JPS638279A - Normal pressure vapor curing process for fiber reinforced lightweight concrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a method for curing concrete, and in particular, to a method for curing fiber-reinforced lightweight concrete in a normal-pressure steam atmosphere. be.

"Prior Art" In general, concrete is subjected to normal pressure steam curing as a means of obtaining the strength required to remove it from a molding form, so-called compressive strength upon demolding.

This atmospheric pressure steam curing involves pouring mixed concrete into formwork, holding it in outside air for a predetermined period of time (pre-curing), and then holding it in atmospheric pressure steam at a maximum temperature for a predetermined period of time (pre-curing). After that, the temperature of the steam was gradually lowered to the outside temperature (post-curing).

The above-mentioned pre-curing is designed to prevent this problem, since applying heat to concrete immediately after pouring will have an adverse effect on the composition and physical properties of the concrete. The highest temperature in the curing process! The compressive strength of the concrete upon demolding is determined by the relationship between the time and the retention time.

Conventionally, for example, in order to obtain a compressive strength at demolding of more than LOO (kg/c, *') required for concrete with a specific gravity of 23, the following conditions were always met. Pressure steam curing is performed.

Pre-curing time・・・・・・・・・・・・・・・・・・・・・
・・・・・・Temperature gradient until reaching the maximum temperature over 3.0 hours ・・Maximum temperature during main curing of 20°C/hour・・・・
・・・・・・・・・50°C maximum temperature duration...
・・・・・・・・・・・・・・・・・・・・・3.5 hours ``Invention or problem to be solved'' The present invention solves the following problems in the conventional technology as described above. The aim is to solve these problems.

In other words, if the above-mentioned curing conditions for ordinary concrete cannot be applied to normal pressure steam curing of fiber-reinforced lightweight concrete, due to the nature of the fiber-reinforced lightweight concrete, within the time set in the pre-curing stage, If the hardness is not strong enough to withstand the temperature during the main curing, and the maximum temperature set during the main curing stage will have a negative impact on the reinforcing fibers and air bubbles in the semi-hardened fiber-reinforced lightweight concrete. This is a problem, such as the possibility that this may lead to a decline in quality.

In order to solve these problems, it is being considered to set the conditions for atmospheric pressure steam curing as shown below.

This condition is 10 (/
cy/cJ! 2) This is an example set to obtain the above compressive strength upon demolding.

Pre-curing time・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・Temperature gradient until the maximum temperature is reached for about 20 hours・・・・・・20°C/hour Maximum temperature during main curing・・・・・・・・・・・・・・・・・・・・・30°
C Maximum temperature duration・・・・・・・・・・・・・・・・・・
...4 hours or more However, even with these measures, the following 2m points remain that need improvement.

(2) The time required for the I cycle frequently exceeds 24 hours, making the manufacturing cycle inconsistent and, as a result, making the setup of the manufacturing process complicated.

■Due to surface aging factors, the implantation time gradually shifts, and the outside temperature during pre-curing changes, causing variations in curing conditions between each dot, even during a short manufacturing period.
Sen M1? This is a factor that adversely affects the quality of rff strong lightweight concrete.

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

7. The method for curing fiber-reinforced lightweight concrete with normal pressure steam according to the present invention involves setting the pre-curing time to at least 11 hours and performing normal-pressure steam curing at a maximum temperature of 40 degrees Celsius or less during main curing. This allows fiber-reinforced lightweight concrete through pre-curing to withstand the maximum temperature during main curing, and significantly shortens the period required for atmospheric pressure steam curing.

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

This example shows a case in which fiber-reinforced ultra-lightweight concrete with a specific gravity of 1.4 is given a demolding compressive strength of 70 Ckg/cm2).

First, fiber-reinforced ultralight concrete is produced by kneading a predetermined mixture and poured into formwork.

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

After this pre-curing is completed, the fiber-reinforced ultra-lightweight concrete is charged into a curing NV kept at about 20°C, and then heated steam is sent into the curing tank to
C/hour) While maintaining the temperature gradient, the temperature in the curing tank is raised to about 40° C., and this temperature state is left for about 4 hours to carry out main curing. The time it takes for the temperature inside the curing tank to reach 40°C is approximately 1 hour since the initial temperature inside the curing tank is 20°C. Therefore, the time required for the main curing is shown in Figure 1. So, about 1
It is 3 hours.

Subsequently, post-curing is carried out by gradually lowering the temperature of the steam supplied into the curing tank to reach the initial temperature inside the curing tank. The time required for the subsequent curing is approximately 4 hours, as shown in FIG.

Thereafter, after curing is completed, the fiber-reinforced lightweight concrete is transported together with the formwork from Tateki Yoyotsubaki and slowly cooled.1. , complete curing of fiber-reinforced lightweight concrete.

As a result of measuring the compressive strength upon demolding of the fiber-reinforced lightweight concrete that had been cured through the above process, the objective 7
A compressive strength upon demolding of 0(&9/Cx') was obtained, and as shown in FIG. 1, the total time required for atmospheric pressure steam curing was able to be kept within 24 hours.

By the way, if the maximum temperature during the main curing was set to 35°C and normal pressure steam curing was performed with other conditions being the same, the compressive strength upon demolding was 50 (k), as shown in Figure 2.
y/cm2), which was significantly lower than the target value (design value).Furthermore, when the maximum temperature was set to 50℃, the value after sprouting was 40 (kg/a12), which caused a loss of face. Similarly, the results were significantly lower than the target value. Furthermore, when the pre-curing time was carried out for 4 hours ± 1 hour while maintaining the maximum temperature at a suitable temperature, as shown in Figure 3, in the state where 5 hours was spent, The result was about 80 (&y/am2), which was above the target value, and after 3 hours, the result was about 53 (,'(!?/cff2), which was low.

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 lifted up and transported to a subsequent storage facility, etc., for ``fa-reinforcement''. Completed production of lightweight concrete.

Note that the conditions shown in the above examples are merely examples, and can be variously changed based on the type and mixing ratio of the Senkeura strong lightweight concrete to be applied.

Effects of the Invention J As explained above, the atmospheric pressure steam curing method for fiber-reinforced lightweight concrete according to the present invention involves pre-curing uncured fiber-reinforced lightweight concrete in the open air for at least 4 hours. After that, main curing is performed in normal pressure steam with a maximum temperature of 40 degrees Celsius or less, and then post-curing is performed while gradually lowering the steam temperature. Not only can the concrete have almost the desired compressive strength when demolding, but the total time required for atmospheric pressure steam curing can be kept within 24 hours, suppressing deviations in the production cycle of Senkeura strong lightweight concrete and increasing productivity. It has excellent effects such as increasing the quality and making the quality constant.

[Brief explanation of the drawing]

Fig. 1 is a process diagram for explaining one embodiment of the present invention, and Figs. 2 and 3 are characteristic curve diagrams of fiber-reinforced lightweight concrete to show the differences between the embodiment and a comparative example. .

Claims (1)

[Claims] After pre-curing the uncured fiber-reinforced lightweight concrete at outside temperature for at least 4 hours, main curing is performed in normal pressure steam with a maximum temperature of 40 degrees Celsius or less, and then the above-mentioned steam temperature is A normal pressure steam curing method for fiber-reinforced lightweight concrete, which is characterized by performing post-curing while gradually lowering the concrete.