Effect of compaction delay on the strength and consolidation properties of cement-stabilized subgrade soil

Abstract

Soil compaction is a considerable construction activity to ensure safety and durability, notably in the transportation industry. Compaction delay (CD) occurs because of unpredictable cases which may be related to the climatic, environmental, and logistics reasons. Since the time delay in compaction process affects the engineering properties of the materials in road construction, the current study evaluates the effect of CD on mechanical and consolidation characteristics of cement-stabilized subgrade soil. To achieve this purpose, a set of experimental tests including standard compaction, unconfined compressive strength (UCS), and one-dimensional consolidation tests are performed. Samples are mixed with 1.5, 3, 6, and 9% Portland cement on their maximum dry density (MDD) considering different ranges of CD up to 120 min. Delayed samples show a reduction in MDD (3.46–5.43%), and UCS (11.31–37.25%) compared with those of non-delayed ones. Morphological findings from scanning electron microscope (SEM) analysis confirmed that the CD has a destructive effect on the mechanical characteristics of the soil–cement samples even in the long run. Correspondingly, delayed samples show lower secant modulus (1.81 times) rather than immediate compacted ones. Furthermore, higher CD yields mixtures with higher compression index and void ratio. Finally, laboratory test results are used to develop MDD and UCS regression models considering the CD parameter. The sensitivity analysis, based on regression models, shows that the MDD and UCS are noticeably influenced by cement content variations.