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Waste plastics may be an environmentally friendly alternative to natural aggregates for concrete manufacture. However, the inferior bond strength between waste plastic aggregates and cement matrix greatly limits the uses of waste plastics for engineering designs and applications. Herein, ethylene–vinyl acetate (EVA) and nanosilica (nS) were jointly employed to enhance the matrix-aggregate interactions in cementitious composites with recycled waste plastics (RWPs). Waterproof properties of the cementitious composites with EVA and nS hybrids were measured. A non-destructive test using micro-focus X-ray computed tomography (µ-XCT) with contrast enhancing technique followed by microstructural tests (SEM/BSE and EDS) were conducted to in-situ trace liquid migration in the composite specimens. The single addition of EVA into the cementitious composites increased the porosity and depressed the compressive strength, but greatly decreased the water sorptivity by nearly 50 %. The organic–inorganic (EVA-nS) hybrids enhanced the recycling potential of the waste plastics in terms of the mitigated strength reduction and improved waterproofing performance. The coupled polymerization of EVA and nanofilling of nS effects were resolved to account for the recyclability improvement. The findings would shed light on design and fabrication of cementitious materials towards large scale recycling methods and technologies of waste plastics.