CN114591013B - Artificial aggregate of river sludge and preparation method thereof - Google Patents
Artificial aggregate of river sludge and preparation method thereof Download PDFInfo
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- CN114591013B CN114591013B CN202210232296.4A CN202210232296A CN114591013B CN 114591013 B CN114591013 B CN 114591013B CN 202210232296 A CN202210232296 A CN 202210232296A CN 114591013 B CN114591013 B CN 114591013B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/02—Agglomerated materials, e.g. artificial aggregates
- C04B18/021—Agglomerated materials, e.g. artificial aggregates agglomerated by a mineral binder, e.g. cement
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/10—Coating or impregnating
- C04B20/1055—Coating or impregnating with inorganic materials
- C04B20/1074—Silicates, e.g. glass
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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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
Technical Field
The invention relates to a method for preparing a sintering-free artificial aggregate by using river sludge as a main raw material and adopting an extrusion molding method, belonging to the field of artificial aggregates for lightweight structural concrete.
Background
The sludge in the Yangtze river basin is a large amount of silted and unconsolidated fine and soft particles in the river reach of the Yangtze river basin, particularly in the middle and lower reaches. The extremely complex components comprise more than ten components such as inorganic non-mineral, biological residues, organic precipitates, iron-containing magnesium colloid and the like. As a common solid waste, the silting of river sludge has various hazards, and in the case of the Yangtze river area, the sludge often causes black and odorous water bodies to seriously affect the development of local fishery and agriculture, and in addition, the sludge can also raise the quality of the water bodiesThe high river bed position improves the flood season danger coefficient, silts up even in key topography, influences large-scale ship normal navigation, significantly compromises the value of shipping of the south of the Yangtze river water network. To cope with this severe problem, governments at all levels have been under the call of national strategies to organize dredging projects many times, which generate millions of tons of sludge each year with serious environmental stress. Taking the Taihu lake downstream of the Yangtze river basin as an example, the total area of the Taihu lake exceeds 2500km 3 Average silting depth exceeds 0.5m, and 3000 ten thousand m is generated only by a project of 'Taihu lake water pollution control scheme' issued by 2007 government 3 Sludge.
In the face of the accumulation of the sludge in the river channel excavated like a mountain, how to better dispose the sludge becomes an urgent problem. The common method comprises landfill stacking, agricultural utilization or as a building raw material and the like, which have great limitations, such as overlarge occupied area due to direct landfill stacking and extremely easy secondary pollution; the sludge is used as farmland fertilizer or wetland backfill, the demand of the sludge is too small, and the treatment period is too long; as a building raw material, the prior sintered wall brick or the sintered aggregate has high energy consumption and does not meet the national energy-saving strategy. Therefore, a sludge resource utilization mode which is more worthy of popularization is urgently needed to solve the problem that the environment is greatly stressed by the river sludge which is produced in large quantities at present.
In recent years, the new building material technology is proposed to provide a new solution for the efficient resource utilization of river sludge. A number of prior studies have shown that the mineral content of dewatered river sludge has many similarities to weathered clays. The river sludge is generated as a result of weathered mountain minerals, weathered earth surface sands and stones and weathered fine particles which are washed by rainwater at the upstream of the river and deposited at the downstream, or rock sands and gravels in the river bed are washed and eroded by water flow for a long time, and the product of the process is essentially clay, so the river sludge has extremely high utilization value in the aspect of preparing novel building materials. The clay mineral has the characteristics of large plasticity index of raw materials and good caking property, and is suitable for industrial granulation and balling. At present, a great deal of related research mainly focuses on preparing novel wall body sintered bricks by using river sludge or preparing sintered aggregates by replacing shale and the like, and the methods can solve the problem of sludge utilization to a certain extent, but the problems of overhigh energy consumption, serious tail gas emission pollution and the like limit the popularization and application of products.
Disclosure of Invention
The invention aims to provide a river sludge artificial aggregate and a preparation method thereof.
Firstly, controlling the calcium-silicon ratio of raw materials to be 0.18-0.32; secondly, the river sludge is subjected to preliminary filter pressing dehydration until the water content is 40 +/-2%, no additional water is required in the forming process, the concrete proportion is calculated according to the mass percent of the artificial aggregate, and the cement: river sludge: quartz tailings: 10-15% of fly ash: 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 method comprises the following six steps:
the first step is as follows:
mixing the dried quartz tailings, the fly ash and the admixture sodium carbonate according to a mixing ratio, and then placing the mixture into a ball mill for grinding until the fineness reaches 300 meshes and the residual is less than 15%, thereby obtaining the dry excitant for the river sludge;
the second step is that:
mixing three main raw materials of cement, river silt (after filter pressing and dehydration) and a dry activator, putting the mixture into a trough type mixer special for stirring viscous materials, 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 stirred plastic material into a rotary extrusion granulator, slowly extruding the material from a bushing mould with the diameter of 10cm, cutting the material by an external rotating blade 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 extruded by the rotary granulator in the third step into a rotary disc granulator together, wherein the addition amount of the steel slag needs to be properly regulated and controlled in the process, the addition amount of the ground steel slag powder is determined according to the rolling water yield of the cylindrical section body, the specific range is controlled to be 6% -10% of the mass of the artificial aggregate, the steel slag powder is continuously added until a shell layer of the aggregate is completely molded, the aggregate is continuously rolled until the shell layer is changed into a regular spherical shape, then the aggregate is rolled for 5-10 min until the surface of the aggregate is smooth and is not adhered, and the granulation process is completed when 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, and carrying out continuous hydro-thermal 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, so that the internal calcium-silicon-aluminum water quaternary system reacts to generate high-temperature hydrated phase Tobermorite (TOB) and garnet, and the artificial aggregate can be obtained.
Preferably, in the third step, the falling height of the extrusion cylindrical segment body is not higher than 1m, and the extrusion cylindrical segment body can be connected into a rotary disc type ball forming mill by an inclined long material groove.
Preferably, in the fifth step, the materials after being wrapped are placed in a shade and naturally maintained for 24 hours.
Preferably, the fly ash is national first-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%.
Compared with the prior art, the invention has the following advantages:
(1) river sludge contains a large amount of other minerals such as clinopodium, muscovite, illite and the like besides cristobalite. The minerals belong to typical clay minerals, have unique surface adsorbability and water absorption expansibility of clay, have a plasticity index of over 12 and very good balling plasticity, and the preparation process of the artificial aggregate provided by the invention has high industrialization degree; (2) the sludge artificial aggregate is regular spherical in shape, high in sphericity and concentrated in particle size distribution of 10-15 mm. Compared with the irregular-shaped broken stone for the building, the spherical aggregate can effectively improve the stress concentration problem when concrete is pressed. The aggregate is coagulatedStress in soil is in various uniform states, the ultimate load is greatly improved, and broken stones are easy to form stress concentration at sharp-angled edges so as to be subjected to multidirectional shearing force, so that the concrete strength is reduced on the contrary; (3) the raw materials used by the artificial sludge aggregate are all industrial solid wastes or tailings, the acquisition cost is low, and a brand-new idea is developed for solving the problem of solid waste accumulation; (4) the artificial sludge aggregate is prepared by plastic kneading, extrusion granulation and steel slag powder water absorption and shell forming through a groove type mixer to form a core-shell structure, and the structural modification of the surface layer has two advantages. Firstly, the stress structure of a single aggregate is improved, the point stress is uniformly dispersed into the surface stress, and the problem of stress splitting of the aggregate is effectively prevented, so that the barrel pressure strength of the aggregate is improved, and secondly, an active surface is provided, firm interface binding force is generated between a concrete matrix and the aggregate, so that an interface weak area of the concrete is eliminated; (5) the artificial sludge aggregate provided by the invention is in a synthesis system of clay materials, the traditional sintering process is abandoned, the autoclaved synthesis process is adopted, and the artificial sludge aggregate meeting the national light aggregate specification is successfully prepared. The improvement of the process greatly reduces the production energy consumption, the artificial aggregate with the same quality is synthesized under the theoretical energy conversion rate, and the steam-pressing process can reduce the energy consumption by 80 percent compared with the sintering process, thereby conforming to the national long-term development strategy of energy conservation and emission reduction and being green and sustainable; (6) the artificial sludge aggregate has excellent performance. Its apparent density is lower than 1900kg/m 3 Bulk density of less than 1000kg/m 3 The cylinder pressure strength is 16-22 MPa. The water absorption rate is 5-10% after 2 hours, the mass loss of freeze-thaw cycles is less than 5%, and the firmness test result is evaluated as the national class I standard according to GB14685-2011 pebble and gravel for construction. (7) The sludge artificial aggregate has excellent thermal performance, the heat conductivity coefficient of common gravel concrete is 1.71W/(m.K) under the same mixing proportion, and the heat conductivity coefficient of concrete after replacing gravel by sludge aggregate with the same volume is only 0.85W/(m.K), compared with the heat insulation performance which can be improved by 50%.
Drawings
Fig. 1 is an XRD analysis spectrum of river sludge.
Fig. 2 is a schematic structural view of Tobermorite (TOB).
Fig. 3 is a SEM of Tobermorite (TOB) crystal morphology.
Fig. 4 is a SEM of the crystal morphology of the guava.
FIG. 5 is a flow chart of the preparation of the artificial aggregate from river sludge according to the invention.
Detailed Description
In order to better understand the technical content of the invention, specific embodiments are specifically enumerated and described below with reference to the accompanying drawings.
Aspects of the present 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 appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any one 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 invention has the following characteristics: the composite material comprises two parts of an inner core and a shell layer on a component gradient, wherein the inner core comprises 10-15% of cement, 55-70% of river sludge, 9-25% of quartz tailings, 6-10% of fly ash and 1-3% of sodium carbonate doped with an exciting agent by mass ratio, and the shell layer comprises 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; and fourthly, the artificial aggregate is cured 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.
The principle and design concept of the invention are as follows:
(1) the Yangtze river region is located in the middle and lower reaches of the Yangtze river basin, the Yangtze river branches have various complex terrains, a large amount of rock weathers flow into a river channel along with rainwater for a long time, and in addition, the change of agricultural production habits is added, so that the sludge of the river channel is easy to deposit in the region. The invention develops and utilizes the raw material of clay-containing minerals by a hydrothermal synthesis process, and aims to reduce energy consumption and recover solid wastes.
(2) Multi-system hydrothermal synthesis reaction
EDS results of river sludge show that the main element is SiO 2 The relative mass ratio of the Al to the Al exceeds 50 percent, and the rest is Al 2 O 3 、Fe 2 O 3 The total proportion of the three elements of MgO reaches 30 percent. According to XRD results, various phases such as cristobalite, chlorite, illite, muscovite and the like exist in the hydration system, wherein the chlorite, the illite and the muscovite belong to clay minerals, and experimental results show that the clay minerals participate in the final hydrothermal synthesis reaction, and the hydration system is a calcium-silicon-aluminum-oxygen quaternary reaction system. The main hydration products of the reaction are Tobermorite (TOB) and guava, which crystallize well. Wherein TOB is mainly generated by transition of CSH (B), TOB is CSH (B) with good crystalline state, has a layer chain structure (figure 2) and higher strength, and SEM is generally in a fiber shape or a needle shape (figure 3). The hydrated garnet is mainly synthesized by taking muscovite and chlorite in river sludge as an aluminum source. Water garnet is octahedral particles in the SEM (see fig. 4), also having a higher strength, and when present in small amounts can increase the strength of the artificial aggregate.
(3) The sludge aggregate is prepared by mixing and ball-milling quartz tailings, fly ash and an additive to prepare the dry excitant, so that the mixing uniformity can be improved. The clay itself is fine in particle but is not easily dispersed because it has surface electronegativity and is easily agglomerated with other particles. The process can play a key role in regulating and controlling viscosity and controlling balling efficiency.
(4) The artificial sludge aggregate has a core-shell structure, the cladding components are ground steel slag powder, and the cladding gray matter accounts for 6-10% of the mass of the artificial aggregate. The surface structure of the aggregate can be modified in the cladding process, so that the surface of the aggregate is rough, an active interface is formed, an aggregate-matrix active interface is formed in the concrete, and the unstable diffusion of cracks at the interface when the concrete is pressed is effectively prevented.
(5) The artificial sludge aggregate is prepared by an extrusion molding method, and the characteristic of high viscoplasticity of the river sludge is fully utilized. The method for preparing the artificial aggregate can greatly improve the preparation efficiency and the molding uniformity, and has extremely high industrialization degree.
The preparation method takes the river sludge as a raw material, carries out the preparation of the artificial sludge aggregate, tests the main mineral phases of the sludge, and XRD diffraction patterns show that the main mineral phases are cristobalite, muscovite, illite, clinopodium pumilum and other clay nonmetallic minerals (see figure 1).
The preparation process of the present invention is described below with reference to fig. 5. The chemical composition of the raw materials used is shown in table 1.
Table 1 main chemical composition (wt.%) of river silt, quartz tailings and fly ash
Example 1:
the artificial sludge aggregate comprises the following components in percentage by mass: cement: river sludge: quartz tailings: 15 parts of fly ash: 70: 9: 6; the sodium carbonate mixing amount is 3.0 wt% (calcium-silicon ratio is 0.23), and the specific preparation process comprises the following steps:
the first step is as follows:
mixing 90kg of dried quartz tailings, 60kg of fly ash and 30kg of sodium carbonate according to a formula, and then grinding in a ball mill, wherein the fineness of raw materials is 300 meshes, and the residual is less than 15%, so as to obtain a dry excitant for river sludge;
the second step:
weighing 150kg of cement, 700kg of river silt (after filter pressing and dehydration) and 150kg of dry excitant, mixing and putting into a trough type mixer special for stirring viscous materials, fully stirring for 10min, wherein no additional water is needed in the process, and the mixed materials gradually enter a plastic state;
the third step:
pouring the stirred plastic material into a rotary extrusion granulator, slowly extruding the material from a bushing mould with the diameter of 10cm, cutting the material by an external rotating blade to obtain a cylindrical section body with the length of 5-10mm, and dropping the cylindrical section body into a disk granulator which continuously rotates at the downstream;
the fourth step:
adding 60kg of ground steel slag powder and the cylindrical section extruded by the rotary granulator in the third step into a rotary disc granulator together, continuously adding the steel slag powder until the shell layer of the aggregate is completely formed, continuously rolling until the shell layer is changed into a regular spherical shape, then rolling for 10min, and finishing the granulation process when the surface of the aggregate is smooth and has no adhesion, wherein the grain size of the material balls is 5-15 mm;
the fifth step:
placing the jacketed sludge aggregate in a shade place for natural curing;
and a sixth step:
and (3) placing the naturally cured material into a still kettle, and carrying out continuous hydrothermal synthesis reaction for 10 hours at the temperature of 180 ℃ and under the saturated vapor pressure of 1.0MPa to enable the internal calcium-silicon-aluminum-water quaternary system to react to generate high-temperature hydrated phase Tobermorite (TOB) and hydrogarnet, thus obtaining the artificial aggregate.
The artificial aggregate prepared by the embodiment has the water absorption of 9.1 percent after 2 hours and the apparent density of 1.79g/cm 3 (ii) a The cylinder pressure strength reaches 18.8MPa, and the softening coefficient is 0.87; the mass loss of the freeze-thaw cycle is only 0.4 percent, and the freeze resistance standard of the aggregate for national buildings is achieved; the quality loss of the firmness test is-1.3 percent, and the firmness of the aggregate for national buildings reaches the I-type standard.
Example 2:
the invention relates to artificial sludge aggregate which comprises the following components in percentage by mass: cement: river sludge: quartz tailings: 10 of fly ash: 55: 25: 10; the sodium carbonate mixing amount is 1.0 wt% (calcium-silicon ratio is 0.25), and the specific preparation process comprises the following steps:
the first step is as follows:
mixing 250kg of dried quartz tailings, 100kg of fly ash and 10kg of sodium carbonate according to a formula, and then grinding the mixture in a ball mill, wherein the fineness of the raw materials is 300 meshes, and the residual is less than 15%, so as to obtain the dry excitant for the sludge in the river;
the second step:
weighing 100kg of cement, 550kg of river silt (after filter pressing and dehydration) and 350kg of dry activator, mixing, putting into a trough type mixer special for stirring viscous materials, fully stirring for 15min, adding no additional water in the process, and gradually putting the mixed materials into a plastic state;
the third step:
pouring the stirred plastic material into a rotary extrusion granulator, slowly extruding the material from a bushing mould with the diameter of 10cm, cutting the material by an external rotating blade to obtain a cylindrical section body with the length of 5-10mm, and falling the cylindrical section body into a disc type granulator which continuously rotates at the downstream;
the fourth step:
adding 100kg of ground steel slag powder and the cylindrical section extruded by the rotary granulator in the third step into a rotary disc granulator, continuously adding the steel slag powder until the shell layer of the aggregate is completely formed, continuously rolling until the shell layer is changed into a regular spherical shape, then rolling for 5min, and finishing the granulation process when the surface of the aggregate is smooth and has no adhesion, wherein the particle size of material balls 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 into a still kettle, and carrying out continuous hydrothermal synthesis reaction for 10 hours at the temperature of 200 ℃ and under the saturated vapor pressure of 1.5MPa to enable the internal calcium-silicon-aluminum-water quaternary system to react to generate high-temperature hydrated phase Tobermorite (TOB) and hydrogarnet, thus obtaining the artificial aggregate.
The artificial aggregate prepared by the embodiment has the water absorption rate of 8.9 percent in 2 hours and the apparent density of 1.85g/cm 3 (ii) a The cylinder pressure strength reaches 18.5MPa, and the softening coefficient is 0.91; the mass loss of the freeze-thaw cycle is only 1.28 percent, and the freeze resistance standard of the aggregate for national buildings is achieved; the quality loss of the firmness test is-4.9 percent, and the firmness of the aggregate for national buildings reaches the I-type standard.
Example 3:
the invention relates to artificial sludge aggregate which comprises the following components in percentage by mass: cement: river sludge: quartz tailings: 12 parts of fly ash: 63: 17: and 8, the mixing amount of sodium carbonate is 2.0 percent (the calcium-silicon ratio is 0.27), and the specific preparation process comprises the following steps:
the first step is as follows:
according to the formula, 170kg of dried quartz tailings, 80kg of fly ash and 20kg of sodium carbonate are mixed and then are put into a ball mill for grinding, and the fineness of the raw materials is 300 meshes, and the residual is less than 15%, so that the drying activator for the sludge in the river channel is obtained;
the second step is that:
weighing 120kg of cement, 630kg of river silt (after filter pressing and dehydration) and 250kg of dry activator, mixing, putting into a trough mixer special for stirring viscous materials, fully stirring for 12min, adding no additional water in the process, and gradually putting the mixed materials into a plastic state;
the third step:
pouring the stirred plastic material into a rotary extrusion granulator, slowly extruding the material from a bushing mould with the diameter of 10cm, cutting the material by an external rotating blade to obtain a cylindrical section body with the length of 5-10mm, and dropping the cylindrical section body into a disk granulator which continuously rotates at the downstream;
the fourth step:
adding 80kg of ground steel slag powder and the cylindrical section extruded by the rotary granulator in the third step into a rotary disc granulator together, continuously adding the steel slag powder until the shell layer of the aggregate is completely formed, continuously rolling until the shell layer is changed into a regular spherical shape, then rolling for 8 min, and finishing the granulation process when the surface of the aggregate is smooth and has no adhesion, wherein the grain size of the material balls 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, and carrying out continuous hydrothermal synthesis reaction for 10 hours at the temperature of 180 ℃ and under the saturated vapor pressure of 1.0MPa to enable the internal calcium-silicon-aluminum water quaternary system to react to generate high-temperature hydrated phase Tobermorite (TOB) and garnet, thus obtaining the artificial aggregate.
The artificial aggregate prepared by the embodiment has water absorption of 9.9 percent for 2 hours and apparent density of 1.86g/cm 3; the cylinder pressure strength reaches 21.9MPa, and the softening coefficient is 0.95; the mass loss of the freeze-thaw cycle is only 0.4 percent, and the freeze resistance standard of the aggregate for national buildings is achieved; the quality loss of the firmness test is-1.3 percent, and the firmness of the aggregate reaches the I-type standard of the firmness of the national building aggregate.
Comparative example 4:
the artificial aggregate is prepared by the reasonable proportioning and selecting scheme provided by the invention, and is in sharp contrast with the examples 1-3. The concrete mass ratio is as follows: cement: river sludge: quartz tailings: 14 parts of fly ash: 80: 3: 3, the mixing amount of sodium carbonate is 3.5 percent, and the specific preparation process is the same as that of the embodiment 1-3.
The artificial aggregate prepared by the comparative example has the water absorption rate of 12.9 percent in 2 hours and the apparent density of 1.81g/cm 3 (ii) a The cylinder pressure strength is only 14.5MPa, the softening coefficient is only 0.75, and the softening coefficient is lower than the qualified standard of 0.8; the freeze-thaw cycle and the firmness test do not reach the standard; the aggregate is easy to crack by autoclaving, and the performances do not meet the production and preparation requirements.
Example 5:
the artificial sludge aggregate in the example 1 is used for trial preparation of concrete, the mix proportion design is comprehensively referred to light aggregate concrete technical specification JGJ 51-2002 and common concrete mix proportion design specification JGJ 55-2011, the artificial sludge aggregate is used as an aggregate to prepare a concrete test block, meanwhile, the sludge aggregate is replaced by the crushed stone with the same volume, and various performances are compared under the same mix proportion. The experimental formulations are shown in the following table:
TABLE 2 artificial aggregate-gravel concrete comparison experiment design mix proportion
TABLE 3 Artificial aggregate-crushed stone concrete comparative experiment results
The apparent density of the lightweight aggregate concrete prepared by using the sludge aggregate in this example was 2034.4kg/m 3 Is only equivalent to 84.4 percent of the apparent density of the common crushed stone concreteThe effect of self weight reduction is very obvious; the 28d compressive strength of the sludge aggregate concrete can reach 69.8MPa, but is higher than that of the common crushed stone concrete, so that the engineering performance is better; the heat conductivity coefficient of the sludge aggregate concrete is only 0.85W/(m.K), and compared with the common crushed stone concrete, the heat insulation performance is improved by 50 percent.
According to the invention, the phases of cristobalite, illite, muscovite, clinopodium chlorite and the like contained in the river sludge are fully utilized, and the molding uniformity is improved by adopting a stirring balling method, a cladding modification technology and other technologies on the molding process; in the maintenance process, the high-temperature hydration phase Tobermorite (TOB) (shown in figure 3) and the garnet (shown in figure 4) are synthesized through the calcium-silicon-aluminum water quaternary hydration reaction to improve the strength of the aggregate, and finally the novel artificial aggregate with the strength, the porous characteristic and the heat preservation and insulation characteristic is prepared. The scheme for recovering the river sludge is also suitable for typical dregs building wastes such as shield dregs, foundation pit dregs, drilling dregs and the like generated in engineering construction of Yangtze river basin areas.
The invention utilizes the river sludge subjected to dehydration treatment to prepare artificial aggregate, mixes a plurality of siliceous materials by adjusting the mixing proportion, and adopts a hydrothermal synthesis process, thereby not only improving the mechanical property of the artificial aggregate, but also reducing the production energy consumption. Therefore, the technology has the greatest advantage that the river sludge can be industrially and intensively treated, and meanwhile, the artificial aggregate with high added value is produced, so that double economic benefits are generated. The artificial aggregate prepared by the invention can be completely adapted to LC60 high-grade light aggregate concrete, has high compressive strength and good thermal performance, and has important significance for recycling 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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