This study investigates the microstructure of lime-treated clayey soils using mercury intrusion porosimetry (MIP) and environmental scanning electron microscopy (ESEM) analyses. Parameters that were varied include lime percent (3, 6, 9%), curing duration (7, 28 days and 1 year), soil pulverization level and mellowing period (1 and 24 h). All samples were compacted at optimum water contents using standard Proctor compaction energy. The 34 MIP and several ESEM analyses conducted on these samples showed that lime content and curing duration had significant impact on the resulting microstructure. MIP results, presented as mercury intrusion curves, total porosity values and pore size distribution histograms revealed that lime stabilization changed the microfabric of clayey soils through a dynamic pore refinement process. Although increases in pore sizes and porosities were observed in the short term (up to 28 days), after a curing period of 1 year, considerable decreases in pore sizes and porosities were noted. A novel "Pore Size Amplification Factor", (PSAF) was calculated to determine the amplification and/or deamplification of different pore size ranges compared to the untreated soil. ESEM analyses confirmed that while the addition of lime to clayey soils initially increased pore size within the microstructure, over time, as the pores became partially or even completely blocked, the pore sizes reduced. Pores of different sizes and cementation within and on the particles were visible. ESEM findings also showed that pore shapes were not always circular as is assumed in MIP analyses. The results of this study add valuable insight into the time related changes in the microfabric of lime-treated soils.