Composite binder, unfired ceramsite and preparation method of unfired ceramsite

Abstract

The invention discloses a composite binder, unfired ceramsite and a preparation method of the unfired ceramsite, and belongs to the technical field of environment-friendly building materials. The composite binder comprises the following components in percentage by mass: 4%-8% of sodium silicate, 1.0%-1.2% of sodium sulfate, 1.5%-2% of sodium aluminate and 88.8%-92.8% of water. The mass ratio of the sodium silicate to the sodium sulfate to the sodium aluminate is (4-7): 1.2: 2. And adding the mixture into a raw material containing Taihu Lake sludge to prepare the unfired ceramsite. According to the non-fired ceramsite disclosed by the invention, waste is recycled, the production cost is reduced, the ceramsite is prepared in a non-fired manner, the energy is saved, and the prepared ceramsite has relatively high strength and durability.

Description

Technical Field

[0001] The invention relates to the technical field of environmentally friendly building materials, and in particular to a composite binder, unfired ceramsite and a preparation method thereof. Background Art

[0002] With the acceleration of my country's urbanization process, the continuous advancement of water conservancy projects, shipping projects and water environment management projects, the output of river and lake silt is increasing. These silts usually have high water content and low strength, and may contain pollutants such as heavy metals, organic matter and nutrients. If not properly handled, they will cause significant secondary pollution risks to the environment. Therefore, how to effectively treat and utilize these silts has become an urgent problem to be solved.

[0003] Traditional ceramsite preparation processes mostly rely on high-energy sintering processes, which are not only costly but also detrimental to environmental protection. Therefore, the development of technologies for preparing unfired ceramsite is of great significance for resource recycling and environmental protection. However, the existing binders used in unfired ceramsite have low bonding strength, poor bonding between raw materials, and poor controllability of raw material quality. The strength and durability of the prepared unfired ceramsite are often difficult to reach the ideal level in the short term. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a composite binder, unfired ceramsite and a preparation method thereof. The present invention optimizes the composite binder so that it can better achieve the bonding of components such as cement, gypsum and Taihu silt, and at the same time, by pre-treating Taihu silt to obtain silt with a specific water content and particle size, and using it as the main component for the preparation of unfired ceramsite, the waste is reused, the production cost is reduced, and the ceramsite can be prepared without firing, which saves energy, and the prepared ceramsite has higher strength and durability.

[0005] The technical solution of the present invention is as follows:

[0006] The first aspect of the present invention provides a composite binder, which comprises, by mass percentage: 4%-8% sodium silicate, 1.0%-1.2% sodium sulfate, 1.5%-2% sodium aluminate, and 88.8%-92.8% water;

[0007] The mass ratio of the sodium silicate, the sodium sulfate and the sodium aluminate is 4-7:1.2:2.

[0008] Preferably, the composite binder comprises, by mass percentage, 4%-6% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and 88.8%-92.8% water.

[0009] The second aspect of the present invention provides an unfired ceramsite, which comprises, by mass percentage, 40%-60% Taihu silt, 20%-30% cement, 10%-15% gypsum, and 10%-20% composite binder; the composite binder is the composite binder described in the first aspect above.

[0010] Preferably, the water content of the Taihu sludge is less than 5%, and the particle size is 80-2000 mesh.

[0011] Preferably, the particle size of the cement is 80-120 mesh.

[0012] Preferably, the gypsum is building gypsum, and the mesh number of the gypsum is 80-120 meshes.

[0013] The third aspect of the present invention provides a method for preparing the unfired ceramsite described in the second aspect, the method comprising the following steps:

[0014] S1: Pretreatment of Taihu sludge raw materials.

[0015] S2: Prepare composite adhesive.

[0016] S3: According to mass percentage, the Taihu sludge obtained in step S1, the composite binder obtained in step S2, gypsum and cement are mixed and stirred evenly to obtain a blank.

[0017] S4: injecting the blank of step S3 into a mold and pressing it to form a ceramsite blank.

[0018] S5: Curing the green body to obtain solidified ceramsite.

[0019] S6: Dry the solidified ceramsite and sieve to obtain the unfired ceramsite.

[0020] Preferably, in step S1, the Taihu sludge pretreatment is to dehydrate and dry the Taihu sludge raw material and then crush it to obtain Taihu sludge.

[0021] Preferably, in step S2, the composite binder is obtained by mixing sodium silicate, sodium sulfate and sodium aluminate by mass percentage, adding water and stirring evenly, and ultrasonicating; the power of the ultrasonication is 500W, the frequency is 35-40kHz, and the time is 25-35min.

[0022] Preferably, in step S5, the curing includes primary water curing and water-retaining secondary curing; the primary water curing is to allow the ceramsite body obtained in step S4 to stand and then perform steam curing; the standing time is 3-24 hours; the steam curing is carried out in a steam curing room at a curing temperature of 40-80°C, and the steam curing time is 7-9 hours; the water-retaining secondary oxidation is to place the ceramsite obtained from the primary water curing in a plastic bag and allow it to stand for curing for 1-3 days.

[0023] The beneficial technical effects of the present invention are:

[0024] The invention pre-treats Taihu sludge, studies the composition, water content, particle size and other characteristics of the sludge, and optimizes the composite binder compounded with the sludge according to the characteristics of the raw materials, so that the Taihu sludge can be better bonded with components such as cement and gypsum. The prepared unfired ceramsite has excellent physical and mechanical properties, high strength and strong durability, and the service life of the ceramsite is extended. At the same time, the resource recycling of Taihu sludge is realized, and environmental pollution is reduced.

[0025] The preparation method of the invention is simple, the process is controllable, it is suitable for large-scale industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below in conjunction with the embodiments.

[0028] The present invention adds Taihu silt as a component for preparing ceramsite, in order to realize the resource recycling of Taihu silt. However, Taihu silt contains rich minerals and organic matter, and how to combine it with existing raw materials to prepare high-strength unfired ceramsite is a problem that needs to be solved urgently.

[0029] The present invention first optimizes the composite binder and provides a new composite binder, which comprises, by mass percentage, 4%-8% sodium silicate, 1.0%-1.2% sodium sulfate, 1.5%-2% sodium aluminate, and 88.8%-92.8% water. The mass ratio of the sodium silicate, the sodium sulfate and the sodium aluminate is 4-7:1.2:2.

[0030] It can be understood that the sodium silicate used in the present invention can provide good bonding and hardening properties; sodium sulfate enhances the compactness and strength of ceramsite; sodium aluminate enhances viscosity and improves water resistance, and promotes uniform mixing of raw materials. By adjusting the ratio of the three, the bonding of Taihu sludge can be better achieved, and the strength and durability of the prepared ceramsite can be improved.

[0031] In some embodiments, the composite binder includes, by mass percentage, 4%-6% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and 88.8%-92.8% water.

[0032] The second aspect provides a new unfired ceramsite, which comprises, by mass percentage, 40%-60% Taihu sludge, 20%-30% cement, 10%-15% gypsum, and 10%-20% of the above composite binder.

[0033] It can be understood that the present invention can realize the preparation of high-strength and high-durability expanded clay without firing by controlling the ratio of Taihu silt, cement, gypsum and optimized composite binder. Changes in the ratio of cement, Taihu silt and gypsum will lead to changes in the porosity of the expanded clay, thereby affecting the strength of the expanded clay. The ratio of the composite binder will affect the durability of the unfired expanded clay.

[0034] In some embodiments, the Taihu sludge has a water content of less than 5% and a particle size of 80-2000 mesh.

[0035] In some embodiments, the Taihu sludge is Taihu sludge powder, which is obtained by pressing the cleaned Taihu sludge raw material to obtain a filter cake, drying, and crushing to obtain sludge with a moisture content of less than 5% and a particle size of 80-2000 mesh, which is used as the raw material for preparing ceramsite.

[0036] It can be understood that the present invention makes full use of silt, solves the problem of difficult treatment of existing Taihu silt, and at the same time, the recycled silt replaces part of the raw materials, reducing costs. By controlling the water content and particle size of Taihu silt, it can be better mixed with other raw materials, reducing gaps and improving the strength of ceramsite.

[0037] In some embodiments, the cement has a particle size of 80-120 meshes; the gypsum is building gypsum, and the mesh size of the gypsum is 80-120 meshes.

[0038] The third aspect of the present invention provides a method for preparing the above-mentioned unfired ceramsite, the preparation method comprising the following steps:

[0039] S1: Taihu sludge pretreatment.

[0040] S2: Prepare composite adhesive.

[0041] S3: According to mass percentage, the Taihu sludge obtained in step S1, the composite binder obtained in step S2, gypsum and cement are mixed and stirred evenly to obtain a blank.

[0042] S4: injecting the blank of step S3 into a mold and pressing it to form a ceramsite blank.

[0043] S5: Curing the green body to obtain solidified ceramsite.

[0044] S6: Dry the solidified ceramsite and sieve to obtain the unfired ceramsite.

[0045] In some embodiments, in step S1, the Taihu sludge pretreatment is to dehydrate and dry the Taihu sludge raw material and then crush it to obtain the Taihu sludge.

[0046] In some embodiments, in step S2, the composite binder is obtained by mixing sodium silicate, sodium sulfate, and sodium aluminate by mass percentage, adding water and stirring evenly, and ultrasonicating; the power of the ultrasonication is 500w, the frequency is 35-40khz, and the time is 25-35min.

[0047] In some embodiments, in step S5, the curing includes primary water curing and water-retaining secondary curing;

[0048] The primary water curing is to allow the ceramsite body obtained in step S4 to stand for steam curing;

[0049] The standing time is 3-24 hours; the steam curing is carried out in a steam curing room at a curing temperature of 40-80° C., and the steam curing time is 7-9 hours.

[0050] The water-retaining secondary oxidation is to place the ceramsite obtained by primary water culture in a plastic bag and leave it to stand for 1-3 days.

[0051] In the embodiment of the present invention, the cement used is commercially available 42.5R grade silicate cement, and the gypsum is commercially available common building gypsum. The particle size of the building gypsum and cement dry material is about 100 mesh.

[0052] The following are specific embodiments.

[0053] Example 1

[0054] A composite binder comprises, by mass percentage, 4% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and the balance is water.

[0055] The preparation method of the composite binder is as follows: 4% sodium silicate, 1.2% sodium sulfate and 2% sodium aluminate are mixed by mass percentage, the remainder is added with water and stirred evenly, and then ultrasonicated for 30 minutes at a power of 500W and a frequency of 35-40kHz to obtain the composite binder.

[0056] The unfired ceramsite containing the composite binder comprises, by mass percentage, 45% of Taihu sludge, 30% of cement, 15% of building gypsum and 10% of the composite binder.

[0057] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0058] (1) Pretreatment of raw materials: The Taihu sludge is dehydrated, dried and crushed to obtain sludge powder with a moisture content of 4% and a particle size of 200-2000 mesh.

[0059] (2) Preparation of composite adhesive: Prepare the composite adhesive according to the above method and set aside.

[0060] (3) Ingredients: According to the mass percentage, 45% of silt powder, 15% of building gypsum, 30% of cement and 10% of composite binder solution are mixed and stirred evenly to form a viscous blank.

[0061] (4) Strip-rolling and ball-making: The blank is pressed into a cake shape by a cake pressing groove; the cake is put into a strip-rolling groove and cut into long strips with a width of 8 mm. The strip material is passed through a ball-making groove to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape to obtain a ceramsite blank.

[0062] (5) Primary water curing of ceramsite samples: After the ceramsite blanks were allowed to stand at room temperature for 24 h, the ceramsite samples were steam cured at a temperature of 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0063] (6) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 2 days to obtain Taihu silt-based unfired expanded clay.

[0064] Example 2

[0065] A composite binder comprises, by mass percentage, 6% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and the balance is water.

[0066] The preparation method of the composite adhesive of this embodiment is as follows: after mixing 6% sodium silicate, 1.2% sodium sulfate and 2% sodium aluminate by mass percentage, adding water and stirring evenly, and ultrasonicating at a power of 500W and a frequency of 35-40kHz for 30 minutes to obtain the composite adhesive.

[0067] The unfired ceramsite prepared by using the composite binder comprises, by mass percentage, 45% of Taihu sludge, 30% of cement, 15% of building gypsum and 10% of the composite binder.

[0068] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0069] (1) Pretreatment of raw materials: dehydrating, drying and crushing the Taihu sludge to obtain sludge powder with a water content of 4% and a particle size of 200-2000 mesh;

[0070] (2) Preparation of composite adhesive: Prepare the composite adhesive according to the above method and set aside.

[0071] (3) Ingredients: According to the mass percentage, 45% of silt powder, 15% of building gypsum, 30% of cement and 10% of composite binder solution are mixed and stirred evenly to form a viscous blank.

[0072] (4) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing groove, and the cake is put into a strip-making groove and cut into long strips with a width of 8 mm. The strip material passes through a pill-making groove to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape.

[0073] (5) Primary water curing of ceramsite samples: After standing at room temperature for 24 h, the ceramsite samples were steam cured at a temperature of 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0074] (6) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 2 days to obtain Taihu silt-based unfired expanded clay.

[0075] Example 3

[0076] A composite binder comprises, by mass percentage, 4% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and the balance is water.

[0077] The preparation method of the composite binder is as follows: 4% sodium silicate, 1.2% sodium sulfate and 2% sodium aluminate are mixed by mass percentage, water is added and stirred evenly, and ultrasonically treated at a power of 500W and a frequency of 35-40kHz for 30 minutes to obtain the composite binder.

[0078] The unfired ceramsite containing the composite binder comprises, by mass percentage, 45% of Taihu sludge, 30% of cement, 15% of building gypsum and 10% of the composite binder.

[0079] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0080] (1) Pretreatment of raw materials: The Taihu sludge is dehydrated, dried and crushed to obtain sludge powder with a moisture content of 4% and a particle size of 200-2000 mesh.

[0081] (2) Preparation of composite adhesive: Prepare the composite adhesive according to the above method and set aside.

[0082] (3) Ingredients: According to the mass percentage, 45% of silt powder, 15% of building gypsum, 30% of cement and 10% of composite binder solution are mixed and stirred evenly to form a viscous blank.

[0083] (4) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing trough, and the cake is put into a strip-making trough and cut into long strips with a width of 8 mm. The strip material is made into a granular ceramsite blank with a diameter of 8 mm by a pelletizing trough. The blank is placed in a drum and rolled into a spherical shape to obtain a ceramsite blank.

[0084] (5) Primary water curing of ceramsite samples: After the ceramsite blanks were allowed to stand at room temperature for 24 h, the ceramsite samples were steam cured at a temperature of 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0085] (6) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 4 days to obtain Taihu silt-based unfired expanded clay.

[0086] Example 4

[0087] A composite binder comprises, by mass percentage, 6% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and the balance is water.

[0088] The preparation method of the composite adhesive of this embodiment is as follows: after mixing 6% sodium silicate, 1.2% sodium sulfate and 2% sodium aluminate by mass percentage, adding water and stirring evenly, and ultrasonicating at a power of 500W and a frequency of 35-40kHz for 30 minutes to obtain the composite adhesive.

[0089] The unfired ceramsite prepared by using the composite binder comprises, by mass percentage, 45% of Taihu sludge, 30% of cement, 15% of building gypsum and 10% of the composite binder.

[0090] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0091] (1) Pretreatment of raw materials: dehydrating, drying and crushing the Taihu sludge to obtain sludge powder with a water content of 4% and a particle size of 200-2000 mesh;

[0092] (2) Preparation of composite adhesive: Prepare the composite adhesive according to the above method and set aside.

[0093] (3) Ingredients: According to the mass percentage, 45% of silt powder, 15% of building gypsum, 30% of cement and 10% of composite binder solution are mixed and stirred evenly to form a viscous blank.

[0094] (4) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing groove, and the cake is put into a strip-making groove and cut into long strips with a width of 8 mm. The strip material passes through a pill-making groove to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape.

[0095] (5) Primary water curing of ceramsite samples: After standing at room temperature for 24 h, the ceramsite samples were steam cured at a temperature of 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0096] (6) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 4 days to obtain Taihu silt-based unfired expanded clay.

[0097] Example 5

[0098] A composite binder comprises, by mass percentage, 4% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and the balance is water.

[0099] The preparation method of the composite binder is as follows: 4% sodium silicate, 1.2% sodium sulfate and 2% sodium aluminate are mixed by mass percentage, water is added and stirred evenly, and ultrasonically treated at a power of 500W and a frequency of 35-40kHz for 30 minutes to obtain the composite binder.

[0100] The unfired ceramsite containing the composite binder comprises, by mass percentage, 45% of Taihu sludge, 30% of cement, 15% of building gypsum and 10% of the composite binder.

[0101] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0102] (1) Pretreatment of raw materials: The Taihu sludge is dehydrated, dried and crushed to obtain sludge powder with a moisture content of 4% and a particle size of 200-2000 mesh.

[0103] (2) Preparation of composite adhesive: Prepare the composite adhesive according to the above method and set aside.

[0104] (3) Ingredients: According to the mass percentage, 45% of silt powder, 15% of building gypsum, 30% of cement and 10% of composite binder solution are mixed and stirred evenly to form a viscous blank.

[0105] (4) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing trough, and the cake is put into a strip-making trough and cut into long strips with a width of 8 mm. The strip material is made into a granular ceramsite blank with a diameter of 8 mm by a pelletizing trough. The blank is placed in a drum and rolled into a spherical shape to obtain a ceramsite blank.

[0106] (5) Primary water curing of ceramsite samples: After the ceramsite blanks were allowed to stand at room temperature for 24 h, the ceramsite samples were steam cured at a temperature of 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0107] (6) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 6 days to obtain Taihu silt-based unfired expanded clay.

[0108] Example 6

[0109] A composite binder comprises, by mass percentage, 6% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, and the balance is water.

[0110] The preparation method of the composite adhesive of this embodiment is as follows: after mixing 6% sodium silicate, 1.2% sodium sulfate and 2% sodium aluminate by mass percentage, adding water and stirring evenly, and ultrasonicating at a power of 500W and a frequency of 35-40kHz for 30 minutes to obtain the composite adhesive.

[0111] The unfired ceramsite prepared by using the composite binder comprises, by mass percentage, 45% of Taihu sludge, 30% of cement, 15% of building gypsum and 10% of the composite binder.

[0112] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0113] (1) Pretreatment of raw materials: dehydrating, drying and crushing the Taihu sludge to obtain sludge powder with a water content of 4% and a particle size of 200-2000 mesh;

[0114] (2) Preparation of composite adhesive: Prepare the composite adhesive according to the above method and set aside.

[0115] (3) Ingredients: According to the mass percentage, 45% of silt powder, 15% of building gypsum, 30% of cement and 10% of composite binder solution are mixed and stirred evenly to form a viscous blank.

[0116] (4) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing groove, and the cake is put into a strip-making groove and cut into long strips with a width of 8 mm. The strip material passes through a pill-making groove to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape.

[0117] (5) Primary water curing of ceramsite samples: After standing at room temperature for 24 h, the ceramsite samples were steam cured at a temperature of 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0118] (6) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 6 days to obtain Taihu silt-based unfired expanded clay.

[0119] Comparative Example 1

[0120] An unfired ceramsite is the same as Example 1, except that no composite binder is added. The unfired ceramsite comprises, by mass percentage, 45% Taihu sludge, 30% cement, 15% building gypsum, and 10% water.

[0121] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0122] (1) Pretreatment of raw materials: The Taihu sludge is dehydrated, dried and crushed to obtain sludge powder with a moisture content of 4% and a particle size of 200-2000 mesh.

[0123] (2) Ingredients: According to the mass percentage, 45% of Taihu silt, 30% of cement, 15% of building gypsum and 10% of water are mixed and stirred evenly to obtain a blank.

[0124] (3) Strip-rolling and ball-making: The blank is pressed into a cake shape by a cake pressing trough, and the cake is put into a strip-rolling trough and cut into long strips with a width of 8 mm. The strip material is passed through a pill-making trough to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape to obtain a ceramsite blank.

[0125] (4) Primary water curing of ceramsite samples: After the ceramsite body is left standing at room temperature for 24 h, it is steam cured at 70 °C for 8 h to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0126] (5) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 2 days to obtain Taihu silt-based unfired expanded clay.

[0127] Comparative Example 2

[0128] The unfired ceramsite comprises, by mass percentage, 45% of Taihu silt, 30% of cement, 15% of building gypsum and 10% of water.

[0129] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0130] (1) Pretreatment of raw materials: The Taihu sludge is dehydrated, dried and crushed to obtain sludge powder with a moisture content of 4% and a particle size of 200-2000 mesh.

[0131] (2) Ingredients: According to the mass percentage, 45% silt powder, 15% building gypsum, 30% cement and 10% water are mixed and stirred evenly to form a viscous blank.

[0132] (3) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing groove, and the cake is put into a strip-making groove and cut into long strips with a width of 8 mm. The strip material passes through a pill-making groove to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape.

[0133] (4) Primary water curing of ceramsite samples: After standing at room temperature for 24 hours, the ceramsite samples were steam cured at a temperature of 70°C for 8 hours to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0134] (5) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 4 days to obtain Taihu silt-based unfired expanded clay.

[0135] Comparative Example 3

[0136] The unfired ceramsite comprises, by mass percentage, 45% of Taihu silt, 30% of cement, 15% of building gypsum and 10% of water.

[0137] The preparation method of the above-mentioned unfired ceramsite is as follows:

[0138] (1) Pretreatment of raw materials: The Taihu sludge is dehydrated, dried and crushed to obtain sludge powder with a moisture content of 4% and a particle size of 200-2000 mesh.

[0139] (2) Ingredients: According to the mass percentage, 45% silt powder, 15% building gypsum, 30% cement and 10% water are mixed and stirred evenly to form a viscous blank.

[0140] (3) Strip-making and ball-rolling: The blank is pressed into a cake shape by a cake pressing groove, and the cake is put into a strip-making groove and cut into long strips with a width of 8 mm. The strip material passes through a pill-making groove to be made into a granular ceramsite blank with a diameter of 8 mm. The blank is placed in a drum and rolled into a spherical shape.

[0141] (4) Primary water curing of ceramsite samples: After standing at room temperature for 24 hours, the ceramsite samples were steam cured at a temperature of 70°C for 8 hours to allow the binder to react fully and the ceramsite to solidify and form, and then cooled to room temperature.

[0142] (5) Water-retaining and natural curing: The expanded clay that has undergone primary water curing is placed in a plastic bag for water-retaining and natural curing at room temperature for 6 days to obtain Taihu silt-based unfired expanded clay.

[0143] Test example:

[0144] The bulk density, apparent density, porosity, and compressive strength of the ceramics prepared in the examples and comparative examples were measured, wherein the compressive strength was measured by a particle strength tester; the bulk density, apparent density, and porosity were tested in accordance with CJ / T 299-2008 "Artificial ceramsite filter material for water treatment"; the specific test structure is shown in Table 1.

[0145] Table 1 Performance test of ceramics prepared in Examples and Comparative Examples

[0146]

[0147]

[0148] It can be seen from Table 1 that the ceramsite containing Taihu sludge prepared by the present invention has a higher porosity and improves the compressive strength of the ceramsite by adding a composite binder and optimizing the composite binder.

[0149] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A composite adhesive, characterized in that: Calculated by mass percentage, it includes: 4%-8% sodium silicate, 1.0%-1.2% sodium sulfate, 1.5%-2% sodium aluminate, and 88.8%-92.8% water; The mass ratio of the sodium silicate, the sodium sulfate and the sodium aluminate is 4-7:1.2:

2.

2. The composite adhesive according to claim 1, comprising, by mass percentage: 4%-6% sodium silicate, 1.2% sodium sulfate, 2% sodium aluminate, 88.8%-92.8% water.

3. A kind of unfired ceramsite, characterized in that: Calculated by mass percentage, it includes 40%-60% Taihu silt, 20%-30% cement, 10%-15% gypsum, and 10%-20% composite binder; The composite adhesive is the composite adhesive according to any one of claims 1 to 2.

4. The unfired ceramsite according to claim 3, characterized in that: The water content of the Taihu sludge is less than 5%, and the particle size is 80-2000 meshes.

5. The unfired ceramsite according to claim 3, characterized in that: The particle size of the cement is 80-120 meshes.

6. The unfired ceramsite according to claim 3, characterized in that: The gypsum is building gypsum, and the mesh number of the gypsum is 80-120 meshes.

7. A method for preparing the unfired ceramsite according to any one of claims 3 to 6, characterized in that: The preparation method comprises the following steps: S1: Taihu sludge raw material pretreatment; S2: prepare composite adhesive; S3: mixing the Taihu sludge obtained in step S1, the composite binder obtained in step S2, gypsum and cement according to mass percentage, stirring evenly to obtain a blank; S4: injecting the blank of step S3 into a mold and pressing it to form a ceramsite blank; S5: curing the green body to obtain solidified ceramsite; S6: Dry the solidified ceramsite and sieve to obtain the unfired ceramsite.

8. The preparation method according to claim 7, characterized in that: In step S1, the Taihu sludge pretreatment is to dehydrate and dry the Taihu sludge raw material and then crush it to obtain Taihu sludge.

9. The preparation method according to claim 7, characterized in that: In step S2, the composite binder is obtained by mixing sodium silicate, sodium sulfate and sodium aluminate in percentage by mass, adding water and stirring evenly, and ultrasonicating; the power of the ultrasonication is 500W, the frequency is 35-40kHz, and the time is 25-35min.

10. The preparation method according to claim 7, characterized in that: In step S5, the curing includes primary water curing and water-retaining secondary curing; The primary water curing is to allow the ceramsite body obtained in step S4 to stand for steam curing; The standing time is 3-24 hours; the steam curing is carried out in a steam curing room at a curing temperature of 40-80° C. and the steam curing time is 7-9 hours; The water-retaining secondary oxidation is to place the ceramsite obtained by primary water culture in a plastic bag and leave it to stand for 1-3 days.

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