| This paper adopts the split Hopkinson pressure bar(SHPB)on the rape straw ash concrete to study the dynamic mechanical properties under uniaxial compression.First,the single factor test is carried out on the ash content and the loading pressure of rape straw ash concrete,to explore the influence rule of both on dynamic performance of concrete;then the orthogonal test of three factors and five levels is carried out with water-cement ratio,ash content of rape straw ash and loading pressure as variables;the stress-strain curves of concrete specimens under different combinations of factor levels are obtained.The influence of different factors on the dynamic mechanical properties of rape straw ash concrete is discussed according to the analysis of the test results.The results show that:(1)The strain rate of rape straw ash concrete specimen increased with the increase of loading pressure.The reasonable loading pressure range is 0.3-0.65 MPa.(2)The peak stress of rape straw ash concrete increases with the increase of strain rate.Under 10% straw ash content and 0.45 MPa loading pressure.The change rate of peak stress of concrete with 10% rape straw ash content at different loading pressures is the highest,up to 63.63%.Under the same loading pressure,the peak stress of rape straw ash concrete decrease with the increase of ash content of rape straw;But compare concrete with rape straw ash with control group in peak stress aspect,concrete with 10% rape straw ash is the highest,its peak stress is higher than the control,while the peak stress of other mixed rape straw ash concrete is lower than that of the control.Based on the above conclusions,the dynamic bearing capacity of concrete is the best when the ash content of rape straw is 10%.(3)As orthogonal test,the order of primary and secondary factors affecting the peak stress of ash concrete in rapeseed straw is: ash content of rapeseed straw> loading pressure> water-cement ratio,the order of influence on the peak strain is: water-cement ratio> ash content of rapestraw ash = loading pressure,the order of impact resistance is:water-cement ratio> loading pressure> rapeseed straw ash content.The optimum combination of the dynamic mechanical properties of rape straw ash concrete is A1B2C4,that is,water-cement ratio of 0.40,rapeseed straw ash content of 10%,loading pressure of0.55 MPa.(4)The results show that the ash-ratio,the ash content of rapestraw and the loading pressure had no obvious effect on the peak strain of rape straw ash concrete.The peak stress and impact resistance of concrete with 10% straw ash content are higher than that of ordinary concrete.When the ash content of rape straw is increased,the peak stress and energy absorption capacity of concrete are all showing a decreasing trend.The concrete peak stress and energy absorption capacity with the impact of increased load pressure increases while the loading pressure ranges 0.3-0.65 MPa.Therefore,for non-load-bearing structural members that are required to withstand suitable moving loads or structures,mixed with 10% rape straw ash to the concrete,can effectively improve the concrete peak stress and impact resistance. |
