The advanced asphalt testing laboratory is located in the Fiedler Hall. The laboratory has been built with generous support from the Kansas Asphalt Pavement Association (KAPA). The Kansas Department of Transportation (KDOT) and Kansas State University also sponsored part of this laboratory. This facility has greatly enhanced the capabilities of Kansas State University in teaching, research and training of Superpave technology. The laboratory has the following pieces of equipment:
(i) A PMW Wheel Tracking Machine (Hamburg Rut
Tester)
(ii) A PMW Kneading Compactor
(iii) An IPC UTM-25 Universal Tester
(ivi) A Bending Beam Reheometer
(v) A Dynamic Shear Rheometer
In addition to the above, a Rotational (Brookfield) Viscometer will
be acquired in the near future.
PMW Wheel Tracking Machine (Patent Number: 5,987,961)
The PMW wheel tracking machine acquired in this laboratory was manufactured by Precison Machine & Welding, Salina, Kansas (premac@midkan.com). This lab testing equipment is used to test the rutting and moisture damage (stripping) potential of asphalt mixes by simulating roadway conditions in a controlled environment. Some images of this machine are shown below:
The PMW wheel tracker uses two Linear Variable Displacement Transducers (LVDT's) to measure the deformation of two replicate asphalt concrete slab samples at eleven points across each sample. This information is compiled and printed out in graphical form for further calculations and interpretation. Two wheels are used to simulate rutting (one on each sample) at 158 pounds of pressure at contact point. If a sample reaches maximum deformation (rut depth) before the allotted test time is completed, it will lift the wheel off of that sample and continue with the test on the other sample. The wheels are moved back and forth by means of motor gearbox and crank shaft connecting rod assembly. Wheels are mounted on a slider frame which is mounted on 4 linear bearings. This machine is capable of running 36 passes per minute to 70 passes per minute, using a frequency drive. Temperature is maintained constant with a water bath. Heaters are controlled with an SCR controller that is in turn driven by a PID loop in the CPU. The temperature is controlled from 0-80 degrees celsius. Water is circulated over a weir plate & back into the heating reservoir, and from there pumped through a filter system and returned to the water bath. The machine is partially self cleaning and has auto drain and auto fill. The whole system is controlled by a PC and CPU system. The software is of original design, it is Windows based and easy to operate. Currently several units are in operation. These are owned by Koch Industries in Wichita, Kan., the University of Texas at Austin, the Texas DOT and Lousiana Transportation Research Center.
PMW Kneading Compactor
The PMW kneading compactor, which has been acquired recently, was also
manufactured by Precision Machine & Welding, Salina, Kansas (premac@midkan.com).
This compactor is needed to fabricate slab samples for the PMW wheel tracking
machine or beam samples for fatigue testing. This linear compactor is driven
by a hydraulic unit that can be located beside the compactor, or in another
room and plumbed in. It is capable of compacting two slabs at once,
thus increasing productivity, decreasing clean-up time, and reducing deviations
in sample quality and temperature. The compactor can be programed
for different lengths of stroke, thus making possible samples of different
length. Compaction mold sizes can also be variable, the compactor
is capable of multiple sample sizes, if needed. It is constructed
primarily of stainless steel, and 1045 steel, ruggedly constructed for
functionality. Accuracy of stroke is achieved using a PLC, and linear
transducer controlled cylinder, coupled with proportional valve.
Slabs can be loaded, run, and completed in less than five minutes. Some
images of this compactor are shown below:
Superpave Mix Performance Tester
KSU has recently acquired an IPC UTM-25. The machine is capable of doing resilient modulus, fatigue and creep tests of Superpave mixture samples.
Dynamic Shear Rheometer (DSR)
The Dynamic Shear Rheometer (DSR) is used to characterize the viscous and elastic behavior of asphalt binders. The DSR measures the viscous and elastic properties of a thin asphalt binder sample sandwiched between an oscillating and a fixed plate. As the force (shear stress) is applied to the asphalt by the spindle, the DSR measures the response (shear strain) of the asphalt to the force. The relationship between the applied stress and the resulting strain in the DSR quantifies both types of behavior, and provides information necessary to calculate two important asphalt binder properties: the complex shear modulus (G* -"G star") and phase angle ("delta"). G* is the ratio of maximum shear stress to maximum shear strain. The time lag between the applied stress and the resulting strain is the phase angle.
The DSR selected for the KAPA Advanced Asphalt Laboratory is the DSR QC Asphalt (shown below), manufactured by ATS RheoSystems and REOLOGICA Instruments AB, for quality control testing of Performance Grade (PG) binders according to AASHTO designation TP5.
Bending Beam Reheometer (BBR)
The BBR has been purchased earlier as part of the Superpave laboratory
development at KSU. The BBR is used to measure the rheological
properties (stiffness modulus and log slope of the creep curve) of PG binder
at low-temperature. It is one of the tests required by Superpave for checking
PG asphalt binder specifications. Typically, tests are run between
0 to -36° C to an accuracy of ± 0.1° C. The time to complete
a test is approximately five minutes and calibration time is less than
five minutes. In this test, a constant load is applied at the center of
a small asphalt beam for a selected period of time. During this loading
time, the deflection of the beam is measured continuously and monitored
by a computer. KSU currently owns a Cannon Thermoelectric Bending Beam
Rheometer (shown below).
Rotational (Brookfield) Viscometer
A Brookfield Viscometer will also acquired for the Advanced Asphalt Laboratory. Rotational viscosity is used to evaluate high temperature workability of binders. A rotational coaxial cylinder viscometer, such as the Brookfield apparatus, is used rather than a capillary viscometer. High temperature binder viscosity is measured to ensure that the asphalt is fluid enough when pumping and mixing. Consequently, rotational viscosity is measured on unaged or "tank" asphalt and must not, according to the Superpave binder specification, exceed 3 Pa-s when measured at 135 deg C.
The model has not been finalized, but is expected to a Bohlin (shown
below) or equivalent.
If you need more information about this laboratory, please contact (mustak@ksu.edu) or Stefan Romanoschi (sromano@ksu.edu).
