Abstract: The present invention provides a method and apparatus for accurately determining weight loss of a sample during heating in a furnace. The method includes the steps of placing a sample in a heated furnace, heating the sample while measurements of sample weight are made, determining rate function from the sample weight measurements, producing a weight loss correction factor using the rate function and using the weight loss correction factor to obtain a corrected weight loss for the sample.

Abstract: The present invention is directed to a method and apparatus for calibrating nuclear gauges and confirming gauge calibrations that provide the accuracy of multiple block calibration methods without requiring multiple standardized calibration blocks of known density. The apparatus includes a support for receiving a nuclear gauge of the type having a radiation source and a radiation detector and a variable radiation filter operatively associated with the support for providing variable attenuation of radiation emitted from the radiation source. The variable radiation filter includes a block having an eccentrically located cavity and positioned for rotation about the central axis of the cavity. The filter may further include a fixed mass for further attenuating radiation discharge by the radiation source such that the energy spectrum produced by the filter substantially matches the energy spectrum of a solid block of material, such as a standardized calibration block.

Abstract: The present invention provides an improved thin layer nuclear density gauge comprising a gauge housing having a vertical cavity therethrough and a base, a first radiation detector located at a first position within said housing and adjacent to said base of said housing, a second radiation detector located at a second position within said housing and adjacent to said base of said housing, a vertically moveable source rod extending into said cavity of said gauge housing, a radiation source operatively positioned within a distal end of said source rod, at least one bearing operatively positioned to guide said source rod within said cavity, and means for vertically extending and retracting said source rod to a plurality of predetermined source rod positions so as to change the spatial relationship between said radiation source and said first and second radiation detectors. The source rod has a maximum radial movement of less than about 0.003 inch at each predetermined position.

Abstract: The present invention provides an improved thin layer nuclear density gauge comprising a gauge housing having a vertical cavity therethrough and a base, a first radiation detector located at a first position within said housing and adjacent to said base of said housing, a second radiation detector located at a second position within said housing and adjacent to said base of said housing, a vertically moveable source rod extending into said cavity of said gauge housing, a radiation source operatively positioned within a distal end of said source rod, at least one bearing operatively positioned to guide said source rod within said cavity, and means for vertically extending and retracting said source rod to a plurality of predetermined source rod positions so as to change the spatial relationship between said radiation source and said first and second radiation detectors. The source rod has a maximum radial movement of less than about 0.003 inch at each predetermined position.

Abstract: An apparatus and method for assaying an asphalt-containing composite material by irradiating the sample using a radiation source having a tunable preselected wavelength selected to closely approximate the absorbance wavelength of a particular material or materials found in the composite material to reduce the overall time and temperatures ordinarily needed to combust and assay such samples.

Abstract: An apparatus for pyrolysis of a sample of a composite material containing a combustible binder includes a combustion chamber configured to receive a sample of the composite material and having an outlet. A heater is associated with the combustion chamber for heating the chamber to a temperature sufficient for pyrolysis of the binder. A blower is in fluid communication with the combustion chamber for creating an airflow through the outlet to remove airborne pyrolysis products from the combustion chamber. An adjustable airflow regulator is operable to adjustably control the airflow to provide a desired minimum residence time within the combustion chamber sufficient for complete pyrolysis of the airborne pyrolysis byproducts.

Abstract: An apparatus and method for testing rutting susceptibility of test specimens. The apparatus includes a specimen holder having cavities for receiving one or more test specimens having an exposed surface for testing. A load bearing surface is positioned above the specimens to prevent friction from effecting the rutting analysis. A load device including at least one loading wheel is positioned adjacent the specimen holder wherein the loading wheels matingly engage the load bearing device. A motive sources provides relative rotational movement between the specimen holder and the loading wheels whereby a load is repeatedly applied to the test specimens under a constant velocity. The method includes testing rutting susceptibility of test specimens by providing a rotational load thereupon whereby the load reflects a linear or constant load across the predetermined path of travel of the loading wheels over the exposed surface of the test specimens.

Abstract: An apparatus for compacting a material sample, such as paving material, including a cylindrical compaction mold and a mold support arranged to support one end of the mold. The mold support includes a turntable mounted for rotation about a rotational axis and a pair of mold-engaging members, such as rollers, extending from the turntable to engage the mold along its periphery and impart a gyratory motion to the mold as the turntable rotates. A mold retainer is also provided that includes a plurality of mold restraints spaced apart from one another about a central axis and arranged to engage the mold about the mold periphery at the end of the mold opposite the mold support. One of the mold restraints is attached to a movable latch that moves the mold restraint between an open position and a closed position. The open position locates the mold restraint out of engagement with the mold to allow the mold to slide into position inside the compactor apparatus.

Abstract: A neutron gauge is described for determining the moisture content of a moisture containing material. Samples of the moisture containing material are confined in a sample pan and a sample cover with sufficient neutron moderating activity is pressed against the sample. The cover, sample, and sample pan are placed in the same location in the gauge with respect to the neutron source and detector for each measurement to compensate for volume variations in the sample. The sample can be weighed to compensate for density variations. The sample pan cover can include a cadmium sheet for direct contact with the sample to shield the sample from neutrons thermalized by the cover.

Abstract: A source capsule containing a radioactive isotope is put inside of an outer protective jacket or capsule and the outer jacket is sealed. The outer protective jacket is so designed that it can be reopened without disturbing the radioactive isotope source capsule contained therein. Thus, when it becomes necessary to recondition the source capsule, the inner source capsule can be removed from the outer protective jacket and it can be re-encapsulated in another outer protective jacket. There is provided an encapsulated radioactive isotope source which comprises an outer protective jacket in the form of a can having a side wall, an integrally formed bottom wall and an open upper end. A source capsule containing a radioactive isotope is received within this outer protective jacket. A jacket cap is received within the outer protective jacket so as to close the open end of the jacket, with the source capsule thus located within the outer protective jacket.

Abstract: An apparatus and method for compacting a material sample, such as soil or paving material, including a mold for receiving the material sample and a ram mounted for movement into a first open end of the mold to provide an axial compressire force thereto. The compacting apparatus also includes a base for supporting a second end of the mold. In operation, the mold is gyrated simultaneously with the application of the axial compressire force by the ram. Gyration is provided by tilting the mold from an initial neutral position in which the center longitudinal axis of the mold is collinear with the axis of compression to a tilted operative position in which the central longitudinal axis of the mold is angularly offset from the axis of compression. The base is thereinafter rotated relative to the mold so as to revolve the center of the second end of the mold about the axis of compression, thus, gyrating the axially compressed material sample.

Abstract: A capacitance monitor for monitoring the moisture content of soil is disclosed in which a capacitance sensing probe having a generally cylindrical probe body and an elongate tubular handle is inserted into an access tube to measure the capacitance of the soil and to thereby determine the moisture content of the soil. The cylindrical probe body has aluminum electrodes separated by a polypropylene dielectric spacer and two sets of circumferentially spaced apart spring biased stainless steel plungers that extend radially outwardly from the probe body to engage the side wall of the access tube and to center the probe body within the access tube. The two sets of plungers are located at opposite ends of the probe body.

Abstract: An instrument and a method are provided for determining the moisture and cement contents of fresh concrete and for calculating and displaying to the user of the instrument the projected strength of the concrete. The instrument has two probes, each probe containing a low-activity nuclear source. The probes are stored in shielded receptacles in a housing when not in use. The user calibrates the probes with reference to concrete compositions of known cement and water content, and then for field use separately inserts each probe into the access tube of a sample pan filled with concrete to obtain counts corresponding to moisture content and cement content. An electronics unit is attached to the housing for storing the correlations and performing the calculations.

Abstract: An apparatus and method for detecting changes in a physical property of the material beneath a large storage vessel, such as a landfill. The apparatus includes one or more tubes defining elongate channels in the material beneath the storage vessel. A sensing probe is moved through the channel while taking and collecting measurements of the physical property of the material in the vicinity of the probe. Typically, moisture and/or density may be measured using conventional nuclear sources and associated detectors. The measurements are compared with reference data to thereby detect a change indicating a leak in the storage vessel.

Abstract: Method and apparatus for determining the asphalt content of a bituminous paving mix wherein Marshall plug samples of the bituminous paving mix are subjected to a neutron source and the neutrons that are thermalized by hydrogen nuclei present in the Marshall plug sample are detected and counted to provide an indication of the asphalt content of the sample. A neutron moderating substance, such as a polyethylene sample holder having receptacles for closely fitting the Marshall plug samples, is included with the sample pan to increase the number of thermalized neutrons resulting from the interaction of neutrons with hydrogen nuclei present in the sample.

Abstract: Measuring the distance to a surface of an object using ultrasonic energy pulses, an ultrasonic energy pulse is directed toward the object and the time is measured for the reflection to return so as to determine the distance to the object. A reference ultrasonic pulse is directed through a fixed and known distance to provide a reference measurement. To enhance the accuracy of the measurement, the air in the region traversed by the ultrasonic pulses is mixed by directing a swirling flow of air in this region so that the temperature of the air in the path of the reference measurement is more nearly representative of the temperature of the air where the distance measurement is taken.

Abstract: The present invention provides an apparatus and method for dynamically measuring the density of soil, asphaltic material and the like during the compaction of the material. The gauge includes a nuclear radiation source and a nuclear radiation detector means which are mounted in spaced relation from the surface of the test material to form an air gap therebetween. The gauge also includes means for measuring the size of the air gap between the test material and the source and detector system, and means to compensate for the effect of the size of the air gap to thereby obtain the density of the test material.

Abstract: A method of measuring the moisture content of soil wherein a tapered probe is inserted into a tapered hole formed in the ground. The walls of the hole are tapered substantially in correspondence with the taper of the probe and such that the soil adjacent the walls is not compacted or otherwise affected. In this manner, good contact between the surface of the probe and the soil is obtained. The probe is a capacitance sensing probe with a pair of spaced electrodes along the tapered surface with a dielectric material in between. The electrodes serve as structural members of the probe body and the hollow internal portion is backfilled to prevent moisture from permeating the probe.

Abstract: This invention relates to a capacitance standard for use with capacitance sensitive probes. The standard comprises a capacitor having a pair of spaced plates and a dielectric positioned therebetween. A shield attached to one of the plates forms an enclosure around the other plate to essentially shield the capacitor. The capacitance standard is therefore not affected by outside electrical fields and an accurate, reproducible capacitance value is provided.

Abstract: The present invention provides a method and system which is useful on instruments requiring experimentally determined calibration curves by which calibration data can be transferred to a plurality of field gauges, thereby avoiding the necessity of individually calibrating each gauge each time calibration is necessary. The field gauges are initially cross related to a master gauge. At a later time when a new calibration is necessary, the master gauge is calibrated using carefully prepared samples of a test material. Using the experimentally derived calibration curves with the cross relation data provides calibration data for the field gauges.