Quantification of Carbon Content in cogeneration boiler waste and Its Effect on pozzolanic Reactivity

Abstract

Supplementary cementitious materials are extensively used in concrete because of the enhancement of fresh and hardened properties compared to ordinary Portland cement. Plants ingest orthosilicic acid from ground water, which is later polymerized as reactive silica in the plant cells. When bagasse and rice husk are burnt as fuel in the cogeneration boiler, reactive amorphous silica is formed because of combustion process and it is present in the residual ashes. In addition to silica, residual biomass such as sugarcane bagasse ash and rice husk ash have higher carbon content due to presence of unburnt particles and it significantly influences the pozzolanic performance of residual biomass. Furthermore, higher carbon content has adverse effects on concrete such as reduction in workability and strength. Even though, a number of earlier research studies have suggested bagasse ash and rice husk ash as an excellent pozzolanic material, still determination of carbon content using more accurate method is not reported in the existing literature. A detailed study on the presence of carbon content in the residual biomass is imperative to achieve maximum reactivity as well as superior alternative cementitious material. In this paper, carbon content in the residual biomass was determined using more appropriate methods and conventional loss on ignition method. Results from the study showed considerable difference in carbon content between sophisticated method and loss on ignition method. Influence of loss on ignition on pozzolanic performance and workability of residual ash blended specimens were investigated and compared with control specimens. Moreover, fast pyrolysis and detailed kinetic model approach was found to be more precise as compared to loss on ignition method.