Environmental friendly technology of cold-bonded bottom ash aggregate manufacture through chemical activation

Cold bonding facilitates production of aggregate with minimum energy consumption compared to the sintered aggregate, which requires a heat treatment in the range of 1000–1200 °C. The strengthening of pelletized bottom ash in cold bonding at ambient temperature is due to the formation of CSH gel during the hydration from the chemical reaction between CaO, water and the pozzolanic character of the bottom ash. Chemical activation is done using Na2SO4 to enhance the strength of the cold-bonded aggregate by accelerating the pozzolanic reaction and formation of more ettringite. Experimental runs were designed using Central Composite Design and the properties of cold-bonded aggregate like bulk density, ten percent fines value (TPFV), porosity and water absorption were studied. It was observed that increase in binder and Na2SO4 dosages increased the strength and decreased the open porosity thereby reducing the water absorption.