Charles Jahrencjahren@iastate.edu email >
Associate Director, Construction Materials and Methods / Asset Management
About the research
Rapid determination of the in-situ hydraulic conductivity for pavement subbase/base layers is critical to ensure that the constructed product meets the design and performance expectations. Currently, no widely accepted specifications or test methods exist for QA/QC of in-situ hydraulic conductivity. This research project produced a ruggedized and repeatable test device known as the Gas Permeameter Test (GPT) for rapid in-situ determination of hydraulic conductivity using an innovative approach based on gas flow measurements through the partially saturated material. The newly developed GPT measures hydraulic conductivity in less than 30 seconds, has a measurement range of about 10 -4 to 10 cm/s, is completely self contained, and was validated for several different materials. Because rapid measurements can be made in the field, measurements collected in a grid pattern can be used to produce color-coded spatial maps of hydraulic conductivity. Implementation of this device will improve construction process control by identifying and mitigating construction practices that lead to unwanted segregation, and will improve confidence that the assumed design values are achieved, which should contribute to improving the service life of pavements. Figure 1 below highlights the key elements and outcomes from this study: (1) aggregate segregation problem identification, (2) test device conceptual and final design, (3) GPT manufacturing and calibration, and (4) field evaluation of the GPT. Although this research project resulted in a validated and functional device, to fully implement this technology, detailed specifications, field training, and pilot projects are needed.