Replacing micro-reinforcing fibers with carbon nanotubes(CNTs)is beneficial for improving the impact properties of ultra-high performance concrete(UHPC);however,the weak wettability and dispersibility of CNTs and the weakly bonded interface between CNTs and UHPC limit their effectiveness as composites.Therefore,this study aims to enhance the reinforcement effect of CNTs on the impact properties of UHPC via functionalization.Unlike ordinary CNTs,functionalized CNTs with carboxyl or hydroxyl groups can break the Si-O-Ca-O-Si coordination bond in the C-S-H gel and form a new network in the UHPC matrix,effectively inhibiting the dislocation slip inside UHPC matrix.Furthermore,functionalized CNTs,particu-larly carboxyl-functionalized CNTs,control the crystallization process and microscopic morphology of the hydration products,significantly decreasing and even eliminating the width of the aggregate-matrix interface transition zone of the UHPC.Moreover,the functionalized CNTs further decrease the attraction of the negatively charged silicate tetrahedron to Ca2+in the C-S-H gel,while modifying the pore struc-ture(particularly the nanoscale pore structure)of UHPC,leading to the expansion of the intermediate C-S-H layer.The changes in the microstructures of UHPC brought about by the functionalized CNTs signif-icantly enhance its dynamic compressive strength,peak strain,impact toughness,and impact dissipation energy at strain rates of 200-800 s-1.Impact performance of UHPC containing a small amount of carboxyl-functionalized CNTs(especially the short ones)is generally better than that of UHPC containing hydroxyl-functionalized and ordinary CNTs;it is even superior to that of UHPC with a high steel fiber content.

Jialiang Wang;Sufen Dong;Sze Dai Pang;Xun Yu;Baoguo Han;Jinping Ou

School of Civil Engineering,Dalian University of Technology,Dalian 116024,China;School of Transportation and Logistics,Dalian University of Technology,Dalian 116024,China;Department of Civil and Environmental Engineering,National University of Singapore,Singapore 117576,Singapore;Department of Mechanical Engineering,New York Institute of Technology,New York,NY 11568,USA

工程（英文）

[1]Jialiang Wang;Sufen Dong;Sze Dai Pang;Xun Yu;Baoguo Han;Jinping Ou-.Tailoring Anti-Impact Properties of Ultra-High Performance Concrete by Incorporating Functionalized Carbon Nanotubes)[J].工程（英文）,2022(11):232-245

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