Preparation method of regenerated waste concrete slurry and controllable low-strength material

Abstract

The invention provides a preparation method of regenerated waste concrete slurry and a controllable low-strength material. The preparation method of the regenerated waste concrete slurry comprises the following steps: regulating and controlling the water content of waste concrete slurry, and carbonizing after the target water content is reached, so as to obtain the regenerated waste concrete slurry. According to the preparation method provided by the invention, the activity of the waste concrete slurry is improved by adopting a carbonization method, the water content of the slurry is controlled to be 80-300%, the operation is simple, and the cost is low. The prepared regenerated waste concrete slurry is applied to a controllable low-strength material and is compounded with regenerated sand powder and a small amount of additives for use, and the working performance of the controllable low-strength material can be met without adding water, cement and other cementing materials. In addition, the controllable low-strength material in the scheme can be effectively recycled, and carbon emission is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of construction engineering waste recycling, and in particular to a preparation method of recycled waste concrete slurry and a controllable low-strength material. Background Art

[0002] Controlled Low-strength Material (CLSM) is a general term for a series of low-strength materials with different uses. It is also often called: flow fill, non-shrinkage fill, controlled density fill, flow mortar, plastic cement soil, cement soil slurry, etc. Its raw materials come from a wide range of sources (industrial waste, construction solid waste, abandoned soil, etc.), the preparation process is simple, easy to construct, and the cost of re-excavation is low. It is widely used in engineering backfill, pavement base, pipeline cushion and other places.

[0003] The materials used in traditional controlled low-strength materials are mainly composed of cementitious materials, fine aggregates, water and admixtures. The cementitious materials mainly include silicate cement, fly ash, lime, etc.; fine aggregates generally use concrete sand; admixtures generally include air entraining agents, water reducers, accelerators, etc. Compared with ordinary concrete materials, controlled low-strength materials have lower strength requirements, but higher working performance requirements. In general, controlled low-strength materials have relatively low technical quality requirements for raw materials. Some construction and industrial solid wastes, such as copper mine tailings, carbide slag, coal gangue, red bricks, construction waste and waste rubber tires, have replaced part of the cementitious materials or fine aggregates for use in controlled low-strength materials. However, the use of the above recycled materials still cannot completely replace the use of cement, and due to the special properties of these materials, it will also lead to an increase in the type or amount of admixtures. For example, although red brick powder has high activity and can replace a large amount of cement, its large water demand leads to an increase in the amount of water reducer.

[0004] Waste concrete slurry is the concrete attached to the mixer, mixer truck or on the bottom of the drum. After washing the machine and mixer truck, the waste slurry with high water content and low activity is obtained. It is a kind of construction waste. In the conventional disposal method, due to the high water content in the waste concrete slurry, it needs to be dehydrated by a filter press and its water content is controlled to 20% to 30% before it can be landfilled. This leads to a significant increase in the comprehensive treatment cost, which is not conducive to large-scale industrial disposal. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the shortcomings of the prior art, the present invention provides a method for preparing recycled waste concrete slurry and a controllable low-strength material, which activates and regenerates the waste concrete slurry and utilizes the high water content of the waste concrete slurry itself to completely replace cement and water, thereby preparing a controllable low-strength material that meets the requirements of working performance and mechanical properties, thereby solving the problems raised in the above-mentioned background technology.

[0007] (II) Technical solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0009] According to a first aspect of the present invention, a method for preparing recycled waste concrete slurry is provided, comprising the following steps: regulating the moisture content of the waste concrete slurry, and performing carbonization treatment after reaching a target moisture content to obtain recycled waste concrete slurry.

[0010] Preferably, the formula for regulating the moisture content of the waste concrete slurry is as shown in Formula I:

[0011]

[0012] In formula I, x is the water content of the waste concrete paste, m is the mass of the waste concrete paste whose water content needs to be measured, V is the volume of the waste concrete paste, a is 500% water content, b is 80% water content, ρ a is the bulk density of the waste concrete paste with a moisture content of 500%, ρ b It is the bulk density of the waste concrete paste with a moisture content of 80%.

[0013] Preferably, the a The range is 1000~1200kg / m 3 , ρ b The range is 1500~1800kg / m 3 .

[0014] Preferably, the CO2 emission rate of the carbonization treatment is 30 to 50 L / min, and the time of the carbonization treatment is 0.5 to 4 h.

[0015] Preferably, the waste concrete slurry is selected from freshly mixed concrete on a concrete mixer or at the bottom of a drum, and is obtained after machine washing and aggregate screening.

[0016] According to a second aspect of the present invention, there is provided a controllable low-strength material based on waste concrete paste, comprising the following components in parts by weight: 1200 to 1410 parts of recycled waste concrete paste, 2500 to 3400 parts of recycled sand powder and 12 to 90 parts of an admixture;

[0017] Wherein, the recycled waste concrete slurry is selected from the recycled waste concrete slurry obtained according to the above preparation method.

[0018] Preferably, the regenerated sand powder is selected from fine aggregate obtained by crushing and screening construction waste or decoration waste.

[0019] Preferably, the particle size of the regenerated sand powder is 0.075-4.75 mm, and the water absorption rate is 5-15%.

[0020] Preferably, the admixture is selected from at least one of polycarboxylate water reducer, naphthalene water reducer, hydroxymethyl propyl cellulose ether, collapse retaining agent or air entraining agent.

[0021] Preferably, the slump of the controllable low-strength material is greater than 215 mm, the expansion is greater than 400 mm, and the 28-day unconfined compressive strength is greater than 1.35 MPa.

[0022] (III) Beneficial effects

[0023] The present invention provides a method for preparing recycled waste concrete slurry, which can control low-strength materials and has the following beneficial effects:

[0024] (1) The present invention provides a method for preparing recycled waste concrete slurry, which uses a carbonization method to improve the activity of the waste concrete slurry and control the water content of the slurry between 80% and 300%. The operation is simple and the cost is low.

[0025] (2) This solution provides a controllable low-strength material based on waste concrete slurry. Carbonized high-activity recycled waste concrete slurry is mixed with recycled sand powder and water reducer to obtain a fully solid waste controllable low-strength material. No external water and cementitious materials such as cement are required to meet the working performance of the controllable low-strength material. In addition, the controllable low-strength material of this solution can effectively reuse resources and reduce carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a performance regulating tank for regenerating waste concrete slurry of the present invention;

[0027] Among them, 1. Waste slurry collection pipeline; 2. Drain pipe; 3. Weight sensor; 4. pH value meter; 5. Hydraulic lifting rod; 6. CO2 delivery pump; 7. CO2 delivery head; 8. Computer control system; 9. Stirring device; 10. Carbonization tank. DETAILED DESCRIPTION

[0028] In order to better illustrate the content of the present invention, a detailed description is given below in conjunction with specific embodiments.

[0029] A method for preparing recycled waste concrete slurry, using Figure 1 The performance adjustment tank shown regenerates the waste concrete paste, wherein the main components of the waste concrete paste are cement particles, hydration products, water and a small amount of fine aggregate;

[0030] The performance adjustment tank includes a waste slurry collection pipeline 1 for collecting the waste concrete slurry generated from the production process and conveying it to the carbonation tank;

[0031] Drain pipe 2, a pipe system for controlling the moisture content of waste concrete paste, is intended to control the moisture content in the waste concrete paste through the value displayed on the weight sensor, and use the drainage valve to discharge excess moisture;

[0032] The weight sensor 3 is installed at the bottom of the carbonization tank to measure the mass of the liquid in the carbonization tank, transmit the measured pressure data to the computer control system and convert it into mass. By monitoring the change in weight, the water content of the waste concrete slurry can be converted to achieve control of different water contents;

[0033] The pH value measuring instrument 4 is installed on the side wall of the carbonization tank, and transmits the pH value of the slurry in the carbonization tank to the computer control system in real time through the probe so as to realize automatic monitoring and adjustment, thereby ensuring the stability of the carbonization process and improving production efficiency;

[0034] Hydraulic lifting rod 5, the hydraulic lifting rod is used to control the height of the carbonization device, and at the same time, a built-in CO2 delivery system can realize the adjustment of CO2 delivery amount and delivery speed;

[0035] CO2 delivery pump 6, the CO2 delivery pump delivers CO2 gas to the carbonization device, and uses a pump to compress and pressurize the CO2 gas to achieve efficient gas delivery. The CO2 delivery pump is composed of mechanical structures such as pistons, diaphragms or screws to ensure stable flow of CO2 under high pressure;

[0036] A CO2 delivery head 7 is provided with air holes or nozzles, which can make CO2 evenly distributed or sprayed to ensure effective delivery. The flow rate and pressure of CO2 can be adjusted and controlled by controlling the valve to meet different delivery requirements. Through the synergistic effect of these components, the CO2 delivery pump can effectively deliver CO2 to the target location to meet the needs of the waste concrete slurry carbonization process;

[0037] Computer control system 8. The computer control system can accurately monitor the operating status of the carbonation tank by receiving the pH value change data transmitted by the pH meter and the pressure change data provided by the weight sensor in real time. The computer control system will automatically adjust the working frequency and gas flow of the CO2 delivery pump according to the set process parameters, thereby optimizing the injection efficiency of carbon dioxide; through intelligent algorithms, the computer control system can quickly respond to the pH and pressure changes of the liquid to ensure the stability and consistency of the carbonation process;

[0038] The stirring device 9 is a device including a blade, a driving device and other structures, which is installed at the bottom of the hydraulic lifting rod and can be adjusted up and down. The driving device provides a rotating power for the blade to stir, so as to ensure the uniform dispersion of the waste concrete slurry-CO2 system;

[0039] Carbonation tank 10, the stirring device is a device including blades, drive devices and other structures, installed at the bottom of the hydraulic lifting rod, and the position can be adjusted up and down. The drive device provides the blades with rotational power to stir, so as to ensure the uniform dispersion of the waste concrete slurry-CO2 system;

[0040] The waste slurry collection pipeline 1 and the drainage pipe 2 are both connected to the carbonization tank 10. The height of the drainage pipe 2 is higher than that of the waste slurry collection pipeline 1. A weight sensor 3 is provided at the bottom of the carbonization tank 10, and a pH value meter 4 is provided on the side wall of the carbonization tank 10. The weight sensor 3 and the pH value meter 4 both transmit data to the computer control system 8 through wires. A carbonization device with regularly arranged CO2 delivery heads 7 is provided directly above the carbonization tank 10. The height of the carbonization device can be adjusted by a hydraulic lifting rod 5. The CO2 delivery pump 6 transfers the CO2 in the CO2 storage tank to the CO2 delivery head 7 through a pipeline. A stirring device 9 is provided between adjacent CO2 delivery heads 7.

[0041] The preparation method of recycled waste concrete slurry specifically comprises the following steps:

[0042] (1) The waste concrete slurry is transported to the carbonization tank 10 through the waste slurry collection pipe 1 and left to stand for 2 to 3 hours, and then the drain pipe 2 is opened to discharge the upper layer of clean water, and the moisture content of the waste concrete slurry is controlled to the target moisture content according to formula I;

[0043] (2) Control the hydraulic lifting rod 5 to descend until the CO2 delivery head 7 is completely immersed in the waste concrete slurry, and at the same time, open the stirring device 9, introduce CO2, and adjust the delivery time and delivery time of CO2 through the valve to achieve the activity improvement of the waste concrete slurry;

[0044] (3) The carbonized waste concrete slurry is collected through the waste collection pipe 1 to obtain recycled waste concrete slurry.

[0045] The following describes a controllable low-strength material based on waste concrete slurry according to the present invention in conjunction with specific embodiments.

[0046] Example 1

[0047] A method for preparing a controllable low-strength material based on waste concrete slurry comprises the following steps:

[0048] Step 1: Collect the waste concrete slurry and place it in a performance control tank, setting the target moisture content to 150%, ρ a and ρ b 1250kg / m 3 and 1700kg / m 3 After calculation, the density of the waste concrete paste needs to be controlled to 1325kg / m 3 ;

[0049] Step 2: Control the volume of waste concrete slurry to 8m 3 , the mass in the control tank is calculated to be 10600kg, the waste concrete slurry is placed in the control tank and left to stand for 3 days, then the drain pipe is opened to discharge the upper layer of clear water, and the control mass is 10600kg;

[0050] Step 3: Lower the hydraulic lifting rod to place the CO2 exhaust hole in the waste concrete slurry, turn on the CO2 delivery pump, control the CO2 emission rate to 30L / min, and the ventilation time to 2h;

[0051] Step 4: Open the waste slurry collection pipeline, discharge the recycled waste concrete slurry and place it in the mixer;

[0052] Step 5: Prepare all-solid waste controllable low-strength materials, which include the following components by weight: 1350 parts of high-activity waste concrete slurry, 3200 parts of recycled sand powder, 35 parts of polycarboxylic acid water reducer, and 15 parts of hydroxymethyl propyl cellulose ether; wherein the recycled sand powder is fine aggregate obtained by crushing and screening waste concrete, with a particle size between 0.15 mm and 4.75 mm and a water absorption rate of 8.5% to 12%.

[0053] Step 6: Mix and stir the materials for 10 minutes. After stirring, test the slump and expansion and put them into the mold. Then carry out standard curing at a temperature of 18-22°C and a humidity of 90-95%. After 7 days of age, carry out unconfined compressive strength test. The test results are shown in Table 1.

[0054] Example 2

[0055] A method for preparing a controllable low-strength material based on waste concrete slurry comprises the following steps:

[0056] Step 1: Collect the waste concrete slurry and place it in a performance control tank, setting the target moisture content to 100%, ρ a and ρ b 1100kg / m 3 and 1600kg / m 3 After calculation, the density of the waste concrete paste needs to be controlled to 2150kg / m 3 ;

[0057] Step 2: Control the volume of waste concrete slurry to 5m 3 , the mass in the control tank is calculated to be 10750kg, the waste concrete slurry is placed in the control tank and left to stand for 3 days, then the drain pipe is opened to discharge the upper layer of clear water, and the control mass is 10750kg;

[0058] Step 3: Lower the hydraulic lifting rod to place the CO2 exhaust hole in the waste concrete slurry, turn on the CO2 delivery pump, control the CO2 emission rate to 50L / min, and the ventilation time to 2h.

[0059] Step 4: Open the waste slurry collection pipeline, discharge the recycled waste concrete slurry and place it in the mixer;

[0060] Step 5: Prepare all-solid waste controllable low-strength materials, which include the following components in parts by weight: high-activity waste concrete slurry: 1,200 parts, regenerated sand powder: 2,800 parts, polycarboxylate water reducer: 20 parts, and hydroxymethyl propyl cellulose ether: 10 parts.

[0061] The recycled sand powder is a fine aggregate obtained by crushing and screening waste concrete, with a particle size ranging from 0.15mm to 4.75mm and a water absorption rate of 7% to 10%.

[0062] Step 6: Mix and stir the materials for 10 minutes. After stirring, test the slump and expansion, and put them into the mold. Then carry out standard curing. The standard curing temperature is 18-22℃, and the standard curing humidity is 90%-95%. After 7 days of age, carry out unconfined compressive strength test. The test results are shown in Table 1.

[0063] Comparative Example 1

[0064] A common solid waste-based controllable low-strength material, comprising the following components in parts by weight: 21 parts of cement, 42 parts of fly ash, 18 parts of waste concrete slurry powder, 331 parts of regenerated sand powder, 81 parts of water, and 2 parts of water reducer; wherein the cement is ordinary Portland cement with a strength grade of 52.5, the fly ash is Class F fly ash, the waste concrete slurry powder is a regenerated powder obtained by drying and grinding waste concrete slurry, and has an activity index of 60%, the regenerated sand powder is a fine aggregate obtained by crushing and screening waste concrete, with a particle size between 0.15 mm and 4.75 mm, and a water absorption rate of 7% to 10%, the water is tap water, and the water reducer is a polycarboxylic acid water reducer with a water reduction rate of 30%.

[0065] The preparation method of the above-mentioned common solid waste-based controllable low-strength material is as follows:

[0066] Step 1: Weigh all the materials and use a mixer to mix the dry materials for 5 minutes.

[0067] Step 2: Add the weighed water to the dry material and stir for 10 minutes.

[0068] Step 3: After mixing, test the slump and expansion, and put it into the mold at the same time. Then carry out standard curing. The standard curing temperature is 18-22℃, and the standard curing humidity is 90%-95%. After 7 days of age, carry out unconfined compressive strength test. The test results are shown in Table 1.

[0069] Table 1

[0070]

[0071] According to the comparison in Table 1, the present invention provides a controllable low-strength material based on carbonized waste concrete paste. After the waste concrete paste is regulated in water content and carbonized, a highly active recycled waste concrete paste is obtained, which can completely replace cement, and then prepare a controllable low-strength material that meets the requirements of working performance and mechanical properties. Compared with the prior art, the present invention does not use cement and other clinkers separately, and at the same time utilizes the high water content of the waste concrete paste, does not need to be filtered, is easy to operate, and reduces the processing cost and material price of the waste concrete paste. In addition, the prepared highly active waste concrete paste can promote the early hydration process of the controllable low-strength material, replace the use of admixtures such as accelerators, and has high environmental and social benefits.

[0072] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing recycled waste concrete slurry, characterized in that: The following steps are involved: The waste concrete slurry is subjected to moisture control, and after reaching the target moisture content, carbonization treatment is performed to obtain recycled waste concrete slurry.

2. The method for preparing recycled waste concrete slurry according to claim 1, characterized in that: The formula for regulating the moisture content of the waste concrete slurry is shown in Formula I: In formula I, x is the water content of the waste concrete paste, m is the mass of the waste concrete paste whose water content needs to be measured, V is the volume of the waste concrete paste, a is 500% water content, b is 80% water content, ρ a is the bulk density of the waste concrete paste with a moisture content of 500%, ρ b It is the bulk density of the waste concrete paste with a moisture content of 80%.

3. The method for preparing recycled waste concrete slurry according to claim 2, characterized in that: The a The range is 1000~1200kg / m 3 , ρ b The range is 1500~1800kg / m 3 .

4. The method for preparing recycled waste concrete slurry according to claim 1, characterized in that: The CO2 emission rate of the carbonization treatment is 30 to 50 L / min, and the time of the carbonization treatment is 0.5 to 4 hours.

5. The method for preparing recycled waste concrete slurry according to claim 1, characterized in that: The waste concrete slurry is selected from freshly mixed concrete in a concrete mixer, a mixer truck or at the bottom of a drum, and is obtained after machine washing and aggregate screening.

6. A controllable low-strength material based on waste concrete slurry, characterized in that: The invention comprises the following components in parts by weight: 1200 to 1410 parts of recycled waste concrete slurry, 2500 to 3400 parts of recycled sand powder and 12 to 90 parts of an admixture; Wherein, the recycled waste concrete slurry is selected from the recycled waste concrete slurry obtained by the preparation method according to any one of claims 1 to 5.

7. The controllable low-strength material based on waste concrete slurry according to claim 6, characterized in that: The regenerated sand powder is selected from fine aggregate obtained by crushing and screening construction waste or decoration waste.

8. The controllable low-strength material based on waste concrete slurry according to claim 7, characterized in that: The particle size of the regenerated sand powder is 0.075-4.75 mm, and the water absorption rate is 5-15%.

9. The controllable low-strength material based on waste concrete slurry according to claim 6, characterized in that: The additive is selected from at least one of polycarboxylate water reducer, naphthalene water reducer, hydroxymethyl propyl cellulose ether, collapse retaining agent or air entraining agent.

10. The controllable low-strength material based on waste concrete slurry according to claim 6, characterized in that: The controllable low-strength material has a slump greater than 215 mm, an expansion greater than 400 mm, and a 28-day unconfined compressive strength greater than 1.35 MPa.

Images