Preparation method of mixed recycled aggregate concrete and mixed recycled aggregate concrete

Abstract

The application discloses a preparation method of mixed recycled aggregate concrete and the mixed recycled aggregate concrete. The preparation method comprises the following steps: preparing the mixed recycled aggregate concrete by using cement, mixed recycled aggregate, mixed sand, fly ash and an additive; the mixed recycled aggregate is prepared by mixing recycled aggregate and virgin aggregate; the mixed sand is prepared by mixing recycled fine particles and natural sand; and the mortar is prepared by using the mixed sand. The mass proportion of the recycled aggregate in the mixed recycled aggregate, the non-uniform coefficient of the mixed recycled aggregate, the grading coefficient and the void ratio of the mixed recycled aggregate are limited, so that the reasonable range of the non-uniform coefficient and the grading coefficient of the mixed recycled aggregate with large bulk density and small void ratio is determined, and the mixed sand is filled correspondingly, so that the mixed recycled aggregate concrete with high strength is prepared, the mixed recycled aggregate concrete replaces the pouring material of the high-performance concrete structure, and the application range of the recycled aggregate concrete is greatly widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a preparation method of mixed recycled aggregate concrete and the mixed recycled aggregate concrete. BACKGROUND

[0002] In engineering construction, mixed recycled aggregate concrete can consume a large amount of old concrete discarded as garbage, thereby changing waste into treasure, saving a large amount of natural aggregate and natural sand resources, and having the important functions of energy saving and emission reduction and green environmental protection.

[0003] At present, recycled aggregate concrete has the adverse properties of low strength, high porosity, strong water permeability and low durability, and can only be used as building concrete with a low strength grade. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the prior art. To this end, the present application provides a preparation method of mixed recycled aggregate concrete, which uses the characteristics of uneven particles filling each other, determines the reasonable range of the uneven coefficient and the grading coefficient of the mixed recycled aggregate with a large packing density and a small void ratio, and the corresponding filling fine particle material, so as to prepare high-strength grade mixed recycled aggregate concrete, replace the pouring material of high-performance concrete structure, and greatly widen the application range of recycled aggregate concrete.

[0005] The present application also provides a mixed recycled aggregate concrete prepared by using the preparation method of the mixed recycled aggregate concrete.

[0006] According to the preparation method of the mixed recycled aggregate concrete according to the first aspect of the present application, the mixed recycled aggregate concrete is prepared by using cement, mixed recycled aggregate, mixed sand material, fly ash and additive;

[0007] The mixed recycled aggregate includes recycled aggregate and virgin aggregate and is mixed, and the mass ratio of the recycled aggregate to the mixed recycled aggregate is α, which satisfies:

[0008]

[0009]

[0010] wherein, represents the mass of the recycled aggregate; represents the mass of the mixed aggregate; is the design value of the strength of the concrete; is the compressive strength of the fresh aggregate, and the requirement is ; is the compressive strength of the recycled aggregate;

[0011] The particle size of the recycled aggregate ranges from 10 to 30 mm, the particle size of the primary aggregate ranges from 10 to 35 mm, and the non-uniformity coefficient of the mixed recycled aggregate greater than 5, the grading coefficient in the range of 1-3;

[0012] wherein, , , are the diameters of the mixed aggregate particles corresponding to the cumulative mass percentage of 10%, 30%, and 60% from small particle size to large particle size, respectively;

[0013] The mixed sand material includes recycled fine particles and natural sand and is mixed, and the recycled fine particles account for a total mass percentage of the mixed sand material β satisfying 0.4≤β≤0.6;

[0014] The mixed sand material is prepared into mortar, and based on the particle size configuration of the mixed recycled aggregate, the void ratio of the mixed recycled aggregate pile is measured , and then the mortar volume ratio of the mixed sand material is configured to be 0.2-0.4, and the mortar amount of the concrete with a water-binder ratio of 0.2-0.4 is prepared according to the mortar-aggregate ratio, so as to prepare the concrete with different fluidity requirements;

[0015] wherein, the mortar volume ratio represents the mortar volume per unit volume of mixed aggregate; and the water-binder ratio represents the value of water / (cement+fly ash).

[0016] The preparation method of the mixed recycled aggregate concrete according to the first aspect of the present application has at least the following beneficial effects: the present application determines the reasonable range of the non-uniformity coefficient and the grading coefficient of the mixed recycled aggregate with a large packing density and a small void ratio by specifically limiting the mass proportion of the recycled aggregate in the mixed recycled aggregate, the non-uniformity coefficient of the mixed recycled aggregate, the grading coefficient, and the void ratio, and fills the mixed sand material accordingly, so as to prepare the mixed recycled aggregate concrete with a high strength grade, replace the pouring material of the high-performance concrete structure, and greatly widen the application range of the recycled aggregate concrete.

[0017] The preparation method of the mixed recycled aggregate concrete according to the first aspect of the present application, the recycled aggregate is made of waste concrete blocks with a strength grade of C20 or above or recycled aggregate separated therefrom.

[0018] The preparation method of the mixed recycled aggregate concrete according to the first aspect of the present application, the recycled aggregate is selected by a process including mechanical crushing and sieving and water washing.

[0019] The preparation method of the mixed recycled aggregate concrete according to the first aspect of the present application, the primary aggregate is a natural crushed stone aggregate.

[0020] According to the preparation method of the mixed recycled aggregate concrete of the first aspect of the present application, the particle size of the recycled fine particles is 0.5-2mm.

[0021] According to the preparation method of the mixed recycled aggregate concrete of the first aspect of the present application, the recycled fine particles are the particle materials screened out during mechanical crushing and washed with water when preparing the recycled aggregate.

[0022] According to the preparation method of the mixed recycled aggregate concrete of the first aspect of the present application, the additive is a retarding type polycarboxylate high-performance water reducing agent.

[0023] According to the preparation method of the mixed recycled aggregate concrete of the first aspect of the present application, the natural sand uses natural medium sand.

[0024] According to the preparation method of the mixed recycled aggregate concrete of the first aspect of the present application, the cement uses PO42.5R cement.

[0025] The mixed recycled aggregate concrete of the second aspect of the present application comprises: being prepared by using the preparation method of the mixed recycled aggregate concrete of the first aspect of the present application.

[0026] It is not difficult to understand that the mixed recycled aggregate concrete in the second aspect of the present application has the technical effects of the preparation method of the mixed recycled aggregate concrete in the first aspect of the present application as described above, and thus will not be described again.

[0027] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0028] The present application will be further described below in conjunction with the drawings and examples;

[0029] Figure 1 The following are schematic diagrams of some sample embodiments of the present application. DETAILED DESCRIPTION

[0030] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0031] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right and the like, is based on the orientation or position relationship shown in the drawings, and is only for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0032] In the description of the present application, several meanings are one or more, and multiple meanings are at least two. Greater than, less than, more than, etc. are understood as not including the number, and above, below, etc. are understood as including the number. If the first, second is described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0033] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and the person skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical scheme.

[0034] It can be understood that the mixed recycled aggregate concrete is prepared from cement, mixed recycled aggregate, sand and recycled fine aggregate, fly ash, and other raw materials. The mixed recycled aggregate is uniformly mixed from recycled aggregate and natural aggregate. The recycled aggregate is waste concrete blocks or recycled aggregate separated therefrom and other materials. The recycled fine aggregate is fine particle material screened during mechanical crushing for preparing recycled aggregate.

[0035] Referring to Figure 1 , the preparation method of the mixed recycled aggregate concrete of the first aspect embodiment of the present application comprises: being prepared from cement, mixed recycled aggregate, mixed sand material, fly ash and admixture;

[0036] The mixed recycled aggregate is mixed from recycled aggregate and virgin aggregate, and the mass ratio α of the recycled aggregate in the mixed recycled aggregate satisfies:

[0037]

[0038]

[0039] Wherein, represents the mass of the recycled aggregate; represents the mass of the mixed aggregate; is the design value of the concrete strength; is the fresh aggregate compressive strength, and the requirement is ; is the recycled aggregate compressive strength;

[0040] The particle size range of recycled aggregate is 10~30mm, and the particle size range of virgin aggregate is 10~35mm. The uniformity coefficient of the mixed recycled aggregate is... Greater than 5, gradation coefficient Within the range of 1-3;

[0041] in, , , These are the particle diameters of the mixed aggregate when the cumulative mass percentage of the aggregate from small to large particle size is 10%, 30%, and 60% of the total mass, respectively.

[0042] The mixed sand material consists of recycled fine particles and natural sand, and the percentage of recycled fine particles in the total mass of the mixed sand material is β, which satisfies the following condition: 0.4 ≤ β ≤ 0.6.

[0043] Mortar was prepared by mixing sand and gravel, and the porosity of the mixed recycled aggregate was measured based on the particle size distribution of the mixed recycled aggregate. Then according to The volume ratio of mortar is used to prepare the amount of mortar for concrete with a water-cement ratio in the range of 0.2 to 0.4, and concrete with different fluidity requirements is prepared accordingly based on the mortar aggregate ratio.

[0044] Among them, mortar volume ratio represents the mortar volume per unit volume of mixed aggregate; water-cement ratio represents the value of water / (cement + fly ash).

[0045] Reference Figure 1 The method for preparing mixed recycled aggregate concrete according to the first aspect of this application is as follows: by specifically limiting the mass ratio of recycled aggregate to mixed recycled aggregate, the non-uniformity coefficient, the gradation coefficient and the porosity of the mixed recycled aggregate, a reasonable range of the non-uniformity coefficient and gradation coefficient of the mixed recycled aggregate with high bulk density and low porosity is determined, and corresponding filling mixed sand is used to prepare high-strength mixed recycled aggregate concrete, which can replace the casting material of high-performance concrete structure and greatly broaden the application range of recycled aggregate concrete.

[0046] In some embodiments of this application, the recycled aggregate is made from waste concrete blocks with a C20 or higher grade, or recycled aggregate separated from them. Preferably, the recycled aggregate is processed by a process including mechanical crushing and screening, and water washing. Further, the particle size of the recycled fine particles is 0.5~2mm, and the recycled fine particles are the granular material that has been screened out during mechanical crushing and water washing during the preparation of the recycled aggregate.

[0047] It can be understood that by limiting the raw material of the recycled aggregate to the waste concrete blocks above C20, the strength of the mixed recycled aggregate concrete prepared can basically meet the design strength grade requirement, wherein the waste concrete blocks are mechanically crushed, and the particle size is controlled by sieving with a specific sieve aperture to meet the preparation conditions.

[0048] In some embodiments of the present application, the virgin aggregate is a natural crushed stone aggregate, specifically a fresh natural crushed stone aggregate. Further, the admixture is a retarding type polycarboxylate high performance water reducing agent, and other water reducing agents with similar functions can also be used. The cement used is PO42.5R cement, and other cements with similar functions can also be used.

[0049] In some embodiments of the present application, the natural sand is natural medium sand, and the mixed sand is mixed from natural medium sand and recycled fine aggregate, which is used to replace the natural sand required for preparing the mixed recycled aggregate concrete sample in equal amount, and the compressive strength test meets the design strength grade requirement.

[0050] Referring to Figure 1 , the experimental results and implementation cases of the present application are as follows:

[0051] It should be noted that by limiting the uniformity coefficient and the grading coefficient to be in a suitable numerical range, the mixed aggregate has excellent bulk density, and the inherent high porosity, high water permeability, and low strength of the recycled concrete are improved.

[0052] Table 1 shows the test results of the bulk density of different grading aggregate particles. As can be seen from the values in Table 1, the grading coefficient of the mixed aggregate is In the range, the bulk density increases with the increase of the uniformity coefficient , and the uniformity coefficient is in the range of 5.5~6.7, the corresponding bulk density change range is 1545~1585 kg m-3, and the corresponding void ratio change range is 42.4~40.9%. According to the national standard “Construction Pebble, Crushed Stone” (GB / T 14685-2011), when the void ratio is less than 43% (the bulk density is 1528 kg m-3 when the apparent density is 2680 kg m-3), the crushed stone is class I, which can be used for the preparation of high-grade (C60 and above) concrete. Therefore, the aggregate for preparing high-quality concrete can be prepared according to the content of the present application.

[0053] Table 1 shows the test results of the bulk density of different grading aggregate particles.

[0054]

[0055] Note: The ratio in the table refers to the ratio of the mass of aggregate in each particle size distribution range to the mass of the mixed aggregate.

[0056] It should be noted that according to the national standard "Construction with pebbles, gravel" (GB / T 14685-2011) and "Concrete structure engineering construction specification" (GB50666-2011), the preparation of strength grade C40~C60 concrete, the aggregate crushing index value ≤10%. Based on this provision, Appendix Table 2 gives the mixed recycled aggregate concrete cube specimen material mix ratio, for which the fine aggregate (mixed sand) in Table 2 of the mixed recycled aggregate concrete cube specimen material mix ratio is mixed by natural medium sand and recycled fine aggregate with a mass of 50% respectively, instead of the natural sand required for preparing mixed recycled aggregate concrete specimens, and the compressive strength experiment meets the design strength grade requirement.

[0057] Wherein the mass ratio of recycled aggregate α (limit value) calculated by the formula is about 1.5, and since α>1.0, the mass ratio of recycled aggregate α (replacement rate) can be selected in the range of 0~100%. Table 3 gives the corresponding mixed recycled aggregate concrete cube specimen compressive strength (28d) test results, from which it can be seen that the strength of the mixed recycled aggregate concrete (A0 is a non-mixed recycled aggregate concrete specimen) basically meets the design strength grade requirement.

[0058] Table 2 Mixed recycled aggregate concrete cube specimen material mix ratio

[0059]

[0060] Note: 1. Gravel (aggregate) is considered as metamorphic rock or plutonic igneous rock, and the crushing index value is taken as 10% according to the specification "Concrete structure engineering construction specification" (GB50666-2011);

[0061] 2. The replacement rate of recycled aggregate is: recycled aggregate mass / total aggregate mass;

[0062] 3. Under the same crushing index value, the strength of recycled aggregate is about 85% of the strength of natural coarse aggregate;

[0063] 4. The mass ratio of recycled aggregate α (limit value) calculated by the formula is about 1.5, and since α>1.0, the mass ratio of recycled aggregate α (replacement rate) can be selected in the range of 0~100%;

[0064] 5. Fine aggregate (mixed sand) is mixed by natural medium sand and recycled fine aggregate with a mass of 50% respectively;

[0065] 6. The water-binder ratio is calculated as "water / (cement+fly ash)";

[0066] 7. The admixture is a retarding type polycarboxylate high performance water reducing agent.

[0067] Table 3 Test results of the compressive strength (28d) of the mixed recycled aggregate concrete cubes

[0068]

[0069] Note: 1. The specimen size is 100mm x 100mm x 100mm;

[0070] 2. The average value is calculated according to the size conversion factor (reduction) of 0.95.

[0071] It should be noted that Appendix Tables 4 and 5 list the main raw material ratios of the mixed recycled aggregate concrete of the implementation cases 1-4.

[0072] Table 4 Main raw material ratios of the mixed recycled aggregate concrete of the implementation cases 1 and 2

[0073]

[0074] Table 5 Main raw material ratios of the mixed recycled aggregate concrete of the implementation cases 3 and 4

[0075]

[0076] With reference to Figure 1 The mixed recycled aggregate concrete of the second aspect embodiment of the present application is prepared by using the preparation method of the mixed recycled aggregate concrete of the first aspect embodiment of the present application, is suitable for replacing the pouring material of the high performance concrete structure, and greatly widens the application range of the recycled aggregate concrete.

[0077] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0078] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

Claims

1. A method for preparing mixed recycled aggregate concrete, characterized in that, include: It is prepared by cement, mixed recycled aggregate, mixed sand, fly ash and admixtures; The mixed recycled aggregate comprises recycled aggregate and virgin aggregate mixed together, and the mass ratio α of the recycled aggregate to the mixed recycled aggregate satisfies: in, Indicates the quality of recycled aggregate; Indicates the quality of the mixed recycled aggregate; This refers to the design value of concrete strength. The compressive strength of the virgin aggregate is required. ; The compressive strength of recycled aggregate; The recycled aggregate has a particle size range of 10-30 mm, the virgin aggregate has a particle size range of 10-35 mm, and the uniformity coefficient of the mixed recycled aggregate is [not specified]. Greater than 5, gradation coefficient Within the range of 1-3; in, , , These are the particle diameters of the mixed recycled aggregate when the cumulative mass percentage of the total mass from small to large particle size is 10%, 30%, and 60%, respectively. The mixed sand material comprises recycled fine particles and natural sand, and the recycled fine particles account for a total mass percentage β of the mixed sand material that satisfies the following condition: 0.4 ≤ β ≤ 0.

6. Mortar is prepared by mixing the sand and gravel, and the porosity of the mixed recycled aggregate is measured based on the particle size distribution of the mixed recycled aggregate. Then according to The volume ratio of mortar is used to prepare the amount of mortar for concrete with a water-cement ratio in the range of 0.2 to 0.4, and concrete with different fluidity requirements is prepared accordingly based on the mortar aggregate ratio. Among them, mortar volume ratio represents the mortar volume per unit volume of mixed aggregate; water-cement ratio represents the value of water / (cement + fly ash).

2. The method for preparing mixed recycled aggregate concrete according to claim 1, characterized in that: The recycled aggregate is made from waste concrete blocks with a C20 or higher rating, or recycled aggregate separated from them.

3. The method for preparing mixed recycled aggregate concrete according to claim 2, characterized in that: The recycled aggregate is processed through mechanical crushing and screening, and water washing.

4. The method for preparing mixed recycled aggregate concrete according to claim 1, characterized in that: The primary aggregate is natural crushed stone aggregate.

5. The method for preparing mixed recycled aggregate concrete according to claim 1, characterized in that: The particle size of the regenerated fine particles is 0.5~2mm.

6. The method for preparing mixed recycled aggregate concrete according to claim 5, characterized in that: The recycled fine particles are granular materials that are screened out during mechanical crushing and washed with water during the preparation of recycled aggregate.

7. The method for preparing mixed recycled aggregate concrete according to claim 1, characterized in that: The admixture is a retarding polycarboxylate high-performance water-reducing agent.

8. The method for preparing mixed recycled aggregate concrete according to claim 1, characterized in that: The natural sand used is medium-sized natural sand.

9. The method for preparing mixed recycled aggregate concrete according to claim 1, characterized in that: The cement used is PO42.5R cement.

10. A type of mixed recycled aggregate concrete, characterized in that, include: It is prepared using the method for preparing mixed recycled aggregate concrete as described in any one of claims 1 to 9.

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