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Modern construction methods often result in concrete structures bearing loads at an early age, which is different from the stress condition under the standard curing in the laboratory. This study experimentally examined effects of different ages and external loads on subsequent mechanical and permeability properties of concrete, and investigated the mechanism of effect from the perspective of internal structure changes. The results show when the early age loading reaches 40% of the current concrete strength, the original internal structure of specimens will be severely damaged, reflecting significant increase in the proportion of mesopores and macropores and obvious connectivity cracks, thus making the mechanical and permeability properties deteriorate, and the earlier the applied load, the greater of this deterioration. However, when loading at 10%, the original internal structure cannot be changed greatly due to the low load level, and some parts of the original pores are even compacted rather than expanded which has little effect on subsequent mechanical and permeability properties of concrete.