Dynamic Compression Mechanical Properties And Numerical Simulation Of Phosphogypsum-based Concret

The reduction and resource utilization of phosphogypsum is an engineering problem receiving much attention in recent years,and to search an economical and efficient utilization path is the key to solving this problem.At present,phosphogypsum shows a good application prospect in the comprehensive utilization of building materials,such as phosphogypsum based mortar（PGBM）,phosphogypsum based concrete（PGBC）,etc.The current research mainly focuses on the static mechanical properties and durability of PGBCs,but there is a lack of research results on the dynamic mechanical properties of PGBCs.However,concrete structures are inevitably subjected to dynamic loads in practical applications.The studies of dynamic mechanical properties of PGBCs can provide the foundation for the popularization of PGBC to promote the large-scale application of phosphogypsum in construction materials.Therefore,in this paper,hemihydrate phosphogypsum（HPG）was used to replace part of cement to prepare phosphogypsum-based mortar and phosphogypsum-based concrete,and their dynamic compressive mechanical properties were tested by Split Hopkinson Pressure Bar（SHPB）device.In addition,a three-dimensional meso-model of phosphogypsum-based concrete was established to predict the dynamic compressive behavior of PGBC under different strain rates.The effects of hemihydrate phosphogypsum replacement rate,aggregate elastic modulus,mechanical properties of interface layer and its thickness on dynamic compressive strength were discussed.（1）The dynamic compression tests of PGBC and PGBM with different HPG replacement rates at different strain rates were carried out to analyze the effects of HPG replacement rate and strain rate on the dynamic compression properties of PGBC and PGBM.And the influence degree of the strain rate on the dynamic compression strength and elastic modulus of PGBC and PGBM was quantified.The results showed that the dynamic compressive strength and dynamic elastic modulus of PGBC and PGBM increased and then decreased with the increase of HPG replacement rate in the range of 30%～50%of HPG replacement rate.（2）The failure modes of PGBC under different strain rates were observed by high-speed camera,and the relationship between strain rate and failure mode of PGBC was analyzed.When the average strain rate increased from 136 s^-1to 432 s^-1,the failure mode of PGBC changed from the failure of large volume and massive particles to the failure of granular and massive particles,and finally to the serious damage of crushing and granular.（3）A three-dimensional meso-model of PGBC was established.Based on the meso-simulation method and dynamic compression experimental results of PGBM,the dynamic compression mechanical behavior of PGBC under different strain rates was simulated.The simulation results were in good agreement with the experimental results,and the error between the dynamic compressive strength simulation and the experimental results was basically within 10%,which verified the effectiveness of the meso-model in predicting the dynamic compression performance of PGBC.（4）The influences of HPG replacement rate,elastic modulus of aggregate,mechanical properties of interface layer and its thickness on the dynamic compressive strength of PGBC were studied by using PGBC three-dimensional meso-model.The results showed that when the HPG replacement rate increased from 30%to 50%,the dynamic compressive strength of PGBC increased first and then decreased.Secondly,the dynamic compressive strength of PGBC decreased with the increase of aggregate elastic modulus and interface layer thickness.When the mechanical properties of the interface layer were closer to the mortar,the dynamic compressive strength wass greater.