JP2000145018A - After-bond method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an after-bond method which is easy in execution control and inexpensive. SOLUTION: In an after-bond method, a concrete is placed in a pre-stressed concrete structure, and then, the pre-stress is introduced at a specified age of the material to demonstrate the adhesion to the concrete. A cement grout to be filled between a PC steel 2 and a sheath 1 is a cement grout 3 to which a setting retarder is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressed concrete structure used for railways, heavy vehicles, buildings, etc., in which the prestressing is introduced at a predetermined time after the concrete is driven, and the adhesion to the concrete is exhibited. Related to the after bond method.

[0002]

2. Description of the Related Art As is well known, in prestressed concrete structures in railways, automobiles, buildings, and the like,
The after-bond method, in which the adhesion between PC steel and concrete is demonstrated after introducing prestress at a predetermined time after the concrete is poured, does not require the placement of the sheath and the injection of cement grout at the construction site. Since the thickness of the member can be reduced and the labor of construction can be reduced, it has been widely used so far.

[0003]

In the after-bonding method, a room-temperature-curable resin is filled between the PC steel and the sheath, and the "post-curing" property of the resin is utilized. The resin is mainly composed of an epoxy resin which is a thermosetting resin, and the curing period of the resin is set by the amount of a curing accelerator added thereto. However, since the curing period of the resin also varies depending on the ambient temperature, the production of after-bond PC steel requires a detailed meeting of the use conditions in advance, and the heat of curing of the concrete to be built is too high. In some cases, this method cannot be applied.
In addition, it is necessary to carry out tension work within one month from the delivery of the product, the product must be stored in a sheet etc. to avoid direct sunlight, and careful construction management is required. Met. In addition, these resins are very expensive, and the development of an inexpensive after-bonding method that is easy to perform in construction management has been required.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an inexpensive after-bonding method that is easy to manage in construction.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a prestressed concrete structure, in which a cement grout filled between a PC steel material and a sheath, which has been widely used so far, has a setting hardening time of concrete or mortar. By adding a large amount of a setting retarder, which is a kind of cement admixture for arbitrarily delaying cement, the cement grout can be maintained in an uncured state for several days to several months.

[0006]

Embodiments of the present invention will be described below. FIG. 1 is a view for explaining an after-bond cable used in the present invention, and FIG.
(B) is a side view partially cut. After inserting the PC steel material 2 made of wire into the sheath 1 having a corrugated surface,
Between the PC steel material and the sheath, an oxycarboxylate, lignin sulfonate or calcium phosphate or a setting retarder combining them is used so that the hydration reaction between cement and water is delayed for about one month to several months. After the cement grout mixed with the addition amount is appropriately adjusted, sealing is performed, and an after-bond cable system including a sheath 1, a PC steel material 2, and a cement grout 3 to which a large amount of a setting retarder is added is configured.

[0007] After that, as in the construction of the conventional after-bonding method, the reinforcing bar and the after-bond cable system of the present invention are arranged in a structure constituted by a mold for forming a structure, and after concrete is driven into the structure. When the concrete hardens and the required concrete strength is generated, the prestressing force is introduced by tensioning the PC steel 2. After the completion of the tension, the cement grout 3 to which the setting retarder between the PC steel material 2 and the sheath 1 is added with the lapse of time is hardened, and adhesion occurs between the concrete of the structure and the PC steel material 2 and the whole is Be integrated.

Next, a concrete example in which a setting retarder is added to concrete will be described. A setting retarder (oxycarboxylate) was added to concrete containing cement (specific gravity 3.16), fine aggregate (specific gravity 2.55), and coarse aggregate (specific gravity 2.60). Kneading temperature 2
The result as shown in FIG. 2 was obtained as a relationship between the addition rate of the setting retarder at 0 ° C. and the curing temperature. Figure 2 shows curing temperature 2
At 0 ° C and 65 ° C, the addition ratio is 1.0%, 1.5%, 2.0%
It shows the change in the compressive strength of the concrete with respect to the number of days elapsed. From this figure, the kneading temperature 2
At the time of standard curing at 0 ° C. and a curing temperature of 20 ° C., the number of days for setting delay of the concrete becomes remarkably longer with the increase in the addition rate of the setting retarder, and the rate of development of compressive strength becomes slower with the increase in the addition rate. You can see that it is. On the other hand, in the case of the kneading temperature of 20 ° C. and the curing temperature of 65 ° C., there is no remarkable difference in the delay effect due to the addition rate as in the standard curing.
It can be seen that the strength development is faster than in the standard curing.

FIG. 3 is a diagram for explaining the relationship between the rate of addition of the setting retarder and the kneading temperature. Here, the curing temperature is 65 ° C.
Of setting retarder and kneading temperature 20 ° C, 30
The relationship of ° C is shown. When the kneading temperature is increased, the start of curing and the speed of developing strength are slowed at the addition ratio of 1.0 and 1.5%, but the start of curing is somewhat accelerated at 2.0%. When the kneading temperature is high, the properties of compressive strength are almost equal regardless of the addition ratio.

FIG. 4 is a graph for explaining the relationship between the curing temperature and the development of the compressive strength, and shows the relationship between the compressive strength and the curing temperature at an addition rate of the setting retarder of 1.0%. In the case of the kneading temperature of 30 ° C. and the addition rate of 1.0%, the higher the curing temperature, the slower the start of curing and the speed of developing the strength.
In the case of ° C, it is particularly remarkable as compared with others.

In the above embodiment, a setting retarder is added to concrete. However, when a setting retarder is added to cement grout containing no aggregate, the hardening time is further extended as in the case of concrete. It is possible.

[0012]

As described above, the present invention proposes an after bond cable method comprising cement grout to which a large amount of a setting retarder has been added. The present invention relates to an after-bond cable method for a PC steel material and a sheath in a conventional prestressed concrete structure. By combining cement grout, which is a filler between the above, and a setting retarder generally used as a concrete admixture, the setting time of cement grout can be adjusted for several days to several months. In addition, the effect of the ambient temperature on cement grout to which the setting retarder has been added is significantly smaller than that of resin, so there is no longer any restriction on the use of the concrete to be built due to the heat of hardening, and tension work begins after the product is delivered. Since there is no restriction on the time until, the construction management becomes easy. In addition, setting retarders are inexpensive because they are a type of commonly used concrete admixture, and cement grout, which is a filler between a PC steel material and a sheath in conventional blessed concrete structures, is used. A very durable and economical after-bond cable system can be achieved by the combination of.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an after-bond cable used in the present invention.

FIG. 2 is a diagram illustrating the relationship between the addition rate of a setting retarder and the curing temperature.

FIG. 3 is a diagram illustrating the relationship between the addition rate of a setting retarder and the kneading temperature.

FIG. 4 is a diagram illustrating the relationship between the curing temperature and the development of compressive strength.

[Explanation of symbols]

1 ... sheath, 2 ... PC steel, 3 ... cement grout to which a large amount of setting retarder is added.

Claims (2)

[Claims] In a prestressed concrete structure, after the concrete is poured, a prestress is introduced at a predetermined material age, and then the space between the PC steel material and the sheath is filled in an after-bonding method that exhibits adhesion to the concrete. An after bond method, wherein the cement grout is a cement grout to which a setting retarder is added. 2. The after-bonding method according to claim 1, wherein the setting retarder is an oxycarboxylate, a lignin sulfonate, a calcium phosphate or a combination thereof.