Ancient building outer wall repairing process

Abstract

The invention belongs to the technical field of ancient building repair construction, and relates to an ancient building outer wall repair process which at least comprises the following steps of S1, outer wall state inspection, S2, working table top building and old wall surface cleaning, S3, performance comparison test on new and old wall bricks, S4, new brick type selection, S5, material preparation, S6, leveling and paying off, S7, ash mixing, S8, new brick masonry, S9, seam repairing, S10, seam hooking and S11, protective coating painting. According to the technology, in the brick selecting link, through detection of the flexural and compressive strength of the bricks and calculation of discreteness and the like, the bricks are strictly tested and screened, the repaired outer wall is high in strength and good in bearing performance, the technology almost has no damage to the original outer wall, the original state of the ancient building can be restored to the maximum extent, and the materials and the like can be close to those of the original wall surface; the consistency of the appearance of the ancient building bare brick wall built by the new bricks and the original appearance of the wall body is improved, and the ancient building repair concept of'repairing old as before 'is fully met.

Description

Technical Field

[0001] The present invention belongs to the technical field of ancient building restoration construction, and specifically relates to a restoration process for the exterior walls of ancient buildings. Background Art

[0002] Among the existing ancient buildings in China, there are many ancient buildings that use fair-faced brick walls as the house walls or courtyard walls. The walls usually adopt brick laying methods such as plum blossom joints, one stretcher bond, three stretcher bonds, full head and full stretcher, and one head and one tile. In ancient buildings, the fair-faced brick walls have different uses compared to modern buildings. In the antique design of modern buildings, the load-bearing mainly relies on the load-bearing columns cast with steel bars and concrete, while the fair-faced brick walls mainly play a decorative role. However, in ancient buildings, in addition to being decorative, the fair-faced brick walls also serve as the main load-bearing members. Therefore, the strength of the brick walls is particularly important. However, due to the long-term erosion of rainwater and weathering, some of the outer wall bricks of ancient building fair-faced brick walls have serious problems such as cracks, severe weathering, peeling off, etc., which not only affect the stability and load-bearing capacity of the fair-faced brick walls themselves, but also greatly reduce the aesthetic degree of the fair-faced brick walls.

[0003] In the prior art, there are also methods for repairing and laying bricks on the basis of the original fair-faced brick walls. For example, a method for repairing and constructing ancient building fair-faced brick walls disclosed in the Chinese patent with the publication number CN111042570B repairs the fair-faced brick walls by combining modern technical means on the basis of the original fair-faced brick walls, and uses steel reinforcement cages and spraying strengthening agents to increase the strength of the walls. However, this method causes greater damage to the original brick walls and increases the difficulty of secondary repair. Ancient building restoration requires more attention to restoring the original appearance as much as possible, and needs to ensure the consistency between the repaired exterior wall and the original wall to the greatest extent. Therefore, there is an urgent need for a restoration process for the exterior walls of ancient buildings that can ensure the strength and stability of the repaired walls while causing the least damage to the original wall and meeting the load-bearing requirements of ancient building fair-faced walls. Summary of the Invention

[0004] To solve or partially solve the problems existing in the related art, the present application provides a restoration process for the exterior walls of ancient buildings. Through modern detection and calculation, the selection of materials is strictly selected, and at the same time, the entire bricklaying process hardly causes any damage to the original exterior wall. The repaired exterior wall not only has high strength and good load-bearing performance, but also improves the consistency between the appearance of the ancient building fair-faced brick wall after the new bricks are laid and the original appearance of the wall, fully meeting the ancient building restoration concept of "restoring the original appearance as much as possible".

[0005] The first aspect of the present application provides a restoration process for the exterior walls of ancient buildings, which at least includes the following steps:

[0006] S1: Inspection of the exterior wall state to determine the area to be repaired: Conduct an investigation on the exterior walls of ancient buildings, and record the mortar joint thickness, brick laying method, type of wall bricks, and degree of damage.

[0007] S2: Scaffold erection on the work surface and cleaning of the old wall: Erect a scaffold as the work surface at the repair point determined in S1. Chisel and remove the severely damaged and non-retainable waste old bricks according to the tools required at the determined repair point. Blow and clean the chiseled surface, and reserve several old bricks for later use. At the same time, measure and calculate the area of the wall to be repaired with a tape measure;

[0008] S3: Performance comparison test of new and old wall bricks: According to the investigation results in step S1, take the reserved old bricks and the new bricks to be selected, and conduct performance comparison tests on the new and old wall bricks respectively, and record the results;

[0009] S4: Selection of new bricks: According to the comparison and measurement results in S2, select the type of new bricks, and calculate the quantity of new bricks according to the area of the external wall to be repaired recorded in the S1 investigation and the size of the selected new brick type;

[0010] S5: Material preparation: According to the type and quantity of new bricks selected in S3, select the bricks, and prepare the bricklaying tools and masonry materials. The masonry materials shall at least include: mortar, protective coating;

[0011] S6: Levelling and setting out: Determine the elevation of each brick layer on the masonry foundation surface. The elevation shall be flush with the elevation of the original brick surface. Set up a bricklayer's pole to control the number of brick courses and level with mortar or fine aggregate concrete, and drive positioning nails. One bricklayer's pole shall be set up on each of the left and right sides of the surface to be masoned. The bricklayer's pole is marked with the thickness of each brick course and mortar joint. Pull a guideline between the bricklayer's poles and calibrate and adjust it with the elevation value measured by a level;

[0012] S7: Mix mortar: Mix mortar for later use;

[0013] S8: Laying new bricks: Select new bricks according to the cleaning condition of the chiseled surface in step S2. With the assistance of the guideline indicated in step S6, use cement mortar / mixed mortar to lay the new bricks at the position where the old bricks were chiseled out: Among them, for the position of the whole severely damaged and non-retainable waste old bricks, use complete new bricks for bricklaying. For the defective section of the available old bricks that are partially intact and can be retained for a section, use a cutting machine and a brick grinding machine to cut and grind the new bricks according to the site conditions, and then carry out bricklaying. Glue is applied to bond the chiseled surface of the old bricks and the cut surface of the new bricks;

[0014] S9: Repair joints:

[0015] Pull a line to open joints: Align and correct the large deviation of the bricks out of line by pulling a line. The horizontal joints that are uneven and blind joints shall also be levelled by pulling a line;

[0016] Repair joints: Repair the bricks with corners chipped off and the vertical joints of the bricks out of line. Apply glue into the corners chipped off, and press and polish the surface with a brick surface;

[0017] After completing the repair of open joints and repair of joints, remove the mortar, slurry and sundries adhered to the wall surface;

[0018] S10: Hook and joint the seams: Prepare the jointing mortar. Wet the wall surface with water before jointing, and then use a jointing trowel to hook and joint the mortar joints to ensure that the horizontal and vertical joints are flush.

[0019] S11: Paint the protective coating: Spray and paint the protective coating on the outer surface of the wall tiles after the masonry is completed.

[0020] Optionally, in some solutions, in step S3, the comparison indicators of the performance comparison test include the flexural strength, and new bricks with a larger flexural strength are preferably selected.

[0021] Optionally, in some solutions, in step S3, the specific steps of the flexural strength comparison test are as follows:

[0022] Select 3 - 5 groups of new bricks of different types, with at least 5 specimens in each group. Conduct group numbering and individual specimen numbering respectively.

[0023] Draw a longitudinal center line on the upper surface of the three groups of specimens and extend it to the front and back surfaces to facilitate checking whether the pressure rod is properly positioned during the test. Mark the points on the lower edges of the front and back surfaces of the specimens that contact the flexural test supports to facilitate checking whether the specimens are properly positioned during the test.

[0024] Place the flexural test supports on the loading plate of the testing machine, and then place the specimens between the two support rods on the flexural test supports. Adjust the position so that the upper center line of the specimen coincides with the center line of the testing machine. Place a steel rod, i.e., the pressure rod, at the upper center line of the specimen so that the center line of the pressure rod coincides with the pressure center of the testing machine. Apply the load uniformly until the testing machine starts to display readings, and then immediately stop applying the load. Use a scale to measure whether the position of the specimen is displaced and whether the pressure rod is centered. After ensuring that there are no errors, proceed to the next step.

[0025] Apply the load uniformly until the specimen fails, record the maximum failure load P, and take a photo of the specimen after the test for record.

[0026] Optionally, in some solutions, in step S3, the flexural strength calculation model is as follows:

[0027]

[0028] In the formula:

[0029] f z is the flexural strength of the specimen, P is the maximum failure load of the specimen, L is the axial distance between the two support rods of the flexural test supports, B is the width of the specimen, and H is the height of the specimen.

[0030] Optionally, in some solutions, in step S3, the comparison indicators of the performance comparison test also include the compressive strength, and new bricks with a larger compressive strength are preferably selected.

[0031] Optionally, in some solutions, in step S3, the specific steps of the compressive strength ratio test are as follows:

[0032] Select 3-5 groups of new bricks of different types, with at least 5 specimens in each group of new bricks. Conduct grouping numbering and single-specimen numbering respectively.

[0033] Place the specimen on the bearing plate of the testing machine. Adjust the position so that the upper center of the specimen coincides with the center line of the testing machine. Apply load at a constant speed until the testing machine starts to display readings, then immediately stop applying load and clear the data to prepare for formal loading. Apply load at a constant speed until the specimen fails. Record the maximum failure load F and the load-displacement change of the specimen during the loading process. Take photos of the specimen after the test.

[0034] Optionally, in some solutions, in step S3, the compressive strength calculation model is as follows:

[0035]

[0036] In the formula:

[0037] f c Is the compressive strength, F is the maximum failure load, L is the length of the specimen, and B is the width of the specimen.

[0038] Optionally, in some solutions, in step S3, if the strength difference after calculating the flexural and compressive strengths between two groups of specimens is within the range of 0.1-0.2, it is also necessary to introduce the coefficient of variation to analyze and calculate the strength discreteness of the specimens. When selecting new bricks, preferentially select the new bricks with the lowest discreteness as the replacement new bricks.

[0039] Optionally, in some solutions, the strength discreteness calculation model is as follows:

[0040]

[0041] In the formula:

[0042] δ is the coefficient of variation, s is the standard deviation, f is the average value of the strength, and f i The strength of a single specimen.

[0043] Optionally, in some solutions, in step S8, the glue used for caulking is a mixed solution of epoxy resin and curing agent, and the mixing volume ratio of epoxy resin and curing agent is 2:1.

[0044] Optionally, in some solutions, the protective coating in step S11 is a water repellent.

[0045] Advantages of this application:

[0046] In the brick selection process of this technology, strict tests and screenings are carried out on bricks through the detection of the flexural and compressive strengths of bricks and calculations of discreteness, etc. The repaired exterior wall not only has high strength and good load-bearing performance, but also the entire masonry process mainly improves the strength of the ancient building's exterior wall through brick selection. Compared with the method of adding a steel bar skeleton inside the original exterior wall in the prior art, this technology causes almost no damage to the original exterior wall, and can restore the original state of the ancient building to the greatest extent. Even the materials, etc. can be close to the original wall surface, improving the consistency between the appearance of the fair-faced brick wall of the ancient building after new brick repair and the original appearance of the wall, fully conforming to the concept of ancient building restoration of "repairing as if it were new".

[0047] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0049] Figure 1 is a schematic process flow diagram in an embodiment of this application;

[0050] Figure 2 is a schematic structural diagram of a testing machine in a flexural test in an embodiment of this application;

[0051] Figure 3 is a schematic structural diagram of a testing machine in a compressive test in an embodiment of this application.

[0052] In the figure, 1, testing machine; 2, testing machine hydraulic rod; 3, pressure rod; 4, flexural test support; 5, support rod; 6, testing machine bearing plate; 7, specimen. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] The following will further describe in detail the specific embodiments of this application in conjunction with the drawings and embodiments. The following embodiments are used to illustrate this application, but are not used to limit the scope of this application. Similarly, the following embodiments are only some embodiments of this application rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

[0054] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0055] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0056] In the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0058] In the present invention, terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0059] In the prior art, during the repair construction of an ancient building's fair-faced brick wall where the wall body is basically in good condition and only some wall bricks are severely weathered and need to be replaced, for the wall bricks where only one section is damaged and the other section is intact and can be retained, the method of chiseling the whole brick and replacing it with a new brick is also adopted. Such a repair construction method has problems such as a large amount of chiseling work, high labor intensity, waste of the original wall bricks in the other section with good masonry state, and easy damage to the wall stability and original appearance of the fair-faced brick wall.

[0060] In view of the above problems, this application makes improvements and innovations and proposes the following embodiments.

[0061] As Figure 1 shown, the first aspect of this application provides a repair process for the exterior wall of an ancient building, which at least includes the following steps:

[0062] S1: Exterior wall condition inspection to determine the area to be repaired: Conduct an investigation on the exterior wall of the ancient building, and record the mortar joint thickness, brick laying method, wall brick type, and damage degree.

[0063] S2: Scaffold erection for the workbench surface and old wall cleaning: Erect a scaffold at the repair point determined in S1 as the workbench surface, chisel out the severely damaged and unusable old bricks according to the tools used at the determined repair point, blow and clean the chiseled surface, and reserve several old bricks for use. At the same time, measure with a tape measure and calculate the area of the wall surface to be repaired.

[0064] S3: Performance comparison test on new and old wall bricks: According to the investigation results in step S1, take the reserved old bricks and the new bricks to be selected, and conduct performance comparison tests on the new and old wall bricks respectively, and record the results.

[0065] S4: Selection of new bricks: According to the comparison and determination results in S2, select the type of new bricks, and calculate the number of new bricks based on the area of the exterior wall to be repaired recorded in S1 and the size of the selected new brick type.

[0066] S5: Material preparation: Select and prepare bricks according to the type and quantity of new bricks determined in S3, and prepare bricklaying tools and masonry materials. The masonry materials shall at least include: mortar and protective coating.

[0067] S6: Levelling and setting out lines: Determine the elevation of each brick layer on the masonry foundation surface. The elevation shall be flush with the original brick surface elevation. Set up a building level rod to control the number of brick courses and level with mortar or fine aggregate concrete, and drive positioning nails. One building level rod shall be set up on each of the left and right sides of the surface to be masoned. The building level rod shall be marked with the thickness of each brick course and mortar joint. Pull a reference line between the building level rods and calibrate and adjust it with the elevation value measured by a level.

[0068] S7: Mortar mixing: Prepare mortar for use. The masonry mortar shall have high adhesiveness, good workability, water retention and strength. The sand shall be screened, with a mud content not exceeding 5%, a consistency of 70 - 90 mm, and a segregation not exceeding 20 mm. Cement mortar and cement - lime mortar shall be used up within 3 h and 4 h respectively. When the highest temperature during construction exceeds 30 °C, they shall be used up within 2 h and 3 h respectively after being mixed. If bleeding occurs in the mortar before masonry, it shall be remixed. Mortar exceeding the above - specified time limit shall not be used and shall not be remixed for use.

[0069] S8: New brick masonry: Select new bricks according to the chiseled surface cleaning condition in step S2. With the assistance of the reference line indicated in step S6, use cement mortar / cement - lime mortar to mason the new bricks to the positions where the old bricks have been chiseled out: Among them, for the positions of the discarded old bricks that are severely damaged as a whole and cannot be retained, use intact new bricks for masonry. For the defective sections of the available old bricks that are partially intact and can be retained for a certain length, cut and polish the new bricks according to the site conditions with a cutting machine and a brick grinding machine, and then carry out masonry. Apply glue to bond the chiseled surface of the old bricks and the cut surface of the new bricks. During the masonry process, the fullness of the horizontal mortar joint shall not be less than 90%, and the fullness of the vertical mortar joint shall not be less than 80%. Transparent joints and blind joints shall not occur.

[0070] S9: Joint repair:

[0071] Opening joints by pulling a line: Use a line to level and align the large deviation of the bricks out of line. For uneven horizontal joints and blind joints, also use a line to level. For the mortar joints with too shallow scribing or missed scribing during wall masonry, use a flat drill or a bricklayer's knife to chisel out the joints, with the depth controlled within 12 - 14 mm, and clean them up.

[0072] Repairing joints: Repair the bricks with corners chipped off and the vertical joints of the bricks out of line. Apply glue to the corners chipped off and press and polish the surface with a brick face.

[0073] After completing the opening and repairing of joints, remove the mortar, slurry and sundries adhered to the wall surface.

[0074] S10: Hook and point the joints: Prepare the jointing mortar. Before pointing the joints, moisten the wall surface with water, and then use a jointing trowel to hook and point the mortar joints to ensure that the horizontal joints and vertical joints are flush. The pointed horizontal joints and vertical joints should have the same depth, be aligned horizontally and vertically, be required to be dense and smooth, the joints at the intersections should be flat, the external corners should be square, and there should be no phenomena such as through joints, blind joints, or missing joints up and down at the internal corners.

[0075] S11: Paint the protective coating: Spray and brush the protective coating on the exterior surface of the wall bricks after the masonry is completed.

[0076] In the brick selection step of this process, through the detection of the flexural and compressive strength of bricks and calculations such as discreteness, strict testing and screening of bricks are carried out. The repaired exterior wall not only has high strength and good load-bearing performance, but also the entire masonry process mainly improves the strength of the exterior wall of ancient buildings through brick selection. Compared with the method of adding a steel bar skeleton inside the original exterior wall in the prior art, this process hardly causes any damage to the original exterior wall and can restore the original state of ancient buildings to the greatest extent. Even the materials can be close to the original wall surface, improving the consistency between the appearance of the fair-faced brick wall of ancient buildings after the new bricks are masoned and the original appearance of the wall, fully meeting the ancient building restoration concept of "repairing as if it were new".

[0077] In some embodiments, in step S3, the comparison indexes of the performance comparison test include flexural strength, and new bricks with a larger flexural strength are preferably selected.

[0078] The specific steps of the flexural strength comparison test are as follows:

[0079] Select 3 - 5 groups of different types of new bricks, with at least 5 specimens in each group. In this embodiment, 3 groups of new bricks are preferably selected, with 5 specimens in each group. The size of the new bricks is 100*40*40. Group numbers and single-specimen numbers are respectively assigned:

[0080] Table 1-1 Grouping and numbering of specimens for flexural test

[0081]

[0082] As Figure 2 shown, draw a longitudinal center line on the upper surface of the three groups of specimens and extend it to the front and back surfaces to facilitate checking whether the pressure rod 3 is placed correctly during the test. Mark the points on the lower edges of the front and back surfaces of specimen 7 that contact the flexural test supports to facilitate checking whether specimen 7 is placed correctly during the test;

[0083] Place the flexural test support 4 on the bearing plate 6 of the testing machine, then place the specimen between the two support rods 5 on the flexural test support 4. Adjust the position to make the upper center line of the specimen coincide with the center line of the hydraulic rod 2 of the testing machine. Place a steel rod, namely the pressure rod 3, at the upper center line of the specimen, and make the center line of the pressure rod 3 coincide with the pressure center of the testing machine 1. Apply the load at a uniform speed of 50 N / s until the testing machine starts to display the readings, and then immediately stop applying the load. Use a scale to measure whether there is any displacement at the position of the specimen 7 and whether the pressure rod 3 is centered. After ensuring that there are no errors, proceed to the next step;

[0084] Apply the load at a uniform speed of 100 N / s until the specimen 7 fails, record the maximum failure load P, and take a photo of the specimen after the test for record.

[0085] According to the test parameters, calculate the flexural strength. The flexural strength calculation model is as follows, accurate to 0.01 MPa:

[0086]

[0087] In the formula:

[0088] f z is the flexural strength of the specimen, P is the maximum failure load of the specimen, L is the axial distance between the two support rods of the flexural test support, B is the width of the specimen, and H is the height of the specimen.

[0089] After calculation, the flexural strength results of the specimens are shown in Table 1-2:

[0090] Table 1-2 Flexural test results

[0091]

[0092]

[0093] Analysis of test results: According to the calculation results in Table 1-2, the flexural strength of the new bricks in Group A is significantly higher than that of the new bricks in the other two groups. Therefore, the new bricks in Group A can be selected as the replacement bricks.

[0094] As Figure 3 shown, in some embodiments, in step S3, the comparison indicators of the performance comparison test further include the compressive strength, and it is preferred to select the new bricks with a larger compressive strength.

[0095] The specific steps of the compressive strength comparison test are as follows:

[0096] Select 3-5 groups of different types of new bricks, with at least 5 specimens in each group. In this embodiment, 3 groups of new bricks are preferably selected, with 5 specimens in each group. The size of the new bricks is 80*80*200. Conduct group numbering and single-specimen numbering respectively:

[0097] Table 2-1 Grouping and numbering of specimens for compressive test

[0098]

[0099] Place the test piece on the bearing plate 6 of the testing machine, adjust the position so that the upper center of the test piece 7 coincides with the center line of the hydraulic rod 2 of the testing machine, apply a load at a uniform speed of 50 N / s until the testing machine 1 starts to display readings, then immediately stop applying the load and zero the data to prepare for formal loading. Apply a load at a uniform speed of 400 N / s until the test piece fails, record the maximum failure load F and the load-displacement change of the test piece during the loading process, and take pictures of the test piece after the test for recording.

[0100] According to the test parameters, calculate the compressive strength. The compressive strength calculation model is as follows, accurate to 0.01 MPa:

[0101]

[0102] In the formula:

[0103] f c is the compressive strength, F is the maximum failure load, L is the length of the test piece, and B is the width of the test piece.

[0104] Table 2-1 Compressive Test Results

[0105]

[0106] Analysis of test results: According to the calculation results in Table 2-2, the flexural strength of the new bricks in Group D is significantly higher than that of the other two groups of new bricks. Therefore, the new bricks in Group D can be selected as the replacement bricks.

[0107] In some embodiments, in step S3, if the difference in flexural and compressive strength between two groups of test pieces is within the range of 0.1 - 0.2 after calculation, then the coefficient of variation needs to be introduced to analyze and calculate the strength discreteness of the test pieces. When selecting new bricks, the new bricks with the lowest discreteness are preferentially selected as the replacement new bricks.

[0108] The strength discreteness calculation model is as follows:

[0109]

[0110] In the formula:

[0111] δ is the coefficient of variation, s is the standard deviation, the average value of the strength, f i the strength of a single test piece.

[0112] In the compressive test, the difference in compressive strength calculation between Group D and Group E is 0.2. Therefore, further strength discreteness calculations need to be performed on the compressive data of the new bricks in Group D and Group E. The calculation results are as follows:

[0113]

[0114] According to the calculated standard deviation and coefficient of variation analysis, the discreteness of the new bricks in group D is significantly lower, indicating that the new bricks in group D have better performance and group D is preferred as replacement bricks.

[0115] Advantages of selecting new bricks by strength discreteness:

[0116] By analyzing the discreteness of strength, we can see that the lower the discreteness, the more evenly the force is transmitted between bricks. When subjected to external forces, such as when a building is hit or settles unevenly, the stress will be evenly transmitted to the entire wall for distribution, and will not be concentrated in certain bricks or brick joints, making the wall have better earthquake resistance.

[0117] If the strength discreteness of bricks is too high, the overall strength of the wall will be limited. Compared with continuous building materials (such as integrally cast reinforced concrete), the overall strength of brick structures with high discreteness is lower. Because bricks are mainly bonded by mortar, this bonding force is relatively weak when subjected to large tension and shear forces. By selecting new bricks with low discreteness, the overall strength of the walls of the restored ancient buildings can be higher and the load-bearing performance can be better.

[0118] Brick structures with high discreteness have more gaps. Even if cement mortar is used to fill the brick joints during the masonry process, these gaps may still become channels for rainwater or groundwater to leak over time, due to the aging of materials and the settlement and deformation of buildings. In rainy areas, since the gaps between bricks are not well sealed, rainwater may penetrate into the interior through the exterior wall, causing problems such as mold on the wall and damage to the decorative layer. By choosing bricks with lower discreteness, the risk of water seepage and collapse can be reduced.

[0119] The high discreteness of bricks makes their surfaces and brick joints more easily exposed to the natural environment, thus being subject to various erosions. For example, acidic gases such as carbon dioxide and sulfur dioxide in the air can react chemically with calcium hydroxide (cement hydration product) in brick joints, resulting in a decrease in the performance of brick joint materials. At the same time, in an environment with high humidity, microorganisms such as mold are also prone to breed in brick joints, causing damage to bricks and bonding materials. In the long run, this environmental erosion will weaken the integrity of the brick structure and reduce the service life of the building. By choosing bricks with lower discreteness, this risk can be reduced.

[0120] The discreteness is high, and the operation accuracy requirements for workers during the construction process are relatively high. To ensure that the bricks are arranged neatly, the brick joint widths are consistent, and the mortar is full, skilled technical workers are required. If these factors cannot be well controlled during the construction process, quality problems are likely to occur. For example, too wide brick joints will lead to a decrease in the strength and waterproof performance of the wall, while too narrow brick joints may prevent the mortar from being fully filled, also affecting the wall quality. Selecting bricks with lower discreteness can reduce the safety hazard problems caused by construction errors of workers.

[0121] In some embodiments, in step S8, the glue used for caulking is a mixed solution of epoxy resin and curing agent, and the mixing volume ratio of epoxy resin to curing agent is 2:1. Since the epoxy resin molecule contains polar epoxy groups and hydroxyl groups, these functional groups enable it to form chemical bonding or physical adsorption with the surfaces of various materials. Therefore, the adhesive prepared by mixing epoxy resin and curing agent has good bonding performance. At the same time, the cured epoxy resin has high hardness, strength, and toughness. In addition, epoxy resin has good tolerance to many chemical substances and can avoid being eroded by chemical substances. Therefore, the adhesive prepared by mixing epoxy resin and curing agent can improve the bonding strength between the chiseled surface of the old brick and the cut surface of the new brick, and prevent it from affecting the strength of the entire wall.

[0122] In some embodiments, the protective coating in step S11 is a water repellent, preferably a silane-based water repellent. The water repellent can undergo physical or chemical reactions on the surface of building materials to form a continuous, low-surface-energy waterproof film, reducing the water absorption of the materials and playing a good waterproof role. At the same time, the low-surface-energy characteristic of the water repellent can not only prevent water but also prevent the attachment of stains, keeping the wall clean for a long time.

[0123] Finally, it should also be noted that although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention, and all of them should be included in the protection scope of this application.

Claims

1. A process for repairing the exterior wall of an ancient building, characterized in that: At least the following steps are included: S1: Check the condition of the exterior wall and determine the area to be repaired: Inspect the exterior wall of the ancient building and record the thickness of the mortar joints, the brick arrangement method, the type of wall bricks and the degree of damage; S2: Construction of work surface and cleaning of old wall: Build a scaffold as a work surface at the point to be repaired determined in S1, chisel out the old bricks that are too damaged to be retained according to the tools used at the point to be repaired, blow and clean the chiseled surface, and take some old bricks for backup. At the same time, use a tape measure to measure and calculate the area of ​​the wall to be repaired; S3: Performing a performance comparison test on the new and old wall tiles: According to the survey results of step S1, take the spare old bricks and the new bricks to be selected, perform a performance comparison test on the new and old wall tiles respectively, and record the results; S4: Selection of new bricks: Based on the comparative measurement results of S2, select the new brick type, and calculate the number of new bricks based on the area of ​​the exterior wall to be repaired and the size of the selected new brick type recorded in the S1 survey; S5: Material preparation: According to the type and quantity of new bricks selected in S3, select bricks, and prepare repair tools and masonry materials. The masonry materials at least include: mortar and protective coating; S6: Leveling and laying out: Determine the elevation of each brick layer on the foundation surface, which should be flush with the elevation of the original brick surface. Set up a number of poles to control the number of brick layers and use mortar or fine stone concrete for leveling. Then drive in positioning nails. Set up a number of poles on each side of the surface to be built. The thickness of each brick layer and mortar joint is marked on the number of poles. Draw a reference line between the number of poles and calibrate and adjust the elevation value measured by the level. S7: Mixing mortar: Mixing mortar for later use; S8: New brick laying: According to the cleaning condition of the chiseled surface in step S2, new bricks are selected, and with the help of the guideline indication in step S6, cement mortar / mixed mortar is used to lay the new bricks to the position where the old bricks are chiseled off: for the position of the abandoned old bricks that are severely damaged and cannot be retained, complete new bricks are used for repair; for the position of the defective section of the partially intact old bricks that can be retained, a cutting machine and a brick grinder are used to cut and grind the new bricks according to the on-site conditions, and then repair and lay, and the chiseled surface of the old brick and the cut surface of the new brick are glued; S9: Seam repair: Pull the thread to open the seam: Use the thread to align the large deviation of the thread, and the uneven horizontal seams and blind seams should also be leveled by pulling the thread; Seam repair: The vertical seams of bricks with missing edges and corners and loose edges should be repaired, glue should be applied to the missing edges and corners, and the surface should be polished; After completing the seam repair and caulking, remove the mortar, mud and debris bonded to the wall surface; S10: Grouting: Prepare the grouting agent, wet the wall surface with water before grouting, and then use the grouting trowel to grout the mortar joints to ensure that the horizontal and vertical joints are flush; S11: Paint protective coating: spray protective coating on the exterior surface of the completed wall tiles.

2. The ancient building exterior wall repair process according to claim 1, characterized in that: In step S3, the comparison index of the performance comparison test includes flexural strength, and new bricks with greater flexural strength are preferably used.

3. The ancient building exterior wall repair process according to claim 2 is characterized in that: In step S3, the specific steps of the flexural strength comparison test are as follows: Select 3-5 groups of new bricks of different types, with at least 5 test pieces in each group, and number them in groups and single test pieces respectively; Draw the longitudinal center line on the upper surface of the three groups of specimens and extend it to the front and rear surfaces to check whether the pressure rod is aligned during the test. Mark the contact points with the flexural test support on the lower edges of the front and rear surfaces of the specimens to check whether the specimens are aligned during the test. Place the flexural test support on the pressure plate of the testing machine, then place the specimen between the two support bars on the flexural test support, adjust the position so that the upper center line of the specimen coincides with the center line of the testing machine, place a steel bar, i.e., a pressure bar, at the upper center line of the specimen, so that the center line of the pressure bar coincides with the pressure center of the testing machine, apply load at a uniform speed until the testing machine starts to display the degree, then stop applying load immediately, use a ruler to measure whether the specimen position is dislocated and whether the pressure bar is centered, and proceed to the next step after ensuring that everything is correct; Apply load at a uniform speed until the specimen fails, record the maximum failure load P, and take photos of the specimen after the test.

4. The ancient building exterior wall repair process according to claim 3 is characterized by: In step S3, the flexural strength calculation model is as follows: Where: f z is the flexural strength of the specimen, P is the maximum destructive load of the specimen, L is the axial distance between the two supporting rods of the flexural test support, B is the width of the specimen, and H is the height of the specimen.

5. A process for repairing the exterior wall of an ancient building according to any one of claims 1 to 4, characterized in that: In step S3, the comparison index of the performance comparison test includes compressive strength, and new bricks with greater compressive strength are preferably used.

6. The ancient building exterior wall repair process according to claim 5, characterized in that: In step S3, the specific steps of the compressive strength comparison test are: Select 3-5 groups of new bricks of different types, with at least 5 test pieces in each group, and number them in groups and single test pieces respectively; Place the specimen on the pressure plate of the testing machine and adjust the position so that the upper center of the specimen coincides with the center line of the testing machine. Apply load at a uniform speed until the testing machine starts to display the degree, then stop applying load and clear the data to prepare for formal loading. Apply load at a uniform speed until the specimen is destroyed. Record the maximum destruction load F and the load-displacement changes of the specimen during the pressurization process, and take photos of the specimen after the test.

7. The ancient building exterior wall repair process according to claim 6, characterized in that: In step S3, the compressive strength calculation model is as follows: Where: f c is the compressive strength, F is the maximum failure load, L is the length of the specimen, and B is the width of the specimen.

8. The ancient building exterior wall repair process according to claim 7 is characterized in that: In step S3, if the strength difference between the two groups of specimens is within the range of 0.1-0.2 after the flexural and compressive strengths are calculated, it is necessary to introduce the coefficient of variation to analyze and calculate the strength discreteness of the specimens. When selecting new bricks, the new bricks with the lowest discreteness are preferentially selected as replacement new bricks.

9. The ancient building exterior wall repair process according to claim 8, characterized in that: The intensity discreteness calculation model is as follows: Where: δ is the coefficient of variation, s is the standard deviation, f is the mean value of the intensity, and f i Strength of a single specimen.

10. The ancient building exterior wall repair process according to claim 1, characterized in that: In step S8, the glue used for gluing is a mixture of epoxy resin and curing agent, and the mixing volume ratio of epoxy resin to curing agent is 2:1.

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