JP3528640B2 - Quality control method of concrete using unwashed riverbed gravel as aggregate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quality control method for preparing concrete, particularly dam concrete. [0002] Conventional aggregates used for dam concrete include riverbed gravel and crushed stone, which are thoroughly washed in an aggregate plant, and fine aggregate (particle size of 5 mm or less), coarse aggregate (grain). Diameter 5m
m), and coarse aggregate is further classified into 5 mm to 20 mm, 20 mm
mm-40mm, 40mm-80mm, 80mm-150mm, etc., and it was confirmed that the fine aggregate and the classified coarse aggregate ensured the quality specified by the JIS standard. Used above. [0003] As described above, in the preparation of dam concrete, high quality fine aggregate and classified coarse aggregate are used, and it is considered that variation in concrete quality is small. As a method, a slump test is generally performed by sampling inspection about once every 1 to 2 hours. [0004] The inventors of the present invention have the prospect that riverbed gravel with a dense and hard tissue with few harmful components can be used as concrete aggregate even if washing is omitted. We are studying it. When using this unwashed river bed gravel as aggregate, aggregate more than 80 mm is cut from the unwashed river bed gravel and classified into roughly two or three coarse aggregates and fine aggregates and a predetermined amount. Is dry-blended with the cement, and the dry-blended solids are put into a stirring vessel of an agitator truck together with water and an admixture and kneaded to prepare concrete. [0005] By the way, even if unwashed riverbed and gravel is classified into several parts, it is inevitable that the quality varies widely depending on the sampling location. Naturally, concrete prepared using an aggregate that is considered to have a large variation in quality has to be considered to have a large variation in quality. For this reason, when preparing concrete using unwashed riverbed gravel as aggregate, it is impossible to carry out quality control at all by batch sampling inspection as in the case of conventional aggregates. Inspection is required. In addition, it is necessary to carry out the inspection early and in a short time, and to take necessary measures immediately, but no effective measures have been found so far. As a result of studying the above points with a focus on the basic formulations shown in Tables 1 and 2 below, it has been found that some concrete that has been continuously stirred in the stirring vessel of the agitator truck has It has been found that in the hard range (small slump value), the hydraulic pressure of the hydraulic motor, which is the power source for rotating the stirring vessel, changes in accordance with the change in the hardness of the concrete. (See Table 3 and FIG. 1) [Table 2] [Table 3] If this knowledge is applied, it is possible to sample concrete from a stirring vessel during stirring without testing.
By measuring the oil pressure of the hydraulic motor, it should be possible to accurately estimate the slump value and the strength after hardening of the concrete in the stirring vessel in real time. The present invention applies this knowledge to the inspection of all the concrete. [0011] That is, the present invention relates to a method of mixing a non-washed riverbed gravel cut to a size of more than 80 mm as an aggregate, and dry-blending the aggregate and a predetermined amount of cement together with water and an admixture to agitate an agitator truck. They were charged into a container, when to adjust the concrete kneading, the unwashed
River bed gravel is classified into fine aggregate and coarse aggregate,
The solid content of coarse aggregate and a predetermined amount of cement is semi-continuously dried.
After blending, remove the solids with less water and
The material is put into the stirring vessel together with the material, and the stirring vessel is
After high-speed rotation at first, normal low-speed rotation and continuous stirring
And the hydraulic pressure of the hydraulic motor that rotates the stirring vessel
Concrete in the stirring vessel estimated in real time from
Add an amount of water corresponding to the slump value of the
A concrete slump value of the concrete in the agitating vessel is slightly increased to a predetermined slump value by adding the concrete into the stirring vessel. Coarse aggregate of more than 80 mm is cut from unwashed riverbed gravel used as aggregate in the present invention. This is because coarse aggregates exceeding 80 mm are not only difficult to put into the stirring vessel of the agitator truck, but if they are thrown in, there is a risk that mixing by the stirring of the agitator truck may become impossible due to mechanical factors. Because it is big. [0013] Usually, it is classified and classified into two types: fine aggregate having a particle size of 5 mm or 10 mm or less and fine aggregate having a particle size smaller than 5 mm or 10 mm. As a boundary, it may be further divided into two classes. According to the present invention, substantially all of the solid content of the aggregate and the cement and the water are initially charged all at once into the stirring vessel of the agitator truck according to the blending design.
%) Will be added later to adjust the slump value.
That is, first, the amount of water to be added is stirred with a little less than the whole amount to prepare hard concrete, and the slump value of the concrete is estimated from the hydraulic pressure of the hydraulic motor. Adjust to slump value. As for the admixture, (1) a predetermined amount of the entire amount is initially charged, (2) a predetermined amount of the total amount is proportionally divided into the amount of water to be injected, and the divided amount is added twice, and (3) a predetermined amount of additional water is added. At the same time, it may be added by any of the following methods, but in terms of concrete quality control, any method should be used. From the viewpoint of simplicity, it is preferable to employ the above method (3). Embodiments of the present invention will be described below. (1) Classify the unwashed riverbed gravel as collected into fine aggregate and coarse aggregate. This classification is performed as follows. The collected riverbed gravel is sent to an 80 mm sieving machine on a belt conveyor, and the passed riverbed gravel is further conveyed on a belt conveyor.
Send to 5mm or 10mm sieving machine and classify. (2) A predetermined amount of cement, fine aggregate, and concrete aggregate of coarse aggregate are dry-blended semi-continuously according to the blend design of the basic blend (1) in Table 1. (3) The dry-blended solids are conveyed by a belt conveyor to the inlet of the stirring vessel of the agitator truck, and at the same time, a predetermined amount of water is charged into the stirring vessel to start rotation of the drum. After first rotating at high speed for about 1 to 3 minutes,
Stirring is continued as normal low-speed rotation. The measurement of the hydraulic pressure of the hydraulic motor is continued, and the slump value of the concrete in the drum is estimated when the hydraulic pressure reaches a steady value. Water-cement ratio of the time of turn-on is 52%, a unit water amount 109 kg / m ^3, the hydraulic motor hydraulic pressure
It was 110-120 kgf / cm ² , and the slump value of the concrete in the drum was estimated to be 4 cm. Slump value of the object of the concrete is 6cm, the slump value is 6cm formulation water-cement ratio is 55%, since it is calculated as a unit water amount 115 kg / m ^3, an additional amount of water 6 kg / m ³ an appropriate amount of The mixture was added together with the admixture and stirring was continued. When the steady value was reached, the hydraulic pressure of the hydraulic motor was 100 to 110 kgf / cm ^2, and it was proved that the slump value of the concrete in the drum was 6 cm as calculated. In an example according to the blend design of the basic blend (2) in Table 2, the water cement ratio at the time of introduction is 79%, and the unit water volume is 119 kg / m ^3.
, And the hydraulic motor hydraulic is 100 ~110kgf / cm ^2,
The slump value of the concrete in the drum was estimated to be 6cm. The slump value of the target concrete is 8 cm, and the composition with this slump value of 8 cm has a water-cement ratio of 89%,
Since the calculated and unit water 133 kg / m ^3, the additional portion of water 14kg / m
³ was added together with an appropriate amount of the admixture, and stirring was continued. Hydraulic pressure of the hydraulic motor at the time of the steady value was 80~90kgf / cm ^2, the slump value of the concrete as calculated in the drum
It has proven to be 8cm. According to the present invention, the properties of concrete using unwashed riverbed and gravel, which is considered to have a large variation in quality as aggregate, can be determined in real time from the measured values of the hydraulic pressure of the hydraulic motor that rotates the agitator truck stirring vessel. By adding an additional amount of water in real time to prepare concrete of the desired quality,
It is possible to control the quality of concrete of all batches to a predetermined quality. Therefore, unwashed riverbed and gravel can be used as aggregate without any worries.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing a relationship between a hydraulic pressure of a hydraulic motor and a slump value of concrete.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Koshizawa 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Shinichi Shimodera 1-2-2 Moto-Akasaka, Minato-ku, Tokyo No. 7 Kashima Construction Co., Ltd. (72) Inventor Shigeru Mutaguchi 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Shinya Ezaki 1-2-2 Moto-Akasaka, Minato-ku, Tokyo No. 7, Kashima Construction Co., Ltd. (56) References JP-A-60-6412 (JP, A) JP-A-62-248607 (JP, A) JP-A-6-305975 (JP, A) 43109 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B28C 7/12 B28C 5/42

Claims (1)

(57) [Claims] [Claim 1] Unwashed riverbed sand and gravel cut to a size of more than 80 mm is used as an aggregate, and a solid content obtained by dry blending the aggregate and a predetermined amount of cement is mixed with water and an admixture. In the agitator truck, the unwashed riverbed sand and gravel are mixed with fine aggregate to prepare concrete by mixing and mixing.
And coarse aggregate, and the fine aggregate and coarse aggregate
Semi-continuous dry blending of solids with cement
Later, this solid content is reduced with less water and admixtures.
The stirring vessel is first rotated at high speed.
After that, continue to stir by rotating at normal low speed, and stir
In real time from the hydraulic pressure of the hydraulic motor that rotates the container
Estimated slump value of concrete in the stirred vessel
To add an amount of water corresponding to
More quality control method for concrete unwashed riverbed gravel, characterized was aggregate to a predetermined slump value slump value slightly larger concrete of the stirring vessel.