A device and method for evaluating the impact resistance of a toughened cement panel

Abstract

The application discloses a kind of toughened cement panel impact toughness detection device, including base, impact frame, drop hammer structure, bottom plate positioning structure, impacted test piece positioning structure, board corner void test simulation structure, board edge void test simulation structure, board middle void test simulation structure, slide rail is fixed on the base on horizontal ground by bolt, bottom plate positioning structure is composed of four baffle and six universal ball, the upper end of drop hammer is connected with the lower end of the top plate of impact frame with the round ring of bolt connection, and the drop hammer is fixed with the top plate by the round ring of bolt passing through both.The test, by using different bottom plate to simulate different types of void, by changing the position of drop hammer to be suitable for different void type impact test.The evaluation method of the application, by damage accumulation degree to evaluate material toughness, provides a kind of void evaluation index.The toughness of energy method evaluation is more intuitive, easy to operate.

Description

Technical Field

[0001] This invention relates to a device for testing the impact toughness of road surfaces, and more particularly to a device and evaluation method for testing the impact toughness of toughened cement panels. Background Technology

[0002] Cement concrete is a brittle and easily cracked material. It is highly susceptible to cracking and breakage under sustained impact, which affects the serviceability and safety of the pavement. Besides the serious safety impact, if the pavement fails to reach its designed service life, the resulting maintenance or even reconstruction costs will be extremely high.

[0003] Airport pavements are a typical example of facilities frequently subjected to impact loads. In recent years, the traffic volume at civil aviation airports has been increasing, and in particular, airports accounting for only about 10% of the total number of airports handle 70% of the domestic passenger throughput, which greatly increases the risk of damage to these airport pavements. At the same time, with the advancement of aviation technology, the number of medium and large passenger aircraft in civil aviation airports is gradually increasing, posing a considerable challenge to civil aviation airport pavements.

[0004] Currently, concrete pavement is the most common pavement structure used in civil aviation airports; however, its performance is far from ideal. Most concrete pavements fail to reach their designed 30-year lifespan, with an average lifespan of only 15-20 years, and some even showing signs of damage within 2-3 years of construction. Voiding is one of the most common types of pavement damage. Statistics show that nearly 70% of airport pavements have a voiding rate greater than 30%, with 30% of airports experiencing severe voiding at the pavement slab level, exceeding 60%. Voiding alters the pavement's support structure, reduces the mechanical properties of the voided areas, and, combined with aircraft impact loads, easily leads to severe pavement damage such as slab breakage and fragmentation, significantly reducing the pavement's service life and seriously impacting aircraft operational safety. To address this problem, scholars both domestically and internationally have proposed many methods to increase concrete toughness, such as adding toughening materials like fibers and rubber powder to extend the concrete's service life.

[0005] However, directly constructing a test road to evaluate the impact resistance of fiber-reinforced concrete materials in the void state requires a lot of manpower and resources. Therefore, developing an experimental testing device for the impact toughness of fiber-reinforced concrete materials in the void state with small test result dispersion and convenient test operation is of great significance for improving the impact toughness of concrete and the pavement life in the void state. Summary of the Invention

[0006] The application aims to provide an impact toughness detection device and evaluation method for a toughened cement panel, which can measure the impact toughness of the toughened cement panel in a void state, has low test cost, and has small test result discreteness.

[0007] The impact toughness detection device for the toughened cement panel comprises a base, an impact frame, a drop hammer, a bottom plate positioning structure, an impacted test piece positioning structure, a void test simulation structure, and a preset crack structure.

[0008] The impact frame comprises two sliding rails and a top plate, and the top plate is arranged on the upper part of the sliding rails.

[0009] The base is provided with a plurality of bolt holes, and the sliding rails are fixed on the base on the horizontal ground through bolts.

[0010] The impacted test piece positioning structure is composed of four baffle plates and six universal balls.

[0011] The upper end of the drop hammer and the lower end of the top plate are provided with a ring connected with a bolt, and the drop hammer is movably connected with the top plate through the bolt.

[0012] The bottom plate positioning structure comprises a groove arranged on a bottom plate and the bottom plate placed in the groove.

[0013] Further, the drop hammer is a pentahedron steel drop hammer with a circular arc bottom.

[0014] Further, the impacted test piece positioning structure is composed of four baffle plates vertically welded on the base, four side universal balls, and two top universal balls.

[0015] The plate corner void test simulation structure comprises a plate corner void test bottom plate mold and a plate corner void test bottom plate.

[0016] The plate edge void test simulation structure comprises a plate edge void test bottom plate mold and a plate edge void test bottom plate.

[0017] The plate middle void test simulation structure comprises a plate middle void test bottom plate mold and a plate middle void test bottom plate.Further, the preset crack structure includes the preset cracks of the corner voided specimen, the preset cracks of the edge voided specimen, and the preset cracks of the middle voided specimen, which are all preset during the manufacturing process of the specimen.

[0018] An evaluation method of an impact toughness detection device, comprising the following steps:

[0019] S1, specimen forming, using a designed voiding mold to prepare a voided base plate, and at the same time, presetting a crack with a width of 2 mm and a depth of 3 mm in the steel plate during the manufacturing of the voided specimen;

[0020] S2, specimen installation, placing the prepared voided base plate on the base, then placing the voided specimen on the voided base plate, and adjusting the position of the voided specimen to make the voided specimen flush with the side surface of the voided base plate;

[0021] S3, hammer position setting, installing the hammer according to the required voiding scene of the test to ensure that the hammer can accurately impact the preset crack when falling;

[0022] S4, impact test, lifting the hammer to the set height, pulling out the pin, and allowing the hammer to perform free fall to impact the specimen, and recording the crack depth h of the specimen after impact; repeating step S3, and recording the impact number n when the specimen is completely broken along the preset crack and the crack depth h of the specimen after each impact;

[0023] S5, fitting the impact number n and the crack depth h to obtain a crack depth-impact number curve, and the expression is as follows:

[0024] h = a + bn + cn 2

[0025] Wherein, |2cn 终 +b| represents the average increase value of the crack depth per impact; and |2cn 终 +b| is defined as an impact damage factor;

[0026] S6, cumulative damage calculation, and the calculation method is as follows:

[0027]

[0028] In the formula, M is an impact damage cumulative factor, n is the impact number, and n 终 is the final impact number;

[0029] S7, using a concrete toughness improvement rate I 终 to evaluate the toughness improvement of the concrete under the voiding state, and the calculation method is as follows:

[0030]

[0031] In the formula, W终，脱空，外掺 W is the impact energy consumed by the toughened concrete specimen in the non-void state when it is finally cracked, and the unit is J;

[0032] W 终，非脱空，外掺 W is the impact energy consumed by the toughened concrete specimen in the non-void state when it is finally cracked, and the unit is J;

[0033] W 终，脱空，素 W is the impact energy consumed by the toughened concrete specimen in the non-void state when it is finally cracked, and the unit is J;

[0034] W 终，非脱空，素 W is the impact energy consumed by the toughened concrete specimen in the non-void state when it is finally cracked, and the unit is J;I 终 W is the toughness improvement rate of the concrete in the void state, and the unit is %;

[0035] Finally, the impact damage cumulative factor M and the toughness improvement rate I of the concrete in the void state are combined 终 to determine the impact toughness of the void specimen, and the judgment criteria are as follows:

[0036] If W 素 < W 外掺 , it indicates that the impact damage factor accumulation speed of the toughened concrete is slow, and the addition of the external mixed material presents a positive hybrid effect;

[0037] If W 素 = W 外掺 , it indicates that the impact damage factor accumulation speed of the toughened concrete is consistent with the plain concrete, and the addition of the external mixed material has no effect on the hybrid of the concrete;

[0038] If W 素 > W 外掺 , it indicates that the impact damage factor accumulation speed of the toughened concrete is slow, and the addition of the external mixed material presents a negative hybrid effect;

[0039] If I 终 ≤20%, it indicates that the addition of the external mixed material has little effect on the toughness improvement of the concrete;

[0040] If 20% < I 终 ≤50%, it indicates that the addition of the external mixed material has a certain effect on the toughness improvement of the concrete;

[0041] If I 终 >50%, it indicates that the addition of the external mixed material has a great effect on the toughness improvement of the concrete.

[0042] Compared with the prior art, the present application has the following remarkable effects:

[0043] 1. The present application simulates different types of voids by changing different base plates, simplifying the traditional paving test road setting void mode;

[0044] 2. The present application is simple to process and easy to adjust, the device is changed into an experimental device suitable for different void types by disassembling the bolts, and the position of the impact hammer is changed by adjusting the bolts;

[0045] 3. The falling hammer impact device of the present application adopts a circular arc shape, which avoids the high dispersion of test results caused by stress concentration;

[0046] 4. The test piece mold of the present application adopts a preset crack form, which is convenient for better observing the damage state of the test piece;

[0047] 5. The toughness of the material is evaluated by the damage accumulation degree, and a void evaluation index is provided, which is more intuitive than the traditional energy method for evaluating toughness. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 Fig. 1 is a structural schematic diagram of the detection device of the present application;

[0049] Figure 2 Fig. 2 is a base structure schematic diagram of the detection device of the present application;

[0050] Fig. 3(a) is a front view of the falling hammer structure of the detection device of the present application;

[0051] Fig. 3(b) is a left view of the falling hammer structure of the detection device of the present application;

[0052] Fig. 4(a) is a schematic diagram of the plate corner void test base plate mold of the present application,

[0053] Fig. 4(b) is a schematic diagram of the plate edge void test base plate mold of the present application,

[0054] Fig. 4(c) is a schematic diagram of the plate middle void test base plate mold of the present application;

[0055] Fig. 5(a) is a schematic diagram of the plate corner void test base plate of the present application,

[0056] Fig. 5(b) is a schematic diagram of the plate edge void test base plate of the present application,

[0057] Fig. 5(c) is a schematic diagram of the plate middle void test base plate of the present application;

[0058] Fig. 6(a) is a schematic diagram of the plate corner void test specimen of the present application,

[0059] Fig. 6(b) is a schematic diagram of the plate edge void test specimen of the present application,

[0060] Fig. 6(c) is a schematic diagram of the plate middle void test specimen of the present application;

[0061] Figure 7 This is a schematic diagram of crack depth measurement according to the present invention.

[0062] Explanation of the labels in the diagram:

[0063] 1-Base, 2-First slide rail, 3-Second slide rail, 4-Top plate, 5-First bolt, 6-Second bolt, 7-Third bolt, 8-Fourth bolt, 9-Groove, 10-Side universal ball joint, 11-Top universal ball joint, 12-Baffle, 13-Concrete base plate, 14-Concrete specimen, 15-Drop hammer, 16-First ring, 17-Second ring, 18-Pin, 19-First plate corner void test positioning bolt hole, 20-Second plate corner void test positioning bolt hole, 21-Third plate corner void test positioning bolt hole, 22-Fourth plate corner void test positioning bolt hole, 23-First plate edge void test positioning bolt hole, 24-Second plate edge void test positioning bolt hole, 25-Third plate edge void test positioning bolt hole, 26-Fourth plate edge void test positioning bolt hole Bolt hole, 27-First plate void test positioning bolt hole, 28-Second plate void test positioning bolt hole, 29-Third plate void test positioning bolt hole, 30-Fourth plate void test positioning bolt hole, 31-Corner void test base plate mold, 32-Edge void test base plate mold, 33-Plate void test base plate mold, 34-Corner void test specimen, 35-First preset crack, 36-Edge void test specimen, 37-Second preset crack, 38-Plate void test specimen, 39-Third preset crack, 40-Corner void test base plate, 41-Corner void area, 42-Edge void test base plate, 43-Edge void area, 44-Plate void test base plate, 45-Plate void area, 46-Preset crack, 47-Crack to be tested. Detailed Implementation

[0064] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0065] like Figures 1-2 As shown, the impact toughness testing device of the present invention includes a base 1, an impact frame, a drop hammer 15, a base plate positioning structure, an impact specimen positioning structure, a plate corner void test simulation structure, a plate edge void test simulation structure, a plate center void test simulation structure, and a preset crack structure. The first slide rail 2 and the second slide rail 3 are respectively fixed to the base on the horizontal ground with the top plate 4 by bolts. The base is provided with bolt holes and a rectangular groove. The impact specimen positioning structure includes four baffles and six universal balls. The upper end of the drop hammer and the lower end of the top plate of the impact frame are both welded with rings connected to pins. The pins pass through the rings of the two to fix the drop hammer to the top plate.

[0066] The impact frame structure comprises two slide rails and a top plate, and the impact frame is fixed to the base by bolts.

[0067] The test piece is selected as a cuboid, the size of the test piece is set as 300mm*300mm*50mm, considering that the size of the coarse aggregate of the concrete is generally 5-25mm gravel and the test piece is easy to break along the preset crack.

[0068] The selected external additive material is fiber, and the test can also be used for the toughening test of concrete with nano calcium carbonate, graphene, carbon nanotube and other materials.

[0069] As shown in Figure 3(a) 、 3(b) , the drop hammer is a pentahedral steel drop hammer with a circular arc-shaped bottom. In order to ensure that the initial cracking impact frequency is not too small and avoid that the final cracking frequency is too large, referring to the standard GB / T 21120-2018 "Synthetic fibers for cement concrete and mortar", four specifications of drop hammer weight are set, i.e. 1kg, 2kg, 3kg and 4kg, and the drop hammer distance from the upper surface of the impact test piece is 300mm. The test personnel can select according to the strength and modulus of the added fiber. The fiber with low strength and low modulus can select the lighter drop hammer of 1kg or 2kg, and the fiber with high strength and high modulus can select the heavier drop hammer of 3kg or 4kg. The upper end of the drop hammer and the lower end of the impact frame top plate are both welded with a ring connected with a bolt, and the bolt is used to control the stop and release of the impact hammer.

[0070] The bottom plate positioning structure is a groove with a size of 300mm*300mm*20mm arranged on the base, and the bottom plate is positioned and the transverse displacement of the bottom plate is limited by placing the bottom plate in the groove.

[0071] The impact test piece positioning structure is composed of four vertical baffles welded on the base and four side universal balls and two top universal balls. The universal balls and the plane of the impact plate keep a small gap, so as to limit the transverse rigid displacement and longitudinal rigid displacement of the impact test piece.

[0072] The corner debonding test simulation structure comprises a corner debonding test bottom plate mold, corner debonding test positioning bolt holes, a base, an impact frame and a drop hammer. The impact frame is fixed and positioned through the corner debonding test positioning bolt holes. The corner debonding test bottom plate is obtained by pouring ordinary concrete into the specially designed corner debonding bottom plate mold and curing and forming, and the corner debonding phenomenon is simulated by artificially manufacturing a debonding area on the corner debonding test bottom plate, as shown in Figure 4(a) 、 5(a) , 6(a).

[0073] The plate corner void bottom plate mold is a steel mold having a void in the form of an isosceles triangle, and the length of the side of the isosceles triangle is set to be 0-120 mm in consideration of the fact that the maximum area of the void of the airport pavement plate is not more than 2 m*2 m, according to the area equivalence principle. The void is constructed in the bottom plate structure to simulate the void.

[0074] The plate edge void test simulation structure is composed of a plate edge void test bottom plate mold, a plate edge void test positioning bolt hole, a base, an impact frame, and a drop hammer. The impact frame is fixed and positioned through the plate edge void test positioning bolt hole, and the plate edge void test bottom plate is obtained by pouring ordinary concrete into the plate edge void test bottom plate mold and curing and molding. The void area is artificially manufactured in the plate edge void test bottom plate to simulate the plate edge void phenomenon, as shown in Figure 4(b) 、 5(b) , 6(b).

[0075] The plate edge void bottom plate mold is a steel mold having a void in the form of a rectangle, and the size of the rectangle is set to be (0-120 mm)*300 mm in consideration of the fact that the maximum area of the void of the airport pavement plate is not more than 2 m*2 m, according to the area equivalence principle. The void is constructed in the bottom plate structure to simulate the void.

[0076] The plate edge void test simulation structure is composed of a plate edge void test bottom plate mold, a plate edge void test positioning bolt hole, a base, an impact frame, and a drop hammer. The impact frame is fixed and positioned through the plate edge void test positioning bolt hole, and the plate edge void test bottom plate is obtained by pouring ordinary concrete into the plate edge void test bottom plate mold and curing and molding. The void area is artificially manufactured in the plate edge void test bottom plate to simulate the plate edge void phenomenon, as shown in Figure 4(c) 、 5(c) , 6(c).

[0077] The plate edge void bottom plate mold is a steel mold having a void in the form of a rectangle, and the size of the rectangle is set to be (0-120 mm)*(0-120 mm) in consideration of the fact that the maximum area of the void of the airport pavement plate is not more than 2 m*2 m, according to the area equivalence principle. The void is constructed in the bottom plate structure to simulate the void.

[0078] The preset crack of the plate corner, plate edge, and plate middle void test piece is manufactured using a steel plate having a thickness of 2 mm in the process of manufacturing the test piece, and the depth of the preset crack is 3 mm, as shown in Figure 7 .

[0079] Example 1:

[0080] The plate corner void impact test is performed by using the impact resistance testing device of the application, and includes the following steps:

[0081] A1, the plate corner void area 41 is selected as an isosceles right triangle with a right angle and a side length of 100 mm, and a plate corner void test bottom plate mold 31 is cast according to the plate corner void area 41.

[0082] A2, concrete is poured into the plate corner void test bottom plate mold 31, and after curing and molding, a plate corner void test bottom plate 40 for constructing the plate corner void area 41 is obtained.

[0083] A3, the base 1 with the baffle 12 is fixed to the horizontal ground, and the base 1 is adjusted to be in a horizontal position.

[0084] A4, before the plate corner void test specimen 34 is molded, a 3 mm thick steel plate is used to make a preset crack one 35 with a depth of 5 mm.

[0085] A5, the plate corner void test bottom plate 40 is placed in the groove 9, and then the plate corner void test specimen 34 is placed on the plate corner void test bottom plate 40.

[0086] A6, the first sliding rail 2, the second sliding rail 3, the top plate 4 and the drop hammer 15 are fixed by connecting the first plate corner void positioning bolt hole 19, the second plate corner void positioning bolt hole 20, the third plate corner void positioning bolt hole 21 and the fourth plate corner void positioning bolt hole 22 through the bolt one 5, the bolt two 6, the bolt three 7 and the bolt four 8, so that the impact hammer 15 is in the same plane as the preset crack one 35.

[0087] A7, the latch 18 is inserted through the first circular ring 16 at the lower end of the impact frame top plate and the second circular ring 17 at the upper end of the drop hammer, and the height of the drop hammer 15 is fixed.

[0088] A8, by pulling out the latch 18, the drop hammer 15 is allowed to do free fall motion and hit the plate corner void test specimen 34, and the impact number n1 is recorded, and the crack depth h1 at this time is also recorded.

[0089] A9, then steps A7 and A8 are repeated until visible cracks appear on the upper surface of the plate corner void test specimen 34, and the impact number n 初1 at this time is recorded; steps A7 and A8 are continuously repeated until the plate corner void test specimen 34 is completely broken along the preset crack one 35, and the final impact number n 终1 is recorded; and the impact energy consumed by the plate corner void test specimen 34 is calculated according to the energy method.

[0090] A10, the plate corner void test bottom plate 40 is taken out, the plate corner void test specimen 34 is placed in the groove, and steps A8 and A9 are repeated to obtain the impact energy consumed by the plate corner void test specimen 34 in a non-void state.

[0091] A11, the impact number n and the crack depth h are fitted by formula (1) to obtain the crack depth-impact number curve:

[0092] h=a+bn+cn 2 (1)

[0093] In the formula: h is the crack depth, n is the impact number; a, b, c are constant terms, which are adjusted according to different condition factors. Among them, |2cn 终1 +b| represents the average increase of crack depth per impact, which reflects the accumulation speed of internal damage of the voided specimen under impact load. |2cn 终1 +b| is defined as the impact damage factor, |2cn 终1 +b| is larger, the faster the damage of the voided specimen accumulates with the increase of impact number, and vice versa. That is, |2cn 终1 +b| is smaller, the better the impact resistance of the voided specimen.

[0094] A12, calculate the cumulative damage, the calculation method is as follows:

[0095]

[0096] In the formula: M is the impact damage accumulation factor, n1 is the impact number, n 终1 is the final impact number.

[0097] A13, the toughness improvement rate I 终 of concrete is used to evaluate the toughness improvement of concrete in the void state, and the calculation method is as follows:

[0098]

[0099] In the formula, W 终，脱空，纤维 is the impact energy consumed by the fiber-reinforced concrete specimen in the void state when it is finally cracked, with the unit of J; W 终，非脱空，纤维 is the impact energy consumed by the fiber-reinforced concrete specimen in the non-void state when it is finally cracked, with the unit of J; W 终，脱空，素 is the impact energy consumed by the concrete specimen without fiber in the void state when it is finally cracked, with the unit of J; W 终，非脱空，素 is the impact energy consumed by the concrete specimen without fiber in the non-void state when it is finally cracked, with the unit of J; I 终 is the toughness improvement rate of concrete in the void state, with the unit of %.

[0100] A14, the impact resistance toughness of the voided specimen is determined by combining the impact damage accumulation factor M and the toughness improvement rate I 终 of concrete in the void state. The judgment criteria are as follows: if W素 <W 纤维 This indicates that the impact damage factor of this type of fiber-reinforced concrete accumulates slowly, and the addition of fibers exhibits a positive hybridization effect; if W 素 =W 纤维 This indicates that the accumulation rate of impact damage factor in this type of fiber-reinforced concrete is consistent with that of plain concrete, and the addition of fibers and mixing with concrete have no effect; if W 素 >W 纤维 This indicates that the impact damage factor of this type of fiber-reinforced concrete accumulates slowly, and the addition of fibers exhibits a negative hybrid effect. 终 ≤20% indicates that the addition of this type of fiber has little effect on improving the toughness of concrete; if it is 20%... 终 ≤50% indicates that the addition of this type of fiber has a certain effect on improving the toughness of concrete; if I 终 The percentage is >50%, indicating that the addition of this type of fiber greatly improves the toughness of concrete.

[0101] Example 2:

[0102] The impact toughness test of the cement pavement slab under void condition was carried out using the above-mentioned test evaluation device, including the following steps:

[0103] B1. According to Embodiment 1, disconnect the first bolt 5, the second bolt 6, the third bolt 7 and the fourth bolt 8 from the first corner positioning bolt hole 19, the second corner positioning bolt hole 20, the third corner positioning bolt hole 21 and the fourth corner positioning bolt hole 22.

[0104] B2, select a rectangle with dimensions of 100mm*300mm for the plate edge void area, and cast the plate edge void test base plate mold 33 according to the plate edge void area 43.

[0105] B3. Concrete is poured into the mold 33 for the test base plate of the slab edge void, and after curing, the test base plate 42 for the slab edge void area 43 is obtained.

[0106] B4. Before forming the test specimen 36 for the plate edge detachment test, a 5mm deep pre-set crack 37 is made using a steel plate with a thickness of 3mm.

[0107] B5. Fix the base 1 with baffle 12 on a horizontal surface and adjust the base 1 to a horizontal position.

[0108] B6. Place the plate edge detachment test base plate 42 into the groove 9, and then place the plate edge detachment test specimen 36 on the plate edge detachment test base plate 42.

[0109] ​B7, the first slide rail 2, the second slide rail 3, the top plate 4 and the drop hammer 15 are fixed by connecting the first plate edge void positioning bolt hole 23, the second plate edge void positioning bolt hole 24, the third plate edge void positioning bolt hole 25 and the fourth plate edge void positioning bolt hole 26 through the first bolt 5, the second bolt 6, the third bolt 7 and the fourth bolt 8, so that the impact hammer 15 is in the same plane as the second preset crack 37.

[0110] B8, the height of the drop hammer 15 is fixed by passing the bolt 18 through the first circular ring 16 at the lower end of the impact frame top plate and the second circular ring 17 at the upper end of the drop hammer.

[0111] B9, by pulling out the bolt 18, the drop hammer 15 is allowed to do free fall motion and hit the plate edge void test specimen 36, recorded as one n2, and the crack depth h2 at this time is also recorded.

[0112] B10, then repeat steps B8, B9 until visible cracks appear on the upper surface of the plate edge void test specimen 36, and record the number of impacts n 初2 at this time; continue to repeat steps B8, B9 until the plate edge void test specimen 36 is completely broken along the second preset crack 37, and record the final number of impacts n 终2 ; the impact energy consumed by the plate edge void test specimen 36 is calculated according to the energy method.

[0113] B11, the plate edge void test bottom plate 42 is removed, the plate edge void test specimen 36 is placed in the groove, and steps B8, B9 are repeated to obtain the impact energy consumed by the plate edge void test specimen 36 in the non-void state.

[0114] B12, the impact number n and the crack depth h are fitted by using formula (1) to obtain the crack depth-impact number curve; the judgment principle is referred to step A11.

[0115] B13, the impact damage cumulative factor is calculated according to formula (2).

[0116] B14, the concrete toughness improvement rate I 终 is evaluated to improve the toughness of the concrete in the void state, and the calculation formula is according to formula (3).

[0117] B15, finally, the impact damage cumulative factor M and the concrete toughness improvement rate I 终 in the void state are combined to determine the impact toughness of the void specimen.

[0118] Example three:

[0119] The plate edge void impact test is carried out by using the impact toughness device of the application, which comprises the following steps:

[0120] C1, according to embodiment one, remove the connection of the first bolt 5, the second bolt 6, the third bolt 7 and the fourth bolt 8 with the first plate corner void positioning bolt hole 19, the second plate corner void positioning bolt hole 20, the third plate corner void positioning bolt hole 21 and the fourth plate corner void positioning bolt hole 22.

[0121] C2, select the plate void area as a rectangle with a size of 100mm*100mm, and cast the plate void test base plate mold 35 according to the plate void area 45.

[0122] C3, pour concrete into the plate void test base plate mold 35, and after curing and forming, obtain the plate void test base plate 44 for constructing the plate void area 45.

[0123] C4, before the plate void test specimen 38 is formed, make a preset crack 39 with a depth of 5mm using a steel plate with a thickness of 3mm.

[0124] C5, fix the base 1 with the baffle 12 to the horizontal ground, and adjust the base 1 to be in a horizontal position.

[0125] C6, place the plate void test base plate 44 into the groove 9, and then place the plate void test specimen 38 on the plate void test base plate 44.

[0126] C7, fix the first sliding rail 2, the second sliding rail 3, the top plate 4 and the drop hammer 15 by connecting the first bolt 5, the second bolt 6, the third bolt 7 and the fourth bolt 8 with the first plate void positioning bolt hole 27, the second plate void positioning bolt hole 28, the third plate void positioning bolt hole 29 and the fourth plate void positioning bolt hole 30, so that the impact hammer 15 is in the same plane as the third preset crack 39.

[0127] C8, pass the latch 18 through the first circular ring 16 at the lower end of the impact frame top plate and the second circular ring 17 at the upper end of the drop hammer, and fix the height of the drop hammer 15.

[0128] C9, by pulling out the latch 18, make the drop hammer 15 do free fall motion, and hit the plate void test specimen 38, record the impact number n1, and record the crack depth h3 at this time.

[0129] C10, then repeat steps C8 and C9 until visible cracks appear on the upper surface of the plate void test specimen 38, and record the impact number n 初3 , continue to repeat steps C8 and C9 until the plate void test specimen 38 is completely broken along the third preset crack 39, and record the final impact number n 终3 ; calculate the impact energy consumed by the plate void test specimen 38 according to the energy method.

[0130] C11, take out the bottom plate 44 of the plate void test, place the plate void test specimen 38 in the groove, repeat steps C8, C9, and obtain the impact energy consumed by the impact of the plate void test specimen 38 in the non-void state.

[0131] C12, use formula (1) to fit the impact number n and the crack depth h to obtain the crack depth-impact number curve; the judgment principle refers to step A11.

[0132] C13, calculate the impact damage cumulative factor, the calculation method is according to formula (2).

[0133] C14, use the concrete toughness improvement rate I 终 to evaluate the toughness improvement of the concrete in the void state, the calculation method is according to formula (3).

[0134] C15, finally combine the impact damage cumulative factor M and the concrete toughness improvement rate I 终 in the void state to determine the impact toughness of the void specimen.

Claims

1. A method for evaluating the impact resistance of a toughened cement panel, wherein, The anti-impact toughness detection device comprises a base, an impact frame, a drop hammer, a bottom plate positioning structure, an impacted test piece positioning structure, a void test simulation structure and a preset crack structure, the impact frame comprises two slide rails and a top plate, and the top plate is arranged on the upper part of the slide rails; A plurality of bolt holes are arranged on the base, and the slide rails are fixed on the base on the horizontal ground through bolts; The impacted test piece positioning structure is composed of four baffle plates and six universal balls, the upper end of the drop hammer and the lower end of the top plate are provided with annular rings connected with the latch, and the drop hammer is movably connected with the top plate through the latch; the drop hammer is arranged directly above the preset crack structure; The bottom plate positioning structure comprises a groove arranged on a bottom plate and the bottom plate, and the bottom plate is placed in the groove; The drop hammer is a pentahedron steel drop hammer with a circular arc bottom; The impacted test piece positioning structure is composed of four baffle plates vertically welded on the base, four side universal balls and two top universal balls, and the universal balls and the plane of the impact plate are kept with a small gap; The void test simulation structure comprises a corner void test simulation structure, an edge void test simulation structure and a middle void test simulation structure; The corner void test simulation structure comprises a corner void test bottom plate mold and a corner void test bottom plate, the corner void test bottom plate is obtained by pouring and curing ordinary concrete in the corner void test bottom plate mold, and a void area is artificially manufactured on the corner void test bottom plate; The edge void test simulation structure comprises an edge void test bottom plate mold and an edge void test bottom plate, the edge void test bottom plate is obtained by pouring and curing ordinary concrete in the edge void test bottom plate mold, and a void area is artificially manufactured on the edge void test bottom plate; The middle void test simulation structure comprises a middle void test bottom plate mold and a middle void test bottom plate, the middle void test bottom plate is obtained by pouring and curing ordinary concrete in the middle void test bottom plate mold, and a void area is artificially manufactured on the middle void test bottom plate; The preset crack structure comprises a corner void test piece preset crack, an edge void test piece preset crack and a middle void test piece preset crack, and the preset cracks are completed during the manufacturing of the test pieces; The method comprises the following steps: S1, test piece forming, a void test bottom plate is prepared by using a designed void test bottom plate mold, and a crack with a width of 2 mm and a depth of 3 mm is preset on a steel plate during the manufacturing of the void test piece; S2, test piece installation, the prepared void test bottom plate is placed on the base, then the void test piece is placed on the void test bottom plate, and the position of the void test piece is adjusted to make the void test piece flush with the side surface of the void test bottom plate; S3, drop hammer position setting, the drop hammer is installed according to the required void scene of the test, and it is ensured that the drop hammer can accurately impact the preset crack when falling; S4, impact test, the drop hammer is lifted to a set height, the latch is pulled out, the drop hammer performs free fall to impact the test piece, and the crack depth h of the test piece after impact is recorded; the above operation is repeated, and the impact number n of the test piece when the test piece is completely broken along the preset crack and the crack depth h of the test piece after each impact are recorded. S5, the impact number n and crack depth h are fitted, and the crack depth-impact number curve is obtained, and the expression is as follows: Wherein, a, b, c are constant terms; S6, calculate the cumulative damage, the calculation method is as follows: , wherein is the cumulative factor of impact damage, n is the number of impacts, is the final number of impacts; is the impact damage factor; S7, the toughness improvement rate of concrete in the state of void The toughness improvement of concrete in the state of void is evaluated, and the calculation method is as follows: In the formula, is the impact energy consumed by the toughened concrete test piece at the final cracking in the void state, in J. E is the impact energy consumed by the toughened concrete specimen at the end of the test, in J; E is the impact energy consumed by the non-toughened concrete specimen in the hollow state at the final cracking, in J; is the impact energy consumed by the non-toughened concrete specimen in the non-void state when the specimen is finally cracked, and the unit is J; is the toughness improvement rate of the concrete in the void state, and the unit is ; Finally, the impact damage cumulative factor M and the increase rate of concrete toughness under the condition of void are combined The impact toughness of the voided specimen is determined, and the criteria are as follows: If , it shows that the impact damage factor of the toughened concrete accumulates slowly, and the addition of the external material presents a positive hybrid effect. If , it shows that the impact damage factor accumulation rate of the toughened concrete is consistent with that of plain concrete, and the addition of the external material and the hybrid of the concrete have no effect; If , it shows that the impact damage factor of the toughened concrete accumulates slowly, and the addition of the external material presents a negative hybrid effect. If , it is shown that the toughness of concrete is not improved by adding this kind of material. If , it is shown that the toughness of the concrete is improved by the addition of the material. If , it is shown that the toughness of the concrete is greatly improved by the addition of this kind of admixture.

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