JPH0753619B2 - Atmospheric pressure steam curing method for fiber reinforced lightweight concrete - Google Patents

Description

The present invention relates to a concrete curing method, and more particularly to a normal pressure steam curing method for curing fiber-reinforced lightweight concrete in a normal pressure steam atmosphere.

"Prior Art" Generally, in concrete, atmospheric pressure steam curing is performed as one means for obtaining the strength required to remove it from the molding frame, that is, so-called compression strength during demolding.

In this atmospheric steam curing, concrete after kneading is driven into the mold and then kept in the open air for a predetermined time (precuring).
Then, the steam is kept in atmospheric pressure steam for which a maximum temperature is set for a predetermined time (main curing), and then the temperature of the steam is gradually lowered to the outside air temperature (post curing).

The pre-curing is set in order to prevent this problem, since the composition and physical properties of the concrete will be adversely affected when heat is applied to the concrete immediately after the driving, and the pre-curing is also performed. The product of the maximum temperature at and its duration determines the demolding compressive strength of the concrete.

Conventionally, for example, in order to obtain a compressive strength at demolding of 100 (kg / cm ² ) or more, which is required for ordinary concrete with a specific gravity of 2.3, under normal pressure steam curing under the following conditions. It is carried out.

Pre-curing time …… 3.0 hours or more Temperature gradient until reaching the maximum temperature …… 20 ℃ / hour Maximum temperature during main curing …… 50 ℃ Maximum temperature duration …… 3.5 hours “Problems to be solved by the invention” book The present invention is intended to solve the following problems in the above-described conventional technology.

That is, when the curing conditions of the ordinary concrete described above are not applied to the normal pressure steam curing of the fiber reinforced lightweight concrete, due to the properties of the fiber reinforced lightweight concrete, within the time set in the pre-curing stage, in the main curing If the hardness is not high enough to withstand the temperature, and if it is the maximum temperature set during the main curing stage, it will adversely affect the reinforcing fibers and bubbles in the fiber-reinforced lightweight concrete in the semi-hardened state, and It is a problem that there is a possibility that it may cause a decrease in

In order to solve such a problem, it has been considered to set the conditions of atmospheric pressure steam curing as shown below.
This condition is 10 (kg / cm ² ) when normal pressure steam curing is applied to fiber reinforced ultralight concrete with specific gravity of 1.4.
This is an example set in order to obtain the above compression strength at the time of demolding.

Pre-curing time …… Approx. 20 hours Temperature gradient to reach maximum temperature …… 20 ℃ / hour Maximum temperature during main curing …… 30 ℃ Maximum temperature duration …… 4 hours or more However, even with such measures, The following problems remain to be improved.

The time required for one cycle easily exceeds 24 hours, the manufacturing cycle is not constant, and as a result, the preparation of the manufacturing process is complicated.

Due to the above factors, the driving time is gradually shifted, the outside air temperature at the time of previous curing changes, and even during a short manufacturing period, each dot causes a change in curing condition,
This is a factor that adversely affects the quality of fiber reinforced lightweight concrete.

"Means for Solving Problems" The present invention is intended to provide a method for atmospheric pressure steam curing of fiber-reinforced lightweight concrete that can effectively solve the problems in the above-mentioned conventional techniques, and is in an uncured state. After pre-curing the fiber reinforced lightweight concrete of above for at least 4 hours in the outside air temperature, the main curing is carried out in the atmospheric pressure steam with the maximum temperature of 40 degrees Celsius or less, and then the steam temperature is gradually increased. It is characterized by performing post-curing while descending.

[Operation] The atmospheric pressure steam curing method for fiber-reinforced lightweight concrete according to the present invention is performed by performing atmospheric pressure steam curing with a pre-curing time of at least 4 hours or more and a maximum temperature during main curing of 40 degrees Celsius or less. The purpose is to make the fiber-reinforced lightweight concrete by pre-curing into a state capable of withstanding the maximum temperature in the main curing, and to significantly shorten the period required for normal-pressure steam curing.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

This example shows a case where a fiber-reinforced ultralight concrete having a specific gravity of 1.4 is given a demolding compressive strength of 70 (kg / cm ² ).

First, a fiber-reinforced ultra-lightweight concrete is produced by kneading a predetermined mixture and is poured into a mold.

Then, as shown in the process diagram of FIG. 1, this fiber-reinforced ultralight concrete is left in the open air for about 4 hours together with the formwork for pre-curing.

After the pre-curing is completed, the fiber reinforced ultralight concrete is charged into a curing tank held at about 20 ° C., and then heating steam is fed into the curing tank to obtain 20 (° C./hour). Maintaining a temperature gradient, keep the temperature in the curing tank at about 40 ° C.
This temperature condition is continued for about 12 hours to carry out main curing. Where the temperature inside the curing tank is
The time to reach 40 ℃ is 20 ℃ in the initial curing tank.
Therefore, the time required for the main curing is about 13 hours, as shown in FIG.

Following this, post-curing is performed by gradually lowering the temperature of the steam supplied into the curing tank to the initial curing tank temperature. The time required for the subsequent curing is about 4 hours as shown in FIG.

After that, after the curing is completed, the fiber-reinforced lightweight concrete is carried out together with the formwork from the curing tank and gradually cooled, and then the temperature of the fiber-reinforced lightweight concrete is lowered to the outside air temperature. Complete light concrete curing.

As a result of measuring the compressive strength at the time of demolding of the fiber reinforced lightweight concrete that has been cured by the above steps, the target 70
A compression strength of (kg / cm ² ) at the time of demolding was obtained, and as shown in FIG. 1, the total time required for steam curing at atmospheric pressure could be kept within 24 hours.

By the way, the maximum temperature during the main curing is 35 ° C,
Moreover, when atmospheric pressure steam curing was performed under the same other conditions, as shown in Fig. 2, the compression strength during demolding was 50 (kg / c
It becomes m ²⁾ below where, result in less than the target value (design value) significantly, also set the maximum temperature 50 ° C., 40
The value was around (kg / cm ² ), which was much lower than the target value as in the former case. Furthermore, when the time required for pre-curing while maintaining the maximum temperature at a suitable temperature was carried out for each of 4 hours ± 1 hour, as shown in FIG. About 80 (kg
/ cm ² ), which was above the target value, and a low result of about 53 (kg / cm ² ) after 3 hours.

In this way, after confirming that the compressive strength of the fiber-reinforced lightweight concrete is within the target value, the fiber-reinforced lightweight concrete is hung up and carried out to a storage facility in the subsequent stage to produce the fiber-reinforced lightweight concrete. To complete.

It should be noted that the conditions shown in the above examples are merely examples, and can be variously changed based on the type and mixture ratio of the fiber-reinforced lightweight concrete mixture to be applied.

[Effects of the Invention] As described above, in the atmospheric pressure steam curing method for fiber-reinforced lightweight concrete according to the present invention, uncured fiber-reinforced lightweight concrete was pre-cured in the open air for at least 4 hours or more. After that, the main temperature is carried out in normal pressure steam of 40 degrees Celsius or less, and then the post curing is carried out while gradually lowering the steam temperature.
The fiber-reinforced lightweight concrete can have almost the desired compressive strength during demolding, and the total time required for steam curing at atmospheric pressure can be kept within 24 hours to suppress the deviation of the production cycle of the fiber-reinforced lightweight concrete and produce it. It has excellent effects such as improving the quality and making the quality constant.

[Brief description of drawings]

FIG. 1 is a process diagram for explaining an embodiment of the present invention, and FIGS. 2 and 3 are characteristic curve diagrams of fiber-reinforced lightweight concrete for showing the difference between the embodiment and the comparative example.

Claims (1)

[Claims] 1. An uncured fiber-reinforced lightweight concrete is pre-cured for at least 4 hours or more in the outside air temperature, and then main-cured in normal pressure steam having a maximum temperature of 40 degrees Celsius or less, Next, a method for normal pressure steam curing of fiber reinforced lightweight concrete, characterized in that post-curing is performed while gradually lowering the steam temperature.