Identification of admixture for pelletization and strength enhancement of sintered coal pond ash aggregate through statistically designed experiments

•Sintered aggregate using pond ash from lignite and bituminous coal source.•Identification of admixtures and its dosage through design of experiments.•Clay, bentonite and kaolinite as binders enhance the strength of aggregate.•Use of calcium hydroxide with clay binder enhanced pelletization efficiency.•Use of borax with clay binders enhanced the strength of aggregate.

Statistically designed experiments using Response Surface Methodology have been undertaken to identify the parameters influencing manufacturing process and properties of aggregate using coal pond ash (generated from bituminous and lignite coal sources). Based on the preliminary studies, Ca(OH)2 and borax have been identified as pelletization and strength enhancing admixture respectively. Pelletization efficiency of bituminous and lignite pond ash increased with an increase in binder and Ca(OH)2 dosage to 20–98% and 50–98% respectively, with proportionate quantity of water. Sintering has been used as a hardening method with temperature range of 900 °C and 1100 °C for a duration range of 45–120 min. Phase composition and sintered microstructure of aggregate has been reported using X-ray diffraction and scanning electron microscopy respectively. The ten percent fines value of aggregate with clay binder was 5.5 tonne as against a value of 4.5 tonne with aggregate with bentonite binder. Among the binders studied, bentonite resulted in high volume utilization of pond ash, i.e. up to 88%.