This study investigates the effects of nanofillers on the interfacial transition zone(ITZ)between aggregate and cement paste by using nanoindentation and statistical nanoindentation techniques.Moreover,the underlying ...This study investigates the effects of nanofillers on the interfacial transition zone(ITZ)between aggregate and cement paste by using nanoindentation and statistical nanoindentation techniques.Moreover,the underlying mechanisms are revealed through micromechanical modeling.The nanoindentation results indicate that incorporating nanofillers increases the degree of hydration in the ITZ,reduces the content of micropores and low-density calcium silicate hydrate(LD C-S-H),and increases the content of highdensity C-S-H(HD C-S-H)and ultra high-density C-S-H(UHD C-S-H).In particular,a new phase,namely nano-core-induced low-density C-S-H(NCILD C-S-H),with a superior hardness of 2.50 GPa and an indentation modulus similar to those of HD C-S-H or UHD C-S-H was identified in this study.The modeling results revealed that the presence of nanofillers increased the packing density of LD CS-H and significantly enhanced the interaction(adhesion and friction)among the basic building blocks of C-S-H gels owing to the formation of nano-core-shell elements,thereby facilitating the formation of NCILD C-S-H and further improving the performance of the ITZ.This study provides insight into the effects of nano fillers on the ITZ in concrete at the nanoscale.展开更多
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 ...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,particularly carboxyl-fu nctionalized CNTs,co ntrol 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 structure(particularly the nanoscale pore structure)of UHPC,leading to the expansion of the intermediate CS-H layer.The changes in the microstructures of UHPC brought about by the functionalized CNTs significantly 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.展开更多
Spiky spherical nickel powder with sharp nano-tips on its surface is a kind of excellent fillers for developing pressure-sensitive cement-based composites/sensors for traffic detection,structural health monitoring,and...Spiky spherical nickel powder with sharp nano-tips on its surface is a kind of excellent fillers for developing pressure-sensitive cement-based composites/sensors for traffic detection,structural health monitoring,and border and military security.The sharp nano-tips on the surface of spiky spherical nickel particles can induce field emission and tunneling effects,which leads to the ultrahigh pressure-sensitive responses of the cement-based composites.In this paper,we systematically introduce research on nanotip-induced ultrahigh pressure-sensitive cement-based composites/sensors,with attentions to their pressure-sensitive property and sensing mechanism,pressure-sensitive characteristic model,and smart structure system for traffic detection.展开更多
Micro/meso scale modification can bring big changes in macroscale property.The addition of nanofillers makes materials strong,durable and multifunctional/smart.This paper aims at studying mechanical property,durabilit...Micro/meso scale modification can bring big changes in macroscale property.The addition of nanofillers makes materials strong,durable and multifunctional/smart.This paper aims at studying mechanical property,durability,electrical property,electromagnetic property and piezoresistivity of concrete with nano silica(NS),carbon nanotube(CNT),botryoid hybrid carbon material(BHCBM),nano graphite展开更多
基金funding offered by the National Natural Science Foundation of China(51978127 and 51908103)the Fundamental Research Funds for the Central Universities(DUT21RC(3)039)。
文摘This study investigates the effects of nanofillers on the interfacial transition zone(ITZ)between aggregate and cement paste by using nanoindentation and statistical nanoindentation techniques.Moreover,the underlying mechanisms are revealed through micromechanical modeling.The nanoindentation results indicate that incorporating nanofillers increases the degree of hydration in the ITZ,reduces the content of micropores and low-density calcium silicate hydrate(LD C-S-H),and increases the content of highdensity C-S-H(HD C-S-H)and ultra high-density C-S-H(UHD C-S-H).In particular,a new phase,namely nano-core-induced low-density C-S-H(NCILD C-S-H),with a superior hardness of 2.50 GPa and an indentation modulus similar to those of HD C-S-H or UHD C-S-H was identified in this study.The modeling results revealed that the presence of nanofillers increased the packing density of LD CS-H and significantly enhanced the interaction(adhesion and friction)among the basic building blocks of C-S-H gels owing to the formation of nano-core-shell elements,thereby facilitating the formation of NCILD C-S-H and further improving the performance of the ITZ.This study provides insight into the effects of nano fillers on the ITZ in concrete at the nanoscale.
基金the National Natural Science Foundation of China(51978127 and 51908103)the Fundamental Research Funds for the Central Universities(DUT21RC(3)039)the China Scholarship Council Foundation(202006060103)for providing funding to carry out this investigation。
文摘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,particularly carboxyl-fu nctionalized CNTs,co ntrol 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 structure(particularly the nanoscale pore structure)of UHPC,leading to the expansion of the intermediate CS-H layer.The changes in the microstructures of UHPC brought about by the functionalized CNTs significantly 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.
文摘Spiky spherical nickel powder with sharp nano-tips on its surface is a kind of excellent fillers for developing pressure-sensitive cement-based composites/sensors for traffic detection,structural health monitoring,and border and military security.The sharp nano-tips on the surface of spiky spherical nickel particles can induce field emission and tunneling effects,which leads to the ultrahigh pressure-sensitive responses of the cement-based composites.In this paper,we systematically introduce research on nanotip-induced ultrahigh pressure-sensitive cement-based composites/sensors,with attentions to their pressure-sensitive property and sensing mechanism,pressure-sensitive characteristic model,and smart structure system for traffic detection.
文摘Micro/meso scale modification can bring big changes in macroscale property.The addition of nanofillers makes materials strong,durable and multifunctional/smart.This paper aims at studying mechanical property,durability,electrical property,electromagnetic property and piezoresistivity of concrete with nano silica(NS),carbon nanotube(CNT),botryoid hybrid carbon material(BHCBM),nano graphite
