the specific preparation process is the same as in Examples 1-3.

The artificial aggregate prepared by this comparative example has a 2-h water absorption rate of 12.9% and an apparent density of 1.81g/cm ³ ; the cylinder compressive strength is only 14.5MPa, and the softening coefficient is only 0.75, which is lower than the qualified standard of 0.8; the freeze-thaw cycle and the firmness test are not up to standard; the aggregate is prone to cracking under autoclave, and the above properties do not meet the production and preparation requirements.

Example 5:

The artificial silt aggregate in Example 1 is used to prepare concrete, and the mix ratio design comprehensively refers to "Technical Specification for Lightweight Aggregate Concrete" JGJ 51-2002 and "Ordinary Concrete Mix Ratio Design Specification" JGJ 55-2011, which is used as aggregate A concrete test block was prepared, and at the same time, the sludge aggregate was replaced with an equal volume of crushed stone, and various properties were compared under the same mixing ratio. The experimental coordination ratio is shown in the following table:

Table 2 Design mix ratio of artificial aggregate-gravel concrete comparative experiment

Table 3 Comparative experimental results of artificial aggregate-crushed stone concrete

In this example, the apparent density of the light aggregate concrete prepared by using the silt aggregate is 2034.4kg/m ³ , which is only 84.4% of the apparent density of the ordinary gravel concrete, and the effect of reducing the self-weight is very obvious; the silt aggregate concrete The 28d compressive strength can reach 69.8MPa, which is higher than that of ordinary gravel concrete, and the engineering performance is better; the thermal conductivity of silt aggregate concrete is only 0.85 W/(m·K), compared with ordinary gravel concrete, thermal insulation Thermal performance increased by 50%.

The invention makes full use of the phases of cristobalite, illite, muscovite, clinochlorite and the like contained in the river silt, and adopts technologies such as stirring into a ball method and cladding modification in the molding process to improve the uniformity of molding; The high-temperature hydration phase tobermullite (TOB) (see Figure 3) and water garnet (see Figure 4) were synthesized through the quaternary hydration reaction of calcium-silicon-alumina water to improve the strength of the aggregates, and finally a porous, porous material with both strength was prepared. New man-made aggregates with properties and thermal insulation properties. The scheme for recovering river silt in the present invention is also applicable to typical slag construction wastes such as shield slag, foundation pit slag and drilling slag produced by engineering construction in the Yangtze River Basin.

The method utilizes dewatered river silt to prepare artificial aggregates, adjusts the mixing ratio, mixes various siliceous materials, and adopts a hydrothermal synthesis process, which not only improves the mechanical properties of artificial aggregates, but also reduces production energy consumption. Therefore, the biggest advantage of the technology of the present invention is that it can industrially and intensively process the river silt, and at the same time, it can produce artificial aggregates with high added value, thereby generating double economic benefits. The artificial aggregate prepared with the patent of the present invention can be fully adapted to LC60 high-grade lightweight aggregate concrete, not only has high compressive strength, but also has very good thermal performance, which is of great significance for the resource utilization of river silt.

Claims (5)

1. The preparation method of the artificial aggregate of the river sludge is characterized in that the raw materials comprise the following cement in percentage by mass: river sludge: quartz tailings: fly ash = 10-15: 55-70: 9-25: 6-10, wherein sodium carbonate is doped in an additional mode according to the mass of 1.0-3.0% of the artificial aggregate, and the calcium-silicon ratio of the raw materials is controlled to be 0.18-0.32; performing preliminary filter pressing and dehydration on the river sludge until the water content is 40 +/-2%; comprises the following six steps:

the first step is as follows:

mixing the dried quartz tailings, the fly ash and the sodium carbonate according to the mixing proportion, and then placing the mixture into a ball mill for grinding until the fineness reaches 300 meshes and the residual is less than 15 percent to obtain the dryness excitant of the river sludge;

the second step:

mixing three main raw materials of cement, river silt and a dry activator, putting the mixture into a trough type mixer, and fully stirring for 10-15 min, wherein no additional water is needed in the process, and the mixed materials gradually enter a plastic state;

the third step:

pouring the material stirred in the second step into a rotary extrusion granulator, slowly extruding the material to obtain a cylindrical section body with the length of 5-10mm, and dropping the cylindrical section body into a continuously rotating disc granulator positioned at the downstream;

the fourth step:

adding the ground steel slag powder and the cylindrical section body in the third step into a rotary disc type granulator together, wherein the using amount of the ground steel slag powder is 6% -10% of the mass of the artificial aggregate, continuously adding the steel slag powder until a shell layer of the aggregate is completely formed, continuously rolling until the shell layer of the aggregate is changed into a regular spherical shape, then rolling for 5-10 min, and finishing the granulation process when the surface of the aggregate is smooth and is not adhered, and the particle size of a material ball is 5-15 mm;

the fifth step:

placing the covered sludge aggregate in a shade place for natural curing;

and a sixth step:

and (3) placing the naturally cured material in an autoclave, carrying out continuous hydrothermal synthesis reaction for 8-10 h under the conditions that the temperature is 180-200 ℃ and the saturated vapor pressure is 1.0-1.5 MPa, and reacting an internal calcium-silicon-aluminum water quaternary system to generate high-temperature hydrated phase tobermorite and water garnet, so as to obtain the artificial aggregate.

2. The method according to claim 1, wherein in the third step the drop height of the extruded cylindrical section is not higher than 1 m.

3. The method as claimed in claim 1, wherein in the fifth step, the encrusted material is naturally cured in a shade for 24 hours.

4. The method of claim 1, wherein the fly ash is national grade fly ash; the quartz tailings are tailings with the particle size of less than 0.125mm generated by a quartz sand magnetic separation process; the cement is ordinary portland cement with the label PII 52.5; the ground steel slag powder is ground converter steel slag powder, the fineness requirement is 300 meshes, and the screen residue is less than 15%.

5. The river sludge artificial aggregate prepared by the method as claimed in any one of claims 1 to 4.

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