JPH0260485B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for placing cement compositions (hereinafter referred to as mortars) made by adding water to cement, aggregate, etc., such as mortar and concrete slurry, and kneading them. [Problems to be solved by the invention] There are many voids (0.5 mm or more) inside the cured product obtained by hardening mortar, and this is a major factor in reducing the physical properties of the cured product. . In addition, in order to improve the strength of the hardened mortar, some attempts have been made to use mortars with a low water-cement ratio, but mortars with a low water-cement ratio have poor fluidity, and with normal casting methods, the voids are further reduced. There is a tendency to increase fluidization, and means to increase fluidization are required. This invention was made in view of the above circumstances. The purpose of this is to effectively remove relatively large voids (0.5 mm or more) called entrapment air, which have a negative effect on strength and physical properties, and to effectively remove the entrapment air, which has a negative effect on strength and physical properties. The purpose of the present invention is to propose a method for placing a cement composition that can impart high strength by increasing fluidity during casting and significantly reducing the voids in the hardened product obtained by placing. [Means for solving the problem] This method of placing mortar is to place mortar, which is made by adding water to cement, aggregate, etc., into the upper opening of a hopper whose lower end is tapered and open. The mortar is placed on a perforated plate with a large number of perforated holes, vibrates the hopper and the perforated plate, and causes the mortar to fall through the perforated holes into the hopper, and then from the opening at the bottom end of the hopper. It is characterized by being poured at least once. This method will be explained below using experimental examples shown in FIGS. 1, 2, and 3. In the experimental example shown in FIG. 1, a hopper 2 whose lower end has a truncated conical shape and is open is placed at the upper center of a horizontally placed formwork 1. A spherical perforated plate 4 having a large number of through holes 3 is attached to the upper opening position of the hopper 2. On the other hand, the rod-shaped vibrator 5 is placed on a platform 6 that moves up and down, and the vibrating rod 7 extending in the horizontal direction and the hopper 2 are connected by a connecting rod 8 projecting from the center above the hopper, and the driving device is installed. Assemble. In this state, the perforated plate 4 inside the hopper 2
A mortar 9 is placed on top of the hopper 2 and the perforated plate 4 are vibrated by operating the vibrator 5. This vibration causes the mortar 9 to move to the perforated plate 4.
falls into the hopper 2 below through the through hole 3,
It further descends along the tapered inner surface of the hopper and falls into the formwork 1 through the opening 10 at the lower end.
At this time, the gantry 6 is gradually moved at a speed commensurate with the rising speed of the height of the mortar 9 that has fallen into the formwork 1 to lift the hopper 2 upwards, and at the same time, the mortar 9 is supplied to achieve a predetermined amount of mortar. etc. are poured into the formwork. In addition, during this pouring, it is preferable to place the opening 10 as close as possible to the already hammered mortar surface and to pour the mortar continuously. In Fig. 2, a perforated plate 4' with a conical lower end and a large number of through holes 3 is attached to the upper opening position of the hopper 2 instead of the spherical perforated plate 4 shown in Fig. 1. The upper center portion is connected to the bar-shaped vibrator 5 with a connecting rod 8 to assemble the casting device. In this case as well, the mortar 9 is placed on the upper surface of the perforated plate 4', and at the same time the perforated plate 4' and the hopper 2 are vibrated to cause the mortar 9 to fall through the through hole 3 and the hopper opening 10. Can be poured within 1. Figure 3 shows the hopper 2 of the pouring device used in Figure 1.
An exhaust port 11 is provided at a lower position of the perforated plate 4 in the hopper 2, and is connected to an exhaust pump 12.
Reduce the pressure in the space between the opening 10 and the mortar 9.
This is an example of actively promoting the removal of air bubbles inside. The perforated plates used in this pouring method have various surface shapes such as spherical, conical, and flat. In addition to circular cross-sections, the through holes can be polygonal, oval, etc., with diameters ranging from several mm to several cm, and are selected in consideration of the aggregate diameter of the mortar, slump value, etc. For example, in the case of a mortar using sand with a particle size D≧1.2 mm in Experimental Example No. described below, it was suitable to use through holes with a circular cross section and a hole diameter of 7.8 mm.
The frequency of vibration is in the range of about 6000 to 14000 vpm, and in the examples described later, suitable results were obtained with vibration of 12000 vpm. [Operation] In this casting method, the mortar is subjected to a pushing force accompanied by intense vibrations during the process of passing through the narrow holes of the perforated plate or falling through the opening of the hopper, causing the solid particles to The mesh becomes disengaged and resistance to shearing force is lost, resulting in liquefaction and significantly increased fluidity. Therefore, the removal of air bubbles in the mortar is facilitated, dense filling can be achieved without creating defects during casting, and a cured product with extremely few voids can be produced. [Experimental Example] Mortar having the composition shown in Table 1 was prepared, and a test specimen was prepared by casting and hardening it by the casting method shown in FIG. 3 above. At the same time, a test specimen of a comparative example was made by hand pouring.

[Table] The porosity, apparent specific gravity, bending strength, and compressive strength of the test specimens made in the experimental examples and comparative examples were
Shown in the table.

【table】

[Development items]

An example of a suitable pouring device for carrying out this pouring method on a practical scale is shown in FIG. In this device, a driving hopper 13 is suspended and attached under a cart 15 running on a rail 14, so that it can run along the surface of a horizontally placed formwork 1. The driving hopper 13 has a horizontal plane and a perforated plate 4 attached to the center thereof, and has a tapered lower end space 16 with a triangular cross section at the bottom thereof, and an opening 10 is opened near one side of the tip thereof. , the perforated plate 4 has a mounting space 17 for placing mortar 9 on the top thereof. Further, oscillators 18, 18 are attached in contact with both outer surfaces of the lower end, an exhaust port 11 is provided, and the lower end space 16 communicates with an exhaust pump 12. The driving hopper 13 is attached to the truck 15 via a vibration isolator 19. To place mortar using this device,
The height of the pouring hopper 13 is adjusted so that the height of the opening 10 from the bottom of the formwork 1 is approximately equal to the thickness of the mortar to be poured, and the mortar 9 is placed on the perforated plate 4. It is supplied to the upper mounting space 17, and the oscillator and exhaust pump are activated to give vibration and exhaust the inside of the lower end space 16. The mortar 9 falls from the through hole 3 to the lower end 16 of the hopper, and further falls into the formwork 1 from the opening 10. The cart 15 is made to travel following the amount of mortar 9 falling, and the position of the hopper opening 10 is moved to achieve a desired thickness, and the mortar 9 is cast into the formwork 1. [Effects of the Invention] This invention is as described above. According to this method, voids in the cured mortar can be significantly reduced and high strength can be developed. Furthermore, mortar can be placed with good workability using a simple device.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are partial cross-sectional views of the method and equipment for placing mortar in the experimental example, respectively;
Figure 5 is a correlation graph between the pore diameter and the integrated value of the pore area for experiment No., respectively, Figures 6 and 7 are correlation graphs between the pore diameter and the number of pores for experiment No., respectively, and Figure 8 is a graph for this method. Longitudinal cross-sectional view of a pouring device suitable for implementation on a practical scale, Figures 9 and 10a,
b is a photograph showing the surface particle structure of the test specimens of Experiment No., Experimental Example, and Comparative Example, respectively. 1...Formwork, 2...Hopper, 3...Through hole,
4, 4'... Perforated plate, 5... Rod-shaped vibrator, 6... Frame, 7... Vibration rod, 8... Connection rod,
9... mortar, 10... opening, 11... exhaust port, 12... exhaust pump, 13... driving hopper, 14... rail, 15... trolley, 16...
Lower end space, 17... mounting space, 18... oscillator, 19... vibration isolator.

Claims (1)

[Claims] 1 A cement composition obtained by adding water to cement, aggregate, etc. and kneading it is placed on a perforated plate with a large number of through holes arranged at the upper opening position of a hopper whose lower end is tapered and opened. , the cement composition is cast by applying vibration to the hopper and the perforated plate, causing the cement composition to fall into the hopper through the through holes, and further falling from the opening at the lower end of the hopper. How to set it up.