Dynamic Response And Damage Mechanism Of Novel Geopolymer Based High-performance Concrete Slabs Under Blast Loading

In the world today,the speed of globalization is accelerating and the exchanges between countries are becoming more and more frequent.Various explosions and terrorist attacks triggered by geopolitical and religious factors occurred frequently.In addition,accidental explosion accidents often occurred due to carelessness or negligence in life and production,such as fuel/gas leakage,improper production and storage of hazardous chemicals.These explosion accidents will cause catastrophic damage,including building collapse,huge property losses and casualties.Therefore,it is of great social and economic significance to carry out the dynamic response and protection design of structures under explosive loads.On the other hand,geopolymer concrete has excellent mechanical properties,fire and high temperature resistance;it could use slag or construction waste as raw materials,which greatly reduce the loss of natural resources and mitigate environmental pollution,and it was expected to become a substitute for Portland cement concrete.However,few scholars have studied the dynamic response of geopolymer concrete structure under blast loads.In order to reveal the dynamic response of a new type of geopolymer concrete slab under blast loads,this study first proposed a novel of light-weight and high-strength geopolymer based high-performance concrete sandwich slab,and studied the dynamic response and failure modes of sandwich slab under contact explosion and multiple blast loadings by experimental and numerical.In addition,the blast resistance performance of steel wire mesh reinforced geopolymer based high-performance concrete slab under multiple blast loadings was also studied.The main research works were as follows:(1)A novel geopolymer based high-performance concrete sandwich slab with light weight and high-strength was proposed,which was composed of top geopolymer based highperformance concrete layer(top G-HPC layer),bottom geopolymer based high-performance concrete layer(bottom G-HPC layer)and metallic tube core layer(MTC).And its blast resistance performance under the contact blast loading was tested.The contact blast tests of seven sandwich slabs and a reinforced concrete slab were carried out to study the influence of the shape and material of metallic tube in MTC and the thickness of top / bottom G-HPC layer and MTC layer on the blast resistance performance of sandwich slabs.The results showed that the sandwich slab with rectangular steel tube in MTC layer has better blast resistance than that with circular steel tube or circular aluminum alloy in MTC layer;the MTC layer can absorb more blast energy by using its large deformation,and can effectively resist the high-speed flying fragments generated by the top G-HPC layer;the thickness of the bottom G-HPC layer has a significant effect on the blast resistance of sandwich slabs.Compared with reinforced concrete slab,the novel sandwich slab has better blast resistance.(2)The refined numerical simulation of sandwich slabs under contact blast loading was established by using the finite element software LS-DYNA,and the accuracy of the finite element model was verified by comparison with the experimental results;based on the verified finite element model,the effects of key parameters(including boundary conditions and explosive equivalent)on the failure modes of sandwich slabs were analyzed.The results showed that the boundary conditions had slight effect on the damage of the top G-HPC layer and the MTC layer of sandwich slabs,but had some effect on the damage of the bottom G-HPC layer.With the increase of explosive equivalent,the damage degree of sandwich slab also increases.(3)The multiple-blast loading test of sandwich slabs was carried out(the first blast load was 1.6 kg @ 0.4 m and the second blast load was 3.2 kg @ 0.4 m).The results showed that sandwich slab has excellent blast resistance performance under multiple blast loading,and can absorb a large amount of blast wave energy by using the deformation of MTC layer.Based on the test results,a refined finite element model of sandwich slab under multiple blast loading was established by using the finite element software LS-DYNA,and the accuracy of the finite element model was also verified;on this basis,the effects of boundary conditions and steel tube spacing on the failure mode of sandwich slabs were analyzed.(4)Multiple-blast loading tests were carried out on the steel wire mesh reinforced geopolymer based high-performance concrete protective slab and the steel wire mesh reinforced geopolymer based high-performance concrete protective slab covered with ultra-high molecular weight polyethylene fiber reinforced cloth(UHMWPE FRC).The results showed that the steel wire mesh can improve the ductility of the geopolymer based high-performance concrete slab and enhance its resistance to multiple blast loading,and the use of steel wire mesh to strengthen the geopolymer based high-performance concrete slab can effectively reduce the high-speed concrete fragment.Under four continuous blast loads,the steel wire mesh reinforced geopolymer based high-performance concrete slab covered with UHMWPE FRC also showed excellent multiple blast loading resistance.(5)A refined finite element model of steel wire mesh reinforced geopolymer based highperformance concrete protective slab under multiple blast loading was established by using the finite element software LS-DYNA,and the accuracy of the finite element model was verified.The parameters of steel wire mesh reinforced geopolymer based high-performance concrete protective slab under multiple blast loading were analyzed.The effects of boundary conditions,length width ratio,layers and arrangement of steel wire mesh,explosive equivalent and UHMWPE FRC on its dynamic response and failure mode were studied.The results showed that the boundary conditions,the length width ratio,the number and arrangement of steel wire mesh,and the explosive equivalent all have significant effects on the failure mode of steel wire mesh reinforced geopolymer based high-performance concrete protective slab.Under the same multiple blast loading,the blast resistance of the steel wire mesh reinforced steel wire mesh reinforced geopolymer based high-performance concrete protective slab covered with UHMWPE FRC at the bottom surface was better than that of the protective slab covered with UHMWPE FRC at the top surface.