Abstract
•Geopolymerization of eggshell powder and flyash at ambient temperature.•Potential application in sustainable sub-base/subgrade construction.•Mixture of sodium silicate and sodium hydroxide was used as alkaline activator.•10 M sodium hydroxide concentration was used in the alkaline activator solution.•Evaluation of strength with respect to activator ratio and precursor ratio.
The eggshell powder (ESP) rich in calcium content is a poultry waste product, generated from grinding waste eggshells. Flyash (FA) is an industrial waste product, generated from the combustion of coal in power plants. Currently, disposal of these kinds of waste products is a global concern. Utilization of waste products as a sustainable construction material can solve many problems related to disposal. The current study aims to determine the possibility of utilization of calcium-rich eggshell powder and industrial waste flyash through geopolymerization, to give a sustainable construction material. Mixtures of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) with fixed 10 M concentration were used as an alkaline activator solution. Modified Proctor test, unconfined compressive strength, and split tensile strength test were performed to analyze the behavior of mechanical strength. Three precursor ratios (ESP:FA) – 30:70, 50:50, and 70:30 and three activator ratios (Na2SiO3/NaOH) – 0.5, 1, and 2 were adopted. The geopolymer composites were cured at ambient temperature (25 ± 2 °C) for 7 days, 28 days, and 56 days to assess the long term strength development. Geopolymer composite 50ESP:50FA with activator ratio 2 was found optimum for unconfined compressive strength and split tensile strength. The optimum composites found in the research have the potential to be employed in sub-base/subgrade application as a sustainable construction material made from waste-by-product.