Construction waste regenerated cement soil as well as preparation method and application thereof

Abstract

The invention discloses construction waste regenerated cement soil as well as a preparation method and application thereof, and relates to the technical field of regenerated cement soil. The construction waste regenerated cement soil comprises cement, modified regenerated powder and water, the modified regenerated powder is formed by mixing granulated blast furnace slag, diatomite, a retarding and water reducing agent and the like with regenerated powder and then modifying the mixture, the particle size of the modified regenerated powder is smaller than 0.15 mm, and the regenerated powder is obtained by crushing and screening construction waste for multiple times. By adopting the scheme, a synergistic effect can be generated, so that the gelling performance of the regenerated powder can be stabilized while the regenerated powder can be fully activated, and a specific particle size range is matched, so that the modified regenerated powder is favorable for accelerating a hydration reaction in a system and improving the synergistic effect of active components while improving the compaction degree of cement soil; the high-value utilization of the construction waste regenerated powder is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of recycled cement soil, in particular to a construction waste recycled cement soil and a preparation method and application thereof. BACKGROUND

[0002] Currently, there are related technologies that can use construction waste as recycled powder to prepare recycled cement soil, which is widely used in various backfilling and roadbed construction. After the construction waste is crushed and sieved to extract coarse aggregate and fine aggregate, a considerable proportion of recycled powder is generated. The particle size of these powders is generally less than 0.15 mm. Since the existing construction waste recycling technology mostly focuses on the recycling of coarse aggregate and fine aggregate, the utilization and research of recycled powder with a particle size less than 0.15 mm are less. Therefore, it is difficult to fully utilize the recycled powder generated each time.

[0003] Some studies have attempted to use these recycled powders as substitutes for cement. However, due to the unclear composition and amount of each raw material in construction waste, the activity of the residual recycled powder after crushing is not well understood. As a result, the properties of recycled powder are not stable. If it is directly mixed into cement and applied to backfilling or roadbed construction, the performance of hardened recycled cement material is also unstable. Therefore, the utilization rate of recycled powder generated from construction waste is generally low at this stage, and it has not been widely utilized. With the tightening of environmental protection policies and the promotion of a resource-saving society, how to effectively utilize construction waste, especially construction waste recycled powder, has become one of the problems that need to be solved in the industry. SUMMARY

[0004] In order to improve the utilization rate of construction waste recycled powder and improve the performance of recycled cement soil containing construction waste recycled powder, the present application provides a construction waste recycled cement soil, a preparation method and application thereof.

[0005] In a first aspect, the present application provides a construction waste recycled cement soil using the following technical solution: A construction waste recycled cement soil, comprising the following raw materials by weight: Cement: 5-15 parts; Modified recycled powder: 85-15 parts; Water: 20-25 parts; The modified recycled powder is modified by mixing granulated blast furnace slag, diatomite, and a retarding water-reducing agent with recycled powder, and the particle size of the modified recycled powder is less than 0.15 mm. The recycled powder is obtained by crushing and sieving construction waste multiple times.

[0006] By adopting the technical scheme, the granulated blast furnace slag, diatomite and retarder water reducing agent are used to modify the recycled powder prepared from the construction waste, the granulated blast furnace slag and diatomite can cooperatively improve the activity and cementation efficiency of the modified recycled powder, so that the recycled powder can be fully activated while the cementation performance is stabilized, the fine particle size design enables the modified recycled powder to effectively improve the pore structure of the recycled cement soil, improves the cement soil compactness, accelerates the hydration reaction in the system and improves the synergistic effect of the active components, in addition, the retarder water reducing agent can effectively reduce the water demand increase caused by the modified recycled powder with high specific surface area, which is beneficial to ensure the workability of the cement soil and improve the structural strength, and then the modified recycled powder after mixing modification can replace most of the cement in the cement soil and solve the problems of low strength and large shrinkage rate of the cement soil after mixing with the traditional recycled powder, so that the high-value utilization of the recycled powder of construction waste is realized.

[0007] Optionally, the preparation method of the modified recycled powder comprises the following steps: A1, the construction waste is subjected to multiple crushing, magnetic separation, screening, cleaning, homogenization and mixing processes to obtain recycled powder with a particle size of less than 2 mm; the primary recycled powder is fully mixed with granulated blast furnace slag and diatomite, and then placed at 800-900 DEG C for calcination for 1-3 h, and the primary mixed recycled powder is obtained after cooling; A2, the primary mixed recycled powder obtained in step A1 is weighed, alcohol amine grinding aid and calcium lignosulfonate are added, dry grinding is performed and screening is performed to obtain mixed recycled powder with a particle size of less than 0.15 mm; A3, the mixed recycled powder obtained in step A2 is weighed, a retarder water reducing agent is added, mixed and stirred uniformly to obtain a modified recycled powder.

[0008] By adopting the technical scheme, the preparation method of the modified recycled powder is simple, which can be realized by using the traditional recycled aggregate or recycled powder processing equipment without the need for equipment improvement or additional purchase of other equipment, which is beneficial to realize rapid production in the factory and reduce the preparation cost.

[0009] Optionally, the recycled powder is specifically a mixed powder of cement-based recycled powder prepared by crushing cement-based construction waste and masonry recycled powder prepared by crushing masonry construction waste, and the mixing mass ratio of the cement-based recycled powder to the masonry recycled powder is (5-7):(3-5).

[0010] By adopting the technical scheme, the cement-based recycled powder contains uncompletely hydrated cement plastic particles and a small amount of volcanic ash active components, and the masonry recycled powder has excellent mechanical strength although its cementing activity is low, can be used as a reinforcing filler to improve the pore structure of the cement soil, and forms a composite skeleton structure of "cement-cementing product-fine particle filler", which is beneficial to improving the activity and cementing stability of the recycled powder, improving the mechanical properties of the recycled cement soil, and realizing high-value utilization of the double-source construction waste.

[0011] Optionally, in the primary mixed recycled powder, the mixing mass ratio of the recycled powder, the granulated blast furnace slag and the diatomite is 10:(1-2):(0.1-0.5).

[0012] By adopting the technical scheme, in this ratio, the synergistic modification effect of the modified recycled powder can be ensured, the particle filling effect and active hydration of the granulated blast furnace slag can be fully played, efficient modification can be realized, and the shrinkage effect of excessive granulated blast furnace slag and diatomite on the cement soil can be inhibited, which is beneficial to reducing the shrinkage rate of the cement soil in the later period.

[0013] Optionally, in the mixed recycled powder, the addition amount of the alcohol amine grinding aid is 0.05%-0.1% of the addition amount of the primary mixed recycled powder, and the addition amount of the calcium lignosulfonate is 0.2%-0.25% of the addition amount of the primary mixed recycled powder.

[0014] By adopting the technical scheme, the grinding efficiency of the mixed recycled powder can be improved, the mixed recycled powder can be preliminarily activated by the calcium lignosulfonate, the activity and cementing effect of the modified recycled powder can be improved, and the high-value utilization of the construction waste recycled powder can be realized.

[0015] Optionally, the mixed recycled powder is sieved by a 0.075mm square hole sieve, and the passing rate is greater than 90%; and sieved by a 0.05mm square hole sieve, and the passing rate is less than 10%.

[0016] By adopting the technical scheme, when the average particle size of the mixed recycled powder is in the above range, the modified recycled powder prepared has good particle size distribution and hydration effect, the cost of preparing the modified recycled powder is not high, the raw material modification cost can be reduced, the comprehensive performance of the recycled cement soil is better, and the economic benefit is obvious.

[0017] Optionally, the addition amount of the retarder is 0.084%-0.125% of the addition amount of the mixed recycled powder.

[0018] Optionally, the retarder water-reducing agent is mixed by polycarboxylic acid water-reducing agent and retarder according to the mass ratio of (8-12):(0.4-0.5), and the retarder is at least one of sodium gluconate, borax and sodium hexametaphosphate.

[0019] By adopting the technical scheme, the water demand increase caused by the modified regenerated powder with high specific surface area can be effectively reduced, and the workability of the cement soil can be ensured and the structural strength thereof can be improved.

[0020] In a second aspect, the application provides a preparation method of the construction waste regenerated cement soil, which adopts the following technical scheme: The cement and the modified regenerated powder are mixed according to the mass fraction, then 60% of water is added, and the mixture is stirred and mixed for 1-2 min, the remaining water is added, and the stirring and mixing are continued for 1-2 min, and the mixture is activated for 30-60 min to obtain the construction waste regenerated cement soil.

[0021] By adopting the technical scheme, the cement, the modified regenerated powder and the water can be fully mixed, and the regenerated cement soil with good fluidity can be obtained, and the preparation method is simple, and the mixing can be carried out in the mixing station or at the construction site, so that the construction efficiency can be improved.

[0022] In a third aspect, the application provides an application of the construction waste regenerated cement soil, which adopts the following technical scheme: The application of the construction waste regenerated cement soil is suitable for laying the structural stable layer of the foundation pit backfill, the pipeline trench backfill or the roadbed filling engineering.

[0023] In summary, the technical scheme of the application has at least one of the following beneficial effects: 1. The modified regenerated powder prepared from the construction waste by using granulated blast furnace slag, diatomite and retarder water-reducing agent can be fully activated while the cementing property thereof is stabilized, and the cement soil compactness can be improved, the hydration reaction in the system can be accelerated, and the synergistic effect of the active components can be improved, so that the high-value utilization of the construction waste regenerated powder is realized.

[0024] 2. The water demand increase caused by the modified regenerated powder with fine particle size and high specific surface area can be effectively reduced by adding the retarder water-reducing agent, so that the workability of the cement soil can be ensured and the structural strength thereof can be improved.

[0025] 3. The cement-based regenerated powder and the masonry-based regenerated powder are mixed to prepare the regenerated powder, which is not only beneficial to improve the activity and cementing stability of the regenerated powder, but also beneficial to improve the mechanical properties of the regenerated cement soil, and the high-value utilization of the double-source construction waste can be realized. DETAILED DESCRIPTION

[0026] The application is further described in detail below in combination with the preparation examples, examples and comparative examples.

[0027] The cement is specifically selected as Portland cement of P.42.5 grade.

[0028] The polycarboxylic acid water reducing agent is selected from Jiangsu Aolite, and the brand is P180 powder polycarboxylic acid water reducing agent.

[0029] Preparation example [Preparation example 1] A modified recycled powder is specifically prepared by the following preparation method: A1, the construction waste is subjected to multiple crushing, magnetic separation, screening, cleaning, homogenization, mixing and other processes to obtain a recycled powder with a particle size of less than 2 mm; 100 kg of the recycled powder is mixed with 15 kg of granulated blast furnace slag and 2 kg of diatomite, and then placed at 800°C for calcination for 3 h, and after cooling, a primary mixed recycled powder is obtained; A2, 100 kg of the primary mixed recycled powder obtained in step A1 is weighed, 0.1 kg of triisopropanolamine and 0.2 kg of calcium lignosulfonate are added, dry grinding and screening are performed, and a mixed recycled powder with a particle size of less than 0.15 mm is obtained, and the screening is performed by using a 0.075 mm square hole screen, and the passing rate is less than 10%; A3, 100 kg of the mixed recycled powder obtained in step A2 is weighed, 0.085 kg of a retarding water reducing agent is added, mixed and stirred uniformly to obtain a modified recycled powder.

[0030] In the present preparation example, the recycled powder is specifically a cement-based recycled powder prepared by crushing cement-based construction waste; the retarding water reducing agent is specifically a mixture of 0.08 kg of polycarboxylic acid water reducing agent and 0.005 kg of sodium gluconate.

[0031] [Preparation example 2] A modified recycled powder is specifically prepared by the following preparation method: A1, the construction waste is subjected to multiple crushing, magnetic separation, screening, cleaning, homogenization, mixing and other processes to obtain a recycled powder with a particle size of less than 2 mm; 100 kg of the recycled powder is mixed with 15 kg of granulated blast furnace slag and 1 kg of diatomite, and then placed at 900°C for calcination for 1.5 h, and after cooling, a primary mixed recycled powder is obtained; A2, 100 kg of the primary mixed recycled powder obtained in step A1 is weighed, 0.05 kg of triisopropanolamine and 0.25 kg of calcium lignosulfonate are added, dry grinding and screening are performed, and a mixed recycled powder with a particle size of less than 0.15 mm is obtained, and the screening is performed by using a 0.075 mm square hole screen, and the passing rate is less than 10%; A3, 100 kg of the mixed recycled powder obtained in step A2 is weighed, 0.125 kg of the retarding water reducing agent is added, and the mixture is thoroughly mixed and stirred to obtain the modified recycled powder.

[0032] In the present preparation example, the recycled powder is specifically masonry recycled powder prepared by crushing masonry construction waste; the retarding water reducing agent is specifically a mixture of 0.12 kg of polycarboxylic acid water reducing agent and 0.005 kg of boric acid.

[0033]

Preparation Example 3

[0034] In the present preparation example, the recycled powder is specifically cement-based recycled powder prepared by crushing cement-based construction waste; the retarding water reducing agent is specifically a mixture of 0.1 kg of polycarboxylic acid water reducing agent and 0.004 kg of sodium gluconate.

[0035]

Preparation Example 4

Preparation Example 3

[0036] In the present preparation example, the recycled powder is specifically a mixed powder of cement-based recycled powder prepared by crushing cement-based construction waste and masonry recycled powder prepared by crushing masonry construction waste, and the specific mixing mass ratio of the cement-based recycled powder to the masonry recycled powder is 7:3, i.e., 100 kg of the recycled powder includes 70 kg of the cement-based recycled powder and 30 kg of the masonry recycled powder.

[0037]

Preparation Example 5

Preparation Example 4

[0038] In the present preparation example, the mixed mass ratio of the cement-based recycled powder to the masonry recycled powder in the recycled powder is 1:1, i.e., 100 kg of the recycled powder includes 50 kg of the cement-based recycled powder and 50 kg of the masonry recycled powder.

[0039] [Preparation Example 6] A modified recycled powder, which is different from the [Preparation Example 4] in that the addition amount of each component of the primary mixed recycled powder is different.

[0040] In the present preparation example, 100 kg of the recycled powder is mixed with 10 kg of granulated blast furnace slag and 5 kg of diatomite, and then is placed to be calcined at 850°C for 2 h, and the primary mixed recycled powder is obtained after cooling.

[0041] [Preparation Example 7] A modified recycled powder, which is different from the [Preparation Example 4] in that the addition amount of each component of the primary mixed recycled powder is different.

[0042] In the present preparation example, 100 kg of the recycled powder is mixed with 30 kg of granulated blast furnace slag and 5 kg of diatomite, and then is placed to be calcined at 850°C for 2 h, and the primary mixed recycled powder is obtained after cooling.

[0043] [Preparation Example 8] A modified recycled powder, which is different from the [Preparation Example 4] in that the average particle diameter of the modified recycled powder is different.

[0044] In the present preparation example, the mixed recycled powder is dry ground and sieved to obtain a mixed recycled powder having a particle diameter of less than 0.15 mm, and is sieved using a 0.075 mm square mesh sieve, a passing rate of which is greater than 90%, and is sieved using a 0.05 mm square mesh sieve, a passing rate of which is less than 10%.

[0045] [Preparation Example 9] A modified recycled powder, which is different from the [Preparation Example 4] in that the average particle diameter of the modified recycled powder is different.

[0046] In the present preparation example, the mixed recycled powder is dry ground and sieved to obtain a mixed recycled powder having a particle diameter of less than 0.15 mm, and is sieved using a 0.075 mm square mesh sieve, a passing rate of which is greater than 95%, and is sieved using a 0.05 mm square mesh sieve, a passing rate of which is greater than 60%.

[0047] [Preparation Example 10] A modified recycled powder, which is different from the [Preparation Example 1] in that the components of the primary mixed recycled powder are different.

[0048] In Step A1 of the present preparation example, the granulated blast furnace slag and the diatomite are replaced with an equivalent amount of recycled powder. The recycled powder is specifically a cement-based recycled powder prepared by crushing cement-based construction waste.

[0049]

Preparation Example 11

Preparation Example 10

[0050] In the present preparation example, the recycled powder is specifically a masonry recycled powder prepared by crushing masonry construction waste. Embodiment

[0051]

Embodiment 1

[0052] In the present embodiment, the modified recycled powder is specifically a modified recycled powder prepared by

Preparation Example 1

[0053] A preparation method of a construction waste recycled cement soil, which comprises the following steps: First, mix the cement and the modified recycled powder thoroughly, then add 60% of the water, mix and stir for 2 min, add the remaining water, and continue to mix and stir for 1 min, and then let it stand for 60 min to obtain a construction waste recycled cement soil.

[0054] An application of a construction waste recycled cement soil, which can be applied to the laying of structural stability layers in foundation pit backfill, pipeline trench backfill, or roadbed filling engineering.

[0055]

Embodiment 2

[0056] In the present embodiment, the modified recycled powder is specifically a modified recycled powder prepared by

Preparation Example 2

[0057] A preparation method of a construction waste recycled cement soil, which comprises the following steps: First, mix the cement and the modified recycled powder thoroughly, then add 60% of the water, mix and stir for 2 min, add the remaining water, and continue to mix and stir for 1 min, and then let it stand for 60 min to obtain a construction waste recycled cement soil.

[0058] An application of a construction waste recycled cement soil, which can be applied to the laying of structural stability layers in foundation pit backfill, pipeline trench backfill, or roadbed filling engineering.

[0059]

Embodiment 3

Embodiment 1

[0060] In this embodiment, a construction waste recycled cement soil comprises 9 kg of cement, 91 kg of modified recycled powder and 25 kg of water.

[0061]

Embodiment 4

Embodiment 3

[0062] In this embodiment, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 3

[0063]

Embodiment 5

Embodiment 3

[0064] In this embodiment, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 4

[0065]

Embodiment 6

Embodiment 3

[0066] In this embodiment, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 5

[0067]

Embodiment 7

Embodiment 3

[0068] In this embodiment, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 6

[0069]

Embodiment 8

Embodiment 3

[0070] In this embodiment, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 7

[0071]

Embodiment 9

Embodiment 3

[0072] In this embodiment, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 8

[0073]

Embodiment 10

Example 3

[0074] In the present example, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 9

[0075] Comparative Example

Comparative Example 1

Example 1

[0076] In the present comparative example, the modified recycled powder is replaced by an equivalent amount of cement-based recycled powder prepared by crushing cement-based construction waste. The particle size of the cement-based recycled powder is less than 0.1 mm, and the sieve residue is less than 30% when sieved by a 0.075 mm square hole sieve.

[0077]

Comparative Example 2

Example 1

[0078] In the present comparative example, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 10

[0079]

Comparative Example 3

Example 1

[0080] In the present comparative example, the modified recycled powder is specifically selected from a modified recycled powder prepared in

Preparation Example 11

[0081]

Comparative Example 4

Example 1

[0082] In the present comparative example, the modified recycled powder is replaced by an equivalent amount of mixed recycled powder prepared in

Preparation Example 1

[0083] Performance test data 1. Cement soil compaction degree: test according to 《JTG / T F20-2015 Highway Pavement Base Construction Technical Rules》 and the test method of conventional roadbed compaction degree, and record the compaction degree (%) of the cement soil prepared in each example and comparative example.

[0084] 2. Compressive strength: The 7-day unconfined compressive strength (MPa) of the cement-soil samples prepared in each example and the comparative example was recorded by referring to the "JTG E51-2009 Specifications for Testing of Inorganic Cementitious Stabilized Materials for Highway Engineering" and "T0805-1994 Test Method for Unconfined Compressive Strength of Inorganic Cementitious Stabilized Materials".

[0085] 3. Shrinkage: The 90-day dry shrinkage coefficient (10 of the cement-soil samples prepared in each example and the comparative example was recorded by referring to the "JTG E51-2009 Specifications for Testing of Inorganic Cementitious Stabilized Materials for Highway Engineering" and "T0854-2009 Test Method for Dry Shrinkage of Inorganic Cementitious Stabilized Materials". -6 ). Degree of compaction (%) Unconfined compressive strength (MPa) coefficient of dry shrinkage (10 -6 )]]> Example 1 97.5 3.9 70.5 Example 2 97.4 4.1 71.7 Example 3 97.7 3.6 66.2 Example 4 98 4.2 72.2 Example 5 98.3 4.3 75.6 Example 6 98.4 4.3 79.3 Example 7 97.8 4.1 94.6 Example 8 98.6 4.4 74.1 Example 9 98.8 4.5 83.6 Example 10 99.0 4.2 104.2 Comparative Example 1 92.6 2.7 205.7 Comparative Example 2 95.1 3.4 126.7 Comparative Example 3 95.8 3.1 158.3 Comparative Example 4 94.5 2.9 186.4

[0086] As can be seen from the data in Table 1 in combination with Example 1 and Comparative Example 1, the modified recycled powder prepared by mixing granulated blast furnace slag and diatomite in a specific ratio with recycled powder crushed from construction waste, and then mixing and modifying with an appropriate amount of a retarding water-reducing agent, can replace most of the cement to prepare recycled cement-soil. Compared with the traditional method of directly adding recycled powder, the compaction degree and 7-day unconfined compressive strength of the recycled cement-soil are significantly improved, and the 90-day dry shrinkage coefficient is significantly reduced. This may be because the granulated blast furnace slag can provide certain calcium-aluminum active ingredients for the recycled powder, and the diatomite can provide a porous adsorption structure through its porous properties, which is beneficial to synergistically improve the activity and cementing efficiency of the modified recycled powder, so that the recycled powder can be fully activated while stabilizing its cementing performance. In addition, the modified recycled powder with fine particle size can effectively fill the pores of the cement-soil and improve the pore structure, accelerate the hydration reaction in the system and improve the synergistic effect of active components while improving the compaction degree of the cement-soil. In addition, the retarding water-reducing agent can also effectively reduce the increase in water demand caused by the modified recycled powder with high specific surface area, which is beneficial to ensure the workability of the cement-soil and improve its structural strength. Therefore, the modified recycled powder after mixing and modification can replace most of the cement in the cement-soil and solve the problems of low strength and large shrinkage of the cement-soil after adding the traditional recycled powder, and realize the high-value utilization of construction waste.

[0087] In addition, in combination with Example 1 and Comparative Examples 2-4 and in combination with the data in Table 1, it can be seen that the modified recycled powder prepared by only mixing and modifying the recycled powder with the retarding water reducing agent, or the mixed recycled powder prepared by only mixing the granulated blast furnace slag, diatomite and recycled powder, has a better performance than the traditional recycled cement soil directly mixed with the recycled powder, but the performance improvement effect is still not as good as the modified recycled powder prepared by the synergistic modification of the recycled powder with the granulated blast furnace slag, diatomite and retarding water reducing agent. Therefore, the modification of the recycled powder with the granulated blast furnace slag, diatomite and retarding water reducing agent can produce a certain complementary or additive effect, which is beneficial to improving the microstructure and macroscopic performance of the recycled cement soil through different mechanisms, and to preparing the recycled cement soil with excellent performance.

[0088] In combination with Example 1 and Example 3 and in combination with the data in Table 1, it can be seen that when the cement content in the recycled cement soil is 9 parts and the modified recycled powder content is 91 parts, the compaction degree and 7-day unconfined compressive strength of the recycled cement soil are higher, and the 90-day dry shrinkage coefficient is lower under the same water content, compared to the cement content of 15 parts and the modified recycled powder content of 85 parts. This is beneficial to achieve the optimal strength and cost-benefit ratio of the cement soil.

[0089] In combination with Examples 4-6 and in combination with the data in Table 1, it can be seen that when the recycled powder is mixed with the cement-based recycled powder and the masonry recycled powder according to a certain proportion, the modified recycled powder prepared thereby can more effectively improve the compaction degree and 7-day unconfined compressive strength of the recycled cement soil, compared to using a single cement-based recycled powder as the recycled powder, but will cause the dry shrinkage coefficient of the recycled cement soil to increase slightly. However, with the further increase of the content of the masonry recycled powder in the recycled powder, the compaction degree and 7-day unconfined compressive strength of the recycled cement soil are less improved or not improved, and the dry shrinkage coefficient is significantly improved.

[0090] From the data in Table 1, it can be seen that, as the content of the granulated blast furnace slag in the modified recycled powder increases, the compaction degree and 7-day unconfined compressive strength of the recycled cement-soil are both significantly improved, and the drying shrinkage coefficient is significantly reduced, but the reduction amplitude gradually decreases. This is probably because the particle size distribution of the granulated blast furnace slag is closer to the dense packing state, which is conducive to improving the pore structure of the cement-soil, and at the same time, as a potential active admixture, the granulated blast furnace slag can also cooperate with the cement-soil system to generate cementitious products, thereby enhancing the structural strength of the hardened cement-soil. Therefore, as the content of the granulated blast furnace slag increases, the particle packing effect and active hydration reaction of the granulated blast furnace slag are more significant, and the compaction degree and unconfined compressive strength are improved, and the drying shrinkage coefficient is reduced. However, when the content of the granulated blast furnace slag exceeds a certain proportion, the optimization effect of the granulated blast furnace slag on the particle size distribution tends to be saturated, and the influence of the overall pore structure on the drying shrinkage of the cement-soil is weakened, so that even if the content of the granulated blast furnace slag continues to increase, the improvement effect on the drying shrinkage of the cement-soil is difficult to further improve.

[0091] From the data in Table 1, it can be seen that, as the average particle size of the mixed recycled powder in the modified recycled powder gradually decreases, the compaction degree of the recycled cement-soil shows a rising trend, and the rising amplitude gradually tends to be flat, the 7-day unconfined compressive strength shows a rising trend first and then a falling trend, and the 90-day drying shrinkage coefficient shows a rising trend, and the rising amplitude gradually increases. This is probably because, as the average particle size of the modified recycled powder gradually decreases, the fine-particle modified recycled powder can fully fill the pores and improve the pore structure of the cement-soil, which is conducive to accelerating the hydration reaction and the synergistic effect of the active components, and can improve the unconfined compressive strength of the cement-soil, but when the particle size of the modified recycled powder is too small, the specific surface area of the modified recycled powder increases, and the water demand is higher, which leads to a decrease in the "effective water-binder ratio", not only causing the lubrication between particles to weaken and the compaction difficulty to increase, and the later shrinkage deformation to be more significant, but also causing the harmful micropores to increase and the pore structure to deteriorate, which not only hinders the later strength development, but also causes the sensitivity of the drying shrinkage coefficient to the particle size change to increase.

[0092] In addition, since the cost required for further reducing the particle size of the mixed recycled powder in the modified recycled powder will be higher and higher, when the mixed recycled powder in the modified recycled powder is sieved by a 0.075 mm square hole sieve with a passing rate of more than 90%, and a 0.05 mm square hole sieve with a passing rate of less than 10%, a recycled cement-soil with lower preparation cost and better comprehensive performance can be obtained.

[0093] The specific embodiment is only an explanation of the present application, and is not a limitation of the present application. Those skilled in the art can make modifications to the specific embodiment without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A construction waste recycled cement soil, characterized in that: It includes the following raw materials in parts by weight: Cement: 5-15 parts; Modified recycled powder: 85-15 parts; Water: 20-25 parts; The modified recycled powder is modified by mixing granulated blast furnace slag, diatomaceous earth, retarding water reducer and the like with recycled powder, and the particle size of the modified recycled powder is less than 0.15 mm. The recycled powder is obtained by multiple crushing and screening of construction waste.

2. The construction waste recycled cement soil according to claim 1, characterized in that: The preparation method of the modified regenerated powder comprises the following steps: A1. The construction waste is subjected to multiple processes such as crushing, magnetic separation, screening, washing, homogenization, and mixing to obtain a recycled powder with a particle size of less than 2 mm; the primary recycled powder is fully mixed with granulated blast furnace slag and diatomaceous earth, and then calcined at 800-900° C. for 1-3 hours. After cooling, the primary mixed recycled powder is obtained; A2. Weigh the primary mixed regenerated powder obtained in step A1, add an alcoholamine grinding aid and calcium lignin sulfonate, dry-grind and sieve to obtain a mixed regenerated powder with a particle size of less than 0.15 mm; A3. Weigh the mixed regenerated powder obtained in step A2, add a retarding water-reducing agent, mix thoroughly and stir evenly to obtain modified regenerated powder.

3. The construction waste recycled cement soil according to claim 2, characterized in that: The recycled powder is specifically a mixed powder of cement-based recycled powder obtained by crushing cement-based construction waste and masonry recycled powder obtained by crushing masonry construction waste, and the mixing mass ratio of the cement-based recycled powder to the masonry recycled powder is (5-7):(3-5).

4. The construction waste recycled cement soil according to claim 2, characterized in that: In the primary mixed regenerated powder, the mixing mass ratio of the regenerated powder, the granulated blast furnace slag and the diatomaceous earth is 10:(1-2):(0.1-0.5).

5. The construction waste recycled cement soil according to claim 2, characterized in that: In the mixed regenerated powder, the added amount of the alcoholamine grinding aid is 0.05%-0.1% of the added amount of the primary mixed regenerated powder, and the added amount of the calcium lignin sulfonate is 0.2%-0.25% of the added amount of the primary mixed regenerated powder.

6. The construction waste recycled cement soil according to claim 2, characterized in that: The mixed regenerated powder is sieved using a 0.075 mm square hole sieve, with a pass rate greater than 90%; and is sieved using a 0.05 mm square hole sieve, with a pass rate less than 10%.

7. The construction waste recycled cement soil according to claim 2, characterized in that: The amount of the retarding water reducer added is 0.084%-0.125% of the amount of the mixed recycled powder added.

8. The construction waste recycled cement soil according to claim 7, characterized in that: The retarding water reducer is prepared by mixing a polycarboxylate water reducer and a retarder in a mass ratio of (8-12):(0.4-0.5), and the retarder is at least one of sodium gluconate, borax, and sodium hexametaphosphate.

9. A method for preparing construction waste recycled cement soil, for preparing the construction waste recycled cement soil according to any one of claims 1 to 8, characterized in that: The following steps are involved: By weight, cement and modified recycled powder are first fully mixed, and then 60% water is added, stirred and mixed for 1-2 minutes, and the remaining water is added and stirred and mixed for 1-2 minutes, and static activation is performed for 30-60 minutes to obtain a construction waste recycled cement soil.

10. An application of construction waste recycled cement soil, applicable to the construction waste recycled cement soil according to any one of claims 1 to 8, characterized in that: It is used for laying structural stabilization layers in foundation pit backfill, pipeline trench backfill or roadbed filling projects.