A carbonization depth compensation correction method for long-age brick-concrete structure rebound detection and reinforcement application

Abstract

The present application belongs to the technical field of building structure reinforcement reconstruction, and particularly relates to a carbonization depth compensation correction method for rebound detection of long-age brick-concrete structure and reinforcement application. The method comprises the following steps: layer-by-layer polishing and recording the polishing depth of the concrete member measuring area; performing rebound detection on the polished surface to obtain an average rebound value; and selecting a one-dimensional strength measurement curve or a standard strength measurement curve containing carbonization depth to calculate the strength estimated value according to the comparison result of the polishing depth and the carbonization saturation threshold. Based on the detected concrete, brick and mortar strength, the axial compressive bearing capacity and the aseismic shearing bearing capacity of the original masonry wall are calculated. When the bearing capacity is insufficient, reinforcement is implemented by adding a reinforced concrete surface layer on both sides, configuring a steel mesh and a tieback. The present application eliminates the surface hardening interference in rebound detection by polishing to remove the carbonization layer, selects a calculation path through threshold comparison to avoid the transmission of carbonization depth measurement error, and uses the detection result for reinforcement parameter checking, thereby improving the detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of building structure reinforcement and renovation technology, specifically involving a carbonation depth compensation and correction method for rebound detection of long-aged brick-concrete structures and its reinforcement application. Background Technology

[0002] The rebound method, due to its non-destructive, efficient, and economical characteristics, is widely used for on-site testing of concrete strength in existing building structures. The current "Technical Specification for Testing the Compressive Strength of Concrete by Rebound Method" (JGJ / T 23-2011) provides a unified strength curve. This curve uses the rebound value and carbonation depth of the concrete specimen as input variables and establishes a strength estimation model through regression analysis. For concrete members with a short age, this curve has good estimation accuracy. In masonry structure testing, existing technology uses the rebound method to test brick strength and the penetration method to test mortar strength, evaluating the masonry's bearing capacity using calculation formulas in the "Code for Design of Masonry Structures." When the evaluation results do not meet safety requirements, double-sided reinforced concrete surface layer reinforcement is typically used to strengthen the masonry walls to improve the structure's axial compressive bearing capacity and seismic shear bearing capacity.

[0003] However, for long-term brick-concrete structures with a service life exceeding 25 years, the aforementioned testing methods have the following drawbacks: First, the carbonation depth of long-term concrete has reached the centimeter level, and the contribution of the carbonation layer hardness to the rebound value tends to saturate. The aforementioned unified strength measurement curve fails to fully consider this long-term evolution law, and direct application will produce systematic bias, leading to an overestimation of strength. Second, the measurement error of carbonation depth is amplified during the strength estimation process, further reducing the accuracy of the test results. Third, the existing testing methods conduct strength tests on concrete, brick, and mortar independently, lacking a direct technical connection with subsequent reinforcement design. The test results are difficult to effectively guide the determination of reinforcement parameters, causing reinforcement design to often rely on empirical values, resulting in over-reinforcement or under-reinforcement. Summary of the Invention

[0004] The purpose of this invention is to provide a carbonation depth compensation and correction method for rebound testing of long-aged brick-concrete structures and its reinforcement application, in order to solve the technical problem that the current rebound method strength curve estimation results are inaccurate and have poor correlation with subsequent reinforcement design because the carbonation depth of concrete components in long-aged brick-concrete structures has far exceeded the conventional range.

[0005] The present invention achieves the above objectives through the following technical solutions: Firstly, this invention proposes a carbonation depth compensation and correction method for rebound testing of long-aged brick-concrete structures, including: The concrete component test area was ground in layers. Phenolphthalein alcohol solution was added during the grinding process. The grinding was stopped when the entire cross-section of the ground surface turned a uniform purple-red color. The grinding depth was recorded. Rebound test was performed on the polished test area surface to obtain the average rebound value; Compare the polishing depth with a preset carbonization saturation threshold: If the grinding depth is greater than or equal to the preset carbonization saturation threshold, the average rebound value is substituted into the univariate strength test curve with the rebound value as the single independent variable to calculate the strength estimate. If the grinding depth is less than the preset carbonization saturation threshold, the average rebound value and the grinding depth are substituted into the standard strength test curve that includes the carbonization depth variable to calculate the estimated strength value. The estimated strength value is output as the compressive strength assessment result after carbonization depth compensation correction; wherein, the carbonization saturation threshold is predetermined based on the critical carbonization depth value when the influence of carbonization depth on the rebound value tends to saturate.

[0006] Furthermore, before performing layered grinding on the test area of ​​the concrete component, the compressive strength of the masonry bricks is tested using the rebound method, and the compressive strength of the masonry mortar is tested using the penetration method. The method for obtaining the average rebound value includes: arranging multiple impact points in each test area, removing multiple maximum and minimum values ​​from the measured rebound values, and calculating the arithmetic mean of the remaining rebound values.

[0007] Furthermore, the method for determining the preset carbonization saturation threshold includes: Prepare standard concrete test blocks with the same strength grade as the concrete component; The test blocks are naturally cured, with the curing period covering the early to late stages of life; The carbonization depth and rebound value of each test block were tested at the preset age, and regression curves of carbonization depth and rebound value as a function of age were plotted. When the carbonization depth growth rate decreases to below a preset rate threshold and the rebound value change rate decreases to below a preset change rate threshold, the corresponding carbonization depth value is determined as the preset carbonization saturation threshold. The early age period is 14-28 days, and the long age period is not less than 540 days. The preset age period includes multiple time points in the early age period and multiple time points in the long age period, and the interval between adjacent preset age periods gradually increases with the increase of age.

[0008] Furthermore, the univariate intensity measurement curve is pre-established in the following manner: Obtain the measured data of rebound value and compressive strength of long-aged concrete specimens with the same mix proportion as the concrete component in the uncarbonated state; Regression analysis was performed on the rebound value and compressive strength to obtain a univariate quadratic function relationship with rebound value as the single independent variable and compressive strength as the dependent variable, which was used as the univariate strength measurement curve. The standard strength test curve that includes the carbonation depth variable is a strength test curve with the average rebound value and carbonation depth as input variables and the estimated value of concrete compressive strength as output variable.

[0009] Furthermore, before comparing the polishing depth with the preset carbonization saturation threshold, the process also includes: Obtain the design strength grade and service life of the concrete component; Based on the design strength grade and service life, the theoretical carbonization depth range of the component is estimated. If the lower limit of the theoretical carbonization depth range is greater than the preset carbonization saturation threshold, the grinding depth comparison step is skipped, and the average rebound value is substituted into the univariate strength measurement curve to calculate the estimated strength value.

[0010] Secondly, the present invention proposes a method for reinforcing long-term brick-concrete structures, wherein the long-term brick-concrete structure comprises concrete components tested by the above method, and the method includes: Obtain the estimated strength value of the concrete member obtained by the above method; The compressive strength of the bricks and the compressive strength of the mortar in the long-term brick-concrete structure were tested. Based on the estimated strength of the concrete component, the compressive strength of the masonry bricks, and the compressive strength of the masonry mortar, calculate the axial compressive bearing capacity and seismic shear bearing capacity of the original masonry wall. When the axial compressive bearing capacity is lower than the first preset percentage of the design target value, or the seismic shear bearing capacity is lower than the second preset percentage of the design target value, the original structure is deemed to have insufficient bearing capacity. When it is determined that the original structure's load-bearing capacity is insufficient, reinforcement parameters are determined, and the masonry wall to which the concrete component belongs is reinforced according to the reinforcement parameters.

[0011] Furthermore, the rebound method was used to test the bricks in the original masonry wall, and the estimated strength of the bricks was calculated based on the conversion relationship between the rebound value and the compressive strength. ; Testing the compressive strength of masonry mortar in long-term brick-concrete structures includes: The penetration method was used to test the horizontal mortar joints in the original masonry wall to obtain the penetration depth value. After removing the maximum and minimum values, the arithmetic mean of the remaining penetration depth values ​​is taken as the representative penetration depth. , Based on the representative value of penetration depth The conversion relationship between mortar strength and compressive strength yields the estimated mortar strength value. ; Estimated value based on brick strength and mortar strength estimate Calculate the average axial compressive strength of the masonry. As shown in the following formula: ; in, This represents the influence coefficient of masonry type and construction method on masonry strength. This is a coefficient related to the type of masonry. The coefficient representing the influence of mortar strength on masonry strength; Based on the average axial compressive strength of the masonry Calculate the design value of the seismic shear strength of the original masonry wall. As shown in the following formula: ; in, The normal stress influence coefficient for masonry strength is the average compressive stress of the horizontal section generated based on the design value of the permanent load. Sure, N is the design value of permanent load, A m This is the cross-sectional area of ​​the original masonry wall.

[0012] Furthermore, determining the reinforcement parameters includes: Based on the axial compressive bearing capacity and seismic shear bearing capacity of the original masonry wall, as well as the preset design target value, a set of reinforcement parameters is initially selected. The reinforcement parameters include the thickness of the reinforced concrete surface layer, the reinforcement ratio of the steel mesh, and the spacing of the tie bars. The theoretical axial compressive bearing capacity of the original masonry wall after applying the initially selected reinforcement parameters is verified according to the following formula: ; Where N is the design value of the axial pressure after reinforcement. f is the stability coefficient of an axially compressed member. m A represents the design value of the compressive strength of the original masonry wall. m This represents the cross-sectional area of ​​the original masonry wall. The concrete strength utilization coefficient, To add a design value for the axial compressive strength of concrete, The cross-sectional area of ​​the newly added concrete surface layer, This is the steel reinforcement strength utilization coefficient. To add a design value for the compressive strength of the vertical reinforcement, This refers to the cross-sectional area of ​​the newly added vertical reinforcing bars in the compression zone; After verifying the theoretical seismic shear capacity of the original masonry wall using the initially selected reinforcement parameters according to the following formula, ; in, This refers to the seismic shear bearing capacity of the original masonry wall. To improve the load-bearing capacity after reinforcement with a reinforced concrete surface layer, This is the seismic adjustment coefficient for bearing capacity; If both of the above inequalities are satisfied, the currently selected reinforcement parameters will be determined as the final reinforcement parameters; if either inequality is not satisfied, the selected reinforcement parameters will be adjusted and recalculated until both inequalities are satisfied.

[0013] Furthermore, reinforcement is carried out according to the reinforcement parameters, including: According to the determined thickness of the reinforced concrete surface layer, a reinforced concrete surface layer is added on both sides of the masonry wall to which the concrete component belongs. According to the determined steel mesh reinforcement ratio, a steel mesh is arranged in the reinforced concrete surface layer; According to the determined tie bar spacing, tie bars are used to anchor the newly added reinforced concrete surface layer to the original masonry wall, so that the new surface layer and the original wall share the load.

[0014] Furthermore, the aforementioned We obtain it from the following formula: ; in, To add a design value for the axial tensile strength of concrete, denoted as , where b is the steel reinforcement strength utilization coefficient, ' is the concrete surface layer thickness, and 'h' is the horizontal length of the wall. This represents the design strength value of the horizontal reinforcement. s represents the cross-sectional area of ​​a single row of horizontal reinforcing bars, and s represents the spacing between the horizontal reinforcing bars. The Calculate according to the following formula: = , = ; in, This represents the design value of seismic shear strength for failure of the original masonry along the stepped cross-section. This represents the net cross-sectional area of ​​the original masonry wall. The normal stress influence coefficient for masonry strength. The design value of the shear strength of the original masonry, the Determined based on the average compressive stress of the horizontal section generated by the design value of the permanent load.

[0015] The beneficial effects of this invention are as follows: 1. This invention removes the carbonation layer through grinding, allowing rebound testing to be performed directly on the uncarbonized concrete surface. The measured rebound value reflects the intrinsic hardness of the material, rather than the contribution of the carbonation layer. By comparing the grinding depth with the carbonation saturation threshold, different calculation paths are selected: when carbonation is saturated, a univariate curve is used directly, avoiding the measurement of carbonation depth; when carbonation is unsaturated, a standard curve is still used. This approach eliminates the need to measure carbonation depth in the calculation, thus removing the influence of carbonation depth measurement errors on the results.

[0016] 2. This invention directly uses the tested concrete strength, brick strength, and mortar strength to calculate the bearing capacity of the original masonry wall, and uses the calculation results as input for the verification of reinforcement parameters. The determination of reinforcement parameters does not rely on empirical values, but is achieved through repeated adjustments and verifications using the bearing capacity verification formula until the design requirements are met. The test data plays a practical role in the reinforcement design; they are not two separate tasks. Attached Figure Description

[0017] Figure 1 This is a flowchart of the carbonization depth compensation and correction method of Embodiment 1 of the present invention; Figure 2 This is the flowchart of the reinforcement application method for long-term brick-concrete structures in Embodiment 2 of the present invention; Figure 3 The curve showing the change in carbonation depth of C20 concrete with age in Example 1 of this invention is used to determine the carbonation saturation threshold. Figure 4 The curve showing the change in carbonation depth of C30 concrete with age in Example 1 of this invention is used to verify the law that the influence of carbonation depth on rebound value tends to saturate. Figure 5 The curve showing the change in rebound value of C20 concrete with age in Example 1 of this invention is used to establish a univariate strength measurement curve. Figure 6 The curve showing the change in rebound value of C30 concrete with age in Example 1 of this invention is used to establish a univariate strength measurement curve. Figure 7 This is a schematic diagram of the stress on the wall before reinforcement in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the stress on the wall after reinforcement in Embodiment 2 of the present invention. Detailed Implementation

[0018] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0019] It is worth noting that the long-term brick-concrete structures targeted by this invention have a service life exceeding 25 years, and the carbonation depth of the concrete components has reached the centimeter level, with the contribution of the carbonation layer hardness to the rebound value approaching saturation. While the brick strength in the masonry structure remains largely at the original design level, the strength of the masonry mortar has severely degraded, becoming a major weak link in structural safety.

[0020] Example 1

[0021] Please refer to 1. This embodiment proposes a carbonation depth compensation and correction method for rebound testing of long-aged brick-concrete structures, including: S1: Layered grinding is performed on the test area of ​​the concrete component. Specifically, an angle grinder with a diamond grinding disc is used to remove the carbonized layer from the surface of the test area in layers. During grinding, a 1% phenolphthalein alcohol solution is continuously added to the grinding surface. This solution turns purplish-red upon contact with uncarbonized alkaline concrete, but remains unchanged upon contact with carbonized neutral or weakly acidic concrete. The grinding is considered complete when the entire cross-section of the ground surface turns a uniform purplish-red color, indicating that the carbonized layer has been completely removed, exposing the fresh, uncarbonized concrete matrix. The grinding depth is recorded.

[0022] S2: Perform a rebound test on the polished test area surface to obtain the average rebound value.

[0023] For specific testing, an HT-225 rebound hammer can be used. Before use, the rebound hammer should be calibrated on a steel anvil, with a calibration value of 80±2, to ensure the instrument is functioning properly. Sixteen impact points should be evenly distributed in each test area, with a minimum clearance of 20 mm between points, avoiding areas with air pockets, exposed stones, or cracks. From the 16 rebound values, remove the three highest and three lowest values, and calculate the arithmetic mean of the remaining 10 rebound values. This arithmetic mean is taken as the average rebound value Rm for the test area, accurate to 0.1.

[0024] S3: Compare the polishing depth with the preset carbonization saturation threshold: If the grinding depth is greater than or equal to the preset carbonization saturation threshold, it means that the carbonization depth has exceeded the saturation threshold and the contribution of the carbonization layer to the rebound value has become stable. At this time, it is not necessary to measure the carbonization depth for calculation. Instead, the average rebound value is substituted into the univariate strength test curve with the rebound value as the single independent variable to calculate the strength estimate. If the grinding depth is less than the preset carbonization saturation threshold, it means that the carbonization depth has not yet reached saturation, and the carbonization layer still has an impact on the rebound value. It is necessary to consider both the rebound value and the carbonization depth. Then, the average rebound value and the grinding depth are substituted into the standard strength test curve that includes the carbonization depth variable to calculate the estimated strength value.

[0025] The carbonation saturation threshold is predetermined based on the critical carbonation depth at which the influence of carbonation depth on rebound value tends to saturate. As is known to those skilled in the art, for long-aged concrete of grades C20 and C30, when the carbonation depth exceeds 6.0 mm, the contribution of the hardness of the carbonation layer to the rebound value tends to saturate, and the influence of further carbonation on the rebound value is negligible. Therefore, in this embodiment, the preset carbonation saturation threshold can preferably be set to 6.0 mm.

[0026] like Figure 3 The figure shows the carbonation depth of C20 concrete as a function of age in Example 1 of this invention. Figure 3 It can be seen that the carbonation depth of C20 concrete increases rapidly in the early stages, and the growth rate gradually slows down with increasing age. When the carbonation depth exceeds 6.0 mm, the curve tends to flatten out.

[0027] like Figure 4 The figure shows the carbonation depth of C30 concrete as a function of age in Example 1 of this invention. Figure 4 It can be seen that the carbonation depth of C30 concrete also exhibits a pattern of rapid early growth followed by a gradual plateauing in the later stages. Based on Figure 3 and Figure 4 The carbonization depth development pattern shown indicates that when the carbonization depth growth rate decreases below a preset rate threshold, the corresponding carbonization depth value is the carbonization saturation threshold. In this embodiment, the carbonization saturation threshold is preset to 6.0 mm.

[0028] S4: Output the estimated strength value as the compressive strength identification result after carbonization depth compensation correction; wherein, the carbonization saturation threshold is predetermined based on the critical carbonization depth value when the influence of carbonization depth on the rebound value tends to saturate.

[0029] In this embodiment, the univariate intensity measurement curve is pre-established in the following manner: The rebound value and compressive strength of long-aged concrete specimens with the same mix proportion as the concrete component to be tested were obtained in the uncarbonated state. Regression analysis was performed on the rebound value and compressive strength to obtain a univariate quadratic function relationship with rebound value as the single independent variable and compressive strength as the dependent variable.

[0030] In one example, by performing regression analysis on the rebound values ​​and compressive strength of C20 and C30 concrete specimens during the 14-600 day age period, the univariate strength test curve expression is obtained as follows: ; In the formula, This is the estimated compressive strength (MPa) of concrete. This represents the average rebound value. This curve is applicable to concrete components with a service life of over 25 years and whose carbonation depth has exceeded the saturation threshold.

[0031] like Figure 5 The figure shows the curve of the rebound value of C20 concrete changing with age in Example 1 of the present invention. Figure 6 The figure shows the curve of the rebound value of C30 concrete changing with age in Example 1 of the present invention. Figure 5 and Figure 6 It can be seen that the rebound values ​​of C20 and C30 concrete reach a stable plateau after 140-180 days of age, corresponding to the trend of the carbonation depth curve becoming flat. In this embodiment, the above-mentioned univariate strength test curve was obtained by regression analysis of the rebound values ​​and compressive strength of concrete specimens at different ages.

[0032] The standard strength test curve that includes the carbonation depth variable is the unified strength test curve specified in the Technical Specification for Testing the Compressive Strength of Concrete by Rebound Method (JGJ / T 23-2011). This curve uses the average rebound value and carbonation depth as input variables and the estimated value of concrete compressive strength as output variables.

[0033] In a preferred embodiment, before the concrete component test area is ground in layers, the compressive strength of the masonry bricks is tested using the rebound method, and the compressive strength of the masonry mortar is tested using the penetration method.

[0034] Specifically, the compressive strength of masonry bricks is tested using an HT-225 brick rebound hammer. Before use, the surface of the test area must be cleaned with a special grinding wheel to expose a solid, flat, and fresh brick surface. Each test area is hit 5 times, with an interval of more than 20 mm between adjacent test points, avoiding brick joints and edges. The measured rebound value is used to obtain the estimated compressive strength of the brick through the brick strength conversion relationship.

[0035] Specifically, the compressive strength test of masonry mortar was conducted using an SJY800B penetrator. Before use, a special grouting tool was used to clean the surface of the horizontal mortar joints in the test area, removing a loose layer of approximately 10 mm to expose the unweathered mortar interior. Sixteen points were evenly tested in each test area, with a spacing greater than 150 mm, avoiding cracks and defects. The three maximum and three minimum values ​​were removed from the 16 penetration depth values, and the arithmetic mean of the remaining ten penetration depth values ​​was calculated as the representative mortar penetration depth value, dmj. The estimated mortar compressive strength was then calculated according to the strength curve specified in the "Technical Specification for Testing the Compressive Strength of Masonry Mortar by Penetration Method" (JGJ / T 136).

[0036] The method for obtaining the average rebound value includes: setting up multiple impact points in each test area, removing multiple maximum and minimum values ​​from the measured rebound values, and calculating the arithmetic mean of the remaining rebound values.

[0037] In a preferred embodiment, the method for determining the preset carbonization saturation threshold includes: Prepare standard concrete test blocks of the same strength grade as the concrete member. The test blocks should be 150 mm × 150 mm × 150 mm in size, and at least 3 test blocks should be prepared for each age.

[0038] The test blocks were subjected to natural curing, with the curing period covering the early to long age stages. The curing method was covered water curing, which began within 12 hours after the initial setting of the concrete. For ordinary concrete, water was applied every 2 hours, and the curing period was no less than 7 days. For concrete with retarder admixtures, the curing period was no less than 14 days.

[0039] The carbonization depth and rebound value of each specimen were tested at preset curing ages, and regression curves of carbonization depth and rebound value as a function of curing age were plotted. For the carbonization depth test, the specimen was placed in a carbonization chamber with a carbon dioxide concentration of 20%±3%, a temperature of 20℃±2℃, and a relative humidity of 70%±5%. After reaching the preset curing age, the specimen was removed, split perpendicular to the carbonization direction, and a 1% phenolphthalein alcohol solution was sprayed onto the fresh fracture surface. After standing for 30 seconds, the vertical distance of the undiscolored area was measured, which is the carbonization depth value. The rebound value was tested using an HT-225 rebound hammer according to standard methods.

[0040] When the rate of increase in carbonization depth decreases below a preset rate threshold and the rate of change in rebound value decreases below a preset rate threshold, the corresponding carbonization depth value is determined as the preset carbonization saturation threshold. In this embodiment, when the rate of increase in carbonization depth decreases below 10% of the initial rate and the rate of change in rebound value is less than 1%, the corresponding carbonization depth value is the carbonization saturation threshold.

[0041] The early age period is 14-28 days, and the long age period is no less than 540 days. The preset age period includes multiple time points in the early age period and multiple time points in the long age period, and the interval between adjacent preset age periods gradually increases with age. In this embodiment, the preset age periods include 14 days, 28 days, 60 days, 90 days, 180 days, 360 days, 390 days, 420 days, 450 days, 480 days, 540 days, and 600 days. The testing intervals are closer in the early stage (14-90 days) and gradually increase in the later stage (180-600 days) to reflect the pattern of rapid growth in carbonization depth followed by slower growth.

[0042] In a preferred embodiment, before comparing the polishing depth with a preset carbonization saturation threshold, the method further includes: Obtain the design strength grade and service life of concrete components; The theoretical carbonation depth range of the component is estimated based on its design strength grade and service life. For example, for a component made of C20 concrete with a service life of 30 years, its carbonation depth range can be estimated using a carbonation depth-age regression curve. If the lower limit of the theoretical carbonation depth range is greater than the preset carbonation saturation threshold, it indicates that even considering normal fluctuations in carbonation depth, the actual carbonation depth of the component has likely exceeded the saturation threshold. In this case, the grinding depth comparison step is skipped, and the average rebound value is substituted into the univariate strength measurement curve to calculate the estimated strength value. This saves on-site testing time and improves testing efficiency.

[0043] According to the above embodiments, this invention uses physical grinding with phenolphthalein color development to control the endpoint of carbonation layer removal, allowing rebound testing to target the uncarbonated concrete matrix and eliminating the interference of carbonation layer hardness on rebound values. By comparing the grinding depth with the carbonation saturation threshold, it distinguishes whether the carbonation effect has reached saturation and selects different calculation paths: when carbonation is saturated, a univariate curve is used, eliminating the need to measure carbonation depth; when carbonation is unsaturated, a standard curve is used, with the carbonation depth input. This technical architecture avoids the propagation and amplification of carbonation depth measurement errors in strength estimation, achieving compensation and correction for the influence of carbonation depth in long-age concrete rebound testing.

[0044] Example 2

[0045] Please refer to 2. This embodiment proposes a method for strengthening long-term brick-concrete structures, including concrete components tested by the method in Embodiment 1. The method includes: Step A: Obtain the estimated strength value of the concrete member using the method in Example 1; Step B: Test the compressive strength of the bricks and the mortar in the long-term brick-concrete structure; Step C: Calculate the axial compressive bearing capacity and seismic shear bearing capacity of the original masonry wall based on the estimated strength of the concrete members, the compressive strength of the masonry bricks, and the compressive strength of the masonry mortar. Step D: When the axial compressive bearing capacity is lower than the first preset percentage of the design target value, or the seismic shear bearing capacity is lower than the second preset percentage of the design target value, the original structure is deemed to have insufficient bearing capacity. Step E: When it is determined that the original structure's load-bearing capacity is insufficient, determine the reinforcement parameters and reinforce the masonry wall to which the concrete component belongs based on the reinforcement parameters.

[0046] In a preferred embodiment, the rebound test is performed on the bricks in the original masonry wall, and the estimated strength value of the brick is calculated based on the conversion relationship between the rebound value and the compressive strength. ; Testing the compressive strength of masonry mortar in long-aged brick-concrete structures includes: using the penetration method to test the horizontal mortar joints in the original masonry wall and obtaining the penetration depth value. After removing the maximum and minimum values, the arithmetic mean of the remaining penetration depth values ​​is taken as the representative penetration depth. , Based on the representative value of penetration depth The conversion relationship between mortar strength and compressive strength yields the estimated mortar strength value. Preferably, 16 points are tested in each test area, and after removing the 3 maximum values ​​and 3 minimum values, n=10.

[0047] Estimated value based on brick strength and mortar strength estimate Calculate the average axial compressive strength of the masonry. As shown in the following formula: ; in, The coefficient representing the influence of masonry type and construction method on masonry strength is given for sintered common bricks. Take 0.78; For sintered common bricks, the coefficient is related to the type of masonry. Take 0.5; The coefficient representing the influence of mortar strength on masonry strength. ,in This represents the average compressive strength of the mortar (MPa).

[0048] Based on the average axial compressive strength of the masonry Calculate the design value of the seismic shear strength of the original masonry wall. As shown in the following formula: ; in, The normal stress influence coefficient for masonry strength is the average compressive stress of the horizontal section generated based on the design value of the permanent load. Sure, N is the design value of permanent load, A m This is the cross-sectional area of ​​the original masonry wall.

[0049] In a preferred embodiment, determining the reinforcement parameters includes: Based on the axial compressive bearing capacity and seismic shear bearing capacity of the original masonry wall, as well as the preset design target values, a set of reinforcement parameters is initially selected. The reinforcement parameters include the thickness of the reinforced concrete surface layer, the reinforcement ratio of the steel mesh, and the spacing of the tie bars. In one example, the initial selection method is as follows: concrete strength grade is C30, double-sided reinforcement thickness is 60mm on each side, vertical reinforcement is HRB400 grade Φ10@200mm, horizontal reinforcement is HRB400 grade Φ6@200mm, tie bars are Φ8, and the spacing is 600-800mm.

[0050] The theoretical axial compressive bearing capacity of the original masonry wall after applying the initially selected reinforcement parameters is verified according to the following formula: ; Where N is the design value of the axial pressure after reinforcement. f is the stability coefficient of an axially compressed member (determined by referring to a table based on the height-to-thickness ratio and reinforcement ratio of the reinforced section). m A represents the design value of the compressive strength of the original masonry wall. m This represents the cross-sectional area of ​​the original masonry wall. This is the concrete strength utilization coefficient (0.8-0.9 for brick masonry, with a lower value for higher initial stress). The design value for the axial compressive strength of concrete is added (14.3 MPa for C30 concrete). The cross-sectional area of ​​the newly added concrete surface layer (for double-sided reinforcement, it is the sum of the thicknesses on both sides multiplied by the length of the wall). This is the steel reinforcement strength utilization coefficient (taken as 0.8-0.9). The design value for the compressive strength of the added vertical reinforcement is 360MPa (HRB400 grade). This refers to the cross-sectional area of ​​the newly added vertical reinforcing bars in the compression zone; After verifying the theoretical seismic shear capacity of the original masonry wall using the initially selected reinforcement parameters according to the following formula, ; in, This refers to the seismic shear bearing capacity of the original masonry wall. To improve the load-bearing capacity after reinforcement with a reinforced concrete surface layer, The seismic adjustment coefficient for bearing capacity is 0.85. In one example, the initial parameters were substituted into the above formula for calculation: the axial compressive bearing capacity N = 2750KN, which is basically equivalent to the original design value of 2808KN; the seismic shear bearing capacity V = 1143.6KN, which is much greater than the original damaged masonry of 58.2KN, thus meeting the seismic fortification requirements of 7 degrees.

[0051] If both of the above inequalities are satisfied, the currently selected reinforcement parameters will be determined as the final reinforcement parameters; if either inequality is not satisfied, the selected reinforcement parameters will be adjusted and recalculated until both inequalities are satisfied. Adjustment methods include: increasing the surface layer thickness, increasing the concrete strength grade, increasing the diameter of the reinforcing bars or decreasing the spacing of the reinforcing bars, and increasing the density of the tie bars.

[0052] In a preferred embodiment, reinforcement is carried out according to reinforcement parameters, including: According to the determined thickness of the reinforced concrete surface layer, a reinforced concrete surface layer is added on both sides of the masonry wall to which the concrete component belongs; fine stone concrete is used during pouring, the maximum particle size of coarse aggregate is strictly controlled, and it is poured in layers, with the thickness of each layer controlled within 500 mm, and a small immersion vibrator with a diameter of no more than 30 mm is used to compact it.

[0053] According to the determined reinforcement ratio of the steel mesh, steel mesh is configured in the reinforced concrete surface layer; the vertical and horizontal steel bars of the steel mesh are tied at the designed spacing, and the vertical steel bars must form a reliable anchorage with the floor or roof components, and the steel bars are arranged through pre-set holes when penetrating the floor slab.

[0054] According to the determined tie bar spacing, tie bars are used to anchor and connect the newly added reinforced concrete surface layer to the original masonry wall, so that the new surface layer and the original wall share the load. The tie bars are made of steel bars with a diameter of 8 mm. When reinforcing one side, L-shaped tie bars are used and anchored in the masonry wall with an anchoring depth of not less than 120 mm. When reinforcing both sides, S-shaped tie bars are used and installed through the wall in a staggered pattern with a spacing of 800 mm.

[0055] In one preferred embodiment We obtain it from the following formula: ; in, The design value for the axial tensile strength of concrete is added (2.14 MPa for C30 concrete). denoted as the steel reinforcement strength utilization coefficient, b as the concrete surface layer thickness (the sum of the thicknesses on both sides is used for double-sided reinforcement), and h as the horizontal length of the wall. The design strength value for horizontal reinforcement (360MPa for HRB400 grade). s represents the cross-sectional area of ​​a single row of horizontal reinforcing bars, and s represents the spacing between the horizontal reinforcing bars.

[0056] In one example, b = 60mm (the sum of 30mm on each side), h = 3600mm, s = 200mm. =154mm 2 (Single row of horizontal reinforcement on each side), substituting into the formula, we get... =881.21KN.

[0057] Calculate according to the following formula: = , = ; in, This represents the design value of seismic shear strength for failure of the original masonry along the stepped cross-section. This represents the net cross-sectional area of ​​the original masonry wall. The normal stress influence coefficient for masonry strength. This is the design value of the shear strength of the original masonry. Determined based on the average compressive stress of the horizontal section generated by the design value of the permanent load.

[0058] In one example, the net cross-sectional area of ​​the original masonry wall =0.864m 2 , =0.124MPa, calculated as follows =106.9KN (original design value) or =58.2KN (considering mortar degradation).

[0059] like Figure 7 The diagram shown is a schematic representation of the stress on the wall before reinforcement in Embodiment 2 of the present invention. Before reinforcement, the original masonry wall had already generated stress and deformation under the load P1. When the mortar strength degraded, the masonry entered the plastic stage prematurely, and its strength and elastic modulus decreased.

[0060] like Figure 8 The diagram shown illustrates the stress distribution of the wall after reinforcement in Embodiment 2 of the present invention. After reinforcement, the newly added reinforced concrete surface layer is connected to the original masonry wall via tie bars to form a unified structure. Under the added load... Under the influence of the force, the newly added surface layer begins to bear the load, and the original masonry and the newly added surface layer share the load.

[0061] In summary, this embodiment directly uses the estimated concrete strength obtained from Example 1, along with the test results for brick and mortar strength, to calculate the bearing capacity of the original masonry wall. The test data is transmitted unidirectionally to the bearing capacity calculation. The reinforcement parameters are determined using an iterative verification method: parameters are initially selected based on the original structure's bearing capacity and design target values. The axial compressive strength and seismic shear strength formulas are then used to determine if the requirements are met. If not, the parameters are adjusted and recalculated until they are met. The reinforcement parameters are transformed from empirically derived values ​​to mechanically determined values, allowing the test data to play a practical role in the reinforcement design.

[0062] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0063] In addition, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0064] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for carbonation depth compensation and correction in rebound testing of long-aged brick-concrete structures, characterized in that, include: The concrete component test area was ground in layers. Phenolphthalein alcohol solution was added during the grinding process. The grinding was stopped when the entire cross-section of the ground surface turned a uniform purple-red color. The grinding depth was recorded. Rebound test was performed on the polished test area surface to obtain the average rebound value; Compare the polishing depth with a preset carbonization saturation threshold: If the grinding depth is greater than or equal to the preset carbonization saturation threshold, the average rebound value is substituted into the univariate strength test curve with the rebound value as the single independent variable to calculate the strength estimate. If the grinding depth is less than the preset carbonization saturation threshold, the average rebound value and the grinding depth are substituted into the standard strength test curve that includes the carbonization depth variable to calculate the estimated strength value. The estimated strength value is output as the compressive strength assessment result after carbonization depth compensation correction; wherein, the carbonization saturation threshold is predetermined based on the critical carbonization depth value when the influence of carbonization depth on the rebound value tends to saturate.

2. The carbonization depth compensation and correction method according to claim 1, characterized in that, Before performing layered grinding on the test area of ​​the concrete component, the method of rebound testing is used to test the compressive strength of the masonry bricks, and the method of penetration testing is used to test the compressive strength of the masonry mortar. The method for obtaining the average rebound value includes: arranging multiple impact points in each test area, removing multiple maximum and minimum values ​​from the measured rebound values, and calculating the arithmetic mean of the remaining rebound values.

3. The carbonization depth compensation and correction method according to claim 1, characterized in that, The method for determining the preset carbonization saturation threshold includes: Prepare standard concrete test blocks with the same strength grade as the concrete component; The test blocks are naturally cured, with the curing period covering the early to late stages of life; The carbonization depth and rebound value of each test block were tested at the preset age, and regression curves of carbonization depth and rebound value as a function of age were plotted. When the carbonization depth growth rate decreases to below a preset rate threshold and the rebound value change rate decreases to below a preset change rate threshold, the corresponding carbonization depth value is determined as the preset carbonization saturation threshold. The early age period is 14-28 days, and the long age period is not less than 540 days. The preset age period includes multiple time points in the early age period and multiple time points in the long age period, and the interval between adjacent preset age periods gradually increases with the increase of age.

4. The carbonization depth compensation and correction method according to claim 1, characterized in that, The univariate intensity measurement curve is pre-established in the following manner: Obtain the measured data of rebound value and compressive strength of long-aged concrete specimens with the same mix proportion as the concrete component in the uncarbonated state; Regression analysis was performed on the rebound value and compressive strength to obtain a univariate quadratic function relationship with rebound value as the single independent variable and compressive strength as the dependent variable, which was used as the univariate strength measurement curve. The standard strength test curve that includes the carbonation depth variable is a strength test curve with the average rebound value and carbonation depth as input variables and the estimated value of concrete compressive strength as output variable.

5. The carbonization depth compensation and correction method according to claim 1, characterized in that, Before comparing the polishing depth with the preset carbonization saturation threshold, the process also includes: Obtain the design strength grade and service life of the concrete component; Based on the design strength grade and service life, the theoretical carbonization depth range of the component is estimated. If the lower limit of the theoretical carbonization depth range is greater than the preset carbonization saturation threshold, the grinding depth comparison step is skipped, and the average rebound value is substituted into the univariate strength measurement curve to calculate the estimated strength value.

6. A method for reinforcing long-term brick-concrete structures, characterized in that, The long-term brick-concrete structure includes concrete components tested by the method of claim 1, the method comprising: Obtain the estimated strength value of the concrete member obtained by the method described in claim 1; The compressive strength of the bricks and the compressive strength of the mortar in the long-term brick-concrete structure were tested. Based on the estimated strength of the concrete component, the compressive strength of the masonry bricks, and the compressive strength of the masonry mortar, calculate the axial compressive bearing capacity and seismic shear bearing capacity of the original masonry wall. When the axial compressive bearing capacity is lower than the first preset percentage of the design target value, or the seismic shear bearing capacity is lower than the second preset percentage of the design target value, the original structure is deemed to have insufficient bearing capacity. When it is determined that the original structure's load-bearing capacity is insufficient, reinforcement parameters are determined, and the masonry wall to which the concrete component belongs is reinforced according to the reinforcement parameters.

7. The method for reinforcing long-term brick-concrete structures according to claim 6, characterized in that, The rebound method was used to test the bricks in the original masonry wall. Based on the conversion relationship between the rebound value and the compressive strength of the brick, the estimated strength value of the brick was calculated. ; Testing the compressive strength of masonry mortar in long-term brick-concrete structures includes: The penetration method was used to test the horizontal mortar joints in the original masonry wall to obtain the penetration depth value. After removing the maximum and minimum values, the arithmetic mean of the remaining penetration depth values ​​is taken as the representative penetration depth. , Based on the representative value of penetration depth The conversion relationship between mortar strength and compressive strength yields the estimated mortar strength value. ; Estimated value based on brick strength and mortar strength estimate Calculate the average axial compressive strength of the masonry. As shown in the following formula: ； in, This represents the influence coefficient of masonry type and construction method on masonry strength. This is a coefficient related to the type of masonry. The coefficient representing the influence of mortar strength on masonry strength; Based on the average axial compressive strength of the masonry Calculate the design value of the seismic shear strength of the original masonry wall. As shown in the following formula: ； in, The normal stress influence coefficient for masonry strength is the average compressive stress of the horizontal section generated based on the design value of the permanent load. Sure, N is the design value of permanent load, A m This is the cross-sectional area of ​​the original masonry wall.

8. The method for reinforcing long-term brick-concrete structures according to claim 6, characterized in that, Determining the reinforcement parameters includes: Based on the axial compressive bearing capacity and seismic shear bearing capacity of the original masonry wall, as well as the preset design target value, a set of reinforcement parameters is initially selected. The reinforcement parameters include the thickness of the reinforced concrete surface layer, the reinforcement ratio of the steel mesh, and the spacing of the tie bars. The theoretical axial compressive bearing capacity of the original masonry wall after applying the initially selected reinforcement parameters is verified according to the following formula: ； Where N is the design value of the axial pressure after reinforcement. f is the stability coefficient of an axially compressed member. m A represents the design value of the compressive strength of the original masonry wall. m This represents the cross-sectional area of ​​the original masonry wall. The concrete strength utilization coefficient, To add a design value for the axial compressive strength of concrete, The cross-sectional area of ​​the newly added concrete surface layer, This is the steel reinforcement strength utilization coefficient. To add a design value for the compressive strength of the vertical reinforcement, This refers to the cross-sectional area of ​​the newly added vertical reinforcing bars in the compression zone; After verifying the theoretical seismic shear capacity of the original masonry wall using the initially selected reinforcement parameters according to the following formula, ； in, This refers to the seismic shear bearing capacity of the original masonry wall. To improve the load-bearing capacity after reinforcement with a reinforced concrete surface layer, This is the seismic adjustment coefficient for bearing capacity; If both of the above inequalities are satisfied, the currently selected reinforcement parameters will be determined as the final reinforcement parameters; if either inequality is not satisfied, the selected reinforcement parameters will be adjusted and recalculated until both inequalities are satisfied.

9. The method for reinforcing long-term brick-concrete structures according to claim 8, characterized in that, Reinforcement is carried out according to the reinforcement parameters, including: According to the determined thickness of the reinforced concrete surface layer, a reinforced concrete surface layer is added on both sides of the masonry wall to which the concrete component belongs. According to the determined steel mesh reinforcement ratio, a steel mesh is arranged in the reinforced concrete surface layer; According to the determined tie bar spacing, tie bars are used to anchor the newly added reinforced concrete surface layer to the original masonry wall, so that the new surface layer and the original wall share the load.

10. The method for reinforcing long-term brick-concrete structures according to claim 8, characterized in that, The We obtain it from the following formula: ； in, To add a design value for the axial tensile strength of concrete, denoted as , where b is the steel reinforcement strength utilization coefficient, ' is the concrete surface layer thickness, and 'h' is the horizontal length of the wall. This represents the design strength value of the horizontal reinforcement. s represents the cross-sectional area of ​​a single row of horizontal reinforcing bars, and s represents the spacing between the horizontal reinforcing bars. The Calculate according to the following formula: = ， = ； in, This represents the design value of seismic shear strength for failure of the original masonry along the stepped cross-section. This represents the net cross-sectional area of ​​the original masonry wall. The normal stress influence coefficient for masonry strength. The design value of the shear strength of the original masonry, the Determined based on the average compressive stress of the horizontal section generated by the design value of the permanent load.

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