US3202737A

US3202737A - Method of manufacturing pressed concrete

Info

Publication number: US3202737A
Application number: US156692A
Authority: US
Inventors: Tsuda Yutaka
Original assignee: Yawata Iron and Steel Co Ltd
Current assignee: Yawata Iron and Steel Co Ltd
Priority date: 1961-12-04
Filing date: 1961-12-04
Publication date: 1965-08-24
Anticipated expiration: 1982-08-24

Description

Aug. 24, 1965 YUTAKA TSUDA METHOD OF MANUFACTURING PRESSED CONCRETE Filed D60. 4, 1961 2 B m h m. w W r 0 d w 7 .m 9 e 5 g m A D. m c 3 INVENTOR Yurclka Tsudcl BY [/Mrfifi {iv/WM ATTORNEYS United States Patent 3,292,737 METHOD OF MANUFACTURING PRESSED CONCRETE Yutaka Tsuda, Setagaya-ku, Tokyo, Japan, assignor to Yawata Iron & Steel Co., Ltd, Tokyo, Japm Filed Dec. 4, 1961, Ser. No. 156,692 2 Claims. (Cl. 264-71) This invention relates to a method of manufacturing pressed concrete.

Civil engineering works in which very strong concrete sheets, piles, beams and ties are used have recently increased so greatly that it is required to continuously massproduce them in a streamlined operation. However, it is usual that the strength of concrete will not come out unless a considerable time is taken. Therefore, a special consideration is further required in order to improve the strength within a short time and to manufacture structures requiring a high strength such as iron reinforced pressed concrete piles.

The present invention has solved those points mentioned above.

An object of the present invention is to provide a method of manufacturing iron reinforced pressed concrete sheets, piles and the like of high strength continuously within a short time while improving the strength.

FIGURE 1 of the accompanying drawings is a perspective view of a manufacturing apparatus for carrying out the method according to the present invention.

FIGURE 2 is a comparative diagram of compressive strength tests.

The present invention shall be detailed in the follow- First of all, an assembled iron reinforcement is made by cutting steel bars into proper lengths, assembling them and welding or jointing them at the respective contact points and said reinforcement is positioned in a molding box which is easy to assemble and disassemble. Concrete which is mixed and kneaded to such hardness as will make the concrete easily flow through said assembled iron reinforcement and into the corners of the molding box and which is not likely to make clearances or uneven parts is poured into the molding box by a fixed measured amount, is made uniform on the whole by means of a vibrator, and is finished so that the height of the surface may be constant and is covered with a lid.

Then the concrete in the molding box is molded under a strong pressure by means of a pressure oil device. In the light of experiments, a method of pressing in two steps in which preparatory pressure of about kg./cm. is first applied and then the pressure is elevated to about 20 kg./cm. and is preferably applied continuously. That is to say, by the preparatory pressing, the concrete mass packed in the molding box and not yet hardened is made horizontal at a fixed height and the more or less irregular surface thereof is made smooth. Therefore, when a further higher pressure is applied, the pressure distribution will be able to be easily made uniform. F urther, as any quick pressure is avoided, the position of the axis of the prestressed steel bar or the assembled iron reinforcement can be stabilized, water in the concrete can be made to float up in the direction of the pressure and thus water can be prevented from remaining in the concrete. When the concrete mass in the molding box is made smooth by the preparatory pressing, the pressure is further elevated to about 20 kg./cm. This predetermined pressure is applied uniformly to each part of the long concrete mass for 6 to 8 minutes by means of the same oil pressure device. The amount of water which remains in the concrete after the compression has been finished, is about 23%.

Too

The compressing device is so arranged that the compressed state of the concrete may be kept as the pressure being applied after the pressing force is released.

Then the molding box and the upper lid are integrally fastened together so that the density of each part of the compressed concrete mass may be uniform. The molding box containing the compressed concrete mass is removed from the pressing device and transferred to the steam curing chamber in order to carry out the curing of the concrete mass in the compressed state as the pressure is being applied. The highest steam curing temperature of ordinary concrete is said in literature to be about 60 C. But, in this case, the temperature of steam may be elevated to C. The temperature rise in such case is for 5 to 10'minutes and is kept for about 2 hours and 30 minutes. The concrete compressed and held in the molding box will begin to harden quickly due to external heat.

The apparatus for carrying out the above described pressing molding shall be explained with reference to the drawings.

A molding box consisting of side wall members made of steel channel 10, a bottom steel plate 12 and bottom members made of steel channel 13 is covered with a lid consisting of cover members made of channel steel 8 and ceiling steel plate 9. Several fixed stands 7 having inclined upper surfaces on the right and left are provided on the upper surface of said lid in a certain distance respectively. Several frames 5 which correspond to said fixed stands in number, are arranged over said molding box. A pair of cotters 6 is fitted between each fixed stand and each frame 5. The angles of inclination of said each stand and said cotters are so arranged that the horizontal component of the stationary frictional forces may be larger than the horizontal component of the slipping force of said cotters, so that the cotters may not slip back to the position where they had stood before they were pushed, even if the pushing from the both sides is released. Each frame 5 is so formed as to be able to be easily disassembled by pulling out the cotters on both sides. On both sides of the frame 5 are arranged oil pressure cylinders 3. Push rods 4 of the molding box are pushed with the piston rods of the oil pressure cylinders 3 so that the cotters 6 may approach each other from both sides. To each oil pressure cylinder 3 are connected a pressure oil feeding pipe 1 and a return oil pipe 2. Said pressure oil feeding pipe 1 and return oil pipe 2 are connected to an oil pressure pump 16 and an oil storage tank 18 through a switching valve 15. Between the oil pressure pump 16 and the switching valve 15 are provided an accumulator 17 and a pressure regulating valve 14 so as to make the pressure in all the cylinders uniform.

Now, if concrete 11 kneaded at a proper mixing ratio is poured in the molding box, is pounded and vibrated so that there may be no clearance and uneven part but the whole may be uniform and is covered with the lid, the frames 5 are assembled, the cotters 6 are fitted, the push rods 4 are set against the cotters, the piston rod of the oil pressure cylinder 3 is set against each push rod and a pressure oil of a predetermined pressure is fed to the pressure oil feeding pipe 1 of each cylinder through the switching valve 15 by operating the oil pressure pump 16, each cylinder will push the cotter with a uniform pressure and a pressure will be applied to the concrete 11. In case the pressure resistance in a part of the concrete 11 is low, the pressure oil will be fed into the cylinder of that part so that the whole may press the concrete with a predetermined uniform pressure. Thus, however long or wide the concrete may be, it will be compressed in each part uniformly under a predetermine pressure for a fixed time. When the molding box with this pressure as applied is conveyed to a curing chamber and is cured, very strong pressed concrete will be made. Further, in the present invention, the pressure oil pipe and the oil pipe connected to each cylinder are in common, the oil pressure fed to all the cylinders is regulated to be constant as desired through the pressure regulating valve provided near the oil pressure feeding source and, even when there is any fluctuation of the oil pressure, the pressure will be directly kept constant in response to the fluctuation. Therefore, the concrete produce will be cured under a uniform pressure on the whole surface and will be able to form a product having no weak points.

According to the present invention, assembled iron reinforcements or prestressed steel bars are set in such molding box as is described above, mixed and kneaded concrete having such softness as will produce no clearance behind the iron reinforcements and in the corner parts of the molding box is poured into the molding box, the lid is mounted on the concrete, a pressure is thus applied to the concrete for a fixed time so that the density may be high, any unstable aggregate may be stabilized and excess water may be squeezed out to make the Water content best adapted to obtain the maximum strength in steam curing, the concrete while still under pressure is cured with steam and is, as required, taken out of the moulding box and cured in water.

The strength of the pressed concrete according to the present invention is much higher than that of the ordinary concrete. The comparative diagram is as shown in FIGURE 2. There are shown results that the pressed concrete according to the present invention has a strength more than twice as high as that of ordinary concrete and is superior in wear strength tests.

The method of the present invention can be applied to the manufacturer of piles, beams, ties, pillars, plates and the like.

What I claim is:

1. A method of manufacturing pressed concrete of high strength, comprising the steps of placing a mass of concrete in a mold having at least one part thereof movable into the interior of the mold, vibrating the mass of concrete in the mold for insuring even distribution of the concrete in the mold, mechanically applying pressure to the movable part of the mold for moving it into the mold and thereby applying a pressure of about kg./cm. to the concrete in the mold, then increasing the mechanical pressure to about kg./cm. for about 6-8 minutes and reducing the water content of the concrete in the mold to about 23% by squeezing out excess water, and then while still maintaining said mechanical pressure of about 20 kg./cm. applying steam to the exterior of the mold to heat the concrete within the mold to about C. in order to cure the concrete.

2. A method of manufacturing pressed concrete of high strength, comprising the steps of placing a mass of concrete in a mold apparatus having at least one part thereof movable into the interior of the mold and having means for holding the movable part in position after a force has been applied to it to apply pressure to concrete within the mold apparatus, vibrating the mass of concrete in the mold for insuring even distribution of the concrete in the mold, applying a force to the movable mold part through said holding means for moving the movable mold part into the mold and thereby applying a pressure of about 10 kg./cm. to the concrete in the mold, then increasing the force until the pressure on the concrete is about 20 kg./cm. and holding the pressure for about 6-8 min. and reducing the water content of the concrete in the mold to about 23% by squeezing out excess water, and then with the holding means holding the pressure on the movable mold part and thus on the concrete in the mold, placing the mold apparatus in a steam curing chamber and filling the steam chamber with steam at 100 C. for heating the mold apparatus to cure the concrete.

References Cited by the Examiner UNITED STATES PATENTS 840,990 1/07 Chailly 25-84 961,046 6/10 Turley 25--84 1,327,710 1/20 Hemstreet 25-102 1,514,936 11/24 Seifert 264-82 1,599,413 9/26 Harrison 264-82 2,311,358 2/43 Baily 25155 2,336,982 12/43 Cremer. 2,433,265 12/47 Denning. 2,437,003 3/48 Ruegy 2584 2,476,653 7/49 Elberty 2583 2,585,193 2/52 Vesper 2584 2,622,303 12/52 Wilson 26482 3,034,192 5/62 Maillard 25154 FOREIGN PATENTS 100,076 1/ 37 Australia.

ROBERT F. WHITE, Primary Examiner. ALEXANDER H. BRODMERKEL, Examiner,

Claims

1. A METHOD OF MANUFACTURING PRESSED CONCRETE OF HIGH STRENGTH, COMPRISING THE STEPS OF PLACING A MASS OF CONCRETE IN A MOLD HAVING AT LEAST ONE LPART THEREOF MOVABLE INTO THE INTERIOR OF THE MOLD, VIBRATING THE MASS OF CONCRETE IN THE MOLD FOR INSURING EVEN DISTRIBUTION OF THE CONCRETE IN THE MOLD, MECHANICALLY APPLYING PRESSURE TO THE MOVABLE PART OF THE MOLD FOR MOVING IT INTO THE MOLD AND THEREBY APPLYING A PRESSURE JOF ABOUT 10 KG./CM.2 TO THE CONCRETE IN THE MOLD, THEN INCREASING THE MECHANICAL LPRESSURE TO ABOUT 20KG./CM.2 FOR ABOUT 6-8 MINUTES AND REDUCING THE WATER CONTENT OF THE CONCRETE IN THE MOLE TO ABOUT 23% BY SQUEEZING OUT EXCESS WATER, AND THEN WHILE STILL MAINTAINING SAID MECHANICAL PRESSURE OF ABOUT 20 KG./CM.2 APPLYING STEAM TO THE EXTERIOR OF THE MOLD TO HEAT THE CONCRETE WITHIN THE MOLD TO ABOUT 100*C. IN ORDER TO CURE THE CONCRETE.