This paper presents findings on the effectiveness of field modulus determinations and modulus based assessment of constructed pavement foundation geomaterials, i.e. subgrade soil and base/subbase unbound aggregate material. Full-scale unsurfaced pavement test sections were constructed on controlled strength weak subgrades and tested to failure for studying effects of aggregate quality on pavement performance. Differences in aggregate quality were assessed by changes in aggregate properties such as particle angularity, fines content and plasticity of fines. In-situ moduli of the constructed layers were measured using both light weight deflectometer (LWD) and GeoGaugeTM type field devices. Tests were conducted on the engineered subgrade as well as on the finished aggregate layer surface with data collected consistently from the same locations using the two devices. Both the GeoGaugeTM and the LWD were successful in identifying anomalies in construction conditions, i.e., increasing or decreasing trends in moduli. However, field achieved dry densities and aggregate qualities could not be linked to the field modulus values, which also differed from the laboratory-measured resilient modulus properties.