Method for quickly optimizing mix proportion of precast concrete member

Abstract

The present disclosure relates to the technical field of precast concrete, and provides a method for quickly optimizing the mix proportion of a precast concrete component, comprising: determining a concrete standard curing design strength and a concrete quick precast curing design strength that the precast concrete component needs to reach; predetermining a mix proportion of concrete, and preparing two groups of concrete test pieces according to the mix proportion; curing the concrete test pieces by using an actual quick precast curing method and a constant-temperature quick curing mode, and then measuring the strength of the concrete test pieces by using a standard test method after the curing ends; and comparing the measured strength with the design required strength until the requirement is met. By using the present disclosure, the test and adjustment period of the concrete can be greatly shortened, the production progress of the precast component is accelerated, the problem of a long optimization period of the mix proportion of the traditional precast concrete component is solved, the dependence of the adjustment of the mix proportion of the concrete on engineering experience is reduced, and the present disclosure has good scientific guidance and promotion value.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of precast concrete, in particular to a method for quickly optimizing the mix proportion of a precast concrete member. BACKGROUND

[0002] The precast concrete technology is one of the important technologies for practicing the green and low-carbon concept and realizing the industrialization of bridges, and the rapid curing process such as steam curing is the core means of the precast concrete technology. The rapid curing is beneficial to improving the turnover rate of the mold, improving the utilization rate of the main process equipment and the labor productivity, shortening the production cycle, and reducing the product cost.

[0003] In the process of designing and adjusting the mix proportion of the factory-precast concrete member, the concrete compressive strength obtained by the standard curing for 28 days is still the key quality parameter for evaluating the qualification of the concrete member and the acceptance basis. However, the concrete compressive strength obtained by the standard curing for 28 days needs 28 days, and due to the long curing period, the mix proportion of the concrete cannot be designed and adjusted in time, and the quality status in the production and preparation of the precast member cannot be predicted in time.

[0004] In addition, the current research method for optimizing the mix proportion of the concrete mainly focuses on the traditional orthogonal design test method, which has many limitations, a limited experimental search range, a long research time, a high cost, and cannot obtain an ideal and practical optimization result of the mix proportion.

[0005] Therefore, it is necessary to develop a scientific and rapid method for optimizing the mix proportion of the precast concrete member. SUMMARY

[0006] (I) Technical problem to be solved

[0007] Therefore, the main purpose of the present disclosure is to provide a method for quickly optimizing the mix proportion of a precast concrete member, so as to solve the problem of long optimization period of the traditional precast concrete member mix proportion, and reduce the dependence of the adjustment of the concrete mix proportion on engineering experience.

[0008] (II) Technical scheme

[0009] To achieve the above purpose, the present disclosure provides a method for quickly optimizing the mix proportion of a precast concrete member, which comprises the following steps:

[0010] determining the concrete standard curing design strength σ 28 and the concrete rapid precast curing design strength σ t2 of the precast concrete member to be reached, and determining the maturity S 28 of the concrete at the end of the standard curing for 28 days of the concrete;

[0011] predetermine a mix proportion of the concrete, and prepare two groups of concrete test pieces according to the mix proportion;

[0012] adopt an actual fast-precast curing mode to cure one group of test pieces in the two groups of concrete test pieces, and measure to obtain a concrete fast-precast curing actual strength σ′ t2 ;

[0013] adopt a constant-temperature fast curing mode to cure another group of test pieces in the two groups of concrete test pieces, and measure to obtain a concrete standard curing actual strength σ′ 28 ;

[0014] determine whether the concrete fast-precast curing actual strength σ′ t2 is greater than a concrete fast-precast curing design strength σ t2 and the concrete standard curing actual strength σ′ 28 is greater than a concrete standard curing design strength σ 28 is established at the same time, if so, the requirement is met; otherwise, adjust the mix proportion of the concrete, and prepare two groups of concrete test pieces again according to the adjusted mix proportion to cure and measure, until the concrete fast-precast curing actual strength σ′ t2 is greater than the concrete fast-precast curing design strength σ t2 and the concrete standard curing actual strength σ′ 28 is greater than the concrete standard curing design strength σ 28 is established at the same time.

[0015] In the foregoing scheme, the concrete standard curing design strength σ 28 and the concrete fast-precast curing design strength σ t2 are determined according to a precast concrete member design index requirement; and the maturity degree S 28 of the concrete at the end of 28d standard curing is determined under a curing temperature of 20℃ and a relative humidity of greater than 95%.

[0016] In the foregoing scheme, the mix proportion of the concrete is determined according to a concrete mix proportion related design regulation.

[0017] In the foregoing scheme, the curing of one group of test pieces in the two groups of concrete test pieces by the actual fast-precast curing mode to measure the concrete fast-precast curing actual strength σ′ t2 includes: curing one group of test pieces in the two groups of concrete test pieces according to an actual fast-precast curing mode requirement in a precast concrete member production process, and measuring the strength of the test pieces by a standard test method after the curing to measure the strength as the concrete fast-precast curing actual strength σ′ t2 .

[0018] In the scheme, the actual fast precast curing mode is determined by a curing process of precast component production, and the curing parameters at least include static time length t1, static temperature T1, temperature rising rate v1, constant temperature time length t2, constant temperature T2, temperature falling rate v2 and total fast curing time length t3.

[0019] In the scheme, the other group of concrete test pieces in the two groups of concrete test pieces is cured by using the constant temperature fast curing mode, and the concrete standard curing actual strength σ' is determined. 28 , comprising: curing the other group of concrete test pieces in the two groups of concrete test pieces by using a constant temperature fast curing mode, the curing temperature of the constant temperature fast curing mode being higher than the curing temperature of the standard curing 28d mode, and the strength of the test piece is determined by using a standard test method after curing, and the determined strength is the concrete standard curing actual strength σ'. 28 .

[0020] In the scheme, in the constant temperature fast curing mode, the curing temperature is selected according to laboratory conditions, and the selection range of the curing temperature is 40-75℃; and the required curing age t q is inversely obtained according to the maturity S 28 of the concrete at the end of the standard curing 28d.

[0021] In the scheme, the maturity S 28 of the concrete is characterized by the equivalent age t e , and the calculation formula of the equivalent age is:

[0022]

[0023] In which:

[0024] U aT =(43830-43T)e (-0.00017T)t

[0025] In the formula, R is the gas constant, and is 8.314 J / mol·K; U ar is the activation energy of cement hydration reaction at the standard curing temperature; and U aT is the activation energy of the reaction at the temperature T, which is a function of time and temperature.

[0026] In the scheme, the mix proportion of the concrete is adjusted by at least one of the following groups: using cement with a high selection index, reducing the water-binder ratio, improving the particle size distribution of coarse and fine aggregates, adding high-efficiency active mineral admixtures or adding high-efficiency water reducing agents.

[0027] (Three) beneficial effects

[0028] As can be seen from the above technical solution, the method for rapidly optimizing the mix proportion of precast concrete components provided in this disclosure, compared with the traditional method for optimizing the mix proportion of precast concrete components, achieves higher efficiency due to the use of a constant-temperature rapid curing method for the concrete, resulting in a higher measured actual standard cured strength σ′ of the concrete. 28 This is equivalent to the strength of concrete under standard 28-day curing conditions, but the required time, i.e., the curing age (t), is different. q It is much shorter than the 28 days required under the standard 28-day curing method, which can significantly shorten the concrete mix design cycle, accelerate the production progress of precast components, solve the problem of long optimization cycle of traditional precast concrete component mix design, save time and costs, reduce the dependence of concrete mix design adjustment on engineering experience, and has good scientific guidance and promotion value. Attached Figure Description

[0029] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0030] Figure 1 This is a flowchart of a method for rapidly optimizing the mix proportions of precast concrete components, as disclosed in this publication.

[0031] Figure 2 This is a flowchart of a method for rapidly optimizing the mix proportions of precast concrete components according to embodiments of this disclosure.

[0032] Figure 3 This is a schematic diagram illustrating the curing of one of the two sets of concrete specimens using a practical rapid prefabrication curing method according to an embodiment of this disclosure.

[0033] Figure 4 This is a comparison diagram between the method for rapidly optimizing the mix proportion of precast concrete components using the embodiments of this disclosure and the traditional mix proportion optimization method. Detailed Implementation

[0034] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0035] This disclosure presents a method for rapidly optimizing the mix proportions of precast concrete components. For example... Figure 1 As shown, Figure 1is a flow chart of the method for quickly optimizing the mix proportion of prefabricated concrete components provided by the present disclosure. It should be noted that Figure 1 The application scenarios shown are only examples of application scenarios to which the embodiments of the present disclosure can be applied, to help those skilled in the art understand the technical content of the present disclosure, but are not meant to imply that the embodiments of the present disclosure cannot be used in other environments or scenarios.

[0036] As Figure 1 shown, the method for quickly optimizing the mix proportion of prefabricated concrete components provided by the present disclosure includes the following steps:

[0037] Step S1: Determine the concrete standard curing design strength σ 28 and the concrete quick prefabrication curing design strength σ t2 of the prefabricated concrete component that needs to be reached, and determine the maturity S 28 of the concrete at the end of 28d standard curing.

[0038] In this step, according to the design index requirements of the prefabricated concrete component, the concrete standard curing design strength σ 28 and the concrete quick prefabrication curing design strength σ t2 of the prefabricated concrete component that needs to be reached are determined. The maturity S 28 of the concrete at the end of 28d standard curing is determined under the conditions of a curing temperature of 20℃ and a relative humidity of greater than 95%.

[0039] Step S2: Predetermine the mix proportion of the concrete, and prepare two groups of concrete test pieces according to the mix proportion.

[0040] In this step, according to the relevant design regulations of the concrete mix proportion, the mix proportion of the concrete is first predetermined, and then two groups of concrete test pieces are prepared according to the mix proportion.

[0041] Step S3: Cure one group of test pieces in the two groups of test pieces using the actual quick prefabrication curing method, and measure to obtain the concrete quick prefabrication curing actual strength σ′ t2 .

[0042] In this step, one group of test pieces in the two groups of test pieces is cured according to the actual quick prefabrication curing method required in the production process of the prefabricated concrete component. After the curing is completed, the strength of the test piece is measured using a standard test method, and the measured strength is the concrete quick prefabrication curing actual strength σ′ t2 . The actual quick prefabrication curing method is determined by the curing process of the prefabricated component production, and at least includes the static stop time length t1, the static stop temperature T1, the temperature rise rate v1, the constant temperature time length t2, the constant temperature T2, the temperature drop rate v2, and the quick curing total time length t3, and other curing parameters.

[0043] Step S4: another group of the two groups of concrete test pieces is cured by using a constant temperature rapid curing method, and the actual strength σ' of the concrete standard curing is measured 28 ;

[0044] In this step, another group of the two groups of concrete test pieces is cured by using a constant temperature rapid curing method, the curing temperature of the constant temperature rapid curing method is higher than the curing temperature of the standard curing 28d method, and the strength of the test piece is measured by using a standard test method after curing, and the measured strength is the actual strength σ' of the concrete standard curing 28 . In the constant temperature rapid curing method, the curing temperature is selected according to the laboratory conditions, and the curing temperature is selected in the range of 40-75℃; the required curing age t q is obtained by back calculation according to the maturity S 28 of the concrete at the end of the standard curing 28d.

[0045] In this embodiment, the maturity S 28 of the concrete is characterized by the equivalent age t e , and the calculation formula of the equivalent age is:

[0046]

[0047] In formula 1:

[0048] U aT =(43830-43T)e (-0.00017T)t

[0049] Wherein: R is the gas constant, 8.314 J / mol·K; U ar is the activation energy of cement hydration reaction at the standard curing temperature; U aT is the activation energy of the reaction at the temperature T, which is a function of time and temperature.

[0050] It should be noted that the maturity of the concrete is characterized by the equivalent age t e of the concrete in the constant temperature rapid curing method at a certain temperature, and the curing age t q required for the development of the strength of the concrete is equivalent to the time required for the concrete to reach the same strength at the standard curing ambient temperature (20℃), that is, the maturity / equivalent age S 28 of the concrete at the end of the standard curing 28d method is t e =672h=28d, and the curing age t q of the corresponding constant temperature rapid curing method is t e=672h = 28d, obtained by reverse calculation. In this disclosure, the actual curing temperature range for the constant temperature rapid curing method is 40-75℃, which is 20℃ higher than the temperature used in the standard 28-day curing method. According to the principles of chemical reaction, the higher the temperature, the faster the concrete hydration rate, and the shorter the time to achieve the same effect (strength). That is, the curing age t using the constant temperature rapid curing method is... q It is much shorter than the standard 28-day maintenance period.

[0051] Step S5: Determine the actual strength σ′ of the rapidly precast and cured concrete. t2 Greater than the design strength σ of rapid precast concrete for curing t2 and the actual strength σ′ of concrete under standard curing 28 Greater than the standard curing design strength σ of concrete 28 If both conditions are met, the requirement is satisfied, and the process ends; otherwise, return to step S2 to adjust the concrete mix proportion, prepare two new sets of concrete specimens according to the adjusted mix proportion, and then execute steps S3 to S5 to cure and measure the two new sets of concrete specimens until the actual strength σ′ of the rapidly precast and cured concrete is reached. t2 Greater than the design strength σ of rapid precast concrete for curing t2 and the actual strength σ′ of concrete under standard curing 28 Greater than the standard curing design strength σ of concrete 28 Established at the same time.

[0052] In this step, the adjustment of the concrete mix proportion is achieved by using at least one of the following groups: selecting high-grade cement, reducing the water-cement ratio, improving the particle size distribution of coarse and fine aggregates, adding high-efficiency active mineral admixtures, or adding high-efficiency water-reducing agents.

[0053] Example 1

[0054] Please refer to Figure 2 As shown, Figure 2 This is a flowchart of a method for rapidly optimizing the mix proportions of precast concrete components according to embodiments of this disclosure, including the following steps:

[0055] ① Determine the required standard curing design strength σ of the precast concrete component based on the design specifications. 28 and the design strength σ of rapid precast concrete curing t2 .

[0056] ② Determine the degree of maturity (S) of the concrete at the end of the standard 28-day curing period (i.e., curing temperature 20℃, relative humidity greater than 95%). 28 .

[0057] ③ According to the relevant design regulations of the concrete mix proportion, the concrete mix proportion is predetermined, and then two groups of concrete test pieces are prepared according to the mix proportion.

[0058] ④ According to the actual rapid prefabrication maintenance mode in the prefabricated concrete component production process, one group of test pieces in the two groups of test pieces prepared in step ③ is maintained, and after the maintenance is completed, the strength of the test piece is measured by using the standard test method, and the measured strength is the actual strength σ' of the concrete rapid prefabrication maintenance. t2 The actual rapid prefabrication maintenance mode is determined by the maintenance process of the prefabricated component production, and includes the static stop time t1, the static stop temperature T1, the heating rate v1, the constant temperature time t2, the constant temperature T2, the cooling rate v2 and the total time t2 of the rapid maintenance.

[0059] ⑤ The other group of test pieces in the two groups of test pieces prepared in step ③ is maintained by using the constant temperature rapid maintenance mode, and after the maintenance is completed, the strength of the test piece is measured by using the standard test method, and the measured strength is the actual strength σ' of the concrete standard maintenance. 28 The determination mode of the constant temperature rapid maintenance mode includes: first, the temperature of the constant temperature rapid maintenance system is selected according to the laboratory conditions, and the selection range of the temperature of the constant temperature rapid maintenance system is 40-75℃; then, the maturity degree S of the concrete in step ② is used to back-calculate the required curing age t under the constant temperature rapid maintenance condition. 28 q .

[0060] ⑥ It is judged whether the actual strength σ' of the concrete rapid prefabrication maintenance is greater than the design strength σ of the concrete rapid prefabrication maintenance and the actual strength σ' of the concrete standard maintenance is greater than the design strength σ of the concrete standard maintenance. t2 If both are true, the requirement is met; otherwise, that is, the actual strength σ' of the concrete rapid prefabrication maintenance and the actual strength σ' of the concrete standard maintenance are not greater than the design strength σ of the concrete rapid prefabrication maintenance and the design strength σ of the concrete standard maintenance, respectively, the concrete mix proportion in step ③ is adjusted, and steps ③-⑥ are repeated until the requirement is met. t2 28 28 t2 28 t2 28

[0061] Further, in step ②, the maturity degree S of the concrete is characterized by the equivalent age t, and the calculation formula of the equivalent age is: 28 e

[0062]

[0063] ​​​​​​​​​​​

[0064] U aT = (43830 - 43T)e (-0.00017T)t

[0065] wherein: R is gas constant, 8.314 J / mol·K; U ar is the activation energy of cement hydration reaction at standard curing temperature; U aT is the activation energy of reaction at temperature T, which is a function of time and temperature.

[0066] Further, in step ⑥, the specific adjustment method of the concrete mix proportion includes one or any combination of the following ways: (1) selecting cement with high grade; (2) reducing the water-binder ratio; (3) improving the particle size distribution of coarse and fine aggregates; (4) adding high-efficiency active mineral admixtures; (5) adding high-efficiency water-reducing agents.

[0067] Example 2

[0068] Please refer to Figure 2 , Figure 2 is a method flowchart for quickly optimizing the mix proportion of prefabricated concrete members according to the embodiments of the present disclosure, including the following steps:

[0069] Step 1: A C50 concrete prefabricated box girder is produced for a certain project. According to the design index requirements of prefabricated concrete members, the concrete standard curing design strength σ 28 of the prefabricated concrete member needs to reach 50 MPa, and the concrete rapid prefabrication curing design strength σ t2 is 37.5 MPa.

[0070] Step 2: Determine the maturity / equivalent age S 28 of the concrete at the end of 28d standard curing (curing temperature 20℃, relative humidity greater than 95%). e = 672h = 28d.

[0071] Step 3: According to the “Mix Proportion Design Specification for Ordinary Concrete” (JGJ 55-2011), the concrete mix proportion is determined, and two groups of test pieces are prepared according to the “Standard Test Methods for Physical and Mechanical Properties of Concrete” GB / T 50081-2019. The concrete mix proportions are as follows:

[0072]

[0073] Step 4: According to the curing process of the prefabricated member production, the actual rapid prefabrication curing method is obtained, and the actual rapid prefabrication curing method is as follows: Figure 3, wherein the static time is 12h, the static temperature is 20℃, the temperature rising rate is 10℃ / h, the constant temperature is 50℃, the constant temperature duration is 24h, the temperature falling rate is 5℃ / h, and the total rapid curing duration is 45h. The first group of test pieces in step three are cured according to the curing mode as described above, and after the curing is completed, the strength of the test pieces is measured by using the standard test method, and it is measured that the strength is the actual strength of the rapid prefabricated concrete σ' t2 = 50.5MPa.

[0074] Step five: according to the laboratory conditions, the temperature of the constant temperature rapid curing mode is determined to be 70℃, according to the maturity / equivalent age S 28 = t e = 672h = 28d of the concrete as described in step two, and the curing age t q = 45h required under the constant temperature rapid curing condition is calculated by using formula (1) in reverse. The second group of test pieces as described in step three are cured according to the constant temperature rapid curing mode as described above, and after the curing is completed, the strength of the test pieces is measured by using the standard test method, and it is measured that the strength is the actual strength of the standard curing concrete σ' 28 = 63.4MPa.

[0075] Step six: if the actual strength of the rapid prefabricated concrete σ' t2 is greater than the design strength of the rapid prefabricated concrete σ t2 and the actual strength of the standard curing concrete σ' 28 is greater than the design strength of the standard curing concrete σ 28 are both established, it is indicated that the mixing proportion of step three meets the design requirements of the prefabricated member, and the mixing proportion determined in step three is the final mixing proportion, and Figure 4 It can be seen that by using the method for rapidly optimizing the mixing proportion of the prefabricated concrete member provided in the embodiment of the disclosure, the optimization cycle of the mixing proportion of the prefabricated concrete member in the embodiment is only 45 hours, which is greatly reduced compared with 672h (i.e. 28 days) required by the traditional mixing proportion optimization method, and the goal of shortening the construction period of the prefabricated member is further achieved.

[0076] Embodiment 3

[0077] Please refer to Figure 2 , and Figure 2 is a flow chart of the method for rapidly optimizing the mixing proportion of the prefabricated concrete member according to the embodiment of the disclosure, which is basically the same as the method of embodiment 2, and the difference is that in step six, the actual strength of the rapid prefabricated concrete σ' t2 is greater than the design strength of the rapid prefabricated concrete σ t2 and the actual strength of the standard curing concrete σ' 28 is greater than the design strength of the standard curing concrete σ 28If they are not simultaneously true, it means that the concrete mix proportion in step three does not meet the design requirements of the precast components and the concrete mix proportion needs to be adjusted. Specifically, when adjusting the concrete mix proportion, one or any combination of the following methods can be used: (1) Select cement with a high grade; (2) Reduce the water-cement ratio; (3) Improve the particle size distribution of coarse and fine aggregates; (4) Add high-efficiency active mineral additives; (5) Add high-efficiency water-reducing agents.

[0078] This embodiment specifically includes the following steps:

[0079] Step 1: A certain project involves the production and fabrication of C50 precast concrete box girders. Based on the design specifications for precast concrete components, the required standard curing design strength σ of the precast concrete components must be achieved. 28 The required design strength σ for rapid precast curing of concrete is 50 MPa. t2 It is 37.5 MPa.

[0080] Step 2: Determine the maturity / equivalent age S of the concrete at the end of the standard 28-day curing method (curing temperature 20℃, relative humidity greater than 95%). 28 =t e =672h=28d.

[0081] Step 3: Determine the concrete mix proportion according to the "Specification for Mix Proportion Design of Ordinary Concrete" (JGJ 55-2011), and prepare two sets of specimens according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" GB / T 50081-2019. The concrete mix proportion is shown in the table below:

[0082]

[0083] Step 4: Based on the curing process of precast component production, obtain the actual rapid precast curing method, as follows: Figure 3 The curing process included a static curing time of 12 hours, a static curing temperature of 20°C, a heating rate of 10°C / hour, a constant temperature of 50°C for 24 hours, a cooling rate of 5°C / hour, and a total rapid curing time of 45 hours. The first group of specimens in step three were cured according to the above curing requirements. After curing, the specimen strength was determined using standard testing methods, and the measured strength was the actual strength σ′ of the rapidly precast concrete. t2 =38.8MPa.

[0084] Step 5: Based on laboratory conditions, determine the temperature for the constant temperature rapid curing method to be 70℃. According to the concrete maturity / equivalent age S mentioned in Step 2... 28 =t e= 672h, and the curing age t required under the constant temperature and rapid curing condition is calculated reversely by using formula (1) q = 45h. The second group of test pieces described in step three are cured in the above constant temperature and rapid curing mode, and the strength of the test pieces is measured after curing according to the standard test method, and the measured strength is the actual strength of the concrete under standard curing σ' 28 = 48.3MPa.

[0085] Step six: the actual strength of the concrete under rapid prefabrication curing σ' t2 is greater than the design strength of the concrete under rapid prefabrication curing σ t2 , the actual strength of the concrete under standard curing σ' 28 is less than the design strength of the concrete under standard curing σ 28 , which indicates that the mixture ratio in step three needs to be adjusted and optimized.

[0086] Step three is repeated, the water-binder ratio is reduced by appropriately reducing the unit water consumption of the concrete, the first concrete mixture ratio is adjusted and optimized, and the adjusted concrete mixture ratio is as follows:

[0087]

[0088] Step four is repeated, and the measured strength is the actual strength of the concrete under rapid prefabrication curing σ' t2 = 43.5MPa.

[0089] Step five is repeated, and the measured strength is the actual strength of the concrete under standard curing σ' 28 = 58MPa.

[0090] Step six is repeated, the actual strength of the concrete under rapid prefabrication curing σ' t2 is greater than the design strength of the concrete under rapid prefabrication curing σ t2 , and the actual strength of the concrete under standard curing σ' 28 is greater than the design strength of the concrete under standard curing σ 28 , which indicates that the adjusted mixture ratio meets the design requirements of the prefabricated component, and the mixture ratio adjusted for the second time is taken as the final mixture ratio.

[0091] It should be noted that in the embodiment 2 and the embodiment 3 of the present disclosure, the curing temperature of the constant temperature and rapid curing mode is 70℃, and the curing age t q = 45h is calculated as follows:

[0092] The curing age t q includes the time from pouring to stripping and the curing time under the environment of 70℃, and the time from pouring to stripping of the concrete in the embodiment 2 and the embodiment 3 is 24h, and the temperature is 20℃.

[0093] The curing age t of the constant temperature rapid curing method q The formula (1) and (2) provided by the present disclosure can be inversely deduced, specifically as follows:

[0094]

[0095] Wherein:

[0096] U aT =(43830-43T)e (-0.00017T)t (Formula 2)

[0097] In the formula, R is the gas constant, taking 8.314 J / mol·K; U ar is the activation energy of cement hydration reaction at the standard curing temperature; U aT is the activation energy of the reaction when the temperature is T, which is a function of time and temperature.

[0098] In order to more intuitively show the calculation process, this time the calculation is in the form of manual calculation.

[0099] Step 1: Convert formula (1) to:

[0100]

[0101] Step 2: Calculate the equivalent age t of the concrete from pouring to form removal e1 , the time t from pouring to form removal q1 =24h=1d, the temperature T1=20℃, take Δt=24h,

[0102]

[0103] Step 3: Calculate the equivalent age t of the concrete cured at 70℃ environment e2 , take Δt=1h, the curing age t q2 =t q1 +Δt=24h+1h=25h=1.04d, the temperature T2=70℃,

[0104]

[0105] Step 4: Determine whether t e2 is infinitely close to S 28 =t e =672h=28d, if yes, t q2 is the curing age corresponding to the constant temperature rapid curing method, if not, repeat step 3 to calculate the curing age t q3 =t q2 +Δt=25h+1h=26h=1.08d, the equivalent age t e3 corresponding to, until t enUnlimited approach S 28 = t e = 672h = 28d, corresponding t qn is the curing age of the constant temperature rapid curing method, t q22 = 45h is the curing age of the constant temperature rapid curing method corresponding to the examples 2 and 3, and the final curing age calculation result of the constant temperature rapid curing method is shown in table 1. It should be noted that the above calculation process can also be quickly calculated by calculation software.

[0106]

[0107]

[0108] Table 1: Constant temperature rapid curing method curing age calculation result

[0109] The above specific examples further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for rapidly optimizing the mix proportions of precast concrete components, characterized in that, The method includes: Determine the required standard curing design strength σ of precast concrete components. 28 and the design strength σ of rapid precast concrete curing t2 And determine the maturity level S of the concrete at the end of 28 days of standard curing. 28 ; The mix proportion of the concrete is predetermined, and two sets of concrete specimens are prepared according to the mix proportion; One set of concrete specimens from the two groups was cured using a practical rapid precast curing method, and the actual strength σ´ of the rapidly precast cured concrete was measured. t2 ; Another set of concrete specimens from the two sets of specimens was cured using a constant temperature rapid curing method, and the actual standard curing strength σ´ of the concrete was determined. 28 ; Determining the actual strength σ´ of rapidly precast and cured concrete t2 Greater than the design strength σ of rapid precast concrete for curing t2 and the actual strength σ´ of concrete under standard curing 28 Greater than the standard curing design strength σ of concrete 28 If both conditions are met, the requirement is satisfied; otherwise, adjust the concrete mix proportion, prepare two new sets of concrete specimens according to the adjusted mix proportion, and perform curing and testing until the actual strength σ´ of the rapidly precast and cured concrete is reached. t2 Greater than the design strength σ of rapid precast concrete for curing t2 and the actual strength σ´ of concrete under standard curing 28 Greater than the standard curing design strength σ of concrete 28 Established simultaneously; Among them, the constant temperature rapid curing method was used to cure another set of concrete specimens from the two sets, and the actual standard curing strength σ´ of the concrete was measured. 28 This includes: curing another set of concrete specimens from the two sets using a constant-temperature rapid curing method. The curing temperature used in this method is higher than that used in the standard 28-day curing method. After curing, the specimen strength is determined using standard test methods, and the measured strength is the actual standard-cured concrete strength σ´. 28 In the aforementioned constant-temperature rapid curing method, the curing temperature is selected based on laboratory conditions, with a range of 40-75℃; the required curing period is t. q It is based on the maturity S of the concrete at the end of 28 days of standard curing. 28 It was obtained by reverse reasoning.

2. The method for rapidly optimizing the mix proportions of precast concrete components according to claim 1, characterized in that, The required standard curing design strength σ of precast concrete components is determined. 28 and the design strength σ of rapid precast concrete curing t2 It is determined based on the design specifications of precast concrete components; The maturity S of the concrete at the end of 28 days of standard curing was determined. 28 The determination was made under the conditions of a curing temperature of 20℃ and a relative humidity greater than 95%.

3. The method for rapidly optimizing the mix proportions of precast concrete components according to claim 1, characterized in that, The predetermined concrete mix proportion is determined according to the relevant design specifications for concrete mix proportions.

4. The method for rapidly optimizing the mix proportions of precast concrete components according to claim 1, characterized in that, One set of concrete specimens from the two groups was cured using a practical rapid precast curing method, and the actual strength σ´ of the rapidly precast cured concrete was measured. t2 ,include: In accordance with the requirements of the actual rapid precasting and curing method in the production of precast concrete components, one set of the two groups of concrete specimens was cured. After curing, the specimen strength was determined using standard test methods, and the measured strength was σ´, the actual strength of the rapidly precast and cured concrete. t2 .

5. The method for rapidly optimizing the mix proportions of precast concrete components according to claim 4, characterized in that, The actual rapid prefabrication curing method is determined by the curing process of the prefabricated component production. The curing parameters include at least the static curing time t1, static curing temperature T1, heating rate v1, constant temperature time t2, constant temperature T2, cooling rate v2, and total rapid curing time t3.

6. The method for rapidly optimizing the mix proportions of precast concrete components according to claim 1, characterized in that, The adjustment of the concrete mix proportion adopts at least one of the following groups: selecting high-grade cement, reducing the water-cement ratio, improving the particle size distribution of coarse and fine aggregates, adding high-efficiency active mineral admixtures, or adding high-efficiency water-reducing agents.

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