Concrete damage evaluation method for hydraulic engineering under impact and abrasion conditions

Abstract

The invention relates to the technical field of durability testing of hydraulic concrete, and discloses a concrete damage evaluation method for a hydraulic engineering under an impact wear condition. A test piece containing a plurality of cubes is formed through one-time pouring of a test piece forming mold, the test pieces can be combined into a cylindrical test piece and can be directly placed into an existing underwater steel ball impact and abrasion tester for testing, and in the impact and abrasion test, the four cube test pieces are integrated into an integral cylindrical test piece; at the moment, the cube test piece is located in the whole cylinder test piece, so that the damage degree of impact wear to the concrete internal structure can be better evaluated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic concrete durability testing, for example to a method for evaluating concrete damage under scouring conditions for hydraulic engineering. BACKGROUND

[0002] During the operation of the water discharge structure, the sand-carrying water flow exerts a coupling effect of scouring and impact on the flow surface, leading to the deterioration of the performance of the concrete material and the peeling and falling off of the surface layer. In order to meet the design, construction and safe operation requirements of the water discharge structure, it is necessary to systematically carry out indoor test research on the anti-scouring performance of the concrete.

[0003] The existing test methods for the anti-scouring performance of concrete mainly include the high-speed ring method, the rotating jet method, the underwater steel ball method and the wind sand gun method, among which the underwater steel ball method is the most widely used. The “Hydraulic Concrete Test Regulations” (DL / T 5150-2017) provides that this method uses a cylindrical standard test piece with a diameter of 300 mm and a height of 100 mm, and three parallel test pieces are set for each group. After 72 h of continuous scouring, the mass loss is measured and the anti-scouring strength is calculated.

[0004] About 70% of the existing concrete dams in China suffer from different degrees of water flow scouring damage during operation, and the erosion problem of large and medium-sized hydropower stations on the main stream of the Yellow River is particularly prominent. In-depth study of the influence mechanism of scouring on the macroscopic performance and microstructure of concrete is of great engineering significance to ensure the long-term safe operation of the water discharge structure.

[0005] In view of the fact that the concrete structure of hydraulic engineering is long-term subjected to the coupling effect of water flow scouring and sediment abrasion, the surface layer and the internal structure will produce progressive damage, which directly affects the safety and service life of the engineering structure. The current evaluation of the scouring damage of the concrete of hydraulic engineering mainly focuses on the macroscopic characterization of the surface damage, and lacks quantitative evaluation means for the damage degree of the internal material.

[0006] The existing test method has technical limitations such as large test piece volume, heavy mass, and complicated operation, and the test results can only represent the surface peeling degree of the concrete, and it is difficult to fully reflect the internal damage evolution law of the concrete under the scouring action. In actual service conditions, the sand-carrying water flow not only causes the loss of the surface layer material, but also causes the accumulation of internal microstructure damage of the concrete, resulting in systematic deterioration of its macroscopic mechanical properties. Therefore, it is urgent to develop a special test piece forming mold and test method that can comprehensively evaluate the surface damage and internal damage characteristics of the concrete under the scouring conditions.

[0007] In summary, the prior art has the following main limitations: first, the current evaluation of concrete damage in hydraulic engineering focuses on the quantification of surface damage, and there is a lack of effective evaluation methods for the degree of internal damage of the material; second, the existing test methods are difficult to simultaneously obtain the correlation between the loss of concrete surface quality and the evolution of internal strength during the erosion process, and cannot establish a quantitative mapping relationship between erosion time and internal damage degree of concrete. In addition, the conventional test scheme usually needs to prepare multiple groups of test pieces to carry out erosion test and strength test respectively, which leads to increased test error and reduced accuracy of evaluation results. Therefore, it is urgent to establish an evaluation method that can represent the internal damage of concrete in hydraulic engineering under erosion conditions, to provide scientific basis for the design optimization, service state evaluation and repair and reinforcement of concrete structures.

[0008] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0009] In order to have a basic understanding of some aspects of the disclosed embodiments, the following is a simple summary. The summary is not a general review, nor is it intended to determine the key / important components or delineate the scope of protection of these embodiments, but as a prelude to the detailed description that follows.

[0010] The concrete damage evaluation method under erosion conditions for hydraulic engineering provided by the embodiments of the present disclosure solves the problem of how to evaluate the internal damage of concrete in hydraulic engineering under erosion conditions.

[0011] In some embodiments, the concrete damage evaluation method under erosion conditions for hydraulic engineering comprises:

[0012] Assembling a test piece forming mold, wherein the test piece forming mold is a cylindrical outer cylinder with four cubic inner cylinders;

[0013] Pouring the same concrete as the actual engineering mix ratio into the test piece forming mold to prepare a cylindrical test piece containing four cubic test pieces, and using the same concrete mix ratio to prepare a cuboid test piece, wherein the length and width of the cuboid test piece are the same as those of the cubic test piece, and the height of the cuboid test piece is less than that of the cubic test piece;

[0014] Testing the compressive strength of the cubic test piece and the cuboid test piece respectively, establishing a conversion relationship between the compressive strength of test pieces of different sizes, and obtaining a correction coefficient K;

[0015] Weighing to obtain the weight of a single cubic test piece before erosion test as m o , using the underwater steel ball method to carry out erosion test on the cylindrical test piece, and weighing to obtain the weight of a single cubic test piece as m tThe impact resistance is calculated, multiple impact tests are performed with different times, and the relationship between the impact time and the impact resistance is established.

[0016] The cuboid specimen after the impact test is cut into the same size as the cuboid specimen, and the compressive strength is tested, and the relationship between the impact time and the compressive strength is established to evaluate the damage of the impact to the interior of the concrete.

[0017] Optionally, the diameter of the cylindrical specimen is 300 mm, the height is 100 mm, the length of the cuboid specimen is 100 mm, the width is 100 mm, and the height is 100 mm, and the length of the cuboid specimen is 100 mm, the width is 100 mm, and the height is 70 mm.

[0018] Optionally, the correction coefficient is calculated according to the following formula:

[0019]

[0020] In the formula, K is the correction coefficient of the compressive strength, f1 is the average value of the compressive strength of the 100 mm cuboid specimen, and the unit is MPa, f 70 is the average value of the compressive strength of the cuboid specimen with a height of 70 mm, and the unit is MPa.

[0021] Optionally, the impact resistance is calculated according to the following formula:

[0022]

[0023] In the formula, f a is the impact resistance of the concrete, the unit is h / (kg / ㎡), t is the impact time, the unit is h, A is the impact area, the unit is ㎡, m0 is the mass of the single specimen before impact, the unit is kg, and m t is the mass of the single specimen after impact for t hours, the unit is kg.

[0024] Optionally, the compressive strength of the concrete after impact is calculated according to the following formula:

[0025] f t = K x f t70

[0026] In the formula, f t is the compressive strength of the concrete after impact, the unit is MPa, K is the correction coefficient of the compressive strength, f t70 is the compressive strength of the concrete specimen after impact for t hours and cutting, and the unit is MPa.

[0027] Optionally, the mass m o is obtained by weighing before the cuboid specimen is placed in water for a first set time and taken out, and the surface water is wiped off and weighed.

[0028] Optionally, the first setting time is equal to the scouring time of the cylinder specimen in the underwater steel ball scouring test.

[0029] Optionally, the specimen forming mold comprises a cylindrical outer cylinder, a square inner cylinder, a base plate and a handle. The cylindrical outer cylinder adopts a split structure, formed by two symmetrical half-circular rings through bolts to form a complete circular ring cylinder structure; the square inner cylinder is an integral structure, containing four square cavities, and the bottom is provided with a positioning flange; the base plate surface has a cylindrical boss, which can be embedded with the cylindrical outer cylinder, and the boss surface is provided with a guide groove which can be embedded with the positioning flange of the square inner cylinder; the handle is arranged on both sides of the base plate.

[0030] Optionally, the preparation of the cylinder specimen comprises:

[0031] The specimen forming mold is coated with a release agent or butter, and the coating positions include the inner surface of the cylindrical outer cylinder, the outer surface of the square inner cylinder, the inner surface and the upper surface of the base plate. The concrete is poured into the specimen forming mold, vibrated and compacted, demolded after initial setting of the concrete and placed in a curing box for curing for 28 days.

[0032] Optionally, the assembly of the specimen forming mold comprises:

[0033] The positioning flange at the bottom of the square inner cylinder is inserted into the guide groove on the surface of the base plate, the cylindrical outer cylinder is placed on the base plate, abutting against the outside of the cylindrical boss, and fastened with bolts.

[0034] The concrete damage evaluation method under scouring conditions for hydraulic engineering provided by the embodiments of the present disclosure can achieve the following technical effects: the specimen forming mold can form a specimen containing multiple squares in a single pouring, the specimen can be combined into a cylinder specimen, and the specimen can be directly placed into an existing underwater steel ball scouring tester for testing; at the same time, the influence of different sizes of the specimen after scouring on the compressive strength is corrected by introducing a correction coefficient K, effectively eliminating the test error caused by the size difference due to specimen cutting, and improving the comparability and accuracy of the compressive strength data. The error caused by different water contents of the specimen is eliminated by immersion treatment, and the accuracy of the quality loss calculation is improved. Four square concrete specimens are formed synchronously in a single pouring, saving materials and significantly improving the test efficiency; the formed square specimens can be tested for mechanical properties, and the damage caused by scouring to the mechanical properties of the concrete can be evaluated. In the scouring test, the four square specimens are integrated into a whole cylinder specimen, and at this time the square specimens are located inside the whole cylinder specimen, so that the damage degree of the internal structure of the concrete caused by scouring can be better evaluated, and an evaluation method for the internal damage of the concrete under scouring conditions in hydraulic engineering can be represented, providing a scientific basis for the design optimization, service state evaluation and repair and reinforcement of the concrete structure.

[0035] The foregoing general description and the following description are only exemplary and explanatory, and are not intended to limit the present application. Attached Figure Description

[0036] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein:

[0037] Figure 1 This is a schematic diagram of the overall structure of a specimen molding die provided in an embodiment of this disclosure;

[0038] Figure 2 This is an exploded view of a specimen molding die provided in an embodiment of this disclosure;

[0039] Figure 3 This is a top view of a specimen molding die provided in an embodiment of this disclosure;

[0040] Figure 4 This is a left view of a specimen molding die provided in an embodiment of this disclosure;

[0041] Figure 5 This is a front view of a specimen molding die provided in an embodiment of this disclosure;

[0042] Figure 6 This is a cross-sectional view of a specimen molding die from one angle provided in an embodiment of this disclosure;

[0043] Figure 7 This is a cross-sectional view of the specimen molding die from another angle provided in an embodiment of this disclosure;

[0044] Figure 8 This is a schematic diagram of cutting a cube specimen according to an embodiment of this disclosure;

[0045] Figure 9 This is a schematic diagram of a method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering, provided in an embodiment of this disclosure.

[0046] Figure label:

[0047] 1. Cylindrical outer cylinder; 2. Cube inner cylinder; 3. Base; 4. Handle. Detailed Implementation

[0048] In order to enable a more detailed understanding of the features and technical content of the embodiments of the present disclosure, the implementation of the embodiments of the present disclosure is described in detail below, and the accompanying drawings are used for reference only and do not limit the embodiments of the present disclosure. In the following technical description, in order to facilitate explanation, a plurality of details are provided to provide a full understanding of the disclosed embodiments. However, one or more embodiments can still be implemented without these details. In other cases, well-known structures and devices can be simplified to facilitate the drawings.

[0049] The terms "first", "second", and the like in the specification and claims of the embodiments of the present disclosure and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present disclosure described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion.

[0050] In the embodiments of the present disclosure, the terms "upper", "lower", "inner", "middle", "outer", "front", "back", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the embodiments of the present disclosure and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to indicating the orientation or positional relationship, the above-mentioned terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain attachment relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the embodiments of the present disclosure can be understood according to the specific circumstances.

[0051] In addition, the terms "set", "connected", "fixed" should be broadly understood. For example, "connected" can be fixedly connected, detachably connected, or integrally configured; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present disclosure can be understood according to the specific circumstances.

[0052] Unless otherwise specified, the term "a plurality of" means two or more.

[0053] In the embodiments of the present disclosure, the character " / " represents an "or" relationship between the objects before and after it. For example, A / B represents: A or B.

[0054] The term "and / or" is a description of the association between objects, which means that there can be three relationships. For example, A and / or B, which means: A or B, or, A and B, the three relationships.

[0055] It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0056] In combination with Figure 1 As shown in the drawings, the present disclosure provides a method for evaluating the damage of concrete under the impact of water conservancy projects, which comprises the following steps:

[0057] S01, assembling a test piece forming mold, wherein the test piece forming mold is a cylindrical outer cylinder with four cubic inner cylinders;

[0058] S02, pouring the same concrete as the actual project into the test piece forming mold to prepare a cylindrical test piece containing four cubic test pieces, and using the same concrete to prepare a cuboid test piece, wherein the length and width of the cuboid test piece are the same as those of the cubic test piece, and the height of the cuboid test piece is less than that of the cubic test piece;

[0059] S03, respectively testing the compressive strength of the cubic test piece and the cuboid test piece, establishing the conversion relationship between the compressive strength of test pieces of different sizes, and obtaining the correction coefficient K;

[0060] S04, weighing to obtain the weight of a single cubic test piece before impact test as m o , using the underwater steel ball method to conduct impact test on the cylindrical test piece, weighing to obtain the weight of a single cubic test piece as m t , calculating the impact resistance, conducting multiple impact tests at different times, and establishing the relationship between the impact time and the impact resistance;

[0061] S05, cutting the cubic test piece after the impact test into the same size as the cuboid test piece, and testing the compressive strength, establishing the relationship between the impact time and the compressive strength, and using it to evaluate the damage of the impact on the internal concrete.

[0062] The method for evaluating the damage of concrete under the condition of water conservancy engineering impact and abrasion provided by the embodiments of the present disclosure can form a test piece containing multiple cubes through single pouring of a test piece forming mold. The test piece can be combined into a cylindrical test piece and can be directly placed into an existing underwater steel ball impact and abrasion tester for testing. Meanwhile, a correction coefficient K is introduced to correct the influence of different sizes of the test piece after impact and abrasion on the compressive strength, effectively eliminating the test error caused by the size difference due to cutting of the test piece, and improving the comparability and accuracy of the compressive strength data. The error caused by different water contents of the test piece is eliminated through immersion treatment, and the accuracy of the quality loss calculation is improved. Four cubic concrete test pieces are formed synchronously in single pouring, which saves materials and significantly improves the test efficiency. The formed cubic test pieces can be tested for mechanical properties, and the damage caused by impact and abrasion to the mechanical properties of concrete can be evaluated. In the impact and abrasion test, the four cubic test pieces are integrated into a whole cylindrical test piece. At this time, the cubic test pieces are located inside the whole cylindrical test piece, so the damage degree of impact and abrasion to the internal structure of concrete can be better evaluated, and the evaluation method of internal damage of concrete under the condition of impact and abrasion in water conservancy engineering can be characterized, which provides a scientific basis for design optimization, service state evaluation and repair and reinforcement of concrete structures

[0063] Optionally, the diameter of the cylindrical test piece is 300mm and the height is 100mm, the length of the cubic test piece is 100mm, the width is 100mm and the height is 100mm, and the length of the cuboid test piece is 100mm, the width is 100mm and the height is 70mm. In this way, the four cubic test pieces with a side length of 100mm are arranged in a cross shape to fill the cylindrical space with a diameter of 300mm and a height of 100mm, ensuring that the whole structure is uniformly stressed. During the impact and abrasion test, the continuous impact and friction of the steel ball on the upper surface of the cylindrical test piece simulates the actual abrasion effect of the sediment on the concrete in the water flow, and the internal cubic test piece avoids the edge effect interference, and more truly reflects the damage evolution law of the internal region of the concrete in the water conservancy engineering.

[0064] Optionally, the correction coefficient is calculated as follows:

[0065]

[0066] In the formula, K is the correction coefficient of compressive strength; f1 is the average value of the compressive strength of the 100mm cubic test piece, with the unit of MPa; f 70 f2 is the average value of the compressive strength of the cuboid test piece with a height of 70mm, with the unit of MPa. In this way, the correction coefficient K is determined by introducing the ratio of the compressive strength of the cuboid test piece with a height of 70mm to the standard cubic test piece, which can effectively reflect the influence of size effect on the strength test results, and further improve the equivalence and comparability of the compressive strength data between test pieces of different sizes.

[0067] Optionally, the impact and abrasion resistance is calculated as follows:

[0068]

[0069] f = f0- f1 a is the anti-abrasion strength of concrete, unit: h / (kg / m2); t is the abrasion time, unit: h; A is the abrasion area, unit: m2; m0is the mass of a single test piece before abrasion, unit: kg; m t is the mass of a single test piece after abrasion t hours, unit: kg. In this way, the anti-abrasion performance of concrete is quantified by the ratio of mass loss per unit area to abrasion time, which can intuitively reflect the durability difference of the material under specific abrasion conditions.

[0070] Optionally, the compressive strength of the concrete after abrasion is calculated as follows:

[0071] f = f0- f1 t = Kxf1 t70

[0072] f = f0- f1 t is the compressive strength of the concrete after abrasion, unit: MPa, K is the compressive strength correction coefficient, f t70 is the compressive strength of the concrete test piece after abrasion t hours and cutting, unit: MPa. In this way, the measured strength of the test piece after abrasion is corrected by the correction coefficient K, eliminating the test deviation caused by the size effect. Thus, the compressive strength data of test pieces of different sizes before and after abrasion are comparable.

[0073] Wherein, when measuring the compressive strength, the surface of 100mm x 100mm is taken as the compression surface to conduct the compressive strength test, so as to ensure that the compression areas of the cubic test piece and the cuboid test piece are the same, and avoid inaccurate strength values due to the difference in force area.

[0074] Optionally, the mass m o is obtained by weighing before the cubic test piece is taken out after being soaked in water for a first set duration, and the surface water is wiped off and weighed. In this way, the mass measurement of the test piece can be ensured in the state of water saturation and surface dryness, so as to eliminate the mass measurement error caused by the difference in water content, and ensure the accuracy and comparability of the mass loss data before and after abrasion. This processing mode simulates the long-term immersion state of the concrete in the actual service environment of water conservancy projects, so that the test results are closer to the real working conditions, and the reliability of the anti-abrasion performance evaluation is improved.

[0075] Optionally, the soaking of the cubic test piece in water refers to the soaking of the entire cylindrical test piece containing four cubic test pieces in water. In this way, the consistency of the overall test piece in the water environment can be maintained, the uneven water absorption problem caused by the difference in boundary conditions when individual test pieces are soaked can be avoided, and the conditions of the cylindrical test piece receiving the impact and abrasion during the test are consistent, ensuring the uniformity and comparability of the material environment state during the test. After soaking is completed, the test piece is taken out as a whole, the surface moisture is wiped off one by one and immediately weighed to avoid the influence of water evaporation on the quality measurement. This operation can further improve the accuracy of the mass loss calculation before and after the impact and abrasion, and strengthen the reliability of the impact and abrasion resistance evaluation results.

[0076] Optionally, the first set time is equal to the impact and abrasion time of the cylindrical test piece using the underwater steel ball method. In this way, the water absorption state of the cubic test piece is consistent with the impact and abrasion test conditions, enhancing the comparability of the mass loss data between different test pieces and further unifying the control standard of the test parameters.

[0077] Optionally, the first set time can be a fixed value or the same as the impact and abrasion time of the impact and abrasion test. When the first set time is a fixed value, it is appropriate to take 24 hours to ensure that the test piece is fully water-absorbed to reach a saturated state. This fixed time is suitable for the case where the impact and abrasion time is short or the test period is limited, which can ensure the stability of the water content of the test piece.

[0078] In combination with Figures 2-7 As shown in the figure, optionally, the test piece forming mold used includes a cylindrical outer cylinder 1, a cubic inner cylinder 2, a bottom plate 3 and a handle 4. The cylindrical outer cylinder 1 adopts a split structure, which is formed into a complete ring cylinder structure by two symmetrical half rings through bolts; the cubic inner cylinder 2 is an integral structure, which contains four cubic chambers and is provided with a positioning flange at the bottom; the bottom plate 3 has a cylindrical boss on the surface, which can be embedded with the cylindrical outer cylinder 1, and the boss surface is provided with a guide groove which can be embedded with the positioning flange of the cubic inner cylinder 2; the handle 4 is arranged on both sides of the bottom plate 3. In this way, the modular design realizes the integrated forming of the cylindrical and cubic test pieces, effectively ensures the consistency of the forming conditions of different shaped test pieces in the pouring and curing process, and reduces the influence of mold deformation or assembly error on the forming quality. The mold structure is easy to disassemble and clean, which significantly improves the test efficiency and repeatability, saves materials and significantly improves the test efficiency.

[0079] Optionally, the preparation of the cylindrical test piece includes: applying release agent or butter to the test piece forming mold, the application position including the inner surface of the cylindrical outer cylinder 1, the outer surface of the square inner cylinder 2, the inner surface and the upper surface of the bottom plate 3, pouring the concrete into the test piece forming mold, vibrating and compacting, demolding after the initial setting of the concrete and placing it in the curing box for curing for 28 days. In this way, the integrity of the test piece corners and the surface without damage during demolding are ensured, and the stable development of the concrete performance is ensured through standard curing conditions. After the curing is completed, the test piece is taken out for size measurement and appearance inspection, and the test sample that does not meet the requirements is removed to ensure the accuracy of the test data. The concrete test piece cured for 28 days has reached the design strength stable period, the internal hydration reaction tends to be completed, and the mechanical properties are more representative. At this time, the impact and grinding test is carried out, which can truly reflect the durability performance of the material after long-term service. At the same time, the test piece structure after 28 days of curing is more dense, the surface hardness and the anti-washing capacity are stable, which is beneficial to reduce the test data dispersion and improve the scientific nature of the performance comparison of the test piece under different mix proportions or process conditions.

[0080] Optionally, all test pieces need to be placed in a standard environment for constant temperature and humidity for 24 hours before testing to balance the moisture content and further ensure the consistency of the test conditions. Then the test pieces are placed in the underwater steel ball impact grinder, and the impact grinding test is carried out according to the predetermined speed and time. After the impact grinding is completed, the test piece is immediately taken out, the surface spalling is washed with clean water and dried, the mass loss is weighed by using an electronic balance with an accuracy of 0.01 g, and the environmental parameters such as water temperature and speed fluctuation during the test process are recorded. By controlling the variable method, it is ensured that only the target factor is changed in each test, and the other conditions are completely the same, so as to accurately evaluate the influence of different mix proportions or curing process on the impact resistance of the concrete.

[0081] Optionally, the assembly of the test specimen forming mold includes: inserting the positioning flange at the bottom of the cuboid inner cylinder 2 into the surface guide groove of the base plate 3, placing the cylindrical outer cylinder 1 on the base plate 3, abutting the outer side of the cylindrical boss, and fastening with bolts. In this way, the assembly process of the overall test specimen forming mold is simple and convenient, and the coaxial centering of the cuboid inner cylinder 2 and the cylindrical outer cylinder 1 during the forming process can be ensured, avoiding uneven wall thickness or stress concentration due to eccentricity. After tightening the bolts, it is necessary to check whether the contact surfaces of each part are tightly fitted to prevent slurry leakage during pouring. The entire assembly process should be carried out on a flat table to ensure the geometric accuracy of the test specimen forming. After the mold is assembled, pouring should be carried out immediately to avoid contamination of the release agent or water evaporation affecting the interface state. Before pouring, the dimensions of each part of the mold should be checked again to ensure that they meet the design requirements. The concrete mixture should be evenly loaded into the mold in three layers, each layer is inserted and vibrated for 30 seconds on the vibrating table until the surface is covered with slurry and no obvious bubbles are discharged to ensure uniform density. After vibrating, the excess concrete is scraped off with a trowel and the surface is smoothed to avoid uneven or honeycomb surfaces. The entire operation process should be completed within 30 minutes to prevent premature setting and affect the molding quality. After pouring, immediately cover the plastic film to prevent water evaporation, and place it in a standard curing room for 24 hours. After demolding, the test specimen is numbered and placed in a curing box for further curing for 28 days.

[0082] Optionally, in S05, the cuboid test specimen after the impact test is cut to the same size as the cuboid test specimen, which means that the uneven end of the cuboid test specimen after the impact test is cut off to become a test specimen with dimensions of 100mmx100mmx70mm. Among them, after cutting, the upper and lower surfaces of the test specimen should be parallel and the perpendicularity error of the opposite surfaces should not exceed 0.5mm to ensure the accuracy and comparability of the subsequent compressive strength test

[0083] In some embodiments

[0084] In S01, the assembly of the test specimen forming mold includes: inserting the positioning flange at the bottom of the cuboid inner cylinder 2 into the surface guide groove of the base plate 3, placing the cylindrical outer cylinder 1 on the base plate 3, abutting the outer side of the cylindrical boss, and fastening with bolts;

[0085] In S02, the concrete mix ratio used when making the test specimen is shown in Table 1:

[0086] Table 1 Concrete mix ratio

[0087]

[0088] In S03, when testing the compressive strength of the cubic and rectangular specimens, the 100mm x 100mm face is taken as the compression face, the loading rate is 0.3MPa / s, and the compressive strength results are shown in Table 2. Multiple groups of specimens are tested to obtain the average value of the 100mm x 100mm x 100mm cubic compressive strength f 100 = 39.78MPa, the average value of the 70mm high rectangular compressive strength f 70 = 46.30MPa, and the correction coefficient K ≈ 0.859;

[0089] Table 2 Compressive strength

[0090]

[0091] In step S04, the weight of a single cubic specimen before the abrasion test is m o , which means that the entire cylindrical specimen containing four cubic specimens is placed in water for 48h, then taken out, the surface water is wiped off, and weighed. The weight of a single cubic specimen is m o = 2.486kg;

[0092] The cylindrical specimen is placed in a steel ball abrasion tester under water, and after 72h and 144h of abrasion, it is taken out, washed clean and the surface water is wiped off, and weighed. The weight of a single cubic specimen is m 72 = 2.329, m 144 = 1.875, and the abrasion resistance strength fa 72 = 4.586h / (kg / ㎡), fa 144 = 2.357h / (kg / ㎡);

[0093] The relationship between the abrasion time and the abrasion resistance strength is that multiple abrasion times and the abrasion resistance strength at that time are marked on the coordinate axes to form a curve graph, which intuitively reflects the relationship between the abrasion time and the abrasion resistance strength. This relationship mainly reflects the external damage of the concrete specimen. Multiple test results are taken to obtain the corresponding curve relationship, and the specific data is not shown here.

[0094] In S05, the cubic specimen after abrasion is cut into a 100mm x 100mm x 70mm concrete specimen (cutting is shown in Figure 9 ), and the 100mm x 100mm face is taken as the compression face to perform the compressive strength test. The loading rate is 0.3MPa / s. The average value of the compressive strength of the concrete specimen after 72h of abrasion is 45.23MPa, and the average value of the compressive strength of the concrete specimen after 144h of abrasion is 42.37MPa. After correction according to the coefficient K, f 72 = 38.85MPa, f 144= 36.40 MPa; by establishing a curve graph between the relationship of multiple groups of polishing time and corresponding compressive strength, the deterioration process of the internal structure of the concrete with the extension of the polishing time can be directly reflected, and accordingly the damage of the polishing to the internal concrete can be better evaluated. Similarly, the corresponding curve graph relationship can be obtained by taking multiple groups of test results, and the specific data is not shown here.

[0095] From the test results, it can be seen that the polishing not only causes the surface damage of the concrete, but also causes the internal damage, and the longer the polishing time, the faster the loss of the polishing resistance and the compressive strength of the concrete.

[0096] The above description and drawings sufficiently illustrate the embodiments of the present disclosure to enable one skilled in the art to practice them. Other embodiments can include structural and other changes. The embodiments represent only the possible variations. Individual components and functions are optional unless explicitly required, and the order of operations can be changed. Parts and features of some embodiments can be included or replaced by parts and features of other embodiments. The embodiments of the present disclosure are not limited to the structures that have been described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering, characterized in that, include: Assemble the specimen molding mold, wherein the specimen molding mold is a cylindrical outer cylinder with four cubic inner cylinders inside; Using concrete with the same mix proportion as the actual project, a cylindrical specimen containing four cube specimens was prepared by pouring it into a specimen molding mold. A cuboid specimen was also prepared using concrete with the same mix proportion. The length and width of the cuboid specimen were the same as those of the cube specimen, but the height of the cuboid specimen was less than that of the cube specimen. The compressive strength of cube and cuboid specimens were tested separately, and the conversion relationship of compressive strength between specimens of different sizes was established to obtain the correction factor K. The weight of a single cube before the impact test was obtained by weighing m. o The cylindrical specimen was subjected to a grinding test using the underwater steel ball method, and the weight of a single cube was obtained by weighing. t To calculate the impact and abrasion resistance, multiple impact and abrasion tests were conducted at different times to establish the relationship between impact and abrasion resistance. After the impact grinding test, the cube specimen was cut into the same size as the cuboid specimen, and the compressive strength was tested to establish the relationship between impact grinding time and compressive strength, which was used to evaluate the damage of impact grinding to the interior of concrete.

2. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 1, characterized in that, The cylindrical specimen has a diameter of 300 mm and a height of 100 mm, the cube specimen has a length of 100 mm, a width of 100 mm and a height of 100 mm, and the cuboid specimen has a length of 100 mm, a width of 100 mm and a height of 70 mm.

3. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 1, characterized in that, The correction factor is calculated using the following formula: Where: K is the compressive strength correction factor; f1 is the average compressive strength of a 100mm cube specimen, in MPa; f 70 This represents the average compressive strength of a rectangular specimen with a height of 70 mm, expressed in MPa.

4. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 1, characterized in that, Impact and abrasion resistance is calculated using the following formula: In the formula: f a t represents the abrasion resistance strength of concrete, expressed in h / (kg / m²); t represents the abrasion time, expressed in h; A represents the abrasion area, expressed in m²; m0 represents the mass of a single specimen before abrasion, expressed in kg; m t The mass of a single specimen after t hours of grinding is expressed in kg.

5. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 1, characterized in that, The compressive strength of the concrete after grinding is calculated using the following formula: f t =K×f t70 In the formula: f t The compressive strength of the concrete after grinding is expressed in MPa, where K is the compressive strength correction factor, and f is the compressive strength. t70 The compressive strength of the concrete specimen obtained after grinding for t hours and cutting is expressed in MPa.

6. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to any one of claims 1 to 5, characterized in that, Weighing to obtain m o Beforehand, the cube specimen was immersed in water for a set time, then removed, the surface moisture was wiped off, and it was weighed.

7. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 6, characterized in that, The first setting time is equal to the grinding time of the cylindrical specimen in the underwater steel ball method.

8. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 1, characterized in that, The specimen molding dies used include: The outer cylinder is a split structure, consisting of two symmetrical semi-circular rings joined together by bolts to form a complete circular cylindrical structure. The inner cylinder of the cube is a one-piece structure containing four cube-shaped chambers, with a positioning flange at the bottom; The chassis has cylindrical bosses on its surface, which can be fitted into the outer cylinder of the cylinder. The surface of the bosses is provided with guide grooves that can be fitted into the positioning flanges of the inner cylinder of the cube. Handles are located on both sides of the chassis.

9. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 8, characterized in that, The preparation of cylindrical specimens includes: Apply a release agent or grease to the mold for forming the specimen. The application areas include the inner surface of the outer cylinder of the cylinder, the outer surface and inner surface of the inner cylinder of the cube, and the upper surface of the base. Pour concrete into the mold for forming the specimen, vibrate it to compact it, and demold it after the concrete has initially set. Then place it in a curing box for 28 days of curing.

10. The method for evaluating concrete damage under impact and grinding conditions in hydraulic engineering according to claim 8, characterized in that, The assembly mold for the test piece includes: Insert the positioning flange at the bottom of the inner cylinder of the cube into the guide groove on the surface of the chassis, place the outer cylinder of the cylinder on the chassis, abut against the outer side of the cylindrical boss, and tighten it with bolts.

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