Device for detecting compaction and shear strength characteristics of asphalt mixture during construction compaction

Abstract

A device is for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction. The device includes a fixed frame and a detection system. The detection system includes a display, a control panel, a test claw, an electric motor, a lift switch, a torque sensor and a temperature sensor. The control panel includes a power switch for controlling the electric motor and a speed regulator for controlling a rotation speed of the test claw. An output end of the electric motor is connected to an input end of the torque sensor, and an output end of the torque sensor is connected to an input end of the test claw. An output end of the test claw is provided with a claw-shaped blade. The claw-shaped blade is provided therein with the temperature sensor.

Claims

1. A device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction, comprising a fixed frame (1) and a detection system, wherein the detection system comprises a display (2), a control panel (3), a test claw (4), an electric motor (5) for driving the test claw (4) to rotate, a lift switch (6) for controlling a vertical movement of the test claw (4), a torque sensor (7) and a temperature sensor (8); the control panel (3) comprises a power switch (31) for controlling the electric motor (5) and a speed regulator (32) for controlling a rotation speed of the test claw (4); an output end of the electric motor (5) is connected to an input end of the torque sensor (7), and an output end of the torque sensor (7) is connected to an input end of the test claw (4); an output end of the test claw (4) is provided with a claw-shaped blade (9); the claw-shaped blade (9) is provided therein with the temperature sensor (8).

2. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 1, wherein there are at least 3 claws of the claw-shaped blade (9).

3. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 2, wherein there are 3-6 claws of the claw-shaped blade (9).

4. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 1, wherein the bottom of the claw-shaped blade is a conical tip.

5. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 2, wherein the bottom of the claw-shaped blade is a conical tip.

6. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 3, wherein the bottom of the claw-shaped blade is a conical tip.

7. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 4, wherein a universal wheel (10) is arranged at the bottom of the fixed frame (1) to facilitate a free movement.

8. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 5, wherein a universal wheel (10) is arranged at the bottom of the fixed frame (1) to facilitate a free movement.

9. The device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to claim 6, wherein a universal wheel (10) is arranged at the bottom of the fixed frame (1) to facilitate a free movement.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a structural diagram of a device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction according to the present invention.

(2) FIG. 2 is a structural diagram of a test claw.

(3) FIG. 3 is a diagram showing the use of a device for detecting compaction and shear strength characteristics of an asphalt mixture.

(4) Reference numerals: 1. fixed frame; 2. display; 3. control panel; 31. power switch; 32. speed regulator; 4. test claw; 5. electric motor; 6. lift switch; 7. torque sensor; 8. temperature sensor; 9. claw blade; and 10. universal wheel.

DETAILED DESCRIPTION

(5) To make the technical means, creative features, purpose of use and effects of the present invention comprehensible, the present invention is further described blow with reference to the specific implementations.

(6) Referring to FIG. 1 and FIG. 2, the present invention provides a preferable device for detecting compaction and shear strength characteristics of an asphalt mixture during construction compaction. The device includes a fixed frame 1 and a detection system. A universal wheel 10 is arranged at the bottom of the fixed frame 1 to facilitate a free movement for on-site construction detection. The detection system includes a display 2, a control panel 3, a test claw 4, an electric motor 5 for driving the test claw 4 to rotate, a lift switch 6 for controlling a vertical movement of the test claw 4, a torque sensor 7 and a temperature sensor 8. The control panel 3 includes a power switch 31 for controlling the electric motor 5 and a speed regulator 32 for controlling a rotation speed of the test claw 4. An output end of the electric motor 5 is connected to an input end of the torque sensor 7, and an output end of the torque sensor 7 is connected to an input end of the test claw 4. An output end of the test claw 4 is provided with a claw-shaped blade 9. There are 6 claws of the claw-shaped blade 9. The bottom of the claw-shaped blade is a conical tip, which is convenient for pressing into the asphalt mixture with a certain degree of compaction. The claw-shaped blade is provided therein with the temperature sensor 8.

(7) As shown in FIG. 3, a specific process is as follows:

(8) step 1: surface, intermediate and base courses of the asphalt mixture are paved separately on site; after the base course is compacted by a compactor, the detection device is moved to a selected detection point, and the universal wheel is fixed;

(9) step 2: the claw-shaped blade on the output end of the test claw is pressed into the asphalt mixture with a certain degree of compaction through a lift switch;

(10) step 3: the power switch of the electric motor is turned on; the electric motor drives a stirring shaft to rotate slowly and uniformly with a speed freely selected between 5°/min and 10°/min; a temperature T (° C.) and a torque M (N.Math.m) on the display are recorded;

(11) step 4: the torque M obtained in step 3 is used to calculate a shear strength and a shear stiffness of the asphalt mixture:

(12) $F=G\gamma =\frac{M\rho }{I_p}$$G=\frac{F}{\gamma }=\frac{M\rho }{\gamma I_p}$

(13) where, F is the shear strength, G is the shear stiffness, γ is a shear strain, ρ is a radius, and I.sub.p is a polar moment of inertia; and

(14) step 5: the shear strength and the shear stiffness obtained in step 4 are used to calculate a compaction detection index K/K.sub.min of the asphalt mixture, where K is defined as an inverse of the shear stiffness,

(15) $K=\frac{1}{G},$
and K.sub.min is a minimum value of K of the asphalt mixture under a corresponding degree of compaction; the compaction detection index K/K.sub.min obtained in real time is compared with a standard interval of K/K.sub.min in Standard Table 1 to determine the compaction status of the asphalt mixture, so as to adjust and control the construction process and construction quality in time; when a value of K/K.sub.min is greater than a right end value of the standard interval, a section is under-compacted and supplementary compaction construction should be implemented in time; when the value of K/K.sub.min is smaller than a left end value of the standard interval, the section is over-compacted, and a remedial measure for over-compaction should be taken in time; when the value of K/K.sub.min is within the range of the standard interval, the compaction of the base course is completed and steps 1-5 may be repeated to construct the intermediate and surface courses.

(16) The corresponding values of the compaction detection index K/K.sub.min and the degree of compaction in Table 1 are standard values obtained by using the detection device and method of the present invention to repeatedly detect the design asphalt mixture (AC-13C asphalt mixture herein) and acquire and calibrate the data in a design stage. It should be noted that the values in the standard table may vary with different design asphalt mixtures in actual engineering, but the detection device and method used are essentially unchanged.

(17) TABLE-US-00001 TABLE 1 Standard table of compaction detection index K/K.sub.min and degree of compaction in correspondence Degree of compaction 0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96 0.98 K/K.sub.min Left end 0.8 0.82 0.84 0.85 0.86 0.87 0.88 0.88 0.9 0.9 value Right end 2.2 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 value

(18) The corresponding values of the compaction detection index K/K.sub.min and the degree of compaction in Table 1 are standard values obtained by using the detection device and method of the Table 1 shows that the compaction detection index K/K.sub.min calculated by the detection device is inversely proportional to the degree of compaction. A higher degree of compaction indicates a worse compactability of the mixture and a smaller compaction detection index. Based on the compaction detection index obtained on site, the detection device monitors the compaction status of the mixture in real time and adjusts the construction in time to prevent and remedy the under- and over-compaction conditions. The compaction detection index, the degree of compaction and other volume indexes are used together for construction guidance to achieve dual control of the construction compaction index and ensure a good compaction effect of the asphalt mixture.

Embodiment 1

(19) In this embodiment, for example, an AC-13C asphalt mixture in a surface course is under a post-paving state. Three compactors are used to compact a section with a compaction method as shown in Table 2.

(20) TABLE-US-00002 TABLE 2 Compaction method of section Primary Secondary Final Compaction step compaction compaction compaction Type of compactor Steel drum Vibratory Steel drum compactor compactor compactor Compaction speed 3 4 5 (km/h) Compaction times 2 2 3

(21) The corresponding values of the compaction detection index K/K.sub.min and the degree of compaction in Table 1 are standard values obtained by using the detection device and method of the A compactor follows a paver to perform primary compaction. After static compaction by a steel drum compactor, a nuclear-free density gage is used to measure a degree of compaction of the asphalt mixture. Compaction and shear strength characteristics detection device is used to measure a real-time compaction detection index K/K.sub.min and an internal temperature T of the mixture. An electric motor drives a stirring shaft to rotate slowly and uniformly. A rotation speed is freely selected from 5°/min to 10°/min. Detection indexes of the compaction status are shown in Table 3.

(22) TABLE-US-00003 TABLE 3 Detection indexes of primary compaction status of section Internal temperature Degree of Stake No. of mixture °/C. compaction/% K/K.sub.min K2 + 060 127.1 82 1.96 K2 + 080 129.9 86 1.24 K2 + 100 126.2 84 1.27

(23) The corresponding values of the compaction detection index K/K.sub.min and the degree of compaction in Table 1 are standard values obtained by using the detection device and method of the purpose of the primary compaction is to level and stabilize the mixture, while creating a condition for secondary compaction. After the primary compaction is completed, the degree of compaction of the mixture reaches more than 80%, and the primary compaction temperature is maintained at 110-130° C., which is a normal construction temperature. Compared with compaction and shear strength characteristics index K/K.sub.min under a corresponding degree of compaction in FIG. 4 and a standard value in Table 1, the compaction detection index K/K.sub.min of the asphalt mixture in each section is in the range of a standard interval. This indicates a good primary compaction status of the mixture.

(24) The secondary compaction follows the primary compaction. The secondary compaction is a key step for the compaction, stabilization and formation of the mixture. After the secondary compaction is completed with a vibratory compactor, the compaction performance of the asphalt mixture is detected the same as that in the primary compaction step. The detection indexes of the compaction status are shown in Table 4.

(25) TABLE-US-00004 TABLE 4 Detection indexes of secondary compaction status of section Internal temperature Degree of Stake No. of mixture °/C. compaction/% K/K.sub.min K2 + 060 90.4 86 1.84 K2 + 080 110.6  95. 1.24 K2 + 100 108.2 97 1.02

(26) The corresponding values of the compaction detection index K/K.sub.min and the degree of compaction in Table 1 are standard values obtained by using the detection device and method of the For section K2+060, the degree of compaction after the secondary compaction is too small. The detection index K/K.sub.min of the mixture is 1.84, which is greater than a normal value of 1.70 under a corresponding degree of compaction (86%), indicating that the compaction of the section is not qualified. The internal temperature of the mixture is 90.4° C., which is lower than a normal secondary compaction temperature (95-115° C.). Therefore, remedial construction cannot be performed, and it is recommended that the section be scrapped and repaved.

(27) For section K2+080, the temperature of the mixture is acceptable. The compaction detection index K/K.sub.min of the mixture is 1.24, which is greater than a normal value of 1.20 under a corresponding degree of compaction (95%). This indicates that the internal mechanical property of the mixture is not up to standard, and the compaction of the mixture is unqualified. The following methods may be used to improve the mechanical property of the mixture:

(28) 1. replace the vibratory compactor with a tire compactor to knead the mixture to reduce the friction between particles and allow a small particle to enter a gap between large particles; and

(29) 2. slow down the compaction of the vibratory compactor and increase the contact time between the compactor and the mixture; or adopt a high-frequency large-amplitude method to generate a large excitation force.

(30) For section K2+100, the internal temperature, the degree of compaction and the compaction and shear strength characteristics of the mixture all are acceptable, indicating that the mixture is in good compaction status and a next stage of construction may be implemented.