Effect of high salinity in grout on the performance of cement-stabilized marine clay

Abstract

Constructing a soilcrete column by injecting grout into the soil is a common method of stabilizing loose soil in coastal areas. Although tap water usually is used in the grout mixture for soil improvement projects, before the cement in grout mixture has completely set, tap water will mix with in situ saline seawater. Researchers have not previously considered the behavior of clay-cement under marine conditions, especially the effect of water salinity, on the performance of soilcrete. The goals of this study were to investigate the effect of the use of naturally saline seawater in grout preparation on the mechanical, physical and microstructural behavior of cement-stabilized marine clay. Marine clay and seawater samples were prepared along the northern shore of the Persian Gulf. Tap water as low salinity water, brackish water as medium salinity water (50% tap water and 50% seawater) and natural seawater as high salinity water were used. Specimens were prepared using the deep mixing method recommendations for laboratory soilcrete tests. Macroscopic evaluation was performed by unconfined compressive strength and indirect Brazilian tension test. The physical aspects of the plasticity of the soilcrete specimens with regard to the Atterberg limits and changes in the particle size distribution caused by cement bonding were evaluated by hydrometer testing. For the micromechanical study, SEM images were prepared from selected specimens. The results show that the use of natural seawater does not reduce the strength in comparison with tap water. Specimens containing brackish water (50% seawater and 50% tap water) showed maximum strength due to flocculation in the structure of the clayey cluster in comparison with tap water. The compressive strength ranged from 1.5 to 5 MPa for clay-cement specimens made of natural soil and seawater. The ratio of tensile strength to compressive strength of these specimens was 0.15–0.25. The results show that the unconfined compressive strength of soilcrete specimens constructed under field conditions was 30% that of specimens constructed under laboratory conditions.