Experimental simulation device and evaluation method for bed load abrasion of mortar and concrete

Abstract

The present invention discloses a test simulation device and method for bedload abrasion mortar and concrete, comprising a specimen table, a specimen support, a bedload abrasion mechanism, a displacement sensor, a velocity sensor and a specimen height control mechanism; the top surface of the specimen is exposed to form a specimen simulation abrasion surface; the bedload abrasion mechanism comprises a cantilever, a cantilever driving mechanism, an impact hammer and an impact roller; the impact roller is arranged at the bottom center of the impact hammer, and the two ends of the central axis of the impact roller are respectively hinged to the bottom of the impact hammer, and the diameter of the impact roller is not less than 5mm; the displacement sensor can be used to detect the height of the impact hammer; the velocity sensor can be used to detect the speed of the impact hammer; the specimen height control mechanism comprises a specimen top surface height sensor and a specimen height lifting mechanism. The present invention simulates bedload abrasion of cement mortar and concrete from the perspective of energy, which is helpful to reveal the mechanism of abrasion and better guide the anti-abrasion design of hydraulic concrete structures.

Description

Technical Field

[0001] The invention relates to the field of building materials, in particular to a test simulation device and an evaluation method for bedload abrasion mortar and concrete. Background Art

[0002] Hydraulic structures, such as dams, ship locks, flood discharge structures, power station buildings, etc., are in contact with environmental water for a long time. The flow surface is eroded and worn by suspended sediment, bedload and high-speed water flow, which places high requirements on the concrete's anti-abrasion. In addition, the concrete of the pier structure of cross-river and sea bridges is also facing erosion and wear. There are mainly two types of abrasive media in the water flow, namely bedload and suspended sediment. Rocks and sand with a particle size greater than 5mm that move near the riverbed surface by sliding, rolling, jumping or layering are bedload. Sediment with a particle size of less than or equal to 5mm suspended in the water flow and moving with the water flow is suspended sediment.

[0003] Ensuring the safety of bridges across rivers and seas is of great significance. At present, the main test method for the scouring and wear of suspended sediment on concrete is the underwater steel ball method. The underwater steel ball method uses a cylindrical specimen and several (10, 25, 35) steel balls to simulate the rolling of stone and sand on the end faces of mortar and concrete cylinders. The evaluation index is the impact and wear strength (the time required for a unit mass to be worn per unit area) or the wear rate, and the evaluation basis is the mass loss of the specimen. However, the underwater steel ball method still has the following deficiencies during the test process, which need to be improved:

[0004] 1. The problem of equipment loss is quite serious.

[0005] 2. The evaluation basis is relatively simple, failing to link the mass loss with other physical and mechanical properties of the specimen, and failing to organically combine the effect of external force with the impact and wear resistance of the specimen from an energy perspective.

[0006] 3. The underwater steel ball method only simulates the wear caused by rolling friction of the concrete specimen surface when the bedload is not subjected to external forces (the weight of the steel ball is ignored), and does not consider the impact and grinding of the bedload on the concrete surface; it does not consider the surface characteristics of the bedload, such as the irregular shape and edges of the surface; nor does it consider the wear caused by the bedload on the concrete components under compressive stress in actual working conditions. However, the actual working conditions are: in high-speed sand-carrying water flow, the larger the sand and gravel particle size, the greater the number of particles, the greater the momentum of the bedload, and the more significant the impact on the surface of the concrete specimen; the more irregular the sand and gravel surface, that is, the more edges and corners, the greater the local stress on the concrete surface, and the greater the wear effect. Summary of the invention

[0007] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and to provide a test simulation device and an evaluation method for the abrasion of mortar and concrete by bed load. The test simulation device and the evaluation method for the abrasion of mortar and concrete by bed load simulate the abrasion of cement mortar and concrete by bed load from the perspective of energy, which helps to reveal the mechanism of abrasion and better guide the abrasion-resistant design of hydraulic concrete structures.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A test simulation device for bed load impact and abrasion mortar and concrete comprises a test piece table, a test piece support, a bed load impact and abrasion mechanism, a displacement sensor, a speed sensor and a test piece height control mechanism.

[0010] The bracket includes a base, columns and a crossbeam; the columns are installed on both sides of the base, and the crossbeam is installed on the top of the columns.

[0011] The test piece table is arranged on a base just below the cross beam and can clamp the test piece and expose the top surface of the test piece to form a simulated punching and grinding surface of the test piece.

[0012] The bed load grinding mechanism comprises a cantilever, a cantilever driving mechanism, an impact hammer and a grinding roller.

[0013] The top end of the cantilever is hinged to the middle part of the cross beam, and the impact hammer is arranged at the other end of the cantilever; the cantilever can be rotated and locked around the cross beam under the drive of the cantilever driving mechanism.

[0014] The impact grinding roller is arranged at the center of the bottom of the impact hammer, and the two ends of the center axis of the impact grinding roller are respectively hinged with the bottom of the impact hammer, and the impact grinding roller can rotate freely around its own axis; the diameter of the impact grinding roller is not less than 5mm.

[0015] The displacement sensor can be used to detect the height of the impact hammer.

[0016] The speed sensor can be used to detect the speed of the impact hammer and is connected to the cantilever drive mechanism.

[0017] The test piece height control mechanism comprises a test piece top surface height sensor and a test piece height lifting mechanism connected with the top surface height sensor.

[0018] The test piece top surface height sensor can be used to detect the height of the test piece top surface.

[0019] The specimen height lifting mechanism is used to control the height lifting of the specimen table.

[0020] The central axis of the grinding roller is parallel to the crossbeam.

[0021] The length of the cantilever can be adjusted.

[0022] A plurality of spherical protrusions are evenly distributed on the roller surface of the grinding roller, and the diameter of each spherical protrusion is not less than 5mm.

[0023] By adjusting the mass of the cantilever and / or the hammer, bed loads with different water velocities can be simulated.

[0024] The experimental simulation method of bedload abrasion mortar and concrete includes the following steps.

[0025] Step 1, preparing the specimen: preparing the specimen of set specifications and curing it; wherein the specimen material is mortar or concrete.

[0026] Step 2: Saturate the specimen with water: Saturate the specimen after curing with water.

[0027] Step 3, specimen clamping: wipe the surface of the saturated specimen dry and weigh it; then, the specimen table is raised and lowered under the control of the height lifting mechanism; and the weighed specimen is clamped and fixed on the specimen table; the top surface of the clamped specimen is exposed to form a simulated punching and grinding surface of the specimen.

[0028] Step 4: The grinding roller is lifted to the initial height: the cantilever is driven by the cantilever drive mechanism to rotate upward around the crossbeam and lift to the set initial height and lock it; at this time, the speed sensor is started and set to zero.

[0029] Step 5, raising the height of the specimen: the specimen table height is raised by the specimen height lifting mechanism. During the process of raising and lowering the specimen table height, the specimen top surface height is detected in real time by the specimen top surface height sensor until the specimen top surface height reaches the set height.

[0030] Step 6, bed load grinding, specifically includes the following steps.

[0031] Step 61, the height of the grinding roller is lowered: the cantilever is released from the initial height of step 4, and drives the grinding roller to swing downward clockwise in a free fall manner; during the downward swing of the grinding roller, the displacement sensor will monitor the height of the load bearing grinding roller in real time; the speed sensor will monitor the swing speed of the cantilever in real time.

[0032] Step 62, bed material grinding: when the grinding roller swings downward to above the specimen, the grinding roller will grind against the top surface of the specimen and rotate;

[0033] Step 63, detecting the grinding height: the swing arm continues to swing clockwise under the action of inertial force, and the grinding roller detaches from the top surface of the specimen until the speed is zero; during the inertial swing process, the speed sensor monitors the swing speed of the cantilever in real time; when the speed sensor detects that the swing speed of the cantilever is zero, the cantilever drive mechanism locks the cantilever position, and the displacement sensor detects and records the grinding height of the grinding roller at this time.

[0034] Step 64, the height of the specimen is lowered: in step 63, after the punching and grinding roller is separated from the top surface of the specimen, the specimen is driven by the specimen height lifting mechanism to lower its height.

[0035] Step 7: The cantilever driving mechanism releases the position lock of the cantilever, and repeats steps 4 and 6 until the designed number of punching and grinding times N is reached, and the punching and grinding height of each time is recorded; wherein N≥6.

[0036] Step 8. Calculate the total impact energy E of the specimen: Calculate the total impact energy E based on the mass of the cantilever and impact hammer, the initial height and the impact height of each time.

[0037] The method also includes step 9, test piece testing, wherein the specific testing method includes the following steps:

[0038] Step 91, observe the appearance integrity of the specimen: stop the impact and grinding test, take out the specimen from the specimen table, and inspect the appearance integrity and surface cracks of the specimen surface.

[0039] Step 92, internal crack detection: use internal damage detection equipment to detect the number and size of internal cracks in the specimen after punching and grinding.

[0040] Step 93, physical and mechanical properties testing: the compressive strength and splitting tensile strength of the punched and ground specimens are tested.

[0041] The method further includes step 10, punching and grinding performance evaluation: according to the purpose to be evaluated and in combination with the total punching and grinding energy E of the specimen obtained in step 8 and the specimen test result in step 9, the punching and grinding performance evaluation is performed.

[0042] In step 10, the objectives to be evaluated include guiding the development of new impact-resistant and wear-resistant materials, durability evaluation of materials subjected to stress, and durability evaluation of materials subjected to tensile stress.

[0043] Step 10-1: When the purpose of the evaluation is to evaluate the durability of materials that bear stress, the evaluation index is the percentage reduction of compressive strength per unit impact energy f cu,loss , the specific calculation method is:

[0044]

[0045] Among them, f cu,0 is the initial compressive strength of the dry specimen of the saturated surface in step 3; f′ cu is the compressive strength of the specimen after punching and grinding in step 93. cu,loss The lower the better. When the value is higher than the minimum design requirement, it indicates that the material is not suitable for use in the design environment.

[0046] Step 10-2: When the purpose of the evaluation is the durability evaluation of the material bearing tensile stress, the evaluation index is the percentage reduction of the splitting tensile strength per unit impact energy fts,loss , the specific calculation method is:

[0047]

[0048] Among them, f ts,0 is the initial splitting tensile strength of the dry specimen of the saturated surface in step 3; f′ ts is the splitting tensile strength of the specimen after punching and grinding in step 93. ts,loss The lower the better. When the value is higher than the minimum design requirement, it indicates that the material is not suitable for use in the design environment.

[0049] Step 10-3: When the purpose of the evaluation is to guide the development of new impact-resistant and wear-resistant materials, the evaluation index needs to be determined based on the test results of the specimen appearance integrity test in step 91.

[0050] Step 10-3A: When the specimen has an incomplete appearance and has peeling or wear grooves on the surface, the evaluation index is the average adhesion work W and the unit wear energy mass loss m. loss .

[0051]

[0052]

[0053] Where S is the total area of ​​the peeling or wear groove; m is the total mass loss.

[0054] Step 10-3B, when the specimen has a complete appearance and there is no peeling or grinding groove on the surface of the specimen, the evaluation indicators are the total length of cracks L per unit grinding energy and unit area, the maximum width of cracks d per unit grinding energy and unit area, and the number of cracks n per unit grinding energy and unit area. The specific calculation formulas are:

[0055]

[0056]

[0057]

[0058] Among them, S 上表面 is the area of ​​the top surface of the specimen.

[0059] L 表 and L 内 are the total length of surface cracks and the total length of internal cracks, respectively.

[0060] d 表 and d 内 They are the maximum width of surface cracks and the maximum width of internal cracks, respectively.

[0061] n 表and n 内 are the number of surface cracks and the number of internal cracks, respectively.

[0062] The present invention has the following beneficial effects:

[0063] 1. The experimental device of the present invention is simple and the device itself has little wear and tear.

[0064] 2. The evaluation method is more scientific and reasonable. In addition to using the mass loss of the specimen as the basis for evaluation, the present invention also adds energy as a basis, and organically links the abrasion energy of the specimen with the mechanical properties (residual strength), defect characteristics (cracks) and material structure characteristics (interface properties) of the specimen. The structure of the material determines the properties of the material. The properties are the external reflection of the structure and have a decisive influence on the performance of the material. After the energy is introduced, the mechanical properties, specimen structure and defect characteristics of the specimen after abrasion are linked. Compared with the use of a single mass loss as the basis for evaluation, the evaluation method used in the present invention is more reasonable. In addition, since the surface tension of mortar and concrete is not only anisotropic, the surface free energy in different regions is also different. The surface tension and surface free energy of the protrusions on the solid surface are greater than those of the depressions. The force between the various phases of cement mortar and concrete is generated by the interaction between the surface force field of each phase and the surface force field of the adjacent phase. Abrasion is external energy input to destroy the interface force. Therefore, the present invention evaluates the suspended sediment abrasion of mortar and concrete surface from the perspective of energy, which helps to reveal the mechanism of abrasion and better guide the abrasion-resistant design of hydraulic concrete structures.

[0065] 3. The present invention can also evaluate the abrasion resistance of constrained mortar and concrete specimens in actual working conditions, and is particularly suitable for evaluating the abrasion resistance of concrete of pressure-bearing structures such as bridge piers.

[0066] 4. The present invention can simulate the impact and grinding effect of water velocity, flow rate, bed load specifications and quantity on mortar and concrete. If the bed load is small in quantity and large in particle size, the impact and grinding roller can be simulated by a cylindrical roller with the same diameter as the bed load particle size; if the bed load has many edges and corners, some protrusions can be added to the surface of the cylindrical roller to simulate the edges and corners of the bed load; if the water velocity is high, the cantilever or the impact and grinding roller mass can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 The schematic diagram of the structure of a test simulation device for bed load abrasion mortar and concrete of the present invention is shown.

[0068] Figure 2 Shows Figure 1 Left side view.

[0069] Figure 3 The schematic diagram of the structure of the grinding roller in the present invention is shown.

[0070] Figure 4 Shows Figure 1 Top view of the .

[0071] Figure 5 The schematic diagram of the structure of the test piece platform in the present invention is shown.

[0072] Figure 6 Schematic diagram showing the average adhesion work W and interfacial tension of aggregate and gel in concrete specimens.

[0073] Among them are:

[0074] 11. Column; 12. Beam; 13. Base;

[0075] 21. Cantilever; 22. Impact hammer; 23. Grinding roller;

[0076] 31. Test piece table; 32. Pressing plate; 33. U-shaped groove side plate; 34. Test piece height lifting mechanism;

[0077] 4. Displacement sensor; 5. Speed ​​sensor; 6. Servo motor; 7. Specimen top surface height sensor;

[0078] 8. Specimen; 81. Aggregate; 82. Gel. DETAILED DESCRIPTION

[0079] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0080] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0081] like Figure 1 , Figure 2 and Figure 4 As shown, a test simulation device for bed load abrasion mortar and concrete includes a specimen table 31, a specimen support, a bed load abrasion mechanism, a displacement sensor 4, a speed sensor 5 and a specimen height control mechanism.

[0082] The bracket includes a base 13, a column 11 and a crossbeam 12; the columns are installed on both sides of the base, and the crossbeam is installed on the top of the columns. In this embodiment, the distance between the two columns is preferably adjustable. Each column is preferably an isosceles triangle structure, and each column is preferably concentrically provided with isosceles triangle weight-reducing holes.

[0083] The specimen is preferably square, and the specimen can be a mortar specimen or a concrete specimen.

[0084] The test piece table is arranged on a base just below the cross beam and can clamp the test piece and expose the top surface of the test piece to form a simulated punching and grinding surface of the test piece.

[0085] like Figure 5 As shown, a U-shaped groove is provided on the specimen table, and a specimen clamp is provided in the U-shaped groove, and the specimen clamp includes two parallel pressure plates 32 and a plurality of screws. Each pressure plate is preferably threadedly connected to the corresponding U-shaped groove side plate 33 by at least one screw. The distance between the two pressure plates is adjusted by the screw to achieve the clamping of the specimen. In this embodiment, the height of the U-shaped groove side plate and the pressure plate are both less than the side length of the specimen, so that the top surface of the specimen is exposed.

[0086] The specimen height control mechanism includes a specimen top surface height sensor 7 and a specimen height lifting mechanism 34 connected to the top surface height sensor.

[0087] The test piece top surface height sensor can be used to detect the height of the test piece top surface, and is preferably arranged in the weight reduction hole.

[0088] The specimen height lifting mechanism is used to control the height lifting of the specimen table, and is preferably a lifting motor or a lifting cylinder.

[0089] The displacement medium grinding mechanism comprises a cantilever 21 , a cantilever driving mechanism, an impact hammer 22 and a grinding roller 23 .

[0090] The top of the cantilever is hinged to the middle of the cross beam, and an impact hammer is arranged at the other end of the cantilever; the cantilever can be rotated and locked around the cross beam under the drive of the cantilever drive mechanism. Further, the length of the cantilever is preferably adjustable.

[0091] The cantilever drive mechanism is preferably a servo motor 6 with a locking function, but may also be other structures known in the prior art, such as a cylinder.

[0092] like Figure 3 As shown, the grinding roller is arranged at the bottom center of the impact hammer, and the two ends of the center axis of the grinding roller are respectively hinged to the bottom of the impact hammer, the center axis of the grinding roller is preferably parallel to the crossbeam, and the grinding roller can rotate freely around its own axis.

[0093] The present invention can simulate the impact of water velocity, flow rate, bed load specifications and quantity on mortar and concrete. If the bed load is small in quantity and large in particle size, the impact roller can be simulated by a cylindrical roller with the same diameter as the bed load particle size, such as setting the diameter of the direct impact roller to be no less than 5 mm.

[0094] If the bed load has many edges and corners, some protrusions can be added to the surface of the cylindrical roller to simulate the edges and corners of the bed load; for example, a plurality of spherical protrusions (more preferably hemispherical protrusions) are preferably evenly distributed on the roller surface of the grinding roller, and the diameter of each spherical protrusion is preferably not less than 5 mm.

[0095] The present invention adjusts the mass of the cantilever and / or the impact hammer to simulate the transported material with different water flow speeds. If the water flow speed is high, the mass of the cantilever or the impact roller is increased.

[0096] The above-mentioned displacement sensor is preferably arranged on the impact hammer and can be used to detect the height of the impact hammer.

[0097] The speed sensor is also preferably arranged on the impact hammer, can be used to detect the speed of the impact hammer, and is connected to the cantilever drive mechanism.

[0098] The experimental simulation method of bedload abrasion mortar and concrete includes the following steps.

[0099] Step 1, preparing the specimen: preparing the specimen of set specifications and curing it; wherein the specimen material is mortar or concrete.

[0100] The preferred specifications of mortar specimens are 40×40×160mm prisms and 70.7×70.7×70.7mm cubes; the preferred specifications of concrete specimens are 150×150×150mm cubes, 100×100×100mm cubes, 200×200×200mm cubes, 150×150×300mm prisms, and 100×100×300mm prisms.

[0101] In this embodiment, 150×150×150 mm cubic concrete specimens are preferably prepared and cured to 28 days of age.

[0102] Step 2: Saturate the specimen with water: Place the cured specimen in a water pool at 20℃±1℃ for saturation.

[0103] Step 3, specimen clamping: wipe the surface of the saturated specimen dry and weigh it; then, the specimen table is raised and lowered under the control of the height lifting mechanism; and the weighed specimen is clamped and fixed on the specimen table; the top surface of the clamped specimen is exposed to form a simulated punching and grinding surface of the specimen.

[0104] Step 4: The grinding roller is lifted to the initial height: the cantilever is driven by the cantilever drive mechanism to rotate upward around the crossbeam and lift to the set initial height and lock it; at this time, the speed sensor is started and set to zero.

[0105] In this embodiment, the initial height is preferably when the cantilever is raised to a horizontal height, that is, Figure 1 The center pointer is at 3 o'clock.

[0106] Step 5, raising the height of the specimen: the specimen table height is raised by the specimen height lifting mechanism. During the process of raising and lowering the specimen table height, the specimen top surface height is detected in real time by the specimen top surface height sensor until the specimen top surface height reaches the set height.

[0107] Step 6, bed load grinding, specifically includes the following steps.

[0108] Step 61, the height of the grinding roller is lowered: the cantilever is released from the initial height of step 4, and drives the grinding roller to swing downward clockwise in a free fall manner; during the downward swing of the grinding roller, the displacement sensor will monitor the height of the load bearing grinding roller in real time; the speed sensor will monitor the swing speed of the cantilever in real time.

[0109] Step 62, bedstock grinding: When the grinding roller swings downward to the top of the specimen (i.e., close to or at Figure 1 When the center pointer is at 6 o'clock, the grinding roller will grind against the top surface of the specimen and rotate.

[0110] Step 63, detecting the grinding height: the swing arm continues to swing clockwise under the action of inertial force, and the grinding roller detaches from the top surface of the specimen until the speed is zero; during the inertial swing process, the speed sensor monitors the swing speed of the cantilever in real time; when the speed sensor detects that the swing speed of the cantilever is zero, the cantilever drive mechanism locks the cantilever position, and the displacement sensor detects and records the grinding height of the grinding roller at this time.

[0111] Step 64, the height of the specimen is lowered: in step 63, after the grinding roller is separated from the top surface of the specimen (the position of the cantilever can be detected by setting an infrared detector), the specimen will be driven by the specimen height lifting mechanism to lower its height.

[0112] Step 7: The cantilever driving mechanism releases the position lock of the cantilever, and repeats steps 4 and 6 until the designed number of punching and grinding times N is reached, and the punching and grinding height of each time is recorded; wherein N≥6, and in this embodiment, preferably N=20.

[0113] Step 8. Calculate the total impact energy E of the specimen: Calculate the total impact energy E based on the mass of the cantilever and impact hammer, the initial height and the impact height of each time.

[0114] Step 9: Test piece testing. The specific testing method includes the following steps.

[0115] Step 91, observe the appearance integrity of the specimen: stop the impact and grinding test, take out the specimen from the specimen table, and inspect the appearance integrity and surface cracks of the specimen surface.

[0116] Step 92, internal crack detection: use internal damage detection equipment to detect the number and size of internal cracks in the specimen after punching and grinding.

[0117] Step 93, physical and mechanical properties testing: the compressive strength and splitting tensile strength of the punched and ground specimens are tested.

[0118] Step 10, punching and grinding performance evaluation: according to the purpose to be evaluated, combined with the total punching and grinding energy E of the specimen obtained in step 8 and the specimen test result in step 9, the punching and grinding performance evaluation is performed.

[0119] In step 10, the objectives to be evaluated include guiding the development of new impact-resistant and wear-resistant materials, durability evaluation of materials subjected to stress, and durability evaluation of materials subjected to tensile stress.

[0120] Step 10-1: When the purpose of the evaluation is to evaluate the durability of materials that bear stress, the evaluation index is the percentage reduction of compressive strength per unit impact energy f cu,loss , the specific calculation method is:

[0121]

[0122] Among them, f cu,0 is the initial compressive strength of the dry specimen of the saturated surface in step 3; f′ cu is the compressive strength of the specimen after punching and grinding in step 93.

[0123] Step 10-2: When the purpose of the evaluation is the durability evaluation of the material bearing tensile stress, the evaluation index is the percentage reduction of the splitting tensile strength per unit impact energy f ts,loss , the specific calculation method is:

[0124]

[0125] Among them, f ts,0 is the initial splitting tensile strength of the dry specimen of the saturated surface in step 3; f′ ts It is the splitting tensile strength of the specimen after punching and grinding in step 93.

[0126] Step 10-3: When the purpose of the evaluation is to guide the development of new impact-resistant and wear-resistant materials, the evaluation index needs to be determined based on the test results of the specimen appearance integrity test in step 91.

[0127] Step 10-3A: When the specimen has an incomplete appearance and has peeling or wear grooves on the surface, the evaluation index is the average adhesion work W and the unit wear energy mass loss m. loss , as shown in Table 1.

[0128] Table 1

[0129]

[0130] Wherein, S is the total area of ​​the detached or abraded groove; m is the total mass loss, which is the difference between the dry mass of the saturated surface in step 3 and the mass of the specimen after abrasion in step 91.

[0131] Step 10-3B, when the specimen has a complete appearance and there is no peeling or grinding groove on the surface of the specimen, the evaluation indicators are the total length of cracks L per unit grinding energy and unit area, the maximum width of cracks d per unit grinding energy and unit area, and the number of cracks n per unit grinding energy and unit area. The specific calculation formulas are:

[0132] Table 2

[0133]

[0134] Among them, S 上表面 is the area of ​​the top surface of the specimen.

[0135] L 表 and L 内 are the total length of surface cracks and the total length of internal cracks, respectively.

[0136] d 表 and d 内 They are the maximum width of surface cracks and the maximum width of internal cracks, respectively.

[0137] n 表 and n 内 are the number of surface cracks and the number of internal cracks, respectively.

[0138] In addition to using the mass loss of the specimen as the basis for evaluation, the present invention also adds energy as a basis, organically linking the grinding energy of the specimen with the mechanical properties (residual strength), defect characteristics (cracks) and material structure characteristics (interface properties) of the specimen. The structure of the material determines the properties of the material, and the properties are the external reflection of the structure and have a decisive influence on the performance of the material. After the energy is introduced, the mechanical properties, specimen structure and defect characteristics of the specimen after the grinding are linked together. Compared with the use of a single mass loss as the basis for evaluation, the evaluation method used by the present invention is more reasonable.

[0139] The concrete in the concrete specimen is a three-phase composite material of solid, liquid and gas, which is composed of hydration products of cementitious materials, aggregates and pores (water in the pores). Cementitious materials are the binder of aggregates. The adhesion between hydration products and aggregates is actually the result of the mutual attraction of particles under the residual force field of the solid surface. The interaction force is also called surface force, which is divided into chemical force and molecular attraction. Take the separation of aggregate and gel interface as an example. Figure 6 As shown, the adhesion work W is equal to the newly formed surface energy γ SV and γ′ SVAnd the difference in interfacial energy γ between the disappeared aggregate and the gel is shown in the following formula, thereby organically linking the energy (the impact and abrasion energy E of the specimen) with its interfacial performance.

[0140] W=γ SV +γ′ SV -γ

[0141] By observing the surface morphology of the specimen and using graphic analysis software, it is very convenient to obtain the area of ​​the specimen wear after punching and grinding, and then combined with the punching and grinding energy, the average adhesion work of the specimen can be obtained. The interface performance of the material can be further analyzed based on the above formula.

[0142] Concrete is a brittle material. The theoretical strength of brittle materials is several hundred times the actual strength. The microcracks inside the material act as a stress multiplier. Griffith theory gives the relationship between the actual fracture strength and the length of the microcracks, as shown in the following formula. The residual strength (actual strength) of the specimen after impact and abrasion can be linked to the internal microcracks of the specimen after impact and abrasion through the following formula.

[0143]

[0144] Where: R——breaking strength;

[0145] C——internal microcrack length;

[0146] E0——elastic modulus;

[0147] a——Surface free energy.

[0148] According to the above formula, the change in the length of microcracks inside the specimen after punching and grinding can be analyzed.

[0149] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. Experimental simulation method for bed load abrasion of mortar and concrete, characterized by: A test simulation device based on bedload impact mortar and concrete, the test simulation device comprising a specimen table, a specimen support, a bedload impact mechanism, a displacement sensor, a velocity sensor and a specimen height control mechanism; The bracket includes a base, a column and a beam; the columns are installed on both sides of the base, and the beam is installed on the top of the column; The test piece table is arranged on a base directly below the crossbeam and can clamp the test piece and expose the top surface of the test piece to form a simulated punching and grinding surface of the test piece; The bed load grinding mechanism comprises a cantilever, a cantilever driving mechanism, an impact hammer and a grinding roller; The top end of the cantilever is hinged to the middle of the crossbeam, and the impact hammer is arranged at the other end of the cantilever; the cantilever can be rotated around the crossbeam and locked under the drive of the cantilever drive mechanism; The grinding roller is set at the center of the bottom of the impact hammer, and the two ends of the center axis of the grinding roller are respectively hinged with the bottom of the impact hammer, and the grinding roller can rotate freely around its own axis; the diameter of the grinding roller is not less than 5mm; The displacement sensor can be used to detect the height of the impact hammer; The speed sensor can be used to detect the speed of the impact hammer and is connected to the cantilever drive mechanism; The test piece height control mechanism includes a test piece top surface height sensor and a test piece height lifting mechanism connected to the top surface height sensor; the test piece top surface height sensor can be used to detect the height of the test piece top surface; The specimen height lifting mechanism is used to control the height lifting of the specimen table; The test simulation method comprises the following steps: Step 1, preparing the specimen: preparing the specimen of set specifications and curing it; wherein the specimen material is mortar or concrete; Step 2: Saturate the specimen with water: saturate the specimen after curing; Step 3, specimen clamping: wipe the surface of the saturated specimen dry and weigh it; then, the specimen table is raised and lowered under the control of the height lifting mechanism; and the weighed specimen is clamped and fixed on the specimen table; the top surface of the clamped specimen is exposed to form a simulated punching and grinding surface of the specimen; Step 4, the grinding roller is lifted to the initial height: the cantilever is driven by the cantilever drive mechanism to rotate upward around the crossbeam and lift to the set initial height and lock it; at this time, the speed sensor is started and set to zero; Step 5, the height of the specimen is raised: the specimen table is raised by the specimen height lifting mechanism. During the process of the specimen table height lifting, the specimen top surface height is detected in real time by the specimen top surface height sensor until the specimen top surface height reaches the set height; Step 6: bed material grinding, specifically including the following steps: Step 61, the height of the grinding roller is lowered: the cantilever is released from the initial height of step 4, and drives the grinding roller to swing downward clockwise in a free fall manner; during the downward swing of the grinding roller, the displacement sensor monitors the height of the bed load grinding roller in real time; the speed sensor monitors the swing speed of the cantilever in real time; Step 62, bed material grinding: when the grinding roller swings downward to above the specimen, the grinding roller will grind against the top surface of the specimen and rotate; Step 63, detecting the grinding height: the swing arm continues to swing clockwise under the action of inertial force, and the grinding roller is separated from the top surface of the test piece until the speed is zero; during the inertial swing process, the speed sensor monitors the swing speed of the cantilever in real time; when the speed sensor detects that the swing speed of the cantilever is zero, the cantilever drive mechanism locks the cantilever position, and the displacement sensor detects and records the grinding height of the grinding roller at this time; Step 64, lowering the height of the specimen: in step 63, after the punching and grinding roller is separated from the top surface of the specimen, the specimen will be driven by the specimen height lifting mechanism to lower its height; Step 7, the cantilever driving mechanism releases the position lock of the cantilever, and repeats steps 4 and 6 until the designed number of punching and grinding times N is reached, and the punching and grinding height of each time is recorded; wherein N≥6; Step 8. Calculate the total impact energy E of the specimen: Calculate the total impact energy E based on the mass of the cantilever and impact hammer, the initial height and the impact height of each time.

2. The test simulation method for bed load abrasion mortar and concrete according to claim 1 is characterized by: The method also includes step 9, test piece testing, wherein the specific testing method includes the following steps: Step 91, observing the appearance integrity of the specimen: stop the punching and grinding test, take out the specimen from the specimen table, and inspect the appearance integrity and surface cracks of the specimen surface; Step 92, internal crack detection: using internal damage detection equipment to detect the number and size of internal cracks in the specimen after punching and grinding; Step 93, physical and mechanical properties testing: the compressive strength and splitting tensile strength of the punched and ground specimens are tested.

3. The test simulation method for bed load abrasion mortar and concrete according to claim 2, characterized in that: The method further includes step 10, punching and grinding performance evaluation: according to the purpose to be evaluated and in combination with the total punching and grinding energy E of the specimen obtained in step 8 and the specimen test result in step 9, the punching and grinding performance evaluation is performed.

4. The test simulation method for bed load abrasion mortar and concrete according to claim 3, characterized in that: In step 10, the purposes to be evaluated include guiding the development of new impact-resistant materials, durability evaluation of materials subject to stress, and durability evaluation of materials subject to tensile stress; Step 10-1: When the purpose of the evaluation is to evaluate the durability of materials that bear stress, the evaluation index is the percentage reduction of compressive strength per unit impact energy f cu,loss , the specific calculation method is: Among them, f cu,0 is the initial compressive strength of the dry specimen of the saturated surface in step 3; f′ cu is the compressive strength of the specimen after punching and grinding in step 93; Step 10-2: When the purpose of the evaluation is the durability evaluation of the material bearing tensile stress, the evaluation index is the percentage reduction of the splitting tensile strength per unit impact energy f ts,loss , the specific calculation method is: Among them, f ts,0 is the initial splitting tensile strength of the dry specimen of the saturated surface in step 3; f′ ts is the splitting tensile strength of the specimen after punching and grinding in step 93; Step 10-3: When the purpose of the evaluation is to guide the development of new impact-resistant and wear-resistant materials, the evaluation index needs to be determined based on the test results of the specimen appearance integrity test in step 91; Step 10-3A: When the specimen has an incomplete appearance and has peeling or wear grooves on the surface, the evaluation index is the average adhesion work W and the unit wear energy mass loss m. loss ; Where S is the total area of ​​the shedding or wear groove; m is the total mass loss; Step 10-3B, when the specimen has a complete appearance and there is no peeling or grinding groove on the surface of the specimen, the evaluation indicators are the total length of cracks L per unit grinding energy and unit area, the maximum width of cracks d per unit grinding energy and unit area, and the number of cracks n per unit grinding energy and unit area. The specific calculation formulas are: Among them, S 上表面 is the area of ​​the top surface of the specimen; L 表 and L 内 are the total length of surface cracks and the total length of internal cracks, respectively; d 表 and d 内 are the maximum width of surface cracks and the maximum width of internal cracks, respectively; n 表 and n 内 are the number of surface cracks and the number of internal cracks, respectively.

5. The test simulation method for bed load abrasion mortar and concrete according to claim 1, characterized in that: The central axis of the grinding roller is parallel to the crossbeam.

6. The test simulation method for bed load abrasion mortar and concrete according to claim 1, characterized in that: The length of the cantilever can be adjusted.

7. The test simulation method for bed load abrasion mortar and concrete according to claim 1, characterized in that: A plurality of spherical protrusions are evenly distributed on the roller surface of the grinding roller, and the diameter of each spherical protrusion is not less than 5mm.

8. The test simulation method for bed load abrasion mortar and concrete according to claim 1, characterized in that: By adjusting the mass of the cantilever and / or the hammer, bed loads with different water velocities can be simulated.

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