High-temperature-resistant solid waste type alkali-activated cementitious material and preparation method thereof

Abstract

The application discloses a high-temperature-resistant solid waste type alkali-activated cementing material and a preparation method thereof, which is prepared from 45.1-53.5% of slag, 7.5-12.2% of calcined waste diatomite filter aid, 13.5-18.8% of bottom ash of household garbage incinerator, 15.7-20.1% of charcoal ash and 8.7-13.5% of water. The alkali-activated cementing material is prepared from multiple materials, so that the residual compressive strength of the alkali-activated cementing material under high temperature can be obviously improved, and the structural damage caused by high temperature can be reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of building materials, and particularly relates to a high-temperature-resistant solid waste type alkali-activated cementitious material and a preparation method thereof. BACKGROUND

[0002] Compared with traditional ordinary Portland cement, the alkali-activated cementitious material has a wide raw material source, a simple preparation process, better environmental effect, excellent mechanical properties, corrosion resistance and durability. However, the alkali-activated cementitious material often has a strength decrease of about 80% at a high temperature of 800 DEG C, and the compressive strength is almost reduced to 0 at 1000 DEG C. The significant decrease in strength at high temperatures is mainly caused by the change in the internal pore structure. With the increase of temperature, the vapor pressure generated by the evaporation of free water in the pores increases. The internal dense pore structure limits the effective release of the vapor pressure, resulting in the continuous increase of the internal pressure, the generation of small cracks between the pores, and the serious damage to the internal structure. At the same time, the thermal stress caused by the non-uniform heat conduction and the thermal expansion difference between the phases will cause micro-cracks in the cementitious material. With the gradual increase of the vapor pressure and the thermal stress, the cracks continuously develop, and finally lead to the serious decrease of the strength at high temperatures.

[0003] Slag is a by-product in the process of blast furnace ironmaking, and its main components are silicate and silico-aluminate melts. The waste diatomite filter aid is a waste produced in the process of beer purification, and its main components are CaO, Fe2O3, Al2O3, SiO2, MgO and P2O5. After use, the internal pores of the diatomite filter aid are filled and cannot be used again, but it contains a large amount of amorphous SiO2 and has the potential to be activated by strong alkali. However, the current treatment method of the waste diatomite filter aid is mainly direct landfill or discharge into rivers and seas after a large amount of treatment. The annual municipal solid waste collection volume in China is more than 100 million tons and is on the rise, and a large amount of slag is produced after incineration. At present, the main treatment method for the incineration slag of municipal solid waste is landfill, but landfill will cause the leaching of heavy metals and dissolved salts to exceed the standard, thereby causing secondary pollution to the surrounding environment. Charcoal ash is the residue produced by the combustion of cellulose, hemicellulose and other organic matters in wood or wood products, and it is currently mainly used as a fertilizer in the agricultural field, but its application in the field of building materials is rarely reported. At present, the stacking of a large amount of slag, waste diatomite filter aid, incineration slag of municipal solid waste and charcoal ash not only occupies valuable land, but also pollutes the soil and groundwater. Therefore, how to large-scale and high-value utilize slag, waste diatomite filter aid, incineration slag of municipal solid waste and realize environmental reduction, resource maximization and enterprise efficiency is an urgent problem to be solved.

[0004] Previous studies have used similar solid waste materials to prepare alkali-activated cementitious materials. For example, patent CN115849749A discloses a high-strength environmentally friendly alkali-activated cementitious material and its preparation method. The cementitious material is prepared by mixing slag, waste diatomite filter aid, building solid waste regenerated micro powder, lithium slag, glass powder and alkali activator. However, the particle size of each raw material has too many restrictions, making large-scale production very difficult. Meanwhile, the main research point of this patent is limited to the active characteristics of the waste diatomite filter aid, and does not involve the high temperature resistance of the material. Patent CN115893879A discloses a preparation method of a solid waste-based ultra-fine special composite cementitious material and the cementitious material. It utilizes the potential pozzolanic activity of bulk solid waste (slag, fly ash, sludge incineration ash, household waste incinerator slag, steel slag, phosphogypsum, red mud and carbide slag) and develops a solid waste-based ultra-fine special composite cementitious material based on the principle of solid waste synergistic utilization. However, its preparation process is complex and energy consumption is high, which is not conducive to large-scale production. Meanwhile, previous studies have also used solid waste to prepare and study its high temperature resistance. For example, patent CN107352872A discloses a diatom sand bead and a high-strength environmentally friendly thermal insulation mortar containing diatom sand beads. The mortar raw materials include diatom sand beads, diatom powder, environmentally friendly latex powder, cement, wood fiber, cellulose, vitrified microbeads and water. Only the calcined and activated diatomite is used as a high-performance admixture to replace part of the cement, which can improve the compressive and flexural strength of the thermal insulation mortar while reducing the thermal conductivity of the thermal insulation mortar. However, the use amount of cement in this patent is still large, which is contrary to the national double carbon strategy, and the preparation cost increases significantly with the continuous rise of cement price. SUMMARY

[0005] In view of the above-mentioned defects and problems of alkali-activated cementitious materials, the present application provides a high-temperature-resistant solid waste type alkali-activated cementitious material and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A high-temperature-resistant solid waste type alkali-activated cementitious material, wherein the raw material components and the mass percentage of each component are as follows: slag 45.1%-53.5%, calcined waste diatomite filter aid 7.5%-12.2%, household waste incinerator bottom ash 13.5%-18.8%, charcoal ash 15.7-20.1%, and water 23.5%-30.2%. The sum of the mass percentages of each component is 100%.

[0008] Further, the slag is a finely ground blast furnace slag powder with a specific surface area greater than 400 m 2 / kg.

[0009] Further, the calcined waste diatomite filter aid is a powder solid obtained by drying the diatomite filter aid used for beer slurry filtration for several times at 105℃, and calcining at 400℃ for 1h, with a particle size range of 200-400 mesh, wherein the content of amorphous SiO2 is ≥80%, and the content of impurities is ≤10%.

[0010] Further, the bottom ash of household waste incinerator slag is a small particle obtained by drying the household waste incinerator slag at 60℃ for 24h and then crushing, with a particle size range of 100-300 mesh, wherein the total content of SiO2, Al2O3 and CaO is ≥70%.

[0011] Further, the charcoal ash is a waste residue produced by burning wood or wood products, with a particle size range of 200-300 mesh, and the main components are K2CO3 and metal oxides, wherein the content of K2CO3 is not less than 80%.

[0012] The preparation method of the high-temperature-resistant solid waste type alkali-activated cementitious material comprises the following steps:

[0013] (1) slowly add the charcoal ash into water at a mass ratio of 1:1.5, continuously stirring during the process, and stop stirring when the supernatant pH of the obtained charcoal ash aqueous solution is ≥11.5;

[0014] (2) take 60% of the charcoal ash aqueous solution obtained in step (1), slowly add the bottom ash of household waste incinerator slag into it, continuously stirring during the process, and then place it in a 60℃ water bath for 1d, filter the residue, dry the obtained filter residue at 105℃, and then ball mill and crush it for 2h at a speed of 45r / min, and then pass it through a 300 mesh sieve, and reserve the fine powder under the sieve for later use;

[0015] (3) pour the fine powder obtained in step (2), calcined waste diatomite filter aid and slag into a stirrer according to the proportion, slowly stir for 0.5 minutes, and obtain a mixed dry material;

[0016] (4) pour the remaining charcoal ash aqueous solution into the stirrer of step (3), slowly stir it with the mixed dry material for 0.5 minutes, and then quickly stir it for 1-3 minutes, stop stirring when the slurry has a certain fluidity, and then cast it into a mold;

[0017] (5) demold after 1d, and then place it in a standard curing room with a temperature of 20±2℃ and a relative humidity of more than 95% for 28d.

[0018] Further, the stirring speed of the slow stirring is 62±5 r / min, and the stirring speed of the fast stirring is 285±10 r / min.

[0019] The bottom ash of municipal solid waste incinerator is a smaller particle obtained by drying and crushing the municipal solid waste incinerator ash. The outer surface of the particle is loose and porous, which is beneficial to the release of internal steam pressure at high temperature. The content of aluminum oxide in the chemical composition of the bottom ash of municipal solid waste incinerator is relatively high, which can form a heat conduction barrier to a certain extent, hinder the internal heat transfer, and enhance the thermal stability of the cementitious material. Therefore, when the bottom ash of municipal solid waste incinerator is used for alkali-activated cementitious material, it is beneficial to improve the high-temperature resistance of the cementitious material. In addition, SiO2 contained in the bottom ash of municipal solid waste incinerator has the potential to be activated by strong alkali. After the bottom ash of municipal solid waste incinerator is soaked in a charcoal ash aqueous solution, the pozzolanic activity of the bottom ash can be fully activated. Then, when the bottom ash is added to an alkali-activated slag system, the reaction degree of the system can be improved, more hydration products can be generated, and the strength of the alkali-activated cementitious material can be improved. At the same time, elemental Al in the bottom ash of municipal solid waste incinerator can release hydrogen gas in an alkaline environment, which avoids the damage to the internal structure of the cementitious material caused by subsequent hydrogen gas, thereby preventing the strength from decreasing.

[0020] The waste diatomite filter aid has high pozzolanic activity and has the potential to be activated by strong alkali, which can greatly improve the mechanical properties of alkali-activated slag cementitious material. In addition, the porous material characteristics of the waste diatomite filter aid calcined at high temperature are obviously enhanced, which can further improve the internal pore structure of the alkali-activated slag cementitious material and reduce the steam pressure formed by the evaporation of free water in the pores under the action of high temperature, thereby effectively inhibiting the formation and development of micro-cracks in the cementitious material at high temperature. At the same time, when the waste diatomite filter aid calcined at high temperature is added to the alkali-activated slag system, it will melt and viscous sintering occur inside at high temperature, which can inhibit the further development of micro-cracks.

[0021] The main component of charcoal ash is potassium carbonate. When it is mixed with water, the aqueous solution is highly alkaline, which is due to the high solubility of alkali metal carbonate and the formation of aqueous metal hydroxide (K2CO3+H2O→2KOH+H2CO3, Na2CO3+H2O→2NaOH+H2CO3). At the same time, it contains a certain amount of soluble amorphous metal oxide, which can lead to a high pH value (pH can reach 10.5-12). Therefore, it can be used as a low-cost alkaline activator for preparing alkali-activated environmentally friendly cementitious material.

[0022] Based on the above analysis, the present application proposes a kind of high-temperature-resistant solid waste type alkali-activated cementitious material prepared by mixing slag, waste diatomite filter aid, household waste incinerator bottom ash and charcoal ash as composite precursor, which utilizes the porous structure of waste diatomite filter aid and household waste incinerator bottom ash to improve the internal pore structure of alkali-activated cementitious material, which is more conducive to the release of internal steam pressure, thereby effectively inhibiting the formation and development of microcracks of cementitious material at high temperature, and further improving the residual compressive strength of cementitious material after high temperature;The waste diatomite filter aid can be alkali-activated to generate C-S-H gel in the alkali slag cement system, which can inhibit the further development of microcracks of alkali slag cementitious material doped with waste diatomite filter aid in high temperature environment such as fire, and is beneficial to further maintain the compressive strength at high temperature.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1. The calcined waste diatomite filter aid and household waste incinerator bottom ash used in the present application have porous material properties, which can improve the internal pore structure of the material and facilitate the release of steam pressure formed by the evaporation of free water in the pores at high temperature, reduce the formation and development of microcracks of cementitious material at high temperature, and effectively reduce the damage of steam pressure to the internal structure.

[0025] 2. The waste diatomite filter aid is doped into the alkali-activated slag system after high-temperature calcination, and its porous structure characteristics make it melt and viscous sintering inside in high temperature environment such as fire, which can inhibit the further development of microcracks and maintain the compressive strength at high temperature.

[0026] 3. The present application uses charcoal ash water solution to pre-soak and water bath heating to fully activate the pozzolanic activity of household waste incinerator bottom ash, and then adds it into the alkali-activated slag system, which can further improve the reaction process of the system. At the same time, the elemental Al contained in the household waste incinerator bottom ash can react in alkaline environment to release hydrogen in advance, avoiding the damage of subsequent hydrogen to the internal structure of cementitious material and leading to strength reduction, which is an economic benefit and environmental benefit.

[0027] 4. The materials used in the present application are all solid waste, which can be used to prepare alkali-activated slag cementitious material, which can reduce the cost of traditional building materials, has certain feasibility in economy, realizes the resource utilization of waste materials, reduces the occupation of land by waste stacking and landfill, avoids the secondary pollution of waste to the environment, and has significant environmental benefits. DETAILED DESCRIPTION

[0028] A kind of high-temperature-resistant solid waste type alkali-activated cementitious material, its preparation includes the following steps:

[0029] (1) slowly add the charcoal ash into water with a mass ratio of 1:1.5, continuously stirring during the process, until the supernatant of the obtained charcoal ash aqueous solution has a pH≥11.5, and then stop stirring;

[0030] (2) take 60wt% of the obtained charcoal ash aqueous solution in step (1), slowly add the household garbage incineration bottom ash into the solution, continuously stirring during the process, and then place in a 60℃ water bath for 1d, and then filter, dry the obtained filter residue at 105℃, and then crush in a ball mill at a rotating speed of 45r / min for 2h, and then pass through a 300-mesh sieve, and then take the undersize fine powder for later use;

[0031] (3) pour the obtained fine powder in step (2), calcined waste diatomite filter aid and slag into a stirrer according to the proportion, slowly stir at a rotating speed of 62±5r / min for 0.5min, and then obtain a mixed dry material;

[0032] (4) pour the remaining charcoal ash aqueous solution into the stirrer in step (3), slowly stir with the mixed dry material at a rotating speed of 62±5r / min for 0.5min, and then quickly stir at a rotating speed of 285±10r / min for 1~3min, until the slurry has a certain fluidity, stop stirring, and then cast into a mold;

[0033] (5) after 1d, remove the mold, and then place in a standard curing room with a temperature of 20±2℃ and a relative humidity of more than 95% for 28d.

[0034] The mass percentage of each raw material component used is: slag 45.1%~53.5%, calcined waste diatomite filter aid 7.5%~12.2%, household garbage incineration bottom ash 13.5%~18.8%, charcoal ash 15.7~20.1%, and water 23.5%~30.2%, and the sum of the mass percentages of each component is 100%.

[0035] The slag is a finely ground blast furnace slag powder with a specific surface area greater than 400 m 2 / kg.

[0036] The calcined waste diatomite filter aid is a powder-shaped solid obtained by drying the diatomite filter aid used for beer slurry filtration for several times at 105℃, and then calcining at 400℃ for 1h, and has a particle size range of 200~400 mesh, wherein the content of amorphous SiO2 is≥80%, and the content of impurities is≤10%.

[0037] The household garbage incineration bottom ash is a small particle obtained by drying the household garbage incineration bottom ash at 60℃ for 24h, and then crushing, and has a particle size range of 100~300 mesh, wherein the total content of SiO2, Al2O3 and CaO is≥70%.

[0038] The charcoal ash is waste residue generated by burning wood or wood products, has a particle size range of 200-300 mesh, and mainly contains K2CO3 and metal oxides, wherein the content of K2CO3 is not less than 80%.

[0039] In order to make the content of the application more convenient to understand, the technical solutions of the application will be further described below in combination with specific embodiments, but the application is not limited to this.

[0040] Example 1

[0041] A high-temperature-resistant solid waste type alkali-activated cementitious material, the preparation of which comprises the following steps:

[0042] (1) slowly add charcoal ash into water according to a mass ratio of 1:1.5, continuously stir during the process, and stop stirring until the supernatant of the obtained charcoal ash aqueous solution has a pH≥11.5;

[0043] (2) take 60% of the mass of the charcoal ash aqueous solution obtained in step (1), slowly add domestic waste incinerator bottom ash into it, continuously stir during the process, then place it in a 60℃ water bath for 1 day, filter, dry the obtained filter residue at 105℃, then crush it in a ball mill at a speed of 45 r / min for 2 h, pass it through a 300 mesh sieve, and reserve the undersize fine powder for use;

[0044] (3) dry the waste diatomite filter aid at 105℃ until there is no obvious change in mass, then calcine it at 400℃ for 1 h to obtain a powder-like solid of calcined waste diatomite filter aid, and cool it to room temperature for use;

[0045] (4) pour the fine powder obtained in step (2), the calcined waste diatomite filter aid obtained in step (3), and slag into a stirrer according to the proportion, slowly stir at a speed of 62±5 r / min for 0.5 minutes to obtain mixed dry materials;

[0046] (5) pour the remaining charcoal ash aqueous solution into the stirrer of step (4), slowly stir it together with the mixed dry materials at a speed of 62±5 r / min for 0.5 minutes, then quickly stir it at a speed of 285±10 r / min for 1-3 minutes, stop stirring when the slurry has a certain fluidity, then cast it into a mold;

[0047] (6) remove the mold after 1 day of standing, then place it in a standard curing room with a temperature of 20±2℃ and a relative humidity of more than 95% for 28 days of curing.

[0048] The mass percentages of the used raw material components are as follows: slag 49.5%, calcined waste diatomite filter aid 8.1%, domestic waste incinerator bottom ash 14.4%, charcoal ash 18.6%, and water 27.9%. The specific surface area of the used slag is 450 m 2 / kg; the particle size of the calcined waste diatomite filter aid was 300 mesh, and the amorphous SiO2 content was 80%, and the impurity content was 5%; the particle size of the used household garbage incineration bottom ash was 100 mesh; the particle size of the used charcoal ash was 300 mesh, and the K2CO3 content was 85%.

[0049] Example 2

[0050] A high-temperature-resistant solid waste type alkali-activated cementitious material, the preparation thereof comprising the following steps:

[0051] (1) The charcoal ash was slowly added into water at a mass ratio of 1:1.5, and the stirring was continuously carried out during the process, until the supernatant pH of the obtained charcoal ash aqueous solution was ≥11.5, and then the stirring was stopped;

[0052] (2) 60% of the mass of the obtained charcoal ash aqueous solution in step (1) was taken, and the household garbage incineration bottom ash was slowly added thereinto, and the stirring was continuously carried out during the process, and then the mixture was placed in a water bath at 60°C for 1 day, and then filtered, and the obtained filter residue was dried at 105°C, and then crushed in a ball mill at a rotating speed of 45 r / min for 2 h, and then passed through a 300 mesh sieve, and the undersize fine powder was reserved for use;

[0053] (3) The waste diatomite filter aid was dried at 105°C until the mass showed no obvious change, and then calcined at 400°C for 1 h to obtain a powder-like solid of the calcined waste diatomite filter aid, which was cooled to room temperature for use;

[0054] (4) The fine powder obtained in step (2), the calcined waste diatomite filter aid obtained in step (3), and the slag were poured into a stirrer according to the proportion, and stirred at a rotating speed of 62±5 r / min for 0.5 min to obtain a mixed dry material;

[0055] (5) The remaining charcoal ash aqueous solution was poured into the stirrer in step (4), and stirred at a rotating speed of 62±5 r / min for 0.5 min with the mixed dry material, and then stirred at a rotating speed of 285±10 r / min for 1-3 min, until the slurry had a certain fluidity, and then the stirring was stopped, and then the slurry was cast into a mold;

[0056] (6) After being placed for 1 day, the mold was removed, and then placed in a standard curing room with a temperature of 20±2°C and a relative humidity of more than 95% for curing for 28 days.

[0057] The mass percentage of each raw material component used was as follows: slag 47.1%, calcined waste diatomite filter aid 10.5%, household garbage incineration bottom ash 14.4%, charcoal ash 18.6%, and water 27.9%. The specific surface area of the used slag was 450 m 2 / kg; the particle size of the calcined waste diatomite filter aid was 300 mesh, and the amorphous SiO2 content was 80%, and the impurity content was 5%; the particle size of the used household garbage incineration bottom ash was 200 mesh; the particle size of the used charcoal ash was 300 mesh, and the K2CO3 content was 85%.

[0058] Example 3

[0059] A high-temperature-resistant solid waste type alkali-activated cementitious material, the preparation thereof comprises the following steps:

[0060] (1) wood charcoal ash is slowly added into water at a mass ratio of 1:1.5, and stirring is continuously carried out during the process, until the supernatant pH of the obtained wood charcoal ash aqueous solution is greater than or equal to 11.5, and then the stirring is stopped;

[0061] (2) 60% of the mass of the wood charcoal ash aqueous solution obtained in step (1) is taken, and household garbage incineration bottom ash is slowly added thereinto, and stirring is continuously carried out during the process, and then the mixture is placed in a water bath at 60°C for 1 day, and then filtration is carried out, and the obtained filter residue is dried at 105°C, and then the filter residue is broken in a ball mill at a rotating speed of 45 r / min for 2 h, and then the broken filter residue is sieved through a 300 mesh sieve, and the undersize fine powder is reserved for use;

[0062] (3) the waste diatomite filter aid is dried at 105°C until the mass of the waste diatomite filter aid has no obvious change, and then the waste diatomite filter aid is calcined at a high temperature of 400°C for 1 h, and then a powder-like solid of the calcined waste diatomite filter aid is obtained, and the powder-like solid is cooled to room temperature for use;

[0063] (4) the fine powder obtained in step (2), the calcined waste diatomite filter aid obtained in step (3) and slag are poured into a stirrer according to the proportion, and the mixture is slowly stirred at a rotating speed of 62±5 r / min for 0.5 minutes, and then a mixed dry material is obtained;

[0064] (5) the remaining wood charcoal ash aqueous solution is poured into the stirrer of step (4), and the wood charcoal ash aqueous solution is slowly stirred at a rotating speed of 62±5 r / min for 0.5 minutes together with the mixed dry material, and then the wood charcoal ash aqueous solution is quickly stirred at a rotating speed of 285±10 r / min for 1-3 minutes, and then the stirring is stopped when the slurry has a certain fluidity, and then the slurry is poured into a mold;

[0065] (6) the mold is removed after being placed for 1 day, and then the mold is placed in a standard curing room with a temperature of 20±2°C and a relative humidity of more than 95% for curing for 28 days.

[0066] The mass percentage of each raw material component used is as follows: slag 45.4%, calcined waste diatomite filter aid 12.2%, household garbage incineration bottom ash 14.4%, charcoal ash 18.6% and water 27.9%. The specific surface area of the used slag is 450 m 2 / kg; the particle size of the calcined waste diatomite filter aid was 300 mesh, the content of amorphous SiO2 was 80%, and the content of impurities was 5%; the particle size of the used household garbage incineration bottom ash was 300 mesh; the particle size of the used charcoal ash was 300 mesh, and the content of K2CO3 was 85%.

[0067] Comparative Example 1

[0068] In step (3), the waste diatomite filter aid was dried at 105℃ until the mass did not change significantly, and then cooled to room temperature for use. The other operations were the same as in Example 1.

[0069] Comparative Example 2

[0070] No calcined waste diatomite filter aid was added in the component, and the other operations were the same as in Example 1.

[0071] Comparative Example 3

[0072] No household garbage incineration bottom ash was added in the component, and the other operations were the same as in Example 1.

[0073] Comparative Example 4

[0074] The particle size of the used household garbage incineration bottom ash was 400 mesh, and the other operations were the same as in Example 1.

[0075] After the cementing materials prepared in Examples 1-3 and Comparative Examples 1-4 were taken out of the curing room and naturally air-dried, they were placed in a box-type electric furnace for heating at different target temperatures (100℃, 200℃, 400℃, 600℃, and 800℃). The heating process was carried out at a rate of 5℃ / min, and the temperature was kept constant at the target temperature for 120min (for example, when heated at 800℃, the temperature was raised at a rate of 5℃ / min from 25℃, and the temperature was kept constant at 800℃ for 120min). After the samples were naturally cooled, they were observed for appearance.

[0076] It was observed that the appearance characteristics of the cementing material test pieces prepared in Examples 1-3 and Comparative Examples 1-4 changed significantly after high-temperature heating. The high-temperature resistant solid waste type alkali-activated cementing material of Example 1 added calcined waste diatomite filter aid and household garbage incineration bottom ash had no obvious cracks on the surface when heated to 600℃, and the color did not change significantly from that at room temperature, both being light gray. When heated to 800℃, the test piece turned into light gray, and a small amount of fine cracks appeared on the surface.

[0077] The test piece of Comparative Example 1 had no obvious cracks on the surface when the temperature reached 400℃, and the color was light gray at room temperature. When heated to 600℃, fine cracks appeared on the surface, and the appearance color turned into light gray. When heated to 800℃, the test piece showed peeling and slight loose appearance.

[0078] The test piece of Comparative Example 2 had no obvious cracks on the surface when the temperature reached 200℃, and the color was light gray at room temperature and at 200℃; fine cracks appeared on the surface at 400℃, and the appearance color changed to light gray; at 600℃, the test piece showed peeling phenomenon and slight loose state.

[0079] The appearance damage of Comparative Example 3 increased with the increasing temperature. When the temperature reached 200℃, the test piece had no obvious cracks on the surface, and the color was light white at room temperature and at 200℃; when the temperature reached 400℃, a large number of fine cracks appeared on the surface, and peeling phenomenon occurred, showing slight loose state; after high temperature at 600℃, a large number of cracks occurred on the surface of the matrix, and loose phenomenon occurred; at 800℃, the test piece was completely loose and the compressive strength could not be measured.

[0080] The test piece of Comparative Example 4 had fine cracks on the surface when the temperature reached 400℃, and the appearance color changed to light gray; at 600℃, a large number of fine cracks appeared on the surface of the test piece.

[0081] The compressive strength of the cementitious materials obtained in the examples and comparative examples at 28 days and after high temperature was tested according to "Cement and Cementitious Materials Strength Test" (GB / T 17671-1999), and the results are shown in Table 1.

[0082] Table 1 Compressive strength of test pieces at different temperature stages / MPa

[0083]

[0084] As shown in Table 1, the compressive strength of the cementitious materials obtained in the examples at 28 days was higher than that of the comparative examples; compared with Comparative Examples 1-3, the residual compressive strength of the cementitious materials prepared in the examples after high temperature was higher, indicating that the addition of calcined waste filter aid diatomite and bottom ash of household waste incinerator was beneficial to improve the compressive strength after high temperature. Among them, the cementitious material prepared by using 10.5% of calcined waste diatomite filter aid and 14.4% of bottom ash of household waste incinerator in Example 2 had the best high temperature resistance performance. As can be seen from the comparison between Example 1 and Comparative Example 1, whether the waste diatomite filter aid was calcined greatly affected the residual compressive strength after high temperature. In addition, as can be seen from the comparison between Example 1 and Comparative Example 4, the mesh number of the bottom ash of household waste incinerator was also a key factor affecting the residual compressive strength after high temperature.

[0085] In summary, the high-temperature-resistant solid waste type alkali-activated cementitious material prepared from slag, calcined waste diatomite filter aid, household waste incineration bottom ash and charcoal ash has the following advantages: 1) Under high temperature environment, the waste diatomite filter aid treated by high temperature calcination melts itself, internal viscous sintering occurs, which can inhibit the development of microcracks and maintain the residual compressive strength under high temperature. At the same time, the porous structure of the calcined waste diatomite filter aid can further improve the internal pore structure of the material, which can effectively reduce the steam pressure formed due to internal water evaporation. 2) The household waste incineration bottom ash is porous on the surface of the particles due to high temperature incineration, which is beneficial to the release of internal steam pressure under high temperature. After soaking in charcoal ash aqueous solution, the reactivity is fully activated in advance. After adding the alkali-activated slag system, the reaction degree of the system can be improved, which is more conducive to the strength maintenance of the system under high temperature. The elemental Al contained in the household waste incineration bottom ash reacts in an alkaline environment to release hydrogen in advance, avoiding the damage of subsequent hydrogen to the internal structure of the cementitious material and causing strength reduction. The high content of alumina in the chemical composition forms a heat conduction barrier to a certain extent, hindering the internal heat transfer. 3) The alkaline activator is prepared by mixing charcoal ash and water, without using any chemical reagent, which greatly reduces the environmental pollution caused by chemical reagents. At the same time, all the raw materials used in preparation are waste, which has high solid waste utilization rate, simple process flow, low production cost, energy saving and is an environmentally friendly cementitious material. Therefore, the high-temperature-resistant solid waste type alkali-activated cementitious material prepared from slag, calcined waste diatomite filter aid, household waste incineration bottom ash and charcoal ash is expected to be widely used in various building structures under high temperature environment, effectively reducing the risk of structural damage caused by high temperature.

[0086] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the application should be included in the scope of the present application.

Claims

1. A high temperature resistant solid waste type alkali-activated cementitious material, characterized in that: The raw material components and the mass percentage of each component are as follows: 45.1%-53.5% of slag, 7.5%-12.2% of calcined waste diatomite filter aid, 13.5%-18.8% of household garbage incineration bottom ash, 15.7-20.1% of charcoal ash, and 23.5%-30.2% of water, and the sum of the mass percentages of the components is 100%. The calcined waste diatomite filter aid is a powder-shaped solid obtained by drying the diatomite filter aid used for beer slurry filtration at 105 DEG C and calcining at 400 DEG C for 1 h, and the particle size range is 200-400 mesh, wherein the content of amorphous SiO2 is greater than or equal to 80%, and the content of impurities is less than or equal to 10%. The household garbage incineration bottom ash is a small particle obtained by drying the household garbage incineration bottom ash at 60 DEG C for 24 h and then crushing, and the particle size range is 100-300 mesh. The preparation of the high-temperature-resistant solid waste type alkali-activated cementitious material comprises the following steps: (1) slowly adding charcoal ash into water at a mass ratio of 1:1.5, continuously stirring during the process, and stopping stirring until the supernatant of the obtained charcoal ash aqueous solution has a pH greater than or equal to 11.5; (2) taking 60 wt% of the charcoal ash aqueous solution obtained in step (1), slowly adding household garbage incineration bottom ash into the charcoal ash aqueous solution, continuously stirring during the process, and then placing in a 60 DEG C water bath for 1 day, filtering the obtained residue, drying the residue at 105 DEG C, ball-milling and crushing the dried residue at a speed of 45 r / min for 2 h, and then passing the residue through a 300 mesh sieve to obtain a fine powder for later use; (3) mixing the fine powder obtained in step (2) with the calcined waste diatomite filter aid and the slag according to the mixing ratio, slowly stirring for 0.5 minutes, and obtaining a mixed dry material; (4) pouring the remaining charcoal ash aqueous solution into the mixed dry material of step (3), slowly stirring for 0.5 minutes, then quickly stirring for 1-3 minutes, and then pouring into a mold; (5) placing the mixture in a standard curing room with a temperature of 20±2 DEG C and a relative humidity of more than 95% for 28 days after demolding and standing for 1 day.

2. The high temperature resistant solid waste based alkali activated cementitious material according to claim 1, characterized in that: The slag is a ground granulated blast furnace slag having a specific surface area greater than 400 m 2 / kg.

3. The high temperature resistant solid waste based alkali activated cementitious material according to claim 1, characterized in that: The total content of SiO2, Al2O3 and CaO in the household garbage incineration bottom ash is greater than or equal to 70%.

4. The high temperature resistant solid waste based alkali activated cementitious material as claimed in claim 1, wherein: The charcoal ash is a waste residue produced by burning wood or wood products, and the particle size range is 200-300 mesh, wherein the content of K2CO3 is not less than 80%.

5. The high temperature resistant solid waste based alkali activated cementitious material as claimed in claim 1, wherein: The speed of the slow stirring is 62±5 r / min, and the speed of the quick stirring is 285±10 r / min.

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