The future construction industry will demand for sustainable concrete, either by recycling or direct incorporation of industrial by-products for effective solution of ecological concerns. The paper covers, outcomes of an investigation conducted to assess the ‘performance of iron slag (0–30 %) recycled aggregate concrete (ISRA) with different levels of recycled (0–100 %) concrete aggregates (RCA)’ using destructive (DT) ‘(compressive, split-tensile and flexure strength)’ and non-destructive ‘(pulse velocity, electrical resistivity and rebound hammer)’ testing (NDT). The strength characters were evaluated to develop statistical regression and grey co-relations. ISRA concrete resulted majorly in decrease of pulse velocities, electrical resistance (up to 28 %) and rebound numbers (by 10) at higher alteration levels. The correlation coefficients were evaluated using linear regression and grey analysis. The grey correlations resulted in visible variations, indicating disparity in magnitude of ISRA concrete. The higher regression (>0.75) and grey coefficients (GRG>0.8) postulates higher probability of accuracy, successfully validate the outcomes.