JP2011027568A - Compressive strength control method of coarse aggregate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of calculating compressive strength of coarse aggregate for concrete simply and accurately without measuring it by a compressive strength testing machine, after boring a sample from ore, and coring it or forming a molded body therefrom. <P>SOLUTION: A determination method of compressive strength of coarse aggregate for concrete includes processes for: measuring the compressive strength of a sample cut out beforehand from coarse aggregate ore; crushing the coarse aggregate ore to form coarse aggregate, and measuring a point loading strength of a plurality of specimens on a fraction cut by 1 mm with a particle size of 10-15 mm; generating a correlation expression between a measured value of the compressive strength and a measured value of the point loading strength; and measuring the point loading strength of the coarse aggregate which is a selection object within a range of the fraction, and determining the compressive strength value of the coarse aggregate which is the selection object from the correlation expression. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for managing the compressive strength of coarse aggregate for concrete.

In recent years, the demand for high-strength or ultra-high-strength concrete has increased with the rise of buildings. In ordinary concrete, the strength characteristics such as compressive strength and static elastic modulus of coarse aggregate are almost unquestioned. However, in high-strength or ultra-high-strength concrete, the strength characteristics of coarse aggregate are It has been reported to affect properties.

The compressive strength of the coarse aggregate for concrete is measured by the compressive strength test of the core-free specimen from the raw stone. However, creating a cored specimen from the original rock itself is a reliable method, but it requires a cored process and is not a simple method.

Therefore, it would be extremely beneficial if a method capable of simply and accurately estimating the compressive strength of the coarse aggregate for concrete could be realized.

On the other hand, the spot loading test method for the coarse aggregate for concrete is described in the Geotechnical Society Standard “Spot Loading Test Method for Rock” (JGS 3421-2005). However, it is data by a point loading test method using a molded specimen or a core-free specimen, and the test result of the coarse aggregate for concrete itself is not found. Therefore, the method for estimating the compressive strength of concrete coarse aggregate using this has not yet begun.

Geotechnical Society Standard (JGS 3421-2005)

To realize a method that can easily and accurately calculate the compressive strength of coarse aggregate for concrete without boring from the rough stone, removing the core, or forming it into a compact, and measuring with a compressive strength tester. With the goal.

The object of the present invention is coarse aggregate for concrete, and is an aggregate in which 90% or more of the mass remains on a 5 mm particle size mesh sieve in ordinary civil engineering terms. Therefore, in the production by normal crushing, the particle size distribution varies depending on the type of the crusher and the crushing method, but most of the particle size is 5 mm or more and 30 mm or less.

A method for determining the compressive strength of a coarse aggregate for concrete, the step of measuring the compressive strength with a sample previously cut out from the coarse aggregate raw stone, and crushing the coarse aggregate raw stone to obtain a coarse aggregate, A step of measuring the point load strength of a plurality of specimens in a 1 mm increment of a diameter of 10 mm to 15 mm, a step of creating a correlation formula between the measured value of the compressive strength and the measured value of the point load strength, Measuring the point load strength of the coarse aggregate to be selected in the range of the fraction, and determining the compression strength value of the coarse aggregate to be selected from the correlation equation, and compressing the coarse aggregate for concrete A method for determining strength.

In addition, the coarse loading material to be selected is sampled from the fraction in increments of 1 mm within the particle size range of 10 mm to 15 mm, and the point load strength is measured, and the correlation equation y = 12.445x-22.651 (y: aggregate The compressive strength of the coarse aggregate for concrete is determined from the compressive strength of the concrete.

An ordinary crusher can be used for rough crushing of the rough. Depending on the size of the raw stone, it is also preferable to use two or more pulverization steps. As the pulverizer, a crusher, a hammer mill, a pulverizer, a ball mill, a vertical mill or the like can be used. Here, the particle size of the coarse aggregate is not less than 5 mm and not more than 30 mm.

Coarse aggregate ore may also be commonly used andesite, sandstone, limestone, or quartz rough rock. Table 1 shows the physical properties and chemical components of the coarse aggregate examples.

In the present invention, it is not necessary to remove the core from the rough ore before crushing, the product is a coarse aggregate for concrete itself, and a plurality of coarse aggregates having a predetermined particle size fraction are selected. It measures the loading strength. For example, the measurement object is limited to coarse aggregate having a particle diameter of 10 mm to 15 mm, and a plurality of fractions having a predetermined particle diameter are collected by sieving or the like. For example, the same number of sampling is performed from 10.0 to 15 mm in increments of 1 mm. At that time, samples with cracks or extremely flat shapes are excluded by visual inspection of samples.

A plurality of predetermined samples with good representativeness thus obtained are subjected to a point loading test in accordance with JGS 3421-2005. Specifically, a load measuring device that can measure the loading load and the breaking load P, which includes a loading cone, a loading frame, a hydraulic jack, and the like, is used as a test device.

Next, the specimen is set in a test apparatus, the specimen is supported by a cone from above and below, and the loading point interval (D), loading point distance (L), and specimen width (W) are measured. At this time, the strength test is performed in the loading test only when the conditions of 0.5D <L <1.5D and 0.3W <D <W are satisfied. If the above conditions are not met, replace with another specimen. Next, the point load strength Is is calculated by the following equation.

Is = 0.9P / De ^ 2 Here, De is an equivalent core diameter, which is the diameter of a circle having an area equal to the cross section of the minimum cross-sectional area of the specimen including two loading points. In the present method, De is equal to D.

For example, the average value (N / mm2) of the strength test result by the point loading test for a plurality of the above samples is taken as the x axis, and the compressive strength (N / mm2) by the core-free specimen from the raw stone is measured separately. Plot in the plane coordinates with y-axis.

The average value (N / mm2) of the strength test result by the point loading test and the compressive strength (N / mm2) of the core-extracted specimen from the raw stone showed a good correlation. For example, the correlation coefficient R2 has a correlation of 0.9 or more.

By applying the point loading strength obtained by the above point loading test to the above-mentioned correlation formula for the coarse aggregate obtained from the raw stone of unknown compressive strength, the compressive strength of the coarse aggregate raw stone could be estimated.

Thus, the compressive strength is measured in advance with a sample cut out from the coarse aggregate raw stone, the coarse aggregate raw stone is crushed into coarse aggregate, and the coarse aggregate has a particle size of 10 mm to 15 mm in increments of 1 mm. A step of measuring the point load strength of a plurality of specimens in the image and calculating an average value, and creating a correlation formula between the measured value of the compressive strength and the measured value of the point load strength, Measuring the point load strength of the coarse aggregate in the range of the fraction, determining the compressive strength value of the coarse aggregate to be selected from the correlation equation, and determining the compressive strength of the coarse aggregate for concrete it can.

Specifically, the point load strength of the coarse aggregate to be selected is measured in the range of the particle size of 10 mm to 15 mm, and the correlation equation y = 12.445-22.651 (y: aggregate The compressive strength of the coarse aggregate for concrete which determines the compressive strength of the coarse aggregate can be determined from the compressive strength x: point load strength).

The present invention predicts and manages the compressive strength of the aggregate from the point load strength when using coarse aggregate products, and the compressive strength is measured using a specimen cut out from the raw aggregate stone each time. Even if it is not, there is a strong correlation with this, and using the point load strength measurable from the aggregate sample itself as an index, it is possible to easily and accurately select a coarse aggregate suitable for this, particularly according to the compressive strength of concrete. Construction process management can be easily and accurately performed.

It is a correlation diagram of the average value of the compressive strength of coarse aggregate, and point load strength (particle size fraction 10-15mm). It is a correlation diagram of the average value of the compressive strength of coarse aggregate, and point load strength (particle size fraction 5-20 mm). It is a correlation diagram of the average value of the compressive strength of coarse aggregate, and point load strength (particle size fraction 5-10 mm). It is a correlation diagram of the average value of the compressive strength of coarse aggregate, and point load strength (particle size fraction 15-20mm).

Hereinafter, embodiments of the present invention will be described in detail. This does not limit the invention.

Coarse aggregate used in the quarry was used. After completing the topsoil removal at the quarry, the blasting holes were drilled with a crawler drill and blasted with a smelting oil explosive to obtain crushed stones. Then, it was thrown into the shaft with a power shovel. The rough ore put into the shaft was crushed using a primary crusher in the shaft. After carrying it out of the mine by an underground belt conveyor, it was further crushed with a cone crusher or an impact crusher and adjusted to 5 to 20 mm with a sieve.

The sample was dried by preliminary drying (105 ° C.) followed by vacuum drying with a trap of dry ice-methanol temperature to obtain a constant weight sample.

The dried sample was then subjected to a point loading test.

Table 2 shows the physical properties and chemical components of the coarse aggregate examples used. Coarse aggregates from 6 companies were used.

In the present invention, not a core from a rough ore before crushing, but a molded product, a coarse aggregate for concrete itself, which is a product, was used as a specimen. The coarse aggregate is sampled by 20 or more by the following method.

First, it is limited to coarse aggregate having a particle size of 10 mm to 15 mm. Further, the particle size is fractionated, and four or more samples are screened and collected from at least five particle sizes. For example, 5 from a particle size fraction of 10.0 to 11.0 mm, 5 from a particle size fraction of 11.0 to 12.0 mm, 5 from a particle size fraction of 12.0 to 13.0 mm, Five from the particle size fraction of 13.0 to 14.0 mm, and five from the particle size fraction of 14.0 to 15.0 mm. In consideration of the fact that there are samples to be excluded as a result of the subsequent visual inspection and measurement of the specimen dimensions during the test, it is preferable to sample more.
Subsequently, the sample selected above is visually inspected, and those with cracks or extremely flat shapes are excluded. If the coarse aggregate to be measured has a directionality such as a layered structure, consideration should be given so that the loading axis in the loading test does not deviate in a specific direction.

The samples with good representativeness thus obtained, for example, 25 samples, are subjected to a point load test based on JGS 3421-2005. Specifically, the test device was measured by a load measuring device capable of measuring a loading portion and a breaking load P composed of a loading cone, a loading frame, a hydraulic jack, and the like.

The test method is as follows.
1. 1. Prepare test equipment Set the specimen on the test equipment. Support the specimen with a cone from above and below.
3. The loading point interval (D), the loading point distance (L), and the specimen width (W) are measured.
4. Only when the conditions of 0.5D <L <1.5D and 0.3W <D <W are satisfied, the strength test is performed in the loading test. If the above conditions are not met, replace with another specimen.
(The loading test is performed on four or more specimens from each fraction in increments of 1 mm with a loading point distance of 10 mm to 15 mm. The number of each fraction is the same.)
5. Calculate the point load strength Is using the following formula:

Is = 0.9P / De ^ 2 Here, De is an equivalent core diameter, which is the diameter of a circle having an area equal to the cross section of the minimum cross-sectional area of the specimen including two loading points. In the present method, De is equal to D.

For example, for the 20 samples, the average value (N / mm2) of the strength test results by the point loading test is taken as the x-axis, and the compressive strength (N / mm2) by the cored specimen from the raw stone is measured separately. Plot in the plane coordinates with y-axis. This is illustrated in FIG.

FIG. 1 shows the correlation between the average value (N / mm2) of the strength test result by the point loading test and the compressive strength (N / mm2) of the cored specimen from the raw stone for the six coarse aggregate products. ing. The correlation coefficient R2 was 0.9352, indicating a very good correlation.

By applying the point loading strength obtained by the above point loading test for the coarse aggregate obtained from the raw stone of unknown compressive strength to the above correlation equation of FIG. 1, the compressive strength of the coarse aggregate raw stone can be estimated.

2, 3, and 4, when the 4-point sampling is performed for the fraction having a particle size of 5 to 20 mm and the fraction having a 1 mm increment is provided in the same manner as described above, the fraction having a particle size of 5 to 10 mm is provided. When the process was performed, plots of the respective plots when the fraction having a particle diameter of 15 to 20 mm was provided and processed were shown.

2, 3, and 4, the correlation coefficients were 0.6833, 0.5102, and 0.6306, respectively, and the correlation with the compression strength by the method shown in FIG. 1 was small.

Table 2 shows the data based on each of the above figures as a relationship between the point load strength, the aggregate, and the compressive strength according to the fraction and the rock type.

Thus, the compressive strength is measured in advance with a sample cut out from the coarse aggregate raw stone, the coarse aggregate raw stone is crushed into coarse aggregate, and the coarse aggregate has a particle size of 10 mm to 15 mm in increments of 1 mm. A step of measuring the point load strength of a plurality of specimens in the image and calculating an average value, and creating a correlation formula between the measured value of the compressive strength and the measured value of the point load strength, Measuring the point load strength of the coarse aggregate in the range of the fraction, determining the compressive strength value of the coarse aggregate to be selected from the correlation equation, and determining the compressive strength of the coarse aggregate for concrete it can.

Further, the point loading strength of the coarse aggregate to be selected is measured in the range of the particle size of 10 mm to 15 mm, and the correlation equation y = 12.445-22.651 (y: the compressive strength of the aggregate x: the point loading strength) From the above, the compressive strength of the coarse aggregate for concrete which determines the compressive strength of the coarse aggregate can be determined.

By using the point load strength that is easy to measure, it is possible to determine the compressive strength of the rough aggregate from the coarse aggregate product, and it is possible to easily select the coarse aggregate suitable for this, especially according to the compressive strength of the concrete. Management can be performed easily and accurately.

Claims (2)

A method for determining the compressive strength of coarse aggregate for concrete,
A step of measuring the compressive strength with a sample previously cut from the coarse aggregate rough,
Roughly crushing the coarse aggregate raw stone to obtain a coarse aggregate, measuring the point load strength of a plurality of specimens in a fraction of 1 mm increments of particle size 10 mm to 15 mm;
Creating a correlation between the measured value of the compressive strength and the measured value of the point load strength;
Measuring the point loading strength of the coarse aggregate to be selected in the range of the fraction, and determining the compression strength value of the coarse aggregate to be selected from the correlation equation;
Of determining the compressive strength of concrete coarse aggregate containing Sampling of coarse aggregates to be selected from fractions of 1 mm increments within a particle size range of 10 mm to 15 mm and measuring point load strength, correlation equation y = 12.445x-22.651 (y: compression of aggregates) A method for determining the compressive strength of the coarse aggregate for concrete, which determines the compressive strength of the coarse aggregate from strength x: point load strength).