A New Low-Activity Nuclear Density Gauge for Compaction Control of Asphalt, Concrete, Soil, and Aggregate Layers in Road Construction

Abstract

AbstractDensity is used as a measure for quality control of compaction of asphalt, concrete, soil, and aggregate layers in road construction. For in-place density measurements, nuclear gauges have been successfully used for decades because of the good measurement properties, such as precision and sensitivity of the nuclear technique. The technique is nondestructive and is a direct method for measuring density. The widespread use of nuclear gauges has been limited because of the nuclear regulatory requirements associated with the usage of radiation sources.To overcome this limitation, in 2016, a nuclear gauge using a low-activity radiation source and a high-efficiency detector was developed. This gauge used mostly for compaction testing of soil and aggregate layers and is exempt from the nuclear regulatory requirements in the United States. Using similar technology, a new nuclear gauge was developed recently to measure density of asphalt and concrete layers in addition to soil and aggregate layers. This gauge is also exempt from the nuclear regulatory requirements in the United States. The new gauge has the option of using a separate probe based on an electromagnetic method for measuring the moisture content of soils and aggregates. This paper presents the design features, measurement properties, and safety aspects of the new nuclear gauge and its associated moisture probe. Comparison of the new low-activity nuclear gauge and a conventional nuclear gauge for measurement of density of asphalt layers, and density and moisture of soil and aggregate layers of thickness up to 30-cm (12-in.) are also presented.KeywordsCompactionSoilAsphaltNuclearGaugeGamma