Alkali-activated concrete salt crystallization erosion test device and test method

Abstract

The application provides a kind of alkali-activated concrete salt crystallization erosion test device and test method, the device includes: test mechanism, including box, hygrodeik, salinometer and salt solution sealed box, saturated salt solution is contained in box and is equipped with first liquid level meter, water inlet and water outlet are arranged on it;Salt solution sealed box is suspended in the box, and corrosion salt solution is contained in it and is equipped with second liquid level meter, sealed box water inlet is arranged on it;Salinometer is used to measure the concentration and pH value of saturated salt solution;Support mechanism includes horizontal rod and suspension rope, one end of suspension rope is connected with horizontal rod, alkali-activated concrete test bar is suspended and fixed to the other end of horizontal rod, alkali-activated concrete test bar is inserted in salt solution sealed box and half soaked in corrosion salt solution;Test mechanism further includes image recording device, for recording the apparent morphology change of test bar in salt crystallization process.The application can more truly restore the salt crystallization process of alkali-activated concrete in natural environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of civil engineering, in particular to a device and method for testing salt crystallization corrosion of alkali-activated concrete. BACKGROUND

[0002] Alkali-activated cementitious materials are cementitious materials mixed by strong alkaline chemicals such as NaOH and Na2SiO3 as activators and fly ash, slag, metakaolin and other pozzolanic active materials or latent hydraulic raw materials as matrix materials. Alkali-activated cementitious materials exhibit good mechanical properties and durability due to their stable hydration products and dense microstructure. At the same time, alkali-activated cementitious materials are considered as green and environmentally friendly materials due to their low carbon emissions during production. In the context of the global goal of achieving "zero carbon emissions by 2050", alkali-activated cementitious materials are likely to partially or completely replace cement and become the most potential building material in the process of constructing concrete structures.

[0003] However, whether the concrete structure is built by ordinary Portland cement or alkali-activated cementitious materials, it is prone to be eroded by salts in the natural service environment, resulting in the production of swelling substances inside the concrete and the destruction of the concrete, and the pulverization and peeling of the concrete surface, ultimately affecting the appearance and performance of the concrete structure. At present, there have been a large number of studies on the resistance of concrete to salt erosion at home and abroad, and relevant test standards and evaluation methods have also been developed. However, most of these evaluation indexes are for chemical salt attack, and there are few studies on physical salt attack (salt crystallization).

[0004] In fact, salt crystallization-induced concrete damage is very common in natural service environment, and the damage is much more serious than chemical attack. However, unfortunately, salt crystallization has been merged into chemical attack for a long time, and the problem of salt crystallization in concrete has not been paid attention to. Until 1990s, foreign scholars began to gradually realize the damage of salt crystallization to concrete. Among them, the representative scholars are Carlos Rodriguez Navarro (1996), George Scherer (1999), David Benavente (2001), Robert J. Flatt (2002), Harvey Haynes (2008), Giovanni Castellazzi (2013) and so on; the representative scholars in China are Yang Quanbing (2007), Ma Kunlin (2007), Deng Dewen (2011) and so on. In 2011, the American Concrete Institute officially classified salt crystallization as physical attack. In recent years, in order to study the salt crystallization attack of ordinary concrete and alkali-activated concrete, a series of tests have been carried out and some achievements have been made. However, there is no uniform test standard for the salt crystallization attack of alkali-activated concrete at home and abroad, and the existing test devices / testing methods have the following problems to be solved:

[0005] Firstly, the contact mode of concrete and salt solution significantly affects the salt crystallization process. The commonly used immersion methods are full immersion, horizontal half immersion and vertical half immersion, etc. Many tests do not use reasonable immersion methods, which leads to the failure to effectively observe the salt crystallization attack phenomenon. Secondly, in order to reduce the test period of salt crystallization attack, dry-wet cycle accelerated test is often used. However, the salt crystallization mode under dry-wet cycle is different from that under capillary adsorption in natural environment, which leads to the test results unable to reflect the real salt crystallization process. Thirdly, some test methods require high-temperature pre-drying treatment of concrete samples, which leads to the microstructure of hydration products in concrete to shrink and produce microcracks, significantly affecting the salt crystallization process. Finally, unlike ordinary concrete, alkali-activated concrete has a very complex salt crystallization process due to its complex chemical composition, and the salt crystallization process is related to many factors such as the type of salt, the concentration of salt, the environmental temperature, the humidity, etc. However, many existing test devices are too complex to safely and effectively control the above influencing factors (such as some devices control the relative humidity by injecting high pressure into the working tank, which will damage the internal structure of concrete), thus making the salt crystallization test results unreliable.

[0006] According to the search, the application publication number CN103217377A of Chinese invention patent discloses a kind of concrete salt corrosion resistance performance rapid determination device and its determination method, its purpose is to accelerate the corrosion process of concrete in salt solution to capture the final state after corrosion, but cannot observe the change of concrete apparent state in salt erosion process in real time;The device does not consider how to regulate the relative humidity in working tank, so it cannot strictly control the important influencing factor of salt erosion process, finally it is not conducive to get reliable test results.In addition, the device fixes the installation mode of concrete test piece and the size of test piece, and the flexibility of applicable scene is not enough.

[0007] The application publication number CN101144807A of Chinese invention patent discloses a kind of concrete salt solution crystallization erosion damage performance test device, which controls the pressure in glass box and visually reads the tube to infer the rate of salt solution into concrete, while the transmission of salt solution in actual concrete is from non-steady state to steady state gradually, and the test method is not accurate enough;And high pressure needs to be injected into the glass box during the test process, which has certain danger, the device is too simple and does not have corresponding safety protection mechanism, and the loss of concentration caused by evaporation of salt solution in working tank is not considered, which can easily cause error of salt crystallization test results.

[0008] The authorized announcement number CN207366416U of Chinese utility model patent discloses a kind of concrete salt crystallization damage performance test device under dry-wet cycle, which is related to high temperature drying and rapid cooling operation of test piece, which can cause the super-saturation of concrete pore solution to rise rapidly, increase the crystallization pressure, damage the microstructure of concrete and affect the precision of salt crystallization test;Salt crystallization process is accelerated by dry-wet cycle, but the salt crystallization mode under dry-wet cycle is different from that under capillary adsorption in natural environment, so it cannot reflect the real salt crystallization process in actual situation.The patent needs to dry concrete sample at high temperature, which can easily cause C-S-H gel shrinkage and microcracks in concrete, and then significantly interfere with salt crystallization process.

[0009] In summary, there is an urgent need for a test device for alkali-activated concrete salt crystallization erosion and a corresponding test method to truly reflect the salt crystallization process of alkali-activated concrete, and to prevent the adverse effects of mechanical properties and durability degradation caused by salt erosion of alkali-activated concrete. SUMMARY

[0010] In view of the defects in the prior art, the purpose of the present application is to provide a test device and method for alkali-activated concrete salt crystallization erosion.

[0011] According to one aspect of the present application, a test device for alkali-activated concrete salt crystallization erosion is provided, which comprises:

[0012] a testing mechanism, comprising a box, a hygrothermograph, a salinometer and at least one sealed salt solution box;

[0013] The box contains saturated salt solution and is provided with a first liquid level gauge for measuring the liquid level of the saturated salt solution. The box is provided with a water inlet and a water outlet, and the water inlet is in communication with a saturated salt solution reservoir. The sealed salt solution box is suspended in the box above the saturated salt solution, contains corrosive salt solution and is provided with a second liquid level gauge for measuring the liquid level of the corrosive salt solution. The sealed salt solution box is provided with a sealed box water inlet in communication with a corrosive salt solution reservoir. The hygrothermograph is arranged inside the box. The salinometer is used to measure the concentration and pH value of the saturated salt solution flowing out of the water outlet.

[0014] A support mechanism, comprising a horizontal rod and a suspension rope. The horizontal rod is horizontally arranged inside the box and fixedly connected to the inner wall of the box at both ends. One end of the suspension rope is connected to the horizontal rod, and an alkali-activated concrete test bar is fixedly suspended at the other end of the horizontal rod. The alkali-activated concrete test bar is inserted into the sealed salt solution box and half-submerged in the corrosive salt solution. The testing mechanism further comprises an image recording device, which is located outside the box and is used to record the apparent morphology change of the alkali-activated concrete test bar during the salt crystallization process.

[0015] Optionally, the box is provided with a support at the bottom, and a net-shaped base plate is arranged above the support, and the sealed salt solution box is arranged on the net-shaped base plate.

[0016] Optionally, paraffin is arranged between the interface of the alkali-activated concrete test bar and the sealed salt solution box.

[0017] Optionally, the water outlet is connected with a water outlet valve, and the water inlet is connected with the saturated salt solution reservoir through a first hose, and the first hose is provided with a water inlet valve.

[0018] Optionally, the sealed box water inlet is connected with the corrosive salt solution reservoir through a second hose, and the second hose is provided with a sealed box water inlet valve.

[0019] Optionally, a stirring device is arranged below the box, and the stirring device is used to stir the saturated salt solution to keep the concentration of the saturated salt solution uniform.

[0020] According to another aspect of the present application, a method for testing the salt crystallization corrosion of alkali-activated concrete is provided, which is realized by using the above device. The method comprises the following steps:

[0021] Inject saturated salt solution into the box, and let it stand until the relative humidity value in the box is stable and reaches the required value, and obtain the initial liquid level height of the saturated salt solution through the first liquid level meter;

[0022] Provide the alkali-activated concrete test bar in the humidity equilibrium state, and measure the mass thereof;

[0023] Inject the corrosion salt solution with the required concentration value into the salt solution sealed box, install the alkali-activated concrete test bar, and make the alkali-activated concrete test bar half-submerged in the corrosion salt solution, and let it stand, and obtain the initial liquid level height of the corrosion salt solution through the second liquid level meter;

[0024] Monitor the temperature and humidity in the box through the temperature and humidity meter to ensure that the test requirements are met;

[0025] Monitor the liquid level height of the saturated salt solution through the first liquid level meter, and monitor the concentration change of the saturated salt solution through the salinity meter, and supplement the saturated salt solution when the liquid level height or the concentration changes until the concentration and the relative humidity return to the initial state;

[0026] Monitor the liquid level height of the corrosion salt solution through the second liquid level meter, and supplement the corrosion salt solution when the liquid level drops until the liquid level returns to the initial state;

[0027] Record the apparent morphology change of the alkali-activated concrete test bar in the salt crystallization process through the image recording device;

[0028] After the alkali-activated concrete test bar is soaked for a specified time, the alkali-activated concrete test bar is taken out for analysis, and the salt crystallization corrosion test result of the alkali-activated concrete test bar is obtained.

[0029] Optionally, the length of the alkali-activated concrete test bar immersed in the corrosion salt solution accounts for 10% to 20% of the entire length of the test bar.

[0030] Optionally, the number of the salt solution sealed boxes is determined according to the test requirements, and deionized water is injected into one of the salt solution sealed boxes as a control group during the test.

[0031] Optionally, the method further comprises: reserving one of the salt solution sealed boxes, and coating all the side surfaces of the alkali-activated concrete test bar therein with paraffin for waterproof sealing treatment, and not supplementing the liquid level height during the test, and continuously observing and recording the liquid level drop height as the test is carried out, and calculating the capillary water absorption rate according to the following formula:

[0032]

[0033] In the formula, h is the corrosion salt solution drop height, the unit is m; S is the capillary absorption rate, the unit is m / s 0.5 ; t is the adsorption time, the unit is s; and b is a fitting parameter.

[0034] Compared with the prior art, the application has at least one of the following beneficial effects:

[0035] 1. The alkali-activated concrete salt crystallization corrosion test device provided by the application suspends the alkali-activated concrete test bar through the horizontal rod and the suspension rope, realizes the semi-immersion contact mode of the alkali-activated concrete, and can effectively improve the salt solution corrosion rate; the relative humidity and the corrosion salt solution concentration in the test box can be stably controlled by monitoring and supplementing the saturated salt solution and the corrosion salt solution at any time during the test without disturbing the state of the measured alkali-activated concrete test bar. The device provided by the application has simple structure, reasonable function, simple operation and low cost, and can more truly restore the salt crystallization process of alkali-activated concrete in the natural environment compared with the dry-wet cycle accelerated test.

[0036] 2. The device and method provided by the application can obtain various performance parameters of alkali-activated concrete after salt crystallization corrosion, which helps to clarify the salt crystallization mechanism and performance degradation process in the concrete, thereby preventing the deterioration of the mechanical properties and durability of alkali-activated concrete caused by salt corrosion in actual engineering applications. BRIEF DESCRIPTION OF DRAWINGS

[0037] Other features, objects and advantages of the application will become more apparent after reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0038] Figure 1 FIG. 1 is a structural schematic view of an alkali-activated concrete salt crystallization corrosion test device in an embodiment of the application;

[0039] Corresponding reference signs in the drawings are as follows: 1 - box, 2 - salt solution sealing box, 3 - hygrometer, 4 - image recording device, 5 - salinometer, 6 - controller, 7 - saturated salt solution, 8 - water outlet, 9 - water outlet valve, 10 - first liquid level meter, 11 - water inlet, 12 - saturated salt solution storage, 13 - water inlet valve, 14 - first hose, 15 - support, 16 - mesh pad, 17 - corrosion salt solution, 18 - second liquid level meter, 19 - sealing box water inlet, 20 - corrosion salt solution storage, 21 - sealing box water inlet valve, 22 - second hose, 23 - alkali-activated concrete test bar, 24 - paraffin, 25 - data line, 26 - stirring device, 27 - base, 28 - horizontal rod, 29 - suspension rope. DETAILED DESCRIPTION

[0040] The application will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the application. These are all within the scope of protection of the application.

[0041] Referring to Figure 1 As shown in FIG. 1, the structure of the salt crystallization corrosion test device for alkali-activated concrete provided in an embodiment of the application. The salt crystallization corrosion test device for alkali-activated concrete includes a test mechanism and a support mechanism, the test mechanism includes a box 1, a temperature and humidity meter 3, a salinity meter 5 and at least one sealed salt solution box 2; the box 1 contains saturated salt solution 7 to stabilize the humidity in the box 1 within the required range, wherein saturated MgCl2 solution is recommended for low humidity requirements, and saturated KCl solution is recommended for high humidity requirements, and the box 1 is provided with a first liquid level meter 10 for measuring the liquid level of the saturated salt solution 7, and the box 1 is provided with a water inlet 11 and a water outlet 8, the water inlet 11 and the water outlet 8 are located on the opposite two side walls, such as Figure 1The left side wall of the box 1 is provided with a water outlet 8, and the right side wall of the box 1 is provided with a water inlet 11, which is communicated with a saturated salt solution storage 12 outside the box 1, so that the concentration of the saturated salt solution is supplemented through the saturated salt solution storage 12, so that the relative humidity in the box 1 is stable; the salt solution sealed box 2 is suspended and arranged in the box 1 and above the saturated salt solution 7, the salt solution sealed box 2 contains the corrosive salt solution 17 and is provided with a second liquid level meter 18 for measuring the liquid level of the corrosive salt solution 17, the corrosive salt solution 17 is independent of the saturated salt solution 7 in the box 1 and does not interfere with each other, and the salt solution sealed box 2 is provided with a sealed box water inlet 19 communicated with a corrosive salt solution storage 20 outside the box 1, so that the concentration of the corrosive salt solution is supplemented through the corrosive salt solution storage 20, so that it is stable at the experimental set value; the hygrothermograph 3 is arranged in the box 1 and is used for monitoring the temperature and humidity in the test process; the salinometer 5 is used for measuring the concentration and pH value of the saturated salt solution 7 flowing out of the water outlet 8; the support mechanism includes a horizontal rod 28 and a suspension rope 29, the horizontal rod 28 and the suspension rope 29 are used for suspending and fixing the measured part, that is, the alkali-activated concrete test strip 23, so as to realize the semi-immersion corrosion mode; specifically, the horizontal rod 28 is horizontally arranged in the box 1 and is fixedly connected with the inner wall of the box 1 at both ends, one end of the suspension rope 29 is connected with the horizontal rod 28, the alkali-activated concrete test strip 23 is suspended and fixed at the other end of the horizontal rod 28, and the alkali-activated concrete test strip 23 is inserted in the salt solution sealed box 2 and is semi-immersed in the corrosive salt solution 17; the test mechanism further includes an image recording device 4, the image recording device 4 is located outside the box 1 and is used for recording the apparent morphology change of the alkali-activated concrete test strip 23 in the salt crystallization process, since the salt crystallization will cause white powder-like substances on the surface of the sample, the influence degree of the salt crystallization on the surface of the concrete can be directly reflected by observing the apparent morphology change of the alkali-activated concrete test strip 23.

[0042] The device provided by the embodiment of the present application suspends the alkali-activated concrete test strip 23 through the horizontal rod 28 and the suspension rope 29, realizes the semi-immersion contact mode of the alkali-activated concrete, and can effectively improve the salt solution corrosion rate; through the monitoring of the hygrothermograph 3, the salinometer 5 and the liquid level meter, the change of the apparent state of the alkali-activated concrete test strip 23 in the salt corrosion process can be observed in real time, and the saturated salt solution 7 and the corrosive salt solution 17 can be supplemented at any time in the test process, so that the relative humidity in the box 1 and the concentration of the corrosive salt solution 17 can be stably controlled, and the state of the measured alkali-activated concrete test strip 23 will not be disturbed. The device provided by the embodiment of the present application has the advantages of simple structure, reasonable function, simple operation and low cost, compared with the dry-wet cycle accelerated test, the embodiment of the present application can more truly restore the salt crystallization process of the alkali-activated concrete in the natural environment.

[0043] In order to facilitate observation during the test, in some embodiments, the box 1 is a transparent box, for example, a plexiglass box. In order to facilitate the arrangement of multiple salt solution sealed boxes 2, the box 1 is in the form of a sealed cuboid. A base 27 is arranged below the box 1 to support the box 1, so as to ensure the stability of the device during the test.

[0044] In some embodiments, a support 15 is arranged at the bottom of the box 1, and a meshed base plate 16 is arranged above the support 15, and the salt solution sealed box 2 is arranged on the meshed base plate 16. The salt solution sealed box 2 is suspended above the saturated salt solution 7 in the box 1 by the support 15 and the meshed base plate 16.

[0045] In the embodiment of the present application, the alkali-activated concrete test bar 23 is suspended in the corrosive salt solution 17, which can be applied to test bars of various shapes and sizes. The alkali-activated concrete test bar 23 is pretreated before the salt crystallization test, for example, the test bar is placed in an environment with a humidity of 50±5% for 3 days to achieve a humidity equilibrium state. Since the pretreatment does not use an oven to dry the test bar, the structure of the test bar is not affected, so as not to interfere with the salt crystallization process, which is beneficial to improve the reliability of the test results.

[0046] In some embodiments, paraffin 24 is arranged between the interface between the alkali-activated concrete test bar 23 and the salt solution sealed box 2, so as to seal the gap between the test bar and the salt solution sealed box 2, so as to minimize the exchange and transmission of moisture between the box 1 and the salt solution sealed box 2, which is beneficial to improve the accuracy of the test results.

[0047] In some embodiments, the water outlet 8 is connected with the water outlet valve 9, and the salinometer 5 is arranged near the water outlet 8. During the test, the saturated salt solution 7 in the box 1 can be sampled at any time, and the concentration and pH value of the saturated salt solution 7 can be measured by the salinometer 5. The water inlet 11 is connected with the saturated salt solution storage 12 through the first hose 14, for example, the first hose 14 is a silica gel tube, and the water inlet valve 13 is arranged on the first hose 14, so as to facilitate the replenishment of the saturated salt solution 7 in the box 1.

[0048] In some embodiments, the sealed box water inlet 19 is connected with the corrosive salt solution storage 20 through the second hose 22, for example, the second hose 22 is a silica gel tube, and the sealed box water inlet valve 21 is arranged on the second hose 22, so as to facilitate the replenishment of the corrosive salt solution 17 in the salt solution sealed box 2.

[0049] Normally, the amount of the liquid level drop of the storage tank and the corresponding change value of the liquid level gauge in the salt solution box should be consistent, but in fact, the salt solution adsorbed in the test strip may also have a backflow phenomenon due to the imbalance of the concentration of the pore solution in the test strip, resulting in a small error between the amount of the supplemented salt solution and the actual amount of the adsorbed salt solution. In order to accurately obtain the volume of the saturated salt solution 7 and the volume of the corrosive salt solution 17 supplemented during the test, high-precision scales are marked on the saturated salt solution storage tank 12 and the corrosive salt solution storage tank 20, and the scales on the storage tanks can assist in observing the change of the liquid level, and the liquid level gauges are mutually complementary, so that the change of the liquid level is monitored by two different means, the test error is controlled as much as possible, and the accuracy and reliability of the measurement results are improved. In addition, the first liquid level gauge 10 and the second liquid level gauge 18 are both high-sensitivity electronic water level sensors, which are beneficial to improve the accuracy of the test results.

[0050] In some embodiments, a stirring device 26 is arranged below the box 1, and the stirring device 26 is used for stirring the saturated salt solution 7 to keep the concentration of the saturated salt solution 7 uniform. Exemplarily, the stirring device 26 adopts a magnetic stirrer.

[0051] In some embodiments, the image recording device 4 adopts a video cassette recorder (VCR), which can record the apparent morphology change of the alkali-activated concrete test strip 23 in the salt crystallization process during the experiment.

[0052] In the above embodiments, in order to meet the temperature requirements during the test, the temperature of the laboratory where the box 1 is located can be stabilized at room temperature by controlling the indoor air conditioning temperature, so as to meet the requirements of the salt crystallization erosion experiment.

[0053] In order to realize the automatic control of the test device, the above device further includes a controller 6, and the salinity meter 5, the temperature and humidity meter 3, and the image recording device 4 are respectively connected to the controller 6 through data lines 25. The controller 6 can store and process the relevant data observed in the salt crystallization process, and reduce the error caused by manual measurement.

[0054] Based on the same inventive concept, another embodiment of the present application provides an alkali-activated concrete salt crystallization erosion test method realized by using the above device, which continues to refer to Figure 1 The method comprises the following steps:

[0055] S1, before the test starts, the saturated salt solution 7 is injected into the box 1, and is left for a period of time until the relative humidity value in the box 1 is stable and reaches the required value, and the initial liquid level height of the saturated salt solution 7 is obtained through the first liquid level gauge 10;

[0056] S2, before the test, the alkali-activated concrete test piece 23 is pretreated to reach a humidity equilibrium state, and its mass is measured and recorded as m0(kg) for calculating the mass loss rate of the alkali-activated concrete test piece 23 under the action of salt crystallization; the test piece can be in a cylindrical, cuboid or other shape, and the height of the test piece is greater than 3 times the width or diameter of the cross section, for example, the size of the test piece can be 50mmx50mmx150mm;

[0057] S3, the corrosion salt solution 17 of the required concentration value is injected into the salt solution sealed box 2, and the alkali-activated concrete test piece 23 is installed so that the alkali-activated concrete test piece 23 is half-submerged in the corrosion salt solution 17, and is placed for a period of time, and the initial liquid level of the corrosion salt solution 17 is obtained through the second liquid level meter 18; preferably, the interface between the salt solution sealed box 2 and the alkali-activated concrete test piece 23 is treated with paraffin 24 to minimize the exchange and transmission of humidity between the box 1 and the salt solution sealed box 2;

[0058] The immersion depth of the bottom of the test piece is determined according to the height of the prepared test piece, for example, the length of the alkali-activated concrete test piece 23 submerged in the corrosion salt solution 17 from the bottom is about 10% to 20% of the entire length of the test piece, and specifically, for the test piece with a length of 150mm, the bottom immersion length can be 20mm. As a typical vertical half-submerged contact method, the immersion length in the embodiment of the present application can enhance the capillary adsorption effect while not affecting the evaporation rate of the test piece surface, thereby accelerating the salt crystallization corrosion experiment process.

[0059] S4, during the test, the temperature and humidity in the box 1 are monitored through the temperature and humidity meter 3 to ensure that the test requirements are met;

[0060] S5, during the test, the liquid level of the saturated salt solution 7 in the box 1 is monitored through the first liquid level meter 10 to control the humidity in the box 1 to remain stable, and the concentration change of the saturated salt solution 7 is monitored through the salinity meter 5, and when the liquid level or concentration changes, the saturated salt solution 7 is supplemented in time until the concentration and relative humidity return to the initial state;

[0061] Specifically, during the test, the saturated salt solution 7 is sampled from the water outlet 8 at intervals, the concentration change is monitored through the salinity meter 5, if the liquid level or concentration decreases, the water inlet valve 13 is opened, and the saturated salt solution 7 is supplemented until the concentration and relative humidity return to the initial state;

[0062] S6, during the test, the liquid level of the corrosion salt solution 17 in the salt solution sealed box 2 is monitored through the second liquid level meter 18, when the liquid level decreases, the sealed box water inlet valve 21 is opened, and the corrosion salt solution 17 is supplemented until the liquid level returns to the initial state;

[0063] S7, the apparent morphology change of the alkali-activated concrete test bar 23 in the salt crystallization process is recorded by the image recording device 4 during the test;

[0064] S8, after the alkali-activated concrete test bar 23 is soaked to the specified time, the alkali-activated concrete test bar 23 is taken out for analysis, and the salt crystallization corrosion test result of the alkali-activated concrete test bar 23 is obtained.

[0065] Specifically, the alkali-activated concrete test bar 23 is taken out, the salt crystallization condition of the test bar is observed, the mass of the test bar after salt crystallization is measured, and is recorded as m t (kg), and the initial mass measured in S2 can be combined to calculate the mass loss rate of the alkali-activated concrete test bar 23 under the action of salt crystallization. The calculation formula is:

[0066]

[0067] In the formula, Δm is the mass loss rate of the test bar under the action of salt crystallization, and t is the capillary adsorption time or the time during which the test bar is soaked in the salt solution.

[0068] Further, the sample is taken from the test bar for XRD analysis to determine the composition of the crystallization product after salt corrosion, the pore solution pH value and the ion concentration are measured, and the pore structure and mechanical properties of the alkali-activated concrete are measured.

[0069] In the embodiment of the application, the number of the salt solution sealed boxes 2 is determined according to the test requirements, and deionized water is injected into one of the salt solution sealed boxes 2 as a control group during the test.

[0070] In some embodiments, the method in the above embodiment further includes: reserving one of the salt solution sealed boxes 2, and coating all the side surfaces of the alkali-activated concrete test bar 23 in the salt solution sealed box 2 with paraffin for waterproof sealing treatment, and not supplementing the liquid level during the test. During the test, the height of the liquid level is continuously observed and recorded, and the capillary water absorption rate is calculated according to the following formula:

[0071]

[0072] In the formula, h is the height of the corrosion salt solution, that is, the adsorption height of the corrosion salt solution in the alkali-activated concrete test bar, and the unit is m; S is the capillary absorption rate, and the unit is m / s 0.5 ; t is the adsorption time, and the unit is s; and b is a fitting parameter.

[0073] The capillary water absorption rate of the measured alkali-activated concrete test bar can be calculated by fitting the adsorption height and time of the alkali-activated concrete at different times according to the above formula. According to the size of the capillary absorption rate S, it can be preliminarily judged that for the alkali-activated concrete test bar with the same porosity, the one with a larger S value tends to have efflorescence on the surface of the test bar, and the one with a smaller S value tends to have subflorescence near the dry front inside the test bar.

[0074] The device and method provided by the above embodiments of the present application can obtain various performance parameters of alkali-activated concrete after salt crystallization erosion, help to clarify the salt crystallization mechanism and performance degradation process in the concrete, and thus prevent the deterioration of the mechanical properties and durability of alkali-activated concrete caused by salt erosion in actual engineering applications.

[0075] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the specific embodiments described above, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The above preferred features can be used in combination as long as they do not conflict with each other.

Claims

1. A test device for alkali-activated salt crystallization erosion of concrete, characterized in that, include: The testing apparatus includes a housing, a thermometer and hygrometer, a salinity meter, and at least one sealed salt solution container; The tank contains a saturated salt solution and is equipped with a first level gauge for measuring the level of the saturated salt solution. The tank has an inlet and an outlet, with the inlet connected to the saturated salt solution storage container. A salt solution sealed box is suspended inside the tank and located above the saturated salt solution. The salt solution sealed box contains a corrosive salt solution and is equipped with a second level gauge for measuring the level of the corrosive salt solution. The salt solution sealed box has an inlet connected to the corrosive salt solution storage container. A thermometer and hygrometer are located inside the tank. A salinity meter is used to measure the concentration and pH value of the saturated salt solution flowing out from the outlet. The support mechanism includes a horizontal bar and a suspension rope. The horizontal bar is horizontally positioned inside the housing and its two ends are fixedly connected to the inner wall of the housing. One end of the suspension rope is connected to the horizontal bar, and the alkali-activated concrete test strip is suspended and fixed to the other end of the horizontal bar. The alkali-activated concrete test strip is inserted into the salt solution sealed box and partially immersed in the corrosive salt solution. The testing mechanism also includes an image recording device located outside the housing, used to record the changes in the appearance morphology of the alkali-activated concrete test strip during the salt crystallization process.

2. The alkali-activated concrete salt crystallization erosion test device according to claim 1, characterized in that, The box has a support at the bottom, and a mesh pad is provided above the support. The salt solution sealing box is located on the mesh pad.

3. The alkali-activated concrete salt crystallization erosion test device according to claim 1, characterized in that, Paraffin wax is provided between the interface between the alkali-activated concrete test strip and the salt solution sealing box.

4. The alkali-activated concrete salt crystallization erosion test device according to claim 1, characterized in that, The water outlet is connected to the water outlet valve, and the water inlet is connected to the saturated salt solution storage device through a first flexible hose, which is equipped with an inlet valve.

5. The alkali-activated concrete salt crystallization erosion test device according to claim 1, characterized in that, The water inlet of the sealed box is connected to the corrosive salt solution storage via a second hose, and the second hose is equipped with a water inlet valve for the sealed box.

6. The alkali-activated concrete salt crystallization erosion test device according to claim 1, characterized in that, A stirring device is provided at the bottom of the box. The stirring device is used to stir the saturated salt solution to maintain the uniform concentration of the saturated salt solution.

7. A method for testing the salt crystallization erosion of concrete using alkali-activated methods, implemented using the apparatus described in any one of claims 1-6, characterized in that, include: Saturated salt solution is injected into the chamber and left to stand until the relative humidity inside the chamber stabilizes and reaches the required test value. The initial liquid level of the saturated salt solution is then obtained through the first liquid level gauge. Provide alkali-activated concrete test strips in a humidity equilibrium state and measure their mass; Inject the corrosive salt solution of the required concentration into the salt solution sealed box, install the alkali-activated concrete test strip, and partially immerse the alkali-activated concrete test strip in the corrosive salt solution. Let it stand, and obtain the initial liquid level of the corrosive salt solution through the second liquid level gauge. The temperature and humidity inside the chamber are monitored using a thermometer and hygrometer to ensure that they meet the test requirements; The liquid level of the saturated salt solution is monitored by the first liquid level gauge, and the concentration change of the saturated salt solution is monitored by the salinity meter. When the liquid level or concentration changes, the saturated salt solution is replenished until the concentration and relative humidity return to the initial state. The level of the corrosive salt solution is monitored by a second level gauge. When the level drops, the corrosive salt solution is added until the level returns to its initial state. The appearance morphology changes of alkali-activated concrete specimens during the salt crystallization process were recorded using an image recording device. After the alkali-activated concrete specimens were soaked for a specified time, they were taken out and analyzed to obtain the salt crystallization erosion test results of the alkali-activated concrete specimens.

8. The method for testing alkali-activated salt crystallization erosion of concrete according to claim 7, characterized in that, The length of the alkali-activated concrete test strip immersed in the corrosive salt solution is 10% to 20% of the total length of the test strip.

9. The method for testing alkali-activated salt crystallization erosion of concrete according to claim 7, characterized in that, The number of salt solution sealed boxes is determined according to the experimental requirements. One of the salt solution sealed boxes is filled with deionized water and serves as a control group during the experiment.

10. The method for testing alkali-activated salt crystallization erosion of concrete according to claim 7, characterized in that, This also includes: retaining one of the salt solution sealed boxes, coating all sides of the alkali-activated concrete test strip inside with paraffin wax for waterproofing and sealing, not replenishing the liquid level during the test, continuously observing and recording the drop in liquid level as the test progresses, and calculating the capillary water absorption rate according to the following formula: In the formula, h is the drop height of the corrosive salt solution, in meters (m); S is the capillary absorption rate, in m / s. 0.5 t is the adsorption time in seconds; b is the fitting parameter.

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