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The application of coal ash (CA) in construction industries has grown rapidly, posing risk to the environment due to heavy metals leaching from the material. This research presents a simulation of ecological risk assessment and model risk indicators (ERI) of leached heavy metals (lead (Pb), copper (Cu), zinc (Zn) and arsenic (As)) from CA (FA: fly ash and BA: bottom ash) via response surface methodology (RSM). The ERI values were based on quantified leached heavy metals from the toxicity characteristic leaching procedure (TCLP-1311) and synthetic precipitation leaching procedure (SPLP-1312). The ecological risk index ( R I ) values for TCLP were 10.27 × 100 (FA), 9.91 × 100 (BA) and 12.58 × 100 (FA + BA); whereas R I for SPLP were 10.34 × 100 (FA), 9.90 × 100 (BA) and 12.61 × 100 (FA + BA). Twenty-nine combinations of operations were evaluated based on Box-Behnken design with ERI as the response variable. The established model risk indicator (i.e., coded and actual factors) of Pb, Cu, Zn and 'As' showed significant model terms that describe their relationship very well, perfectly fit to the corresponding ERI (sum of squares = 0.4160, F value = 682,375.55) with probability of 0.01% for an F-value could occur due to noise. The optimized models were validated with error percentage of less than 5%. The established ERI models showed significant model terms and will be useful for ecological monitoring of CA application in construction industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • The physicochemical and leaching properties of FA and BA were presented. • BA and FA shown similar pozzolanic property, potential as alternative binder. • Heavy metals leaching of FA, BA and FA + BA were in permissible limits. • Pb is an indicator for existence of other heavy metals (i.e. Zn, Cu and As) Coal ash (fly (FA) and bottom (BA) ashes) contain heavy metals. This research presents physicochemical and leaching properties of coal ashes (FA, BA and FA + BA) from a Malaysian power plant. The physicochemical (X-ray fluorescence (XRF) and scanning electron microscopy (SEM)) and leaching properties (toxicity characteristic leaching (TCLP) and synthetic precipitation leaching (SPLP) procedures) of ash samples were determined. Heavy metals like lead (Pb), zinc (Zn), copper (Cu) and arsenic (As) were quantified using atomic absorption spectrometer (AAS). Leaching properties were found to complied to the standard guidelines for heavy metals. Further investigation on leaching properties is recommended for construction industry applications. [ABSTRACT FROM AUTHOR]