Inorganic binder stabilized material accelerated curing technique

Abstract

The application provides an inorganic binder stable material accelerated curing technology, and the specific steps are as follows: first stage: the inorganic binder stable material is placed in an environment with a relative humidity of 95-100%, and is heated to 60-80 DEG C at room temperature, and is cured and maintained, and the curing time is 3-5h; second stage: the temperature is decreased to 20-30 DEG C in the environment with a relative humidity of 95-100%, and is cured and maintained, and the curing time is 24-72h; third stage: the temperature is increased to 60-80 DEG C in the environment with a relative humidity of 60-80%, and the air pressure is more than 80% of the material strength design value and does not exceed 2.5MPa, and is cured and maintained, and the curing time is 72-336h. The application ensures that the test results accurately and reliably reflect the material performance based on the maturity formula, and has important social and economic benefits for guiding engineering design and construction and improving engineering construction efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of methods for curing, solidification or hardening, and specifically relates to an accelerated curing technology for inorganic binder stabilized materials. Background Technology

[0002] Inorganic binder stabilized material is a mixture made by mixing aggregates with inorganic binders such as cement, lime, and fly ash, adding water, and then compacting and curing it. Due to its high strength, good stability, and excellent self-contained slab structure, it is widely used in the base course of highways and urban roads at all levels.

[0003] However, given the objective fact that the properties of inorganic binder stabilized materials increase with age, current construction specifications impose age requirements on properties such as flexural strength and resilient modulus (90 days for cement-based materials and 180 days for lime-based materials). This creates a significant contradiction with the demands of the rapidly developing transportation infrastructure construction. The current standard, "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG 3441-2024), provides standard and rapid curing methods for inorganic binder stabilized materials. However, the rapid curing method involves a cumbersome process for determining the corresponding short curing age, and the method of establishing a strength-age curve based on compressive strength remains debatable.

[0004] Currently, most research on the curing process of inorganic binder stabilized materials focuses on the impact of the curing process on changes in material properties. Given the diversity of materials and the complexity of the environment, no complete and unified conclusions have yet been reached. Related reports mainly focus on improvements in on-site construction techniques and curing equipment, with relatively little attention paid to curing methods themselves.

[0005] Developing new and efficient inorganic binder stabilized materials and accelerated curing technology is of great significance as it can guide engineering design and construction, significantly improve engineering construction efficiency, and bring good social and economic benefits. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an accelerated curing technology for inorganic binder stabilized materials. This method can significantly reduce the curing time of inorganic binder stabilized materials and has the advantages of simple process and stable binder performance. It can be used to guide engineering design and construction, improve engineering construction efficiency, and has high social and economic benefits.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An accelerated curing technology for inorganic binder stabilized materials is disclosed, which employs a staged curing method to achieve accelerated curing of inorganic binder stabilized materials. The specific steps are as follows:

[0009] First stage: Place the inorganic binder stabilized material in an environment with a relative humidity of 95-100%, and heat it to 60-80℃ at a heating rate of 20-30℃ / h at room temperature, and keep it warm for curing. The curing time of the first stage (including the time consumed in the heating process) is 3-5 hours.

[0010] Second stage: In an environment with a relative humidity of 95-100%, cool down to 20-30℃ at a cooling rate of 20-30℃ / h, and keep warm for curing. The curing time in the second stage (including the time consumed by the cooling process) is 24-72 hours.

[0011] The third stage: In an environment with a relative humidity of 60-80% and an air pressure of more than 80% of the material's design strength value but not exceeding 2.5 MPa, the temperature is raised to 60-80℃ at a heating rate of 20-30℃ / h, and then kept warm for curing. The curing time in the third stage (including the time consumed during the heating process) is 72-336 hours.

[0012] According to the above scheme, the inorganic binder stabilizing material includes lime-stabilized materials, cement-stabilized materials, and industrial waste residue (such as fly ash) stabilizing materials.

[0013] According to the above scheme, the environment with a relative humidity of 95-100% is achieved by atomized spraying, and immersion in water is prohibited.

[0014] According to the above scheme, when the inorganic binder stabilized material is a cement-stabilized material, the curing temperature of the first, second, and third stages shall be the lower limit value; when the inorganic binder stabilized material is other stabilized materials, the curing temperature of the first, second, and third stages shall be the upper limit value.

[0015] According to the above scheme, when the inorganic binder stabilized material is a cement-stabilized material and the material strength design value is higher than 3.0 MPa, the curing time of the first stage and the second stage shall be the middle value; when the material strength design value is lower than 3.0 MPa, the curing time of the first stage and the second stage shall be the lower limit value; when the inorganic binder stabilized material is other stabilized materials, the curing time of the first stage and the second stage shall be the upper limit value.

[0016] According to the above scheme, the third stage is an environment where the air pressure is more than 80% of the material strength design value and does not exceed 2.5 MPa, the pressurization rate is 0.2 ± 0.02 MPa / h, and the pressure fluctuation value during the pressure stabilization process does not exceed ± 0.2 MPa.

[0017] According to the above scheme, the maintenance time for the third stage is calculated using the following formulas (1) and (2):

[0018] M 标 ≤t1×T1+k2×t2×T2+k3×t3×T3×k4 (1)

[0019] k3=P / P0 (2)

[0020] In the above formula, M 标 For inorganic binder stabilized materials, the standard curing maturity is 42720℃·h for cement-stabilized materials and 85920℃·h for other stabilized materials. 标 Method of determination: Cement-stabilized materials: 20℃×89(d)×24h=42720℃·h (the last day of immersion in water is not included in the curing time); other stabilized materials: 20℃×179(d)×24h=85920℃·h.

[0021] t1, t2, and t3 are the curing times for the first, second, and third stages, respectively, in hours. The value of t3 is calculated based on the above formula and rounded up to the nearest integer, and must be ≥72 hours.

[0022] T1, T2, and T3 are the curing temperatures for the first, second, and third stages, respectively, in °C.

[0023] k2 is the reaction coefficient for the second stage, with a value of 4.029;

[0024] k3 is the pressure response coefficient for the third stage;

[0025] k4 is the structural reaction coefficient for the third stage, which is 0.35 for cement-stabilized materials and 0.5 for other inorganic binder-stabilized materials.

[0026] P is the air pressure in the curing space, in MPa;

[0027] P0 is standard atmospheric pressure (101.325 kPa), MPa.

[0028] The present invention also includes the application of the above-mentioned inorganic binder stabilized material accelerated curing technology in the field of concrete.

[0029] Cement hydration is divided into three stages: The first stage (initiation and induction) is the dissolution or rapid hydration stage. After cement particles come into contact with water, the surface of the cement particles begins to dissolve, releasing calcium ions, silicate ions, and hydroxide ions. These ions react with ions present in the water to form hydration products. This process is completed within minutes to hours. The second stage (acceleration) is the moderate hydration stage. Cement particles continue to react with water, forming more hydration products. The silicate minerals in the cement gradually hydrolyze and crystallize, forming the cement stone skeleton. This process is completed within hours to days. The third stage (deceleration and decay) is when the reaction between cement particles and water gradually slows down, with only a small amount of hydration reaction occurring. This process can last for months or years. The strength and hardness of the cement stone will still increase, but at a very slow rate.

[0030] This invention, based on the strength formation mechanism of inorganic binder stabilized materials, proposes a staged curing method and controls the curing effect by adjusting the curing maturity to achieve accelerated curing of inorganic binder stabilized materials. By adjusting the curing conditions (temperature, humidity, and air pressure) at each stage, the performance of inorganic binder stabilized materials is rapidly improved to the greatest extent. Taking cement-stabilized materials as an example, in the first stage of curing, the material is essentially provided with sufficient water molecules through a high-temperature and high-humidity environment to accelerate the dissolution of cement particles and ion exchange. The curing time is determined to be 3-5 hours. In the second stage, cement hydration is an exothermic reaction, so the ambient temperature is lowered while maintaining a high-humidity environment to promote the forward hydration reaction and the full growth of crystal nuclei. The first stage involves the formation of a complete three-dimensional skeleton structure, lasting 1-3 days. The third stage of curing time is calculated and determined based on the maturity formula. Taking advantage of the well-developed pores of inorganic binder stabilized materials, high pressure and high temperature environment are applied for curing. On the one hand, this physically improves the density of the structure compared to traditional curing methods. More importantly, water molecules can more easily enter the interior of the structure, allowing the originally slow, gradual reaction process from the outside to the inside to occur simultaneously from the inside and outside. Therefore, this greatly accelerates the formation of a dense skeleton structure of the inorganic binder stabilized material. By controlling the curing time of the material based on the maturity formula, the test results can accurately and reliably reflect the performance of the material itself, thereby achieving the goal of shortening the curing age of inorganic binder stabilized materials.

[0031] Correspondingly, the structural strength of other inorganic binder stabilized materials (such as lime and fly ash stabilized materials) comes from the ion exchange in lime and fly ash to form a coagulated-crystallized network structure. There is also a consolidation effect of calcium hydroxide reacting with carbon dioxide to form calcium carbonate. Compared with the hydration reaction of cement, its reaction rate is relatively slow. Therefore, the curing time in this invention is all at the upper limit.

[0032] In this invention, the temperature of the curing environment at each stage adopts a gradual change mode, with a heating / cooling rate of 20-30℃ / h. The rapid change in ambient temperature will cause a temperature difference between the inside and the surface of the material, resulting in differences in the internal and external properties of the material and reducing the overall uniformity of the material properties. On the other hand, in areas with excessive temperature difference, stress concentration will form, which will easily lead to brittle fracture and a decrease in material strength.

[0033] Currently, existing maturity equations for cement concrete curing, such as the Nuese-Saul maturity equation and the equivalent age maturity function based on the Arrhenius function, are extremely complex. The maturity calculation formula provided by this invention is simply expressed as the product of curing temperature and time, making the calculation convenient. After determining the curing temperature and curing time for the first and second stages, the curing time for the third stage is calculated according to equations (1) and (2). Curing maturity mainly involves controlling the curing time of the third stage. The core objective of this invention is to shorten the curing time of inorganic binders while ensuring their stable material properties, thereby improving experimental efficiency and avoiding delays in construction progress.

[0034] The present invention has the following beneficial effects:

[0035] 1. This invention fully utilizes the basic principles of crystallization and ion exchange in inorganic binders such as cement hydration and fly ash, designs positive environmental conditions to meet the requirements of rapid and sufficient reaction, and ensures that the test results accurately and reliably reflect the material properties based on the maturity formula. It has significant socio-economic benefits for guiding engineering design and construction and improving engineering construction efficiency. Existing curing methods require 3 months of curing, which causes serious delays in design and construction. The curing technology of this invention can significantly shorten the engineering construction cycle and reduce construction costs.

[0036] 2. The health preservation technology of this invention has the advantages of simple process and stable performance of the obtained binder, and is easy to implement with high feasibility. Attached Figure Description

[0037] Figure 1 Example 1 uses 4% cement-stabilized crushed stone as the inorganic binder stabilizing material. The fitting curves of unconfined compressive strength (MPa) versus curing time (h) and flexural tensile strength (MPa) versus curing time (h) are obtained under standard curing and staged accelerated curing conditions, respectively.

[0038] Figure 2 Example 2 uses 5% cement-stabilized crushed stone as the inorganic binder stabilizing material. The fitting curves of unconfined compressive strength (MPa) versus curing time (h) and flexural tensile strength (MPa) versus curing time (h) are obtained under standard curing and staged accelerated curing conditions, respectively.

[0039] Figure 3 Example 3 uses lime-stabilized granules as the inorganic binder stabilizing material. The fitting curves of unconfined compressive strength (MPa) versus curing time (h) and flexural tensile strength (MPa) versus curing time (h) are obtained under standard curing and staged accelerated curing conditions, respectively. Detailed Implementation

[0040] To better understand this invention, the following embodiments further illustrate its content. In these embodiments, the long-term properties of inorganic binder stabilized materials, such as flexural strength and compressive resilient modulus, are used as indicators to verify the curing effect. Examples 1-3 respectively use 4% cement-stabilized crushed stone, 5% cement-stabilized crushed stone, and lime-fly ash stabilized aggregate as research objects, testing the strength change patterns of different inorganic binder stabilized materials at different curing stages. A blank control group (standard curing: 20℃, RH≥95%) is set up to verify the curing effect. Furthermore, the content of this invention is not limited to the following embodiments.

[0041] Example 1

[0042] An accelerated curing technology for inorganic binder stabilized materials is proposed, using 4% cement-stabilized crushed stone as the implementation material, with a design strength of 2.5 MPa. The cement used is 32.5 grade ordinary Portland cement, and the aggregate is basalt. Both the raw materials and gradation meet current specifications. The maximum dry density of the mixture is 2.304 g / cm³. 3 The optimal moisture content was 4.9%, and cylindrical and beam specimens were formed according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering (JTG 3441-2024)". The 7-day unconfined compressive strength and 90-day flexural tensile strength were selected as the test indicators for curing effect.

[0043] It employs a phased curing method to accelerate the curing of inorganic binder stabilized materials. The specific steps are as follows:

[0044] First stage: Place 4% cement-stabilized crushed stone in an environment with a relative humidity of 96%, and heat it to 60℃ at a heating rate of 30℃ / h at room temperature, and keep it warm for 3 hours.

[0045] Second stage: In an environment with a relative humidity of 96%, the temperature is reduced to 20℃ at a rate of 30℃ / h, and then kept warm for 24 hours.

[0046] The third stage: Under an environment with a relative humidity of 70% and an air pressure of 2MPa (pressurization rate of 0.2±0.02MPa / h, with pressure fluctuation not exceeding ±0.2MPa during the pressure stabilization process), the temperature is increased to 60℃ at a rate of 30℃ / h, and then kept warm for curing. The curing time for the third stage is 98 hours. To ensure consistency with current standards and specifications, on the last day of the curing period, the specimens are removed from the curing chamber, allowed to air dry to room temperature (about 2 hours), weighed, and then immersed in a constant temperature water bath at 20±2℃ for 24 hours. After immersion, the specimens are removed and relevant tests are conducted immediately.

[0047] Determination of curing time: Since it is a cement-stabilized material and the design strength is less than 3.0 MPa, the lower limit of the curing time is taken. The first stage is 3 hours, the second stage is 24 hours, and the third stage is calculated according to formula (1) and formula (2). M of cement-stabilized material 标 The value is 42720℃·h. The calculation result is rounded up to the nearest integer and is not less than 72h. After calculation, t3≥98.0h, so 98h is taken.

[0048] Determining the curing temperature: For cement-based stabilized materials, the lower limit of the temperature range is 60℃ (high temperature environment) and 20℃ (normal temperature environment). At the same time, the temperature change process of the curing environment should be carried out in a gradual manner, with a heating / cooling rate of 30℃ / h.

[0049] In this embodiment, seven sets of cylindrical and beam specimens were prepared according to the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTG 3441-2024. The specific curing conditions are shown in Table 1.

[0050] Table 1

[0051]

[0052] Since the curing time of specimens 2-1 and 3-1 was relatively short, specimens 2-1 and 3-1 were first cured at 20℃ and RH≥95% for 12 hours before performance testing. During the curing process, the surface of the specimens was covered with a layer of water film. After that, they were immersed in water for 12 hours before the specimens were taken out to carry out relevant tests.

[0053] The test results of the unconfined compressive strength and flexural strength of the specimens prepared in this embodiment are shown in Table 2.

[0054] Table 2

[0055] 1 3.2 (Cylindrical, 7d) 1.52 (beam type, 90d) 2-1 0.3 0.18 2-2 1.3 0.26 2-3 2.2 0.48 3-1 1.1 0.36 3-2 2.2 0.84 3-3 3.5 1.76

[0056] As shown in Table 2, the performance test results of specimen (3-3) using the phased curing method are higher than those of specimen (1) under the same curing time under standard curing conditions, indicating that phased curing can accelerate the performance improvement of cement-stabilized crushed stone. Furthermore, comparing (3-1), (3-2), and (3-3), it can be seen that the curing strength of the specimens increases after each curing stage. The strength after the first and second stages still does not reach the design value, while the strength after the third stage is slightly higher than the strength under standard curing conditions, indicating that the phased curing method based on maturity theory is accurate and feasible.

[0057] Based on the test results in Table 2, the fitting functions of unconfined compressive strength (y, unit MPa) and curing time (x, unit h) under standard curing and phased accelerated curing conditions, as well as the fitting functions of flexural strength (z, unit MPa) and curing time (x, unit h), are obtained and are shown in Table 3 below.

[0058] Table 3

[0059]

[0060] like Figure 1 The figures shown are the fitting curves of unconfined compressive strength (MPa) versus curing time (h) and flexural tensile strength (MPa) versus curing time (h) under standard curing and phased accelerated curing conditions, obtained according to the test results in Table 2 in this embodiment. The horizontal axis represents curing time, and the vertical axis represents strength. Figure 1 As shown in Table 3, the strength growth curve of 4% cement-stabilized crushed stone initially increases in slope and then decreases, with the curve showing a trend towards flattening. This is because before the curing process, after cement is mixed with water and aggregates, the mineral particles in the cement come into contact with water, and water molecules are quickly adsorbed onto the particle surface, undergoing a hydration reaction. The hydration products formed form a shielding layer on the surface of the mineral particles, reducing the reaction rate. As the first stage of the curing process begins, the high temperature and humidity environment accelerates the movement of water molecules, promotes the dissolution of cement mineral particles, and the ion concentration in the solution continuously increases. The increased osmotic pressure accelerates the rupture of the shielding membrane, promoting the formation and growth of crystal nuclei in a short period of time. Therefore, macroscopically, this manifests as a gradual increase in the strength growth rate of the specimen. As the curing process progresses, a large number of crystal nuclei are continuously formed and grow, and the exothermic reaction reaches its peak. Therefore, lowering the curing environment temperature is beneficial to the forward movement of the reaction and the full growth of crystal nuclei, forming a complete three-dimensional skeleton structure. At this stage, the cement hydration reaction rate also reaches its peak. Analysis shows that the strength growth rate of the specimens using this method is higher than that under standard curing conditions during the third stage of curing. This is because the key factor determining the strength growth of the specimens in the third stage is the ion diffusion rate in the solution. The pressure environment applied in this method allows the process of gradually reacting from the outside to the inside, which is originally slow, to occur simultaneously from the inside and outside. Therefore, it greatly accelerates the formation of a dense structure of the inorganic binder stabilized material skeleton.

[0061] Example 2

[0062] An accelerated curing technology for inorganic binder stabilized materials is proposed, using 5% cement-stabilized crushed stone as the implementation material, with a design strength of 4.0 MPa. The cement used is 32.5 ordinary Portland cement, and the aggregate is basalt. Both the raw materials and gradation meet current specifications, and the maximum dry density of the mixture is 2.326 g / cm³. 3 The optimal moisture content was 4.7%, and cylindrical and beam specimens were formed according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering (JTG 3441-2024)". The 7-day unconfined compressive strength and 90-day flexural tensile strength were selected as the indicators for testing the curing effect.

[0063] It employs a phased curing method to accelerate the curing of inorganic binder stabilized materials. The specific steps are as follows:

[0064] First stage: Place 5% cement-stabilized crushed stone in an environment with a relative humidity of 96%, and heat it to 60℃ at a heating rate of 30℃ / h at room temperature, and keep it warm for 4 hours.

[0065] Second stage: In an environment with a relative humidity of 96%, the temperature is reduced to 20℃ at a rate of 30℃ / h, and then kept warm for curing. The curing time for the second stage is 48 hours.

[0066] The third stage: Under an environment with a relative humidity of 70% and an air pressure of 2.5 MPa (pressurization rate of 0.2 ± 0.02 MPa / h, with pressure fluctuation not exceeding ± 0.2 MPa during the pressure stabilization process), the temperature is increased to 60℃ at a rate of 30℃ / h, and then kept warm for curing. The curing time for the third stage is 75 hours. To ensure consistency with current standards and specifications, on the last day of the curing period, the specimens are removed from the curing chamber, allowed to air dry to room temperature (about 2 hours), weighed, and then immersed in a constant temperature water bath at 20 ± 2℃ for 24 hours. After immersion, the specimens are removed and relevant tests are conducted immediately.

[0067] Determination of curing time: Since it is a cement-stabilized material and the design strength is less than 3.0 MPa, the lower limit of the curing time is taken. The first stage is 3 hours, the second stage is 24 hours, and the third stage is calculated according to formula (1) and formula (2). M of cement-stabilized material 标 The value is 42720℃·h. The calculation result is rounded up to the nearest integer and is not less than 72h. After calculation, t3≥74.6h, so we take 75h.

[0068] Determining the curing temperature: For cement-based stabilized materials, the lower limit of the temperature range is 60℃ (high temperature environment) and 20℃ (normal temperature environment). At the same time, the temperature change process of the curing environment should be carried out in a gradual manner, with a heating / cooling rate of 30℃ / h.

[0069] In this embodiment, seven sets of cylindrical and beam specimens were prepared according to the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTG 3441-2024. The specific curing conditions are shown in Table 4.

[0070] Table 4

[0071]

[0072] Since the curing time of specimens 5-1 and 6-1 was relatively short, specimens 5-1 and 6-1 were first placed at 20℃ and RH≥95% for 12 hours before performance testing. During the curing process, the surface of the specimens was covered with a layer of water film. After that, they were immersed in water for 12 hours before the specimens were taken out and the relevant tests were carried out.

[0073] The test results of the unconfined compressive strength and flexural strength of the specimens prepared in this embodiment are shown in Table 5.

[0074] Table 5

[0075] 4 4.3 (Cylindrical, 7d) 1.89 (beam type, 90d) 5-1 0.6 0.21 5-2 1.8 0.44 5-3 2.8 0.59 6-1 1.3 0.39 6-2 2.9 1.03 6-3 4.5 1.79

[0076] As shown in Table 5, after 127 hours of curing using the phased curing method described in this invention, the performance of the mixture is close to that after 90 days of standard curing, indicating that the method described in this invention meets the construction performance requirements. Meanwhile, compared with Example 1, the increased cement content in the material system led to a significant increase in the compressive strength of the mixture, while the flexural strength remained lower than that after 90 days of standard curing. This may be due to the increased cement hydration products in the mixture, forming a shielding layer that reduces the ion exchange rate in the solution, thus decreasing the flexural strength of the mixture to some extent.

[0077] Based on the test results in Table 5, the fitting functions of unconfined compressive strength (y, unit MPa) and curing time (x, unit h) under standard curing and phased accelerated curing conditions, as well as the fitting functions of flexural strength (z, unit MPa) and curing time (x, unit h), are obtained and are shown in Table 6 below.

[0078] Table 6

[0079]

[0080] like Figure 2 The figures shown are the fitting curves of unconfined compressive strength (MPa) versus curing time (h) and flexural tensile strength (MPa) versus curing time (h) under standard curing and phased accelerated curing conditions, obtained according to the test results in Table 5 in this embodiment. The horizontal axis represents curing time, and the vertical axis represents strength. Figure 2 As shown in Table 6, the strength growth curve of 5% cement-stabilized crushed stone is more significant than that of 4% cement-stabilized crushed stone in Example 1. This is because the increase in cement content leads to an increase in hydration products in the mixture and a more dense skeleton structure.

[0081] Example 3

[0082] An accelerated curing technology for inorganic binder stabilized materials is proposed, using lime-fly ash stabilized granular material (lime:fly ash:gravel = 12:30:58) as the implementation material, with a design strength of 1.0 MPa, an effective calcium and magnesium content of 85.6% in lime, and a fly ash specific gravity of 2.28 g / cm³. 3 Dry density 0.9 g / cm³ 3 The raw materials and gradation both meet current specifications. The maximum dry density of the mixture is 1.859 g / cm³. 3 The optimal moisture content was 8.3%, and cylindrical and beam specimens were formed according to the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering (JTG3441-2024)". The 7-day unconfined compressive strength and 90-day flexural tensile strength were selected as the indicators for testing the curing effect.

[0083] It employs a phased curing method to accelerate the curing of inorganic binder stabilized materials. The specific steps are as follows:

[0084] First stage: Place the lime-stabilized aggregate in an environment with a relative humidity of 96%, and heat it to 80℃ at a heating rate of 30℃ / h at room temperature, and keep it warm for 5 hours.

[0085] Second stage: In an environment with a relative humidity of 96%, the temperature is reduced to 30℃ at a rate of 30℃ / h, and then kept warm for curing. The curing time for the second stage is 72 hours.

[0086] The third stage: Under an environment with a relative humidity of 70% and an air pressure of 0.8 MPa (pressurization rate of 0.2 ± 0.02 MPa / h, with pressure fluctuation not exceeding ± 0.2 MPa during the pressure stabilization process), the temperature is increased to 80℃ at a rate of 30℃ / h, and then kept warm for curing. The curing time for the third stage is 244 hours. To ensure consistency with current standards and specifications, on the last day of the curing period, the specimens are removed from the curing chamber, allowed to air dry to room temperature (about 2 hours), weighed, and then immersed in a constant temperature water bath at 20 ± 2℃ for 24 hours. After immersion, the specimens are removed and relevant tests are conducted immediately.

[0087] Determination of curing time: Since it is a type of other stabilized material and the design strength is less than 3.0 MPa, the upper limit of the curing time is taken. The first stage is 5 hours, the second stage is 72 hours, and the third stage is calculated according to formula (1) and formula (2). M of other stabilized materials 标 The value is taken as 85920℃·h. The calculation result is rounded up to the nearest integer and is not less than 72h. After calculation, t3≥243.2h, so we take 244h.

[0088] Determining the curing temperature: For cement-based stabilized materials, the lower limit of the temperature range is 60℃ (high temperature environment) and 20℃ (normal temperature environment). At the same time, the temperature change process of the curing environment should be carried out in a gradual manner, with a heating / cooling rate of 30℃ / h.

[0089] In this embodiment, seven sets of cylindrical and beam-shaped specimens were prepared, and their specific curing conditions are shown in Table 7.

[0090] Table 7

[0091]

[0092]

[0093] Since the curing time of specimens 8-1 and 9-1 was relatively short, specimens 8-1 and 9-1 were first cured at 20℃ and RH≥95% for 12 hours before performance testing. During the curing process, the surface of the specimens was covered with a layer of water film. After that, they were immersed in water for 12 hours before the specimens were taken out and the relevant tests were carried out.

[0094] The test results of the unconfined compressive strength and flexural strength of the specimens prepared in this embodiment are shown in Table 8.

[0095] Table 8

[0096] 0 1.8 (cylindrical, 7d) 1.21 (Beam type, 180d) 1-1 0.2 0.10 1-2 0.5 0.16 1-3 2.2 0.44 2-1 0.4 0.15 2-2 1.5 0.26 2-3 2.8 1.35

[0097] As shown in Table 8, the strength growth of lime-stabilized aggregates varies significantly under different curing conditions. The staged curing method described in this invention can effectively accelerate the growth of its skeletal structure, especially in the third stage of curing. Furthermore, using the accelerated curing method of this invention, the strength achieved in 321 hours of curing exceeds that of standard curing after 180 days, demonstrating the practicality and feasibility of the staged curing method of this invention.

[0098] Based on the test results in Table 8, the fitting functions of unconfined compressive strength (y, unit MPa) and curing time (x, unit h) under standard curing and phased accelerated curing conditions, as well as the fitting functions of flexural strength (z, unit MPa) and curing time (x, unit h), are obtained and are shown in Table 9 below.

[0099] Table 9

[0100]

[0101] like Figure 3 The figures shown are the fitting curves of unconfined compressive strength (MPa) versus curing time (h) and flexural tensile strength (MPa) versus curing time (h) under standard curing and phased accelerated curing conditions, obtained according to the test results in Table 8 in this embodiment. The horizontal axis represents curing time, and the vertical axis represents strength. Figure 3 As shown in Table 9, the strength growth pattern of lime-fly ash stabilized aggregate is similar to that of cement-stabilized crushed stone. However, the strength growth rate of lime-fly ash stabilized materials is lower, which is because the crystallization rate of lime and fly ash is significantly lower than that of cement hydration reaction.

Claims

1. A method for accelerating the curing of inorganic binder-stabilized materials, characterized in that, It employs a phased curing method to accelerate the curing of inorganic binder stabilized materials. The specific steps are as follows: First stage: Place the inorganic binder stabilized material in an environment with a relative humidity of 95~100%, and heat it to 60~80℃ at a heating rate of 20~30℃ / h at room temperature, and keep it warm for curing. The curing time for the first stage is 3~5 hours. Second stage: In an environment with a relative humidity of 95~100%, cool down to 20~30℃ at a cooling rate of 20~30℃ / h, and keep warm for curing. The curing time for the second stage is 24~72 hours. The third stage: In an environment with a relative humidity of 60-80% and an air pressure of more than 80% of the material strength design value and not exceeding 2.5MPa, the temperature is raised to 60-80℃ at a heating rate of 20-30℃ / h, and then kept warm for curing. The curing time for the third stage is 72-336h. The inorganic binder stabilized materials include lime stabilized materials, cement stabilized materials, and industrial waste stabilized materials; The maintenance time for the third stage is calculated according to formulas (1) and (2): M 标 ≤t1×T1+k2×t2×T2+k3×t3×T3×k4(1) k3=P / P0(2) In the above formula, M 标 For inorganic binder stabilized materials, the standard curing maturity is 42720℃·h for cement-stabilized materials and 85920℃·h for other stabilized materials. 标 Determination method: Cement-stabilized materials: 20℃ × 89 × 24h = 42720℃·h; Other stabilized materials: 20℃ × 179 × 24h = 85920℃·h; t1, t2, and t3 are the curing times for the first, second, and third stages, respectively, in hours. The value of t3 is calculated based on the above formula and rounded up to the nearest integer, and must be ≥72 hours. T1, T2, and T3 are the curing temperatures for the first, second, and third stages, respectively, in °C. k2 is the reaction coefficient for the second stage, with a value of 4.029; k3 is the pressure reaction coefficient in the third stage; k4 is the structural reaction coefficient for the third stage, which is 0.35 for cement-stabilized materials and 0.5 for other inorganic binder-stabilized materials. P is the air pressure in the curing space, in MPa; P0 is standard atmospheric pressure, MPa.

2. The method for accelerating the curing of inorganic binder stabilized materials according to claim 1, characterized in that, The relative humidity of 95-100% is achieved by atomized spraying; immersion in water is prohibited.

3. The method for accelerating the curing of inorganic binder stabilized materials according to claim 1, characterized in that, When the inorganic binder stabilized material is a cement-stabilized material, the curing temperatures for the first, second, and third stages shall be the lower limit values; when the inorganic binder stabilized material is another type of stabilized material, the curing temperatures for the first, second, and third stages shall be the upper limit values.

4. The method for accelerating the curing of inorganic binder stabilized materials according to claim 1, characterized in that, When the inorganic binder stabilized material is a cement-stabilized material and the material strength design value is higher than 3.0 MPa, the curing time of the first and second stages shall be the median value; when the material strength design value is lower than 3.0 MPa, the curing time of the first and second stages shall be the lower limit value. When the inorganic binder stabilized material is other stabilized materials, the curing time of the first and second stages shall be the upper limit value.

5. The method for accelerating the curing of inorganic binder stabilized materials according to claim 1, characterized in that, The third stage is an environment where the air pressure is more than 80% of the material strength design value and does not exceed 2.5 MPa, the pressurization rate is 0.2 ± 0.02 MPa / h, and the pressure fluctuation value during the pressure stabilization process does not exceed ± 0.2 MPa.

6. The application of the method for accelerating curing of inorganic binder stabilized materials according to any one of claims 1-5 in the field of concrete.

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