Strength development of recycled concrete aggregate stabilized with fly ash-rice husk ash based geopolymer as pavement base material

Abstract

This research studies on the usage of fly ash (FA) and rice husk ash (RHA) based geopolymers for improving the compressive strength of recycled concrete aggregate (RCA) to be a lightweight stabilised pavement base material. A mixture of FA from coal-burning power plants and RHA from rice milling process was used as a precursor while the liquid alkaline activator (L) was a mixture of sodium hydroxide solution (NaOH) and sodium silicate solution (Na2SiO3). Various RHA/FA ratios (between 100/0 and 0/100) and NaOH/Na2SiO3 ratios (between 50/50 and 100/0) were used in this study. The FA-RHA-geopolymer stabilised RCA samples, at each NaOH/Na2SiO3 ratio were prepared at the optimum liquid alkaline activator content (OLC) for unconfined compressive strength (UCS) tests. The UCS tests were conducted after 7, 28 and 60 days of curing. The test results indicate that the UCS of FA-RHA-geopolymer stabilised RCA increases as the RHA/FA and NaOH/Na2SiO3 ratios decrease and the curing time increases. Based on the Department of Highways, Thailand, the 60/40 RHA/FA and 60/40 NaOH/Na2SiO3 mix proportions are recommended for both low and high traffic volume roads with a low unit weight of 21.1 kN/m3. This research study confirms the potential of FA-RHA-geopolymer stabilised RCA as an alternative stabilised road base material.