Cold region concrete water flow erosion criterion construction method

Abstract

The invention relates to the field of cold region concrete tests, in particular to a cold region concrete water flow erosion criterion construction method. Comprising the following steps: preparing a test block, and repeatedly performing a freeze-thaw erosion coupling test on the test block; the method comprises the following steps: taking cement paste powder on the surface of an erosion surface before the surface layer of the erosion surface of a test block is peeled off and a freeze-thaw erosion coupling test is executed every time, measuring and calculating the solid-phase calcium content of the cement paste powder obtained every time, and calculating the solid-phase calcium content of the cement paste powder obtained every time after the solid-phase calcium content is stable; taking the percentage of the residual solid-phase calcium content of the test block to the initial solid-phase calcium content as a test block surface neat paste erosion criterion; after the aggregates on the erosion surface of the test block are exposed, the relative convex height of each aggregate on the erosion surface of the test block is obtained before the freeze-thaw erosion coupling test is executed each time; and fitting a relational expression between the relative convex height critical value of the aggregate and the equivalent diameter of the aggregate, and taking the relative convex height critical value of the aggregate obtained according to the relational expression as an aggregate erosion criterion. According to the method, the erosion criterion of the neat paste and the aggregate in the cold region concrete can be established.

Description

Technical Field

[0001] The invention relates to the field of cold region concrete testing, and in particular to a method for constructing a criterion for water erosion of cold region concrete. Background Art

[0002] Frost damage is common and severe in water channels, sluices, bridge piers, dams, and other projects built in cold regions. Concrete cracking, loosening, and erosion are common. Furthermore, under the long-term action of low-speed water flow, the dissolution and erosion of the surface concrete are important factors that accelerate the deterioration of concrete performance and the development of corrosion diseases in freeze-thaw environments. The corrosion process of concrete under the coupled action of freeze-thaw erosion can be summarized into three stages: surface slurry peeling, small stone peeling and large stone leakage, and stable peeling. Figure 1 shown.

[0003] The existing evaluation indicators for the corrosion resistance of cold-region concrete are mainly mass loss rate and dynamic elastic modulus loss rate, which can be used for concrete corrosion resistance design in the design stage, but cannot be used to evaluate the degree of corrosion of concrete on site.

[0004] Considering that concrete surface spalling can be used as an important indicator for durability assessment of existing concrete structures in cold regions, the corrosion process of concrete under freeze-thaw-erosion coupling involves both paste and aggregate. Therefore, it is urgent to establish erosion criteria for both paste and aggregate in concrete under freeze-thaw-erosion coupling. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the existing technology and provide a method for constructing water erosion criterion for cold-region concrete. The method can establish erosion criterion for pure paste and aggregate in cold-region concrete, and then be used for numerical simulation of corrosion diseases of concrete structures such as water channel linings and bridge piers under the coupled action of freeze-thaw and low-speed water erosion.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a method for constructing a criterion for water erosion of concrete in cold regions, comprising:

[0007] include:

[0008] The concrete test block is taken out after being cured to a specified age, and a protective layer is applied to the remaining surfaces except the eroded surface to obtain a test block;

[0009] Repeated freeze-thaw erosion coupling tests were performed on the test blocks. In each freeze-thaw erosion coupling test, the test blocks were first subjected to an indoor accelerated freeze-thaw cycle test equivalent to one year of service under field conditions, followed by a water flow erosion test equivalent to one year of service under field conditions.

[0010] Before the surface slurry of the eroded surface of the test block peels off, and before each freeze-thaw erosion coupling test is performed, cement slurry powder on the eroded surface is collected and the solid phase calcium content of the cement slurry powder obtained each time is measured. After the solid phase calcium content stabilizes, the percentage of the remaining solid phase calcium content of the test block to the initial solid phase calcium content is used as the criterion for the erosion of the surface slurry of the test block;

[0011] After the aggregate on the erosion surface of the test block was exposed, before each freeze-thaw erosion coupling test was performed, the relative convex height of each aggregate in the non-edge area of the erosion surface of the same test block was obtained. The relative convex height is the ratio of the aggregate convex height to its equivalent diameter. The relative convex height of the aggregate before being washed away was used as its relative convex height critical value, and the relationship between the relative convex height critical value of the aggregate and the equivalent diameter of the aggregate was fitted. The relative convex height critical value of the aggregate obtained based on this relationship was used as the aggregate erosion criterion.

[0012] Furthermore, the water erosion test of the test block is carried out based on an erosion test device, which includes a scouring trough, a water tank, a water pipe and a water pump; wherein,

[0013] The trough has a slope section, a buffer section and a horizontal section arranged in sequence; the test block is laid flat on the horizontal section, and each time erosion occurs, the erosion surface is flush with the end of the buffer section; a water pump is connected to a water pipe to pump fluid to the slope section.

[0014] Furthermore, the flushing fluid used in the erosion test device is a 6 mol / L NH4Cl solution.

[0015] Further, the steps for calculating the solid phase calcium content are:

[0016] Grind the cement paste powder and sieve it, take a sample of preset weight and soak it in a NH4Cl solution of preset concentration and stir it until the Ca 2+ After the concentration stabilized, the clarified liquid was extracted and the Ca content of the clarified liquid was measured by EDTA complexometric titration. 2+ Concentration, based on Ca 2+ Calculate the solid phase calcium content.

[0017] Furthermore, the specific steps for obtaining the equivalent diameter of each aggregate on the eroded surface of the test block are as follows:

[0018] The eroded surface of the test block was photographed from above, and each aggregate was marked. The edge line of each aggregate in contact with the mortar was used as a reference, and the area of each aggregate in contact with the mortar was measured and equivalently converted into a circular diameter as the equivalent diameter of the corresponding aggregate.

[0019] Furthermore, the specific steps for obtaining the convex height of each aggregate on the eroded surface of the test block are as follows:

[0020] The eroded surface of the specimen was scanned using a 3D scanner to obtain a 3D topography image. The lowest point of the edge line where the aggregate and the slurry contacted on the 3D topography image was used as a reference, and the point cloud software was used to read the convex height of the aggregate.

[0021] After adopting the above technical solution, the present invention can simulate the long-term low-speed water flow erosion service environment of cold-region concrete, establish the erosion criterion of the net paste and aggregate in cold-region concrete, and then be used for numerical simulation of corrosion diseases of concrete structures such as water channel linings and bridge piers under the coupled action of freeze-thaw and low-speed water flow erosion. Therefore, the surface erosion and spalling conditions of cold-region concrete structures under the action of low-speed water flow can be studied through numerical simulation methods, and the development of their corrosion diseases can be predicted. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of concrete corrosion process under freeze-thaw erosion coupling;

[0023] Figure 2 This is a flow chart of the method for constructing a criterion for water erosion of cold-region concrete according to the present invention;

[0024] Figure 3 This is the structural diagram of the erosion test device;

[0025] Figure 4 Flow chart for sample preparation for solid phase calcium content;

[0026] Figure 5 This is the time-varying regularity diagram of the residual solid phase calcium content on the eroded surface;

[0027] Figure 6 This is the aggregate area map calculated using Image J software;

[0028] Figure 7 The three-dimensional topography image obtained by scanning;

[0029] Figure 8 This is the aggregate convex height map calculated using Cloud Compare software;

[0030] Figure 9 This is the erosion surface diagram of the test piece; Figure 9 (a) is a top view of the eroded surface of the test piece; Figure 9 (b) is the three-dimensional morphology of the eroded surface of the test piece;

[0031] Figure 10 This is a graph showing the relationship between the relative convex height of aggregate and the equivalent diameter of aggregate. DETAILED DESCRIPTION

[0032] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0033] like Figure 2 As shown, a method for constructing a criterion for water erosion of concrete in cold regions includes:

[0034] include:

[0035] The concrete test block is taken out after being cured to a specified age, and a protective layer is applied to the remaining surfaces except the eroded surface to obtain a test block;

[0036] Repeated freeze-thaw erosion coupling tests were performed on the test blocks. In each freeze-thaw erosion coupling test, the test blocks were first subjected to an indoor accelerated freeze-thaw cycle test equivalent to one year of service under field conditions, followed by a water flow erosion test equivalent to one year of service under field conditions.

[0037] Before the surface slurry of the eroded surface of the test block peels off, and before each freeze-thaw erosion coupling test is performed, cement slurry powder on the eroded surface is collected, and the solid phase calcium content of the cement slurry powder obtained each time is measured. After the change in solid phase calcium content with the freeze-thaw erosion coupling test time tends to be stable, the percentage of the remaining solid phase calcium content of the test block to the initial solid phase calcium content is used as the criterion for erosion of the surface slurry of the test block, that is, the criterion for boundary migration of the surface slurry of the test block;

[0038] After the aggregate on the erosion surface of the test block was exposed, before each freeze-thaw erosion coupling test was performed, the relative convex height of each aggregate in the non-edge area of the erosion surface of the same test block was obtained. The relative convex height is the ratio of the aggregate convex height to the equivalent diameter. The relative convex height of the aggregate before being washed away was used as its relative convex height critical value, and the relationship between the relative convex height critical value of the aggregate and the equivalent diameter of the aggregate was fitted. The relative convex height critical value of the aggregate obtained based on this relationship was used as the aggregate erosion criterion.

[0039] It's important to note that in real-world environments, freeze-thaw and scouring occur simultaneously throughout the year. The order of their onset depends on the specific time the project begins service. However, because freeze-thaw is stronger than dissolution-scouring, freeze-thaw is typically used first, followed by scouring. Furthermore, freeze-thaw and scouring occur alternately, with freeze-thaw occurring only for a short period during winter. Therefore, in this example, scouring during freeze-thaw periods is ignored, simplifying the concept to an alternating freeze-thaw and scouring cycle.

[0040] Furthermore, as the paste surrounding the aggregate peels off, the aggregate gradually bulges outward, directly subject to the impact of the water flow. The greater the bulge height, the larger the area impacted by the water flow, and the greater the total impact force acting on the aggregate. However, the area of the aggregate wrapped by the paste decreases with increasing bulge height. Therefore, the greater the bulge height of the aggregate relative to its size, the more susceptible it is to water erosion. Furthermore, freeze-thaw effects primarily manifest themselves in damage and degradation of the interfacial transition zone (ITZ) between the aggregate and the paste. The stronger the freeze-thaw cumulative effect, the more severe the ITZ degradation, and the more susceptible the aggregate is to spalling. Therefore, relative bulge height can be used as a criterion for aggregate erosion in concrete subjected to freeze-thaw-erosion coupling. Generally speaking, spherical aggregates with similar dimensions in three dimensions are the most ideal type of aggregate. Such aggregates are often used in projects with high requirements for concrete quality. Therefore, aggregates with uneven surfaces can be equivalent to spherical shapes. The ratio of the aggregate convex height to the circular equivalent diameter of the aggregate in the top view of the erosion specimen is defined as the relative convex height of the aggregate. In addition, it is reasonable to use the critical value of the relative convex height of the aggregate obtained according to the relationship as the criterion for aggregate erosion.

[0041] In this embodiment, the water erosion test of the test block is carried out based on the erosion test device. Figure 3 As shown, the erosion test device includes an erosion trough, a water tank, a water pipe and a water pump; wherein,

[0042] The trough has a slope section, a buffer section and a horizontal section arranged in sequence; the test block is laid flat on the horizontal section, and each time erosion occurs, the erosion surface is flush with the end of the buffer section (the bottom of the test block is glued, and this height can be easily adjusted when the glue has not solidified. That is, after the erosion surface of the test block is eroded, before the next water erosion test is carried out, the bottom is glued to raise it to make up for the eroded height), ensuring that water flows smoothly through the erosion surface of the test block; the water pump is connected to the water pipe to pump fluid to the slope section. More preferably, the flushing fluid used in the erosion test device is a 6 mol / L NH4Cl solution, including but not limited to other solutions with similar acceleration rates, such as NH4NO3 solution and HNO3 solution.

[0043] In this embodiment, preferably, Figure 4 As shown, the steps for measuring solid phase calcium content are:

[0044] Grind the cement paste powder and sieve it, take a sample of preset weight and soak it in a NH4Cl solution of preset concentration and stir it until the Ca 2+ After the concentration stabilized, the clarified liquid was extracted and the Ca content of the clarified liquid was measured by EDTA complexometric titration. 2+ Concentration, based on Ca 2+ Calculate the solid phase calcium content.

[0045] In this embodiment, preferably, Figure 6As shown in Figure 2, the specific steps for obtaining the equivalent diameter of each aggregate on the eroded surface of the test block are as follows:

[0046] The eroded surface of the test block was photographed from above, and each aggregate was marked. The edge line of each aggregate in contact with the mortar was used as a reference, and the area of each aggregate in contact with the mortar was measured and equivalently converted into a circular diameter as the equivalent diameter of the corresponding aggregate.

[0047] In this embodiment, preferably, Figure 7 、 Figure 8 and Figure 9 As shown in Figure 2, the specific steps for obtaining the convex height of each aggregate on the eroded surface of the test block are as follows:

[0048] The eroded surface of the specimen was scanned using a 3D scanner to obtain a 3D topography image. The lowest point of the edge line where the aggregate and the slurry contacted on the 3D topography image was used as a reference, and the point cloud software was used to read the convex height of the aggregate.

[0049] The technical solutions involved in the above embodiments are described in detail below in conjunction with specific embodiments.

[0050] like Figure 2 As shown, a method for constructing a criterion for water erosion of concrete in cold regions includes: conducting indoor accelerated tests of concrete freeze-thaw and erosion in alternating cycles at intervals of one year under equivalent actual service environments, analyzing and processing the test results, and establishing a criterion for low-speed water erosion (including a criterion for net slurry erosion and a criterion for aggregate erosion).

[0051] Indoor accelerated tests of concrete freeze-thaw and erosion are carried out in alternating cycles at intervals of one year under conditions equivalent to actual service environments. Specifically, the tests include:

[0052] Step S1: After curing the concrete test block to a specified age, take it out, apply epoxy resin to the remaining five surfaces except the erosion surface and dry it in the shade to obtain a test block, ensuring that only the erosion surface is eroded by water flow, reducing the damage to other surfaces of the test block.

[0053] Step S2: Repeatedly perform freeze-thaw erosion coupling test on the test block. The specific process of each freeze-thaw erosion coupling test is as follows:

[0054] Step S21: The test block is subjected to an indoor accelerated freeze-thaw cycle test equivalent to one year of service under a field environment. Based on existing research, the annual field freeze-thaw cycles in Northeast my country, Northwest China, North China, and Central China are set to 120, 118, 84, and 18, respectively. The equivalent conversion ratio between indoor accelerated freeze-thaw cycles and field freeze-thaw cycles is between 1:10 and 1:15, roughly equivalent to 12 freeze-thaw cycles under natural conditions.

[0055] In step S22, the completely thawed test block is secured in the horizontal section of the flushing device. A 6 mol / L ammonium chloride solution is added to the water tank, raising the water level above the pump level. The solution is then transported through the water pipe and into the channel trough. The trough can be constructed from acrylic sheet. Existing research indicates that under static corrosion, the accelerated corrosion rate of 6 mol / L NH4Cl solution on concrete is approximately 200 times, meaning that two days of accelerated corrosion is roughly equivalent to one year of actual service life.

[0056] In step S23, the water pump is started. The solution is pumped through the water pipe and flows into the device. After passing through the ramp and buffer sections, the water flow reaches a steady state, flushing the surface of the test block before flowing into the water tank, completing the water cycle. The flushing flow rate is coordinated by the pump power and the inlet and outlet diameters of the water pipe. Taking the concrete lining of a water channel as an example, the flow rate of the existing water channel is generally below 5 m / s. In the experiments, the flow rates were designed to be 1, 2, 3, 4, and 5 m / s. The methods for achieving these flow rates are shown in Table 1.

[0057] Table 1 Specific parameters of the erosion test device

[0058]

[0059]

[0060] Step S24: After the erosion time equivalent to one year of service under the field environment has been reached, the water pump is turned off, and the freeze-thaw-erosion cycle test is completed. The test block is removed and the next freeze-thaw-erosion cycle is carried out.

[0061] It should be noted that the indoor accelerated freeze-thaw cycle test, which is equivalent to one year of service under the field environment, is a standard test conducted in accordance with GB50082-2024 "Standard Test Method for Long-term Performance and Durability of Ordinary Concrete".

[0062] The specific process of obtaining the criterion for net slurry erosion is as follows:

[0063] The first step is sampling: before the surface slurry of the eroded surface of the test block peels off, and before each freeze-thaw erosion coupling test is performed, a layer of cement slurry powder about 1 mm thick is taken from the surface of the eroded surface of the test block.

[0064] It should be noted that the experimental blocks after sampling did not participate in the subsequent experiments.

[0065] Step 2: Sample preparation: Grind the cement paste powder taken each time thoroughly and sieve it with a 200-mesh sieve. Then, 0.2 g of the sample was immersed in 20 ml of 6 mol / L NH4Cl solution. After sealing, the beaker was placed on a magnetic stirrer and stirred at a low speed until the Ca in the solution 2+After the concentration stabilizes (about 4 days), extract the clarified solution and prepare the sample as follows Figure 4 shown.

[0066] The third step is to calculate the solid phase calcium content: the Ca content in the extracted clarified solution is measured regularly by EDTA complexometric titration. 2+ Concentration. The specific operation method is as follows: use a pipette to take 2mL of the soaking solution and place it in a 500mL beaker, add deionized water to dilute it to 200 times the sample solution, then add 5mL of triethanolamine masking agent, and then add about 20mg of CMP indicator, shake it to dissolve, then add 250g / L KOH solution while stirring, after green fluorescence appears, slowly titrate with EDTA standard solution until the green fluorescence disappears and red appears, stop. 2+ The concentration is calculated as shown in formula (1), based on which the residual solid phase calcium content of the eroded surface is calculated.

[0067]

[0068] Where, Ca in the immersion solution 2+ concentration; 74.08 is the molar mass of Ca(OH)2; v1 is the volume of EDTA standard solution consumed during titration; c is the concentration of EDTA standard solution; V is the volume of the sample to be tested.

[0069] The fourth step is to construct the criterion for net slurry erosion: with the extension of equivalent service life, the residual solid phase calcium content of the erosion surface under the coupling effect of freeze-thaw erosion first decreases and then tends to be stable. When the solid phase calcium content is lower than this stable value, the surface damaged area will be washed away by the water flow. Therefore, this stable value can be used as the criterion for net slurry erosion of channel lining concrete under specific flow rate and freeze-thaw environment. Figure 5 It can be seen that at flow rates of 1, 2, 3, 4, and 5 m / s, when the residual solid calcium content on the eroded surface decreases to 26.4%, 27.3%, 20.8%, 22.2%, and 27.3% of the initial content, respectively, with an average value of about 25%, boundary migration of the slurry on the specimen surface occurs. This average value is then used as the criterion for slurry erosion.

[0070] The specific process of obtaining aggregate erosion criterion is as follows:

[0071] The first step is to take a bird's-eye view of the eroded surface after the aggregates on the eroded surface of the specimen are exposed for the first time and before each freeze-thaw erosion coupling test, mark each aggregate on the specimen surface, and use ImageJ software to obtain the equivalent diameter of each coarse aggregate. The specific process is to first calibrate the size according to the actual scale in the software, and then measure the area of each coarse aggregate based on the edge line where the aggregate contacts the mortar (calibrated according to the turning point visible to the naked eye on the boundary line), such as Figure 6As shown, according to the principle of equal area, it is equivalent to a circle. The diameter of the circle is the equivalent diameter of the aggregate, and the data is recorded.

[0072] The second step is to perform a three-dimensional scan of the eroded surface of the test piece. Specifically, open the DUUMM 3D scanner software, connect the DUUMMV900 3D scanner and the computer, and perform calibration. Before starting the scan, set the appropriate resolution and exposure parameters, and paste the marking points on the surface of the test piece. First, scan the marking points. Stop scanning after all are recognized, switch to scanning laser points, and stop scanning after the outline of the aggregate on the surface of the test piece is clearly visible. The schematic diagram after the scan is completed is as follows Figure 7 shown.

[0073] Step 3: Process the scanned point cloud data. Specifically, delete unnecessary areas and markers; optimize the model to remove isolated points and disconnected items; perform triangulation operations to fill in the markers. Save the model.

[0074] Step 4: In the 3D scan model, take the lowest point of the edge line where the aggregate and mortar meet as the reference, and use software that can recognize 3D images and read dimensional data, such as but not limited to Cloud Compare point cloud software, to read the height of the aggregate protrusion, such as Figure 8 Open the 3D scan image, rotate the model, and adjust the coordinate system so that the coordinate axis is perpendicular to the specimen surface; match each aggregate in the erosion surface image with the 3D scan image, as shown. Figure 8 As shown, the actual convex height of each aggregate is read out.

[0075] in, Figure 9 The top view and three-dimensional morphology of the eroded surface of the same test block are shown below. Figure 9 (a) is a top view of the eroded surface of the test piece; Figure 9 (b) is the three-dimensional morphology of the eroded surface of the test piece.

[0076] Step 5: The ratio of the convex height to the equivalent diameter is defined as the relative convex height of the aggregate (the number of freeze-thaw erosion coupling tests corresponding to the convex height and equivalent diameter remains the same). After the erosion surface becomes stable and coarse aggregates of various particle sizes begin to peel off continuously, a statistical analysis of the relative convex height of the residual aggregate on the erosion surface is performed to establish the aggregate erosion criterion. Specifically:

[0077] Considering the randomness of concrete microstructure and the fact that the flow velocity within 5 m / s has no significant effect on the aggregate spalling process, the flow velocity groups are not subdivided when establishing the aggregate erosion criterion under the coupled effect of freeze-thaw erosion. Figure 10As shown in the figure, each particle size has a relatively obvious convex upper limit, that is, when the convexity of the aggregate is greater than the critical value, the probability of the aggregate being eroded by flowing water after freezing and thawing is very high. Therefore, the upper critical point (blue data point in the figure) is selected for the formulation of the aggregate erosion criterion (the selection strategy is to use the relative convex height obtained last time before the aggregate is eroded as its relative convex height critical value). It should be noted that Figure 10 The black data points in the figure correspond to aggregates that are not washed away during the equivalent service life in the next year.

[0078] Depend on Figure 10 It can be seen that under the coupled effects of freeze-thaw erosion at flow rates of 1 to 5 m / s, the relative convex height of the residual aggregate decreases linearly with increasing aggregate equivalent diameter. This is because the coupling effect is primarily manifested in the degradation of the ITZ, with freeze-thaw being the dominant factor. Therefore, aggregate spalling after freeze-thaw occurs primarily in the early stages of erosion. Large aggregates are typically located at the highest points on the erosion surface and are most affected by the impact of the water flow. According to the fitting equation in the figure, the critical value of the relative convex height of the aggregate decreases from 60% to 30% when the aggregate particle size increases from 4.75 mm to 9.5 mm.

[0079] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for constructing a criterion for water erosion of concrete in cold regions, characterized in that: include: The concrete test block is taken out after being cured to a specified age, and a protective layer is applied to the remaining surfaces except the eroded surface to obtain a test block; Repeated freeze-thaw erosion coupling tests were performed on the test blocks. In each freeze-thaw erosion coupling test, the test blocks were first subjected to an indoor accelerated freeze-thaw cycle test equivalent to one year of service under field conditions, followed by a water flow erosion test equivalent to one year of service under field conditions. Before the surface slurry of the eroded surface of the test block peels off, and before each freeze-thaw erosion coupling test is performed, cement slurry powder on the eroded surface is collected and the solid phase calcium content of the cement slurry powder obtained each time is measured. After the solid phase calcium content stabilizes, the percentage of the remaining solid phase calcium content of the test block to the initial solid phase calcium content is used as the criterion for the erosion of the surface slurry of the test block; After the aggregate on the erosion surface of the test block was exposed, before each freeze-thaw erosion coupling test was performed, the relative convex height of each aggregate in the non-edge area of the erosion surface of the same test block was obtained. The relative convex height is the ratio of the aggregate convex height to its equivalent diameter. The relative convex height of the aggregate before being washed away was used as its relative convex height critical value, and the relationship between the relative convex height critical value of the aggregate and the equivalent diameter of the aggregate was fitted. The relative convex height critical value of the aggregate obtained based on this relationship was used as the aggregate erosion criterion.

2. The method for constructing a criterion for water erosion of concrete in cold regions according to claim 1, characterized in that: The water erosion test of the test block is carried out based on the erosion test device, which includes a scouring trough, a water tank, a water pipe and a water pump; The trough has a slope section, a buffer section and a horizontal section arranged in sequence; the test block is laid flat on the horizontal section, and each time erosion occurs, the erosion surface is flush with the end of the buffer section; a water pump is connected to a water pipe to pump fluid to the slope section.

3. The method for constructing water erosion criterion for cold region concrete according to claim 2, characterized in that: The flushing fluid used in the erosion test device is 6 mol / L NH4Cl solution.

4. The method for constructing water erosion criterion for cold region concrete according to claim 1, characterized in that: The steps for calculating the solid phase calcium content are: Grind the cement paste powder and sieve it, take a sample of preset weight and soak it in a NH4Cl solution of preset concentration and stir it until the Ca 2+ After the concentration stabilized, the clarified liquid was extracted and the Ca content of the clarified liquid was measured by EDTA complexometric titration. 2+ Concentration, based on Ca 2+ Calculate the solid phase calcium content.

5. The method for constructing water erosion criterion for cold region concrete according to claim 1, characterized in that: The specific steps to obtain the equivalent diameter of each aggregate on the erosion surface of the test block are: The eroded surface of the test block was photographed from above, and each aggregate was marked. The edge line of each aggregate in contact with the mortar was used as a reference, and the area of each aggregate in contact with the mortar was measured and equivalently converted into a circular diameter as the equivalent diameter of the corresponding aggregate.

6. The method for constructing water erosion criterion for cold region concrete according to claim 1, characterized in that: The specific steps to obtain the convex height of each aggregate on the eroded surface of the test block are: The eroded surface of the specimen was scanned using a 3D scanner to obtain a 3D topography image. The lowest point of the edge line where the aggregate and the slurry contacted on the 3D topography image was used as a reference, and the point cloud software was used to read the convex height of the aggregate.

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