Experimental Study On Mechanical And Fatigue Properties Of Rice Husk Ash Concrete

Rice husk ash has good pozzolanic action and microaggregate filling effect.The ground rice husk ash can not only reduce the air pollution caused by rice husk ash,but also improve the bending strength,impact life and bending fatigue life of cement concrete by adding it into cement concrete surface layer of low grade highway.It also reduces the cost of road construction.The paper tested the mechanical properties,physical properties,impact resistance and bending fatigue properties of rice husk ash concrete with different grain sizes(120μm,44μm,17μm,10μm,8μm)and mixing amount(0%,5%,10%,20%,30%).The specific research contents and conclusions are as follows:(1)Through orthogonal test and matrix analysis,the optimal level of coarse aggregate gradation,sand ratio and water-cement ratio have been determined as 4.75mm-19.5mm coarse aggregate ratio of 35%,sand ratio of 34%,water-cement ratio of 0.43.Under the mixture ratio,the flexural strength,compressive strength and slump of rice husk ash concrete all meet the standard of low grade highway surface concrete.(2)The flexural and tensile strength,compressive strength,dynamic modulus,dry density,water absorption and impact resistance of rice husk ash concrete with different grain size and dosage of rice husk ash have been tested.The test results show that when the average grain size of rice husk ash is 17μm and the content of rice husk ash is 5%,the compressive strength and dynamic modulus of rice husk ash concrete decrease slightly,the dry density and water absorption decrease more,and the impact resistance and impact toughness improve to a certain extent.(3)The flexural fatigue tests of rice husk ash concrete with different grain size and dosage of rice husk ash have been carried out to analyze the influence of grain size and dosage of rice husk ash on the fatigue life of rice husk ash concrete,and the S-N curve and P-S-N curve set of rice husk ash concrete have been established.The experimental results show that the fatigue life of rice husk ash concrete follows the two-parameter Weibull distribution.When the average grain size of rice husk ash is in the range of 17μm ～ 8μm and the dosage is in the range of 0% ～ 10%,the fatigue life of rice husk ash concrete is improved compared with that of reference concrete,but the advantage decreases gradually with the increase of stress level.(4)By Weibull distribution theory,the paper has calculated the equivalent fatigue life of the specimens under different failure probability,and obtained the fatigue life equation of rice husk ash concrete under different rice husk ash particle size and dosage.When the bending fatigue life of 2 million times,the fatigue strength reduction factor of rice husk ash concrete is in the range of 0.2267 ～ 0.4896 by fatigue equation.When the content of rice husk ash is 10% and the average particle size is between 10μm and 8μm,the reduction coefficient of fatigue strength of rice husk ash concrete is lower than that of reference concrete.(5)The paper has analyzed theoretically the bending fatigue damage process of rice husk ash concrete,and discussed the actual stress ratio of rice husk ash concrete in bending fatigue process by using the basic concept of damage mechanics and the fatigue damage equation of rice husk ash concrete.