CN116079879A - Method for rapidly optimizing mixing ratio of precast concrete components - Google Patents
Method for rapidly optimizing mixing ratio of precast concrete components Download PDFInfo
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Abstract
The present disclosure relates to the technical field of precast concrete, and provides a method for rapidly optimizing a mixing ratio of precast concrete members, comprising: determining the standard curing design strength of concrete and the rapid precast curing design strength of concrete which are required to be achieved by precast concrete members; the mixing proportion of concrete is pre-determined, and two groups of concrete test pieces are prepared according to the mixing proportion; and curing the concrete test piece by adopting an actual rapid prefabrication curing method and a constant-temperature rapid curing mode, measuring the strength of the concrete test piece by adopting a standard test method after curing, and comparing the measured strength with the strength required by design until the strength meets the requirement. By utilizing the method and the device, the trial-mix period of concrete can be greatly shortened, the production progress of the prefabricated component is quickened, the problem that the traditional prefabricated concrete component is long in mix proportion optimization period is solved, the dependence of concrete mix proportion adjustment on engineering experience is reduced, and better scientific guidance and popularization value are achieved.
Description
Technical Field
The disclosure relates to the technical field of precast concrete, in particular to a method for rapidly optimizing a mixing ratio of precast concrete components.
Background
The precast concrete technology is one of important technologies for realizing the green low-carbon concept and realizing bridge industrialization, and the rapid curing technology such as steam curing and the like is a core means of the precast concrete technology. The rapid maintenance is beneficial to improving the turnover rate of the die, improving the utilization rate and labor productivity of main process equipment, shortening the production period and reducing the product cost.
In the process of designing and adjusting the mix proportion of the factory precast concrete components, the standard curing mode 28d is adopted to obtain the compressive strength of the concrete, and the key quality parameters and the acceptance criteria for evaluating the qualification of the concrete components are still adopted. However, the standard curing 28d method is adopted to obtain the compressive strength of the concrete, which takes 28 days, and because of the long curing period, the concrete mixing ratio cannot be designed and adjusted in time, and the quality condition in the production and preparation of the prefabricated part cannot be predicted in time.
In addition, the current research method for optimizing the concrete mixing ratio is mainly concentrated on the traditional orthogonal design test method, the method has more limiting conditions, the experimental searching range is limited, the research is long in time consumption and high in cost, and an ideal mixing ratio optimizing result close to the actual mixing ratio cannot be obtained.
Therefore, there is a need to develop a scientific and rapid method for optimizing the mix ratio of precast concrete elements.
Disclosure of Invention
First, the technical problem to be solved
In view of the above, a main object of the present disclosure is to provide a method for quickly optimizing a mix ratio of a precast concrete member, so as to solve the problem of long optimization period of the mix ratio of the conventional precast concrete member, and reduce the dependency of the adjustment of the mix ratio of the concrete on engineering experience.
(II) technical scheme
To achieve the above object, the present disclosure provides a method of rapidly optimizing a mix ratio of precast concrete members, the method comprising:
determining the standard curing design strength sigma of concrete to be achieved by a precast concrete member 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 And determining the maturity S of the concrete at the end of 28d of standard curing of the concrete 28 ；
The mixing proportion of concrete is pre-determined, and two groups of concrete test pieces are prepared according to the mixing proportion;
curing one group of concrete test pieces in the two groups of concrete test pieces by adopting an actual rapid precast curing mode, and determining to obtain the actual strength sigma 'of the rapid precast concrete curing' t2 ；
Curing the other group of concrete test pieces in the two groups of concrete test pieces by adopting a constant-temperature rapid curing mode, and determining to obtain the concrete standard curing actual strength sigma' 28 ；
Judging actual strength sigma 'of concrete rapid prefabrication maintenance' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 Whether the two are simultaneously established, if so, the requirements are met; otherwise, adjusting the mixing ratio of the concrete, and preparing two groups of concrete test pieces again according to the adjusted mixing ratio for curing and measuring until the actual strength sigma 'of the rapid precast curing of the concrete' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 And so on.
In the above scheme, the concrete is determinedStandard concrete curing design strength sigma that the component needs to reach 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 Is determined according to the design index requirement of the precast concrete member; determining the maturity S of the concrete at the end of 28 days of standard curing of the concrete 28 Is determined at a curing temperature of 20 ℃ and a relative humidity of greater than 95%.
In the above scheme, the predetermined concrete mixing ratio is determined according to the concrete mixing ratio related design rules.
In the scheme, the actual rapid precast curing mode is adopted to cure one group of the two groups of concrete test pieces, and the actual strength sigma 'of the rapid precast curing of the concrete is obtained by measurement' t2 Comprising: curing one group of concrete test pieces in the two groups of concrete test pieces according to the actual rapid precast curing mode requirement in the precast concrete member production process, and measuring the strength of the test pieces by adopting a standard test method after curing, wherein the measured strength is the actual strength sigma 'of the rapid precast concrete curing' t2 。
In the above scheme, the actual rapid prefabricated curing mode is determined by a curing process for producing and preparing prefabricated components, and the curing parameters at least comprise a static time duration t 1 Rest temperature T 1 Rate of temperature rise v 1 Constant temperature duration t 2 Constant temperature T 2 Cooling rate v 2 And a total time t of rapid maintenance 3 。
In the scheme, the other group of the two groups of concrete test pieces is cured by adopting a constant-temperature rapid curing mode, and the standard curing actual strength sigma 'of the concrete is obtained by measuring' 28 Comprising: curing the other group of concrete test pieces in the two groups of concrete test pieces by adopting a constant-temperature rapid curing mode, wherein the curing temperature adopted by the constant-temperature rapid curing mode is higher than the curing temperature adopted by a standard curing mode of 28d, and the strength of the test pieces is measured by adopting a standard test method after curing is finished, so that the measured strength is the standard curing actual strength sigma 'of the concrete' 28 。
In the scheme, in the constant temperature rapid maintenance mode, the method comprises the following steps ofThe curing temperature is selected according to laboratory conditions, and the range of the curing temperature is 40-75 ℃; the required curing age t q According to the maturity S of the concrete at the end of 28d adopting standard curing 28 And (5) reversely pushing to obtain the product.
In the above scheme, the maturity S of the concrete 28 By equivalent age t e Characterization, the equivalent age calculation formula is as follows:
wherein:
U aT ＝(43830-43T)e (-0.00017T)t
wherein: r is a gas constant, 8.314J/mol.K; u (U) ar The cement hydration reaction activation energy at the standard curing temperature; u (U) aT The reaction activation energy at a temperature T is a function of time and temperature.
In the above scheme, the mixing ratio of the concrete is adjusted by at least one of selecting cement with high grade, reducing the water-cement ratio, improving the grain size distribution of coarse and fine aggregates, and doping high-efficiency active mineral reference materials or high-efficiency water reducer.
(III) beneficial effects
As can be seen from the technical scheme, compared with the traditional optimization design method for the mixing proportion of the precast concrete components, the method for rapidly optimizing the mixing proportion of the precast concrete components provided by the present disclosure has the advantages that the constant temperature rapid curing mode is adopted to cure the concrete, and then the standard curing actual strength sigma 'of the concrete is measured' 28 Equivalent to the strength of concrete in a standard curing mode of 28 days, but the required time is the curing age t q The method is far smaller than 28 days required by a standard curing 28d mode, so that the trial-mix period of concrete can be greatly shortened, the production progress of precast components is quickened, the problem of long optimization period of the traditional precast concrete component proportion is solved, the time and the cost are saved, the dependence of concrete proportion adjustment on engineering experience is reduced, and better scientific guidance is providedSex and popularization value.
Drawings
The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments thereof with reference to the accompanying drawings in which:
fig. 1 is a flow chart of a method for rapidly optimizing the mix ratio of precast concrete elements provided by the present disclosure.
Fig. 2 is a flowchart of a method of rapidly optimizing precast concrete element mix ratios in accordance with an embodiment of the present disclosure.
Fig. 3 is a schematic illustration of curing one of the two sets of concrete test pieces using an actual rapid precast curing mode in accordance with an embodiment of the present disclosure.
Fig. 4 is a diagram comparing a method of rapidly optimizing a mix ratio of precast concrete units using an embodiment of the present disclosure with a conventional mix ratio optimizing method.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is only exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the concepts of the present disclosure.
The embodiment of the disclosure provides a method for quickly optimizing the mixing ratio of precast concrete components. As shown in fig. 1, fig. 1 is a flowchart of a method for rapidly optimizing the mix ratio of precast concrete elements provided by the present disclosure. It should be noted that fig. 1 is only an example of an application scenario in which the embodiments of the present disclosure may be applied to help those skilled in the art understand the technical content of the present disclosure, but it does not mean that the embodiments of the present disclosure may not be used in other environments or scenarios.
As shown in fig. 1, the method for rapidly optimizing the mixing ratio of precast concrete members provided by the present disclosure includes the following steps:
step S1: determining the standard curing design strength sigma of concrete to be achieved by a precast concrete member 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 And determining the maturity S of the concrete at the end of 28d of standard curing of the concrete 28 ；
In the step, according to the design index requirement of the precast concrete member, determining the standard curing design strength sigma of the concrete which needs to be achieved by the precast concrete member 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 . Determining the maturity S of the concrete at the end of the standard curing 28d 28 Is determined at a curing temperature of 20 ℃ and a relative humidity of greater than 95%.
Step S2: the mixing proportion of concrete is pre-determined, and two groups of concrete test pieces are prepared according to the mixing proportion;
in this step, according to the concrete mix related design protocol, the mix of the concrete is first predetermined, and then two sets of concrete test pieces are prepared according to the mix.
Step S3: curing one group of concrete test pieces in the two groups of concrete test pieces by adopting an actual rapid precast curing mode, and determining to obtain the actual strength sigma 'of the rapid precast concrete curing' t2 ；
In the step, according to the requirement of an actual rapid precast curing mode in the precast concrete member production process, curing one group of concrete test pieces in the two groups of concrete test pieces, and measuring the strength of the test pieces by adopting a standard test method after curing, wherein the measured strength is the actual strength sigma 'of the rapid precast concrete curing' t2 . Wherein the actual rapid prefabricated maintenance mode is determined by a maintenance process for producing and preparing prefabricated parts and at least comprises a static stop time duration t 1 Rest temperature T 1 Rate of temperature rise v 1 Constant temperature duration t 2 Constant temperature T 2 Cooling rate v 2 And a total time t of rapid maintenance 3 And (5) maintaining parameters.
Step S4: curing the other group of concrete test pieces in the two groups of concrete test pieces by adopting a constant-temperature rapid curing mode, and measuring to obtain a mixtureConcrete standard curing actual strength sigma' 28 ；
In the step, the other group of the two groups of concrete test pieces is cured by adopting a constant-temperature rapid curing mode, the curing temperature adopted by the constant-temperature rapid curing mode is higher than the curing temperature adopted by a standard curing mode of 28d, the strength of the test piece is measured by adopting a standard test method after curing, and the measured strength is the standard curing actual strength sigma 'of the concrete' 28 . In the constant temperature rapid curing mode, the adopted curing temperature is selected according to laboratory conditions, and the selection range of the curing temperature is 40-75 ℃; the required curing age t q According to the maturity S of the concrete at the end of 28d adopting standard curing 28 And (5) reversely pushing to obtain the product.
In this embodiment, the concrete maturity S 28 By equivalent age t e Characterization, the equivalent age calculation formula is as follows:
in equation 1:
U aT ＝(43830-43T)e (-0.00017T)t
wherein: r is a gas constant, 8.314J/mol.K; u (U) ar The cement hydration reaction activation energy at the standard curing temperature; u (U) aT The reaction activation energy at a temperature T is a function of time and temperature.
It should be noted that the present disclosure employs an equivalent age t e Characterizing the maturity of concrete, the equivalent age is the curing age t required by the strength development of concrete in a constant temperature rapid curing mode at a certain temperature q Equivalent to the time required for the concrete to reach the same strength at the standard curing environment temperature (20 ℃), namely the maturity/equivalent age S of the concrete when the standard curing mode of 28d is adopted in the present disclosure 28 ＝t e The curing age t of the corresponding constant-temperature rapid curing mode is 672 h=28d q Then the equivalent age t can be utilized e The result is reverse-pushed with 672 h=28d. Constant temperature rapid feeding in the present disclosureThe actual curing temperature of the curing mode is selected to be 40-75 ℃ which is higher than the temperature of 20 ℃ adopted by the standard curing mode of 28d, and according to the chemical reaction principle, the higher the temperature is, the faster the hydration rate of the concrete is, and the shorter the time for reaching the same effect (strength) is, namely the curing age t adopting the constant-temperature rapid curing mode q Is much smaller than 28 days of the standard 28d mode of maintenance.
Step S5: judging actual strength sigma 'of concrete rapid prefabrication maintenance' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 Whether the two are simultaneously established or not, if the two are simultaneously established, the requirement is met, and the process is ended; otherwise, returning to the step S2 to adjust the mixing ratio of the concrete, preparing two groups of concrete test pieces again according to the adjusted mixing ratio, and then executing the steps S3 to S5 to perform curing and determination on the two groups of concrete test pieces prepared again until the concrete is rapidly prefabricated and cured to the actual strength sigma' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 And so on.
In the step, the mixing ratio of the concrete is adjusted by at least one of selecting cement with high grade, reducing the water-cement ratio, improving the grain size distribution of coarse and fine aggregates, and doping high-efficiency active mineral reference materials or high-efficiency water reducing agents.
Example 1
Referring to fig. 2, fig. 2 is a flowchart of a method for rapidly optimizing a precast concrete member mix ratio according to an embodiment of the present disclosure, including the steps of:
(1) determining the standard curing design strength sigma of the concrete to be achieved by the precast concrete member according to the design index requirement of the precast concrete member 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 。
(2) Determining the maturity S of the concrete at the end of 28d standard curing (curing temperature 20 ℃ C., relative humidity greater than 95%) 28 。
(3) According to the concrete mixing proportion related design rules, the concrete mixing proportion is pre-determined, and then two groups of concrete test pieces are prepared according to the mixing proportion.
(4) Curing one group of the two groups of concrete test pieces prepared in the step (3) according to an actual rapid precast curing mode in the precast concrete member production process, and measuring the strength of the test pieces by adopting a standard test method after curing, wherein the measured strength is the actual strength sigma 'of the rapid precast concrete curing' t2 . The actual rapid prefabricated maintenance mode is determined by a maintenance process for producing and preparing prefabricated parts and comprises a static stop time duration t 1 Rest temperature T 1 Rate of temperature rise v 1 Constant temperature duration t 2 Constant temperature T 2 Cooling rate v 2 And a total time t of rapid maintenance 2 And (5) maintaining parameters.
(5) Curing the other group of the two groups of concrete test pieces prepared in the step (3) by adopting a constant-temperature rapid curing mode, and measuring the strength of the test pieces by adopting a standard test method after curing is finished, wherein the measured strength is the actual strength sigma 'of concrete standard curing' 28 . The method for determining the constant temperature rapid maintenance mode comprises the following steps: firstly, selecting the temperature of a constant-temperature rapid curing system according to laboratory conditions, wherein the temperature of the constant-temperature rapid curing system is selected within the range of 40-75 ℃; then according to the maturity S of the concrete in the step (2) 28 The reverse pushing is carried out to obtain the required curing age t under the constant temperature rapid curing condition q 。
(6) Judging actual strength sigma 'of concrete rapid prefabrication maintenance' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 Whether the two are simultaneously established, if so, the requirements are met; otherwise, the concrete is quickly prefabricated and maintained to have actual strength sigma' t2 And concrete standard curing actual strength sigma' 28 Is not simultaneously larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And the standard curing design strength sigma of the concrete 28 Mixing the concrete in the step (3)And (3) row adjustment, and repeating the steps (3) - (6) until the requirements are met.
Further, in step (2), the maturity S of the concrete 28 By equivalent age t e Characterization, the equivalent age calculation formula is as follows:
wherein:
U aT ＝(43830-43T)e (-0.00017T)t
wherein: r is a gas constant, 8.314J/mol.K; u (U) ar The cement hydration reaction activation energy at the standard curing temperature; u (U) aT The reaction activation energy at a temperature T is a function of time and temperature.
Further, in the step (6), the concrete mixing proportion concrete debugging method comprises one or any combination of the following modes: (1) selecting cement with high label; (2) reducing the water-gel ratio; (3) improving the grain size distribution of the coarse and fine aggregates; (4) incorporating a highly effective active mineral reference material; (5) mixing into the high-efficiency water reducer.
Example 2
Referring to fig. 2, fig. 2 is a flowchart of a method for rapidly optimizing a precast concrete member mix ratio according to an embodiment of the present disclosure, including the steps of:
step one: c50 concrete precast box girder produced by certain engineering production, and according to the design index requirement of precast concrete components, the standard curing design strength sigma of the concrete which needs to be achieved by the precast concrete components 28 50MPa, and the strength sigma of the concrete rapid prefabrication maintenance design t2 37.5MPa.
Step two: determining the maturity/equivalent age S of the concrete at the end of the standard curing 28d mode (curing temperature 20 ℃ C., relative humidity greater than 95%) 28 ＝t e ＝672h＝28d。
Step three: according to the general concrete mix design procedure (JGJ 55-2011), determining the concrete mix, and preparing two groups of test pieces according to the concrete physical and mechanical property test method standard GB/T50081-2019, wherein the concrete mix is as follows:
step four: according to the curing process of the prefabricated part production preparation, the actual rapid prefabricated curing mode is obtained, wherein the actual rapid prefabricated curing mode is shown as figure 3, the static stop time is 12 hours, the static stop temperature is 20 ℃ and the heating rate is 10 ℃/h, the constant temperature is 50 ℃, the constant temperature duration is 24 hours, the cooling rate is 5 ℃/h, and the total rapid curing duration is 45 hours. Curing the first group of test pieces in the third step according to the curing mode requirement, and measuring the strength of the test pieces by adopting a standard test method after curing is finished, wherein the measured strength is the actual strength sigma 'of concrete rapid precast curing' t2 ＝50.5MPa。
Step five: determining the temperature of a constant-temperature rapid curing mode to be 70 ℃ according to laboratory conditions, and determining the maturity/equivalent age S of the concrete according to the second step 28 ＝t e =672 h=28 d, and the required curing age t under the constant temperature rapid curing condition is obtained by adopting the formula (1) to calculate in a reverse way q =45h. Curing the second group of test pieces in the third step according to the constant-temperature rapid curing mode, and measuring the strength of the test pieces by adopting a standard test method after curing, wherein the measured strength is the concrete standard curing actual strength sigma' 28 ＝63.4MPa。
Step six: if concrete is prefabricated and cured rapidly, the actual strength sigma 'is achieved' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 If the two are simultaneously established, it is stated that the mix ratio of the third step meets the design requirement of the prefabricated component, and the mix ratio determined in the third step is taken as the final mix ratio, as can be seen from fig. 4, by the method for quickly optimizing the mix ratio of the prefabricated concrete component provided by the embodiment of the present disclosure, the optimization period of the mix ratio of the prefabricated concrete component in the embodiment is only 45 hours, and 672h, namely 2h is needed compared with the traditional mix ratio optimization methodCompared with 8 days, the method greatly reduces the design adjustment period of the mixing ratio, and further achieves the aim of shortening the construction period of the prefabricated component.
Example 3
Referring to fig. 2, fig. 2 is a flowchart of a method for rapidly optimizing the mix ratio of precast concrete units according to an embodiment of the present disclosure, which is basically the same as the method of embodiment 2, except that: in the sixth step, concrete is rapidly prefabricated and maintained to have actual strength sigma' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 If the concrete mixing ratios in the third step do not meet the design requirements of the prefabricated components, the concrete mixing ratios need to be adjusted, and particularly when the concrete mixing ratios are adjusted, the concrete mixing ratios are used in combination in one or more of the following modes: (1) selecting cement with high label; (2) reducing the water-gel ratio; (3) improving the grain size distribution of the coarse and fine aggregates; (4) incorporating a highly effective active mineral reference material; (5) mixing into the high-efficiency water reducer.
For this embodiment, the method specifically includes the following steps:
step one: c50 concrete precast box girder produced by certain engineering production, and according to the design index requirement of precast concrete components, the standard curing design strength sigma of the concrete which needs to be achieved by the precast concrete components 28 The design strength sigma of the concrete rapid prefabrication maintenance needed to be achieved when the rapid prefabrication maintenance is finished is 50MPa t2 37.5MPa.
Step two: determining the maturity/equivalent age S of the concrete at the end of the standard curing 28d mode (curing temperature 20 ℃ C., relative humidity greater than 95%) 28 ＝t e ＝672h＝28d。
Step three: according to the general concrete mix design procedure (JGJ 55-2011), determining the concrete mix, and preparing two groups of test pieces according to the concrete physical and mechanical property test method standard GB/T50081-2019, wherein the concrete mix is as follows:
step four: according to the curing process of the prefabricated part production preparation, the actual rapid prefabricated curing mode is obtained, wherein the actual rapid prefabricated curing mode is shown as figure 3, the static stop time is 12 hours, the static stop temperature is 20 ℃ and the heating rate is 10 ℃/h, the constant temperature is 50 ℃, the constant temperature duration is 24 hours, the cooling rate is 5 ℃/h, and the total rapid curing duration is 45 hours. Curing the first group of test pieces in the third step according to the curing mode requirement, and measuring the strength of the test pieces by adopting a standard test method after curing is finished, wherein the measured strength is the actual strength sigma 'of concrete rapid precast curing' t2 ＝38.8MPa。
Step five: determining the temperature of a constant-temperature rapid curing mode to be 70 ℃ according to laboratory conditions, and determining the maturity/equivalent age S of the concrete according to the second step 28 ＝t e =672 h, and the required curing age t under the constant temperature rapid curing condition is obtained by the reverse push calculation of the formula (1) q =45h. Curing the second group of test pieces in the third step according to the constant-temperature rapid curing mode, and measuring the strength of the test pieces by adopting a standard test method after curing, wherein the measured strength is the concrete standard curing actual strength sigma' 28 ＝48.3MPa。
Step six: concrete rapid prefabrication maintenance actual strength sigma' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 Concrete standard curing actual strength sigma' 28 Is smaller than the standard curing design strength sigma of concrete 28 The adjustment and optimization of the mixing ratio in the third step are required.
Repeating the third step, reducing the water-gel ratio by properly reducing the water consumption of the concrete unit, and optimally adjusting the first concrete mixing ratio, wherein the adjusted concrete mixing ratio is shown in the following table:
repeating the fourth step to obtain the concrete rapid prefabrication maintenance actual strengthσ′ t2 ＝43.5MPa。
Repeating the fifth step, wherein the measured strength is the actual strength sigma 'of the standard curing of the concrete' 28 ＝58MPa。
Repeating the step six, and rapidly prefabricating and curing the concrete to obtain the actual strength sigma' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 Meanwhile, the situation that the adjusted mixing ratio meets the design requirement of the prefabricated component is described, and the mixing ratio after the second adjustment is used as the final mixing ratio.
In example 2 and example 3 of the present disclosure, the curing temperature used in the constant temperature rapid curing method was 70 ℃, and the curing age t was q The calculation process for=45h is specifically as follows:
the curing age t q The time from pouring to form removal and curing time in the environment of 70 ℃ are included, the time from pouring to form removal of the concrete in example 2 and example 3 is 24 hours, and the temperature is 20 ℃.
Curing age t of constant-temperature rapid curing mode q Can be obtained by reverse-pushing the formulas (1) and (2) provided by the disclosure, and is specifically as follows:
wherein:
U aT ＝(43830-43T)e (-0.00017T)t (equation 2)
Wherein: r is a gas constant, 8.314J/mol.K; u (U) ar The cement hydration reaction activation energy at the standard curing temperature; u (U) aT The reaction activation energy at a temperature T is a function of time and temperature.
To more intuitively demonstrate the calculation process, this calculation is performed manually.
Step 1: converting equation (1) into:
step 2: calculating the equivalent age t corresponding to the concrete from pouring to form removal e1 Time t from pouring to demolding q1 =24h=1d, temperature T 1 Taking Δt=24 h at 20 ℃,
step 3: calculating equivalent age t corresponding to curing of concrete at 70 DEG C e2 Taking Δt=1h, and curing the age t q2 ＝t q1 +Δt=24h+1h=25h=1.04 d, temperature T 2 ＝70℃，
Step 4: judgment of t e2 Whether or not to infinitely approach S 28 ＝t e =672 h=28d, if so t q2 If not, repeating the step 3 to calculate the curing age t q3 ＝t q2 Equivalent age t for +Δt=25h+1h=26h=1.08d e3 Up to t en Infinite approach S 28 ＝t e =672 h=28d, corresponding t qn For the curing age of the constant temperature rapid curing mode, t is obtained through continuous iteration q22 =45h is the curing age of the corresponding thermostatic fast curing mode of this example 2 and example 3, and the final curing age calculation result of the thermostatic fast curing mode is shown in table 1. It should be noted that the above calculation process can also be calculated quickly by calculation software.
Table 1 results of the temperature-constant fast curing method curing age calculation
While the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be understood that the foregoing embodiments are merely illustrative of the invention and are not intended to limit the invention, and that any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the present disclosure are intended to be included within the scope of the present disclosure.
Claims (9)
1. A method for rapidly optimizing the mix ratio of precast concrete elements, the method comprising:
determining the standard curing design strength v of concrete to be achieved by a precast concrete member 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 And determining the maturity S of the concrete at the end of 28d of standard curing of the concrete 28 ；
The mixing proportion of concrete is pre-determined, and two groups of concrete test pieces are prepared according to the mixing proportion;
curing one group of concrete test pieces in the two groups of concrete test pieces by adopting an actual rapid precast curing mode, and determining to obtain the actual strength sigma 'of the rapid precast concrete curing' t2 ；
Curing the other group of concrete test pieces in the two groups of concrete test pieces by adopting a constant-temperature rapid curing mode, and determining to obtain the concrete standard curing actual strength sigma' 28 ；
Judging actual strength sigma 'of concrete rapid prefabrication maintenance' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And concrete standard curing actual strength sigma' 28 Is greater than the standard curing design strength sigma of concrete 28 Whether the two are simultaneously established, if so, the requirements are met; otherwise, adjusting the mixing ratio of the concrete, and preparing two groups of concrete test pieces again according to the adjusted mixing ratio for curing and measuring until the actual strength sigma 'of the rapid precast curing of the concrete' t2 Is larger than the design strength sigma of concrete rapid prefabrication maintenance t2 And mixingConcrete standard curing actual strength sigma' 2s Is greater than the standard curing design strength sigma of concrete 28 And so on.
2. The method for rapidly optimizing the mix ratio of precast concrete units according to claim 1,
the standard curing design strength sigma of the concrete which needs to be achieved by the precast concrete member is determined 28 And the design strength sigma of concrete rapid prefabrication maintenance t2 Is determined according to the design index requirement of the precast concrete member;
determining the maturity S of the concrete at the end of 28 days of standard curing of the concrete 28 Is determined at a curing temperature of 20 ℃ and a relative humidity of greater than 95%.
3. The method of quickly optimizing the mix of precast concrete elements of claim 1, wherein the predetermined concrete mix is determined according to a concrete mix related design protocol.
4. The method for quickly optimizing the mix ratio of precast concrete units according to claim 1, wherein one of the two sets of concrete test pieces is cured by an actual quick precast curing method, and the actual strength sigma 'of the quick precast curing of the concrete is measured' t2 Comprising:
curing one group of concrete test pieces in the two groups of concrete test pieces according to the actual rapid precast curing mode requirement in the precast concrete member production process, and measuring the strength of the test pieces by adopting a standard test method after curing, wherein the measured strength is the actual strength sigma 'of the rapid precast concrete curing' t2 。
5. The method for rapidly optimizing the mix ratio of precast concrete units according to claim 4, wherein the actual rapid precast curing mode is determined by a curing process for the production and preparation of precast units, and the curing parameters include at least a dead time periodt 1 Rest temperature T 1 Rate of temperature rise v 1 Constant temperature duration t 2 Constant temperature T 2 Cooling rate v 2 And a total time t of rapid maintenance 3 。
6. The method for quickly optimizing the mix proportion of precast concrete units according to claim 1, wherein the other one of the two sets of concrete test pieces is cured by adopting a constant temperature quick curing mode, and the standard curing actual strength sigma 'of the concrete is measured' 28 Comprising:
curing the other group of concrete test pieces in the two groups of concrete test pieces by adopting a constant-temperature rapid curing mode, wherein the curing temperature adopted by the constant-temperature rapid curing mode is higher than the curing temperature adopted by a standard curing mode of 28d, and the strength of the test pieces is measured by adopting a standard test method after curing is finished, so that the measured strength is the standard curing actual strength sigma 'of the concrete' 28 。
7. The method for rapidly optimizing the mix proportion of precast concrete units according to claim 6, characterized in that in the constant temperature rapid curing mode, the curing temperature used is selected according to laboratory conditions, and the range of selection of the curing temperature is 40-75 ℃; the required curing age t q According to the maturity S of the concrete at the end of 28d adopting standard curing 28 And (5) reversely pushing to obtain the product.
8. The method for rapid optimization of the mix proportion of precast concrete elements according to claim 7, characterized in that the maturity S of the concrete 28 By equivalent age t e Characterization, the equivalent age calculation formula is as follows:
wherein:
U aT ＝(43830-43T)e (-0.00017T)t
in the middle of: r is a gas constant, 8.314J/mol.K; u (U) ar The cement hydration reaction activation energy at the standard curing temperature; u (U) aT The reaction activation energy at a temperature T is a function of time and temperature.
9. The method for rapid optimizing precast concrete unit mix ratio of claim 1, wherein the adjusting the mix ratio of the concrete is at least one of the group consisting of selecting a cement with a high grade, reducing a water cement ratio, improving a grain size distribution of coarse and fine aggregates, incorporating a high efficiency active mineral reference, or incorporating a high efficiency water reducing agent.
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| CN202210462383.9A CN114654576A (en) | 2022-04-28 | 2022-04-28 | Method for quickly optimizing mix proportion of precast concrete components |
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| CN104020046A (en) * | 2014-06-04 | 2014-09-03 | 王卫仑 | Method for estimating compressive strength of concrete in early stage |
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| CN104950099A (en) * | 2015-06-17 | 2015-09-30 | 福建省大地管桩有限公司 | Autoclave curing concrete admixture activity index inspection method |
| CN110451891A (en) * | 2019-08-27 | 2019-11-15 | 黑龙江盛世新宇高新技术开发有限公司 | Light high strength concrete mixing proportion design method |
| CN110962224A (en) * | 2019-12-31 | 2020-04-07 | 天津中匠建筑科技有限公司 | Test method and device for acquiring steam curing parameters of prefabricated part at low temperature and steam curing method |
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