Laboratory Investigation to Optimize the Medical Waste Ash-Based Geopolymer Parameters for Flexible Pavement Base Stabilization

This current study optimizes the medical waste ash (MWA)-based geo-polymer parameters, including NaOH molarity Na2SiO3/NaOH ratio, and precursor content for pavement base stabilization. Optimization is done based on the density and compressive strength of MWA based geopolymer paste prepared by varying NaOH molarity and the Na2SiO3/NaOH ratios. The optimum NaOH and Na2SiO3/NaOH ratio determined to be 8 M and 1 respectively. By using optimum values of activator, compaction characteristics and unconfined compressive strength (UCS) were determined for crushed aggregates (CA)-MWA geopolymer specimens at various ratios (CA: MWA = 100:0, 90:10, 80:20 and 70:30). The maximum dry density (MDD) of CA-MWA geopolymer specimens increased as MWA replacement increased due to filler effect of MWA. For MWA, higher than 20% replacement MDD decreases due to the lower specific gravity of MWA compared to CA’s. The UCS of stabilized mixes increases with increasing precursor (MWA) content in the mixture up to 20%; increasing MWA content further reduces the UCS value of CA-MWA geopolymer. Therefore, the optimum ingredient of the CA-MWA geopolymer specimen at Na2SiO3/NaOH ratio 1 and CA: MWA = 80:20, which meets the 7-day UCS requirement of pavement base material for high-volume roads as per IRC: 37-2018. Other ratios of CA: MWA meets the 7 days UCS requirement of pavement base material for low-volume roads as per Ministry of Rural Development (MoRD) specifications. Moreover, CA-MWA geopolymer mixes found durable against wetting-drying cycles. The heavy metal concentration in stabilized mixes was below Toxicity Characteristic Leaching Procedure (TCLP) limits. Hence the mixes are non-hazardous to the environment.