Ultra-high performance concrete(UHPC)was prepared by using manufactured sand(MS)which is recycled from tunnel waste to substitute traditional river sand(RS).The influence of different substitution rates on workability,dry shrinkage,flexural/compressive strength and microscopic properties was studied.The results show that although the flowability has decreased to a certain extent,UHPC made by MS still has good working performance.The corresponding compressive/flexural strength are optimal when the MS substitute is 40％.The microscopic morphology of UHPC is significantly affected by MS.With the increase of MS,the micro-voids and cracks of UHPC gradually increase.The rough surface and irregular edges of MS are more conducive to establishing a connection with cement paste.Meanwhile,the irregular edge structure produces an interlocking effect between MS particles,which further enhance the bonding property between cement paste and aggregate.However,the microstructure of the interfacial transition zone between the steel fiber and MS is relatively loosen,and contains many micro-voids,which makes this area a weak bridging ability,resulting in a decrease in the overall flexural strength.In general,it is an effective strategy to replace traditional river sand to prepare UHPC by MS from tunnel waste.
维普
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