CN101629886A - Method for testing high-temperature indirect tensile strength of bituminous mixture - Google Patents

Abstract

The invention discloses a method for testing high-temperature indirect tensile strength of bituminous mixture, aiming at providing a testing method that a testing result is affected by self weight of a test piece in the testing process and taking heterogeneity of the bituminous mixture into consideration. In the testing method of the invention, the test piece of the bituminous mixture is ring-shaped, evenly-distributed radial pressure is applied on the inner wall of the test piece, tensile stress is generated on the inner wall of the test piece along the radial direction under the action of radial pressure, and a fracture surface is generated at the weakest position of the test piece under the action of the tensile stress. The ring-shaped test piece in the testing method of the invention can use a static pressure formation test piece or a test piece from an edge runner mill, rotary hit or Marshell hit formation by using a core drilling machine for drilling, cutting and forming. The test piece can also be obtained by drilling a sample from the site of the bituminous road surface engineering and two-end finishing and forming. The testing device of the testing method of the invention comprises a sample forming and supporting device, a loading device and a data acquisition system.

Description

A kind of method for testing high-temperature indirect tensile strength of bituminous mixture

Technical field

The present invention relates to the road engineering indirect tensile strength and measure the field, especially relate to a kind of method for testing high-temperature indirect tensile strength that is applicable to asphalt.

Background technology

In road engineering, the indirect tensile strength of asphalt is one of important indicator of highway pavement structural design.Existing asphalt indirect tensile strength means of testing mainly comprises: the test of (1) beam deflection; (2) diametral compression test." highway engineering pitch and asphalt testing regulations " (JTJ052-2000) stipulated: adopt the indirect tensile strength of the method mensuration asphalt of diametral compression test, test temperature must not be higher than 30 ℃.

In recent years, high-temperature indirect tensile strength as a kind of accurately, simple performance testing index, be used to estimate the high temperature rutting resistance of asphalt

The direction of conducting oneself with dignity is identical because beam deflection test and diametral compression test load apply direction and asphalt, and when test temperature during greater than 30 ℃, high-temperature indirect tensile strength of bituminous mixture is less, adopt said method to carry out testing high-temperature indirect tensile strength of bituminous mixture, its result is subjected to the influence of the weight of test specimen own easily, carries out the testing high-temperature indirect tensile strength of bituminous mixture precision with existing method and is difficult to guarantee.

Summary of the invention

Technical matters to be solved by this invention is to provide a kind of new test method and instrument at above-mentioned deficiency of the prior art.In the method, test specimen is an annular, the test specimen inwall is applied uniform radial pressure make its stretcher strain and destruction (accompanying drawing 1).Under radial compression applied, test specimen produces identical tension along radial direction at the test specimen inwall, under action of pulling stress, can produce the plane of fracture (accompanying drawing 2) at the weakness of test specimen according to the unevenness of sample itself.

Test philosophy is as follows: according to theory of elastic mechanics, inside radius is a, and external radius is that the annulus of b does not have constraint at outer wall, and only is subjected to internal pressure q _aDo the time spent, annulus inner radial normal stress ${\mathrm{\&sigma;}}_r=-\frac{a^2(b^2-r^2)}{r^2(b^2-a^2)}{q}_a$ Compressive stress always, hoop normal stress ${\mathrm{\&sigma;}}_{\mathrm{\&theta;}}=\frac{a^2({\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="A2009100208840007H1.png"\; state="\{\{state\}\}">b</figure-callout>}}^2+r^2)}{r^2(b^2-a^2)}{q}_a$ Tension always, tension is in annulus specimen inwall maximum.And | σ _θ|＞| σ _r|.Consider the asphalt indirect tensile strength much smaller than its compressive strength, so the destruction of annulus only may be the fail in tension that at first appears at inwall.Work as q _aWhen enough big, the circle ring inner wall tensile stress sigma _{θ α}Reach the tensile strength sigma of material _t, crackle appears in inwall; Because the stress of crack tip is concentrated, crackle is expanded rapidly and is made sample break destruction.Therefore can think that annulus is broken the maximum internal pressure power q when destroying _{A max}Pairing inwall hoop tensile stress sigma _{θ α max}Be exactly the fail in tension intensity σ of sample _t

Whole test device (seeing accompanying drawing 3) by specimen molding with prop up device, charger and data acquisition system (DAS) three parts and form.Testing main flow process comprises: at first ring-type test specimen 1 is held in place on the annular test-piece pallet 7 between base 2 and the upper cover plate 3, start Hydrauservo System 17 and drive piston 19 upwards motion in hydraulic jack 18, provide test required hydraulic environment by the enclosed elastic cavity that is communicated with hydraulic jack 18 for ring-type test specimen 1 simultaneously, promptly apply radially and uniform internal pressure at ring-type test specimen 1 inwall.According to Elasticity knowledge, its inwall is subjected to uniform internal pressure to do the time spent, the radial normal stress σ that it is suffered in that the outside surface of ring-type test specimen 1 is free _rBe always compressive stress, hoop normal stress σ _θBe always tension, and tensile stress sigma _θMaximal value occur on the inwall of ring-type test specimen 1.Again since the tensile strength of road engineering material much smaller than its compressive strength, so the destruction of ring-type test specimen 1 only may at first appear in the fail in tension of its inwall, promptly the inwall of ring-type test specimen 1 is destroyed because of stretching the earliest.In process of the test, detect by the displacement of pressure transducer 15 in real time with displacement transducer 20 pairs of enclosed elastic inside cavity fluid pressure and hydraulic jack 18 used pistons 19, by pressure signal and the displacement signal that pressure transducer 15 and displacement transducer 20 are gathered, can reflect accurately that ring-type test specimen 1 suffered interior pressure in process of the test changes and because of the volume-variation situation of the enclosed elastic cavity inner chamber that the application of force caused.Pressure transducer 15 reaches data Collection ﹠ Processing System 16 with the signal that is collected simultaneously with displacement transducer 20, and the corresponding simultaneously corresponding control Hydrauservo System 17 of analyzing and processing of carrying out of 16 pairs of data of being gathered of data Collection ﹠ Processing System is moved.When the interior pressure of ring-type test specimen 1 enough big, and the suffered tensile stress sigma of its inwall _θReach the tensile stress sigma that the tensile strength of material can bear _tThe time, crackle will appear in inwall, by being crackle detected internal pressure q when occurring this moment _a, just can calculate the tensile strength of ring-type test specimen 1.Loading system peak load 10T, loading speed is 1～50mm/min stepless change, the constant temperature oven 23 that is arranged in whole experiment above upper cover plate 3 outsides, the base 2 maintains test temperature on the steady temperature, can temperature corresponding selection between 31 ℃-60 ℃ be adjusted according to different needs in the practice.

Ring specimen of the present invention adopts the static pressure method shaping test piece, also can hit reality or the marshall compaction shaping test piece is got also excision forming with boring the core machine drill from edge runner, rotation.Moulding is repaired at two ends after also can drilling through sample from the bituminous pavement engineering site.

Advantage of the present invention is: than existing method of testing, institute's load application direction is vertical with test specimen deadweight direction, can overcome the influence of test specimen deadweight to test result; And in test process, the stressing conditions of each section of annular test-piece is all identical, therefore in this test, from the annular test-piece inwall test specimen is carried out the even application of force, test specimen destroys from the weakest section automatically, this makes the heterogeneity of asphalt obtain consideration, compares with other method of testing to have obvious superiority.

Embodiment

Embodiment

Select limestone aggregates for use, No. 90 pitches in Kelamayi.Adopt AC-13 grating intermediate value.Adopt the static pressure method shaping test piece, the sample dimensions of making is inside radius a=25mm, external radius b=75mm, high h=50mm.Each test specimen adopts 1678 grams to gather materials, and bitumen aggregate ratio adopts 3.5%, 4.5%, 5.5%, 6.5% respectively.

Sample dimensions a=25mm, b=75mm, r=25mm substitution σ _θExpression formula, can obtain the expression formula σ of circle ring inner wall maximum tension stress _t=1.25q _aTest specimen was placed 60 ℃ of constant water bath box 1 hour, take out respectively, be held in place on the annular test-piece pallet between base and the upper cover plate, calorstat temperature is set to 60 ℃, and the oil cylinder loading speed is 50mm/min, records maximum internal pressure power q _{A max}, different bitumen aggregate ratio AC-13 asphalt tensile strength are as shown in table 1 down to calculate 60 ℃ respectively.

AC-13 asphalt tensile strength under the different bitumen aggregate ratios of table one

Bitumen aggregate ratio	Tensile strength (kPa)
		??3.5％	??56.34
??4.5％	??53.28
		??5.5％	??45.76
??6.5％	??30.27

Description of drawings

Fig. 1 is the stress synoptic diagram of ring-type test specimen.

The stress synoptic diagram that Fig. 2 looks squarely for the ring-type test specimen.

Fig. 3 is a structural representation of the present invention.

Description of reference numerals:

1-ring-type test specimen; The 2-base; The 3-upper cover plate;

The 4-removable cover; The 5-support column; The 6-bolt;

7-test specimen pallet; The 8-screw; 9-ring-shaped rubber plug one;

10-ring-shaped rubber plug two; The 11-rubber diaphragm; 12-O type circle;

13-three-dimensional joint; The 14-hydraulic tube; The 15-pressure transducer;

The 16-data Collection ﹠ Processing System; The 17-Hydrauservo System; The 18-hydraulic jack;

The 19-piston; The 20-displacement transducer; The 21-support bar;

The 22-roof timbering; The 23-constant temperature oven.

Claims (4)

1. method for testing high-temperature indirect tensile strength of bituminous mixture, it is characterized in that: under the hot conditions, bitumen mixture specimen is an annular, the test specimen inwall is applied uniform radial pressure make stretcher strain of annular test specimen and destruction.

2. according to the described assay method of claim 1, it is characterized in that: described ring specimen, can adopt the static pressure method shaping test piece, also can hit reality or marshall compaction shaping test piece and get also excision forming with boring the core machine drill from edge runner, rotation.Moulding is repaired at two ends after also can drilling through sample from the bituminous pavement engineering site.

3. according to the described assay method of claim 1, it is characterized in that: described hot conditions is 31 ℃-60 ℃.

4. according to the described assay method of claim 1, it is characterized in that: asphalt refers to petroleum bitumen, emulsified asphalt or foamed asphalt etc. and the potpourri that gathers materials.

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