Toxicity Characteristics and Heavy Metals Leachability of Self Compacted Concrete Containing Fly Ash and Bottom Ash as Partial Cement and Sand Replacement

Abstract

This research aimed to examine the toxicity characteristics of self-compacted concrete (SCC) containing fly ash (FA) and bottom ash (BA) as a partial replacement of ordinary Portland cement and fine aggregate. In particular, the other objective was to identify the heavy metals leaching nature of FA and BA in SCC as well as to determine their possible use as construction materials. FA and BA derived from the phase of combustion in coal-fired power plants. It contains heavy metals within their compositions. SCC mixtures were prepared to have various percentages of FA (substitution of cement) and BA (substitution of sand) of 0, 10, 20, and 30% respectively for subsequent experiments. Several investigations were performed out, such as the characterization of the main composition and heavy metals of the materials through X-Ray Fluorescence (main composition and heavy metal characterization of the raw materials), the compressive strength test, the Toxicity Characteristics Leaching Procedure (TCLP) and the Synthetic Precipitation Leaching Procedure (SPLP). Results showed that SCC containing FA and BA replacement had obtained compressive strengths of a similar range or higher than the control SCC (without any replacement of FA and BA). Sample FA10BA10 or 10% substitution of FA and BA recorded the highest compressive strength value at 58.07 ± 0.50 MPa. From the results of TCLP and SPLP, it founded that the inclusion of ashes up to 30% was safe as the concentration of heavy metal leaching did not surpass the concentration of pollutants for toxicity characteristics. In conclusion, this research suggests that the disposal and use of FA and BA as a promising replacement of construction materials may be used to minimize their environmental issues, improve efficiency and reduce the cost of production of SCC in the future.