The massive accumulation of waste PET plastic (WP) and coal gangue (CG) would induce a series of environmental problems such as causing soil and water pollution. For reducing the environmental pollution induced by these two wastes, this study attempts to utilize the combination of WP and CG into cement-based materials. Cement mortars incorporated with fine waste plastic (FWP) replacing part of sand and concrete blended with CG and coarse waste plastic (CWP) as part of coarse aggregate were prepared and their work-ability, mechanical strengths, dynamic elastic modulus (DEM), chloride ion permeability, hydration and microstructures were systematically investigated. In addition, metakaolin (MK) as a kind of active admixture was added into mortar or concrete and its effect of MK on the property of cement mortar or concrete was evaluated. The results show that the strengths of cement mortars containing various level of FWP decrease with increase of FWP and CG level. The mechanical strengths of concrete containing MK and 25-100 % CG and CWP are appropriate at different ages. Although the strengths of concrete blended with MK and wastes aggregate are lower than that of concrete without wastes, it is obviously higher than that of concrete only containing wastes but not MK. Its slump of fresh concrete significantly declines with CWP and CG contents growth. The coulomb electric flux and chloride migration coefficient of concrete at 28d generally increase with CG and CWP level, which indicates a declined tendency of resistance to chloride ion penetration. Its DEM for concrete measured with ultrasonic testing method slightly decrease with rise of CG and CWP content (25-100 %) and can give a basic prediction of strengths and chloride ion permeability. Hydration and microstructures tests including TG/DTA, MIP and SEM/EDS demonstrate that the pozzolanic reaction of MK can result in more gels generated and strengthen the ITZ between WP or CG and cement paste thus evidently improving its mechanical and durability of concrete when compared to the reference specimen without MK. Although the properties of concrete blended with CG and CWP as part of coarse aggregate are inferior to pure natural gravel contained concrete, its strengths and resistance to chloride ion permeability can achieve requirements of engineering structures.