GeoGauge — H-4140

Compaction Uniformity
via in-place Stiffness Measurement ASTM D6758

The GeoGauge is a unique, QC/QA field tool that can be used to measure the uniformity of unbound pavement layers by measuring the variability in stiffness throughout a structure. It is an excellent tool for identifying construction anomalies that would otherwise go undetected during construction where only density or percent compaction measurements were used. By measuring stiffness, the GeoGauge can reveal and thus help reduce variabilities in layer properties, which density measurements may miss, thus allowing corrective actions to be taken during construction to ensure that the highest quality base and subgrade are achieved despite variations in materials used.

The GeoGauge is the perfect companion instrument for density measuring devices such as nuclear gauges and the electrical density gauge. Density measuring devices can be used to ensure that proper compaction is achieved and the GeoGauge can be used to verify that the stiffness/modulus values assumed in the design specifications of new or rehabilitated pavement structures are met.

Compacting and monitoring
pavement layers directly to design
requirements of structural
layer stiffness or material modulus
in addition to percent compaction
during the construction process
establishes the means to effectively
control structural uniformity,
strength and deflection, as well as
enabling the monitoring and control
of the construction quality of various
materials. This leads to better
smoothness and longer lasting
pavement surfaces at lower cost.

The GeoGauge works by applying a
vibrating force at 25 specific frequencies,
which produce small deflections in
the material. The resulting displacement is
measured by the GeoGauge and displayed
as stiffness determined by the ratio of the force to deflection. The GeoGauge produces stress and strain levels common for pavement, bedding and foundation applications. In addition, Young's and shear modulus can be determined from GeoGauge measurements if a Poisson's ratio is assumed. This dynamic technology used by the GeoGauge simulates real in-use conditions. This factor allows the GeoGauge to directly measure in-place engineering properties during the construction process. The GeoGauge supports and directly links the in-place engineering properties of compacted materials with Mechanistic-Empirical Design for effective QC/QA. Successful control of compaction creates a quality functional structure with the desired engineering properties for the application and life intended.

Applications include subgrade, sub-base, base, monitoring the strength gain of lime, cement, fly-ash and polymer stabilized materials, monitoring the re-compaction of underground utility backfills to previous properties matching surrounding undisturbed materials, monitoring the compaction of asphalt and cold in-place recycling to peak properties to prevent wasted effort and damaging over-compaction.


Verifier Mass, 10kg— H-4140.20
Verifies calibration of gauge.

Calibration Platen, 10kg— H-4140.C
Platen used to allow gauge to self-calibrate. Gauge is bolted onto platen with a torque wrench (included).

Ifrared Data Cable— H-4140.12
Infrared (IR) serial interface adapter cable with spreadsheet software template

GeoGauge Data Sheet


Layer Stiffness17 to 400 klbf/in (3 to 90 MN/m)
Young's Modulus (in-place)4 to 90 kpsi (26 to 610 MPa
Measuring Depth9 to 12 inches (230 to 310 mm)
Measuring Duration75 seconds
Powersix D-cell batteries
(1000 to 1500 measurements)
Dimensionsgauge only: 11" dia. x 10.5" high (280 mm x 270 mm)

carrying case: 18.5" x 16.5" x 13" (470 x 420 x 330 mm)
Net Weightgauge only: 22 lbs. (10 kg)
with case: 34 lls. (15.5 kg)
Shipping Weight39 lbs. (17.7 kb)

Features include:

  • Dynamically measures in-place engineering properties using structural layer stiffness, MN/m (klbf/in) and Young's Modulus of a material, MPa (kpsi)
  • In-place QC/QA links compaction and material performance directly to design requirements while advancing Mechanistic-Empirical Pavement Design
  • Enables maximum lift stiffness with minimum compactive effort
  • Facilitates uniform stress transmission and distribution from pavement to subgrade resulting in longer pavement life, reduced maintenance costs and longer lasting surface smoothness.
  • Enables reduced structural variability in construction
  • In-place QC/QA of the strength gain of stabilizedmaterials
  • Data base development supporting Mechanistic-Empirical Design and performance specifications
  • Portable, fast, simple, reliable, non-invasive
  • Other compaction applications include: lime, cement, fly-ash and polymer stabilized materials, cement-treated and rehabilitated bases, large particle aggregate bases, as well as underground utility backfills
  • Gauge includes simple, easy-to-use software application, which provides download and storage of test data. Application allows printing of data reports, as well as saving information in other fornats (.pdf, .csv and Rich Text) for importing data into other programs