Construction Of Multiple Conductive Pathways In Cement Composites And The Performance Investigation

With the development of modern civil engineering,the intelligence of concrete structures has gradually become a significant development trend.At the same time,the development of nanotechnology and nanomaterials has brought new vitality to the concrete industry.Based on this,this paper investigates the effects of the introduction of carbon nanomaterials in cementitious materials on the mechanical properties,water-mediated transport properties,thermal conductivity and electrical conductivity of cementitious materials,starting from typical one-dimensional(carbon nanotubes,CNTs)and two-dimensional(graphene)carbon nanomaterials.On this basis,the effects of silica-ash pre-dispersed carbon nanomaterials on the properties of cementitious materials were investigated,as well as a comparative study of the effects of binary compounding of carbon nanomaterials with macroscopic carbon fibres on the properties of cementitious materials.The main research contents of this paper are as follows.(1)The effects of typical one-dimensional(CNTs)and two-dimensional(graphene)carbon nanomaterials on the properties of cementitious materials were investigated.The results showed that the amount of CNTs alone should not exceed 0.6%,and the efficiency of the improvement of flexural strength was significantly better than that of compressive strength.When the amount of CNTs exceeds 0.9%,its introduction has a negative effect on the water absorption of mortar,while it has a significant enhancement on the thermal conductivity.The percolation threshold of single-doped CNTs ranged from about 0.9-1.5%.The introduction of 0.5% graphene was beneficial to the development of the early strength of mortar,while the resistivity of mortar specimens doped with 0.5-1.5% graphene alone could be reduced by 3-4 orders of magnitude.(2)The effects of silica fume pre-dispersed CNTs and graphene on the properties of cementitious composites were investigated.The results showed that the flexural strength of mortar with 10% silica fume pre-dispersed CNTs was improved by 15-50%.The use of 10%dispersed 1.5% CNTs significantly reduced the water absorption of the cement mortar;meanwhile,its thermal conductivity was increased by a small amount of about 10%.The use of silica fume pre-dispersed CNTs can significantly reduce the resistivity of mortar specimens(by up to 8 orders of magnitude).The resistivity of mortar specimens with 10% silica fume predispersed with graphene reached the lowest value.(3)Using 10% silica fume pre-dispersed conductive phase was preferred,and the effect of the binary compounded conductive phase on the performance of the cement mortar was investigated.The results show that to balance the mechanical,electrical and thermal conductivity of cementitious materials,the optimal ratio is 0.5% graphene combined with 0.6%CNTs.Binary compounding of carbon fibres and carbon-based nanomaterials can reduce the resistivity of mortar specimens by ～8 orders of magnitude;and the effect of binary compounding of 0.1% carbon fibers and CNTs is obviously due to the combination of binary compounding of carbon fibers and graphene,it is suggested that the CNTs and carbon fibers The optimal combination is 0.1% carbon fiber combined with 0.3% CNTs.