Properties of concrete incorporating alum sludge in different conditions as partial replacement of fine aggregate

Abstract

Water treatment plant generates alum sludge as waste during the process of treating drinking water for human consumption. Notwithstanding the benefits of treating water, there are still problems associated with the disposal of waste generated from the water treatment plant after the treatment process. Studies have shown that the conventional disposal method is associated with environmental hazards; and there is a need to derive more sustainable method of alum sludge disposal. This study focused on investigating the properties of concrete incorporating alum sludge as a partial replacement of fine aggregate. The alum sludge used in this study as replacement of fine aggregate was prepared in two ways; oven-dried under temperature 105 °C and 300 °C heated alum sludge (heated in the furnace). Both alum sludge (oven-dried alum sludge, 300 °C heated alum sludge) was crushed/grinded to obtain a maximum particle size of 65 µm and used to replace fine aggregate in different proportions (0%, 5%, 10% and 15%). The produced concrete was tested for fresh properties; and then cured at 7, 28, 56, 90 and 180 days to test for hardened and durability properties. The results from the study showed that oven-dried alum sludge and 300 °C treated alum sludge produce a workable mix and can be used as replacement of fine aggregate with optimum replacement content of 10%. Both alum sludge improved the density of the concrete, strength properties of the concrete and concrete durability. At 15% replacement content of fine aggregate with oven dried and 300°C heated alum sludge, yield a decrease in workability and strength properties, with poor durability properties.