Microbial treatment of cement kiln dust for utilization in concrete

Abstract

Rapid industrialization and urbanization increases the demand of building and constructionmaterial for infrastructure development. Generation of cement kiln dust (CKD) during cementclinker manufacturing has become one of the major environmental and economical issues.Globally, cement industries generate 700 million tons of cement kiln dust every year as ameasure to control product quality and to ensure uninterrupted operation of the plant due to highalkalinity and heavy metal content, and major part of it is landfilled. In order to reduce disposalcosts utilization of CKD as construction material has become an attractive alternative to its disposal. Cement kiln dust is highly alkaline in nature which restricts its utilization in mortar and concreteas it causes crack, deformities and reduces the strength and quality of cement and concrete. Also, the alkaline leachate generated from landfilled CKD may contaminate soil, surface and ground water. So, it is necessary to monitor the alkalinity of CKD before utilization. This can be achieved by biological methods using microorganisms that requires low energy inputs, and does not produce hazardous by-products.This study presents the utilization of bacterial treated cement kiln dust in mortar and concrete, and its leachate behavior. In this study, the effect of bacterial (alkali-tolerant Bacillus strain KG1) treated cement kiln dust (after reducing the alkalinity) as partial replacement of Portlandcement (5, 10, 15, 20 and 30% w/w) on the normal consistency, setting times and hydration process of blended cement pastes, and on compressive strength at 7, 28 and 91 days of curing of blended cement mortar and concrete was investigated. Several properties such as split tensile strength, ultrasonic pulse velocity, RCPT and porosity of concrete was also studied at the age of 7, 28 and 91 days. Bacterial (isolate KG1, KG4, KG5 and KGMD1) inoculums were optimized at 0.8 O.D. for 20 days of incubation.