Long-Term Mechnical,Self-Healing And Impact Performances Of Concrete With Nanofillers

Nano technology has promoted the strength and toughness development of cement-based materials.Reactive Powder Concrete(RPC)is a kind of material with high strength,high durability and dense microstructure.In this thesis,Nano-Silicon Dioxide(NS),Nano-Zirconium Dioxide(NZ),and Nano-Titanium Dioxide(NT)were incorporated into RPC to improve the properties of RPC.The effects of nano-fillers on mechanical strength,self-healing and impact properties of RPC cured for 28 d,90d and 360 d were investigated.Main results were summarized as follow:1.RPC with 0%.1% and 3% nano-fillers(NS,NZ and NT)were prepared.The compressive strength,flexural strength,microstructure and hydration degree of composites were analyzed.The research results showed that the flexural strength and compressive strength of the composites increased significantly after 28 days.The incorporation of nano-fillers would condense the microstructure of composits and reduce the preferred orientation of calcium hydroxide.2.RPC with 0% and 3% nano-fillers(NS,NZ and NT)were prepared.The self-healing ability of such specimens in water and in air was investigated.The results of the study showed that for flexural strength,composits prepared with NS and NZ obtained the best self-healing ability in water and in air,respectively.For compressive strength,the composits prepared with NS presented the best self-healing ability both in water and in air.In general,the incorporation of nano-fillers was able to improve the self-healing ability of RPC.3.The impact performances of RPC containing 0%,1% and 3% nano-fillers(NS,NZ and NT)were investigated via pendulum impact test and Split Hopkinson Pressure Bar(SHPB)test.For pendulum impact test,the impact toughness of composites with nano-fillers was higher than that of the control group.When the amounts of nano-fillers incorporated were equal,the order of impact toughness of specimens from large to small was: RPC with NS,RPC with NZ,and RPC with NT.After SHPB tests,it could be seen that the dynamic compressive strength of PRC with nano-fillers had a significant strain rate effect.The dynamic compressive strength and dynamic impact toughness of all composits were improved,but the strain rate sensitivities of them were reduced.