JP2709041B2 - Method and apparatus for measuring specific gravity of surface dry sand - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the specific gravity (surface dry specific gravity) of fine aggregate (sand) mixed in cement during concrete production in a surface dry and saturated state.

[0002]

2. Description of the Related Art Concrete is manufactured by mixing sand as fine aggregate and gravel (ballast) as coarse aggregate in cement, adding water, and kneading. Concrete that has not yet solidified immediately after production is generally called ready-mixed concrete. The strength of the concrete in which the ready-mixed concrete has solidified after a predetermined period of time is affected by the ratio of water to cement (hereinafter referred to as W / C ratio) at the time of preparing the ready-mixed concrete. The W / C ratio has an optimal value for each type of cement, and the value is specified by the cement manufacturer. Therefore, the specified W
By keeping the / C ratio, concrete of the best quality can be obtained. However, it is generally difficult to keep the above specified W / C ratio at the production site of ready-mixed concrete for the following reasons.

[0003] Fine aggregate (hereinafter simply referred to as sand), which is a main material of concrete, is usually placed outdoors in the form of small hills. Therefore, even after a few days of fine weather, some water remains on the surface of the sand. Especially after the rain, a lot of water is attached. During the production of ready-mixed concrete, the weights of aggregates such as water, cement and sand are measured and mixed at a predetermined weight ratio. Therefore, when using the sand to which such moisture is attached, the measured weight of the sand includes the weight of the water attached to the sand. Therefore, extra water added to the sand is added to the ready-mixed concrete manufactured using sand to which a large amount of water has adhered. As a result, the amount of water increases, the W / C ratio increases, and the specified value cannot be maintained. In the case of using the sand to which water is attached as described above, if the specific gravity of the sand is known, the amount of the attached water can be calculated based on the value of the specific gravity.

[0004] The specific gravity is such that the surface of the sand particles is dry, and a predetermined amount of water is contained in the fine gaps inside the sand particles (surface dry and saturated, usually surface dry) ) (Hereinafter referred to as surface specific gravity). The measuring method of the above table dry specific gravity is JIS A 1109
(Specific gravity of fine aggregate and water absorption test method). In general, it is specified that the surface dry specific gravity of sand for concrete is not less than a predetermined value (for example, 2.5) as a standard of building materials.

[0005]

In the measurement of the specific gravity of the surface dry, it is necessary to first put the sand in a surface dry state. For this purpose, a sample of sand to which water has adhered (hereinafter referred to as wet sand) is evenly dried while gently sending warm air. The determination as to whether or not a predetermined surface dry state has been reached is performed by the following method. Wet sand, still considered to have some water on its surface, is placed in a conical vessel (flow cone) of specified dimensions and gently poke 25 times with a sliver of predetermined dimensions. Next, the flow cone is gently pulled up vertically, and the determination is made based on the holding state of the sand cone at that time. That is, if the sand is too dry, the conical shape cannot be maintained, and the sand is greatly distorted. Conversely, when the drying is insufficient, the conical shape is maintained without any collapse. The above operation is repeated while drying the sample little by little. When the flow cone is pulled up, when the cone-shaped sample breaks for the first time, it is determined that the surface-dry state has been reached. The judgment of such a surface dry state depends on the subjective judgment of the tester, and the judgment accuracy may vary depending on the tester. As described above, the conventional method of measuring the specific gravity of the surface dryness requires a long time and a problem that an appropriate measurement accuracy cannot be obtained, and the problem has been solved.

[0006]

[Means for Solving the Problems]

The method for measuring the specific gravity of a fine aggregate in a dry and saturated state on the surface according to the first aspect of the present invention is a method for measuring the specific gravity of a fine aggregate and water in a _first predetermined volume (L ₁ ). Measuring the weight (Ws) of the first predetermined volume (L ₁₎ by replacing most of the water in the mixture of the fine aggregate to be measured and water with an aqueous solution having a specific gravity different from the specific gravity of water. ) and made the step of measuring the weight of the mixture of the aqueous solution to be measured fine aggregate (W _E), a second of said aqueous solution separated from the mixture of the aqueous solution and the measured fine aggregate determining step of measuring the weight _{(W E)} of a predetermined volume _{(L 2),} and a second predetermined volume of the solution _{(L 2)} and the weight _{(W E)} because of the aqueous solution density ([rho _E) together, the first predetermined volume (L ₁₎ obtained in each _step, fine aggregate and water to be measured Weight of the mixture of (Ws), the weight of the mixture of an aqueous solution having a specific gravity different from the specific gravity of the measured fine aggregate water (W _E), the specific gravity of an aqueous solution having a specific gravity different from the specific gravity of the water ( Using the values of ρ _E ) and the specific gravity of water (ρw),
The formula shown below

[0008]

(Equation 5)

A step of obtaining a specific gravity (ρ).

[0010]

The apparatus for measuring the specific gravity of a fine aggregate in a dry and saturated state on the surface according to the second aspect of the present invention has a first predetermined volume (L ₁ ).
Weight (Ws) of the mixture of the fine aggregate to be measured and water, and a mixture of the fine aggregate to be measured having a first predetermined volume (L ₁ ) and an aqueous solution having a specific gravity different from the specific gravity of water. weight (W _E), and the first predetermined volume (L ₁₎ less than a second predetermined volume (L _2), the weight of the aqueous solution separated from the mixture of the measured fine aggregate and an aqueous solution (W _E ), And a specific gravity (ρ _E ) of the aqueous solution is determined based on a detection output of the weight detector and the second predetermined volume (L ₂ ), and a specific gravity of the determined aqueous solution is determined. (Ρ _E ), the specific gravity of water (ρ _w ) previously determined, the first predetermined volume (L ₁ ), and the weight of the mixture of the fine aggregate to be measured and water (Ws)
And the weight (W _E ) of the mixture of the fine aggregate to be measured and the aqueous solution,

[0012]

(Equation 5)

There is provided an arithmetic means for calculating the specific gravity (ρ) of the fine aggregate to be measured.

[0014]

[0015]

According to the first and second aspects of the invention, the water adhering to the fine aggregate is absorbed by an aqueous solution having a specific gravity different from the specific gravity of the water, and the fine aggregate becomes substantially saturated with surface dryness in the aqueous solution. Acts the same as

[0016]

FIG. 1 is a flow chart of a method for measuring the specific gravity of the surface dry of fine aggregate for concrete according to an embodiment of the present invention. FIG.
Is a side view of the first container 1 used for measurement, and FIG.
It is a side view of the container 2 of FIG. FIG. 4 shows the first and second containers 1
FIG. 4 is a side view showing a state in which a suction device 7 used for setting the water levels of FIGS. Container 1
2 are not limited to the shapes shown in FIG. 2 and FIG. 3, and other shapes may be used.

Hereinafter, a method of measuring the specific gravity of the surface dry of this embodiment will be described with reference to FIGS. 1, 2, 3 and 4. Container 1
For example, a glass wide-mouthed container having a volume of about 1 liter is desirable. Weight of the container 1 (tare) represented by F _1.

[0018] In Step 1 of Figure 1, the total volume of both the vessel 1 filled with water and sand first predetermined volume L _1.
The volume of sand and water should be about the same. Mark 3 first shows the water level slightly higher amount than the first predetermined volume L ₁ to the next putting sand
Pour water close to. After sufficient agitation to remove air bubbles in the sand, as shown in FIG.
Is inserted into the inlet of the container 1, and the plate 9 is brought into contact with the upper end surface of the container 1. The nozzle 8 is connected to the suction device 7 via the hose 10.
Is in communication with The distance from the lower surface 9A of the plate 9 to the tip 8A of the nozzle 8 is constant, and is longer than the perpendicular distance from the upper end surface of the container 1 to the mark 3. As shown in FIG. 4, after the water has been injected to the vicinity of the mark 3 and the suction device 7 is operated, the water in the container 1 is discharged from the nozzle 8
And is discharged through a hose 10 to a tank (not shown) in the suction device 7. The water level is the tip 8 of the nozzle 8
When the pressure drops to A, the nozzle 8 only sucks air and does not suck water, so that the distance from the lower surface 9A of the plate 9 to the water surface 1A becomes constant. Due to this suction, the volume of water in the container 1 is set to the “first predetermined volume L ₁ ”. The accuracy is, for example, 0.001% to 0.0005.
%. Thus, the first container 1 is filled with the _first predetermined volume L1 of water and sand.

In step 2, a first predetermined volume L ₁
To the weighed W ₁ of the container 1 containing water and sand. Determining the weight W _S of the first predetermined volume of water and sand by subtracting the tare F ₁ from the weight W _1. In step 3, the temperature T _1w of the water in the container 1 is measured. Temperature measurement is performed, for example, by placing a temperature sensor in water. Based on the temperature T _1W , the specific gravity ρ _W of the water is obtained by a known “table showing the relationship between the specific gravity of water and the temperature”. The temperature T _1W
, The change in the volume of the container 1 due to the temperature is corrected to obtain an accurate value of the _first predetermined volume L1.

In step 4, most of the water in the container 1 is discarded. Discarding most refers to the degree to which the container is normally tilted and discarded approximately visible water without extraordinary effort or extraordinarily long hours of work. So in this case,
It is not necessary to completely abandon the water; some may be left.

In step 5, after a predetermined “aqueous solution” is poured into the container 1, the mixture is thoroughly stirred to completely remove air bubbles between the sand grains, and then the first device is suctioned using the suction device 7.
To the a predetermined volume L _1. Sufficient stirring means stirring so that the aqueous solution reaches the surface of all the sand grains in the container and air bubbles do not enter the mixture. However, in this case, stirring should not be carried out for an extremely long time so that the aqueous solution penetrates into the micropores (microscopically sized holes or crevices) inside each sand grain. The "aqueous solution" in the present invention refers to an aqueous solution having a specific gravity considerably different from that of water. For example, the specific gravity is 1.5
An aqueous solution before and after, which has little change in specific gravity with time, does not chemically react with sand, and is harmless to the human body and low in viscosity, is a desirable example. For example, an aqueous solution of potassium carbonate adjusted to a specific gravity of about 1.5 is suitable. Conversely, as the “aqueous solution”, an aqueous solution having a lower specific gravity than water can be used. For example, methyl alcohol. In step 6, measuring the weight W ₂ of the container 1 comprising an aqueous solution and sand. The weight W _E of the aqueous solution and the sand of a predetermined volume L ₁ is obtained by subtracting the tare F ₁ from the weight W ₂ . In step 7, the temperature T _1H of the aqueous solution in the container 1 is measured. Based on the temperature T _1H , a change in the volume of the container 1 due to the temperature is corrected to obtain an accurate value of the _first predetermined volume L ₁ .

[0022] In Step 8, the aqueous solution in the container 1 and transferred to the container 2 a second predetermined volume L _2. Step 9
, The weight W _2H of the second predetermined volume L ₂ of the aqueous solution is measured. The weight W _2H is determined by subtracting the container tare F ₂ from the weight of the container 2 containing the aqueous solution. In step 10, the specific gravity ρ _E of the aqueous solution is determined from the _second predetermined volume L ₂ and the weight W _2H .

In step 11, using the measured values obtained in each of the above steps, the values are substituted into the following equation (6) for calculation to determine the specific gravity ρ.

[0024]

(Equation 5)

The measured values and other data necessary for the calculation are listed below. L ₁ : First predetermined volume L ₂ : Second predetermined volume F ₁ : Tare of container 1 F ₂ : Tare of container 2 W ₁ : Weight of container 1 containing water and sand of _first predetermined volume L ₁ W ₂ : Weight of the container 1 containing the first predetermined volume L ₁ of aqueous solution and sand ρ _W : Specific gravity of water in the container 1 ρ _E : Specific gravity of aqueous solution _WS : Weight of sand and water of the predetermined volume L ₁ T _1W : Water temperature of container 1 containing sand and water W _E : Weight of aqueous solution and sand T _1H : Temperature of aqueous solution of container 1 W _2H : Weight of aqueous solution of predetermined volume L ₂

Next, the reason why the surface dry specific gravity (ρ) can be measured in the present invention by the above equation (6) will be described. Assuming that the volume of sand in the surface dry state is S and the specific gravity of water is ρ _W , the weight W _{S of} the first predetermined volume L ₁ of sand and water measured in step 2 of FIG. And 6, the weight W _E of the sand and the aqueous solution having the predetermined volume L ₁ measured by the equations (1) and (2), respectively.

[0027]

(Equation 1)

In step 4, the water adhering to the surface of the wet sand after the water is discarded mixes with the aqueous solution added in step 5, and the concentration of the aqueous solution decreases. Therefore, the obtained specific gravity ρ _E is smaller than the initial specific gravity. Equation (3) is obtained by subtracting equation (1) from equation (2).

[0029]

(Equation 2)

As shown in the equations (3) to (4), the volume S
Ask for.

[0031]

(Equation 3)

By transforming equation (1), the specific gravity ρ is expressed by equation (5).

[0033]

(Equation 4)

By eliminating S from equations (4) and (5), the specific gravity ρ can be determined as shown in equation (6).

[0035]

(Equation 5)

The calculation for determining the specific gravity ρ in step 11 is basically the above equations (1) to (6). In actual measurement, the data used in these formulas (1) to (6), a first predetermined volume L _1, the second predetermined volume L _2, water density [rho _W and an aqueous solution of a specific gravity [rho _E A separate calculation is required to determine the change due to temperature based on each temperature coefficient and correct it. Corrections for the above data are given below. (1) Correction by change of the first temperature of a predetermined volume L _1: (2) a second correction due to a temperature change in the predetermined volume L _2: (3) correction by the temperature of the specific gravity [rho _W Water: (4) Correction of Specific Gravity ρ _E of Aqueous Solution by Temperature: By using the values corrected in the above items (1) to (4) for the numerical values of the above equations (1) to (6), FIG.
Even when the temperature changes in each step shown in (1), the correct surface dry specific gravity ρ can be obtained without being affected by the temperature change. However, in the normal room temperature range, i.
When the temperature hardly changes during the measurement in the range of about ° C, or when a very high measurement accuracy is not required, the above-described correction based on the temperature can be omitted.

FIG. 5 is a block diagram of an embodiment of an apparatus for executing the method for measuring the surface dry specific gravity of fine aggregate according to the present invention. In the figure, a weight detector 12 is a device for measuring the weight of the container 1 or 2, and is constituted by, for example, a weigh scale using a strain gauge. The temperature detector 13 has a temperature sensor 14 and measures the water temperature by putting the temperature sensor 14 in water. Data detected by the weight detector 12 and the temperature detector 13 are recorded in the memory 17 via the CPU 15. The memory 16 stores the above equations (1) to (6). Further, the memory 16 has a first predetermined volume L ₁ , a second predetermined volume L ₂ , a tare F ₁ and F ₂ of each of the containers 1 and 2, a table showing a relationship between a temperature and a specific gravity of water, the container 1 and The expansion count data of 2 is stored in memory.

In the CPU 15, the calculations based on the above equations (1) to (6) are performed using the data in the memory 17. Then, the specific gravity ρ of the surface dryness of the calculation result is obtained. The obtained surface dry specific gravity ρ is displayed on the display device 19.

FIG. 6 is a plan view showing an operation portion of the input device 18. Data such as weight and temperature is input by the input device 18. In the figure, switches 21 to 30 are constituted by push button switches or touch switches. On the surface of each switch, each data measured in the process of measuring the specific gravity of the surface dry according to the present invention is written by its symbol. The data measured by operating a switch corresponding to the data measured in each step of the flowchart of FIG. 1 is stored in a predetermined address of the memory 16. When the switch 30 is operated after operating all the data by operating the switches 21 to 29, the CPU 15 calculates the expressions (1) to (6) and obtains the specific gravity ρ.

In the above embodiment, the measurement of the surface dry specific gravity (ρ) of wet sand to which water has adhered has been described. However, a liquid other than water, for example, sand to which oil has adhered or another member, for example,
It is also possible to measure the surface dry specific gravity of a metal piece, a fibrous member, or the like. In this case, instead of the above-mentioned "aqueous solution having a specific gravity different from the specific gravity of water", another liquid in which the oil is easily dissolved and whose specific gravity is different from the specific gravity of the oil is used.

[0041]

【The invention's effect】

According to the first and second aspects of the present invention, wet sand is placed in an aqueous solution having a specific gravity different from that of water, and water adhering to the sand is absorbed by the aqueous solution. The weight of the resulting aqueous solution for a first predetermined volume of sand _{(L 1) (W E)} , the weight of the specific gravity of the aqueous solution (ρ _E), a first predetermined volume of sand and water (L ₁₎ ( Ws) and the specific gravity of water (ρ _w ), the surface dry specific gravity can be measured without making the wet sand surface dry by performing the calculation shown in Expression (6).

[Brief description of the drawings]

FIG. 1 is a flowchart of a method for measuring a specific gravity of a surface dry according to the present invention.

FIG. 2 is a side view of the first container 1.

FIG. 3 is a side view of the second container 2.

FIG. 4 is a side view showing a state where the suction device is attached to the first container 1.

FIG. 5 is a block diagram of an apparatus for measuring surface dry specific gravity according to the present invention.

FIG. 6 is a plan view of an input device of the measuring device of FIG. 5;

Claims (2)

(57) [Claims] 1. A step of measuring a weight (W _S ) of a mixture of the fine aggregate to be measured and water, which is made to a _first predetermined volume (L ₁ ); Most of the water in the mixture is replaced with an aqueous solution having a specific gravity different from that of water,
Said step of measuring the weight of the mixture of the aqueous solution to be measured fine aggregate (W _E) of a predetermined volume (L _1), said separated from mixture of the aqueous solution to be measured fine aggregate the Measuring a weight of a _second predetermined volume (L ₂ ) of the aqueous solution; and a second predetermined volume (L ₂ ) of the aqueous solution
And the weight thereof to determine the specific gravity (ρ _E ) of the aqueous solution, and the first predetermined volume obtained in each of the steps.
(L ₁ ), the weight of the mixture of the fine aggregate to be measured and water (W _S ), the weight of the mixture of the fine aggregate to be measured and an aqueous solution having a specific gravity different from the specific gravity of water (W _E ), Using the values of the specific gravity (ρ _E ) of the aqueous solution having a specific gravity different from the specific gravity of water and the specific gravity of water (ρ _W ), the following equation is obtained. Determining the specific gravity (ρ) of the fine aggregate to be measured by the method described above. Wherein the weight of the first predetermined volume (L ₁₎ mixture of fine aggregate and water under measurement (W _S), a first predetermined volume (L ₁₎
Wherein the measured fine aggregate, the weight of the mixture of an aqueous solution of a different specific gravity and the specific gravity of water (W _E), and a first small second predetermined volume than a predetermined volume (L ₁₎ (L ₂₎ A weight detector for measuring the weight of the aqueous solution separated from the mixture of the fine aggregate to be measured and the aqueous solution; and a detection output of the weight detector and the second predetermined volume (L ₂ ). together determine the specific gravity ([rho _E) of the aqueous solution Te, the obtained aqueous solution of a specific gravity ([rho _E), the previously obtained water density
(ρ _W ), the first predetermined volume (L ₁ ), the weight of the mixture of the fine aggregate to be measured and water (W _S ), and the weight of the mixture of the fine aggregate to be measured and the aqueous solution (W _{Using E} ), the following equation: A measuring device for calculating the specific gravity (ρ) of the fine aggregate to be measured by the following method.