00230197

Monograph

http://onlinepubs.trb.org...bs/nchrp/nchrp_rpt_138.pdf

THE OBJECTIVE OF THIS STUDY WAS TO EVALUATE THE SUITABILITY OF EXISTING INSTRUMENTATION AND TECHNIQUES AND TO STIMULATE DEVELOPMENT OF MODIFIED OR NEW PROCEDURES TO MEASURE THE AMOUNT AND STATE OF WATER IN HIGHWAY COMPONENTS, SUCH AS EMBANKMENTS, SUBGRADES, BASE COURSES, PAVEMENTS, AND STRUCTURES. IN ACCOMPLISHING THIS OBJECTIVE, THE RESEARCHERS CONDUCTED AN EXTENSIVE LITERATURE REVIEW. THOSE TECHNIQUES THAT APPEAR TO BE IMMEDIATELY APPLICABLE TO HIGHWAY PROBLEMS WERE EVALUATED USING A LINEAR DECISION MODEL FOR COMPARING INSTRUMENT PERFORMANCE CHARACTERISTICS WITH SPECIFIC MOISTURE MEASUREMENT NEEDS. A COMPREHENSIVE LIST OF PERFORMANCE CHARACTERISTICS WITH WHICH TO MAKE THIS COMPARISON WAS COMPILED. THE DESCRIPTION OF MOISTURE MEASUREMENT INSTRUMENTATION IS DIVIDED INTO CATEGORIES ACCORDING TO THE CHEMICAL AND PHYSICAL PROCESSES INVOLVED IN THE PRINCIPLE OF MEASUREMENT. COMMERCIAL INSTRUMENTATION IS AVAILABLE IN MOST OF THESE CATEGORIES; HOWEVER, AS A RULE, THE INSTRUMENTS ARE NOT DESIGNED FOR USE IN HIGHWAY ENGINEERING APPLICATIONS. THE MOST SUITABLE TECHNIQUES CURRENTLY AVAILABLE FOR USE IN HIGHWAY PROBLEMS ARE THE GRAVIMETRIC METHODS AND NUCLEAR SCATTERING METHODS. FOR NONDESTRUCTIVE SURFACE OR NEAR-SURFACE MEASUREMENTS, THE NUCLEAR METHOD APPEARS TO BE UNEXCELLED. WHERE SAMPLES CAN BE REMOVED FOR ANALYSIS, GRAVIMETRIC METHODS ARE MOST SUITABLE. OVEN DRYING IS MOST COMMONLY USED, AND NORMALLY IS THE STANDARD METHOD FOR CORRELATING VARIOUS HIGHWAY COMPONENT CHARACTERISTICS WITH MOISTURE CONTENT. FOR FIELD USE, CHEMICAL EXTRACTION TECHNIQUES APPEAR TO BE MOST EFFECTIVE. PROBLEMS OCCUR WITH ALL OF THESE TECHNIQUES; HOWEVER, THEIR PERFORMANCE IS SUCH THAT THEY CAN BE OF SIGNIFICANT VALUE IN CERTAIN APPLICATIONS. CANDIDATE METHODS FOR EVALUATION IN UNCONSOLIDATED MATERIALS IN STOCKPILES, BINS, AND CONVEYORS; COMPACTED MATERIALS IN DEPTH OR IN LAYERS AND OTHER SHAPES ARE NUCLEAR, RADIOWAVE, MICROWAVE RESISTANCE, CAPACITANCE, HYGROMETRIC, TENSIOMETRIC, THERMAL CONDUCTIVITY, AND RAPID CHEMICAL AND THERMAL EXTRACTION TECHNIQUES. CERTAIN MODIFICATIONS MAY IMPROVE THE OVER-ALL PERFORMANCE OF NUCLEAR METHODS, WITH CONCURRENT ADDITIONAL COSTS. ONE OF THESE IS THE ADDITIONAL MEASUREMENT OF NEUTRON-ABSORBING MATERIALS BY MEANS OF THE NEUTRON GAMMA TECHNIQUE. IGNITION TESTS ALSO MAY BE HELPFUL IN INTERPRETING SOME MEASUREMENTS IN CLAY MATERIALS. HYGROMETRIC TECHNIQUES USING ALUMINUM OXIDE FILMS MIGHT BENEFIT FROM IMPROVED CONSTRUCTION METHODS. EXTREME CARE IN FABRICATION AND THE USE OF THICK SPUTTERED FILMS SHOULD ADD TO THE QUALITY OF PERFORMANCE OF THESE UNITS. MANY OF THE MEASUREMENT PROBLEMS LACKING SUFFICIENT INSTRUMENTATION COULD BE HANDLED THROUGH THE DEVELOPMENT OF REMOTE-SENSING TECHNIQUES. ONE PARTICULARLY PROMISING TECHNIQUE IS THAT OF IMPLANT TELEMETRY. MOISTURE MEASUREMENT PRINCIPLES THAT ARE COMPATIBLE WITH THIS TYPE OF REMOTE SENSING SHOULD RECEIVE FUTURE RESEARCH EFFORT.

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60 p.

1973

NCHRP Report

Digital/other

Figures (2) ; References; Tables (15)

Gravimetric analysis; Instrumentation; Measurement; Moisture content; Nuclear phenomena; Nuclear powered ships; Remote sensing; Water

Geotechnology; Highways

TRIS, TRB, ATRI

Aug 5 1973 12:00AM