Recycled aggregate strengthening method based on synergistic carbonization of household garbage incineration fly ash

Abstract

The invention discloses a recycled aggregate strengthening method based on synergistic carbonization of household garbage incineration fly ash, which comprises the following steps: mixing and stirring the household garbage incineration fly ash and a certain proportion of water, and centrifuging to obtain washed fly ash centrifugate and filter residue; performing soaking treatment on the dried recycled aggregate by adopting centrifugate, and performing carbon dioxide carbonization on the recycled aggregate soaked in the centrifugate to obtain reinforced recycled aggregate; and soaking and carbonizing the recycled aggregate for multiple times to complete all reinforcement processes of the recycled aggregate. The technical performance of the recycled aggregate is improved, the problem that the heavy metal content of the household garbage incineration fly ash is too high is solved, and permanent storage of carbon dioxide is achieved. The method effectively promotes harmlessness and recycling of the incineration fly ash of the construction wastes and the household wastes, realizes treatment of wastes with wastes, realizes three-effect synergism, and has remarkable environmental and economic benefits.

Description

Technical Field

[0001] The invention relates to a recycled aggregate strengthening method based on the coordinated carbonization of fly ash from the incineration of domestic waste, and belongs to the field of treatment, disposal and resource utilization of solid waste. Background Art

[0002] With the continuous advancement of urbanization, processing construction waste into recycled aggregates, partially or completely replacing natural aggregates to prepare concrete or mortar for house construction or road base, etc. has a good application prospect. However, the performance of concrete or mortar is highly correlated with the performance of aggregates. The inherent defects of the technical performance of recycled aggregates (with more microcracks and pores) make recycled aggregate concrete or mortar have the characteristics of poor workability, low strength, and poor durability. Recycled aggregates are also rarely used in medium and high strength concrete or mortar due to their poor technical performance. Strengthening and improving the quality of recycled aggregates is a necessary way to utilize them as high-value resources.

[0003] On the other hand, using domestic waste for incineration power generation has become the main way to deal with domestic waste. Domestic waste incineration fly ash is listed as hazardous waste by many countries because it is rich in heavy metal elements such as Pb, Zn, Cr, etc. Heavy metal stabilization treatment of waste incineration fly ash is a prerequisite for safe disposal and resource utilization of waste incineration fly ash. In addition, many industrial exhaust gases (such as domestic waste incineration, cement clinker production, etc.) contain a large amount of CO2, and improving environmental quality and reducing greenhouse gas emissions are urgent needs. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for strengthening recycled aggregates based on the coordinated carbonization of fly ash from the incineration of domestic waste, so as to achieve the performance enhancement of recycled aggregates from construction waste, reduce the heavy metal content of fly ash from the incineration of domestic waste, and permanently seal up CO2.

[0005] Technical solution: The method for strengthening recycled aggregate based on the coordinated carbonization of fly ash from the incineration of domestic waste described in the present invention comprises the following steps:

[0006] (1) dissolving fly ash from the incineration of domestic waste in water, mixing and stirring, and centrifuging to obtain a centrifuge rich in alkaline metal ions and fly ash residue;

[0007] (2) adding the dried recycled aggregate to the centrifuge obtained in step (1), soaking and separating the recycled aggregate and the centrifuge;

[0008] (3) subjecting the recycled aggregate obtained in step (2) to a CO2 carbonization treatment to obtain a reinforced recycled aggregate;

[0009] (4) Repeat steps (2) to (3) for multiple times with the reinforced recycled aggregate to complete the reinforcement process of the recycled aggregate.

[0010] Further, in step (1), the municipal solid waste incineration fly ash refers to the residue collected by the flue gas purification system of a municipal solid waste incineration power plant, and the particle size of the municipal solid waste incineration fly ash is below 0.150 mm.

[0011] Further, in step (1), the mass ratio of the municipal solid waste incineration fly ash to water is 1:(3 - 5), and the mixing time is 0.5 - 1 h.

[0012] Further, in step (2), the liquid level height of the centrifuged liquid exceeds the highest point of the recycled aggregate by 2 - 3 cm.

[0013] Further, in step (2), the soaking treatment time is 12 - 24 h.

[0014] Further, in step (2), the recycled aggregate is prepared by crushing and screening construction demolition waste, and is one or more of recycled concrete aggregate, recycled brick - concrete aggregate, and recycled brick aggregate.

[0015] Further, in step (2), the particle size of the recycled aggregate is 0.075 - 31.5 mm.

[0016] Further, in step (3), the CO2 carbonization treatment is natural carbonization under normal temperature and pressure with the air CO2 concentration or accelerated carbonization under high temperature, high pressure and high CO2 concentration.

[0017] Further, in step (3), the natural carbonization time is 24 - 48 h, and the accelerated carbonization time is 12 - 24 h.

[0018] Further, in step (4), the number of times is 3 - 5 times.

[0019] The technical principle of the present invention is:

[0020] Since the recycled aggregate has a loose structure, a high porosity and few carbonizable components inside (there are almost no carbonizable components in the recycled brick aggregate), the pores and micro - cracks that can be filled by the carbonization products generated by CO2 carbonization are very limited. Therefore, directly using CO2 carbonization on the recycled aggregate has an insignificant effect on improving its technical performance. The water - washed centrifuged liquid of the municipal solid waste incineration fly ash contains a large amount of metal cations (Ca 2+ 、Mg 2+ 、Cu 2+ 、Cd 3+ 、Zn 2+ 、Pb 2+ etc.), and its pH value is alkaline, which is CO3 2-It provides a good environment for the reaction with metal cations to form carbonate precipitates. Therefore, pre-impregnating recycled aggregates with the centrifugate and then carbonizing them is equivalent to adding a large amount of carbonizable components into the pores and microcracks of the aggregates. A large amount of carbonates (such as CaCO3, MgCO3, ZnCO3, Cu2(OH)2CO3, 2PbCO3·Pb(OH)2, etc.) will be generated and precipitated during the carbonization reaction, effectively reducing the porosity of the recycled aggregates and improving their technical properties. In addition, when the strengthened recycled aggregates are applied to concrete or mortar, the carbonate particles attached to the surface of the aggregates have the effect of stimulating the hydration of cement-based materials. They will become the nucleation sites of calcium silicate hydrate to promote the formation of calcium silicate hydrate, which is beneficial to improving the performance of the interfacial transition zone between the aggregates and the new mortar, and further improving the technical properties of recycled aggregate concrete or mortar.

[0021] The method for strengthening recycled aggregates based on the co-carbonization of municipal solid waste incineration fly ash of the present invention effectively solves the congenital defects of recycled aggregates such as low apparent density, high water absorption rate and crushing index due to the existence of more microcracks and pores, and then improves the problems of poor workability, low strength and poor durability of recycled aggregate concrete. It is beneficial to improve the resource utilization rate of construction waste, and at the same time reduces the heavy metal content of municipal solid waste incineration fly ash and realizes the permanent sequestration of CO2 during this process, promoting the safe disposal and resource utilization of municipal solid waste incineration fly ash.

[0022] Advantages: Compared with the prior art, the present invention has the following remarkable advantages:

[0023] (1) By washing the municipal solid waste incineration fly ash with water, the method of the present invention effectively reduces the heavy metal content in the fly ash. The washed fly ash filter residue can be further used for safe disposal and resource utilization, solving the problems of product quality damage or heavy metal pollution caused by too high heavy metal content in the fly ash.

[0024] (2) Under the action of the carbonization reaction, the method of the present invention generates carbonates from CO2 and metal cations in the centrifugate of the washed fly ash in an alkaline environment, effectively reducing the porosity of the recycled aggregates and significantly improving the technical properties of the recycled aggregates, manifested in the increase of apparent density, the decrease of water absorption rate and crushing index, and can effectively solve the problems of poor workability, low strength and poor durability of recycled aggregate concrete or mortar, which is beneficial to the popularization and application of recycled concrete or mortar in engineering construction.

[0025] (3) The method of the present invention uses carbon dioxide mineralization technology to convert CO2 into stable carbonates and fill them into the pores and microcracks of the aggregates, realizing the permanent sequestration of CO2 and effectively reducing the CO2 content in the industrial exhaust gas.

[0026] In summary, the technical solution proposed by the present invention not only improves the technical performance of recycled aggregates, but also solves the problem of excessive heavy metal content in fly ash from municipal solid waste incineration and achieves the permanent sequestration of CO2. It effectively promotes the harmless treatment and resource utilization of construction waste and fly ash from municipal solid waste incineration, realizes the treatment of waste with waste and the synergistic effect of three aspects, and has remarkable environmental and economic benefits. Description of the Drawings

[0027] Figure 1 It is a schematic flow chart of the co-carbonization of fly ash from municipal solid waste incineration and recycled aggregates. Specific Embodiments

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0029] The raw materials and their properties are as follows:

[0030] Recycled coarse aggregate - 1 (RCA - 1): It is derived from the concrete pavement layer of a road project in Nanjing, obtained by crushing and screening, with a particle size range of 4.75 - 19.0 mm, and it is called recycled concrete coarse aggregate.

[0031] Recycled coarse aggregate - 2 (RCA - 2): It is derived from a building demolition project in Nanjing, obtained by crushing and screening waste bricks, with a particle size range of 4.75 - 19.0 mm, and it is called recycled brick coarse aggregate.

[0032] Recycled fine aggregate 1 (RFA - 1): It is derived from the concrete pavement layer of a road project in Nanjing, obtained by crushing and screening, with a particle size range of 0.075 - 4.75 mm, and it is called recycled concrete fine aggregate.

[0033] Recycled fine aggregate 2 (RFA - 2): It is derived from a building demolition project in Nanjing, obtained by crushing and screening waste bricks, with a particle size range of 0.075 - 4.75 mm, and it is called recycled brick fine aggregate.

[0034] According to "Crushed and Broken Stones for Construction" (GB / T 14685 - 2022), the apparent density, water absorption rate, and crushing index parameters of RCA - 1 and RCA - 2 were tested, and the results are shown in Table 2 before strengthening.

[0035] According to "Sand for Construction" (GB / T 14684 - 2022), the apparent density, water absorption rate, and crushing index parameters of RFA - 1 and RFA - 2 were tested, and the results are shown in Table 2 before strengthening.

[0036] Municipal solid waste incineration fly ash: sourced from a municipal solid waste incineration plant in Nanjing, with a particle size range of less than 0.150 mm. The chemical composition of the municipal solid waste incineration fly ash was identified using an X-ray fluorescence spectrometer (XRF), and the results are shown in Table 1. Heavy metal toxicity tests were conducted on the waste incineration fly ash in accordance with the "Technical Specifications for Soil Environmental Monitoring" (HJ 166-2004) and the "Horizontal Oscillation Method for the Leaching Toxicity of Solid Wastes" (HJ 557-2009). The limit requirements in the "Technical Specifications for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial)" (HJ 1134-2022) were referred to for the heavy metal leaching toxicity.

[0037] Table 1 Chemical composition of municipal solid waste incineration fly ash (wt / %)

[0038]

[0039] Note: LOI represents loss on ignition

[0040] Water: Tap water in Nanjing area.

[0041] Example 1

[0042] S1: Dissolve 5 kg of municipal solid waste incineration fly ash in 15 kg of water. Use an industrial stirring tank to mix and stir the municipal solid waste incineration fly ash and water for 0.5 h. After stirring and dissolving, pour the mixture into an industrial centrifuge for centrifugation to obtain centrifugate-1 rich in alkaline metal ions and fly ash filter residue-1;

[0043] S2: Place 5 kg of dried RCA-1 in a container, pour the centrifugate-1 obtained in step S1 (the liquid level of the centrifugate-1 is about 2 cm higher than the highest point of RCA-1) to soak RCA-1 for 12 h. After soaking, separate RCA-1 from the centrifugate-1 and recover all the centrifugate;

[0044] S3: Spread the RCA-1 soaked in the centrifugate in step S2 on a shady and well-ventilated place, and collect the recycled aggregate for standby after natural carbonization for 24 h;

[0045] S4: Repeat steps S2 to S3 for 3 times with the recycled aggregate obtained in step S3 to complete all the strengthening processes of RCA-1. The whole process is as Figure 1 shown.

[0046] Performance test:

[0047] According to "Crushed Stones and Pebbles for Construction" (GB / T 14685-2022), the apparent density, water absorption and crushing index parameters of the strengthened RCA-1 were tested, and the results are shown in Table 2.

[0048] The heavy metal toxicity test of fly ash filter residue - 1 was carried out in accordance with the "Technical Specification for Soil Environmental Monitoring" (HJ 166 - 2004) and the "Horizontal Oscillation Method for the Leaching Toxicity of Solid Wastes" (HJ 557 - 2009). The limit requirements in the "Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial)" (HJ 1134 - 2022) were referred to for the leaching toxicity of heavy metals. The results are shown in Table 3.

[0049] Example 2

[0050] The experimental process was the same as that of Example 1, except that the repetition of steps S2 - S3 three times in step S4 was replaced by five times. Specific implementation steps:

[0051] S1 - S3: The same as steps S1 - S3 of Example 1;

[0052] S4: The recycled aggregate obtained in step S3 was repeated steps S2 - S3 five times to complete all the strengthening processes of RCA - 1.

[0053] The apparent density, water absorption rate and crushing index parameters of the strengthened RCA - 1 are shown in Table 2.

[0054] Example 3

[0055] The experimental process was the same as that of Example 1, except that the natural carbonation in step S3 was replaced by accelerated carbonation. Specific implementation steps:

[0056] S1 - S2: The same as steps S1 - S2 of Example 1;

[0057] S3: The RCA - 1 soaked in the centrifuged liquid in step S2 was placed in a concrete carbonation test chamber for accelerated carbonation treatment. The carbonation temperature was set at 20 ± 2 °C, the humidity was 70 ± 5%, the carbon dioxide concentration was 20.0 ± 0.5%, and the carbonation time was 12 h.

[0058] S4: The recycled aggregate obtained in step S3 was repeated steps S2 - S3 three times to complete all the strengthening processes of RCA - 1.

[0059] The apparent density, water absorption rate and crushing index parameters of the strengthened RCA - 1 are shown in Table 2.

[0060] Example 4

[0061] The experimental process was the same as that of Example 1, except that RCA - 1 was replaced by RCA - 2. Specific implementation steps:

[0062] S1: Dissolve 5 kg of municipal solid waste incineration fly ash in 25 kg of water. Use an industrial stirring tank to mix and stir the fly ash and water for 1 h. After stirring and dissolving, pour the mixed solution into an industrial centrifuge for centrifugation. After centrifugation, obtain centrifugate-2 rich in alkaline metal ions and fly ash filter residue-2;

[0063] S2: Place 5 kg of dried RCA-2 in a container, pour the centrifugate-2 obtained in step S1 (the liquid level height of the centrifugate-2 needs to be about 3 cm above the highest point of RCA-2) to soak RCA-2 for 24 h. After soaking, separate RCA-2 from the centrifugate-2 and recover all the centrifugate;

[0064] S3: Spread the RCA-2 soaked in the centrifugate in step S2 in a cool and ventilated place, and collect the recycled aggregate for standby after natural carbonization for 48 h;

[0065] S4: Repeat steps S2 to S3 for 5 times with the recycled aggregate obtained in step S3 to complete all the strengthening processes of RCA-2.

[0066] The results of the apparent density, water absorption rate, and crushing index parameters of the strengthened RCA-2 are shown in Table 2. The heavy metal toxicity results of the fly ash filter residue-2 are shown in Table 3.

[0067] Example 5

[0068] The experimental process is the same as that of Example 1, except that RCA-1 is replaced by RFA-1. Specific implementation steps:

[0069] S1: The same as step S1 of Example 1. S2: Place 5 kg of dried RFA-1 in a container, pour the centrifugate-1 obtained in step S1 (the liquid level height of the centrifugate-1 needs to be about 3 cm above the highest point of RFA-1) to soak RFA-1 for 24 h. After soaking, separate RFA-1 from the centrifugate-1 and recover all the centrifugate;

[0070] S3: Place the RFA-1 soaked in the centrifugate in step S2 in a concrete carbonation test chamber for accelerated carbonation treatment. Set the carbonation temperature to 20 ± 2 °C, humidity to 70 ± 5%, carbon dioxide concentration to 20.0 ± 0.5%, and carbonation time to 12 h.

[0071] S4: Repeat steps S2 to S3 for 3 times with the recycled aggregate obtained in step S3 to complete all the strengthening processes of RFA-1.

[0072] Test the apparent density, water absorption rate, and crushing index parameters of the strengthened RFA-1 according to "Sand for construction" (GB / T 14684-2022), and the results are shown in Table 2.

[0073] Example 6

[0074] The experimental process is the same as that of Example 2, except that RCA-2 is replaced by RFA-2. Specific implementation steps:

[0075] S1: The same as step S1 of Example 2.

[0076] S2: Place 5 kg of dried RFA-2 in a container, pour the centrifugate-2 obtained in step S1 (the liquid level of the centrifugate-2 needs to be about 3 cm higher than the highest point of RFA-2) to soak RFA-2 for 24 h. After soaking, separate RFA-2 from the centrifugate-2 and recover all the centrifugate;

[0077] S3: Place the RFA-2 soaked in the centrifugate in step S2 in a concrete carbonation test chamber for accelerated carbonation treatment. Set the carbonation temperature to 20 ± 2 °C, humidity to 70 ± 5%, carbon dioxide concentration to 20.0 ± 0.5%, and carbonation time to 24 h.

[0078] S4: Repeat steps S2 to S3 for 5 times with the recycled aggregate obtained in step S3 to complete all the strengthening processes of RFA-2.

[0079] The results of the apparent density, water absorption and crushing index parameters of the strengthened RFA-2 are shown in Table 2.

[0080] Example 7

[0081] The experimental process is the same as that of Example 1, except that step S4 is not implemented, and S1 to S3 are all the strengthening processes. Specific implementation steps:

[0082] S1 - S3: The same as steps S1 to S3 of Example 1;

[0083] The results of the apparent density, water absorption and crushing index parameters of the strengthened RCA-1 are shown in Table 2.

[0084] Example 8

[0085] The experimental process is the same as that of Example 1, except that the natural carbonation for 24 h in step S3 is replaced by natural carbonation for 12 h. Specific implementation steps:

[0086] S1 - S2: The same as steps S1 to S2 of Example 1;

[0087] S3: Spread the RCA-1 soaked in the centrifugate in step S2 in a cool and ventilated place, and collect the recycled aggregate for standby after natural carbonation for 12 h;

[0088] S4: Repeat steps S2 to S3 for 3 times with the recycled aggregate obtained in step S3 to complete all the strengthening processes of RCA-1.

[0089] The apparent density, water absorption rate, and crushing index parameters of RCA-1 after strengthening are shown in Table 2.

[0090] Table 2 Comparison of technical performance indicators of recycled aggregates before and after strengthening

[0091]

[0092]

[0093] As can be seen from Table 2, after strengthening by the present invention, the technical performance of the recycled aggregates in Examples 1-6 has been significantly improved. By comparing Example 1 and Example 2, it can be found that increasing the repetition times of steps S2-S3 can further improve the technical performance of the recycled aggregates. This is because more carbonation products are generated during multiple "soaking-carbonation" processes, resulting in an increase in the density of the aggregates. However, from the perspective of the strengthening effect, for recycled concrete aggregates with relatively low porosity, the improvement effect brought by increasing the repetition times of steps S2-S3 is limited. Therefore, for recycled aggregates with relatively high porosity, the repetition times of steps S2-S3 can be appropriately increased, and Examples 4 and 6 prove the above view.

[0094] By comparing Example 1 and Example 3, it can be found that when accelerated carbonation is used to replace natural carbonation, not only the time required for strengthening the aggregates is reduced, but also recycled aggregates with more excellent performance are obtained. This is mainly because the concrete carbonation test chamber provides a high-concentration carbon dioxide and a suitable temperature and humidity environment, and the reaction of alkaline metal ions and CO3 2- in the pores and microcracks of the aggregates is more rapid and sufficient, so the strengthening effect is more significant.

[0095] Examples 5 and 6 use recycled fine aggregates. It can be found that the present invention is also applicable to the strengthening of recycled fine aggregates, and its strengthening effect is better than that of recycled coarse aggregates. This is mainly because recycled fine aggregates have a larger porosity and specific surface area, which can absorb more alkali metal solutions and then generate more carbonation products.

[0096] By comparing Example 1, Example 2, and Example 7, it can be found that only one "soaking-carbonation" has a very limited effect on improving the performance of the aggregates. This is because the carbonation products generated by one "soaking-carbonation" cannot well fill the pores and microcracks of the aggregates. In addition, comparing Example 1 and Example 8 shows that it is very necessary to ensure an appropriate carbonation time. Too little carbonation time will lead to insufficient carbonation reaction and less generation of carbonation products.

[0097] Table 3 Heavy metal leaching toxicity of municipal solid waste incineration fly ash and filter residue

[0098]

[0099] As can be seen from Table 3, there is a phenomenon that the leaching concentrations of heavy metals Cd, Cu, Pb, and Zn in the raw municipal solid waste incineration fly ash exceed the standard, while the heavy metal leaching concentrations in the fly ash filter residue treated by the present invention all meet the standard limits. By comparing the total amounts and leaching concentrations of heavy metals in Filter Residue-1 and Filter Residue-2, it can be found that when the mass ratio of municipal solid waste incineration fly ash to water is adjusted from 1:3 to 1:5, the total amounts and leaching concentrations of heavy metals in the fly ash filter residue are further reduced. Therefore, when the total amount and leaching of heavy metals in the raw fly ash are relatively high, the mass of water can be appropriately increased.

[0100] The data results of the examples further verify the practicality of the present invention.

[0101] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any technical solutions obtained by adopting equivalent substitution or equivalent transformation are within the protection scope of the present invention.

Claims

1. A method for strengthening recycled aggregates based on the co-carbonization of municipal solid waste incineration fly ash, characterized in that, It includes the following steps: (1) Dissolve the municipal solid waste incineration fly ash in water, mix and stir, and centrifuge to obtain a centrifugate rich in alkaline metal ions and fly ash filter residue; (2) Add the dried recycled aggregate to the centrifugate obtained in step (1), soak and treat, and separate to obtain the recycled aggregate and the centrifugate; (3) Perform CO2 carbonization treatment on the recycled aggregate obtained in step (2) to obtain the strengthened recycled aggregate; (4) Repeat steps (2) to (3) for the strengthened recycled aggregate multiple times to complete the strengthening process of the recycled aggregate.

2. The method for strengthening recycled aggregates based on co-carbonization of municipal solid waste incineration fly ash according to claim 1, characterized in that In step (1), the particle size of the municipal solid waste incineration fly ash is below 0.150 mm.

3. The method for strengthening recycled aggregates based on the co-carbonization of municipal solid waste incineration fly ash according to claim 1, wherein In step (1), the mass ratio of the municipal solid waste incineration fly ash to water is 1:(3 - 5), and the mixing and stirring time is 0.5 - 1 h.

4. The method for strengthening recycled aggregate based on co-carbonization of municipal solid waste incineration fly ash according to claim 1, wherein In step (2), the liquid level height of the centrifugate exceeds the highest point of the recycled aggregate by 2 - 3 cm.

5. The method for strengthening recycled aggregate based on co-carbonization of municipal solid waste incineration fly ash according to claim 1, wherein In step (2), the soaking treatment time is 12 - 24 h.

6. The method for strengthening recycled aggregate based on the co-carbonization of municipal solid waste incineration fly ash according to claim 1, wherein In step (2), the recycled aggregate is one or several of recycled concrete aggregate, recycled brick - concrete aggregate, and recycled brick aggregate.

7. The method for strengthening recycled aggregates based on the co-carbonization of municipal solid waste incineration fly ash according to claim 1, wherein In step (2), the particle size of the recycled aggregate is 0.075 - 31.5 mm.

8. The method for strengthening recycled aggregate based on co-carbonization of municipal solid waste incineration fly ash according to claim 1, wherein In step (3), the CO2 carbonization treatment is natural carbonization under normal temperature and pressure with air CO2 concentration or accelerated carbonization under high temperature and high pressure with high CO2 concentration.

9. The method for strengthening recycled aggregates based on the co-carbonization of municipal solid waste incineration fly ash according to claim 8, characterized in that, In step (3), the natural carbonization time is 24 - 48 h, and the accelerated carbonization time is 12 - 24 h.

10. The method for strengthening recycled aggregates based on co-carbonization of municipal solid waste incineration fly ash according to claim 1, characterized in that In step (4), multiple times means 3 - 5 times.

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