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马歇尔 测试方法: Everything You Need to Know

马歇尔 测试方法: Everything You Need to Know

What is the 马歇尔 测试?

的 马歇尔 method of asphalt mix design is widely practiced in construction materials laboratories to select and proportion aggregate and asphalt materials for pavement construction. This holistic approach to asphalt pavement mix design involves the selection of mineral aggregate and binder materials, preparation of trial samples, load testing for strength and flow of materials, and lab tests of material properties. 的 focus is on the determination of an optimum asphalt content that will provide maximum strength to the mix with minimum deformation from axle loads. 马歇尔 stability and flow test values, 密度, and air voids in the mix and the mineral aggregate are all used for evaluation of trial mixtures of lab-mixed, lab-compacted (LMLC) asphalt mixtures. 马歇尔 stability and flow tests can also monitor the production of the asphalt mixture using plant mix, laboratory-compacted (PMLC) samples.

Background and History

第二次世界大战期间, t在这里 was an urgent need to quickly construct suitable airfields for large 军事 aircraft with increasingly higher wheel loads. 在1943年,美国的军事行动.S. Army Corps of Engineers began evaluating several asphalt pavement mix design methods at their Waterways Experiment Station (WES) in Vicksburg, 密西西比州. 的 马歇尔稳定度 Method developed by Bruce 马歇尔 at the 密西西比州 Highway Department in 1939 seemed to be the most promising after a procedure to measure deformation (flow) was added. 的 马歇尔 method was recommended based on simplicity, rapid and effective test results, and the fact that some of the apparatus was compatible with equipment currently in use for the California Bearing Ratio (CBR) load test for subgrade soils. Because of its straightforward process and equipment, along with widespread use by the U.S. 军事, the method is used in some capacity by many state departments of transportation and is the most widely used pavement design system in the world.

马歇尔稳定度 测试: 的 Process

的 马歇尔 process uses a series of laboratory tests and evaluation criteria for selecting materials and to progressively narrow in on optimum mix design. A suitable mix will resist deformation from traffic loads and damage from climatic conditions and will have adequate skid resistance.

注意: 测试s associated with 马歇尔 mix design have procedures specified in several different ASTM and AASHTO test methods, as well as many local and regional variations. 的 contents of this article are a guide to equipment and common practices only and are in no way intended to supersede requirements in any of these published test methods.

总选择 begins with lab testing to measure the physical properties of aggregates. 耐磨性, 稳健, 耐用性, and particle shape all combine to ensure the aggregates themselves are durable and will also contribute to the strength and resistance to deformation of the final asphalt mix. 的 chart below shows some typical laboratory tests performed for the evaluation of proposed aggregates. T在这里 are linked references for testing equipment and ASTM / AASHTO test methods.

综合测试


AASHTO /
AASHTO
方法
磨损
电阻
稳健韧性耐用性影响
电阻
形状 &
纹理
分级具体的
重力
洛杉矶磨耗XXXXX
Micro-DevalXXX
硫酸
稳健
C88 / T 104XX
耐久性指数

D3744 /

T 210

XX
细gg
有角

C1252 /

T 304

XX
沙子
等效

D2419 /

T 176

XX
平 &
细长的
D4791 / N/AX
成薄片 &
伸长
BS-812X
颗粒大小
分布
C136 / T 27X
特定的重力/
吸收
C128 / T 84X

的 blending of aggregates of different size fractions or shape characteristics is often performed to produce mixtures with greater densities, 的优势, 或处理属性.

沥青 binder selection is not performed according to a specific procedure in the 马歇尔 method. 的 Superpave Performance Grading (PG) binder system is often used, but final selection may be based on experience, 之前的表现, 或者局部手术. 的 PG system characterizes the suitability of an asphalt binder based on the expected climatic conditions as well as aging conditions under which it is to be used. So, a binder selected for use in Florida would be different from the one used in Minnesota. PG binders are classified with two numbers that represent the maximum and minimum pavement temperatures (in Celsius) at which they are suitable.

AASHTO m320图表

样品制备 starts with an estimate of what the optimum binder content will be, based on experience and past performance. Several trial blends of aggregate and asphalt binder are prepared in laboratory-scale 搅拌机 with binder contents at, above, and below the estimated optimum in increments of 0.5%. Each trial mix must contain enough material to compact three specimens for stability and flow measurements, 通常约2.6lb (1.2kg) for each specimen. 的 ASTM D2041/ AASHTO T 209 theoretical maximum specific gravity, 或米测试, is performed to document 密度 characteristics of the design mix. A selection of equipment for performing this test can be found 在这里. 实验室烤箱 are required to heat and condition aggregate and asphalt materials, compaction hammers, and molds.

样品压实 is performed by manual or automatic 马歇尔压实工具 10磅(45.36kg) mass and 18in (457.2mm) drop height and stationary or rotating operation. 的 prepared and heated trial blends are compacted into 马歇尔 压实模具, each consisting of mold, collar, and base plate in 4in (101.6毫米或6英寸(152.4毫米)直径. 的 number of blows required for specimen compaction is typically 35, 50, or 75, depending on anticipated traffic loads. 的 specified number of blows is applied to one side of the specimen, then the mold is reversed, and the same number applied to the opposite side. 的 intact and compacted specimens are extracted from the mold with a  样本喷射器 and the bulk specific gravity is measured following ASTM D2726/ AASHTO T 166

稳定 and flow testing are described in test methods ASTM D6927/ AASHTO T 245. 的 compacted asphalt specimen is conditioned in a  水浴 before being placed in a 马歇尔打破头. 的 breaking head and specimen assembly are positioned in a  马歇尔 stability tester 配备  组件 to measure stability and flow during the test. This test predicts the performance of the trial mixes. 稳定 is the maximum strength of the mix when loaded at a rate of 2in (50.每分钟8毫米). During the loading process the plastic flow, or deformation of the specimen, is recorded in 0.01in (0.25mm) increments by a dial gauge or linear variable displacement transducer (LVDT).  Data acquisition software is available to record, graph, calculate, and report 马歇尔 test values automatically.  ASTM D5581 can also be used for 6in (152mm) compacted specimens or pavement cores.

马歇尔 Data Acquisition Software Screenshot

Characterization/measurement of 密度 and voids are important properties for a complete analysis of the proposed mix design. 正如上面所提到的, specific gravity and 密度 values are determined using the ASTM D2041/AASHTO T 209 theoretical method (Rice test) for the loose asphalt material and ASTM D2726/AASHTO T 166 to determine the bulk specific gravity of compacted specimens. T在这里 is also a need to describe various types of air void contents. Air void content in compacted mixtures consists of the small spaces between coated aggregate particles in a compacted mixture and is a test method defined in ASTM D3203/ AASHTO T 269. T在这里 are two other void values determined by calculations.

  • Voids in mineral aggregates (影响规律) are defined as the void space between the aggregate particles in a compacted mixture. 影响规律 is calculated based on the aggregate bulk specific gravity and is expressed as a percentage of the bulk volume of the compacted mixture.

    的 formula for calculating 影响规律 is:

\[影响规律 = {100 - {GmbPs \over ’}}\]

地点:
影响规律 = Voids in mineral aggregate, in percent of bulk volume
= 散装 specific gravity of the aggregate
Gmb = 散装 specific gravity of compacted mix
Ps = Aggregate, percent by total weight of mix

  • Voids filled with asphalt (的浓度) in a compacted paving mixture, consisting of that portion of the initial voids in the aggregate (影响规律) which have been filled with the non-absorbed asphalt.

    的浓度 can be determined by the following equation:

\[的浓度 = {100({影响规律 - Pa \over 影响规律})}\]

地点:
的浓度 = voids in mineral aggregate, percent of bulk volume
Pa = air voids in compacted mixture, percent of total volume

测试方法s and 设备

的 chart below references some ASTM and AASHTO standard test methods related to the 马歇尔 mix design method, along with laboratory equipment required for the tests.

实验室
测试
设备
ASTM / AASHTO
测试方法
最大
具体的
重力和
密度
散装
具体的
重力的
压实
标本
沥青
准备
&
压实
沥青
稳定
&
百分比
含气率
样品的高度
或厚度
米测试D2041 / T 209X
体积密度X
马歇尔
压实
D6926 / T 245XX
稳定 &
XX
含气率在
压实
混合
D3203 / T 269X
样本
厚度
D3549X

We hope this blog has given you a better understanding of the 马歇尔 asphalt mix design method and some of the associated test standards and lab equipment. For questions about your application, please loveBet爱博体育下载.

About the Author Ben Backus