Engineering properties of marginal lateritic soil stabilized with one-part high calcium fly ash geopolymer as pavement materials

This research investigated the engineering and microstructure properties of marginal lateritic soil (MLS) stabilized with one-part high calcium fly ash geopolymer. High calcium fly ash (FA), a by-product of an electrical power plant in Thailand was used as a starting material and solid sodium hydroxide (NH) in flake form was used as an alkali activator. The influences of NH content, soaking conditions, and curing time were studied. The unconfined compressive strength (UCS), indirect tensile strength (ITS), and microstructure were investigated. Test results showed that the use of one-part high calcium FA geopolymer (OP-G) to stabilize MLS can improve the engineering properties noticeably. The samples with 20% NH content yielded the maximum 7-day UCS of 1930 kPa and 2800 kPa under soaked and unsoaked conditions, respectively, corresponding to the maximum 7-day ITS of 270 kPa and 400 kPa. The 28-day UCS and 28-day ITS of MLS samples stabilized with OP-G were higher than the 7-day UCS and 7-day ITS of samples. This indicated the continued reaction of the OP-G stabilized MLS. The 7-day soaked UCS of the stabilized MLS was higher than 689 kPa required for subbase materials according to the Department of Highway (DOH), Thailand. The total cost, cost/UCS ratio, and CO2 emission of OP-G were lower than those of two-part geopolymer stabilized MLS samples. The outcomes of this research thus support the utilization of OP-G as an alternative to Portland cement in treating MLS for use as pavement materials.