The ASTM D2041/ AASHTO T 209 theoretical maximum specific gravity, or Rice test, is performed to document density characteristics of the design mix.
#MARSHALL AVT 50H BLEW TRIAL#
Each trial mix must contain enough material to compact three specimens for stability and flow measurements, usually about 2.6lb (1.2kg) for each specimen. Several trial blends of aggregate and asphalt binder are prepared in laboratory-scale mixers with binder contents at, above, and below the estimated optimum in increments of 0.5%. Sample preparation starts with an estimate of what the optimum binder content will be, based on experience and past performance. PG binders are classified with two numbers that represent the maximum and minimum pavement temperatures (in Celsius) at which they are suitable.
So, a binder selected for use in Florida would be different from the one used in Minnesota. The 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. The Superpave Performance Grading (PG) binder system is often used, but final selection may be based on experience, previous performance, or a local procedure. The blending of aggregates of different size fractions or shape characteristics is often performed to produce mixtures with greater densities, strengths, or handling properties.Īsphalt binder selection is not performed according to a specific procedure in the Marshall method. There are linked references for testing equipment and ASTM/AASHTO test methods. The chart below shows some typical laboratory tests performed for the evaluation of proposed aggregates. Abrasion resistance, soundness, durability, 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. The 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.Īggregate selection begins with lab testing to measure the physical properties of aggregates. Note: Tests associated with Marshall mix design have procedures specified in several different ASTM and AASHTO test methods, as well as many local and regional variations. A suitable mix will resist deformation from traffic loads and damage from climatic conditions and will have adequate skid resistance.
#MARSHALL AVT 50H BLEW SERIES#
The Marshall process uses a series of laboratory tests and evaluation criteria for selecting materials and to progressively narrow in on optimum mix design. military, 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. Because of its straightforward process and equipment, along with widespread use by the U.S. The Marshall 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. The Marshall Stability Method developed by Bruce Marshall at the Mississippi Highway Department in 1939 seemed to be the most promising after a procedure to measure deformation (flow) was added. Army Corps of Engineers began evaluating several asphalt pavement mix design methods at their Waterways Experiment Station (WES) in Vicksburg, Mississippi. Background and Historyĭuring World War II, there was an urgent need to quickly construct suitable airfields for large military aircraft with increasingly higher wheel loads. Marshall stability and flow tests can also monitor the production of the asphalt mixture using plant mix, laboratory-compacted (PMLC) samples.
Marshall stability and flow test values, density, 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. The focus is on the determination of an optimum asphalt content that will provide maximum strength to the mix with minimum deformation from axle loads. 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. The Marshall method of asphalt mix design is widely practiced in construction materials laboratories to select and proportion aggregate and asphalt materials for pavement construction.
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