Impact of fluidized bed fly ash on strength development of self-compacting concrete

Abstract

The use of self-compacting concrete (SCC) instead of traditional vibrated concrete has many advantages, which are most evident through the increased efficiency of SCC concrete under the influence of the environment. However, its use requires careful planning of concrete works and careful optimization of concrete mix design. SCC usually includes large amount of fine particles which ensure cohesiveness of the mixture and provide enough excess paste which is necessary for achieving adequate flow properties. When pulverized coal fly ash is used as a fine mineral additive, its spherical particles reduce water demand, and slow pozzolanic reactions reduce permeability and this leads to increased durability. Nowadays, pulverized coal combustion technology is being replaced by combustion in a circulating fluidized bed, which is characterized by lower energy consumption. Circulating fluidized bed fly ash particles are irregularly shaped and differ in chemical composition from pulverized coal fly ash. In this paper the possibility of designing SCC with the addition of circulating fluidized bed fly ash is being investigated. SCC mixes with different amounts of fly ash were designed and its properties in the fresh state were tested using slump-flow, J-ring and L-box measurements. Compressive strength was tested in the period from 2 days to 90 days to evaluate the effect of circulating fluidized bed fly ash on strength development.