Research On Compressive Strength Of Desert Sand Concrete Containing Interfacial Phases After Elevated Temperature

Nowadays,high-rise buildings are densely distributed.When a fire occurs,due to the "chimney effect",it makes the rescue in high-rise buildings become difficult,and causes serious losses of personnel and property.Due to sand resources are facing an increasingly depleted dilemma,compressive strength is the most basic mechanical property of concrete,and the interface phase is the weakest structural layer in concrete.Therefore,the compressive strength study of the desert sand concrete(DSC)with interfacial phase after elevated temperature has the great significance for the analysis of the mechanical properties of the DSC after elevated temperature,the DSC engineering application and the protection of the environment sustainable development.This paper regarded the DSC as a three-phase composite material,which was composed of coarse aggregate,desert sand mortar and interface phases.The constitutive parameters of the coarse aggregate were taken from relevant literature.The desert sand mortar parameters were mainly obtained through the compression test of the desert sand mortar after elevated temperature,and the interface phase simulation parameters were calculated and determined based on the desert sand mortar test data.A DSC numerical model after elevated temperature was established,and the interface phase was taken into account.ANSYS was used to simulate the uniaxial compression failure process of the DSC after elevated temperature.The main contents were as follows:1)The uniaxial compression performance of desert sand mortar after elevated temperature was studied,and the stress-strain curve of desert sand mortar was obtained.The fitting relationship between temperature,desert sand replacement rate and related mechanical parameters(peak stress,peak strain,elastic modulus and Poisson’s ratio)can be established;and the constitutive equation of desert sand mortar under uniaxial compression after elevated temperature can be given.The results can provide a source of parameters for subsequent numerical simulations.The test also analyzed the appearance characteristics of the desert sand mortar specimens and the compressive failure of the mortar under different temperatures and different desert sand replacement rates.2)Using the test model as the reference object,a numerical model of the DSC after elevated temperature was established based on the three phases,which were the coarse aggregate,desert sand mortar and interface.The simulation results were compared with the test results of the DSC after elevated temperature.The result showed that the overall error was-1.59%-4.05%,and the concrete failure model obtained by simulation and experiment was basically the same,which verified the feasibility of the model.3)The numerical model of DSC was established after elevated temperature to study the desert sand replacement rate,specimen size,interface phase thickness,interface phase strength,coarse aggregate volume content and coarse aggregate particle size(minimum particle size,intermediate particle size,and maximum particle size)on the compressive strength of DSC after elevated temperature.The results showed that the use of desert sand to completely replace medium sand cannot obtain the best results.When the replacement rate was 40%,the compressive strength was the highest.When the size of the specimen increased,the compressive strength decreased continuously and showed a negative correlation.There was a negative correlation between the interface phase thickness and the DSC compressive strength after elevated temperature.DSC compressive strength was increased with the increase of interface phase strength.For secondary coarse aggregate,it has a significant impact on DSC compressive strength.When coarse aggregate volume content increased from 35%to 65%,the relationship curve between compressive strength and volume content increased first and then decreased.The compressive strength was optimal when the volume content was 45%.The influence of the minimum particle size and the maximum particle size of coarse aggregates was basically the same.As the aggregate size increased,the compressive strength was decreased.With increasing the median particle size of the coarse aggregate,the compressive strength increased firstly and then decreased.