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The research on the highly efficient reutilization of mixed recycled aggregates (MRA) produced from construction and demolition waste has attracted significant attention globally. In this study, the feasibility of using 100% MRA in cement-stabilized materials was investigated. The mechanical properties and microstructures of cement-stabilized MRA (CSMRA) materials containing 100% MRA were systematically examined through unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, drying shrinkage test, X-ray diffraction analysis, mercury intrusion porosimetry, and scanning electron microscopy. Results showed that the UCS and ITS of CSMRA materials were significantly enhanced with the increase of cement content and curing age, and there was almost a linear relationship between the UCS and ITS. The failure behavior of CSMRA materials under load showed three typical stages: compaction stage, elastic stage, and yield stage. The increase of the cement content caused the drying shrinkage deformation of CSMRA to increase sharply when the cement content exceeded 4%. The microstructural analysis indicated that cement had both filling and binding effects on CSMRA materials. The strength growth with cement content and curing age was because of the constant hydration of cement minerals, producing more calcium silicate hydrate binders between aggregates. Moreover, the increasing cement content could reduce the porosity and optimize the pore structure distribution of CSMRA materials. The findings of this study demonstrate that the use of 100% MRA in cement-stabilized materials as a road base is feasible, which will significantly enhance the utilization efficiency of MRA.

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In this study, the effect of nano-SiO 2 on mechanical properties and microstructure of polymer modified cementitious (PMC) materials under 20 and 6 C was studied through strength test, X-ray Diffraction Analysis, Mercury Intrusion Porosimetry, and Scanning Electron Microscopy. Results showed that the flexural and compressive strength of cement mortar was influenced seriously by polymer especially under low temperature condition. And nano-SiO 2 was contributed to enhance the flexural and compressive strength of PMC materials at early age under 20 C while the enhancement still existed at later age under 6 C. The disadvantage of polymer on the properties and microstructure of PMC materials at low temperature was modified by nano-SiO 2 due to the increase of hydration rate of cement, the decrease of the Ca(OH) 2 (CH) orientation aggregation, the modification of pore structure, and the promotion of polymer film formation. This study provides a prospective method on the performance optimization of PMC materials. K E Y W O R D S different temperatures, microstructure, nano-SiO 2 , PMC materials