Test method and device for acquiring steam curing parameters of prefabricated part at low temperature and steam curing method
Technical Field
The invention belongs to the field of building prefabricated parts, and particularly relates to a method and a device for acquiring and testing steam curing parameters of a prefabricated part at a low temperature and a steam curing method.
Background
The traditional concrete prefabricated part curing method comprises the modes of natural curing, steam curing, hot mixed concrete hot mold curing, solar curing, far infrared curing and the like, and two modes of natural curing and steam curing are commonly used. The natural curing cost is low, the operation is simple and easy, but the curing time is long, the template turnover rate is low, the occupied area is large, the curing time can be shortened by steam curing, the template turnover rate is correspondingly improved, and the occupied area is greatly reduced. Steam curing is to place the component in a curing chamber containing saturated steam or a mixture of steam and air, and cure the component in an environment of high temperature and humidity to accelerate hydration of the concrete and make the concrete reach a specified strength standard value in a short time.
Currently, the prior art means of steam curing commonly used in the industry are such:
in order to improve the early strength of the prefabricated parts, each prefabricated part factory usually adopts a steam curing method to accelerate the hydration of concrete, shorten the form removal time, accelerate the turnover of the form and improve the production efficiency. The time and temperature settings of steam curing can have different degrees of impact on the early strength, the later strength and the quality of the finished product of the concrete.
At present, two phenomena of steam curing of prefabricated parts exist: firstly, the steam curing time is reduced, the demoulding efficiency is accelerated, the standing time is reduced, the heating rate is accelerated, and the constant temperature is increased; and secondly, the time parameter setting of four stages of steam curing is not scientific, so that the curing time is long and the good demolding effect cannot be achieved.
In the prior art, the steam curing static time is generally 2 hours, the constant temperature is 40-60 ℃, and the steam curing time is 8-14 hours, the scheme specifies steam curing parameters for different mold-entering temperatures, the static time is controlled to be 3-6 hours, the constant temperature is 30-50 ℃, and the steam curing time is 8-13 hours, so that the demolding strength is met, the member has no phenomena of peeling, cracking and the like, and the strength growth rule of the 7d and 28d age stages has no retraction phenomenon.
In summary, the problems of the prior art are as follows: the steam curing device for the fixed mould table is unreasonable, the steam loss is large, and the utilization rate is low; steam curing of prefabricated parts, no steam curing parameter values are specified for different mold-entering temperatures, the steam curing cost of the prefabricated parts is high at the present stage, and the quality of the prefabricated parts is always problematic after steam curing. The concrete steam curing mainly comprises a series of physical and chemical reactions such as accelerating hydration and hardening of newly-mixed concrete, wherein the newly-poured concrete comprises cement paste, coarse and fine aggregates, air bubbles and water, the steam curing process mainly comprises the steps of curing the concrete in damp and hot steam, internal cracks appear under the thermal expansion effect of the concrete in the steam curing process, and the problems of peeling and cracking appear under the shrinkage in the cooling process.
Problems to be solved by the prior art
(1) The concrete steam curing device comprises a steam generation system, an automatic temperature control system and a curing cover. The problems of uncontrollable temperature, poor heat preservation and uneven heating temperature of concrete in the curing process are solved.
(2) And (3) aiming at concrete with different mold-entering temperatures, reasonable steam-curing parameters of each steam-curing process are specified, so that the quality problem of the member caused by steam curing is avoided.
(3) The steam curing of the component is carried out according to the steam curing process parameters, so that the cost is reduced, and the strength of the concrete is improved.
The difficulty in solving the technical problems is as follows:
the conventional steam curing mode of the prefabricated part is only curing through fixed parameter setting, the scheme needs to acquire the strength increase and the internal structure change rule in the hydration process through the stage data in the concrete hydration hardening process in the early stage, and then sets a plurality of parameters for different mold-entering temperatures to compare and verify the most reasonable steam curing parameter value.
The significance of solving the technical problems is as follows:
the steam curing parameters specified by different mold-entering temperatures can effectively solve the problems that the early strength is low in the production process of the prefabricated part, the steam utilization rate is low in the steam curing process of the prefabricated part of the fixed mold table and the steam curing cost is high in the prior art, the quality of the prefabricated part is improved, and the turnover of the mold table is accelerated.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a test method and device for acquiring steam curing parameters of a prefabricated part at a low temperature and a steam curing method for steam curing of the prefabricated part at the low temperature.
The invention is realized in such a way that a test method for acquiring steam curing parameters of a prefabricated part at low temperature comprises the following steps:
arranging a steam maintenance shed on the fixed mould table;
preparing concrete to be poured, and pouring the concrete on a fixed mould table, wherein the mold-entering temperature of the concrete is 5-15 ℃;
introducing steam with different temperatures into the steam curing shed, and performing a curing contrast test;
the maintenance contrast test is divided into four stages: a standing stage, a heating stage, a constant temperature stage and a cooling stage; a temperature probe is arranged in the curing shed, and the steam temperature is adjusted according to the temperature requirement of each stage;
and judging whether the stripping strength is met or not, and reserving steam curing parameters meeting the stripping strength.
In one embodiment, the concrete has a rest time of 3-6 hours; the static temperature is 5-30 ℃.
In one embodiment, the constant temperature time is 3-6 hours; the constant temperature is 30-50 ℃.
The invention also aims to provide a test device suitable for the test method for acquiring the steam curing parameters of the prefabricated part at the low temperature.
The invention also aims to provide a steam curing method for the prefabricated part, which applies the curing parameters obtained by the low-temperature prefabricated part steam curing parameter acquisition test method and is suitable for steam curing of the prefabricated part at low temperature.
In summary, the advantages and positive effects of the invention are:
firstly, setting more excellent steam curing parameters aiming at different mold-entering temperatures (5 ℃, 10 ℃ and 15 ℃) of concrete at low temperature;
secondly, the finished product of the prefabricated part after being cured by the steam curing parameters is better in quality;
thirdly, the steam curing time is shortened, the turnover rate of the die is improved, and the steam curing cost is reduced.
Drawings
FIG. 1 is a flowchart illustrating steps of a method for testing acquisition of steam curing parameters of a prefabricated part at a low temperature according to an embodiment of the present invention;
Detailed Description
In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings.
Aiming at the problems in the prior art, the invention provides a test method and a device for acquiring steam curing parameters of a prefabricated part at low temperature and a steam curing method, and the invention is described in detail with reference to the attached drawing 1.
A test method for acquiring steam curing parameters of a prefabricated part at low temperature comprises the following steps:
step S01: arranging a steam maintenance shed on the fixed mould table;
step S02: preparing concrete to be poured, and pouring the concrete on a fixed mould table, wherein the mold-entering temperature of the concrete is 5-15 ℃;
step S03: introducing steam with different temperatures into the steam curing shed, and performing a curing contrast test;
step S04: the maintenance contrast test is divided into four stages: a standing stage, a heating stage, a constant temperature stage and a cooling stage; a temperature probe is arranged in the curing shed, and the steam temperature is adjusted according to the temperature requirement of each stage;
step S05: and judging whether the stripping strength is met or not, and reserving steam curing parameters meeting the stripping strength.
In the example, the raw materials and varieties used for preparing the concrete are cement P.O42.5, fly ash grade II, river sand fineness modulus of 2.5, bluestone maximum particle size of 25mm, and the additive is a polycarboxylic acid high-efficiency water reducing agent.
In the example, the concrete mixing ratio of the comparative test is fixed and is set quantitatively.
Preferably, the concrete has a rest time of 3-6 hours; the static stop temperature is 5-30 ℃, and it is further pointed out that the static stop time of the concrete can be 3 hours, 4 hours, 5 hours and 6 hours respectively; the static stop temperature can be 5 ℃, 15 ℃, 25 ℃ and 30 ℃ respectively.
Preferably, the constant temperature time is 3-6 hours; the constant temperature is 30-60 ℃, and it is further pointed out that the constant temperature time can be 3 hours, 4 hours, 5 hours and 6 hours respectively; the constant temperature can be 30 ℃, 40 ℃, 50 ℃ and 60 ℃.
The invention also aims to provide a test device suitable for the test method for acquiring the steam curing parameters of the prefabricated part at the low temperature.
Preferably, the steam is prepared by an electric boiler and then is introduced into the curing shed through a pipeline, the temperature control assembly is placed in the curing shed and comprises a temperature probe and an automatic control valve, the temperature probe is used for detecting the real-time temperature in the curing shed, and the automatic control valve is used for controlling the steam feeding amount according to the real-time temperature feedback of the temperature probe, so that the curing temperature is controlled.
The invention also aims to provide a steam curing method for the prefabricated part, which applies the curing parameters obtained by the low-temperature prefabricated part steam curing parameter acquisition test method and is suitable for steam curing of the prefabricated part at low temperature.
Temperature of entering mould
|
Strength of demold
|
Steaming time
|
3d strength
|
7d strength
|
5℃
|
22.5Mpa
|
12.5h
|
30.1
|
40.6
|
10℃
|
22.6Mpa
|
11.5h
|
38.2
|
44.4
|
15℃
|
29.6Mpa
|
12.5h
|
34.2
|
39.2 |
Example one
The method is carried out by combining a fixed die table production line, a temperature probe is put into a maintenance shed, and the temperature is controlled by an automatic temperature control regulating valve;
the mixing proportion of the concrete in the whole test is fixed;
the steam curing is divided into four stages of a static stop stage, a temperature rising stage, a constant temperature stage and a temperature reduction stage
When the mold-entering temperature is 5 ℃, the static temperature is calculated for 4 hours from the completion of concrete pouring, and the static temperature is 20 ℃.
The heating rate of the heating stage is 20 ℃/h, and the heating time is 1 hour
Keeping the temperature at 40 ℃ for 4 h;
the cooling rate is 10 ℃/h, and the cooling time is 3.5 hours.
The curing time from the static stop to the whole temperature reduction stage is 12.5 hours.
The heating rate is controlled by setting the time for the resting temperature to rise to the constant temperature, and in principle does not exceed 20 ℃/h, and the cooling rate is controlled by setting the time for the constant temperature to fall to the set temperature, and in principle does not exceed 10 ℃/h.
The verification shows that the demolding strength is 22.5Mpa after the steam curing is finished for 12.5 hours, the demolding strength is met, the quality of the member is good, the 3d strength is 30.1 after the steam curing is converted into standard curing, the strength in the 7d age period is 40.6Mpa, the strength growth rule does not influence the growth of the later strength.
Example two
When the mold-entering temperature is 10 ℃, the static temperature is calculated for 5 hours from the completion of concrete pouring, and the static temperature is 30 ℃.
The constant temperature is 30 ℃, and the constant temperature time is 4 hours;
the cooling rate is 10 ℃/h, and the cooling time is 2.5 hours.
The curing time from the standing to the cooling is 11.5 h.
The verification shows that the demolding strength is 22.6Mpa after the steam curing is finished for 11.5 hours, the demolding strength is met, the quality of the member is good, the 3d strength is 38.2 after the steam curing is converted into standard curing, the strength in the 7d age period is 44.4Mpa, and the strength increase rule does not influence the increase of the later strength.
Example 3
When the mold-entering temperature is 15 ℃, the static temperature is calculated for 4 hours from the completion of concrete pouring, and the static temperature is 30 ℃.
Keeping the temperature at 50 ℃ for 3 h;
the cooling rate is 10 ℃/h, and the cooling time is 4.5 hours.
The curing time from the static stop to the whole temperature reduction stage is 12 hours.
The verification proves that the demolding strength is 26.6Mpa after the steam curing for 12 hours is finished, the demolding strength is met, the quality of the member is good, the 3d strength is 34.2 after the steam curing is converted into standard curing, the 7d age strength is 39.2Mpa, the strength growth rule does not influence the growth of the later strength.
As can be seen from the comparison of the above table, the prefabricated part which meets the specification requirements has the drawing strength not lower than 15MPa and meets the design requirement of 75 percent, and the mark is taken
The method is the most reasonable parameter, the steam curing time for the member to reach the stripping strength is shortest, and the member has no peeling and cracking phenomena.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.