The water permeability properties of re-vibrated lightweight concrete

Re-vibration of sequential layers of relatively deep structural members after a particular time harms the strength and water permeability properties of the concrete. The harmful effects can be observed in lightweight concrete due to the floating tendency of lightweight aggregate. In this experimental study, the influence of adding retarder plasticizer and silica fume on water permeability properties of re-vibrated lightweight concrete was investigated. The effects of re-vibration at different time lags on compressive strength and permeable voids ratio were studied. Absorption, sorptivity, and water penetration depth under pressure were also studied. Results show that the addition of a retarder increased the compressive strength and reduced the permeability for all mixes, even though the mixes were re-vibrated before the final set of the cement. Similar effects were found in mixes that contained silica fume as partial replacement of cement, except the sorptivity properties of concrete when compared with the control mixture. A linear relationship between permeable voids and water absorption was set.