A systematic research on foamed concrete: The effects of foam content, fly ash, slag, silica fume and water-to-binder ratio

In this study, the effects of foam content, different dosages of fly ash, slag, silica fume and water-to-binder ratio on a series of properties of foamed concrete were examined. In total, 39 mixes of foamed concrete were prepared and corresponding fluidity, mechanical strength, water absorption and resistance against freezing-thawing cycles were investigated. Besides, microstructural and mineralogical characterizations were also conducted. Further, the relationship between compressive strength and dry density was also described. Experimental results showed that an optimal content of fly ash exists for obtaining the highest fluidity of foamed concrete, which was 50% in this research. Except foam content, all other factors led to increased mechanical strength and decreased water absorption first and then lower mechanical strengths but greater water absorption were observed. Silica fume seems to have a stronger influence on the properties of foamed concrete compared to other factors due probably to its finer particle sizes and pozzolanic reactivity. Finally, the foamed concrete prepared displayed higher mechanical strength with light weight compared to the findings from other literature, which is possibly associated with the higher stability of pores and/or voids introduced, fewer interconnected pores and participation of various mineral admixtures. For the durability performance, foam content at 28% or higher, fly ash content at 60% and water-to-binder ratio of 0.60 all led to structural damages of specimens after 50 cycles of freeze–thaw actions.