High-temperature environment-adaptable concrete hydration temperature rise inhibitor and preparation method thereof

Abstract

The application discloses a high-temperature environment adaptive concrete hydration temperature rise inhibitor and a preparation method thereof. The concrete hydration temperature rise inhibitor is a solid powder prepared from a solid mixture of sodium trimetaphosphate ascorbic acid ester compounds and retarding components and molten paraffin wax; the sodium trimetaphosphate ascorbic acid ester compounds are ester compounds generated from sodium trimetaphosphate and ascorbic acid under alkaline conditions; and the paraffin wax has a melting point of 44-50 DEG C. The high-temperature environment adaptive concrete hydration temperature rise inhibitor is prepared by mixing sodium trimetaphosphate ascorbic acid ester compounds, retarding components and paraffin wax. The hydration temperature rise inhibitor has the hydration regulation performance, has little influence on the induction period, is suitable for being applied to high-temperature mold-entering concrete, and can ensure the 28d compressive strength of the concrete.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology. Specifically, it relates to a high-temperature environment-adaptive concrete hydration temperature rise inhibitor, its preparation method, and its application in inhibiting temperature cracks in concrete. Background Technology

[0002] Cracks in large-volume concrete have always been a pressing issue in engineering, resulting in significant manpower and material costs for repairs every year. Therefore, reducing the occurrence of cracks in large-volume concrete has become a hot research topic in engineering. There are many causes of concrete cracks, mainly categorized as shrinkage cracks, temperature cracks, and settlement cracks; among these, shrinkage cracks and temperature cracks are the two primary forms of cracks.

[0003] Temperature cracks are caused by large temperature differences in concrete. During the hardening process, the cement in a concrete structure releases a large amount of heat of hydration, causing the internal temperature to rise continuously. This results in a significant temperature difference between the concrete surface and its interior, with the internal expansion exceeding the external expansion. At this point, the concrete surface experiences substantial tensile stress, which the early tensile strength of the concrete is too low to withstand, leading to cracking. Clearly, the key to temperature cracking lies in the large temperature difference between the inside and outside. Therefore, reducing this temperature difference is crucial to minimizing temperature cracking. A common method is to lay cooling water pipes. However, due to the excessive heat release during early cement hydration, especially in thick walls, the cooling efficiency of cooling water pipes is insufficient. If the peak rate of cement hydration heat release can be reduced to a certain extent, and this is combined with cooling water pipes, the temperature difference between the inside and outside of large-volume concrete can be effectively reduced. Materials that can reduce the peak rate of cement hydration heat release are called cement hydration rate regulating materials.

[0004] Currently, there are numerous reports on improved cement hydration rate control materials targeting temperature cracks. For example, patent document CN 104710131A describes a concrete hydration temperature rise inhibitor that effectively reduces the hydration rate during the acceleration and deceleration phases while having almost no effect on the cement hydration induction phase by encapsulating modified dextrin with a non-soluble polymer. This method is simple to prepare, but requires the removal of organic solvents, which is not environmentally friendly. Another example is patent document CN 105060762A, which discloses a method for preparing a starch-based cement hydration rate control material. The starch is completely gelatinized, then enzymatically hydrolyzed, and precipitated with ethanol, filtered, and pulverized to obtain dextrin. This dextrin is then reacted with an emulsifier to prepare a starch-based cement concrete hydration temperature rise inhibitor with hydration control properties. However, this process uses a large amount of ethanol, making post-processing more complicated. Japanese patents JP2017165627A and JP2020093940A respectively describe a crack-resistant concrete and an expansive agent with hydration control properties, both of which use dextrin as their hydration heat-inhibiting component.

[0005] The above-mentioned hydration control materials begin to play a role in the initial stage of mixing, and more or less have a certain impact on the induction period. Moreover, the hydration control performance will be weakened at high temperatures.

[0006] Therefore, given the current technical problems with starch or dextrin-based hydration temperature rise inhibitors, there is an urgent need to develop a hydration temperature rise inhibitor that has minimal impact on the induction period and good control performance at high temperatures, in order to solve the problem of temperature cracks in concrete. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention aims to provide a high-temperature-adaptive concrete hydration temperature rise inhibitor. This inhibitor releases a slowly releasing retarding component and sodium tripolyphosphate ascorbate compounds when paraffin wax reaches a certain temperature, thereby regulating hydration. Since the melting point of paraffin wax is controlled between 44℃ and 50℃, this hydration temperature rise inhibitor is suitable for use in environments where the pouring temperature exceeds 30℃.

[0008] The inventors of this invention discovered that the peak temperature of concrete generally exceeds 60°C, while the temperature upon placement in the formwork is typically around 20-30°C. When the concrete temperature exceeds 40°C, it indicates that the binder has already undergone a certain degree of hydration. At this point, introducing some retarding components or materials with hydration-regulating properties to reduce the hydration rate is a good method of hydration regulation. The advantage of this hydration regulation method is that it has almost no impact on the induction period.

[0009] Paraffin wax is a mixture that can be made into different melting points by adjusting the molecular weight of hydrocarbons. Paraffin wax can also be used as a temperature-sensitive material, changing from a solid to a liquid when the temperature reaches its melting point, thus releasing encapsulated substances.

[0010] Ascorbic acid and sodium trimetaphosphate undergo an esterification reaction under alkaline conditions. This reaction modifies the sodium trimetaphosphate, weakening its retarding effect and giving the esterified product some hydration regulation properties. Adding further retarding components, released through the melting of paraffin at a specific temperature, can further enhance hydration regulation.

[0011] Based on this, the present invention provides a high-temperature environment-adaptive concrete hydration temperature rise inhibitor, which is a solid powder prepared by a solid mixture of sodium tripolyphosphate ascorbate compound and retarding component and molten paraffin.

[0012] The sodium trimetaphosphate ascorbate esters are ester compounds formed by sodium trimetaphosphate and ascorbic acid under alkaline conditions;

[0013] The paraffin wax has a melting point of 44℃-50℃.

[0014] Furthermore, the retarding component is selected from any one or more of tartaric acid, citric acid, glucose, sorbitol, sodium tripolyphosphate, and sodium hexametaphosphate.

[0015] The hydration temperature rise inhibitor of this invention is designed based on the exothermic temperature rise characteristics of cement during the early and middle stages of hydration. Paraffin wax melts in an environment of 44℃-50℃, releasing ester compounds and retarding components with hydration-regulating properties, thereby controlling the hydration rate during the middle stage of hydration. This hydration temperature rise inhibitor is suitable for applications where the concrete pouring temperature is greater than 30℃.

[0016] The preparation method of the high-temperature environment-adaptive concrete hydration temperature rise inhibitor of the present invention includes the following steps:

[0017] (1) Add ascorbic acid, sodium trimephosphate and retarding component into water to obtain the first liquid phase. Adjust the pH to 9-11 and react at 40℃~60℃ for 2h~4h. Neutralize to pH=7 and dry at 60℃ to obtain the first solid phase of retarding component / ester.

[0018] (2) The paraffin wax with a melting point of 44℃-50℃ is melted at a temperature of 60℃-70℃ to obtain the second liquid phase;

[0019] (3) After fully wetting the first solid phase with the second liquid phase at a temperature of 60℃-70℃, stop heating and slowly cool down to room temperature to obtain the second solid phase. Crush the second solid phase to obtain the hydration temperature rise inhibitor of the present invention.

[0020] Furthermore, in the first liquid phase, the mass fraction of ascorbic acid is 10%–15%, the mass fraction of sodium trimetaphosphate is 10%–18%, and the mass fraction of the retarding component is 5%–10%.

[0021] Furthermore, the mass ratio of the second liquid phase to the first solid phase is 1:3 to 5.

[0022] The cooling rate in step (3) shall not exceed 2℃ / min.

[0023] The hydration temperature rise inhibitor provided by the present invention can be applied to concrete to suppress temperature cracks. The hydration temperature rise inhibitor is added to the concrete at a dosage of 0.4% to 0.6% of the total mass of cementitious materials in the pre-added concrete.

[0024] The beneficial effects of this invention are as follows:

[0025] The high-temperature-adaptive concrete hydration temperature rise inhibitor provided by this invention is prepared by melting and mixing sodium tripolyphosphate ascorbate, retarding components, and paraffin wax. Unlike common hydration temperature rise inhibitors, which begin to act in the early stages of mixing and thus affect the induction period of cement hydration, this invention works in the early to mid-stages of hydration. When cement begins to hydrate and the concrete temperature rises to a certain level, paraffin wax melts and releases sodium tripolyphosphate ascorbate and retarding components with hydration-regulating properties, slowing down the cement hydration rate and thus regulating hydration. This method has minimal impact on the induction period and is suitable for use on concrete placed at high temperatures (above 30°C), while ensuring the 28-day compressive strength of the concrete. Detailed Implementation

[0026] The embodiments of the present invention will now be described in detail. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the various embodiments of the invention and various modifications suitable for particular intended applications.

[0027] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, or product that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, or products.

[0028] In various embodiments of the present invention, a variety of hydration temperature rise inhibitors with different proportions and compositions are provided. To demonstrate their excellent performance in suppressing temperature cracks when applied to concrete, the hydration temperature rise inhibitors provided in each embodiment were applied to the concrete preparation process, and the properties of the obtained concrete specimens were measured.

[0029] Example 1:

[0030] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0031] (1) 100g ascorbic acid, 100g sodium trimetaphosphate and 50g tartaric acid were added to 750g water to obtain the first liquid phase. The pH was adjusted to 9 and the reaction was carried out at 40℃ for 2h. The pH was neutralized to 7 and dried at 60℃ to obtain the first solid phase of the retarding component / ester.

[0032] (2) The paraffin wax with a melting point of 44°C, equivalent to 1 / 3 of the mass of the first solid phase, is melted at 60°C to obtain the second liquid phase;

[0033] (3) The second liquid phase is fully immersed in the first solid phase at 60°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0034] Example 2:

[0035] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0036] (1) Add 150g ascorbic acid, 180g sodium trimetaphosphate and 100g citric acid to 570g water to obtain the first liquid phase. Adjust the pH to 11 and react at 60℃ for 4h. Neutralize to pH=7 and dry at 60℃ to obtain the first solid phase of the retarding component / ester.

[0037] (2) The paraffin wax with a melting point of 50°C, equivalent to 1 / 4 of the mass of the first solid phase, is melted at 70°C to obtain the second liquid phase;

[0038] (3) The second liquid phase is fully immersed in the first solid phase at 70°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0039] Example 3:

[0040] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0041] (1) 100g ascorbic acid, 120g sodium trimetaphosphate and 60g glucose were added to 720g water to obtain the first liquid phase. The pH was adjusted to 10 and the reaction was carried out at 50℃ for 3h. The pH was neutralized to 7 and dried at 60℃ to obtain the first solid phase of the retarded component / ester.

[0042] (2) The paraffin wax with a melting point of 46°C, which is equivalent to 1 / 5 of the mass of the first solid phase, is melted at a temperature of 62°C to obtain the second liquid phase;

[0043] (3) The second liquid phase is fully immersed in the first solid phase at 63°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0044] Example 4:

[0045] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0046] (1) 100g ascorbic acid, 109g sodium trimetaphosphate and 90g sorbitol were added to 701g water to obtain the first liquid phase. The pH was adjusted to 10.5 and the reaction was carried out at 44℃ for 2.5h. The pH was neutralized to 7 and dried at 60℃ to obtain the first solid phase of the retarding component / ester.

[0047] (2) The paraffin wax with a melting point of 47°C, which is equivalent to 2 / 7 of the mass of the first solid phase, is melted at a temperature of 65°C to obtain the second liquid phase;

[0048] (3) The second liquid phase is fully immersed in the first solid phase at 64°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0049] Example 5:

[0050] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0051] (1) 140g ascorbic acid, 161g sodium trimetaphosphate and 98g sodium tripolyphosphate were added to 601g water to obtain the first liquid phase. The pH was adjusted to 9.7 and the reaction was carried out at 54℃ for 3.5h. The pH was neutralized to 7 and dried at 60℃ to obtain the first solid phase of the retarding component / ester.

[0052] (2) The paraffin wax with a melting point of 48°C, which is equivalent to 2 / 9 of the mass of the first solid phase, is melted at a temperature of 68°C to obtain the second liquid phase;

[0053] (3) The second liquid phase is fully immersed in the first solid phase at 65°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0054] Example 6:

[0055] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0056] (1) 130g ascorbic acid, 148.2g sodium trimetaphosphate and 78g sodium hexametaphosphate were added to 643.8g water to obtain the first liquid phase. The pH was adjusted to 10.3 and the reaction was carried out at 52℃ for 4h. The pH was neutralized to 7 and dried at 60℃ to obtain the first solid phase of the retarding component / ester.

[0057] (2) The paraffin wax with a melting point of 49°C, equivalent to 5 / 21 of the mass of the first solid phase, was melted at a temperature of 64°C to obtain the second liquid phase;

[0058] (3) The second liquid phase is fully immersed in the first solid phase at 65°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0059] Example 7:

[0060] A method for preparing a high-temperature environment-adaptive concrete hydration temperature rise inhibitor includes the following steps:

[0061] (1) 110g ascorbic acid, 116.6g sodium trimetaphosphate, 44g sodium tripolyphosphate, and 44g glucose were added to 685.4g water to obtain the first liquid phase. The pH was adjusted to 9, and the reaction was carried out at 57℃ for 3.6h. The pH was neutralized to 7 and dried at 60℃ to obtain the first solid phase of the retarding component / ester.

[0062] (2) The paraffin wax with a melting point of 46°C, which is equivalent to 1 / 3 of the mass of the first solid phase, is melted at a temperature of 66°C to obtain the second liquid phase;

[0063] (3) The second liquid phase is fully immersed in the first solid phase at 67°C, and the temperature is slowly reduced to obtain the second solid phase. The second solid phase is then crushed to obtain the hydration temperature rise inhibitor.

[0064] To test the crack resistance of the hydration temperature rise inhibitor obtained above, it was added to the concrete at a rate of 0.4% to 0.6% of the total mass of cementitious materials in the concrete (specific dosages are shown in Table 2 below) to obtain crack-resistant concrete specimens.

[0065] To demonstrate the anti-cracking effect of the hydration temperature rise inhibitor provided in the above embodiments of the present invention when applied to concrete, the following comparative experiments were conducted.

[0066] Comparative Example 1:

[0067] The first concrete comparative specimen was prepared according to the concrete mix proportions shown in Table 1 below. Comparative Example 2:

[0068] According to the concrete mix proportions shown in Table 1 below, and at an addition rate of 0.4% (relative to the dosage in Example 1), ascorbic acid, sodium trimetaphosphate, tartaric acid, and paraffin were directly added to the concrete specimens prepared in the same amount as in Example 1 to make a second concrete comparative specimen.

[0069] Comparative Example 3:

[0070] According to the concrete mix proportions shown in Table 1 below, and at an addition rate of 0.6% (relative to the dosage in Example 2), the first solid phase and paraffin prepared in Example 2 were directly added to the concrete specimens to prepare the third concrete comparative specimen.

[0071] Comparative Example 4:

[0072] According to the concrete mix proportions shown in Table 1 below, and at an addition rate of 0.2%, the sample from Example 1 of CN 104710131A was added to prepare the concrete specimens to make the fourth concrete comparative specimen.

[0073] The concrete specimens obtained in the above embodiments and comparative examples were tested using the following instruments, methods, and standards:

[0074] Unless otherwise specified, in the concrete in which the hydration temperature rise inhibitor provided in the various embodiments of the present invention is applied, the cement used is Conch Cement, and the dosage of the hydration temperature rise inhibitor refers to the mass fraction relative to the total mass of cementitious materials in the concrete.

[0075] In the following embodiments of the present invention, the concrete mix design used for testing compressive strength and setting time is shown in Table 1; the fly ash is Grade I fly ash, the sand is medium sand with a fineness modulus of 2.6 to 2.9, the aggregate is basalt with a particle size of 16 mm to 25 mm, and the pebble is basalt with a particle size of 5 mm to 16 mm. An appropriate water-reducing agent is also added to obtain a suitable concrete state.

[0076] Table 1 Mix Proportions for Concrete Foundations

[0077] Components cement fly ash natural sand Dashi Xiaoshi water <![CDATA[Dosage / kg / m 3 > 340 80 729 765 328 152

[0078] The rate of heat release during cement hydration was determined using a TAM AIR isothermal calorimeter from TA Instruments, Inc. (USA). The test temperature was 30℃, and the test specimen was neat cement paste with a water-cement ratio of 0.4.

[0079] The reduction in the peak value of the maximum heat release rate was used as the criterion for determining the hydration temperature rise inhibitor of this invention. Under the same conditions, the greater the reduction in the peak value of the heat release rate, the better the cement hydration control performance. The test method was performed in accordance with GB / T 2022-1980.

[0080] The compressive strength and setting time of concrete shall be performed in accordance with GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete".

[0081] The test results obtained from each embodiment and comparative example are shown in Table 2 below.

[0082] Table 2. Experimental data from different embodiments and comparative examples.

[0083]

[0084] As can be seen from the experimental data in Table 2, compared with the first concrete control block without any crack-resistant materials in Comparative Example 1, the second concrete control block with the same amount of ascorbic acid, sodium trimetaphosphate, retarder and paraffin directly added in Comparative Example 2, the third concrete control block with the same amount of the first solid phase and paraffin directly added in Comparative Example 3, and the fourth concrete control block with 0.2% of the sample from Example 1 of CN 104710131A directly added in Comparative Example 4, the hydration temperature rise inhibitors provided in each embodiment of the present invention can significantly reduce the peak value of the maximum hydration rate without affecting the compressive strength, by allowing the paraffin to melt and release the combined ascorbic acid sodium trimetaphosphate ester compound and retarder when the specimen temperature reaches above 40°C. The inhibitors have little effect on the induction period and play a role in hydration regulation, especially suitable for concrete components with a placement temperature above 30°C.

[0085] Although the invention has been shown and described with reference to specific embodiments, those skilled in the art will understand that various changes in form and detail may be made herein without departing from the spirit and scope of the invention as defined by the claims and their equivalents.

Claims

1. A high-temperature environment-adaptive concrete hydration temperature rise inhibitor, characterized in that, The concrete hydration temperature rise inhibitor is a solid powder prepared from a solid mixture of sodium tripolyphosphate ascorbate and retarding components, and molten paraffin. The sodium trimetaphosphate ascorbate esters are ester compounds formed by sodium trimetaphosphate and ascorbic acid under alkaline conditions; The paraffin wax has a melting point of 44℃-50℃.

2. The high-temperature environment-adaptive concrete hydration temperature rise inhibitor according to claim 1, characterized in that, The retarding component is selected from any one or more of tartaric acid, citric acid, glucose, sorbitol, sodium tripolyphosphate, and sodium hexametaphosphate.

3. The preparation method of a high-temperature environment-adaptive concrete hydration temperature rise inhibitor as described in claim 1 or 2, characterized in that, It includes the following steps: (1) Add ascorbic acid, sodium trimephosphate and retarding component into water to obtain the first liquid phase. Adjust the pH to 9-11 and react at 40℃~60℃ for 2h~4h. Neutralize to pH=7 and dry at 60℃ to obtain the first solid phase of retarding component / ester. (2) The paraffin wax with a melting point of 44℃-50℃ is melted at a temperature of 60℃-70℃ to obtain the second liquid phase; (3) After fully wetting the first solid phase with the second liquid phase at a temperature of 60℃-70℃, stop heating and slowly cool to room temperature to obtain the second solid phase. Crush the second solid phase to obtain the hydration temperature rise inhibitor.

4. The preparation method according to claim 3, characterized in that, In the first liquid phase, the mass fraction of ascorbic acid is 10%–15%, the mass fraction of sodium trimetaphosphate is 10%–18%, and the mass fraction of the retarding component is 5%–10%. The mass ratio of the second liquid phase to the first solid phase is 1:3 to 5.

5. The preparation method according to claim 3, characterized in that, The cooling rate in step (3) shall not exceed 2℃ / min.

6. The application of the high-temperature environment-adaptive concrete hydration temperature rise inhibitor as described in claim 1 or 2 in concrete.

7. The application according to claim 6, characterized in that, The aforementioned hydration temperature rise inhibitor can be added to the concrete at a dosage of 0.4% to 0.6% of the total mass of cementitious materials in the pre-added concrete.

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