Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: AASHTO TP 112:2021
• Năm ban hành / Publication date: 2021
• Tình trạng / Status: A - Còn hiệu lực
• Tên tiếng Anh / Title in English: Standard Method of Test for Determining In-Place Density and Moisture Content of Soil and Soil–Aggregate Using Complex Impedance Methodology

Thay thế cho / Replace

AASHTO TP 112:2019

• Số trang / Page: 11

Phạm vi áp dụng / Scope of standard

This practice describes the procedures for determining the density and moisture content of aggregate and soil-aggregate. The practice allows for electromagnetic testing of porous construction materials in the laboratory that is used to calibrate the apparatus to these specific porous construction materials. With such calibration, the field apparatus can then be used on the construction site to test the density and moisture of the porous construction materials without the need for field calibration using a complex impedance measuring instrument (CIMI). The CIMI measures the electrical properties of the material being tested and correlates the electrical properties to the physical properties during a laboratory or field material calibration procedure. The electrical properties are typically unique for the material. During the material calibration procedure, empirically derived correlations relate the electrical and physical properties of the material using the correlation mathematics. The subsequent electrical testing of the material utilizes the established relationship of the electrical and physical characteristics to calculate the material density and moisture content. The CIMI is composed of solid state electronics that are calibrated at the time of manufacturing and no additional instrument is thereafter required.

Density-The total or wet density of aggregate and soil-aggregate mixtures is determined by applying a known frequency of alternating current and measuring it through the material. The complex impedance is calculated based on the measurements and relationships previously established with a known material model.

The density in mass per unit volume is determined by comparison of the readings calculated and the calibration with a representative material model over a range of known densities.

Moisture-The moisture content of the aggregate and soil-aggregate mixtures is determined by applying a known frequency of alternating current and measuring it through the material. The complex impedance is calculated based on the measurements and relationships previously established with a known material model.

The moisture content in mass per unit volume is determined by comparison of the readings calculated and the calibration with a representative model of known moisture content.

SI Units-The values stated in SI units are to be regarded as the standard. The inch-pound equivalents may be approximate. It is common practice in the engineering profession to concurrently use pounds to represent both a unit of mass (lbm) and of force (lbf). This implicitly combines two systems of units, that is, the absolute system and the gravitational system.

This standard has been written using the absolute system for water content (kg/m3) in SI units. Conversion to the gravitational system of weight in lb/ft³ is scientifically incorrect; however, the gravitational system should not be regarded as nonconformance with the standard.

In the English system, the pound (lbf) represents a unit of force (weight). However, the use of balances or scales recording pounds of mass (lbm), or recording of density (lbm/ft3) should not be regarded as nonconformance with this standard.

This procedure does not purport to exhaustively address safety concerns associated with its use. 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. See Section 6 for Hazards.

The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of R 18 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with R 18 alone does not completely assure reliable results. Reliable results depend on many factors; following the suggestions of R 18 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.