JP4861610B2 - Method for producing concrete using recycled aggregate - Google Patents

Description

The present invention relates to a method for producing concrete using recycled aggregate in the concrete field.

The use of recycled aggregate for asphalt aggregate on paved roads is well known and implemented,
Research and development has also been conducted on the recycling of waste concrete into concrete, such as by demolishing buildings, and the reuse rate is increasing dramatically.

However, the reuse of concrete waste materials such as building demolition to concrete is mainly for roadbed materials and backfill materials, and natural aggregates such as strength are used for building columns, beams and slabs. Because it is inferior to what we had, special processing had to be performed, and there was no merit in terms of quality and price, and it was not implemented.

In particular, recycled aggregates produced by low-level processing using concrete waste material after being pulverized by a pulverizer are in a state of little use other than recycled roadbed material due to poor quality. However, low-level regeneration has many advantages such as saving energy compared to high-grade recycled aggregates such as heated grits, and reducing the environmental burden and improving the reuse rate of waste concrete.
Then, as a result of conducting a prior patent search on the reuse of concrete waste,
No. 20154, Japanese Patent Application Laid-Open No. 2004-41859, and the like were searched.

The above Japanese Patent Laid-Open No. 2002-201554 breaks a concrete lump discharged along with the dismantling of a concrete structure, and puts filled concrete containing coarse aggregate among a large number of concrete lumps thus obtained. This increases the compressive strength of the entire recycled concrete.

Japanese Laid-Open Patent Publication No. 2004-41859 discloses a coarse aggregate and a fine aggregate separated by a crushing action and a grinding action of a conical-type ball mill by putting concrete waste into a conical-type ball mill containing spherical grinding members. In this case, the deposits adhering to the material are peeled off to regenerate the coarse aggregate and fine aggregate from the concrete waste.
JP 2002-20154 A JP 2004-41859 A

However, even though the former can be used for a specific concrete structure, it cannot be applied to a general concrete structure, and the latter requires a special crushing device such as a conical ball mill.

Therefore, an object of the present invention is to improve the quality of recycled concrete within the scope of conventional concrete manufacturing technology without requiring any special equipment for the waste concrete material.

In view of the above-mentioned points, the present invention mixes recycled aggregates of cement and concrete waste, water, and raw materials for admixture, and stirs and kneads these with a mixer to produce concrete. A method for producing concrete using recycled aggregates to be produced, comprising mixing recycled aggregates of cement and concrete waste with low-grade aggregate, water, and raw materials of admixture and mixing the recycled aggregates in the mixer. In order to peel off old powder adhering to the surface, a regenerated bone characterized by improving the strength of concrete by applying vibration to the raw material for a predetermined time with a rod-shaped vibrator to improve adhesion of mortar The manufacturing method of the concrete by a material is provided.

In addition, the concrete made from recycled aggregate is characterized in that the raw material is vibrated for 30 to 180 seconds in order to peel off the old powder adhering to the surface of the recycled aggregate during the mixing of the raw material in the mixer. The manufacturing method of this is provided.

Furthermore, the concrete made from recycled aggregate is characterized in that the raw material is vibrated for 30 to 180 seconds in order to peel off the old powder adhering to the surface of the recycled aggregate during the mixing of the raw material in the mixer. The manufacturing method of this is provided.

Furthermore, recycled fine aggregate of cement and concrete waste is put into a mixer and kneaded for 30 seconds, mixed with water and admixture for 60 seconds, recycled coarse aggregate is added and kneaded for 60 seconds, The present invention provides a method for producing concrete using recycled aggregate, which is characterized by imparting vibration to the raw material .

The method for producing concrete by using the recycled aggregate according to the present invention comprises mixing cement, recycled concrete aggregate, water, and raw materials of admixture, and stirring and kneading them with a mixer to produce concrete. This is a manufacturing method, in which cement and concrete waste low-grade aggregate recycled aggregate, water, and raw materials of admixture are mixed and old powder adhering to the surface of the recycled aggregate is mixed in the mixer. In order to exfoliate, the raw material is vibrated with a rod-shaped vibrator for a predetermined time to improve the adhesion of the mortar and improve the strength of the concrete. Therefore, the quality of recycled concrete can be improved within the scope of conventional concrete manufacturing technology without the need for special equipment, and mortar can be attached to recycled aggregate. There was improved, compressive strength of the concrete can be sufficiently exhibited.

And even if the recycled aggregate of concrete waste is a low-level processed aggregate, in order to peel off the old powder adhering to the surface of the recycled aggregate, the recycled aggregate is given a vibration for a predetermined time. The adhesion of mortar to the surface is improved, and the compressive strength of the concrete can be sufficiently developed.

Also, during the mixing of the raw material and mixing with the mixer, in order to peel off the old powder adhering to the surface of the recycled aggregate, the raw material is vibrated for 30 to 180 seconds to improve the adhesion of the mortar. By improving the strength, it is possible to obtain a sufficient effect as described above even with a low-grade aggregate of concrete waste.

Furthermore, recycled fine aggregates of cement and concrete waste are put into a mixer and kneaded for 30 seconds, mixed with water and admixture for 60 seconds, recycled coarse aggregate is added and kneaded for 60 seconds, By giving vibration to the raw material, a moderately slumped material can be obtained even if it is a low-grade aggregate of concrete waste, and it can be constructed in the same manner as before.

The best mode of the invention

The method for producing concrete by using the recycled aggregate according to the present invention comprises mixing cement, recycled concrete aggregate, water, and raw materials of admixture, and stirring and kneading them with a mixer to produce concrete. This is a manufacturing method, in which cement and concrete waste low-grade aggregate recycled aggregate, water, and raw materials of admixture are mixed and old powder adhering to the surface of the recycled aggregate is mixed in the mixer. In order to exfoliate, the raw material is vibrated over a predetermined time with a rod-shaped vibrator to improve adhesion of the mortar to improve the strength of the concrete.

As the concrete waste material, waste material or the like obtained by dismantling a concrete building can be used, and the recycled fine aggregate and recycled coarse aggregate can be used for the entire particle size obtained by crushing the lump of the concrete waste material. In addition, these recycled aggregates should be low-level processed by crushing concrete lumps with a crushing device, and if necessary, high-level processed by crushing by grinding with heating. Can do.

Table 1 (a) and (b) show examples of the properties of these recycled aggregates.
Table 1 Properties table of recycled aggregates

The recycled aggregate concrete is made by mixing cement and recycled fine aggregate into, for example, a twin-screw mixer 1 as shown in FIGS. 1 (a) and 1 (b) and kneading for 30 seconds. Also, water, an admixture (water reducing agent) mixed for 60 seconds kneading the containing), then 60 seconds kneaded by injecting regeneration coarse aggregate. After that, the rod-like vibrator 2 is inserted to give vibration to the raw material, and the old raw material adhered to the surface of the recycled aggregate so that the given raw material flows sufficiently in the mixer and reaches the whole. To peel off.

As this excitation time, it can be performed over a predetermined time of 30 to 180 seconds,
As will be described later, even if vibration is applied for 60 seconds or more, the effect is not enhanced, and a sufficient effect can be enhanced in 30 to 60 seconds, preferably around 60 seconds.

Thereafter, in order to prevent material separation, it is preferable to knead and discharge again for 30 to 60 seconds.
The total kneading time is about 5 to 6 minutes, and the quality of the recycled aggregate concrete can be improved by performing appropriate kneading and applying vibration according to the gist of the present invention.

About the Example of this invention, compared with the normal aggregate (N) of a comparative example, the low processing recycled aggregate (R) and high processing recycled aggregate (RH) of a concrete waste material, water-cement ratio (W / C) was fixed, the target slump was 8 ± 2.5 cm, and the target air amount was 4.5 ± 1.5%. Table 2 shows the composition of recycled aggregate (R, RH), and Table 3 shows the composition of ordinary aggregate (N).

Table 2 Recycled aggregate formulation

Table 3 Composition table of ordinary aggregate

And about the mixing | blending of recycled aggregate, when a rod-shaped vibrator for 0 minute, 1 minute, and 3 minutes is inserted, about a low processing recycled aggregate (RV-0, RV-1, RV-3), advanced processing For aggregates (RHV-0, RHV-1, RHV-3) and when mixing time is extended for 0 minutes, 1 minute, 3 minutes instead of a vibrator (RM-0, RM-1, RM- 3), and when mixing the normal aggregate (N) when the vibrator is not inserted (NV-0) and when the vibrator is inserted for 2 minutes (NV-2)
).

For the mixing of the concrete, a forced biaxial kneading mixer having a capacity of 60 liters as shown in FIG. 1 was used. The total mixing time was constant at 360 seconds. For the mixing procedure, cement and fine aggregate were added and kneaded for 30 seconds, water and admixture (including auxiliary water reducing agent) were added and kneaded for 60 seconds, and coarse aggregate was added and sequentially kneaded for 60 seconds. 150 seconds after mixing starts, the mixer is temporarily stopped, a rod-like vibrator is inserted, the concrete raw material is vibrated for 60 seconds and 180 seconds, and is sufficiently fluidized and stirred. The old powder adhering to the surface of was peeled off. And about the thing of 60 second vibration, it kneaded again for 30 seconds after that, and discharged | emitted.

About concrete by the above test, air quantity, slump test is performed, 100mm
Using a standard cylindrical specimen form with a diameter of 200 mm, a specimen was prepared by compaction using a vibrator. And it demolded by material age 1 day, and 20 degreeC water curing was performed immediately after demolding.

About these, slump test (JIS A 1101), air quantity test (JIS A)
As a result of 1128), as shown in FIGS. 2A and 2B, the concrete using the low-grade recycled aggregate has a smaller slump than the concrete using the high-grade recycled aggregate. This is probably because low-grade recycled aggregates have a lot of adhesion of raw concrete mortar and cement paste particles. Compared to those using low-grade recycled aggregates, RM (extended mixing time) over RV (vibrated one) regardless of the time to add the vibrator and the mixing time extension ) Has a larger slump. This is considered to be due to the moisture content of the aggregate, because the low-grade recycled aggregate was used in a natural state (at first it was absolutely dry) that was left outside without being in a dry state.

However, the concrete using the low-grade recycled aggregate can improve the fluidity by applying vibration and extending the mixing time. Slump is 3-4c
m, and this tendency is not observed in concrete using highly processed recycled aggregate. Low-grade recycled aggregate containing a lot of aggregate with mortar and cement paste particles attached is thought to be able to peel off these attached particles by applying vibration and increasing the mixing time. . Further, it is considered that the slump is increased by the separation of the adhered particles. In addition, in the aggregate used this time, it can be seen that increasing the one-minute vibrator insertion and mixing time is the time when slump is most easily obtained.

In addition, in the air amount, when the normal vibration is applied, the air amount decreases, but the tendency is opposite. The amount of air increased as the mixing time was increased. This is thought to be due to the fact that a large amount of air was taken in due to the insertion of a vibrator during mixing and an increase in mixing time.

FIG. 3A shows the compressive strength of the low-level processed aggregate when the vibration time is changed. FIG.
b) shows the compressive strength of the low-grade aggregate when the kneading time is changed. RV-1, RV-3 (vibrated) is about 30% compared to RV-0 (non-vibrated) in compressive strength of 28 days, which is a general design standard age. large. By inserting the vibrator, the fine powder adhering to the recycled aggregate is peeled off, new mortar is attached again, and the strength is sufficiently developed. Further, the difference between the vibration time of 1 minute and 3 minutes is not remarkable. Therefore,
In the low-grade treated aggregate, it is judged that the vibrator insertion time can be sufficiently effective in one minute.

At 28 days of age, RM-1 and RM-3 (extended mixing time) are RM-
It is slightly larger than 0 (one that does not extend the mixing time), but at the age of 91 days, the strength is almost the same regardless of the extension of the mixing time. In the low-grade recycled aggregate, the improvement effect on the compressive strength can be obtained by applying a vibrator rather than extending the mixing time.

FIG. 4 shows the influence of the vibrator insertion time on the compressive strength of highly processed aggregate concrete. When vibration is not applied, there is almost no difference in compressive strength at the age of each material for both vibration times of 1 minute and 3 minutes. Highly processed recycled aggregates are almost in the same state as ordinary aggregates because fine powder is removed from the aggregates by heating and grinding. As a result, it is considered that it was close to ordinary aggregate, and even if the vibrator was inserted, the compression bast was not affected.

FIG. 5 shows the effect of whether or not a vibrator is inserted on the compressive strength of concrete using ordinary aggregate. The compressive strength of ordinary aggregate concrete is almost the same value at the same age. Therefore, the insertion of the vibrator into the normal aggregate has no effect on the compressive strength. This is because ordinary aggregates have no adhesion of pulverized fine powder particles of cement paste to the aggregate interface. It is speculated that the increase in compressive strength due to the insertion of the vibrator of the low-level treated aggregate is due to the improvement of the aggregate interface.

Ten or more Vickers hardnesses at the age of 28 days were measured for each sample, and the averages thereof are shown in FIGS. 6 (a), (b), and FIG. 7. Vickers hardness is expressed in HV. Micro hardness on the vertical axis (
0.005HV) represents the strength of the needle pointing to the concrete interface. In RV Vickers hardness,
RV that does not vibrate when the distance from the interface is 100 μm to 300 μm
The hardness of −0 is significantly lower than those of RV-1 and RV-3 that are vibrated. It is thought that the insertion of the vibrator is effective in improving the compressive strength accompanying the strengthening of the transition zone at the aggregate interface by peeling off the mortar and paste particles of the raw concrete. Also, there is almost no difference in compressive strength RV-
1 and RV-3 showed little difference in microhardness as well.

In the RM Vickers hardness, the distance from the interface is 100 μm to 300 μm, and those with longer mixing time (RM-1, RM-3) than those without longer mixing time (RM-0) Micro hardness is slightly small. However, the values were almost the same between 400 μm and 500 μm. There is almost no difference in the compressive strength of what extended the mixing time by the difference in the extended time of mixing. This is considered to be because there is no effect of improving the adhesion at the aggregate interface by increasing the mixing time. In addition, regarding the magnitude of the microhardness, the RV to which the vibrator is charged and the RM that extends the mixing time are about the same value at about 20 HV.

In the RH Vickers hardness, the minute strengths of all the specimens were almost the same value. The microhardness of the highly processed recycled aggregate was the same as the compressive strength regardless of the insertion of the rod-shaped vibrator. Further, when the difference in microhardness was compared between the low-level processed and high-level processed recycled aggregates, the maximum value of the high-level processed recycled aggregates was 15 HV, and the low-level processed recycled aggregates were 20 HV or higher. The aggregate interface of the high-processed recycled aggregate is almost the same as that of ordinary aggregate and does not contain fine powder like the low-processed recycled aggregate. Therefore, it is considered that the state of the aggregate interface does not change.

An experiment was conducted using a 91-day-old concrete specimen prepared using low-grade recycled aggregate and normal aggregate. Table 4 shows the results of a simple freeze-thaw test on specimens prepared by two methods of vibrator insertion and mixing for low-grade recycled aggregates. The number of cycles at the time of cracking, the dynamic elastic modulus, and The average value of the relative dynamic elastic modulus is shown.

Table 4 Degree of cracking

The freeze-thaw temperature specified in JIS-A 1148-2101 “Method for Freezing and Thawing Concrete” is minus 18 ° C., and 300 cycles or a relative dynamic elastic modulus is 60.
The test ends when% is cut off. However, since freeze-thaw was continued until the occurrence of cracks was visually confirmed, the value was measured to a value below 60%. In all types, cracks could be confirmed in 3 cycles. However, paying attention to the relative kinematic modulus, cracks occurred when the RV subjected to vibration was about 50%, whereas the RM with prolonged mixing showed almost 60%. The amount of air in the RV series concrete is smaller than that in the RM, which is considered to be because the resistance to frost damage was improved in the RM. Fig. 8 (a) and (b) show the dynamic elastic modulus and relative dynamic elastic modulus of a simple freeze-thaw test for concrete using low-grade recycled aggregate with vibrator insertion.
).

Regardless of whether or not the vibrator was inserted, the dynamic modulus of elasticity and the relative dynamic modulus of elasticity were greatly lowered in each cycle, unlike the conventional ones. This is because the simple freezing and thawing test using liquid nitrogen was conducted in a very severe environment of minus 193 ° C, and the place where the ultrasonic propagation time was measured (about 150 mm from the bottom) was affected by the freezing and thawing from the past. Because it was an easy place, 30% compression strength difference between RV-1 and RV-3 with a vibrator inserted and RV-0 without a vibrator
This difference was not observed in the results of the simple freeze-thaw test.

Compared with concrete using ordinary aggregate, the recycled aggregate concrete treated at a low level in 3 cycles was cracked, whereas ordinary concrete was not cracked in 6 cycles, and the relative kinematic modulus was It was 70% or more. Moreover, the relative kinematic modulus decreased at twice the speed regardless of whether or not the vibrator was inserted. The same result as that in the past that the recycled aggregate was inferior in frost damage resistance was obtained.

The dynamic elastic modulus and relative dynamic elastic modulus of the simple freeze-thaw test for concrete using low-grade recycled aggregate with extended mixing time and concrete using ordinary aggregate are shown in Fig. 9 (
Shown in a) and (b). Similar to the test results of the concrete with the vibrator inserted, the dynamic modulus of elasticity of the test piece produced by extending the mixing time decreased at about twice the speed of ordinary aggregate concrete. Similarly, it was difficult to discriminate the influence on the kinematic modulus due to the difference in mixing time.

Elevated view (a) and side sectional view (b) of the mixer used in the present invention, Slump test comparison diagram of recycled aggregate concrete (a) and air volume test comparison diagram (b), Concrete compressive strength comparison chart (a) when vibration of low-grade aggregate use is given, and concrete compressive strength comparison chart when mixing time is extended (b), Comparison diagram of concrete compressive strength when vibration of high-processed aggregate is used, Comparison of concrete compressive strength when using normal aggregates with or without vibration Vickers hardness diagram (a) when given the vibration of using the low-grade aggregate as above (b) and Vickers hardness diagram (b) when mixing time is extended, Vickers hardness diagram in the case of mixing time extension using the high processing aggregate as above, (A), (b) Relationship diagram between cycle number and kinematic elastic modulus when vibration of low-grade aggregate is used The relational diagram (a) of the dynamic elastic modulus in the case of the mixing time extension using the low-grade treated aggregate and the normal aggregate use, and the relative diagram (b) of the relative dynamic elastic modulus.

Explanation of symbols

    1 ... Mixer

Claims (4)

It is a method for producing concrete by using recycled aggregate, in which recycled aggregate of cement and concrete waste, water, and raw materials of admixture are mixed, and these are stirred and kneaded with a mixer to produce concrete,
Low-treated cement and concrete waste aggregate Recycled aggregate of aggregate, water, and admixture raw materials are mixed in the mixer, and in the middle of kneading in the mixer, stick-shaped to peel off the old powder adhering to the surface of the recycled aggregate A method for producing concrete using recycled aggregate, wherein the vibration is applied to the raw material for a predetermined time to improve adhesion of the mortar and improve the strength of the concrete.   2. The regeneration according to claim 1, wherein the raw material is vibrated for 30 to 180 seconds in order to peel off the old powder adhering to the surface of the recycled aggregate during the mixing of the raw material in the mixer. A method for producing concrete using aggregates.   In order to peel off the old powder adhering to the surface of the recycled aggregate during the mixing of the raw material and mixing with the mixer, the raw material is vibrated for 30 to 180 seconds to improve the adhesion of the mortar, and the raw material is vibrated. 3. The method for producing concrete using recycled aggregate according to claim 1, wherein the raw material is further kneaded after giving.   Recycled fine aggregate of cement and concrete waste is put into a mixer and kneaded for 30 seconds, mixed with water and admixture for 60 seconds, recycled coarse aggregate is added and kneaded for 60 seconds, and these raw materials are mixed. The method for producing concrete using recycled aggregate according to any one of claims 1 to 3, wherein vibration is applied.

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