Preparation process of recycled fine aggregate concrete

Abstract

The invention discloses a preparation process of recycled fine aggregate concrete, which comprises the following steps: S1, carrying out graded crushing on waste recycled fine aggregate concrete through a crusher to obtain first aggregate, and cleaning to remove impurities; s2, calcining the first aggregate at the calcining temperature of 350-700 DEG C for 2-15 hours, and naturally cooling; and S3, completely immersing the completely cooled first aggregate in an acetic acid solution for soaking treatment. The invention belongs to the technical field of recycled fine aggregate concrete preparation, and aims at solving the problems that in the prior art, recycled fine aggregate concrete is unstable in quality, microcracks and pores are easily generated, and the durability of the recycled fine aggregate concrete is weakened. The recycled fine aggregate concrete has the technical effects that the formation of cracks is reduced and the durability of the recycled fine aggregate concrete is improved by adjusting the use amount of the cement and adding the silicate expanding agent and the water reducing agent in a certain proportion.

Description

Technical Field

[0001] The present application relates to the technical field of recycled fine aggregate concrete preparation, and in particular to a process for preparing recycled fine aggregate concrete. Background Art

[0002] With the acceleration of urbanization and the continuous advancement of infrastructure construction, a large number of buildings have been demolished, rebuilt or renovated, resulting in a large amount of waste recycled fine aggregate concrete, bricks and tiles, steel bars and other building materials; among them, the waste recycled fine aggregate concrete can be crushed, cleaned, graded and other processes to obtain recycled fine aggregate, and then the recycled fine aggregate is used to partially or completely replace the natural recycled fine aggregate to re-formulate recycled fine aggregate concrete; recycled fine aggregate concrete has significant advantages in environmental protection and resource conservation, and is an important component of modern green building materials, which not only helps to reduce the pollution of construction waste to the environment, but also saves natural building material resources;

[0003] For example, China's authorized publication number is CN 111592288 B, which discloses a preparation process for recycled fine aggregate concrete and the recycled fine aggregate concrete prepared therefrom, which discloses a preparation process for recycled fine aggregate concrete that can improve the bonding strength between other raw materials in the recycled fine aggregate concrete and the particles of the recycled fine aggregate dry powder, and improve the crack resistance of the recycled fine aggregate concrete.

[0004] However, during the crushing process of waste recycled fine aggregate concrete, the surface of the recycled fine aggregate is easily damaged and cracked, resulting in unstable quality of recycled fine aggregate concrete prepared by most preparation processes, which is prone to microcracks and pores. Microcracks and pores will absorb more water. When the water inside the recycled fine aggregate concrete evaporates, its volume decreases, which weakens the durability of the recycled fine aggregate concrete, thereby shortening the service life of the building over time. Summary of the invention

[0005] To this end, the present application provides a preparation process for recycled fine aggregate concrete to solve the existing problem that a unified form is used for managing and outputting user data resources of different sizes. Although this simplifies the development and maintenance process, it reduces efficiency and user experience and has poor flexibility.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] A preparation process of recycled fine aggregate concrete comprises the following steps:

[0008] S1: crushing the waste recycled fine aggregate concrete by graded crushing to obtain the first aggregate, and then washing to remove impurities;

[0009] S2: calcining the first aggregate, the calcination temperature is usually controlled at 350-700°C, the calcination time is 2-15 hours and naturally cooled;

[0010] S3: completely immersing the completely cooled first aggregate in an acetic acid solution for soaking treatment, taking it out after soaking and naturally air-drying it to a drained state, so as to prepare recycled fine aggregate;

[0011] S4: weigh 200-360 parts of recycled fine aggregate, 100-200 parts of cement, 20-35 parts of silica fume, 5-25 parts of polyurethane adhesive, 50-85 parts of water, 0.5-1.5 parts of water reducer, 0.01-0.1 parts of air entraining agent, and 10-30 parts of silicate expansion agent;

[0012] S5: Add the materials in S4 into a mixer respectively, mix them fully, and obtain recycled fine aggregate concrete.

[0013] Furthermore, the specific steps of S1 are as follows:

[0014] Step 1: remove impurities in the waste recycled fine aggregate concrete and perform preliminary crushing through a crusher to obtain first fragments, the particle size of which is less than 150 mm;

[0015] Step 2: Put the first broken pieces into a crusher for further crushing to obtain second broken pieces, wherein the particle size of the second broken pieces is less than 20 mm;

[0016] Step three: screening the second broken pieces through a screening machine to obtain a first aggregate, wherein the particle size of the first aggregate is <4.5 mm;

[0017] Step 4: Clean the first aggregate with a sand washer to remove impurities on the surface, and dry it with a dryer at a drying temperature of 140°C-260°C.

[0018] Furthermore, the concentration of the acetic acid solution is 0.08-0.15 mol / L, and the pH value is 6-7.5.

[0019] Furthermore, the water reducing agent is a melamine-based water reducing agent.

[0020] Furthermore, the specific steps of S5 are as follows:

[0021] S51: First, 100-200 parts of cement are added into a mixer, followed by 100-180 parts of recycled fine aggregate, and then 50-85 parts of water, and preliminary mixing is started for 2-10 minutes;

[0022] S52: add 20-35 parts of silica fume and the remaining 100-180 parts of recycled fine aggregate, and stir for 1-5 minutes;

[0023] S53: Then add 10-30 parts of silicate expansion agent and 5-25 parts of polyurethane adhesive, stir for 1-5 minutes, so that the polyurethane adhesive is fully integrated with various materials;

[0024] S54: Finally, 0.5-1.5 parts of water reducing agent and 0.01-0.1 parts of air entraining agent are added for final mixing to obtain recycled fine aggregate concrete.

[0025] Furthermore, the stirring time of the final stirring in S54 is 2-10 minutes, and the rotation speed of the stirrer is 400 rpm-750 rpm.

[0026] Furthermore, the soaking time for complete soaking is 1.5-2 hours, and stirring is performed once every 45-60 minutes.

[0027] Compared with the prior art, this application has at least the following beneficial effects:

[0028] In the overall preparation process, a higher proportion of cement can improve the early strength of recycled fine aggregate concrete. At the same time, combined with a certain proportion of silicate expansive agent and water reducer, by adjusting the cement dosage and adding silicate expansive agent and water reducer, a higher proportion of cement can improve the early strength of recycled fine aggregate concrete. Silicate expansive agent can release gas through chemical reaction during the preparation process, causing the volume of recycled fine aggregate concrete to expand, compensating for the volume shrinkage of recycled fine aggregate concrete due to shrinkage during the hardening process, reducing the formation of cracks, and improving the durability of recycled fine aggregate concrete. The addition of water reducer can reduce water consumption and reduce the volume shrinkage caused by water evaporation during the drying process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more intuitively illustrate the prior art and the present application, exemplary drawings are given below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing the present application; for example, those skilled in the art are capable of easily making conventional adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components) based on the technical concepts and exemplary drawings disclosed in the present application.

[0030] Figure 1 A schematic diagram of module connections for a process for preparing recycled fine aggregate concrete provided in one embodiment of the present application. DETAILED DESCRIPTION

[0031] The present application is further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0032] like Figure 1As shown, a preparation process of recycled fine aggregate concrete in an embodiment of the first aspect of the present application specifically comprises the following steps:

[0033] S1: crushing the waste recycled fine aggregate concrete by graded crushing to obtain the first aggregate, and then washing to remove impurities;

[0034] The specific steps of S1 are as follows:

[0035] Step 1: remove impurities in the waste recycled fine aggregate concrete and perform preliminary crushing through a crusher to obtain first fragments, the particle size of which is less than 150 mm;

[0036] Step 2: Put the first broken pieces into a crusher for further crushing to obtain second broken pieces, wherein the particle size of the second broken pieces is less than 20 mm;

[0037] Step 3: Screening the second broken pieces through a screening machine to obtain a first aggregate, the particle size of the first aggregate is <4.5 mm. Through this step, it is ensured that all particles larger than 4.5 mm are removed, thereby improving the final quality and uniformity;

[0038] Step 4: The first aggregate is cleaned by a sand washer to remove impurities on the surface, and then dried by a dryer at a temperature of 140°C-260°C to ensure that the material is dried quickly and evenly while avoiding changes in the material properties that may be caused by excessively high temperatures.

[0039] During the crushing process, the fragments below the standard particle size need to be sent back to the crusher for further crushing, forming a closed-loop cycle.

[0040] S2: Calcine the first aggregate, the calcination temperature is usually controlled at 350-700℃, the calcination time is 2-15 hours and naturally cooled. The main purpose of calcination is to remove combustible impurities in the recycled fine aggregate and reduce the moisture content. Within this calcination temperature range, the combustible impurities can be effectively burned, and the performance of the aggregate itself will not be significantly damaged; specifically, when the temperature reaches about 350℃, the combustible impurities begin to burn; as the temperature rises, the combustion reaction gradually intensifies until the temperature reaches about degrees Celsius, most of the combustible impurities can be completely burned.

[0041] S3: The first aggregate after complete cooling is thoroughly immersed in the acetic acid solution for soaking treatment. After the soaking is completed, it is taken out and naturally air-dried to a drained state to prepare the recycled fine aggregate. The soaking time is 1.5-2 hours, and it is stirred once every 45-60 minutes; the soaking is complete to ensure that the soaking liquid is in full contact with the recycled fine aggregate; at the same time, the concentration of the acetic acid solution is 0.08-0.15 mol / L, and the pH value is 6-7.5. The acetic acid solution can react chemically with the cement product in the recycled fine aggregate, which helps to dissolve and remove part of the hardened cement mortar attached to the surface of the recycled fine aggregate, thereby increasing the surface friction coefficient of the recycled fine aggregate, which is convenient for improving the bonding force between the recycled fine aggregate and the material during subsequent preparation. In addition, the acetic acid solution reacts chemically with the cement product in the recycled fine aggregate to produce calcium carbonate, which can be filled in the pores of the recycled fine aggregate, thereby improving the density and strength of the recycled fine aggregate;

[0042] S4: weigh 200-360 parts of recycled fine aggregate, 100-200 parts of cement, 20-35 parts of silica fume, 5-25 parts of polyurethane adhesive, 50-85 parts of water, 0.5-1.5 parts of water reducer, 0.01-0.1 parts of air entraining agent, 10-30 parts of silicate expansion agent, the water reducer is a melamine-based water reducer;

[0043] The particle size of silica fume is smaller than that of cement particles, and it can fill the gaps between cement particles, making the recycled fine aggregate concrete denser and reducing the porosity, thereby improving the strength and impermeability of the recycled fine aggregate concrete.

[0044] Air-entraining agent is an anionic surfactant. When it is added to the recycled fine aggregate concrete mixture, it can be oriented and adsorbed on the air-liquid interface to form a stable bubble structure. The bubble structure can cut off the capillary pathways in the recycled fine aggregate concrete, reduce water permeability and the destructive effects of freeze-thaw cycles on the recycled fine aggregate concrete.

[0045] Water reducing agent: Using high-efficiency water reducing agent can reduce water consumption, lower the water-cement ratio, and thus reduce shrinkage;

[0046] During the preparation process, silicate expansive agent can release gas through chemical reaction, causing the volume of recycled fine aggregate concrete to expand, compensating for the volume shrinkage of recycled fine aggregate concrete due to shrinkage during the hardening process, reducing the formation of cracks, and improving the durability of recycled fine aggregate concrete.

[0047] S5: adding the materials in S4 into a mixer respectively and mixing them fully to obtain recycled fine aggregate concrete;

[0048] S51: First, add 100-200 parts of cement into the mixer, then add 100-180 parts of recycled fine aggregate, and then add 50-85 parts of water, and start preliminary stirring for 2-10 minutes to ensure that the materials are initially mixed evenly;

[0049] S52: Add 20-35 parts of silica fume and the remaining 100-180 parts of recycled fine aggregate, and stir for 1-5 minutes to ensure that the silica fume and recycled fine aggregate are fully dispersed and react with cement and other materials;

[0050] S53: Then add 10-30 parts of silicate expansion agent and 5-25 parts of polyurethane adhesive, stir for 1-5 minutes, so that the polyurethane adhesive is fully integrated with various materials;

[0051] S54: Finally, add 0.5-1.5 parts of water reducing agent and 0.01-0.1 parts of air entraining agent for final mixing to obtain recycled fine aggregate concrete; the mixing time is 2-10 minutes, and the speed of the mixer is 400 rpm-750 rpm, so that the water reducing agent and the air entraining agent are fully dispersed and play a role, so as to ensure that the materials are mixed evenly and there is no excessive mixing that causes the performance of the recycled fine aggregate concrete to deteriorate.

[0052] In summary, in the preparation method, the cement content accounts for a relatively large proportion in the overall preparation process, which can improve the early strength of the recycled fine aggregate concrete. At the same time, combined with a certain proportion of silicate expansive agent and water reducer, the silicate expansive agent can release gas through chemical reaction during the preparation process, so that the volume of the recycled fine aggregate concrete expands, compensates for the volume shrinkage of the recycled fine aggregate concrete due to shrinkage during the hardening process, reduces the formation of cracks, and improves the durability of the recycled fine aggregate concrete. The addition of water reducer can reduce the water consumption and reduce the water-cement ratio (i.e., the ratio of water to cement). A lower water-cement ratio means that there is less water in the recycled fine aggregate concrete, thereby reducing the volume shrinkage caused by water evaporation during the drying process. By adjusting the amount of cement, adding silicate expansive agent and water reducer, the early strength of the recycled fine aggregate concrete is improved, and the occurrence of shrinkage is effectively reduced, thereby improving the durability and working performance of the recycled fine aggregate concrete.

[0053] A specific application example is given below:

[0054] S1: crushing the waste recycled fine aggregate concrete by graded crushing to obtain the first aggregate, and then washing to remove impurities;

[0055] S2: calcining the first aggregate, the calcination temperature is usually controlled at 500° C., the calcination time is 2 hours and naturally cooled.

[0056] S3: completely immerse the completely cooled first aggregate in the acetic acid solution of the impregnation liquid for 2 hours, and stir once every 45 minutes, and drain naturally to obtain the recycled fine aggregate; completely immerse to ensure that the impregnation liquid is in full contact with the recycled fine aggregate; at the same time, the concentration of the acetic acid solution is 0.08-0.15 mol / L, and the pH value is 6-7.5. The acetic acid solution can react chemically with the cement product in the recycled fine aggregate, which helps to dissolve and remove part of the hardened cement mortar attached to the surface of the recycled fine aggregate, thereby increasing the surface friction coefficient of the recycled fine aggregate, and facilitating the improvement of the bonding force between the recycled fine aggregate and the material during subsequent preparation. In addition, the acetic acid solution reacts chemically with the cement product in the recycled fine aggregate to produce calcium carbonate, which can be filled in the pores of the recycled fine aggregate, thereby improving the density and strength of the recycled fine aggregate;

[0057] S4: weigh 200 parts of recycled fine aggregate, 200 parts of cement, 35 parts of silica fume, 25 parts of polyurethane adhesive, 80 parts of water, 1 part of water reducing agent, 0.07 parts of air entraining agent, and 20 parts of silicate expansion agent;

[0058] S5: adding the materials in S4 into a mixer respectively and mixing them fully to obtain recycled fine aggregate concrete;

[0059] S51: First, 200 parts of cement are added into the mixer, followed by 100 parts of recycled fine aggregate, and then 80 parts of water, and initial stirring is started for 5 minutes to ensure that the materials are initially mixed evenly;

[0060] S52: add 35 parts of silica fume and the remaining 100 parts of recycled fine aggregate, and stir for 3 minutes to ensure that the silica fume and recycled fine aggregate are fully dispersed and react with cement and other materials;

[0061] S53: Then add 20 parts of silicate expansion agent and 25 parts of polyurethane adhesive, and stir for 5 minutes to fully blend the polyurethane adhesive with various materials;

[0062] S54: Finally, 1 part of water reducing agent and 0.07 part of air entraining agent were added for final mixing. The mixing time was 6 minutes and the speed of the mixer was 500 rpm to obtain recycled fine aggregate concrete.

[0063] The technical features of the above embodiments may be arbitrarily combined (as long as there is no contradiction in the combination of these technical features). To make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A process for preparing recycled fine aggregate concrete, characterized in that: The following steps are involved: S1: crushing the waste recycled fine aggregate concrete by graded crushing to obtain the first aggregate, and washing to remove impurities; S2: calcining the first aggregate, the calcination temperature is usually controlled at 350-700°C, the calcination time is 2-15 hours and naturally cooled; S3: completely immersing the completely cooled first aggregate in an acetic acid solution for soaking treatment, taking it out after soaking and naturally air-drying it to a drained state, so as to prepare recycled fine aggregate; S4: weigh 200-360 parts of recycled fine aggregate, 100-200 parts of cement, 20-35 parts of silica fume, 5-25 parts of polyurethane adhesive, 50-85 parts of water, 0.5-1.5 parts of water reducer, 0.01-0.1 parts of air entraining agent, and 10-30 parts of silicate expansion agent; S5: Add the materials in S4 into a mixer respectively, mix them fully, and obtain recycled fine aggregate concrete.

2. The process for preparing recycled fine aggregate concrete according to claim 1, characterized in that: The specific steps of S1 are as follows: Step 1: remove impurities in the waste recycled fine aggregate concrete and perform preliminary crushing through a crusher to obtain first fragments, the particle size of which is less than 150 mm; Step 2: Put the first broken pieces into a crusher for further crushing to obtain second broken pieces, wherein the particle size of the second broken pieces is less than 20 mm; Step three: screening the second broken pieces through a screening machine to obtain a first aggregate, wherein the particle size of the first aggregate is <4.5 mm; Step 4: Clean the first aggregate with a sand washer to remove impurities on the surface, and dry it with a dryer at a drying temperature of 140°C-260°C.

3. The process for preparing recycled fine aggregate concrete according to claim 1, characterized in that: The concentration of the acetic acid solution is 0.08-0.15 mol / L, and the pH value is 6-7.

5.

4. The process for preparing recycled fine aggregate concrete according to claim 1, characterized in that: The water reducing agent is a melamine-based water reducing agent.

5. The process for preparing recycled fine aggregate concrete according to claim 1, characterized in that: The specific steps of S5 are as follows: S51: First, 100-200 parts of cement are added into a mixer, followed by 100-180 parts of recycled fine aggregate, and then 50-85 parts of water, and preliminary mixing is started for 2-10 minutes; S52: add 20-35 parts of silica fume and the remaining 100-180 parts of recycled fine aggregate, and stir for 1-5 minutes; S53: Then add 10-30 parts of silicate expansion agent and 5-25 parts of polyurethane adhesive, stir for 1-5 minutes, so that the polyurethane adhesive is fully integrated with various materials; S54: Finally, 0.5-1.5 parts of water reducing agent and 0.01-0.1 parts of air entraining agent are added for final mixing to obtain recycled fine aggregate concrete.

6. The process for preparing recycled fine aggregate concrete according to claim 5, characterized in that: The stirring time of the final stirring in S54 is 2-10 minutes, and the rotation speed of the stirrer is 400 rpm-750 rpm.

7. The process for preparing recycled fine aggregate concrete according to claim 1, characterized in that: The soaking time for the complete soaking is 1.5-2 hours, and stirring is performed once every 45-60 minutes.

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