Effectiveness study for fly ash cement improved marine clay

Abstract

The disposal of fly ash poses increasingly difficult problems for many urbanized regions. A viable solution to the problem is reclamation of fly ash for civil engineering applications. Previous researches shown that fly ash is a potential source of construction material and soil stabilizer. Although it is one of the lowest-cost and most widely used materials in the world, cement raises many concerns for the environment and human health. Many studies have been conducted with the aim of reducing the cost of cement for soil stabilization; one option is to partially replace cement with waste materials such as fly ash. This paper presented a laboratory study on the effectiveness of fly ash cement-improved Singapore marine clay (FACC) through tests including unconfined compression, split tensile, Bender element, and isotropic compression tests. The effectiveness of FACC in soft clay treatment was discussed in detail by comparing its geotechnical properties with those of Ordinary Portland Cement-admixed clay (OPCC). Specimens with 20–100% cement content, 100–133% water content, and 7–150days curing periods were used for the FACC and OPCC experiments. The results showed that the effectiveness of FACC was dependent on both the geotechnical property values and ratios, which were related to cement content, water content, and curing period. It was found that for specimens with high cement content (50–100%) and long curing period (90–150days), the strength ratio of the FACC to OPCC specimens was as high as 70–85%. The stiffness ratio and isotropic primary yielding stress ratio were also higher than 60% at 90days. Specimens with low cement content or high water content showed low geotechnical property values and/or ratios, which indicated lower levels of effectiveness. Based on experimental observations, a new function for estimating geotechnical property ratios was proposed and then proved to be effective.