A modified activated carbon-activated slag composite cementitious material, preparation method and application thereof

Abstract

The present invention relates to a modified activated carbon-activated slag composite cementitious material, a preparation method and application thereof, wherein the modified activated carbon-activated slag composite cementitious material comprises an activator and a precursor. The activator is modified activated carbon, and the precursor is slag. According to the mass fraction, the modified activated carbon-activated slag composite cementitious material comprises 20-40% of the activator. The modified activated carbon is prepared by carbonizing coffee skins, mixing with a strong base and then heating and activating the same. The modified activated carbon-activated slag composite cementitious material of the present invention uses the modified activated carbon prepared by carbonizing coffee skins, mixing with a strong base and then heating and activating the same as the activator of the slag, and the activated carbon modified by the strong base as the activator of the slag, which can avoid the occurrence of alkali efflorescence and carbonization during use, can improve the corrosion resistance and durability of buildings, and avoid environmental pollution caused by alkali efflorescence and carbonization.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste utilization, and in particular to a modified activated carbon-activated slag composite gelling material, a preparation method and application thereof. Background Art

[0002] The stacking of slag and waste glass will not only occupy a large amount of land, but also cause harm to the soil environment and water resources, so the proper treatment of slag is an urgent problem to be solved. In the prior art, slag can be applied on a large scale to alkali-activated composite cementitious materials to effectively alleviate the environmental pollution and land occupation caused by slag accumulation or landfill, and realize the recycling of solid waste. At present, alkali-activated cementitious materials are highly active and rapidly developed in global research and development. Alkali-activated cementitious materials can replace cement, which can not only reduce carbon dioxide emissions and energy consumption, but also recycle waste materials such as slag, fly ash, mineral powder and glass powder, so alkali-activated cementitious materials have received widespread attention as a substitute for cement.

[0003] In the prior art, alkali-activated slag cementitious materials can be prepared using strong alkalis such as water glass, sodium hydroxide, potassium hydroxide, or a mixture of water glass and strong alkali as an activator. However, the cost of using water glass as an activator is relatively high, and the production of water glass causes great environmental pollution. In addition, when the alkali-activated slag cementitious materials obtained using water glass or strong alkali as an alkali activator are used in building materials, there are also alkali-efflorescence and carbonization phenomena. The alkali-efflorescence phenomenon is manifested as the alkali activator seeping out on the surface of the material, and the carbonization phenomenon is manifested as the reaction of carbon dioxide with the alkali activator. The alkali-efflorescence and carbonization phenomena will not only reduce the corrosion resistance and durability of the building, but also pollute the surrounding environment.

[0004] Therefore, there is a need for a slag cementitious material that can avoid efflorescence and carbonization. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the above technical problems, in order to solve the problem that the existing alkali-activated slag cementitious materials are prone to efflorescence and carbonization, which reduces the corrosion resistance and durability of buildings and causes pollution, the present invention provides a modified activated carbon-activated slag composite cementitious material, its preparation method and application.

[0007] (II) Technical solution

[0008] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, the present invention provides a modified activated carbon activated slag composite cementitious material, comprising an activator and a precursor;

[0010] The activator is modified activated carbon, and the precursor is slag; the modified activated carbon activated slag composite cementitious material includes 20-40% of the activator in terms of mass fraction;

[0011] The modified activated carbon is prepared by subjecting coffee peels to carbonization treatment, mixing with a strong base, and then heating and activating treatment.

[0012] The modified activated carbon activated slag composite cementitious material as described above, preferably, comprises 30-40% of the activator in terms of mass fraction.

[0013] The modified activated carbon activated slag composite cementitious material as described above, preferably, the specific surface area of ​​the slag is 300-400m 2 / kg, the density of slag is 2.3-3.0g / cm 3 .

[0014] In a second aspect, the present invention provides a method for preparing the modified activated carbon activated slag composite cementitious material, comprising the following steps:

[0015] S1: Carbonizing coffee skins under anaerobic conditions to obtain activated carbon;

[0016] S2: adding a strong base to the activated carbon, and then heating and activating the activated carbon-strong base mixed system under anaerobic conditions to obtain modified activated carbon; in this step, the mass ratio of the strong base to the activated carbon is 2:1-4:1;

[0017] S3: grinding the modified activated carbon to obtain modified activated carbon powder;

[0018] S4: adding slag to the modified activated carbon powder to obtain a modified activated carbon-activated slag composite cementitious material; in terms of mass fraction, the modified activated carbon powder accounts for 20-40% of the modified activated carbon-activated slag composite cementitious material.

[0019] In the preparation method as described above, preferably, in step S1, the temperature is raised to 400-450°C at a rate of 5-10°C / min in an anaerobic environment and kept warm for 30-40 minutes.

[0020] In the preparation method as described above, preferably, in step S2, the temperature is raised to 450-550° C. at a heating rate of 5-10° C. / min in an anaerobic environment and kept warm for 50-60 min.

[0021] In the preparation method as described above, preferably, in step S2, the strong base is potassium hydroxide or sodium hydroxide;

[0022] In step S2, after adding a strong base to the activated carbon, deionized water is continuously added and stirred evenly; the solid-liquid ratio of the strong base to the activated carbon to the deionized water is 1:2-1:3.

[0023] In the preparation method as described above, preferably, in step S3, the modified activated carbon is ground to 50-200 mesh.

[0024] In the preparation method as described above, preferably, before step S1, the coffee skins are cleaned and dried.

[0025] In a third aspect, the present invention also provides an application of the modified activated carbon-activated slag composite cementitious material or the modified activated carbon-activated slag composite cementitious material prepared by the above-mentioned preparation method. Specifically, the modified activated carbon-activated slag composite cementitious material is used to replace silicate cement.

[0026] (III) Beneficial effects

[0027] Firstly, the modified activated carbon-activated slag composite cementitious material of the present invention uses the modified activated carbon prepared by carbonizing coffee skins, mixing with a strong alkali and then heating and activating the carbonized coffee skins as the activator of the slag, which can avoid the occurrence of alkali efflorescence and carbonization during use, improve the corrosion resistance and durability of the building, and avoid environmental pollution caused by alkali efflorescence and carbonization. In addition, using the modified activated carbon of the present invention as the activator of the slag can further slow down the setting time of the composite cementitious material, which is conducive to the promotion and application of the composite cementitious material.

[0028] Secondly, the modified activated carbon-activated slag composite cementitious material of the present invention uses modified activated carbon as an activator for slag, providing an effective way for solid waste recycling of slag and coffee skins. Therefore, the modified activated carbon-activated slag composite cementitious material of the present invention has good economic, social and environmental benefits, and is suitable for large-scale promotion and application.

[0029] Thirdly, the mechanical properties and working performance of the modified activated carbon-activated slag composite cementitious material of the present invention can meet the requirements of ordinary Portland cement. Therefore, the modified activated carbon-activated slag composite cementitious material of the present invention can replace ordinary Portland cement, reduce the use of cement, and has the advantages of energy saving, environmental protection, low cost, etc.

[0030] In addition, compared with using water glass as an alkali activator, the modified activated carbon-activated slag composite cementitious material of the present invention uses activated carbon modified with a strong alkali as an activator, which can also reduce production costs and has better economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the SEM image of the modified activated carbon prepared in Example 1;

[0032] Figure 2 This is a SEM image of the activated carbon prepared in step S1 of Comparative Example 1;

[0033] Figure 3 This is the thermogravimetric diagram of the modified activated carbon in Example 1. DETAILED DESCRIPTION

[0034] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific implementation methods.

[0035] The present invention provides a modified activated carbon activated slag composite cementitious material, comprising an activator and a precursor. The activator is modified activated carbon, and the precursor is slag. According to the mass fraction, the modified activated carbon activated slag composite cementitious material comprises 20-40% of the activator, preferably 30-40% of the activator, and more preferably 30% of the activator. The modified activated carbon in the present invention is prepared by carbonizing coffee skin, mixing with a strong base, and then heating and activating.

[0036] The specific surface area of ​​the slag used in the present invention can be 300-400m 2 / kg, the density of slag can be 2.3-3.0g / cm 3 .

[0037] The present invention also provides a method for preparing the modified activated carbon activated slag composite gelling material, comprising the following steps:

[0038] S1: Washing the coffee skin and drying it, and carbonizing the coffee skin under anaerobic conditions to obtain activated carbon. Carbonization can convert the coffee skin into activated carbon. In this step, the temperature is raised to 400-450°C at a rate of 5-10°C / min under an anaerobic environment, kept at this temperature for 30-40 minutes, and then cooled to room temperature.

[0039] S2: Add a strong base to the activated carbon, and then heat and activate the activated carbon-strong base mixed system under anaerobic conditions to obtain modified activated carbon; in this step, the mass ratio of strong base to activated carbon is 2:1-4:1. In this step, adding a strong base and heating and activating the activated carbon can further modify the activated carbon, making the pore structure and surface functional groups of the activated carbon richer. In addition, the addition of a strong base and the heating and activation treatment in this step are the key factors to solve the alkali efflux and carbonization problems. If activated carbon that has not been treated with a strong base and heating and activation is used, the slag composite cementitious material cannot stimulate the activity of the slag at all, and the mixed material has no strength. It is even more impossible to solve the alkali efflux and carbonization phenomena of the existing alkali activators, and it is impossible to improve the corrosion resistance and durability of the building. In this step, the temperature is raised to 450-550°C at a heating rate of 5-10°C / min under an anaerobic environment, and the temperature is kept for 50-60 minutes.

[0040] In addition, in step S2, the strong base can be potassium hydroxide or sodium hydroxide. After adding the strong base to the activated carbon, deionized water is added and stirred evenly. The solid-liquid ratio of the strong base, the activated carbon and the deionized water is 1:2-1:3.

[0041] S3: After the heating activation treatment, the mixture is cooled to room temperature, and then the modified activated carbon is ground, preferably to 50-200 meshes, to obtain modified activated carbon powder, which can be sealed in a drying container for later use.

[0042] S4: Add slag to the modified activated carbon powder to obtain a modified activated carbon activated slag composite cementitious material. The particle size of the slag is preferably 50-200 mesh. In terms of mass fraction, the modified activated carbon powder accounts for 20-40% of the modified activated carbon activated slag composite cementitious material, preferably 30-40%, and more preferably 30%. In this step, the proportion of the modified activated carbon powder in the composite cementitious material is also a key factor in solving the alkali efflux and carbonization problems. When the modified activated carbon powder accounts for less than 30% of the total amount of the composite cementitious material, or accounts for more than 40% of the total amount of the composite cementitious material, the mechanical properties, corrosion resistance and durability of the composite cementitious material will be significantly reduced.

[0043] The specific surface area of ​​the modified activated carbon prepared by the present invention is 1500-1699m 2 / kg, with a large specific surface area and rich pore structure. Modified activated carbon is strongly alkaline, which can provide an alkaline environment, promote the production of inorganic substances with gelling properties such as dicalcium silicate and tricalcium silicate, and improve early strength.

[0044] In the present invention, the modified activated carbon-activated slag composite cementitious material or the modified activated carbon-activated slag composite cementitious material prepared by the above-mentioned preparation method can be used to replace ordinary Portland cement. In addition, cement as a cementitious material will release a large amount of heat during the coagulation process, which will cause the building materials to crack easily under the principle of thermal expansion and contraction. The modified activated carbon-activated slag composite cementitious material of the present invention can be used to replace ordinary Portland cement, and the modified activated carbon-activated slag composite cementitious material of the present invention releases less heat during the coagulation process than the cement system, so it can also avoid cracking of buildings.

[0045] Example 1

[0046] This embodiment provides a method for preparing a modified activated carbon activated slag composite cementitious material, comprising the following steps:

[0047] S1: The coffee skins are washed with deionized water and then dried. The dried coffee skins are then placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min in an anaerobic environment. The mixture is carbonized for 30 minutes to obtain activated carbon.

[0048] S2: Potassium hydroxide and activated carbon are mixed in a mass ratio of 3:1, and then deionized water is added in a solid-liquid ratio of 1:2. After stirring evenly, the mixed system is heated to 450°C at a heating rate of 10°C / min under anaerobic conditions, heated for activation treatment for 60 minutes, and then cooled to room temperature to obtain modified activated carbon.

[0049] S3: The dried modified activated carbon is placed in a pulverizer and crushed, then passed through a 200-mesh sieve, and the obtained modified activated carbon powder (MAC) is collected in a sealed container.

[0050] S4: Weigh the sieved modified activated carbon powder and 200-mesh slag into a stirrer, mix and stir at room temperature, the stirring speed is 60r / min, the stirring time is 2min, and a dry powder mixture is obtained. Among them, the mass ratio of modified activated carbon powder to slag is 30:70. Use a stirrer to mix the obtained dry powder mixture with water at room temperature, stir at low speed for 1min, and then stir at high speed for 2min. The water-to-binder ratio (the mass ratio of the added water to the dry powder mixture) is 30:100, and a gray gelled substance is obtained.

[0051] The obtained gray gelled material is then poured into a 25mm×25mm×25mm mold and vibrated to be compacted. After vibration compaction, a layer of plastic wrap is covered on the surface of the mold. After being placed for one day, the mold is removed. After demolding, the specimen is placed in an environment with a relative humidity of ≥95wt% and 20±2℃ for curing.

[0052] Example 2

[0053] This embodiment provides a method for preparing a modified activated carbon activated slag composite cementitious material, comprising the following steps:

[0054] S1: The coffee skins are washed with deionized water and then dried. The dried coffee skins are then placed in a muffle furnace and heated to 450°C at a heating rate of 5°C / min in an anaerobic environment. The activated carbon is carbonized for 40 minutes.

[0055] S2: Potassium hydroxide and activated carbon are mixed in a mass ratio of 2:1, and then deionized water is added in a solid-liquid ratio of 1:3. After stirring evenly, the mixed system is heated to 550°C at a heating rate of 8°C / min under anaerobic conditions, heated for activation treatment for 50 minutes, and cooled to room temperature to obtain modified activated carbon.

[0056] S3: Put the dried modified activated carbon into a pulverizer for crushing and then pass it through a 150-mesh sieve, and collect the obtained modified activated carbon powder in a sealed container.

[0057] S4: Weigh the sieved modified activated carbon powder and 150 mesh slag into a stirrer, mix and stir at room temperature, the stirring speed is 60r / min, the stirring time is 2min, and a dry powder mixture is obtained. Among them, the mass ratio of modified activated carbon powder to slag is 30:70. Use a stirrer to mix the obtained dry powder mixture with water at room temperature, stir at low speed for 1min, and then stir at high speed for 2min, the water-to-binder ratio is 30:100, and a gray gelled substance is obtained.

[0058] The obtained gray gelled material is then poured into a 25mm×25mm×25mm mold and vibrated to be compacted. After vibration compaction, a layer of plastic wrap is covered on the surface of the mold. After being placed for one day, the mold is removed. After demolding, the specimen is placed in an environment with a relative humidity of ≥95wt% and 20±2℃ for curing.

[0059] Example 3

[0060] This embodiment provides a method for preparing a modified activated carbon activated slag composite cementitious material, comprising the following steps:

[0061] S1: The coffee skins were washed with deionized water and then dried. The dried coffee skins were then placed in a muffle furnace and heated to 420°C at a heating rate of 8°C / min in an anaerobic environment. The activated carbon was carbonized for 35 minutes.

[0062] S2: Potassium hydroxide and activated carbon are mixed in a mass ratio of 4:1, and then deionized water is added in a solid-liquid ratio of 1:2.5. After stirring evenly, the mixed system is heated to 500°C at a heating rate of 5°C / min under anaerobic conditions, heated for activation treatment for 55 minutes, and then cooled to room temperature to obtain modified activated carbon.

[0063] S3: Put the dried modified activated carbon into a pulverizer for crushing and then pass it through a 50-mesh sieve, and collect the obtained modified activated carbon powder in a sealed container.

[0064] S4: Weigh the sieved modified activated carbon powder and 50-mesh slag into a stirrer, mix and stir at room temperature, the stirring speed is 60r / min, the stirring time is 2min, and a dry powder mixture is obtained. Among them, the mass ratio of modified activated carbon powder to slag is 30:70. Use a stirrer to mix the obtained dry powder mixture with water at room temperature, stir at low speed for 1min, and then stir at high speed for 2min, the water-to-binder ratio is 30:100, and a gray gelled substance is obtained.

[0065] The obtained gray gelled material is then poured into a 25mm×25mm×25mm mold and vibrated to be compacted. After vibration compaction, a layer of plastic wrap is covered on the surface of the mold. After being placed for one day, the mold is removed. After demolding, the specimen is placed in an environment with a relative humidity of ≥95wt% and 20±2℃ for curing.

[0066] Example 4

[0067] This embodiment provides a method for preparing a modified activated carbon-activated slag composite cementitious material, which is different from Embodiment 1 in that the mass ratio of the modified activated carbon powder to the slag is 20:80.

[0068] Comparative Example 1

[0069] Comparative Example 1 provides a method for preparing an activated carbon-slag composite cementitious material, which differs from Example 1 in that in step S4, the modified activated carbon is replaced by the activated carbon prepared in step S1.

[0070] Comparative Example 2

[0071] Comparative Example 2 provides a preparation method of an alkali-activated slag composite cementitious material. The difference from Example 1 is that steps S1-S3 are omitted, and in step S4, potassium hydroxide and slag are directly poured into the agitator, the mass ratio of potassium hydroxide to slag is 22.5:140, and the water-cement ratio (the ratio of the water added in step S4 to the total mass of potassium hydroxide and slag) is 30:100.

[0072] Comparative Example 3

[0073] Comparative Example 3 provides a method for preparing an alkali-activated carbon-slag composite cementitious material. The difference from Example 1 is that steps S2-S3 are omitted, and in step S4, potassium hydroxide, the same activated carbon as in step S1, and slag are directly poured into the agitator, and the mass ratio of potassium hydroxide, activated carbon and slag is 45:15:140.

[0074] Comparative Example 4

[0075] This comparative example provides a method for preparing a modified activated carbon-activated slag composite cementitious material, which is different from Example 1 in that the mass ratio of the modified activated carbon powder to the slag is 50:50.

[0076] It should be noted that the composition (in %) of the slag used in Examples 1-4 and Comparative Examples 1-4 is shown in Table 1, wherein the contents of metal elements and non-metal elements other than oxygen in the slag are calculated as corresponding oxides.

[0077] Table 1 Composition of slag in Examples 1-4 and Comparative Examples 1-4

[0078] <![CDATA[MgO Al2O3 SiO2 SO3 K2O CaO MnO Fe2O3 TiO2 Na2O]]> Slag 6.90 15.71 31.40 1.43 0.53 38.26 1.23 0.38 2.94 0.96

[0079] It should be noted that the slag in Table 1 may contain some oxides with low contents which are difficult to detect, so the sum of the above components is less than 100%.

[0080] The oxide composition (in %) of the modified activated carbon powder prepared in Example 1 is shown in Table 2.

[0081] Table 2 Composition of modified activated carbon powder prepared in Example 1 (containing only oxides)

[0082] <![CDATA[MgO Al2O3 SiO2 SO3 K2O CaO MnO Fe2O3 TiO2 Na2O]]> MAC ---0.05 99.95-----

[0083] Performance Testing:

[0084] In Examples 1-4 and Comparative Examples 1-4, after demolding, the specimens were cured for 3 d, 7 d, 14 d and 28 d, respectively, and the compressive strength of each specimen in each time period was tested. For specific performance data, see Table 3.

[0085] Table 3 Compressive strength records of the specimens in Examples 1-4 and Comparative Examples 1-4 at different times

[0086] 3d 7d 14d 28d Example 1 19.2MPa 27.3MPa 32MPa 33.9MPa Example 2 10.2MPa 17.8MPa 18.2MPa 25.5MPa Example 3 10.6MPa 15.7MPa 11.6MPa 12.3MPa Example 4 19.8MPa 28.3MPa 30.2MPa 33.9MPa Comparative Example 1 6.5MPa 4MPa 3.6MPa 3.8MPa Comparative Example 2 25.5MPa 21.6MPa 18.5MPa 17.6MPa Comparative Example 3 37.7MPa 22.1MPa 17.6MPa 18.3MPa Comparative Example 4 8.5MPa 7.5MPa 11.2MPa 11.6MPa

[0087] It can be seen from Table 3 that the specimens of Examples 1-4 can basically reach a compressive strength of about 30Mpa after 28 days of curing, and the compressive strength of the cement specimens after 28 days of curing is also basically between 30-40Mpa. Therefore, the modified activated carbon-activated slag composite cementitious material of the present invention can replace ordinary Portland cement, reduce the use of cement, be more energy-saving and environmentally friendly, and have lower costs. Comparative Example 1 only adds ordinary activated carbon to the slag. Unlike modified activated carbon, ordinary activated carbon does not have the function of activating slag, so the mechanical properties of the specimen are poor. Comparative Example 2 uses potassium hydroxide as an alkali activator for slag. The specimen also has alkali efflux and carbonization phenomena, resulting in low corrosion resistance and durability of the specimen. Therefore, with the increase of curing time, the mechanical properties of the specimen gradually decrease. Comparative Example 3 adds potassium hydroxide and ordinary activated carbon to the slag, wherein potassium hydroxide is used as an alkaline activator for the slag, and the activated carbon does not have an activating effect, so the specimen still has alkali efflux and carbonization phenomena, and the corrosion resistance and durability of the specimen are low. Therefore, with the increase of the curing time, the mechanical properties of the specimen also show a gradual decrease. Comparative Examples 2 and 3 directly add potassium hydroxide with the same content as Example 1, which can stimulate the activity of the slag to a certain extent and have a certain strength. However, since potassium hydroxide itself is a strong alkali, directly adding slag will accelerate the coagulation time of the specimen to a certain extent, and serious alkali efflux will occur, affecting the corrosion resistance and durability of the specimen. The carbonization phenomenon will also cause many pores to appear in the specimen, which will also affect the corrosion resistance and durability of the specimen. In Comparative Example 4, due to the excessive addition of modified activated carbon, the mechanical properties of the specimen are insufficient.

[0088] The free hydroxide ions (OH - ) in the modified activated carbon, the free hydroxide ions (OH - ) in the activated carbon, the free hydroxide ions (OH - ) in potassium hydroxide, the free hydroxide ions (OH - ) to the total mass of potassium hydroxide and activated carbon and the free hydroxide ions (OH - ) was measured to determine the proportion of modified activated carbon (all ratios are by mass), and Table 4 was obtained.

[0089] Table 4 Statistics of water-to-binder ratio, free hydroxide ratio and alkali-to-carbon ratio of Examples 1-4 and Comparative Examples 1-4

[0090]

[0091]

[0092] In Table 4, W / C represents the water-to-binder ratio, OH- is the ratio of free hydroxide to activator in the composite cementitious material, and K / C is the alkali-carbon ratio (mass ratio of strong alkali to activated carbon) when the activated carbon is modified by strong alkali and activation heat treatment.

[0093] It can be seen from Table 4 that, except for Comparative Example 1, other embodiments and comparative examples all contain a certain amount of free hydroxide ions. However, combined with the mechanical properties data in Table 3, it can be seen that even though the embodiments and comparative examples except Comparative Example 1 all contain free hydroxide ions, only the modified activated carbon treated with strong alkali can avoid efflorescence and carbonization while stimulating the slag, thereby improving the corrosion resistance and durability of the composite cementitious material.

[0094] Figure 1 This is the SEM image of the modified activated carbon prepared in Example 1. Figure 2 This is a SEM image of the activated carbon prepared in step S1 of Comparative Example 1. Figure 1 It can be seen that the modified activated carbon prepared by the present invention has a three-dimensional network structure, which can fully wrap the slag inside the three-dimensional network structure for activation, and can achieve the gradual activation of the slag, so that the alkali phenomenon and carbonization phenomenon can be avoided. Figure 1 It can be seen that the three-dimensional network structure of the modified activated carbon is relatively stable, which can ensure that the mechanical properties of the composite cementitious material are maintained at a good level for a long time during use, which is consistent with the compressive strength of Example 1 in Table 3. Figure 2 It can be seen that although ordinary activated carbon that has not been modified with strong alkali also has a rich pore structure, this pore structure is irregularly distributed, the pores are fragile and easy to collapse, which will lead to poor mechanical properties of the composite cementitious material.

[0095] Figure 3 There are two obvious peaks in the thermogravimetric analysis graph. The peak at around 100°C is speculated to be due to the evaporation of water in the sample to be tested, which leads to a significant change in mass. The mass in the temperature range of 200°C-700°C shows a slight change, which is speculated to be due to the combustion of internal substances caused by the increase in temperature, resulting in a decrease in mass. The peak near 850°C is speculated to be due to the volatilization of some hydroxide compounds inside the modified activated carbon after the addition of potassium hydroxide for modification.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified activated carbon activated slag composite cementitious material, characterized in that: Including activators and precursors; The activator is modified activated carbon, and the precursor is slag; the modified activated carbon activated slag composite cementitious material includes 20-40% of the activator in terms of mass fraction; The modified activated carbon is prepared by carbonizing coffee peels, mixing with a strong base, and then heating and activating the mixture; The preparation method of the modified activated carbon activated slag composite cementitious material comprises the following steps: S1: Carbonizing coffee skins under anaerobic conditions to obtain activated carbon; S2: adding a strong base to the activated carbon, and then heating and activating the activated carbon-strong base mixed system under anaerobic conditions to obtain modified activated carbon; in this step, the mass ratio of the strong base to the activated carbon is 2:1-4:1; S3: grinding the modified activated carbon to obtain modified activated carbon powder; S4: adding slag to the modified activated carbon powder to obtain a modified activated carbon-activated slag composite cementitious material; the modified activated carbon powder accounts for 20-40% of the modified activated carbon-activated slag composite cementitious material by mass fraction; In step S1, the temperature is raised to 400-450°C at a rate of 5-10°C / min under an anaerobic environment and kept at this temperature for 30-40 minutes; In step S2, the temperature is raised to 450-550°C at a heating rate of 5-10°C / min under an anaerobic environment and kept at this temperature for 50-60 minutes; The specific surface area of ​​the modified activated carbon powder is 1500-1699m 2 / kg.

2. The modified activated carbon activated slag composite cementitious material according to claim 1, characterized in that: Calculated by mass fraction, the modified activated carbon activated slag composite cementitious material includes 30-40% of the activator.

3. The modified activated carbon activated slag composite cementitious material according to claim 1, characterized in that: The specific surface area of ​​slag is 300-400m 2 / kg, the density of slag is 2.3-3.0g / cm 3 .

4. The modified activated carbon activated slag composite cementitious material according to claim 1, characterized in that: In step S2, the strong base is potassium hydroxide or sodium hydroxide; In step S2, after adding a strong base to the activated carbon, deionized water is continuously added and stirred evenly; the solid-liquid ratio of the strong base to the activated carbon to the deionized water is 1:2-1:

3.

5. The modified activated carbon activated slag composite cementitious material according to claim 1, characterized in that: In step S3, the modified activated carbon is ground to 50-200 mesh.

6. The modified activated carbon activated slag composite cementitious material according to claim 1, characterized in that: Before step S1, the coffee skins are washed and dried.

7. The use of the modified activated carbon activated slag composite cementitious material according to any one of claims 1 to 6, characterized in that: The modified activated carbon-activated slag composite cementitious material is used to replace silicate cement.

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