KR102511126B1 - Estimation method of cement amount of concrete using hydrochloric acid dissolution heat - Google Patents

Abstract

The present invention discloses a method for estimating the unit cement amount of concrete using hydrochloric acid dissolution heat.
According to the method for estimating the unit cement amount of concrete using the heat of dissolution of hydrochloric acid according to the present invention, the temperature difference (ΔΤ) between the diluted solution obtained by diluting the crushed concrete with water and the reaction solution mixed with the diluted solution and the hydrochloric acid solution is It is characterized in that it is proportional to the unit cement amount, and according to this, it is possible to estimate the unit cement amount of hardened concrete using the hydrochloric acid melting heat method, so that the unit cement amount can be estimated at the time of mixing through the temperature difference.

Description

Estimation method of cement amount of concrete using hydrochloric acid dissolution heat}

The present invention relates to a method for estimating the unit cement amount of concrete using hydrochloric acid dissolution heat, and more particularly, as a method for confirming the unit cement amount of hardened concrete,

It relates to a method for estimating the unit cement amount of concrete using the heat of hydrochloric acid dissolution, which can estimate the unit cement amount of hardened concrete using the heat of hydrochloric acid dissolution method, and thus estimate the unit cement amount when mixing through the temperature difference.

Setting the unit cement amount in the mixing design of concrete is a very important factor in terms of economic feasibility, ensuring durability of concrete, and safety such as material separation and strength reduction.

However, recently, in Korea, there are concerns about the quality of ready-mixed concrete due to problems such as the substitution of more than an appropriate amount of admixture instead of less cement than the supply contract, and there are various cases in which defective ready-mixed concrete that does not meet the required quality is brought to the construction site. The importance of quality control of ready-mixed concrete is greatly highlighted due to poor construction of concrete, such as being reported through the media.

In addition, it is expected that the imbalance in the supply and demand of concrete aggregates will continue to be raised in the future, and the demand for high quality of concrete structures is also continuously increasing. In order to do this, the need to strengthen the quality control of ready-mixed concrete is emerging.

On the other hand, the quality control of ready-mixed concrete cast at construction production sites so far has evaluated the slump, air volume, and chloride ion amount of unhardened concrete in accordance with KS F 4009, and then used a standard curing specimen for concrete at the strength management age specified in the specification. The quality assurance is determined by measuring the compressive strength.

The method for determining the strength of concrete is as shown in Table 1 Strength confirmation method of hardened concrete and Table 2 Principles and characteristics of measuring early strength and unit cement amount of unhardened concrete. A variety of strength measurement methods, including ultrasonic measurement and non-destructive testing using integrated temperature, are used in practice, but methods for confirming the unit cement amount of hardened concrete have hardly been reported.

Strength test type Test Methods Schmidt hammer method Estimating the strength of concrete by the degree of repulsion when hitting the surface Resonance method Strength is measured as a dynamic measurement value using the period of natural vibration between objects sonic law Intensity is estimated by the speed of the sound wave compound method Estimation of strength by combining the repulsion method and the speed of sound method drawing method Measure the strength of bolts or steel plates buried in concrete core picking The concrete part to be tested is collected using a core drill and re-tested such as strength test penetration resistance method A pin is driven into concrete using gunpowder or a spring to evaluate its strength from its depth. sonography Strength measurement at the speed of ultrasonic waves passing through the concrete

Experiment method principle characteristic hydrochloric acid dissolution method Determination of heat of dissolution when hydrochloric acid is applied to fresh mortar sieved from concrete This is not possible if the lime composition is agglomerated and the heat is measured in an insulated container. back titration Sodium hydroxide titer in cement as a function of hydrochloric acid relative to that in proportion to the amount of cement in mortar leached from concrete Determined by preliminary experiment and requires correction curve simple back titration Although it is the above method, the amount of cement is simply inspected by the measuring device. Mortar is taken from concrete and analyzed by color change performed in 15 minutes with a precision of 5% for comparison. Auto-cleaning tester method CaCO ₂ has no effect, but dissolves only cement and detects chelate compounds in the mixture Experiments carried out in the case of fragments or limestone containing concrete samples hydrometer The specific gravity of the mortar suspension and the added water is proportional to the amount of mortar cement leached from the fresh concrete. Measured preliminary experiments require calibration curves and are not possible when fine powder is added. color difference method By colorizing the unhardened concrete sample according to the added water, the color difference was calculated using the calibration curve of the amount of cement and the fertilizer. The experiment is simple, but requires expensive equipment heat closure Prediction of cement composition through sieving by heating and crushing mortar samples from unhardened concrete Simple practical equipment and method Formulation analyzer method Calculation of Cement Amount for Cement Composition in Washed Slurry Direct measurement of concrete possible

Therefore, the technical problem to be solved by the present invention is a method of confirming the unit cement amount of hardened concrete in an actual structure, and it is possible to estimate the unit cement amount of hardened concrete using the hydrochloric acid melting heat method, so that the unit cement when mixing through the temperature difference It is to provide a method for estimating the unit cement amount of hardened concrete using hydrochloric acid dissolution heat that can estimate the amount.

The present invention, in order to solve the above-mentioned technical problem, the temperature difference (ΔΤ) between the diluted solution of crushed concrete diluted with water and the reaction solution mixed with the diluted solution and hydrochloric acid solution is the amount of unit cement used in the concrete and It provides a method for estimating the unit cement amount of concrete using hydrochloric acid dissolution heat, characterized in that it is proportional.

According to another embodiment of the present invention, the temperature difference (ΔΤ) between the dilution solution and the reaction solution mixed with the hydrochloric acid solution may be according to Equation 1.

<Equation 1>

△Τ=Τ-(0.8Τc+0.2Τ _H )

(ΔΤ: temperature difference (℃), Τ: maximum reaction temperature (℃), Τc: temperature of concrete diluent before reaction (℃), Τ _H : temperature of hydrochloric acid before reaction (℃))

According to another embodiment of the present invention, the maximum reaction temperature may be formed within 10 minutes after initiation of the reaction.

According to another embodiment of the present invention, the average particle size of the crushed concrete may be 10 mm or less.

According to another embodiment of the present invention, the amount of SP agent according to the amount of unit cement before hardening of the concrete may be adjustable.

According to another embodiment of the present invention, the unit volume mass according to the unit cement amount before hardening of the concrete may be unchanged.

According to another embodiment of the present invention, the compressive strength of the concrete may increase as the amount of unit cement used increases.

Therefore, according to the method for estimating the unit cement amount of concrete using the heat of hydrochloric acid dissolution according to the present invention, as a method of confirming the unit cement amount of hardened concrete, it is possible to estimate the unit cement amount of hardened concrete by utilizing the hydrochloric acid heat of dissolution method, and thus the temperature difference Through this, it exerts the effect of estimating the amount of unit cement when mixing.

1 is a graph showing the slump and SP amount according to the unit cement amount of unhardened concrete according to the present invention,
Figure 2 is a graph showing the amount of air and unit volume mass according to the unit cement amount of unhardened concrete according to the present invention,
Figure 3 is a graph showing the compressive strength according to the unit cement amount of the compressive strength according to the unit cement amount of the hardened concrete according to the present invention,
4 is a graph showing the temperature of concrete and mortar according to the change in unit cement amount according to the present invention,
5 is a graph showing the correlation between the temperature difference and unit cement amount of hardened concrete according to the present invention.

Hereinafter, the present invention will be described in more detail.

In order to help the understanding of the present invention, examples are described in detail, but the following examples are only illustrative of the contents of the present invention, and the scope of the present invention is not limited to the following examples.

The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

In addition, although the present invention describes specific parts in detail, it will be clear to those skilled in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. .

Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

1 is a graph showing slump and SP amount according to unit cement amount of unhardened concrete according to the present invention, and FIG. 2 is a graph showing air volume and unit volume mass according to unit cement amount of unhardened concrete according to the present invention. , Figure 3 is a graph showing the compressive strength according to the unit cement amount according to the unit cement amount of hardened concrete according to the present invention, Figure 4 shows the temperature of concrete and mortar according to the change in unit cement amount according to the present invention It is a graph, and FIG. 5 is a graph showing the correlation between the temperature difference and unit cement amount of hardened concrete according to the present invention.

According to the method for estimating the unit cement amount of concrete using the heat of dissolution of hydrochloric acid according to the present invention, the temperature difference (ΔΤ) between the diluted solution obtained by diluting the crushed concrete with water and the reaction solution mixed with the diluted solution and the hydrochloric acid solution is It is characterized in that it is proportional to the unit cement amount.

Here, the concrete is a commonly used concrete in which cement, water, sand, aggregate, etc. are mixed and used, and the aggregate may include coarse aggregate and fine aggregate.

Ordinary Portland cement can be used as the cement, and its properties are shown in Table 3 below.

density
(g/cm ³ ) fineness
(cm ² /g) stability
(%) Condensation time (minutes) Compressive strength (MPa) first resolution closing 3 days 7 days 28 days 3.10 3520 0.5 305 340 31.4 39.9 53.0

In addition, the aggregate must be of constant quality and uniform quality when manufacturing aggregate concrete, and its characteristics can be shown in Tables 4 and 5 below.

division density
(g/cm ³ ) assembly rate absorption rate 0.08mm sieve
Passing amount (%) Standing decision performance rate (%) Stone Coarse Aggregate 2.63 6.20 0.82 - 56.5

division density
(g/cm ³ ) assembly rate absorption rate 0.08mm sieve
Passing amount (%) Standing decision performance rate (%) quarry fine aggregate 2.62 2.75 1.31 4.60 -

In addition, the hydrochloric acid solution is a mixture of hydrochloric acid and water, and may have characteristics shown in Table 6 below.

division density
(g/cm ³ ) vapor specific gravity Molecular Weight Hydrochloric acid 1.19 1.3 36.5

Meanwhile, the temperature difference (ΔΤ) between the diluted solution and the reaction solution mixed with the hydrochloric acid solution may be according to Equation 1.

<Equation 1>

△Τ=Τ-(0.8Τc+0.2Τ _H )

(ΔΤ: temperature difference (℃), Τ: maximum reaction temperature (℃), Τc: temperature of concrete diluent before reaction (℃), Τ _H : temperature of hydrochloric acid before reaction (℃))

Τ is the maximum reaction temperature (℃), which means the highest temperature among the temperatures resulting from the dilution solution and the hydrochloric acid solution being mixed, and the active ingredient of the dilution solution and the hydrochloric acid chemically reacting and generating heat, which is formed within 10 minutes after the start of the reaction. It has a characteristic.

Preferably, the maximum reaction temperature (° C.) can be reached in about 2 minutes after the reaction starts.

The Τc is the temperature of the concrete dilution solution before reaction (℃).

Τ _H is the measured temperature of the hydrochloric acid solution before the reaction.

In addition, the average particle size at which the concrete is crushed may be 10 mm or less. If it exceeds 10 mm, it is difficult for the active ingredients in the particles to participate in the chemical reaction with hydrochloric acid, which may cause deviations in the measurement of the maximum reaction temperature, and the minimum particle size The smaller the is, the more advantageous it is to measure the temperature. However, since the uniformity of the concrete mixing process is not so high, there is almost no deviation in temperature measurement when it is less than 1 mm, so 1 mm or more is preferable.

In addition, the amount of SP agent according to the amount of unit cement before hardening of the concrete can be adjusted, so that the amount of SP agent used can be reduced. It can be adjusted by reducing the amount.

The SP agent is an abbreviation of Super Plasticizer and is a type of water reducing agent. It effectively disperses cement by strengthening the function of a general water reducing agent, and is used at a high addition rate without adverse effects such as delay in setting, excessive air entrainment, and reduction in strength. It refers to an admixture that can drastically reduce the unit quantity.

In addition, the unit volume mass according to the unit cement amount before hardening of the concrete may be unchanged, and the air amount of the unit cement amount before hardening tends to increase or decrease slightly as the unit cement amount increases, which is due to the increase in the unit cement amount It seems to be due to the improvement of fillability, and there may be little change in unit volume mass.

On the other hand, the compressive strength of the concrete may increase as the amount of unit cement used increases, which seems to be due to the filling effect and the decrease in the amount of air as the unit cement amount increases.

Example

As shown in Table 7 below, experimental examples according to the present invention were carried out.

Mixing factors of concrete were W/C (water/cement weight ratio) 45%, target slump 150±25mm, target air volume 4.5±1.5%, unit cement volume (kg/m ³ ) were divided into 6 groups, 356 and 366, respectively. , 378, 389, 400 and 411, and the test items are unhardened concrete and hardened concrete. For unhardened concrete, slump, slump flow, air volume, and unit volume mass were measured as four items, respectively, and for hardened concrete, compressive strength was measured as two items, respectively, and temperature was measured by the hydrochloric acid dissolution method. The compressive strength of 7 days and 28 days was measured, specimens were prepared, and the hydrochloric acid dissolution heat method was performed using the specimens cured after curing in water. In addition, as shown in Table 8, concrete contains cement, sand, and gravel .

division experimental factor experimental factor level of experimentation mixing factor W/C(%) One 45 Target slump (mm) 150±25 Target air volume (%) One 4.5±1.5 Unit cement amount (kg/m ³ ) 6 356 366
378 389
400 411 Experiment item fresh concrete 4 slump, slump flow
air volume, unit volume mass hardened concrete 2 Compressive strength (3, 7, 28 days)
Hydrochloric acid dissolving heat method (28 days)

W/B
(%) Unit cement amount
(kg/㎥) unit
quantity
(kg/㎥) S/a
(%) SP/C
(%) AE/C
(%) Unit mass mixing (kg/㎥) Unit volume mixing (ℓ/㎥) C S G C S G 45 356 160 46 0.22 0.023 356 832 894 113 327 355 366 165 0.19 0.023 367 787 917 116 310 364 378 170 0.15 0.023 378 777 905 120 306 359 389 175 0.15 0.017 389 767 893 123 302 355 400 180 0.10 0.012 400 757 882 127 298 350 411 185 0.10 0.023 411 747 870 131 294 345 * S/a: Fine aggregate ratio C: Cement, S: Sand, G: Gravel

The hydrochloric acid dissolving heat method is specifically, (1) preparing a 200 g sample crushed to a maximum concrete size of 3 mm or less, and (2) putting the 200 g sample of concrete in an Erlenmeyer flask and mixing it with 800 ml of water prepared in advance. Put it in an insulated container, (4) measure the temperature of the mixture with a thermocouple thermometer, (5) measure the temperature of 100ml hydrochloric acid weighed in advance, (6) mix the mixture and hydrochloric acid uniformly for about 30 seconds and put it in an insulated container , (7) The maximum temperature of the reaction heat generated by the chemical reaction between the mixture and hydrochloric acid was measured by interlocking the thermocouple and the data logger, and (8) the temperature difference was obtained (ΔΤ=Τ-(0.8Τc+0.2Τ _H ) )

Experimental Example 1 Slump and SP amount according to unit cement amount of unhardened concrete

The slump test for evaluating the fluidity of unhardened concrete is performed in accordance with KS F 2402 (Slump test method for unhardened concrete). After aligning the upper surface of the filled concrete with the top of the slump cone, lift the slump cone vertically, and After the movement of the stop, measure the diameter thought to be the maximum spread and the diameter in the orthogonal direction.

1 is a graph showing the slump and SP amount according to the unit cement amount of unhardened concrete according to the present invention. Referring to this, as the unit cement amount increases, the slump slightly increases, but the SP amount decreases. As the amount of unit cement increases, it is judged that the fluidity increased because the water inside the concrete increased in the same W/C.

Experimental Example 2 Amount of air and unit volume mass according to unit cement amount of unhardened concrete

The air content test is measured in accordance with KS F 2421 (Air content test method by the pressure method of unhardened concrete). In this case, it was judged to be different from the target mixture and discarded without molding the specimen, and the unit volume mass test was measured in accordance with the regulations of KS F 2409. Evenly compact 25 times with a rod, hit the outside of the container with a rubber mallet 10 to 15 times until no air bubbles are visible on the concrete surface, put samples up to 2/3 of the container, compact the same number of times as before, and finally Add it until it overflows and compact it the same number of times as the previous time. After that, measure the mass inside the container after leveling the surface.

Figure 2 is a graph showing the amount of air and unit volume mass according to the amount of unit cement of unhardened concrete according to the present invention. Referring to this, the amount of air tends to increase or decrease slightly as the amount of unit cement increases. It was judged to be due to the improvement in filling ability, and it was confirmed that there was little change in unit volume mass.

Experimental Example 3 of hardened concrete Compressive strength according to unit cement amount

The specimen compressive strength measurement experiment was measured with UTM (Universal Testing Machine) according to the regulations of KS F 2405 (Concrete compressive strength test method). Arrange the central axis so that it coincides with the center of the platen within an error of 1% of the diameter, and the platen of the tester and the end face of the specimen are directly brought into close contact (no cushioning material is inserted between them), and the same speed so as not to impact the specimen. After the load is applied and the specimen starts to deform rapidly, stop adjusting the speed of applying the load and continue to apply the load, read the maximum load indicated by the tester to three significant digits until the specimen is destroyed, and calculate save by using

<Compressive strength formula>

where f _c : compressive strength (MPa), P : maximum load (N), n : circumferential rate (π), d : diameter of specimen (mm)

3 is a cured concrete according to the present invention Compressive strength according to unit cement amount This is a graph showing the compressive strength according to unit cement amount. Referring to this graph, the compressive strength increased ^as the unit cement amount increased. ³ The compressive strength of concrete was about 22% higher. It is believed that this is due to the filling effect and the decrease in air volume as the amount of unit cement increases.

Experimental Example 4 Temperature history compressive strength according to elapsed time of unit cement amount of hardened concrete

Put a mixture of 200 g of concrete sample crushed to a maximum concrete size of 3 mm or less and 800 ml of water into an insulated container, add 100 ml of hydrochloric acid to it, mix it uniformly for about 30 seconds, put it into an insulated container, and heat the reaction The temperature of is measured by linking the thermocouple and the data logger.

4 is a graph showing the temperature of concrete and mortar according to the change in the unit cement amount according to the present invention. Referring to this, it was confirmed that the reaction temperature of most concrete samples increased rapidly after 60 seconds, After that, it was found that the temperature increased and decreased slightly. In addition, the highest reaction temperature appeared after 90 seconds.

Experimental Example 5 Cured Concrete Correlation between temperature difference and unit cement amount

Equation using the maximum reaction temperature measured in Experimental Example 4 △Τ=Τ-(0.8Τc+0.2Τ _H ) (△Τ: temperature difference (℃), Τ: maximum reaction temperature (℃), Τc: concrete dilution temperature before reaction (℃), Τ _H : hydrochloric acid temperature before reaction ( ℃)) was used to measure the temperature difference. A correlation was derived according to the amount of unit cement.

5 is hardened concrete according to the present invention It is a graph showing the correlation between temperature difference and unit cement amount. Referring to this, the unit cement amount can be estimated when checking an arbitrary temperature difference. For example, in the case of a difference of 12 ° C as shown in FIG. /m ³ , in the case of a difference of 14℃, the unit cement amount can be estimated as 408 kg/m ³ .

Therefore, as described above, the present invention can estimate the unit cement amount by checking the increase in the heat of dissolution of hydrochloric acid in the concrete sample.

Claims (7)

The temperature difference (ΔΤ) between the dilution solution obtained by diluting the crushed concrete with water and the reaction solution obtained by mixing the dilution solution and the hydrochloric acid solution is proportional to the amount of unit cement used in the concrete,
As the amount of unit cement before hardening of the concrete increases, the amount of water in the concrete increases in the same W / C, so the fluidity increases and the amount of SP decreases,
The unit volume mass according to the unit cement amount before hardening of the concrete is unchanged,
As the amount of unit cement increases, the amount of air increases and decreases due to the improvement in the filling property according to the increase in the amount of unit cement,
A method for estimating the unit cement amount of concrete using hydrochloric acid dissolution heat, characterized in that the unit cement amount is estimated according to Equation 2 below.
<Equation 2>
y=82.27+23.31x
(y: unit cement amount, x: temperature difference between the diluted solution and the reaction solution mixed with the hydrochloric acid solution)
According to claim 1,
The temperature difference (ΔΤ) between the diluted solution and the reaction solution mixed with the hydrochloric acid solution is a method for estimating the unit cement amount of concrete using hydrochloric acid dissolution heat, characterized in that according to Equation 1.
<Equation 1>
△Τ=Τ-(0.8Τc+0.2Τ _H )
(ΔΤ: temperature difference (℃), Τ: maximum reaction temperature (℃), Τc: temperature of concrete diluent before reaction (℃), Τ _H : temperature of hydrochloric acid before reaction (℃))
According to claim 2,
The method of estimating the unit cement amount of concrete using hydrochloric acid dissolution heat, characterized in that the maximum reaction temperature is formed within 10 minutes after the start of the reaction.
According to claim 1,
Method for estimating unit cement amount of concrete using hydrochloric acid dissolution heat, characterized in that the average particle size of the concrete crushed is 10 mm or less.
delete delete According to claim 1,
The method of estimating the unit cement amount of concrete using hydrochloric acid melting heat, characterized in that the compressive strength of the concrete increases as the amount of unit cement used increases.

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