FLY-ASH-BASED GEOPOLYMER AS STABILIZER FOR SILTY SAND EMBANKMENT MATERIALS

Abstract

Fly ash in the recent decades has become abundant resulting in the improper waste disposal.
However, it is also known to be a precursor to the process of geopolymerization which is categorized under
waste utilization. Geopolymer has become known for being on par with cement and other chemical
stabilizers in terms of strength. It has been used in numerous studies focusing on concrete and on soil
stabilization. This study proposes the use of fly-ash-based geopolymer as a stabilizer for silty sand
embankment material wherein the process of synthesizing geopolymer is through the dry-mix method. The
dry-mix method is another way of producing geopolymer, requiring the aluminosilicate precursors and alkali
activators to be in its dry state, and adding water to the dry-mix would result in geopolymerization. The
geopolymer was applied on Silty Sand to verify its reaction with the soil and to obtain the effective mix that
would enable the soil to be stabilized for embankment use. The effectiveness of this method in soil
stabilization was tested through the following tests, the CBR Test (ASTM D1833) and the UCS Test (ASTM
D2166). Results have shown improvements of the geopolymer-stabilized soil in terms of the CBR index and
the UCS value. The effective geopolymer concentration was found to be at 30% geopolymer concentration
which produced the highest increase for the stabilized soil with a maximum CBR index of 34.32% and a
maximum UCS value of 1349.74 kPa.