A rapid test method for the rust-inhibiting properties of freshly mixed concrete

Abstract

This disclosure relates to a rapid testing method for the rust-inhibiting performance of freshly mixed concrete. The rapid testing method includes the following steps: (1) mixing freshly mixed concrete with water and taking the clear upper layer solution; (2) adding soluble chloride salt and oxidant to the clear upper layer solution in sequence and mixing to obtain a test solution; (3) placing a standard carbon steel corrosion test piece in the test solution and testing whether the test piece shows rust and the degree of rust, thereby determining the rust-inhibiting performance of the freshly mixed concrete. The rapid testing method provided by this disclosure can complete the test in a short time and can quickly determine whether the rust-inhibiting performance of the concrete being constructed on site meets the standards.

Description

Technical Field

[0001] This disclosure relates to the technical field of concrete testing methods, and in particular to a rapid testing method for the rust-inhibiting properties of freshly mixed concrete. Background Technology

[0002] In the field of engineering construction, reinforced concrete is one of the most commonly used engineering materials. Under normal conditions, the steel bars inside the concrete are protected by the concrete and remain in a passivated state, preventing corrosion. However, in special environments, such as coastal areas or saline-alkali lands, chloride ions from the environment can enter the concrete, causing rapid corrosion of the steel bars and thus damaging the reinforced concrete structure. In addition, the de-icing salts commonly used today also contain a large amount of chloride ions, which can accelerate the corrosion of the steel bars inside the concrete in environments where de-icing salts are used.

[0003] To inhibit the corrosion of steel bars in concrete by chloride ions, the most common method is to add steel corrosion inhibitors to the concrete. GB / T50046-2018, "Standard for Corrosion Protection Design of Industrial Buildings," also explicitly requires the use of steel corrosion inhibitors in corrosive environments to extend the service life of reinforced concrete. Related material and construction standards include JGJ / T192-2009, "Technical Specification for Application of Steel Corrosion Inhibitors," and GB / T33803-2017, "Technical Specification for Corrosion Resistance Application of Corrosion Inhibitors in Reinforced Concrete," etc.

[0004] Currently, various steel reinforcement corrosion inhibitors are available for use in reinforced concrete to prevent corrosion of steel bars. However, a common problem hindering construction is how to quickly test the corrosion-inhibiting effect of concrete with the corrosion inhibitor added on-site. Current projects can only conduct raw material testing on the incoming steel reinforcement corrosion inhibitors according to relevant standards beforehand; there is no corresponding method to test the corrosion-inhibiting performance of the concrete during on-site construction.

[0005] According to the current relevant standards and specifications, the rust-inhibiting performance can only be tested on hardened concrete. The test method is complex and the cycle is long. It is very likely that the test results can only be obtained after the project is completed. If the rust-inhibiting performance does not meet the standards, a lot of manpower and resources will be wasted on rework.

[0006] Therefore, it is necessary to develop a rapid testing method for the rust-inhibiting performance of freshly mixed concrete, which can quickly determine whether the rust-inhibiting performance of concrete constructed on site meets the standards and minimize the waste of manpower and resources. Summary of the Invention

[0007] To address the aforementioned technical problems, this disclosure provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete. The rapid testing method provided by this disclosure can complete the test in a short time and quickly determine whether the rust-inhibiting performance of concrete being constructed on-site meets the standards.

[0008] In a first aspect, this disclosure provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete, the rapid testing method comprising the following steps:

[0009] (1) Mix freshly mixed concrete with water and take the clear solution from the top layer;

[0010] (2) Add soluble chloride and oxidant to the clear upper layer of solution and mix to obtain the test solution;

[0011] (3) Place the carbon steel standard corrosion test piece in the test liquid and check whether the test piece shows rust or the degree of rust on the test piece, so as to judge the rust-inhibiting performance of the fresh concrete.

[0012] The rapid testing method disclosed herein accelerates the corrosion of steel reinforcement materials through chloride ions and oxidants, thus speeding up the time it takes for the steel reinforcement to rust. If no steel reinforcement rust inhibitor is added to the fresh concrete or the amount of steel reinforcement rust inhibitor added is insufficient, the test specimen will show rust or severe rust in a short period of time during the testing process. In contrast, concrete that meets the standards will not show rust or will only show very slight rust during the testing process. This testing method with clear differentiation enables testers to determine whether the rust inhibition performance of the fresh concrete is qualified in a short testing time without any doubt.

[0013] As a preferred embodiment of this disclosure, the amount of soluble chloride added to the detection solution is 0.5-10.0% of the mass of the upper clear solution, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., preferably 2%.

[0014] As a preferred embodiment of this disclosure, the soluble chloride salt is selected from any one or a combination of at least two of sodium chloride, calcium chloride, or magnesium chloride.

[0015] As a preferred embodiment of this disclosure, the amount of oxidant added to the detection solution is 0.06-1.5‰ of the mass of the upper clear solution, such as 0.08‰, 0.1‰, 0.2‰, 0.5‰, 0.6‰, 0.8‰, 1.0‰, 1.2‰, 1.4‰, etc., preferably 0.3‰.

[0016] As a preferred embodiment of this disclosure, the oxidant is selected from reactive oxygen molecules, further selected from compounds containing peroxy groups, and even more preferably hydrogen peroxide.

[0017] As a preferred embodiment of this disclosure, the amount of water added is such that the pH of the upper clarified solution is 7-12.

[0018] The concentration of chloride ions and the concentration of oxidant both affect the corrosion rate of the test piece. By controlling the amount of chloride salt, oxidant and pH value of the clear solution in the upper layer, this disclosure can obtain test results in a shorter time and make the test method provided by this disclosure applicable to different fresh concrete tests.

[0019] Meanwhile, this disclosure reveals that peroxides, especially hydrogen peroxide, when used in combination with chloride ions, can significantly accelerate the corrosion of test pieces, thus achieving the purpose of rapid detection.

[0020] As a preferred technical solution of this disclosure, the test piece is derusted and degreased before testing.

[0021] As a preferred technical solution of this disclosure, in step (3), the test piece is checked for rust every 5-10 minutes.

[0022] As a preferred technical solution of this disclosure, the test piece is placed in the test solution for 2-24 hours, and then the corrosion of the test piece is tested.

[0023] As a preferred technical solution of this disclosure, the detection method in step (3) includes visual inspection and / or instrument detection.

[0024] As a preferred technical solution of this disclosure, the detection method includes detecting whether the test piece is corroded and / or detecting whether the color of the detection liquid has changed.

[0025] As a preferred technical solution of this disclosure, the detection method includes detecting the corrosion current of the test piece to determine the corrosion status of the test piece.

[0026] Considering that different application scenarios have different requirements for fresh concrete, for example, when applied to the seaside or saline-alkali land, where it is rich in chloride ions, a larger amount of steel reinforcement corrosion inhibitor needs to be added. In this case, the steel reinforcement needs to be placed in the test liquid for a longer period of time without being corroded. If applied to conventional scenarios, less steel reinforcement corrosion inhibitor is needed. Therefore, this disclosure does not limit what kind of result is considered as qualified for the corrosion inhibition performance of fresh concrete.

[0027] This disclosure mainly provides a rapid testing method for judging the rust-inhibiting performance of freshly mixed concrete. As for what constitutes a satisfactory rust-inhibiting performance and what constitutes a substandard rust-inhibiting performance, it is necessary to make a specific judgment based on the application scenario.

[0028] This disclosure allows for the preparation of in-situ mixed concrete using different amounts of rust inhibitors, followed by testing using the rapid testing method provided in this disclosure. The rust condition of the test specimens or the time of rust appearance is recorded. When conducting on-site testing, the recorded results are compared with the test results of the concrete at the construction site, enabling a relatively accurate and rapid determination of whether the amount of rust inhibitor added in the freshly mixed concrete at the construction site is up to standard. The testing method provided in this disclosure is adaptable to different types of rust inhibitors.

[0029] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0030] (1) The testing method provided in this disclosure can quickly test the rust-inhibiting performance of fresh concrete. The testing time is short and the method is relatively simple. The test can be completed in a short time at the construction site, minimizing the cost of non-compliance.

[0031] (2) By adjusting the amount of chloride salt, oxidant and pH value of the upper clear solution, this disclosure enables the detection method provided by this disclosure to be applicable to the detection of the rust-inhibiting performance of fresh concrete in different application scenarios. Moreover, the detection time is short, the judgment method is simple and the accuracy is extremely high. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0033] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0034] Figure 1 This is a morphological image of sample A1 used in the performance test of this disclosure.

[0035] Figure 2 This is a morphological image of sample A2 used in the performance test of this disclosure.

[0036] Figure 3 This is a morphological image of sample A3 used in the performance test of this disclosure.

[0037] Figure 4 The figure shows the test results of concrete with added rust inhibitor in performance test 2 of this disclosure;

[0038] Figure 5 This is a graph showing the test results of concrete without rust inhibitor in performance test 2 of this disclosure. Detailed Implementation

[0039] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0040] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0041] This disclosure provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete, specifically including the following steps:

[0042] (1) Mix fresh concrete with water, and add water in such a way that the pH of the clear solution in the upper layer is 7-12. Take the clear solution in the upper layer.

[0043] (2) Add soluble chloride and oxidant to the clear upper layer of solution in sequence to obtain the test solution;

[0044] The amount of soluble chloride added is 0.5-10.0% of the mass of the upper clear solution, and the amount of oxidant added is 0.06-1.5‰ of the mass of the upper clear solution. The soluble chloride is selected from any one or at least a combination of two of sodium chloride, calcium chloride, or magnesium chloride, and the oxidant is selected from hydrogen peroxide.

[0045] (3) Place the carbon steel standard corrosion test piece in the test solution and check whether the test piece shows corrosion every 5-10 minutes, and / or, after 2-24 hours, check the corrosion of the test piece to determine the corrosion resistance of the fresh concrete.

[0046] Example 1

[0047] This embodiment provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0048] (1) Mix fresh concrete with water at a mass ratio of 1:1, then filter and take the clear upper layer solution;

[0049] (2) Add 2g of sodium chloride and 1g of hydrogen peroxide (3% concentration) to 100g of the clear upper layer solution and mix to obtain the test solution;

[0050] (3) Place the standard corrosion test piece of carbon steel in the test liquid and check whether the test piece shows rust every 5 minutes to determine the rust-inhibiting performance of fresh concrete.

[0051] Performance Test 1: Evaluation of Rapid Detection Methods

[0052] (1) A certain project is located in a coastal area. In order to prevent the chloride ions in seawater from causing corrosion of the steel bars in the underground concrete, according to relevant specifications, a certain amount of nitrite-based steel bar corrosion inhibitor needs to be added to the concrete and the corrosion inhibition performance of the fresh concrete needs to be tested:

[0053] Fresh concrete was prepared according to the concrete mix proportions provided in Table 1, and then tested according to the rapid testing method provided in Example 1, wherein:

[0054] Table 1 (Unit: kg / m³) 3 )

[0055] cement fly ash Mineral powder sand stone Water reducing agent Steel reinforcement corrosion inhibitor water 360 60 30 690 1080 6.75 9 / 4.5 / 0 180

[0056] When conducting tests according to the mixing ratio provided in Example 1, the specific steps are as follows:

[0057] (1) Prepare three sets of concrete according to the mix proportions in Table 1, with the dosage of nitrite-based steel reinforcement corrosion inhibitor being 9 kg / m³. 3 4.5kg / m 3 0kg / m 3 After mixing evenly, weigh 1 kg of concrete sample, add 1 kg of water, stir thoroughly, let stand for 5 minutes, pour out the upper liquid and filter the solid particles with filter paper to obtain the upper clear solution.

[0058] (2) Take 100g of the clear upper layer solution, add 2g of sodium chloride and 1g of hydrogen peroxide (3% concentration) in sequence, stir to mix them thoroughly, and obtain the test solution;

[0059] (3) After degreasing a carbon steel standard corrosion test piece that meets the requirements of JGJ / T192-2009 "Technical Specification for Application of Corrosion Inhibitor of Steel Bars" with ethanol, place it in the test solution, requiring the carbon steel test piece to be completely immersed in the solution in the container;

[0060] (4) The corrosion of the carbon steel test piece in the test solution was observed every 15 minutes. The results are shown in Table 2:

[0061] Table 2

[0062] Sample number A1 A2 A3 <![CDATA[Dosage of steel bar rust inhibitor (kg / m 3 )]]> 9 4.5 0 Time of rust appearance - 120 minutes later 15 minutes later Corrosion status over 24 hours No visible rust Minor rust Extensive rust Test photos at 24 hours Figure 1 Figure 2 Figure 3

[0063] From Table 2 and Figure 1-3 According to the data, if no steel reinforcement corrosion inhibitor is added to the fresh concrete, the corrosion resistance performance of the fresh concrete can be determined within 15 minutes. Therefore, the testing method provided in this disclosure can quickly test the corrosion resistance performance of fresh concrete. During the construction process, fresh concrete can be taken from the site and tested according to the testing method provided in this disclosure, and it can be determined in a short time whether the corrosion resistance performance of the fresh concrete meets the requirements.

[0064] Example 2

[0065] This embodiment provides a three-component rapid testing kit for detecting the corrosion-inhibiting performance of freshly mixed concrete, wherein:

[0066] Component A consists of 3.5g of sodium chloride, Component B consists of 2g of 3% hydrogen peroxide, and Component C consists of filter paper and an open container with a capacity of more than 100mL.

[0067] When conducting rapid testing of the rust-inhibiting properties of freshly mixed concrete:

[0068] (1) Mix fresh concrete with water and filter it with filter paper to obtain the clear upper layer solution;

[0069] (2) Add component A and component B to the clear upper layer of solution in sequence and mix to obtain the test solution;

[0070] (3) Place the standard carbon steel corrosion test piece in the test liquid and check whether the test piece shows corrosion and the degree of corrosion. The corrosion resistance of the fresh concrete can be judged by the time of corrosion or the size of the corrosion area.

[0071] Performance Test 2: Evaluation of the Rapid Testing Kit

[0072] Prepare fresh concrete according to the proportions in Table 1 (without adding steel reinforcement corrosion inhibitor). Divide the concrete into two groups. One group is left untreated and is designated as the blank group concrete. The other group is prepared according to 8 kg / m³... 3 The amount of organic alcohol amine steel reinforcement corrosion inhibitor added is recorded as corrosion inhibitor-added concrete;

[0073] Take two samples of the rapid testing kit for the rust-inhibiting properties of fresh concrete and perform the test according to the following instructions:

[0074] (1) Take 200g of fresh concrete, add 600g of water, stir for 2min and let stand for 3min. Then filter the solid particles with the filter paper in component C and put the filtered clear solution into the open container in component C.

[0075] (2) Mix component A with 100 mL of the supernatant in an open container, and at the same time, add component B and mix.

[0076] (3) Add carbon steel standard corrosion test pieces and let stand. Observe the corrosion of the internal carbon steel standard corrosion test pieces. The corrosion inhibition performance of the fresh concrete is judged by the time of corrosion appearance or the size of the corrosion area. The test results are shown in Table 3 below:

[0077] Table 3

[0078] Sample name Concrete with rust inhibitor Blank group concrete Time of rust appearance Individual rust spots appeared after about 5 minutes. Multiple rust spots appeared within 1 minute Test photos at 30 minutes Figure 4 Figure 5

[0079] From Table 3 and Figure 4-5It is known that the rapid testing method provided in this disclosure has a good testing effect on the rust-inhibiting performance of fresh concrete. The degree of rust on the carbon steel standard corrosion test pieces of concrete with and without rust inhibitor is significantly different, which is sufficient to determine whether steel reinforcement rust inhibitor has been added to the concrete.

[0080] If tests are conducted in advance according to different dosages of the rust inhibitor in the concrete, and the corrosion condition of the carbon steel standard corrosion test pieces is recorded, and then compared with the test results of the concrete at the construction site, it can be determined more accurately whether the concrete at the construction site has added enough rust inhibitor according to the designed dosage. In addition, test parameters can be adjusted according to different steel reinforcement rust inhibitors, and different models of test kits can be provided.

[0081] Example 3

[0082] This embodiment provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0083] The difference from Example 1 is that in this example, the pH value of the clear solution in the upper layer is controlled to be 11 by controlling the amount of water added.

[0084] Example 4

[0085] This embodiment provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0086] (1) Mix fresh concrete with water at a mass ratio of 1:1, then filter and take the clear upper layer solution;

[0087] (2) Add 0.5g of sodium chloride and 5g of hydrogen peroxide (3% concentration) to 100g of the clear upper layer solution and mix to obtain the test solution;

[0088] (3) Place the standard corrosion test piece of carbon steel in the test liquid and check whether the test piece shows rust every 5 minutes to determine the rust-inhibiting performance of fresh concrete.

[0089] Example 5

[0090] This embodiment provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0091] (1) Mix fresh concrete with water at a mass ratio of 1:1, then filter and take the clear upper layer solution;

[0092] (2) Add 10g of sodium chloride and 0.2g of hydrogen peroxide (3% concentration) to 100g of the clear upper layer solution and mix to obtain the test solution;

[0093] (3) Place the standard corrosion test piece of carbon steel in the test liquid and check whether the test piece shows rust every 5 minutes to determine the rust-inhibiting performance of fresh concrete.

[0094] Comparative Examples 1-2

[0095] This comparative example provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0096] The difference from Example 1 is that, in this comparative example, the amount of sodium chloride added is 0.1g (Comparative Example 1) and 12g (Comparative Example 2).

[0097] Comparative Examples 3-4

[0098] This comparative example provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0099] The difference from Example 1 is that in this comparative example, the amount of hydrogen peroxide added is 0.1g (Comparative Example 3) and 6g (Comparative Example 4).

[0100] Comparative Example 5

[0101] This comparative example provides a rapid testing method for the rust-inhibiting performance of freshly mixed concrete.

[0102] The difference from Example 1 is that, in this comparative example, the oxidant is chlorine dioxide.

[0103] Performance Test 3

[0104] (1) Prepare blank concrete and concrete with rust inhibitor (rust inhibitor dosage is 9 kg / m³) according to performance test 1. 3 );

[0105] (2) The corrosion inhibition performance of fresh concrete was tested according to the rapid testing methods provided in Examples 1, 3-5 and Comparative Examples 1-5. The test results are shown in Table 4.

[0106] Table 4

[0107]

[0108] Table 4 shows that increasing chloride ion concentration, increasing hydrogen peroxide concentration, and decreasing pH value all accelerate the corrosion rate of steel samples. If the corrosion rate is too fast, both blank concrete and concrete mixed with chloride ions will show corrosion in a short time, making them difficult to distinguish. Decreasing chloride ion concentration, decreasing hydrogen peroxide concentration, and replacing hydrogen peroxide with chlorine dioxide as the oxidant will slow down the corrosion rate of steel samples. If the corrosion rate is too slow, even blank concrete will require a long time to show corrosion, affecting the efficiency of rapid on-site testing. The detection method provided in this disclosure ensures that the time for corrosion to appear is appropriate—neither too short, making observation difficult, nor too long, wasting excessive time.

[0109] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0110] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rapid testing method for the rust-inhibiting performance of freshly mixed concrete, characterized in that, The rapid detection method includes the following steps: (1) Mix fresh concrete with water and take the clear solution from the top layer. The amount of water added is such that the pH of the clear solution from the top layer is 7-12. (2) A soluble chloride salt and an oxidant are added to the upper clear solution and mixed to obtain a test solution. In the test solution, the amount of the soluble chloride salt added is 0.5-10.0% of the mass of the upper clear solution, and the amount of the oxidant added is 0.06-1.5‰ of the mass of the upper clear solution. (3) Place the standard corrosion test piece of carbon steel in the test solution and check whether the test piece is corroded every 5-10 minutes, or place the test piece in the test solution for 2-24 hours and check the degree of corrosion of the test piece to determine the corrosion resistance of the fresh concrete.

2. The rapid detection method according to claim 1, characterized in that, In the detection solution, the amount of the soluble chloride added is 2% of the mass of the upper clear solution.

3. The rapid detection method according to claim 1, characterized in that, The soluble chloride salt is selected from any one or a combination of at least two of sodium chloride, calcium chloride, or magnesium chloride.

4. The rapid detection method according to claim 1, characterized in that, In the detection solution, the amount of oxidant added is 0.3‰ of the mass of the upper clear solution.

5. The rapid detection method according to claim 1, characterized in that, The oxidant is selected from reactive oxygen molecules.

6. The rapid detection method according to claim 5, characterized in that, The oxidant is selected from compounds containing a peroxy group.

7. The rapid detection method according to claim 6, characterized in that, The oxidant is hydrogen peroxide.

8. The rapid detection method according to claim 1, characterized in that, The test pieces were derusted and degreased before testing.

9. The rapid detection method according to claim 1, characterized in that, The detection methods include visual inspection and / or instrumental inspection; And / or, the detection method includes detecting whether the test piece is corroded and / or detecting whether the color of the test solution has changed.

10. The rapid detection method according to claim 9, characterized in that, The detection method includes detecting the corrosion current of the test piece to determine the corrosion status of the test piece.

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