JPS62122710A - Mixer for cooling 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 (Field of Industrial Application) The present invention relates to a mixer for cooling concrete that produces concrete with a low mixing temperature used in hot concrete and mass concrete construction.

(Prior art and its problems) When concrete is manufactured in the heat of the year, the mixing temperature increases, the amount of per unit soaking required to obtain the same consistency increases, and the unit cement field required to achieve the same water-cement ratio also increases. To increase. In addition, the slump of concrete during hot weather during transport increases, and the amount of cement per unit of water must be further increased. This is not only uneconomical, but also increases the temperature rise due to heat generation of the cement, and also increases drying shrinkage, making it more likely to cause defects such as cracks. Furthermore, it hardens more quickly, which reduces the time allowed for pouring and makes construction difficult.

In addition, in mass concrete, since concrete is a poor conductor of heat, the internal temperature rises as it hardens and generates heat, increasing the temperature difference between the inside and the outside surface, making surface cracks more likely to occur. . Furthermore, if the concrete is restrained from the outside, the shrinkage caused by the drop in temperature after hardening is restrained, resulting in large tensile stress.

For these reasons, it is necessary to take some measure to lower the temperature of hot concrete or mass concrete, and it is necessary to suppress the temperature rise due to heat generated by the hydration reaction of cement as much as possible.

Conventionally, in order to keep the mixing temperature of concrete low, methods such as cooling materials such as cement and aggregate with cold water, or cooling the concrete by adding ice to the concrete mixing tank water have been adopted. was.

Another method has been to install a cooling pipe at the concrete pouring site and run cold water through the pipe during and immediately after pouring concrete to lower the internal temperature of the concrete.

However, the method of cooling materials such as cement and aggregates with cold water requires large-scale cooling equipment to obtain cold water, but the cooling effect is not great, and concrete quality control is also difficult. Furthermore, the method of cooling the mixing tank water with ice requires large-scale ice-making equipment, and it is difficult to appropriately control the temperature and moisture content of the concrete. In any case, with conventional methods, it is difficult to cool a large amount of concrete to a sufficiently low temperature in an appropriate and efficient manner.

(Purpose of the Invention) This invention was devised in view of the above-mentioned problems of the conventional technology.The purpose of this invention is to efficiently reduce the temperature to a sufficiently low temperature when mixing concrete, which requires large-scale equipment, and has low operating costs. To provide a concrete cooling mixer capable of lowering the mixing temperature.

(Structure of the Invention) The concrete cooling mixer according to the present invention is configured such that a sealing lid is provided at the opening for introducing concrete material and discharging concrete, so that the inside of the mixing barrel can be sealed when concrete is mixed. The mixing cylinder, including the airtight lid, has a pressure-resistant structure that can withstand an internal pressure of at least 20k (1/crl), and the mixing cylinder has a nozzle section that supplies liquefied gas as a refrigerant for cooling concrete to the inside, and an internal gas It is equipped with a safety valve that releases internal gas to the outside when the pressure exceeds a set value.

(Embodiment) The figure shows the structure of a mixer for cooling concrete according to an embodiment of the present invention. This embodiment is a rotating barrel tilting mixer. The mixing cylinder 10 is attached to a support stand 12, and is rotatable around a central axis P as shown by the arrow a, and can also be tilted as shown by the arrow around a support shaft 16 orthogonal to the axis P. It has become. Mixing cylinder 10 as shown
The mixing cylinder 10 is connected to a motor 14 via a gear mechanism with its axis P slightly tilted with respect to the horizontal. In this state, the mixing cylinder 10 is rotated by the motor 14 as shown by arrow a.

The mixing unit 11i110 has a pot shape with only one end open, and concrete material is introduced through the opening 10a, and mixed concrete is discharged from the mixing unit 11i110. A seal M18 is attached to the opening 1Qa of the mixing barrel 10. The sealing lid 18 may be configured to be detachable from the mixing barrel 10, or may be connected to the mixing barrel 1110 by a hinge mechanism. In any case, when preparing the concrete material and discharging the mixed concrete, the sealing lid 18 is opened to widen the opening 10a. When concrete is mixed, the opening 10a is closed with the sealing lid 18, and the sealing lid 18 is tightened with the handle 18a.
0's internal space can be sealed.

The sealing lid 18 is provided with a safety valve 20 for communicating the inside and outside of the mixing barrel 10. As will be described later, the safety valve 28 opens when the internal pressure of the sealed mixing barrel 10 exceeds a set value, and acts to release internal gas to the outside and maintain the internal pressure at the set value.

In this embodiment, the operating pressure of the safety valve 20 is 35 kg/C. The mixing barrel 10 including the sealing lid 18 has a pressure of at least 40 kg, which is slightly higher than the operating pressure of the safety valve 20.
It has a pressure-resistant structure that can withstand an internal pressure of /cd. Of course, the higher the pressure resistance of the mixing cylinder 10, the better, and at least 20! J/c
rt is required.

A nozzle 22 for injecting liquid nitrogen is attached to the center of the inner bottom of the pot-shaped mixing barrel 10. The nozzle 22 has a pipe shape, is attached along the axis Pl of the mixing cylinder 10, and has a large number of holes around its tip.

The base of the nozzle 22 communicates with the outer surface side of the mixing cylinder 10 and
A rotary joint 24 is attached here.

In this embodiment, liquid nitrogen is used as a refrigerant for cooling concrete. Liquid nitrogen is stored in a tank 30, and the discharge valve 28 of the tank 30 and the rotary joint 24 are connected with a pressure hose 26. When the valve 28 is opened appropriately, liquid nitrogen is discharged from the tank 30 and supplied to the nozzle 22 through the hose 262 and the rotary joint 24.
Liquid nitrogen is ejected into the mixing barrel 10 from the holes.

In the above configuration, concrete material is put into the mixing barrel 10, the opening 10a is completely sealed with the sealing lid 18,
The motor 14 is driven to rotate the mixing cylinder 10 to mix concrete.

At the same time, the valve 28 is opened and liquid nitrogen is introduced into the nozzle 22.
It is ejected into the mixing cylinder 10 and sprayed onto the concrete material being mixed. Mix appropriate amount of liquid nitrogen 1110
Once the water has been supplied to the inside, the valve 28 may be closed to stop the supply.

The liquid nitrogen ejected from the nozzle 22 vaporizes within the mixing barrel 10, absorbs surrounding heat with its latent heat and apparent heat, and rapidly cools the concrete being mixed. The pressure inside the sealed mixing cylinder 10 rises due to the vaporized and expanded nitrogen gas, and when the pressure reaches 35 kg (+/cd), the safety valve 20 operates to gradually release the internal gas, causing the internal gas to rise to 35 kg/cd.
Maintain approximately CD pressure.

As is well known, under normal pressure, liquid nitrogen becomes 180 times its original volume when it vaporizes, and when the temperature rises to roughly 0°C, the volume expands 640 times compared to its liquid state. . Therefore, even if liquid nitrogen is introduced into an open space like a normal mixer to cool the concrete inside, the nitrogen gas, which has undergone significant volume expansion, will dissipate into the atmosphere from the space containing the concrete. As a result, the cold energy of liquid nitrogen or nitrogen gas cannot be fully utilized, and the cooling effect cannot be improved much.

However, according to the mixer of the present invention, liquid nitrogen is vaporized inside the sealed mixing device 10, which has a structure that can withstand high pressure, and the nitrogen gas is not released to the outside until the internal pressure becomes considerably high. Alternatively, the cooling energy possessed by nitrogen gas can be fully utilized, and the concrete being mixed can be efficiently cooled down to a sufficiently low temperature at a low cost.

Although the above embodiment was a rotary barrel type tilting mixer, the present invention is not limited to this type of mixer, and the present invention can be applied to any structure that can seal the inside of the mixing barrel during concrete mixing. Applicable.

(Effects of the Invention) As explained in detail above, according to the concrete cooling mixer according to the present invention, there is no need for large-scale incidental equipment, and the cooling energy of the liquefied gas as a refrigerant is efficiently used without wasting it. The concrete that is being mixed can be cooled very effectively, and concrete at a sufficiently low temperature can be efficiently produced with low operating costs.

[Brief explanation of drawings]

The figure is a configuration diagram of a concrete cooling mixer according to an embodiment of the present invention.

Claims (1)

[Claims] (1) A sealing lid is provided at the opening for introducing concrete materials and discharging concrete, so that the inside of the mixing barrel can be sealed during concrete mixing, and the mixing barrel including the sealing lid has a weight of at least 20 kg.
It has a pressure-resistant structure that can withstand an internal pressure of /cm^2, and has a nozzle part that supplies liquefied gas as a refrigerant for concrete cooling to the mixing cylinder, and a nozzle part that supplies internal gas to the outside when the internal gas pressure exceeds a set value. A mixer for cooling concrete, characterized in that it is equipped with a safety valve that releases water to the concrete.