A comparative evaluation of the in-place stiffness modulus using a van-integrated falling weight deflectometer (FWD) and the GeoGauge (soil stiffness gauge – SSG) was done on a limestone all-in-aggregate (AIA), used in the base course of a highway pavement. The tests were done in two campaigns, one for each unbound granular layer of 0.15 m thickness, along 510 m, using five alignments. Considering the whole granular materials used, the dry unit weight (γ_d) is related with the stiffness modulus obtained with the SSG. The stiffness moduli obtained for the SSG and for the FWD in the same test point are not correlated. Considering as reference the equivalent modulus obtained with the FWD, the moduli computed for the 85th percentile with both the FWD and the SSG show a difference lower than 20%. These results emphasise the possible use of the SSG as a reliable procedure for stiffness modulus evaluation of unbound limestone bases.