JP5812585B2 - Method for promoting exfoliation of asphalt mixture - Google Patents

Description

  Techniques relating to pavement material analysis are disclosed below.

  In recent years, drainage pavements that have become widespread are laid by forming a water-permeable surface layer with an open-graded (porous) asphalt mixture on a water-impermeable base layer. In addition, if the base layer is also permeable with an open-graded asphalt mixture, it becomes a permeable pavement that allows moisture to penetrate into the roadbed. Recently, a water-permeable surface layer is newly laid on the existing pavement as a base layer.

  In these drainage and water-permeable pavements, it has been found that lateral flow after pavement occurs relatively early, and it has been found that the main cause is the peeling phenomenon of the asphalt mixture of the base layer. Furthermore, even in impermeable dense-grain pavement, water may penetrate into the base layer from cracks generated after pavement, leading to deterioration. Therefore, a peeling evaluation test is performed on the asphalt mixture of the base layer in advance. For example, as disclosed in Patent Document 1, a peeling evaluation test is performed by preparing a specimen of a base layer asphalt mixture, and generating a water-permeable specimen that promotes peeling by repeatedly applying water permeability pressure with hot water of 30 ° C to 70 ° C. It is carried out by comparing with a standard specimen that does nothing. As an index, the ratio of the crush strength (permeability crush strength) of the water-permeable specimen to the crush strength (standard crush strength) of the standard specimen ([permeability crush strength / standard crush strength] ] × 100), the peeled area ratio (visual observation) of the water-permeable specimen is used.

JP 2005-128009 A

  The specimen peeling promotion method carried out during the peeling evaluation test is carried out by a method in which water permeation pressure is repeatedly applied with warm water as disclosed in Patent Document 1. That is, a water temperature of 30 ° C. to 70 ° C., a water permeability of 50 KPa to 600 KPa, a sealing pressure (side pressure) for preventing water leakage from the side of the specimen 100 KPa to 700 KPa, and the water permeability is periodically applied to the specimen for a predetermined time. It is implemented by giving. In the peeling promotion method of the said system currently implemented, it takes about 4 hours or more from the start to the end, and it takes one day to finish the peeling promotion of one specimen. Since the peeling evaluation test must be performed on a plurality of specimens on the base layer, it takes a very long time to promote peeling of a large number of specimens.

  In view of this background, there is a need for a peel promoting method that requires less time.

  A method for promoting the peeling of the asphalt mixture, which is proposed for the above problem, is to immerse a specimen of the asphalt mixture in a liquid in a sealed container, and raise the pressure in the sealed container to be higher than the atmospheric pressure to This is a peeling promotion method in which the liquid temperature in the container is maintained at a boiling point or higher at atmospheric pressure and the specimen is cured for at least 30 minutes under the temperature and pressure conditions.

  According to the peeling promotion method according to the above proposal, the specimen is forcibly immersed in the inside of the specimen by applying the osmotic pressure by immersing the specimen in a pressurized hot liquid exceeding the boiling point under a pressure exceeding atmospheric pressure. Therefore, the curing time for promoting peeling is 30 minutes at the shortest. That is, the test time can be shortened as compared with the conventional peeling promotion method.

The figure which showed embodiment of the airtight container used for the peeling promotion method which concerns on this invention. The figure (A) which looked at the airtight container of FIG. 1 from the lid side, and the figure which looked from the bottom side (B). The figure which showed the airtight container of FIG. 1 in the cross section.

1 to 3 show an embodiment of a closed container used for a peeling promotion method for promoting peeling of an asphalt mixture in order to perform a peeling evaluation test.
The sealed container of the present embodiment includes a bottomed metal (thermally conductive material) cylindrical container 1 and a metal disc-shaped lid 2 that hermetically seals the inside of the container by sealing the mouth of the cylindrical container 1. Have. The cylindrical container 1 has a flange 1a at the mouth and a drain port 1b (see FIG. 3) for cleaning or the like at the bottom. A belt-shaped band heater 3 is wound around the body of the cylindrical container 1 and is controlled by the controller Cnt. The lid 2 has the same diameter as the flange 1a of the cylindrical container 1, the peripheral edge of the lid 2 abuts on the flange 1a, and the peripheral edge is fixed to the flange 1a by a plurality of bolts 2a. The bolt 2a passes through the through holes 2b provided at equal intervals on the peripheral edge of the lid 2, and is screwed into the screw hole 1c of the flange 1a (see FIG. 3).

  A drain port 1 b provided at the center of the bottom of the cylindrical container 1 is sealed with a metal drain plug 4. The drain plug 4 that plugs the drain port 1 b has a circular flange 4 a at the head, and four locations of the flange 4 a are fastened with bolts 4 b and are fixed to the center of the bottom of the cylindrical container 1. The bolt 4b passes through the through hole 4c of the flange 4a and is screwed into the screw hole 1d at the bottom of the cylindrical container 1 (see FIG. 3).

  A hermetic seal is maintained between the lid 2 and the drain plug 4 and the cylindrical container 1 by the packing materials P1 and P2. On the contact surface of the peripheral edge of the lid 2 that contacts the flange 1a, a convex strip 2c is provided in a circular shape, and on the contact surface of the flange 1a, a concave strip 1e corresponding to the convex strip 2c of the lid 2 is circumferential. Established. When the lid 2 is fixed to the flange 1a, the ridges 2c are accommodated in the recesses 1e, and the packing material P1 is sandwiched between the ridges 2c and the recesses 1e. Further, on the outer surface of the bottom portion of the cylindrical container 1, a recess 1f is provided in a circular shape so as to surround the drain port 1b, and the packing material P2 is accommodated in the recess 1f. The packing material P2 is pressed by the flange 4a of the drain plug 4, and is pressed into the recess 1f to be in close contact therewith.

  The lid 2 is provided with a vent hole 2d for releasing the abnormal pressure (see FIG. 3), and a safety valve SV that is opened when the pressure in the sealed container is abnormally increased is attached to the vent hole 2d. The lid 2 is further attached with a thermometer TM, a pressure gauge PG, and a drain cock DC for draining water. The thermometer TM hangs down from the lid 2 into the water, measures the water temperature, and outputs a measurement signal to the controller Cnt. The pressure gauge PG measures the pressure in the sealed container. In the drain cock DC, a pipe hangs down from the lid 2 into the water, and after the promotion of peeling, the cock is opened to release the liquid (its vapor) to the outside, and the internal pressure of the container is reduced to atmospheric pressure.

  In the sealed container having the above structure, water or other liquid suitable for promoting peeling is accommodated in the cylindrical container 1, the lid 2 is closed, and heat is applied from the band heater 3, so that the inside of the container exceeds the atmospheric pressure. With pressure, the liquid inside can be maintained at a temperature above the boiling point under atmospheric pressure. For example, when water is used, the pressure in the container can be increased to about atmospheric pressure + 600 kPa (or higher) by heating with the band heater 3, and the water temperature in the container can be increased to 100 ° C. or higher. The specimen 5 of the asphalt mixture is immersed in the pressurized hot water in the container to execute peeling promotion. The specimen 5 is placed on the table 6 in the cylindrical container 1. The table 6 is, for example, a desk shape that supports the top plate with four legs, and the top plate has a mesh shape or the like. During the promotion, the water temperature in the container is measured by the thermometer Tm and transmitted to the controller Cnt, and the controller Cnt controls the band heater 3 according to the measured value. Further, the pressure in the container during the promotion is measured and monitored by the pressure gauge PG.

  At the start of peeling promotion, first, the lid 2 is opened, the specimen 5 is set on the base 6 in the cylindrical container 1, and the lid 2 is closed after the water is poured to the eighth minute, and all bolts 2a are tightened. And seal. Then, the band heater 3 is energized to start heating. When the internal pressure of the container rises by heating and exceeds the atmospheric pressure, the water in the container is not vaporized but becomes pressurized hot water having a temperature exceeding the boiling point of 100 ° C. at atmospheric pressure. The controller Cnt monitors the water temperature and controls the band heater 3 so that the water temperature is 100 ° C. or higher, preferably 120 ° C.

  While performing control so that the water temperature is maintained at 120 ° C. by the band heater 3, the specimen 5 is cured within the sealed container for a curing time of 30 minutes or longer, and 120 minutes at the longest. When the osmotic pressure is applied to the specimen 5 in pressurized hot water, the specimen 5 is forcibly immersed in the specimen, and peeling is promoted during the curing time. The curing time of 30 minutes to 120 minutes is sufficiently shorter than the conventional peeling promotion method. As described above, in the conventional peeling promotion method, it takes about 4 hours at the shortest to promote the peeling, and therefore, the peeling can be promoted only once per day. Compared with this, according to the peeling promotion method of this embodiment, since peeling promotion can be implemented in about 60 minutes, peeling promotion can be implemented 3 times a day. In addition, the structure of the apparatus is simplified as compared with the conventional apparatus disclosed in Patent Document 1.

  After the curing time has elapsed, the sealed container is cooled, and water (water vapor) is discharged from the drain cock DC. The cooling may be either natural cooling or forced cooling. After removing water and reducing the pressure, the lid 2 is opened and the specimen 5 is taken out.

  Using a specimen of an asphalt mixture, preparing a standard specimen cured in the air without any changes and a water-permeable specimen accelerated by the conventional peeling promotion method, and performing a peeling evaluation test, The crush strength ratio and peel area ratio were measured. If the crushing strength of the standard specimen is the standard crushing strength and the crushing strength of the water-permeable specimen is the water-permeable crushing strength, the crushing strength ratio is obtained as [permeable crushing strength / standard crushing strength] × 100. Can do.

  On the other hand, using a specimen of an asphalt mixture using coarse aggregates with different static peeling rates, preparing a water immersion specimen that has been peel-promoted by the peel promoting method of the present embodiment, conducting a peel evaluation test, the above standard From the comparison with the specimen, the crushing strength ratio and the peeled area ratio were measured. When the crushing strength of the water immersion specimen is the immersion crushing strength, the crushing strength ratio can be obtained by [water immersion crushing strength / standard crushing strength] × 100. The peeling promotion method of the present embodiment is carried out at a water temperature of 100 ° C., 110 ° C., 120 ° C., 130 ° C., 140 ° C., 150 ° C. using separate specimens, and at each temperature, 0 min. Curing times of 30 minutes, 60 minutes, 90 minutes and 120 minutes were implemented. If the water temperature rises above 200 ° C., the asphalt and aggregate of the specimen are roughly separated, and the exfoliation state is exceeded. In addition, it was excluded that the curing time exceeded 120 minutes because it would take too much time as before.

  Correlation of the crush strength ratio obtained in the peel evaluation test by the peel promoting method of the present embodiment performed under the above conditions with respect to the crush strength ratio obtained in the peel evaluation test by the conventional peel promoting method ( R) was studied. As a result, a relatively good correlation was obtained in the test specimens in which the curing time was 30 minutes to 120 minutes at each temperature between 100 ° C. and 150 ° C. When a specimen showing a high correlation with correlation R ≧ 0.7 is extracted, at least a water temperature of 110 ° C./120° C./130° C. with a curing time of 30 minutes, a water temperature of 110 ° C./120° C./130° C. with a curing time of 60 minutes, Since specimens having a water temperature of 110 ° C./120° C. with a curing time of 90 minutes were extracted, a water temperature of 120 ° C. and a curing time of 60 minutes showing that all adjacent conditions showed a high correlation were judged as the optimum conditions. In addition, about the peeling area rate, the range was seen more widely than before and came to be able to judge more clearly.

1 Cylindrical container 2 Lid 3 Heater 4 Drain stopper 5 Specimen DC Drain cock PG Pressure gauge SV Safety valve

Claims (3)

A peeling promotion method for promoting peeling of an asphalt mixture,
Immerse the specimen of the asphalt mixture in water in a sealed container,
Control the pressure inside the sealed container to be higher than atmospheric pressure and keep the water temperature in the sealed container at 100 ° C to 150 ° C,
Curing the specimen for 30 minutes to 120 minutes under the temperature and pressure conditions,
Peeling acceleration method. The exfoliation promoting method according to claim 1, wherein the water temperature in the sealed container is controlled to be maintained at 110 ° C. to 130 ° C. , and the curing time is 30 minutes to 90 minutes . The exfoliation promoting method according to claim 1, wherein the water temperature in the sealed container is controlled to be kept at 120 ° C, and the curing time is 60 minutes.

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