Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Reexamination Certificate
2001-05-23
2002-06-04
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
C340S870120, C340S870020
Reexamination Certificate
active
06400161
ABSTRACT:
TECHNICAL FIELD OF INVENTION
The present invention relates generally to a Material Analyzing Apparatus and Method for measurement of density and segregation (or non-uniformity) of a test material. The measurement of density and segregation are accomplished by making surface contact between the apparatus and the unknown material. The apparatus for such measurements may be stationary or moved across a test surface under analysis. The measurements are non-destructive and do not alter the material under analysis.
BACKGROUND OF THE INVENTION
The invention relates to a material segregation and density analyzing apparatus and method to analyze density and segregation of a material. In particular, the invention relates to a material segregation and density analyzing apparatus and method to analyze at least one of density and segregation of asphalt.
Ninety-six percent of all paved roads and streets in the United states, almost two million miles, are surfaced with asphalt. Asphalt is a relatively low cost pavement material, especially in comparison to other pavement materials, such as concrete. Another asphalt feature that makes it superior to concrete for pavement is its flexibility. The maintenance of asphalt is also typically less expensive than maintaining concrete.
It is the nature of asphalt pavement to be non-uniform. It is very difficult to achieve a non-segregated and completely homogeneous asphalt mix for pavement. Also, the asphalt mix is very difficult to apply in an essentially uniform pavement layer. Therefore, the pavement is characterized by measurements in material variations and/or segregation. These variations or segregation are often visible on the pavement surface, however, it is a very subjective and difficult process for quantifying the pavement segregation amount. Pavement segregation is representative of pavement density.
Segregation can be defined as the separation of coarse and fine aggregate particles in the hot mix asphalt mixture. Alternately, segregation has been described as a separation and consolidation of the larger aggregate asphalt particles, which leave the asphalt mass and rise to the surface of the mix. This segregation can occur in the mixed material before it is fed onto the highway or it may become segregated as it is being placed onto the road surface. Research indicates that segregation has a direct impact on the long-term performance of the asphalt pavement by increasing the air void content of the mix, thus increasing the potential for moisture damage, raveling, cracking and a total disintegration of the affected road surface. Therefore, it is desirable to determine the pavement segregation.
When paving a particular highway, the asphalt mix, which is to be applied is routinely checked for mix properties at the asphalt mix plant. The check attempts to verify the asphalt mix integrity and homogeneity, and thus to control the ultimate density of the asphalt mix, when applied and rolled. The check of the asphalt mix can be correlated to resultant pavement density and segregation when applied. Accordingly, pavement specimens for control can be available for potential density device calibration or referencing of pavement density indicator devices.
When an asphalt paver lays a layer of asphalt mix for compaction on a highway, the asphalt quality will relate to the longevity of the new highway. Such longevity-influencing factors include, but are not limited to, density of the asphalt mix as it becomes compacted on a road surface and the homogeneity and segregation of the asphalt mix. Although the mix of liquid asphalt and rock aggregate segregation may have been ideal at the asphalt plant, there is no guarantee of the mix quality as applied to the road surface. The lack of homogeneity can be described as segregation.
Paving material (pavement) is typically laid down by a paver at about 75% of its desired compaction. During subsequent compaction, for example by being rolled over, it is very desirable to compact the paving material close to the final desired pavement compaction degree, without altering the segregation. The pavement compaction should be as close to the desired compaction to provide an absence of material variations, such as, but not limited to, air voids, which are believed to create defects in the resulting paved structure.
The level of pavement compaction cannot be readily determined without complicated measurements. These complicated pavement measurements may not be accurate. In the past, these complicated pavement measurements typically involved boring out of a portion of the rolled pavement (hereinafter also referred to as “extractions”) and measuring their density in the lab. This process forms a hole in the pavement, which of course is not desirable. This hole is not desirable as the integrity of the pavement is breached.
In order to address these asphalt-related problems, various complicated asphalt pavement measurement systems and devices have been proposed and developed. For example, and in no way limiting of the invention, measurement of pavement dielectric properties has been proposed to determine pavement density, which has been suggested as an indicator of pavement compaction level.
One such known pavement density indicator device is disclosed in U.S. Pat. No. 3,784,905 to Blackwell. The Blackwell device appears to measures dielectric properties of the applied and rolled asphalt, in which the dielectric properties are believed to be representative of a change in pavement or asphalt density. The Blackwell device appears to operate at low frequencies where its operations are subject to variations in moisture and temperature, and thus can result in errors. While Blackwell may provide adequate operations in some instances, the Blackwell device must be moved at extremely slow speeds across the material being tested to obtain a density reading. Thus, it appears that the Blackwell device may need extended time periods of operation to provide a density determination, which as discussed above is not desirable. Further, the Blackwell device possesses a large weight, which may necessitate large supportive objects to support and transport the Blackwell device. The large objects may be dragged across the applied pavement surface, thus potentially causing damage to the often freshly-applied pavement.
Another potential disadvantage of the Blackwell device may be its limited depth adjustability for measurement. This limited depth adjustability may be attributed to the Blackwell electrodes only varying a depth of measurement by changing the height of the electrodes. This electrode configuration is not desirable due to the limited depth adjustability for measurement.
Another known pavement indicator device comprises a nuclear source, which is used to determine density of a pavement material. This nuclear-sourced device has a variety of drawbacks. Some of these drawbacks in the nuclear-sourced devices include that the nuclear-sourced device requires a licensed operator, controls, and a radiation shield (e.g., a lead enclosure). Of course, these nuclear-sourced device drawbacks lend to an increased cost of the nuclear-sourced device, increased cost of operation, and inherent dangers found with nuclear materials. Further, the nuclear-sourced device is non-adjustable for pavement area and depth, requires long time for, and is very heavy and difficult to maneuver. Furthermore, the nuclear-sourced device is also very expensive, at least in part due to the nuclear material of the nuclear-sourced device. Additionally, these nuclear density devices need to be constantly correlated to core densities that are taken from the same location as was nuclear gauge tested. This correlation should be done for each different mix that might be used. These steps are of course timely and cost consuming, and thus make use of these nuclear devices undesirable.
Another conventional pavement density indicator device is set forth in U.S. Pat. No. 5,900,736 assigned to TransTech Systems. The TransTech System pavement density indicator device is a non-nuclear, asphal
Hamdan Wasseem H.
Metjahic Safet
LandOfFree
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