Preparation method of interface delayed coagulation concrete test piece

Abstract

The invention discloses a preparation method of an interface delayed coagulation concrete test piece, and belongs to the field of concrete material surface treatment. The preparation method of the interface delayed coagulation concrete test piece comprises the following steps: preparing the delayed coagulation functional paper. Selecting at least one of the horizontal interface and the vertical interface to form a delayed coagulation layer; if a horizontal interface is selected, the concrete mixture is put into a test mold and then vibrated to be compact, and retarding functional paper is attached to the concrete forming top face; and if the vertical interface is selected, atomizing and spraying water to the surface of the side wall of the test mold, attaching retarding functional paper to the wet side wall, loading a concrete mixture into the test mold, and vibrating and compacting the concrete mixture. And finally, demolding after curing to obtain the interface delayed coagulation concrete test piece. According to the preparation method, the consistency of the thickness and the roughness of an interface delayed coagulation layer can be ensured, and the phenomena of delayed coagulation failure or local bonding weakness caused by levelness deviation on a horizontal interface and structural defects caused by retarder flow falling on a vertical interface are thoroughly eliminated.

Description

Technical Field

[0001] The present invention relates to the field of surface treatment of concrete materials, and particularly to a method for preparing an interfacial retarded concrete specimen. Background Art

[0002] In the construction of concrete projects, due to diverse structural forms and different cross-sectional dimensions, it is often necessary to carry out sub - pouring to achieve the overall structural form required by the design, thus generating the interface between new and old concrete. To ensure the effective bonding of new and old concrete and form an overall load - bearing performance, it is necessary to roughen the contact surface of the existing concrete to eliminate the smooth layer on the surface of the solidified concrete and form a uniformly rough surface. However, there are significant defects in the surface retarder treatment process for the interface between new and old concrete (including horizontal and vertical interfaces) in the prior art, which are specifically manifested as follows:

[0003] 1. Problems in horizontal interface treatment:

[0004] Currently, in the construction of horizontal interfaces, low - viscosity liquid surface retarders (such as water - based retarders) that can be sprayed are mostly used, and their fluidity is close to that of water. When the interface is not absolutely horizontal, the retarder is prone to gather in low - lying areas under the action of gravity, resulting in uneven distribution of the interface retarder. In some local areas, the surface concrete setting cannot be effectively retarded, and it is difficult to form a uniformly rough surface, seriously affecting the bonding strength and integrity of the interface between new and old concrete.

[0005] 2. Problems in vertical interface treatment:

[0006] For vertical interfaces, high - viscosity paste - like surface retarders are usually applied to the inner side of the formwork. However, due to its own weight, the paste - like retarder is prone to fall along the formwork and accumulate at the bottom of the formwork. During the subsequent concrete pouring process, the falling retarder not only acts on the vertical interface but also contacts the bottom concrete, resulting in abnormal setting of the bottom - area concrete (such as insufficient local strength or delayed hardening), forming an unexpected structural weak point and increasing the potential risks of construction quality.

[0007] The above - mentioned technical defects lead to unstable bonding performance of the interface between new and old concrete, and are prone to problems such as interface peeling and stress concentration, directly affecting the durability and safety of the structure. Therefore, there is an urgent need to develop an interface treatment technology that can adapt to different interface forms, act uniformly on the target area and avoid the migration of the retarder, so as to improve the collaborative working performance of new and old concrete and eliminate construction quality risks. Summary of the Invention

[0008] In view of this, the present invention provides a method for preparing an interfacial retarded concrete specimen, mainly aiming to solve the problem that due to the levelness of the horizontal interface of water - based surface concrete, the surface retarder gathers in low - lying areas, resulting in the surface retarder not being able to act uniformly on the entire interface; and to solve the problem of the paste - like surface retarder flowing down when applied to the side of the formwork.

[0009] The technical solution of the present invention is as follows: The preparation method of the interfacial retarding concrete specimen includes the following steps:

[0010] Step 1, prepare the retarding functional paper: spray the water-based surface retarding agent on the absorbent paper and air-dry it naturally.

[0011] Step 2, select at least one of the horizontal interface or the vertical interface to form a retarding layer:

[0012] If the horizontal interface is selected, then execute:

[0013] S21a, after loading the concrete mixture into the mold, vibrate it until it is dense.

[0014] S22a, attach the retarding functional paper to the top surface of the formed concrete and cover it with a plastic film to activate the retarding function by using the moisture of the concrete.

[0015] If the vertical interface is selected, then execute:

[0016] S21b, atomize and spray water on the side wall surface of the mold.

[0017] S22b, attach the retarding functional paper to the wet side wall and spray the release agent on the other side walls that do not need retarding.

[0018] S23b, load the concrete mixture into the mold and vibrate it until it is dense.

[0019] Step 3, demold after curing to obtain the interfacial retarding concrete specimen.

[0020] According to the above-mentioned preparation method of the interfacial retarding concrete specimen, the water absorption rate of the absorbent paper is ≥ 2.5 g / m 2 , and the gram weight is 4.5 g / m 2 ~ 10.0 g / m 2 ;

[0021] The absorbent paper is one of toilet paper, tissue paper, hand wipe paper, and kitchen paper.

[0022] Furthermore, the spraying amount range of the water-based surface retarding agent corresponding to the area of the absorbent paper is 125 g / m 2 ~ 275 g / m 2 .

[0023] According to the above-mentioned preparation method of the interfacial retarding concrete specimen, the water-based surface retarding agent contains at least one functional component selected from the following categories: hydroxycarboxylic acids and their salts, phosphates, sulfonates, carbohydrate compounds, boric acid and its salts, polyols.

[0024] Preferably, the absorbent paper is toilet paper, and the water absorption rate of the toilet paper is 4.0 g / m2 with a grammage of 4.5 g / m 2 ;

[0025] The water-based surface retarder is sucrose;

[0026] The spraying amount of the water-based surface retarder corresponding to the area of the absorbent paper ranges from 250 to 275 g / m².

[0027] Preferably, the absorbent paper is toilet paper, and the water absorption rate of the toilet paper is 4.0 g / m 2 with a grammage of 4.5 g / m 2 ;

[0028] The water-based surface retarder is sodium citrate;

[0029] The spraying amount of the water-based surface retarder corresponding to the area of the absorbent paper ranges from 200 to 250 g / m².

[0030] According to the foregoing method for preparing the interface-retarded concrete specimen, when a retardation layer is formed on both the horizontal interface and the vertical interface simultaneously, the vertical interface is treated first and then the horizontal interface is treated.

[0031] According to the foregoing method for preparing the interface-retarded concrete specimen, the curing conditions in step 3 are a temperature of 25 ± 5°C and a placement time of 24 ± 2 h.

[0032] According to the foregoing method for preparing the interface-retarded concrete specimen, the concrete mixture includes: cement, coarse aggregate, and fine aggregate;

[0033] The cement is one or more of Portland cement, ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, and composite Portland cement.

[0034] Furthermore, the particle size of the coarse aggregate is 5 to 20 mm, and the fineness modulus of the fine aggregate is 2.3 to 3.0.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Based on a mature water-based surface retarder system, it is loaded on the surface of the absorbent paper through a quantitative spraying process and forms a retardation functional paper after air drying and curing. Among them, the porosity and water absorption of the absorbent paper are adapted to the penetration characteristics of the retarder solution, ensuring that the retarder is evenly distributed and fixed inside the absorbent paper; through the precise metering control of the spraying equipment, the consistency of the application amount of the retarder per unit area is achieved, thus overcoming the dosage deviation problem caused by fluidity in the traditional spraying process.

[0037] 2. The retarding functional paper has physical cutting characteristics, and can be customized in size and shape according to the construction interface form (such as horizontal joint surface, vertical joint surface or special-shaped structural surface), so as to achieve precise boundary definition of the retarding effect area. The diffusion or migration of the retarder in non-target areas can be avoided by fitting the cut functional paper to the template or interface, which is especially suitable for the refined treatment of complex structural interfaces and small-sized joint surfaces.

[0038] 3. The retarding functional paper is used in conjunction with concrete of specific components. During the pouring process, the concrete forms a directional extrusion rather than shear damage to the retarding functional paper, ensuring that the retarding functional paper remains intact in the interface area and continuously releases the retarding components, eventually forming a uniform rough interface transition layer. The compressive strength and bonding strength of the interface retarding concrete specimens meet the design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a sample state diagram of the test piece of Example 1 after flushing;

[0040] Figure 2 This is the sample state diagram of the specimen of comparative example 1 after flushing;

[0041] Figure 3 This is a sample state diagram of the test piece of Example 2 before flushing;

[0042] Figure 4 This is a sample state diagram of the specimen in Example 2 after flushing. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in conjunction with the accompanying drawings. Figures 1 to 4 The technical scheme of the present invention is clearly and completely described in detail with specific embodiments.

[0044] An embodiment of the present invention provides a method for preparing an interface slow-setting concrete specimen, comprising the following steps:

[0045] Step 1, preparing slow-setting functional paper: spraying a water-based surface retarder on absorbent paper and allowing the paper to dry naturally.

[0046] Step 2: Select at least one of the horizontal interface and the vertical interface to form a slow-setting layer.

[0047] If you select the horizontal interface, execute:

[0048] S21a, placing the concrete mixture into the test mold and vibrating it to make it dense;

[0049] S22a, affix slow-setting functional paper to the top surface of the concrete and cover it with plastic film, and use the concrete moisture to activate the slow-setting function. The function of the plastic film is to reduce the evaporation of moisture in the concrete.

[0050] If the vertical interface is selected, then execute:

[0051] S21b. Atomize and spray water on the surface of the side wall of the test mold;

[0052] S22b. Attach the retarding function paper to the wet side wall, and spray the mold release agent on the other side walls that do not require retarding;

[0053] S23b. Load the concrete mixture into the test mold and vibrate it until it is dense.

[0054] When a retarding layer is formed on both the horizontal interface and the vertical interface simultaneously, the vertical interface is processed first and then the horizontal interface is processed.

[0055] Step 3. Demold after curing to obtain an interface-retarded concrete specimen. Specifically, the curing conditions are a temperature of 25 ± 5 °C and a placement time of 24 ± 2 h.

[0056] Specifically, the water absorption rate of the blotting paper in Step 1 is ≥ 2.5 g / m 2 , and the grammage is 4.5 g / m 2 ~10.0 g / m 2 ; the blotting paper is one of toilet paper, tissue paper, hand wipes, and kitchen paper.

[0057] A water absorption rate ≥ 2.5 g / m² can ensure that the paper fully absorbs the water-based retarding agent, avoid liquid loss or uneven distribution after spraying, and guarantee the uniformity and effectiveness of the retarding function paper. Lower limit of grammage (4.5 g / m²): Prevent the paper from being torn or deformed during processing (spraying, air drying), and ensure process stability. Upper limit of grammage (10.0 g / m²): Avoid a decrease in flexibility due to too thick paper, which affects the actual application scenarios (such as conforming to curved surfaces or the usage requirements of folding). Specify common high water-absorbing materials such as toilet paper and tissue paper. Due to their loose fiber structure and high porosity, they can quickly adsorb the retarding agent and lock it evenly, while ensuring the stable retention of the retarding agent after air drying and avoiding functional failure.

[0058] Specifically, the water-based surface retarding agent contains at least one functional component selected from the following categories: hydroxycarboxylic acids and their salts (such as citric acid, tartaric acid, sodium citrate, potassium citrate, sodium gluconate, sodium potassium tartrate); phosphates (such as sodium tripolyphosphate, sodium hexametaphosphate); sulfonates (such as sodium lignosulfonate, sodium naphthalene sulfonate); carbohydrate compounds (such as glucose, sucrose); boric acid and its salts (such as boric acid, borax); polyols (such as sorbitol, mannitol).

[0059] The spraying amount range of the water-based surface retarding agent corresponding to the area of the blotting paper is 125 g / m 2 ~275 g / m 2 .

[0060] Specifically, the concrete mixture includes: cement, coarse aggregate, and fine aggregate. An appropriate cement content ensures sufficient hydration products to form a dense structure, providing the necessary compressive strength and durability, while avoiding temperature cracks caused by excessive heat of hydration due to excessive cement. Coarse aggregate provides strength as a skeleton, and fine aggregate fills the voids. The combination of the two reduces the porosity, improves the compactness of the concrete, and enhances the impermeability and frost resistance. The cement is Portland cement, ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, composite Portland cement, etc. It is preferred to use Portland cement, which can provide high early strength and is suitable for most engineering scenarios, but the fast hydration rate may limit the construction time.

[0061] The particle size of the coarse aggregate is 5 - 20 mm, and the fineness modulus of the fine aggregate is 2.3 - 3.0.

[0062] The coarse aggregate is selected with a particle size range of 5 - 20 mm. This particle size range covers continuous grading (such as 5 - 10 mm, 10 - 20 mm), which can effectively reduce the void ratio between aggregates (usually controlled at 35 - 40%), reduce the demand for cement paste, improve the compactness and compressive strength of the concrete (with a 5 - 10% increase). It matches the conventional test mold size (150 mm cube), avoiding the damage of the retarder layer caused by large - sized aggregates (>20 mm) touching the side wall of the test mold during vibration, and at the same time preventing too fine aggregates (<5 mm) from increasing the specific surface area and affecting the migration efficiency of water to the retarder - functional paper. Medium - sized aggregates can maintain good workability within the slump range of 70 - 150 mm, ensuring that the paste fully wraps the aggregates during the vibration compaction process and reducing pore defects at the interface. The maximum particle size of the coarse aggregate ≤20 mm can reduce the protrusion of the aggregates on the forming surface after vibration (height difference ≤0.5 mm), ensure the full contact between the retarder - functional paper and the concrete, and avoid local retardation failure;

[0063] The synergistic effect of the fine aggregate with a fineness modulus of 2.3 - 3.0 has the following characteristics: The fineness modulus of 2.3 - 3.0 corresponds to the medium - sand range (Zone II sand), and its particle size distribution can effectively fill the gaps between coarse aggregates (the void ratio is reduced to 20 - 25%). While reducing the demand for paste, it enhances the denseness of the microstructure in the interfacial transition zone; Fine particles (the proportion of 0.15 - 0.6 mm ≥15%) can form a continuous paste film, improving the bonding strength between the coarse aggregate and the cement matrix, and preventing the peeling of the interfacial retarder layer due to stress concentration during demolding; The moderate sand ratio (30 - 45%) combined with the fineness modulus can balance the water retention of the concrete and the water - absorption activation efficiency of the retarder - functional paper, ensuring the uniform diffusion of the retarder at the interface. The capillary pore structure formed by the fineness modulus of 2.3 - 3.0 of the fine aggregate can adjust the penetration depth of water carrying the retarder into the concrete surface layer (controlled at 1 - 3 mm), forming an effective retarder layer while avoiding excessive penetration and affecting the strength of the bulk.

[0064] C50 concrete is a high-strength concrete with a standard cube compressive strength of 50 MPa at 28 days. The cement for C50 concrete is ordinary Portland cement, and the coarse aggregate is hard and clean crushed stone or gravel with a particle size of 5 - 20 mm (good gradation is required, and the maximum particle size ≤ 25 mm). The fine aggregate is medium-coarse river sand or manufactured sand with a fineness modulus of 2.3 - 3.0 and a mud content ≤ 3%. The proportion of the coarse aggregate is about 60 - 70%, and the fine aggregate is 30 - 40% (the sand ratio is usually 28 - 35%).

[0065] Next, the setting retardation effect of the setting retardation functional paper is demonstrated through experimental results.

[0066] Example 1:

[0067] On 1 square meter of toilet paper, 250 g of aqueous surface setting retarder, specifically sucrose, was evenly sprayed, and then naturally air-dried to obtain 1 square meter of setting retardation functional paper.

[0068] Stir C50 concrete, pour the concrete mixture into a mold of 200 mm × 100 mm × 50 mm, then cut the setting retardation functional paper into an area of 200 mm × 100 mm, lay it flat on the concrete surface, and cover it with a plastic film to form a setting retardation layer at the horizontal interface.

[0069] Let it stand at room temperature for 24 h, and the curing condition is a temperature of 25°C to obtain an interface setting retardation concrete specimen.

[0070] Wash the surface of the setting retardation functional paper with a high-pressure water gun to obtain a rough concrete interface. As Figure 1 shown.

[0071] Comparative Example 1:

[0072] Stir C50 concrete, pour the concrete mixture into a mold of 200 mm × 100 mm × 50 mm, and spray the aqueous surface setting retarder sucrose on the concrete surface to form a setting retardation layer at the horizontal interface.

[0073] Let it stand at room temperature for 24 h, and the curing condition is a temperature of 5°C to obtain an interface setting retardation concrete specimen.

[0074] Wash the surface of the setting retardation functional paper with a high-pressure water gun to obtain a rough concrete interface. As Figure 2 shown.

[0075] From the comparison between Example 1 and Comparative Example 1, the surface of the interface setting retardation concrete specimen prepared by the method of the present invention is rough and evenly distributed, achieving a good setting retardation effect. In Comparative Example 1, the aqueous surface setting retarder was directly sprayed on the concrete surface, resulting in uneven distribution of the aqueous surface setting retarder on the concrete surface and obvious protrusions on the surface of the concrete specimen.

[0076] Regarding the problem of uneven distribution caused by the migration of traditional water-based surface retarders to low-lying areas due to gravity at non-absolutely horizontal interfaces, the interface is fixedly covered with a retardant functional paper. Utilizing the slow-release property of the retardant in the paper substrate, the retardant components act uniformly on the entire target interface. After the retardant functional paper is attached to the construction surface, its physical barrier effect can prevent the excessive enrichment of the retardant in cracks or depressions, ensuring the consistency of the thickness and roughness of the interface retardant layer, and completely eliminating the retardant failure or local bonding weakness caused by the level deviation.

[0077] Example 2:

[0078] On 1 square meter of toilet paper, 250 g of water-based surface retarder is evenly sprayed. The water-based surface retarder is specifically sucrose, and then it is naturally air-dried to obtain 1 square meter of retardant functional paper.

[0079] On the side surface of a mold with dimensions of 150 mm × 150 mm × 150 mm, the side wall surface of the mold is atomized and sprayed with water. Then, the retardant functional paper is cut into an area of 150 mm × 150 mm, and the retardant functional paper is attached to the wet side wall. The water will fix the retardant functional paper on the side of the mold. Stir C50 concrete, pour the concrete mixture into the mold, vibrate it densely, and then place it at 25°C and let it stand for 24 h. Use a high-pressure water gun to flush the surface where the retardant functional paper acts to obtain a rough concrete interface. Figure 3 This is a sample state diagram before the specimen is flushed. Figure 4 This is a sample state diagram after the specimen is flushed.

[0080] Regarding the defect that the paste retarder contaminates the bottom concrete due to its own weight when applied to the side surface of the formwork, the retardant functional paper is used to replace the traditional paste material. By pre-cutting and pasting the retardant functional paper on the inner side of the mold, using the solid loading capacity of the paper substrate for the retardant, the retardant is prevented from detaching from the target interface under the action of gravity. During the pouring process, the retardant functional paper closely adheres to the formwork under the lateral pressure of the concrete, and the retardant only acts on the vertical interface area, avoiding the accidental retardation of the bottom concrete and fundamentally eliminating the structural defects caused by dripping.

[0081] Next, an experimental study is conducted on the spraying amount of the water-based surface retarder corresponding to the area of the absorbent paper.

[0082] Experiment 1:

[0083] Select absorbent paper with a water absorption rate of 4.0 g / m 2 and a grammage of 4.5 g / m 2For the toilet paper, sucrose is selected as the water-based surface retarder. After spraying it on the toilet paper in different dosages and then air-drying it naturally in a 20°C room, specimens are formed according to the requirements of JC / T 2624~2021 "Concrete Surface Retarder" and the etching depth is tested to achieve a quantitative effect. The spraying amount range of the water-based surface retarder corresponding to the area of the absorbent paper is 100 g / m 2 ~300 g / m 2 . The corresponding relationship between the specific spraying amount of the water-based surface retarder and the performance is shown in Table 1.

[0084] Table 1

[0085]

[0086] It can be seen from the data that when the spraying amount is less than 125 g / m 2 , the retarder component in the retardation functional paper is relatively low. After encountering the mixing water in the concrete, the contact range with the cementitious material in the concrete is effective, and the etching depth obtained after flushing is relatively shallow, and the effect is not good. When the spraying amount is greater than 250 g / m 2 , the air-drying time is prolonged, it is easy to flush, and the performance tends to be stable, indicating that the adsorption and release mechanism of sucrose on the toilet paper carrier reaches equilibrium. The comprehensive performance is optimal when the spraying amount of sucrose on the toilet paper is 250~275 g / m², and the best technical effect can be achieved (etching depth ≥ 3.2 mm, flushing time ≤ 0.5 min), meeting the requirements of the JC / T 2624-2021 standard and being applicable to the refined treatment needs of the concrete surface.

[0087] Experiment 2:

[0088] Replace the sucrose in Experiment 1 with sodium citrate, and other conditions are exactly the same as those in Experiment 1. The corresponding relationship between the specific spraying amount of the water-based surface retarder and the performance is shown in Table 2.

[0089] Table 2

[0090]

[0091] It can be seen from the data that the changing trends of the air-drying time and the flushing time after 24 h corresponding to spraying sodium citrate and sucrose in Experiment 1 are the same. However, compared with the data in Experiment 1, it is found that sodium citrate dries faster: at the same spraying amount, the air-drying time of sodium citrate is 10%~15% shorter than that of sucrose. Compared with sucrose, sodium citrate has a higher retardation efficiency, and the required spraying amount to reach the same etching depth (3.0 mm) is lower. The flushing time of sodium citrate stabilizes below 0.8 min at 250 g / m², while sucrose reaches 0.5 min only at 250 g / m². The comprehensive performance is optimal when the spraying amount of sodium citrate on the toilet paper is 200~250 g / m², and the economy and performance can be taken into account.

[0092] Experiment 3:

[0093] Replace the sucrose in Experiment 1 with boric acid, and keep other conditions exactly the same as those in Experiment 1. The corresponding relationship between the spraying amount of the aqueous surface retarder and the performance is shown in Table 3.

[0094] Table 3

[0095]

[0096] It can be seen from the data that the changing trends of the air-drying time and the scouring time after 24 h corresponding to Experiment 3, Experiment 1, and Experiment 2 are the same. However, by comparing with the data of Experiment 1 and Experiment 2, it is found that the air-drying time of boric acid is significantly lower than that of sucrose and sodium citrate. However, the retarding efficiency of boric acid is relatively low, and the spraying amount ≥ 275 g / m² is required to reach the target etching depth (≥ 3.0 mm). No obvious overloading phenomenon is observed: when the spraying amount is 300 g / m², the etching depth still increases steadily.

[0097] The effects of the present invention:

[0098] 1. Based on a mature aqueous surface retarder system, it is loaded on the surface of the absorbent paper through a quantitative spraying process and forms a retardation functional paper after air-drying and curing. Among them, the porosity and water absorption of the absorbent paper are adapted to the penetration characteristics of the retarder solution to ensure that the retarder is evenly distributed and fixed inside the absorbent paper; through the precise metering control of the spraying equipment, the consistency of the application amount of the retarder per unit area is realized, thereby overcoming the dosage deviation problem caused by fluidity in the traditional spraying process.

[0099] 2. The retardation functional paper has the physical cutting characteristics and can be customized and cut in terms of size and shape according to the construction interface form (such as horizontal joint surface, vertical joint surface or special-shaped structure surface) to accurately define the boundary of the retardation action area. By fixing the cut functional paper to the template or interface, the diffusion or migration of the retarder in the non-target area can be avoided, which is especially suitable for the fine treatment of complex structure interfaces and small-size joint surfaces.

[0100] 3. The retardation functional paper is used in coordination with a specific component concrete. During the pouring process, the concrete forms a directional extrusion on the retardation functional paper instead of shear damage, ensuring that the retardation functional paper remains intact in the interface area and continuously releases the retardation component, and finally forms a uniform rough interface transition layer, and the compressive strength and bonding strength of the interface retardation concrete specimens meet the design requirements.

[0101] This technology uses the retarding functional paper as a medium to systematically solve two major industry problems, namely, the migration of retarding agents at the horizontal interface and the dripping of retarding agents at the vertical interface, achieving the standardization, refinement, and high efficiency of the treatment of the interface between new and old concrete. At the same time, through the adaptable concrete mix ratio, the structural damage of the retarding functional paper during the pouring process is avoided, and the bond strength between the new and old concrete interfaces and the controllability of the construction quality are significantly improved.

[0102] Finally, it should be noted that the above-mentioned embodiments are only specific embodiments of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments or easily conceive of changes, or perform equivalent replacements for some of the technical features; and these modifications, changes, or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A preparation method for an interface retarding concrete specimen, characterized in that, It includes the following steps: Step 1, prepare the retarding functional paper: spray the aqueous surface retarding agent on the absorbent paper and air-dry it naturally; Step 2, select at least one of the horizontal interface or the vertical interface to form a retarding layer: If the horizontal interface is selected, then execute: S21a, fill the concrete mixture into the test mold and vibrate it densely; S22a, attach the retarding functional paper to the top surface of the formed concrete and cover it with a plastic film to activate the retarding function by using the moisture of the concrete; If the vertical interface is selected, then execute: S21b, spray the side wall surface of the test mold with atomized water; S22b, attach the retarding functional paper to the wet side wall and spray the release agent on the other side walls that do not need retarding; S23b, fill the concrete mixture into the test mold and vibrate it densely; Step 3, demold after curing to obtain the interface retarding concrete specimen.

2. The preparation method of the interfacial retarding concrete specimen according to claim 1, wherein The water absorption rate of the blotting paper ≥ 2.5 g / m 2 , and the grammage is 4.5 g / m 2 ~10.0 g / m 2 ; The absorbent paper is one of toilet paper, tissue paper, hand towel paper, and kitchen paper.

3. The preparation method of the interfacial retarding concrete specimen according to claim 2, characterized in that, The spraying amount of the water-based surface retarder corresponding to the area of the absorbent paper ranges from 125 to 275 g / m 2 .

4. The method for preparing an interface retarding concrete specimen according to claim 3, wherein The aqueous surface retarding agent contains at least one functional component selected from the following categories: hydroxycarboxylic acids and their salts, phosphates, sulfonates, carbohydrate compounds, boric acid and its salts, polyols.

5. The preparation method of the interface retarded concrete specimen according to claim 4, characterized in that, The absorbent paper is toilet paper, and the water absorption rate of the toilet paper is 4.0 g / m 2 and the grammage is 4.5 g / m 2 ; The aqueous surface retarding agent is sucrose; The spraying amount range of the aqueous surface retarding agent corresponding to the area of the absorbent paper is 250 - 275 g / m².

6. The preparation method of the interface retarding concrete specimen according to claim 4, characterized in that, The absorbent paper is toilet paper, and the water absorption rate of the toilet paper is 4.0 g / m 2 and the grammage is 4.5 g / m 2 ; The aqueous surface retarding agent is sodium citrate; The spraying amount range of the aqueous surface retarding agent corresponding to the area of the absorbent paper is 200 - 250 g / m².

7. The preparation method of the interfacial retarding concrete specimen according to claim 1, characterized in that, When forming the retarding layer on both the horizontal interface and the vertical interface simultaneously, the vertical interface treatment is carried out first and then the horizontal interface treatment.

8. The preparation method of the interfacial retarding concrete specimen according to claim 1, characterized in that, The curing condition in Step 3 is 25 ± 5 °C and the placement time is 24 ± 2 h.

9. The preparation method of the interface retarding concrete specimen according to claim 1, wherein, The concrete mixture includes: cement, coarse aggregate, and fine aggregate; The cement is one or more of portland cement, ordinary portland cement, slag portland cement, pozzolanic portland cement, fly ash portland cement, and composite portland cement.

10. The preparation method of the interfacial retarded concrete specimen according to claim 9, characterized in that, The particle size of the coarse aggregate is 5 - 20 mm and the fineness modulus of the fine aggregate is 2.3 - 3.0.

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