A method for testing the frost resistance of concrete taking into account the dissolution
Patent Information
- Application Number
- CN202610807914.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-05
- Publication Date
- 2026-08-07
AI Technical Summary
[0004]本发明的目的在于提供一种考虑溶蚀的混凝土抗冻性试验方法，以解决上述背景技术中提出现有通常采用静态纯水作为冻融介质在数百次循环过程中保持不变，这与实际混凝土所处环境严重不符，导致从混凝土中溶出的离子在溶液中不断富集，很快达到化学平衡，从而强烈抑制后续溶蚀反应的进行，严重低估甚至完全掩盖了溶蚀损伤的长期贡献，其测试结果无法反映真实服役环境下冻融与溶蚀耦合的破坏效应，也难以用于科学评价不同配合比混凝土对溶蚀的敏感性的问题
1、本发明首次在标准化的冻融试验方法引入并量化了化学溶蚀变量，通过更换溶液介质，打破了传统静态介质对溶蚀反应的抑制，使持续的化学溶出过程得以在试验中真实再现，填补了标准方法在化学损伤考量上的空白，同时通过周期性更新介质，模拟了溶蚀产物被带走的关键环境条件，使实验室加速试验的损伤机制与真实服役机制的符合度大幅提高；
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Abstract
Description
Technical Field
[0001] This invention relates to the field of civil engineering material testing technology, specifically to a test method for the frost resistance of concrete that takes into account erosion. Background Technology
[0002] The damage to concrete under freeze-thaw cycles is a complex physicochemical process. The traditional freeze-thaw resistance test methods are mainly based on physical damage mechanisms, namely the volume expansion pressure generated by the freezing of pore water and the osmotic pressure generated by the migration of unfrozen water. These standard methods evaluate the freeze-thaw resistance level by monitoring the relative dynamic elastic modulus decay and mass loss of the specimen after freeze-thaw cycles. The default premise is that the damage is mainly caused by physical forces. Numerous studies and engineering practices have shown that freeze-thaw damage to concrete is significantly exacerbated, especially in de-icing salt environments or environments in contact with flowing water. This suggests the important role of chemical factors, as concrete pore fluid contains abundant Ca. 2+ OH - Plasma, the phase transition, temperature gradient and moisture migration during freeze-thaw processes drive the diffusion and migration of ions in the pores, resulting in the continuous dissolution of hydration products such as calcium hydroxide and CSH gel. This chemical process not only directly weakens the microstructure of the slurry and reduces its adhesion and stiffness, but more importantly, the micro-defects generated by dissolution will promote the micro-cracks generated by ice expansion, forming a "physical-chemical" synergistic damage effect.
[0003] Existing methods typically use static pure water as the freeze-thaw medium, which remains constant throughout hundreds of cycles. This is significantly inconsistent with the actual environment of concrete, causing ions dissolved from the concrete to accumulate in the solution and quickly reach chemical equilibrium. This strongly inhibits subsequent dissolution reactions, severely underestimating or even completely masking the long-term contribution of dissolution damage. The test results cannot reflect the destructive effect of the coupling of freeze-thaw and dissolution under real service conditions, and are also difficult to use for scientifically evaluating the sensitivity of concrete with different mix proportions to dissolution. Therefore, this method does not meet the current requirements. To address this, we propose a concrete freeze-thaw resistance test method that considers dissolution. Summary of the Invention
[0004] The purpose of this invention is to provide a concrete freeze-thaw resistance test method that takes into account corrosion, in order to solve the problem mentioned in the background art that the existing method usually uses static pure water as the freeze-thaw medium and keeps it unchanged during hundreds of cycles. This is seriously inconsistent with the actual environment of concrete, which leads to the continuous enrichment of ions dissolved from the concrete in the solution, which quickly reaches chemical equilibrium and thus strongly inhibits the subsequent corrosion reaction. This seriously underestimates or even completely masks the long-term contribution of corrosion damage. The test results cannot reflect the destructive effect of the coupling of freeze-thaw and corrosion under real service conditions, and are also difficult to use for scientific evaluation of the sensitivity of concrete with different mix proportions to corrosion.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a test method for the frost resistance of concrete considering dissolution, comprising the following steps: S1: Specimen preparation and pretreatment: The specimens that have been molded and cured to the specified age are subjected to vacuum water saturation treatment, and their initial mass and initial transverse fundamental frequency are measured as performance benchmarks. S2: Establish the freeze-thaw cycle interval, place the saturated specimen into the specimen box of the freeze-thaw test chamber, and add the initial freeze-thaw medium solution to form the initial chemical environment of the specimen. Perform multiple freeze-thaw cycles on the specimen through the freeze-thaw test chamber. After multiple pre-set freeze-thaw cycle intervals are completed, the test is paused. S3: Repeated treatment of specimens in chemical environment: After each freeze-thaw cycle interval is completed, the freeze-thaw medium solution contained in the specimen box is completely drained and collected as the old solution sample of that cycle interval. Then, immediately add a fresh solution with the same volume as the initial freeze-thaw medium solution and the same chemical composition to the specimen box to restore the initial chemical environment of the specimen. Repeat the freeze-thaw cycle interval of the specimen multiple times until the preset total number of cycles and the specimen destruction standard are reached. S4: Simultaneous quantitative monitoring of the dissolution process, chemical analysis of old solution samples collected in each freeze-thaw cycle interval to determine core indicators; S5: Multi-dimensional performance evaluation and correlation analysis. At each synchronous node when the freeze-thaw medium solution is changed, the mass and transverse fundamental frequency of the specimen are measured, and the mass loss rate and relative dynamic elastic modulus of the specimen are calculated. Time series curves are established, and then the correlation and temporal sequence of the time series curves are analyzed.
[0006] Preferably, the specimen is made of concrete, which is formed by mixing and pouring water, cement, coarse aggregate, sand, water-reducing agent and air-entraining agent. The specimen has a size of 150mm×150mm×150mm and an age of at least 28 days.
[0007] Preferably, the specimen is subjected to vacuum saturation treatment using a vacuum saturation machine, the vacuum saturation treatment comprising the following steps: A1: Material placement process: The specimens are vertically stacked in the stainless steel sleeve in the vacuum chamber of the vacuum saturation machine. First, a vacuum is drawn for 3 hours in an anhydrous state to fully extract the gas in the capillaries inside the specimens and create a negative pressure environment. A2: Water injection and suction. When the vacuum degree inside the specimen reaches a negative pressure of 1330Pa, distilled water is injected to submerge the specimen. Then, the vacuum is evacuated again for 1 hour, so that the distilled water can penetrate deep into the pores under the action of negative pressure. A3: Settle and test. Turn off the vacuum saturation machine and open the vent valve to restore normal pressure. Let the specimen continue to soak in water for 18-24 hours to complete the final saturation process with the help of atmospheric pressure. After the settling period, take out the specimen and immediately test the electrical flux and permeability of the specimen.
[0008] Preferably, the freeze-thaw medium solution is one of deionized water and a pore solution, the chemical composition of the deionized water and the pore solution is known and constant, and the initial freeze-thaw medium level is higher than the specimen height.
[0009] Preferably, the multiple freeze-thaw cycles of the freeze-thaw test chamber consist of alternating freezing and thawing phases. The freezing phase is from -15°C to -18°C and held for 2.5 hours, and the thawing phase is from 1°C to 5°C and held for 1.5 hours. Each freeze-thaw cycle interval includes 25 freeze-thaw cycles.
[0010] Preferably, the core indicators measured in the old solution sample include calcium ion concentration and pH value. The calcium ion concentration and pH value are used to directly characterize the dissolution of cement hydration products and the change in liquid phase alkalinity. The ion concentration, solution volume, and number of cycles of the old solution sample are used to calculate the average ion dissolution rate and the cumulative total dissolution for each freeze-thaw cycle interval.
[0011] Preferably, the mass loss rate of the specimen is W, which is used to measure the change in mass of concrete during the freeze-thaw process due to factors such as water expansion upon freezing and damage to the pore structure. The relative dynamic elastic modulus of the specimen is Ea, which is used to reflect the degree of damage to the internal structure of the concrete during the freeze-thaw cycle and is required to be no less than 60% of the initial value. ; ; in, This represents the mass loss rate of the specimen after the nth freeze-thaw cycle interval. The initial mass of the specimen before freeze-thaw. The mass of the specimen after the nth freeze-thaw cycle interval. Let be the relative dynamic elastic modulus of the specimen after the nth freeze-thaw cycle interval. The fundamental transverse frequency of the specimen after the nth freeze-thaw cycle interval. The initial value of the transverse fundamental frequency of the specimen before freeze-thaw.
[0012] Preferably, the time series curve includes a macroscopic performance degradation curve, a cumulative erosion growth curve, and a mass change curve, wherein the macroscopic performance degradation curve is a dynamic elastic modulus degradation curve.
[0013] Preferably, the time series curve is used to assess the correlation between corrosion development and macroscopic performance degradation through correlation and temporal analysis, and to distinguish the contribution patterns of physical damage and chemical damage.
[0014] Preferably, the core quantitative indicator of the cumulative erosion growth curve is the calcium ion dissolution rate. The calcium ion dissolution rate Used to reflect the degree of chemical solubility of Ca(OH)2 and CSH gel in concrete; ; in, The calcium ion dissolution rate of the specimen after the nth freeze-thaw cycle interval. The total mass of soluble calcium ions in the specimen before the freeze-thaw test. This represents the mass of residual calcium ions in the old solution sample after the nth freeze-thaw cycle interval. It is obtained by multiplying the calcium ion concentration and volume in the old solution sample.
[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces and quantifies chemical dissolution variables for the first time in the standardized freeze-thaw test method. By changing the solution medium, it breaks the inhibition of the dissolution reaction by the traditional static medium, so that the continuous chemical dissolution process can be realistically reproduced in the test, filling the gap in the standard method in the consideration of chemical damage. At the same time, by periodically updating the medium, it simulates the key environmental conditions for the dissolution products to be carried away, which greatly improves the consistency between the damage mechanism of the accelerated test in the laboratory and the real service mechanism. 2. This invention correlates the degradation of macroscopic physical properties with the migration of microscopic chemical substances, enabling researchers to diagnose whether the main control mechanism of damage is physical expansion or chemical dissolution. This provides precise guidance for material optimization and is applicable to the objective evaluation and screening of high-durability concrete used in complex scenarios such as de-icing salt environments, hydraulic structures, and coastal areas, including concrete with added mineral admixtures and anti-corrosion additives. It can effectively identify materials that perform well in traditional tests but have insufficient resistance to dissolution, thus improving the reliability of engineering life prediction. Attached Figure Description
[0016] Figure 1 This is a flowchart of the concrete frost resistance test method of the present invention; Figure 2 This is a line graph showing the changes in calcium ions in the freeze-thaw medium solution under the freeze-thaw conditions of this invention. Figure 3 This is a line graph showing the pH change in the freeze-thaw medium solution under the freeze-thaw conditions of this invention. Figure 4This is a line graph showing the compressive strength of the specimens subjected to freeze-thaw cycles according to the present invention. Figure 5 This is a line graph showing the compressive strength loss rate of the specimens during the freeze-thaw cycle of this invention. Detailed Implementation
[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0018] Please see Figure 1 The present invention provides an embodiment of a method for testing the frost resistance of concrete considering dissolution, comprising the following steps: S1: Specimen preparation and pretreatment: The specimens that have been molded and cured to the specified age are subjected to vacuum water saturation treatment, and their initial mass and initial transverse fundamental frequency are measured as performance benchmarks. S2: Establish the freeze-thaw cycle interval, place the saturated specimen into the specimen box of the freeze-thaw test chamber, and add the initial freeze-thaw medium solution to form the initial chemical environment of the specimen. Perform multiple freeze-thaw cycles on the specimen through the freeze-thaw test chamber. After multiple pre-set freeze-thaw cycle intervals are completed, the test is paused. S3: Repeated treatment of specimens in chemical environment: After each freeze-thaw cycle interval is completed, the freeze-thaw medium solution contained in the specimen box is completely drained and collected as the old solution sample of that cycle interval. Then, immediately add a fresh solution with the same volume as the initial freeze-thaw medium solution and the same chemical composition to the specimen box to restore the initial chemical environment of the specimen. Repeat the freeze-thaw cycle interval of the specimen multiple times until the preset total number of cycles and the specimen destruction standard are reached. S4: Simultaneous quantitative monitoring of the dissolution process, chemical analysis of old solution samples collected in each freeze-thaw cycle interval to determine core indicators; S5: Multi-dimensional performance evaluation and correlation analysis. At each synchronous node when the freeze-thaw medium solution is changed, the mass and transverse fundamental frequency of the specimen are measured, and the mass loss rate and relative dynamic elastic modulus of the specimen are calculated. Time series curves are established, and then the correlation and temporal sequence of the time series curves are analyzed.
[0019] Please refer to Table 1. The material of the specimen is concrete, which is made by mixing water, cement, coarse aggregate, sand, water-reducing agent and air-entraining agent and then pouring it into shape. The size of the specimen is 150mm×150mm×150mm, and the curing period of the specimen is at least 28 days.
[0020] Table 1: Mix proportions of concrete specimens
[0021] The specimens are subjected to vacuum saturation treatment using a vacuum saturation machine. The vacuum saturation treatment includes the following steps: A1: Material placement process: The specimens are vertically stacked in the stainless steel sleeve in the vacuum chamber of the vacuum saturation machine. First, a vacuum is drawn for 3 hours in an anhydrous state to fully extract the gas in the capillaries inside the specimens and create a negative pressure environment. A2: Water injection and suction. When the vacuum degree inside the specimen reaches a negative pressure of 1330Pa, distilled water is injected to submerge the specimen. Then, the vacuum is evacuated again for 1 hour, so that the distilled water can penetrate deep into the pores under the action of negative pressure. A3: Settle and test. Turn off the vacuum saturation machine and open the vent valve to restore normal pressure. Let the specimen continue to soak in water for 18-24 hours to complete the final saturation process with the help of atmospheric pressure. After the settling period, take out the specimen and immediately test the electrical flux and permeability of the specimen.
[0022] Furthermore, the freeze-thaw medium solution is either deionized water or a pore solution. The chemical composition of the deionized water and the pore solution is known and constant. The initial liquid level of the freeze-thaw medium is higher than the height of the specimen. The multiple freeze-thaw cycles in the freeze-thaw test chamber consist of alternating freezing and thawing phases. The freezing phase is from -15℃ to -18℃ and held for 2.5 hours, and the thawing phase is from 1℃ to 5℃ and held for 1.5 hours. Each freeze-thaw cycle interval includes 25 freeze-thaw cycles.
[0023] The mass loss rate of the specimen is W, which measures the change in mass of concrete during freeze-thaw cycles due to factors such as water expansion upon freezing and damage to the pore structure. The relative dynamic elastic modulus of the specimen is Ea, which reflects the degree of damage to the internal structure of concrete during freeze-thaw cycles and is required to be no less than 60% of the initial value. ; ; in, This represents the mass loss rate of the specimen after the nth freeze-thaw cycle interval. The initial mass of the specimen before freeze-thaw. The mass of the specimen after the nth freeze-thaw cycle interval. Let be the relative dynamic elastic modulus of the specimen after the nth freeze-thaw cycle interval. The fundamental transverse frequency of the specimen after the nth freeze-thaw cycle interval. The initial value of the transverse fundamental frequency of the specimen before freeze-thaw.
[0024] The time series curves include macroscopic performance degradation curves, cumulative erosion growth curves, and mass change curves. The macroscopic performance degradation curve is the dynamic elastic modulus degradation curve. The time series curves are used to evaluate the correlation between erosion development and macroscopic performance degradation through correlation and time sequence analysis, and to distinguish the contribution patterns of physical damage and chemical damage. The core quantitative indicator of the cumulative corrosion growth curve is the calcium ion dissolution rate. calcium ion dissolution rate Used to reflect the degree of chemical solubility of Ca(OH)2 and CSH gel in concrete; ; in, The calcium ion dissolution rate of the specimen after the nth freeze-thaw cycle interval. The total mass of soluble calcium ions in the specimen before the freeze-thaw test. This represents the mass of residual calcium ions in the old solution sample after the nth freeze-thaw cycle interval. It is obtained by multiplying the calcium ion concentration and volume in the old solution sample.
[0025] Based on the concrete specimens in Table 1, the freeze-thaw resistance of the concrete specimens was tested after six freeze-thaw cycle intervals. The six freeze-thaw cycle intervals were the 25th, 50th, 75th, 100th, 125th and 150th cycles. Please see Figure 2 and Figure 3 The core indicators for measuring old solution samples include calcium ion concentration and pH value. The ion concentration, solution volume and number of cycles of old solution samples are used to calculate the average ion dissolution rate and cumulative dissolution amount for each freeze-thaw cycle interval. By measuring the calcium ion concentration and pH value of old solution samples in the freeze-thaw cycle interval, the dissolution of cement hydration products and the change of liquid phase alkalinity can be directly characterized. Please see Figure 4 and Figure 5 Under freeze-thaw cycles, concrete specimens exhibited significant Ca2+ oxidation. 2+ OH - The dissolution phenomenon causes the hydration products inside the concrete to decompose and dissolve directly, leading to a decrease in the mechanical properties of the concrete.
[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
Claims
1. A test method for the freeze-thaw resistance of concrete considering dissolution, characterized in that, Includes the following steps: S1: Specimen preparation and pretreatment: The specimens that have been molded and cured to the specified age are subjected to vacuum water saturation treatment, and their initial mass and initial transverse fundamental frequency are measured as performance benchmarks. S2: Establish the freeze-thaw cycle interval, place the saturated specimen into the specimen box of the freeze-thaw test chamber, and add the initial freeze-thaw medium solution to form the initial chemical environment of the specimen. Perform multiple freeze-thaw cycles on the specimen through the freeze-thaw test chamber. After multiple pre-set freeze-thaw cycle intervals are completed, the test is paused. S3: Repeated treatment of specimens in chemical environment: After each freeze-thaw cycle interval is completed, the freeze-thaw medium solution contained in the specimen box is completely drained and collected as the old solution sample of that cycle interval. Then, immediately add a fresh solution with the same volume as the initial freeze-thaw medium solution and the same chemical composition to the specimen box to restore the initial chemical environment of the specimen. Repeat the freeze-thaw cycle interval of the specimen multiple times until the preset total number of cycles and the specimen destruction standard are reached. S4: Simultaneous quantitative monitoring of the dissolution process, chemical analysis of old solution samples collected in each freeze-thaw cycle interval to determine core indicators; S5: Multi-dimensional performance evaluation and correlation analysis. At each synchronous node when the freeze-thaw medium solution is changed, the mass and transverse fundamental frequency of the specimen are measured, and the mass loss rate and relative dynamic elastic modulus of the specimen are calculated. Time series curves are established, and then the correlation and temporal sequence of the time series curves are analyzed.
2. The method for testing the frost resistance of concrete considering dissolution according to claim 1, characterized in that: The mass loss rate of the specimen is W, which is used to measure the change in the mass of concrete during the freeze-thaw process due to factors such as the expansion of water when it freezes and the destruction of the pore structure. The relative dynamic elastic modulus of the specimen is Ea, which is used to reflect the degree of damage to the internal structure of the concrete during the freeze-thaw cycle, and is required to be no less than 60% of the initial value. ； ； in, This represents the mass loss rate of the specimen after the nth freeze-thaw cycle interval. The initial mass of the specimen before freeze-thaw. The mass of the specimen after the nth freeze-thaw cycle interval. Let be the relative dynamic elastic modulus of the specimen after the nth freeze-thaw cycle interval. The fundamental transverse frequency of the specimen after the nth freeze-thaw cycle interval. The initial value of the transverse fundamental frequency of the specimen before freeze-thaw.
3. The method for testing the frost resistance of concrete considering dissolution according to claim 2, characterized in that: The time series curves include a macroscopic performance degradation curve, a cumulative dissolution growth curve, and a mass change curve, wherein the macroscopic performance degradation curve is a dynamic elastic modulus degradation curve.
4. The method for testing the frost resistance of concrete considering dissolution according to claim 3, characterized in that: The core quantitative indicator of the cumulative erosion growth curve is the calcium ion dissolution rate. The calcium ion dissolution rate Used to reflect the degree of chemical solubility of Ca(OH)2 and CSH gel in concrete; ； in, The calcium ion dissolution rate of the specimen after the nth freeze-thaw cycle interval. The total mass of soluble calcium ions in the specimen before the freeze-thaw test. This represents the mass of residual calcium ions in the old solution sample after the nth freeze-thaw cycle interval. It is obtained by multiplying the calcium ion concentration and volume in the old solution sample.
5. The method for testing the frost resistance of concrete considering dissolution according to claim 4, characterized in that: The specimen is made of concrete, which is formed by mixing and pouring water, cement, coarse aggregate, sand, water-reducing agent and air-entraining agent. The specimen has a size of 150mm×150mm×150mm and an age of at least 28 days.
6. The method for testing the freeze-thaw resistance of concrete considering erosion according to claim 5, characterized in that: The specimen is subjected to vacuum saturation treatment using a vacuum saturation machine, and the vacuum saturation treatment includes the following steps: A1: Material placement process: The specimens are vertically stacked in the stainless steel sleeve in the vacuum chamber of the vacuum saturation machine. First, a vacuum is drawn for 3 hours in an anhydrous state to fully extract the gas in the capillaries inside the specimens and create a negative pressure environment. A2: Water injection and suction. When the vacuum degree inside the specimen reaches a negative pressure of 1330Pa, distilled water is injected to submerge the specimen. Then, the vacuum is evacuated again for 1 hour, so that the distilled water can penetrate deep into the pores under the action of negative pressure. A3: Settle and test. Turn off the vacuum saturation machine and open the vent valve to restore normal pressure. Let the specimen continue to soak in water for 18-24 hours to complete the final saturation process with the help of atmospheric pressure. After the settling period, take out the specimen and immediately test the electrical flux and permeability of the specimen.
7. The method for testing the frost resistance of concrete considering dissolution according to claim 6, characterized in that: The freeze-thaw medium solution is one of deionized water and a pore solution, the chemical composition of which is known and constant, and the initial freeze-thaw medium level is higher than the specimen height.
8. The method for testing the frost resistance of concrete considering dissolution according to claim 7, characterized in that: The freeze-thaw test chamber consists of multiple freeze-thaw cycles, which alternate between a freezing phase and a thawing phase. The freezing phase is from -15°C to -18°C and held for 2.5 hours, while the thawing phase is from 1°C to 5°C and held for 1.5 hours. Each freeze-thaw cycle interval includes 25 freeze-thaw cycles.
9. A method for testing the frost resistance of concrete considering dissolution according to claim 8, characterized in that: The core indicators measured for the old solution sample include calcium ion concentration and pH value. The calcium ion concentration and pH value are used to directly characterize the dissolution of cement hydration products and the change in liquid phase alkalinity. The ion concentration, solution volume, and number of cycles of the old solution sample are used to calculate the average ion dissolution rate and the cumulative total dissolution for each freeze-thaw cycle interval.
10. A method for testing the frost resistance of concrete considering dissolution according to claim 3, characterized in that: The time series curves are used to assess the correlation between corrosion development and macroscopic performance degradation through correlation and temporal analysis, and to distinguish the contribution patterns of physical damage and chemical damage.