JPH0715434B2 - Penetration measurement method for young age concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a method for measuring the amount of penetration of young concrete.

(Prior art) The strength control of concrete at the young age is usually performed based on the elapsed time after placing concrete and the result of the compression test by the strength control specimen. A direct strength control method using concrete is desirable. Therefore, it is necessary to study a strength control method for non-destructively determining the compressive strength of on-site concrete at the young age.

In the case of hardened concrete, various methods have been proposed, standardized, and standardized as non-destructive on-site strength estimation methods for concrete in the prior art.

However, there is no standard or standardized method for extremely low-strength concrete at the young age.

In terms of compressive strength of about 10 kgf / cm ^2, which is low strength, the dynamic and static penetration methods and rotation methods in sounding in the soil field are only standardized and standardized.

The standard penetration test by the dynamic penetration method is a method in which a turret is assembled and a conical tip portion is penetrated deep into the ground to measure the N value. The cone penetration test of the static penetration method is input or heavy. It is a method to measure the penetration resistance value by penetrating the conical tip with a weight, and the simple vane test of the rotary method is to push a vane (resisting blade) with a cross-shaped cross section into the ground.
This is a method in which the resistance moment value is measured by applying extremely slow rotation to the central axis.

(Problems to be solved by the invention) The standard penetration test of the dynamic penetration method is suitable for the determination of the depth and bearing capacity of the support layer, particularly the density of the sand layer, and the measurement of strength change,
Clay is suitable for hard viscosities, but on a large scale,
Not suitable for nondestructive testing.

The cone penetration test of the static penetration method is portable and convenient, but if the cone hits the coarse aggregate, the resistance value becomes large and accuracy cannot be expected.

The rotation type simple vane test is portable and convenient, but it is not suitable for nondestructive testing. If the vane hits the coarse aggregate, the resistance moment becomes large and accuracy cannot be expected.

The present invention has been proposed in view of the problems of the prior art with a simple structure, the penetration of young material concrete that can confirm the strength development of extremely low strength concrete at the young material age from the penetration test results. The point is to provide a method for measuring quantity.

(Means for Solving the Problem) In order to achieve the above-mentioned object, according to the strength determination method for young concrete according to the present invention, a protrusion-shaped mark crosses at the central portion on the tip surface of the penetration testing device. The tip penetrating part provided as above is pressed against the concrete surface of extremely low strength at the young age and a predetermined load is applied, then the penetration tester is removed, and it remains in the depression formed on the concrete surface. The strength of the young concrete is estimated from the relative relationship between the diameter of the depression and the compressive strength by measuring the mark of the protrusion mark as the diameter of the depression.

(Operation) According to the present invention, a projection-like mark is provided on the tip penetration portion of the penetration testing device so as to intersect with the center portion, and the concrete of extremely low strength at the young age is provided through the tip penetration portion. When a predetermined load is applied to the surface and the penetration tester is removed, a depression due to the tip penetration portion is formed on the surface of the young-age concrete, and the mark of the protrusion of the mark remains in the depression.

According to the present invention, it is possible to measure the trace of the protrusion as the diameter of the depression and estimate the strength of the young-age concrete from the relationship between the diameter of the depression and the compressive strength.

(Examples) The present invention will be described below with reference to illustrated examples.

(1) is a cylindrical body of a penetration tester (A) having a load scale (2) on its outer peripheral surface, and a shaft (5) with a handle (4) on a top lid (3) of the cylindrical body (1). Is slidably fitted into the shaft (5) and is fixed to the lower end portion of the shaft (5) which penetrates into the cylindrical body (1), and the bottom cover (7) of the cylindrical body (1). ) And a spring (8) is interposed between
Threaded rod portions provided above and below the connecting member (10) are screwed to the bottom lid (7) and the hemispherical or conical tip penetration portion (9).

A slit (11) is provided on the cylindrical body (1) in the generatrix direction, and a marker (12) attached to an appropriate portion of the spring (8) is seen through the slit (11), and a penetration test device ( By knowing the amount of deformation of the spring (8) in (A), the load applied by the device (A) can be known.

The tip penetrating portion (9) is provided with protrusion-like marks (13) in a cross shape so as to be orthogonal to each other at the central portion of the penetrating portion (9).

Then, the penetration test apparatus (A) is vertically pressed against the surface of the young concrete (B) whose compressive strength is to be estimated, and the handle (4) is attached to the cylindrical body (1) (see FIG. 1). ) Is applied to the bottom lid (7) side to apply a predetermined load, and a plurality of depressions (C) are formed on the surface of the concrete (B). (See FIG. 2) At this time, since the protrusion-like marks (13) of the tip penetration portion (9) are provided in a cross shape, the tip penetration portion (9) penetrates into the concrete (B). A cross-shaped groove is formed up to the range. This is effective as a mark when measuring the amount of penetration when the depth of penetration is shallow and the resulting depression (C) is small or unclear.

When the cross-shaped groove (13 ') is symmetrical with respect to the center of the depression (C) as shown in Fig. 3, the tip penetration portion (9) is formed.
Can be confirmed to have penetrated vertically into the surface of the concrete (B). When the cross-shaped groove (13 ') is asymmetric with respect to the center of the depression (C) as shown in FIG. 4, the tip penetration portion (9) is inclined with respect to the surface of the concrete (B). I understand.

Then, the traces of the cross-shaped groove (13 ') formed on the surface of the concrete (B) were measured several times by a caliper (D) to a unit of 1/20 mm, and the average value was measured. Let the hollow (C) be the diameter. (See FIG. 5) Then, using the compressive strength estimation formula previously obtained from the relationship between the diameter of the depression (C) and the compressive strength of concrete,
The compressive strength of the young concrete (B) is estimated.

The cross-shaped protrusion mark (13) provided on the tip penetration portion (9) is made of a material that does not deform during a penetration test. For example, the protrusion mark is a 0.5 mm diameter piano wire. It is a cross shape.

A hemisphere with a diameter of 100 mm with a cross-shaped mark with a 0.5 mm diameter piano wire on the protrusion is attached as the tip penetration part, and the loading load is 3
The relation between the diameter D of the hollow and the compressive strength δ in the concrete of the mixture targeted for the ECL method is shown below.
Shown in Figure 10.

As a result, the diameter D (mm) of the depression and the compressive strength δ (kgf / cm
There is a strong negative correlation with ² ), and the approximate expression shown in Expression (1) was obtained.

Approximate expression −0.172 × D δ = 26.2 × e (1) Correlation γ = −0.907, number of data: n = 124 In addition, in the above-mentioned embodiment, in order to facilitate measurement of the diameter of the depression (C), the tip The protrusion-like mark (13) in the penetrating portion (9) is provided in a cross shape, but it is shown in FIGS.
As shown in the figure, they may be arranged in a radial pattern or a grid pattern that passes through the central portion.

The tip penetration part (9) is rigid enough not to be deformed during a penetration test, and the tip penetration part does not need to be hemispherical or conical if a mark showing the penetration amount is clearly marked.
It may have a shape as shown in FIG. 16, FIG. 17 and FIG.

(Effects of the Invention) According to the present invention, as described above, a protrusion-shaped mark intersecting at the central portion is provided at the tip penetration portion in the penetration testing device, and the tip penetration portion has a very low-strength concrete surface in the young age group. After applying a predetermined load by pressing to, the penetration test device is removed, thus measuring the mark of the protrusion-like mark left in the recess formed on the concrete surface as the diameter of the recess, and the recess The strength of the young concrete can be confirmed from the relative relationship between the diameter of the concrete and the compressive strength.

Therefore, according to the method of the present invention, since it is possible to directly control the strength of young age concrete, it is easy to perform safety control and process control, and the slip foam method, which requires demolding at the stage when the concrete is extremely low strength, etc. In, it becomes possible to directly control the strength of concrete.

[Brief description of drawings]

1 and 2 are side views showing the steps of an embodiment of the method for measuring the penetration amount of young age concrete according to the present invention, and FIGS. 3 and 4 are attached to the surface of young age concrete. The top view which shows the hollow by a penetration test apparatus, FIG. 5 is a top view which shows the measurement state of the same hollow, FIG. 6 is a partial longitudinal front view of a penetration test apparatus, FIG. 7 is a tip penetration part in the penetration testing apparatus. Fig.8, Fig.8 and Fig.9 are the side view and Fig.10, respectively.
Figure is a diagram showing the relationship between depressions and compressive strength applied to the surface of young-age concrete, Figures 11 to 14 are plan views showing examples of the tip penetration portion, and Figures 15 and 16 are respectively A side view showing another embodiment of the tip penetration portion, as well as a plan view, FIG. 17 and FIG.
The drawings are side views and plan views showing other embodiments of the tip penetrating portions. (A) …… Penetration test device, (B) …… Young age concrete, (C) …… Dimple, (9) …… Tip penetration part, (13)
…… Projective mark, (13 ′) …… Groove on concrete surface.

Claims (1)

[Claims] 1. A tip penetrating portion provided on a tip surface of a penetrating test device so that projecting marks cross each other at a central portion.
After pressing a very low strength concrete surface at a young age and applying a predetermined load, the penetration test device was removed, and the marks of the protruding marks remaining in the depressions formed on the concrete surface were indented. The method for measuring the amount of penetration of young-age concrete is characterized in that the strength of the young-age concrete is estimated from the relative relationship between the diameter of the depression and the compressive strength.