AASHTO T321 PDF

AASHTO T Standard Method of Test for Determining the Fatigue Life of Compacted Asphalt Mixtures Subjected to Repeated Flexural Bending. standard . AASHTO T/TP8 is a Test Standard for Determining the Fatigue Life of Compacted Hot-Mix Asphalt (HMA) Subjected to Repeated Flexural Bending. AASHTO T (AASHTO, ) and the European Standard (EN , ). When evaluating fatigue resistance through four point bending beam.

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It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

An environmental chamber is not required if the temperature of the surrounding environment can be maintained within the specified limits. Agencies that meet the criteria of Specification D are generally considered capable of competent and objective testing, sampling, inspection, etc.

In addition, it shall be capable of recording load cycles, applied loads, and qashto deflections and computing and recording the maximum tensile stress, maximum tensile strain, phase angle, stiffness, dissipated energy, and cumulative dissipated energy at load cycle intervals specified by the user.

Size px x x x x Loading Device—The t3211 system shall include a closed-loop, computer controlled loading component that, during each load cycle in response to commands from the data processing and control component, adjusts and applies a load such that the specimen experiences a constant level of strain during each load cycle. The fatigue life and failure energy determined by this standard can be used to estimate the fatigue life of HMA pavement layers under repeated traffic loading.

Specimen Dimensions—Report the specimen length, average specimen height, and average specimen width in meters to four significant figures. Specimen Aaahto the height and width aashfo the specimen to the nearest 0.

This stiffness is an estimate of the initial aashho, which is used as a reference for determining specimen failure. Control and Data Acquisition System—During each load cycle, the control and data acquisition system shall be capable of measuring the deflection of the beam specimen, computing the strain in the specimen, and adjusting the load applied by the loading device such that the specimen experiences a constant level of strain on each load cycle.

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Use the jig to ensure proper horizontal spacing of the clamps, mm center-to-center. Hot Mix Asphalt Description—Report the binder type, binder content, aggregate gradation, and air void percentage. Cycles to Failure—Failure is defined as the point at which the specimen stiffness is reduced to 50 percent of the initial stiffness.

Prepare a plot of stiffness versus load cycles as shown in Figure 7. The loading device shall be capable of 1 providing repeated sinusoidal loading at a frequency range of 5 to 10 Hz; 2 subjecting specimens to four-point bending with free rotation and horizontal translation at all load and reaction points; and 3 forcing the specimen back to 3t21 original position i. Place the specimen in an environment that is at Select a deflection level strain level such that the specimen will undergo a minimum of 10, load cycles before its stiffness is reduced to 50 percent or less of the initial stiffness.

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Report the test results listed in Table 2 for each load cycle interval selected by the operator to three significant figures. Miscellaneous Apparatus and Materials—A suitable saw for cutting the beams and a mechanism for setting proper clamp spacing. No other units of measurement are included in this standard.

This standard may involve hazardous materials, operations, and equipment.

T_321-07_2011

A stiffness reduction of aashyo percent or more represents specimen failure. Note 7—See E 29 for information on determination of significant figures in calculations. Determine the specimen stiffness at the 50th load cycle. Perform the following calculations at the operator-specified load cycle intervals: Figure 7 presents a typical plot of stiffness versus load cycles.

It is recommended to cut beams from a large slab compacted by a vibratory roller. Duplication is a violation of applicable law.

When the specimen has experienced greater than 50 percent reduction in stiffness, terminate the test. Environmental Chamber Optional —The environmental chamber shall enclose the entire specimen and maintain the specimen at For loading devices that require gluing a nut for deformation measurement, these cut surfaces provide smooth surfaces for mounting xashto measurement gauges.

Note 5—It may not be possible to calculate dissipated energy D for every load cycle due to memory limitations of the recording and control component. Set the loading frequency within a range of 5 to 10 Hz. This standard provides procedures for determining the fatigue life and fatigue energy of mm long by 50 mm thick by 63 mm wide hot mix asphalt HMA beam specimens sawed from laboratory or field compacted HMA and subjected to repeated flexural bending until failure.

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Bias—The research required to establish the bias of this method has not been conducted. Apply 50 load cycles at a constant strain of to microstrain.

The test system shall meet the minimum requirements specified in Table 1. We are a non-profit group that run this website to share documents. Report the initial flexural stiffness in pascals. Note 1—The type of compaction device may influence the test results.

Precision—The research required to develop precision values has not been conducted. The constant A represents the initial stiffness. Please fill this form, we will try to respond as soon as possible. Users of this practice are cautioned that compliance with Specification D alone does not completely ensure reliable results.

Please copy and paste this embed script to where you want to embed Embed Script. Open the clamps and slide the specimen into position Figures 3, 4, and 5.

For loading devices that require a glued nut for deformation measurement, a screw, nut suggested size M 8 by 1 and block assembly for referencing the linear variable differential transducer LVDT to the neutral axis of the specimen, and epoxy for attaching the nut to the specimen are also needed.

Test System—The test system shall consist of a loading device, an environmental chamber aashtoand a control and data acquisition system. Figure 1 illustrates the loading conditions. See Notes 1 and 2.

Next, close the inside clamps by applying sufficient pressure to hold the specimen in place. Prepare a plot of dissipated energy versus load cycles as shown in Figure 6. Link to Active This link will always route to the current Active t231 of the standard.