One-Dimensional Compression of Air-Foam Treated Lightweight Geo-Material in Microscopic Point of View

Abstract

Air-foam treated lightweight geo-material (LGM), which is a mixture of dredged clay, cement, and air-foam, has been developed and utilized for various coastal structures, in order to reduce both overburden stress acting on an underground structure (tunnel, buried pipe, etc.) and lateral earth pressure acting on a retaining structure (quay wall, seawall, shore protection, etc.). In this study, one-dimensional compression behavior of the LGM was investigated in microscopic point of view with scanning electron microscope, optical CCD digital microscope, color laser 3-D profile microscope and mercury intrusion porosimetry (MIP). Though air-foam bubbles with diameters in a range of 200-500 11m are observed in the microscopic images, these sizes are not well reflected in the pore entrance size distribution by MIP because of the very small pore entrances. In MIP, there are in total three pore groups for LGM as in ranges of greater than 10 μm, 0.5-10 μm, and less than 0.5 μm. The group of the largest size corresponds to the air-foam bubbles, the one of the smallest size corresponds to the intra-pores in aggregates, and the one of the middle size corresponds to the inter-pores between the particle aggregates. When compression pressure increases, the observable airfoam bubbles primarily decreases; then the inter-pores between aggregates slightly decreases under a large compression pressure, but the intra-pores in aggregates do not decrease so much.