Modeling and experimental study of multiple factors on mechanical strength of iron sand modified cement mortars

•Effects of five factors on iron sand modified cement mortars (ISCM)’ mechanical strength were studied.•The influence degree of multiple factors on mechanical strength for ISCM was analyzed.•The overall mechanical strength of modified cement mortar mixed natural iron sand is the best among the three cement mortars.•New prediction models between mechanical properties and multiple factors were developed and analyzed. To figure out how multiple factors affect iron sand modified cement mortar (ISCM)’s mechanical properties, the influence of the water-cement ratio, sand-cement ratio, river sand-iron sand ratio, density, and age on its mechanical properties were analyzed by compressive and flexural tests. Then, the influence degree of multiple factors on mechanical strength is studied by gray correlation theory. The results showed that the water-cement ratio has the most significant influence on mechanical strength. Afterwards, gray target theory is applied to evaluate the mechanical strength rank of three kinds of ISCM. The results showed the overall mechanical properties of natural iron sand modified cement mortar rank the best. Finally, new prediction models for mortars’ compressive and flexural strengths are systematically proposed and compared with two existing models. The results show that the proposed models have more agreements with experimental values.