Method for activating all components of waste concrete, recycled activated powder and application

Abstract

The application discloses a kind of waste concrete full-component activation treatment method, reactivated powder and application.The waste concrete full-component activation treatment method includes the following steps: waste concrete full-component is broken and ground, and pretreated powder is obtained;The pretreated powder is activated at low temperature, and then cooled, and reactivated powder is obtained.The application is surface activated modification to the whole component of waste concrete, and a large number of active nanoparticles are generated on the surface of powder, which significantly improves the interface bonding of reactivated powder, new mineral admixture and cement paste;And the full-component crushing, screening treatment mode simplifies the traditional waste concrete treatment process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste concrete recycling, and in particular to a full-component activation treatment method of waste concrete, a recycled activated powder and application. BACKGROUND

[0002] With the rapid advancement of global urbanization and the continuous development of the construction industry, the amount of construction waste is increasing. According to statistics, billions of tons of construction waste are generated worldwide every year. If these waste concretes are not effectively disposed of and utilized, not only will they occupy a large amount of land resources, but they may also have a serious negative impact on the environment, such as dust pollution, soil erosion, etc. At the same time, the demand for natural aggregates, cement and other raw materials in the construction industry is also growing, leading to overexploitation of natural resources, further exacerbating environmental pressure. Under such circumstances, developing recycling technology for waste concrete has become a problem to be solved, which not only can alleviate the environmental problems caused by waste disposal, but also can reduce the consumption of natural resources, with significant economic and ecological benefits.

[0003] At present, the recycling of waste concrete mainly focuses on the preparation of recycled micro-powder and recycled aggregate after crushing and screening of waste concrete, and its application in the production of recycled concrete or in the field of road base. However, the performance of recycled aggregate and recycled concrete is often difficult to compare with that of natural aggregate and ordinary concrete, which is mainly due to the adverse effects of residual cement paste and impurities in waste concrete on the performance of recycled aggregate, and the separation technology of recycled aggregate and recycled micro-powder is not mature, which hinders the recycling of waste concrete.

[0004] Therefore, it is urgent to develop new waste concrete treatment technology to simplify the treatment process, expand the application range of waste concrete, realize the high-value utilization of waste concrete, and promote the resource utilization of construction waste and the green development of the construction industry. SUMMARY

[0005] The present application aims to overcome the above technical deficiencies and provide a full-component activation treatment method of waste concrete, a recycled activated powder and application, which solves the technical problems of complex waste concrete treatment process and poor interfacial bonding of existing recycled aggregate in the prior art.

[0006] In a first aspect, the present application provides a full-component activation treatment method of waste concrete, comprising the following steps:

[0007] The full components of waste concrete are crushed and ground to obtain pretreated powder;

[0008] The pretreated powder is subjected to low-temperature activation treatment, followed by cooling to obtain a recycled activated powder.

[0009] In a second aspect, the present application provides a reactivated powder obtained by the full-component activation treatment method of waste concrete according to the first aspect of the present application.

[0010] In a third aspect, the present application provides the use of the reactivated powder described above, which is used as a cementitious component in recycled concrete.

[0011] Compared with the prior art, the present application has the following beneficial effects:

[0012] The present application significantly improves the interfacial bonding between the reactivated powder and new mineral admixtures and cement paste by surface activation modification of all components of waste concrete, which produces a large number of active nanoparticles on the surface of the powder; and the full-component crushing and screening treatment simplifies the traditional waste concrete treatment process. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a 28d compressive strength chart of the recycled concrete test blocks F1-F13 obtained in Examples 1-5 and Comparative Examples 1-8 of the present application;

[0014] Figure 2 is a SEM chart of the reactivated powder obtained in Example 6 of the present application;

[0015] Figure 3 is a SEM chart of the reactivated powder obtained in Comparative Example 9 of the present application;

[0016] Figure 4 is a SEM chart of the reactivated powder obtained in Comparative Example 10 of the present application;

[0017] Figure 5 is a SEM chart of the reactivated powder obtained in Comparative Example 11 of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0019] In a first aspect, the present application provides a full-component activation treatment method of waste concrete, which comprises the following steps:

[0020] The full components of waste concrete are crushed and ground to obtain a pretreated powder;

[0021] The pretreated powder is subjected to low-temperature activation treatment, followed by cooling, to obtain a reactivated powder.

[0022] The application improves the interface combination of the recycled activated powder, new mineral admixture and cement paste by surface activation modification of all components of the waste concrete, and a large number of active nanoparticles are generated on the powder surface; moreover, the crushing and screening treatment of all components simplifies the traditional waste concrete treatment process; in particular, the surface of calcium carbonate and gel components in the waste concrete is activated, and the generated free calcium oxide and high-activity silica gel have significant cementitious activity, and a large amount of gel and ettringite reaction products fill the pores and optimize the reaction interface, thereby promoting the strength development of the recycled concrete; the application is different from the traditional recycled concrete treatment process and expands the application range of the waste concrete.

[0023] In the embodiment, the particle size of the pretreated powder is ≤ 150 μm.

[0024] In the embodiment, the low-temperature activation treatment is performed by calcining the pretreated powder at a heating rate of 5-20 ℃ / min, including but not limited to 5 ℃ / min, 10 ℃ / min, 15 ℃ / min, 20 ℃ / min, etc., at a calcining temperature of 750-950 ℃, including but not limited to 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, etc., for a calcining time of 0-10 min, including but not limited to 0 min, 2 min, 4 min, 6 min, 8 min, 10 min, etc. The application can make the obtained recycled activated powder have good activation effect by controlling the low-activation parameters in the above range. If the calcining temperature is too low, the activation effect on the powder is insufficient; if the calcining temperature is too high or the calcining time is too long, the activity will be greatly reduced.

[0025] In the embodiment, the rapid cooling is adopted, and the rapid cooling process is cooling to room temperature for 3-5 min.

[0026] In the embodiment, the rapid cooling is fan quenching.

[0027] In the second aspect, the application provides a recycled activated powder obtained by the activation treatment method of the waste concrete all components provided in the first aspect of the application.

[0028] In the third aspect, the application provides the application of the above-mentioned recycled activated powder, which is applied as a cementitious component in recycled concrete.

[0029] Further, the raw materials of the recycled concrete further include cement and / or mineral admixtures.

[0030] Further, the recycled powder accounts for 0.1-100% of the total mass of the recycled powder, cement and mineral admixture, including but not limited to 0.1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.

[0031] Further, the cement accounts for 0-99.9% of the total mass of the recycled powder, cement and mineral admixture, including but not limited to 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99.9%, etc.

[0032] Further, the mineral admixture accounts for 0-99.9% of the total mass of the recycled powder, cement and mineral admixture, including but not limited to 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99.9%, etc.

[0033] Further, the raw material of the recycled concrete further includes: aggregate.

[0034] Further, the aggregate accounts for 0-70% of the total mass of the recycled powder, cement and mineral admixture, including but not limited to 0, 10%, 20%, 30%, 40%, 50%, 60%, 70%, etc.

[0035] Further, the raw material of the recycled concrete further includes: water reducing agent.

[0036] Further, the water reducing agent is a polycarboxylic acid water reducing agent.

[0037] Further, the solid content of the water reducing agent is 30-50%, including but not limited to 30%, 35%, 40%, 45%, 50%, etc.

[0038] Further, the water reducing agent accounts for 0.1-5% of the total mass of the recycled powder, cement and mineral admixture, including but not limited to 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0039] Further, the raw material of the recycled concrete further includes: water.

[0040] Further, the water accounts for 30-50% of the total mass of the recycled powder, cement and mineral admixture.

[0041] To avoid redundancy, in the following examples and comparative examples of the present application, some raw materials are summarized as follows:

[0042] The polycarboxylic acid water reducing agent used has a solid content of 40%;

[0043] The source of the waste concrete used is obtained from the demolition of old buildings, which is crushed and ground. The chemical composition is determined by X-ray fluorescence spectrometer (Zetium, Malvern Panalytics), and the test results are shown in Table 1.

[0044] Table 1 Physicochemical analysis of waste concrete

[0045]

[0046] Example 1

[0047] A method for preparing recycled concrete, comprising the following steps:

[0048] Select waste concrete, crush and grind into powder with a particle size of ≤150 μm, calcine the powder in a roller-type calcining furnace, raise the temperature from room temperature to 900 °C at a rate of 10 °C / min, then rapidly cool with a fan, and cool to room temperature in 3-5 min; take 500 g of the cooled sample, add 500 g of slag, mix evenly in a stirring pot for 2 min, then add 400 g of water (water-binder ratio is 0.40) and 5 g of water reducing agent, fast stir for 3 min to obtain a slurry, and pour into a 40×40×40 mm mold. After standard curing for 28 d, test the compressive mechanical properties, denoted as F1.

[0049] Example 2

[0050] A method for preparing recycled concrete, comprising the following steps:

[0051] Select waste concrete, crush and grind into powder with a particle size of ≤150 μm, calcine the powder in a roller-type calcining furnace, raise the temperature from room temperature to 900 °C at a rate of 10 °C / min, then rapidly cool with a fan, and cool to room temperature in 3-5 min; take 500 g of the cooled sample, add 500 g of slag, mix evenly in a stirring pot for 2 min, then add 400 g of water (water-binder ratio is 0.40) and 5 g of water reducing agent, fast stir for 3 min to obtain a slurry, and pour into a 40×40×40 mm mold. After standard curing for 28 d, test the compressive mechanical properties, denoted as F1.

[0052] Example 3

[0053] A method for preparing recycled concrete, comprising the following steps:

[0054] The waste concrete is selected, is broken and is ground into the powder of ≤150 μm particle size, the powder is calcined in the roller type calcining furnace, is heated to 900 ℃ from room temperature at 10 ℃ / min, then is rapidly cooled with a fan, 3~5min is cooled to room temperature;Take 700g sample after cooling, add 300g slag, mix after slow stirring in the stirring pot for 2 minutes, add 400g water (water binder ratio is 0.40) and 5g water reducing agent fast stirring 3min to obtain the slurry, and is poured into the mold of 40×40×40mm, after standard curing 28d, the compressive mechanical property test is carried out, and is recorded as F3.

[0055] Example 4

[0056] A preparation method of recycled concrete, comprising the following steps:

[0057] The waste concrete is selected, is broken and is ground into the powder of ≤150 μm particle size, the powder is calcined in the roller type calcining furnace, is heated to 750 ℃ from room temperature at 10 ℃ / min, then is rapidly cooled with a fan, 3~5min is cooled to room temperature;Take 500g sample after cooling, add 500g slag, mix after slow stirring in the stirring pot for 2 minutes, add 400g water (water binder ratio is 0.40) and 5g water reducing agent fast stirring 3min to obtain the slurry, and is poured into the mold of 40×40×40mm, after standard curing 28d, the compressive mechanical property test is carried out, and is recorded as F4.

[0058] Example 5

[0059] A preparation method of recycled concrete, comprising the following steps:

[0060] The waste concrete is selected, is broken and is ground into the powder of ≤150 μm particle size, the powder is calcined in the roller type calcining furnace, is heated to 950 ℃ from room temperature at 10 ℃ / min, then is rapidly cooled with a fan, 3~5min is cooled to room temperature;Take 500g sample after cooling, add 500g slag, mix after slow stirring in the stirring pot for 2 minutes, add 400g water (water binder ratio is 0.40) and 5g water reducing agent fast stirring 3min to obtain the slurry, and is poured into the mold of 40×40×40mm, after standard curing 28d, the compressive mechanical property test is carried out, and is recorded as F5.

[0061] Example 6

[0062] A full-component activation treatment method of waste concrete, comprising the following steps:

[0063] The waste concrete is selected, is broken and is ground into the powder of ≤150 μm particle size, the powder is calcined in the roller type calcining furnace, is heated to 900 ℃ from room temperature at 10 ℃ / min, then is rapidly cooled with a fan, 3~5min is cooled to room temperature, under 20000 times magnification, the powder surface morphology is observed asFigure 2 as shown.

[0064] Comparative Example 1

[0065] A method for preparing recycled concrete, comprising the following steps:

[0066] Selecting waste concrete, crushing and grinding into powder with a particle size of ≤ 150 μm, taking 500 g of sample, adding 500 g of slag, stirring in a pot for two minutes, adding 400 g of water (water-binder ratio of 0.40) and 5 g of water reducing agent, stirring for 3 min to obtain a slurry, and pouring into a 40x40x40mm mold, and after standard curing for 28d, the compressive mechanical property test is performed, recorded as F6.

[0067] Comparative Example 2

[0068] A method for preparing recycled concrete, comprising the following steps:

[0069] Selecting waste concrete, crushing and grinding into powder with a particle size of ≤ 150 μm, taking 250 g of sample, adding 500 g (PO425) cement and 250 g of slag, stirring in a pot for two minutes, adding 400 g of water (water-binder ratio of 0.40) and 5 g of water reducing agent, stirring for 3 min to obtain a slurry, and pouring into a 40x40x40mm mold, and after standard curing for 28d, the compressive mechanical property test is performed, recorded as F7.

[0070] Comparative Example 3

[0071] A method for preparing recycled concrete, comprising the following steps:

[0072] Selecting waste concrete, crushing and grinding into powder with a particle size of ≤ 150 μm, taking 700 g of sample, adding 300 g of slag, stirring in a pot for two minutes, adding 400 g of water (water-binder ratio of 0.40) and 5 g of water reducing agent, stirring for 3 min to obtain a slurry, and pouring into a 40x40x40mm mold, and after standard curing for 28d, the compressive mechanical property test is performed, recorded as F8.

[0073] Comparative Example 4

[0074] A method for preparing recycled concrete, comprising the following steps:

[0075] Selecting waste concrete, after preliminary crushing, sorting, removing large particles such as sand and gravel aggregate, then ball milling the remaining cement stone components, and sieving out the powder with a particle size of ≤150 μm as recycled powder, taking 500g of recycled powder, adding 500g of slag, stirring in a pot for two minutes, then adding 400g of water (water-binder ratio is 0.40) and 5g of water reducing agent, stirring for 3min to obtain a slurry, and pouring into a 40x40x40mm mold, after standard curing for 28d, the compressive mechanical property test is recorded as F9.

[0076] Comparative example 5

[0077] A method for preparing recycled concrete, comprising the following steps:

[0078] Selecting waste concrete, after preliminary crushing, sorting, removing large particles such as sand and gravel aggregate, then ball milling the remaining cement stone components, and sieving out the powder with a particle size of ≤150 μm as recycled powder, taking 500g of recycled powder, adding 500g of slag, stirring in a pot for two minutes, then adding 400g of water (water-binder ratio is 0.40) and 5g of water reducing agent, stirring for 3min to obtain a slurry, and pouring into a 40x40x40mm mold, after standard curing for 28d, the compressive mechanical property test is recorded as F9.

[0079] Comparative example 6

[0080] A method for preparing recycled concrete, comprising the following steps:

[0081] Selecting waste concrete, crushing and grinding into a powder with a particle size of ≤150 μm, using a roller type calcining furnace to heat from room temperature to 900℃ at a rate of 10℃ / min, keeping the temperature for 20min, then rapidly cooling with a fan, cooling to room temperature for 3~5min, taking 500g of the cooled sample, adding 500g of slag, stirring in a pot for two minutes, then adding 400g of water (water-binder ratio is 0.40) and 5g of water reducing agent, stirring for 3min to obtain a slurry, and pouring into a 40x40x40mm mold, after standard curing for 28d, the compressive mechanical property test is recorded as F11.

[0082] Comparative example 7

[0083] A method for preparing recycled concrete, comprising the following steps:

[0084] Select the waste concrete, broken into a particle size of ≤ 150 μm powder, using a roller type calcining furnace at a heating rate of 10 ℃ / min from room temperature to 1000 ℃, and then use the fan to quench, 3~5min cooling to room temperature, take the cooled 500g sample, add 500g slag, mix in a stirring pot for two minutes, then add 400g water (water binder ratio is 0.40) and 5g water reducing agent fast stirring 3min to get the slurry, and cast into 40×40×40mm mold, standard curing 28d, then test the compressive mechanical properties, recorded as F12.

[0085] Comparative Example 8

[0086] A method for preparing recycled concrete, comprising the following steps:

[0087] Select the waste concrete, broken into a particle size of ≤ 150 μm powder, using a roller type calcining furnace at a heating rate of 10 ℃ / min from room temperature to 900 ℃, and then use the fan to quench, 3~5min cooling to room temperature, take the cooled 500g sample, add 500g slag, mix in a stirring pot for two minutes, then add 400g water (water binder ratio is 0.40) and 5g water reducing agent fast stirring 3min to get the slurry, and cast into 40×40×40mm mold, standard curing 28d, then test the compressive mechanical properties, recorded as F13.

[0088] Comparative Example 9

[0089] A method for activating all components of waste concrete, comprising the following steps:

[0090] Select the waste concrete, broken into a particle size of ≤ 150 μm powder, using a roller type calcining furnace at a heating rate of 10 ℃ / min from room temperature to 700 ℃, and then use the fan to quench, 3~5min cooling to room temperature, and observe the surface morphology of the powder under 20000 times magnification as shown in Figure 3 .

[0091] Comparative Example 10

[0092] A method for activating all components of waste concrete, comprising the following steps:

[0093] Select the waste concrete, broken into a particle size of ≤ 150 μm powder, using a roller type calcining furnace at a heating rate of 10 ℃ / min from room temperature to 1000 ℃, and then use the fan to quench, 3~5min cooling to room temperature, and observe the surface morphology of the powder under 20000 times magnification as shown in Figure 4 .

[0094] Comparative Example 11

[0095] A method for activating all components of waste concrete, comprising the following steps:

[0096] The waste concrete is selected, crushed and ground into a powder with a particle size of ≤ 150 μm, a roller-type calcining furnace is used to raise the temperature from room temperature to 900 ℃ at a rate of 10 ℃ / min, and the furnace is cooled to room temperature for about 5 h, and the powder surface morphology is observed under magnification of 20000 times as shown in Figure 5 .

[0097] Please refer to Figure 1 , Figure 1 is a diagram of the 28d compressive strength of the recycled concrete test blocks F1-F13 obtained in Examples 1-5 and Comparative Examples 1-8 of the present application. It can be seen from Figure 1 that F1-F5 have a significant increase in compressive strength compared to the comparative examples F6-F8 which are not activated. This is because the free calcium oxide, high-activity silica gel and other products produced after surface activation of calcium carbonate, gel and other components in the waste concrete have significant cementitious activity, and at the same time, a large amount of gel, ettringite and other reaction products fill the pores and optimize the reaction interface, ultimately promoting the strength development of the high-surface-activity recycled concrete. Then, compared to the F9 and F10 groups which use recycled micro-powder, the F1 and F2 groups have higher mechanical properties, because the activated recycled powder after activation treatment can effectively stimulate slag and promote the progress of pozzolanic reaction, thus promoting the strength development. Finally, for the F11-F13 groups, compared to the treatment method of F1, F11 increases the holding time at 900 ℃, F12 increases the calcination temperature to 1000 ℃, and F13 adopts the method of cooling with the furnace at 900 ℃, and the strength of the three groups decreases significantly, because the calcination time of the carbonate components reaching the decomposition temperature (above 700 ℃) is increased, which leads to an increase in calcination degree, and the nanoparticles formed on the surface tend to aggregate, thus leading to an increase in size and a decrease in activity.

[0098] Please refer to Figures 2-5 , Figures 2-5 are the surface morphologies of the recycled activated powder obtained after treating the whole components of the waste concrete at different temperatures or different cooling methods in Example 6 and Comparative Examples 9-11, respectively. It can be seen from Figure 2 that under the system of Example 6, the sample surface has a large number of active calcium oxide and magnesium oxide particles of about 50 nm; it can be seen from Figure 3 that when the temperature is lowered, the surface does not change because no reaction occurs; and it can be seen from Figure 4 and 5 that when the treatment temperature is increased or no rapid cooling is used, the nanoparticles tend to aggregate and the particle size increases, resulting in a decrease in activity.

[0099] In summary, compared with the prior art, the beneficial effects of the present application include:

[0100] (1) The present application activates the calcium carbonate, gel and other components in the waste concrete by surface activation treatment technology, and the generated free calcium oxide and high-activity silica gel have significant cementitious activity. At the same time, a large amount of gel and ettringite reaction products fill the pores and optimize the reaction interface, ultimately promoting the strength development of the recycled concrete.

[0101] (2) The present application activates the calcium carbonate, gel and other components in the waste concrete by surface activation treatment technology, and the generated free calcium oxide and high-activity silica gel have significant cementitious activity. At the same time, a large amount of gel and ettringite reaction products fill the pores and optimize the reaction interface, ultimately promoting the strength development of the recycled concrete.

[0102] (3) The present application simplifies the traditional waste concrete treatment process by adopting the whole component crushing and screening treatment method. This technology is expected to promote the high-value utilization of waste concrete and provide new ideas and methods for the resource utilization of construction waste.

[0103] (4) The recycled waste concrete prepared by the present application can be applied to various cement concrete fields such as buildings, roads and bridges.

[0104] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made in accordance with the technical concept of the present application should be included within the scope of protection of the claims of the present application.

[0105] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made in accordance with the technical concept of the present application should be included within the scope of protection of the claims of the present application.

Claims

1. A method for activating all components of waste concrete, characterized by, The method comprises the following steps: crushing and grinding the whole component of waste concrete to obtain pretreated powder; carrying out low-temperature activation treatment on the pretreated powder, and then cooling to obtain activated powder; wherein the low-temperature activation treatment is carried out by calcining the pretreated powder at a heating rate of 5-20 ℃ / min, a calcining temperature of 750-950 ℃, and a calcining time of 0-10 min.

2. The method for activating the entire components of the waste concrete according to claim 1, wherein The particle size of the pretreated powder is ≤150 μm.

3. The method of claim 1, wherein the waste concrete is activated by the full composition of the activator. rapid cooling is adopted, and the rapid cooling process is cooling to room temperature in 3-5 min.

4. A recycled powder characterized by, The activated powder is obtained by the activation treatment method of the whole component of waste concrete according to any one of claims 1-3.

5. Use of a reactivated powder, characterized in that, The activated powder is used as a cementitious component in recycled concrete.

6. Use of the reactivated powder according to claim 5, characterized in that, The raw materials of the recycled concrete further comprise cement and / or mineral admixtures; wherein the activated powder accounts for 0.1-100% of the total mass of the activated powder, cement and mineral admixtures; the cement accounts for 0-99.9% of the total mass of the activated powder, cement and mineral admixtures; the mineral admixtures account for 0-99.9% of the total mass of the activated powder, cement and mineral admixtures.

7. The use of the reactivated powder according to claim 5, characterized in that, The raw materials of the recycled concrete further comprise aggregate; wherein the aggregate accounts for 0-70% of the total mass of the activated powder, cement and mineral admixtures.

8. The use of the reactivated powder according to claim 5, characterized in that, The raw materials of the recycled concrete further comprise water reducing agent; wherein the water reducing agent is polycarboxylic acid water reducing agent; and / or the solid content of the water reducing agent is 30%-50%; and / or the water reducing agent accounts for 0.1%-5% of the total mass of the activated powder, cement and mineral admixtures.

9. The use of the reactivated powder according to claim 5, characterized in that, The raw materials of the recycled concrete further comprise water; wherein the water accounts for 30%-50% of the total mass of the activated powder, cement and mineral admixtures.

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