Investigation On The Resistance Of Geopolymer-Based Ultra-High Performance Concrete Slabs Under Contact Explosions

With the rapid development of economy and the gradual advancement of modernization,a series of important infrastructures such as cross-sea bridges and high-speed railways have emerged.On the other hand,blast and impact accidents occur frequently,and how to ensure the safety and reliability of engineering structures has become a key problem that the researchers need to solve urgently.Under blast and impact loading,normal strength concrete are prone to brittle failure.With the development of concrete materials,ultra-high performance concrete(UHPC)is a promising material to improve the blast and impact resistance of protective engineering because of its ultra-high mechanical properties and excellent durability.Furthermore,geopolymer-based ultra-high performance concrete(G-UHPC)is a new type of green UHPC material that not only has ultra-high strength and resistance comparable to UHPC but also has less impact for the natural environment,which is in line with the national strategic positioning of green and low-carbon concrete materials.At present,the existing research results show that there are relatively few experimental and numerical studies on the blast and impact resistance of G-UHPC materials,and the understanding of their damage mechanisms is relatively insufficient.Therefore,the preparation and mechanical properties of G-UHPC materials are reviewed in this paper.Subsequently,the damage mode and anti-explosion performance of G-UHPC slabs under contact explosion are systematically studied through experiments,numerical simulation and parameter analysis.The main research works and innovative achievements are as follows:(1)The material composition and preparation method of G-UHPC are briefly introduced.Then,the static mechanical properties of G-UHPC and the dynamic mechanical properties of GPC are summarized in detail,and the mathematical formulas between uniaxial compressive strength and splitting tensile strength,flexural strength and elastic modulus,and the strain rate effect formula of GPC are fitted.(2)The contact explosion tests of ordinary G-UHPC slabs,steel wire mesh,steel fibre,and polyurea coating reinforced G-UHPC slabs were designed and carried out.The contact explosion tests were set in two working conditions: 150 mm thick G-UHPC slab under the action of 0.4 kg TNT and 200 mm thick G-UHPC slab under the action of 1.0 kg TNT.The test results show that: 1)steel wire mesh and steel fibre can effectively improve the resistance of explosion performance of G-UHPC slabs;2)the polyurea coating can fully wrap the concrete fragments caused by the blast loading,thus greatly reducing the secondary damage.(3)Based on a series of mechanical property tests of G-UHPC materials,the dynamic constitutive model parameters suitable for G-UHPC are calibrated,which provides support for numerical simulation of the dynamic response of G-UHPC slabs under contact explosion.(4)The numerical model of the G-UHPC slab against contact explosion is established,and the modified G-UHPC dynamic constitutive model is applied to the numerical simulation.The consistency between the experimental and simulation results shows that the calibrated dynamic constitutive model and algorithm are suitable for predicting the dynamic response of the G-UHPC slab under contact explosion load.Combined with the stress wave propagation theory and numerical simulation results,the strengthening effect of steel wire mesh and steel fibre on the contact explosion load of G-UHPC slab is revealed.(5)Using the effective numerical model,the parameter studies of G-UHPC slabs against contact explosion were conducted,and the corresponding empirical formula was fitted to predict the damage mode of G-UHPC slabs under contact explosion.Therefore,the empirical formula can provide an effective reference for the design of G-UHPC slabs under contact explosion.