Design And Fatigue Properties Of Waste Rubber Powder Foam Concrete

The southeast region of China has a well-developed water system,extensive river networks,and a large number of soft soil foundations,which are prone to road instability such as uneven settlement,leading to problems such as road surface water,road collapse,and "vehicle jumping at the bridge head.".Foam concrete has the characteristics of light weight and high fluidity,which can effectively reduce the self weight of the subgrade and restrain the settlement of the subgrade when it is applied to the replacement of soft soil subgrade.However,the fatigue resistance of foam concrete is not outstanding,which becomes the bottleneck problem that restricts the long-term use of foam concrete subgrade.By mixing waste rubber powder into foam concrete,on the one hand,it can alleviate the burden on the environment caused by the difficulty in recycling waste rubber,on the other hand,it can ensure light weight,convenient construction and have certain fatigue resistance.In this paper,waste rubber powder foam concrete was prepared and fatigue performance was studied.The research contents and results are as follows:(1)Select the components of waste rubber powder foam concrete and determine its index requirements,formulate the preparation process according to the specifications,and clarify the precautions for the test.Using this preparation method,waste rubber powder foam concrete that can meet the specification requirements was prepared in the laboratory.(2)Through theoretical calculation,single and multi factor mix design is adopted to analyze the influence of rubber powder,foaming agent and fly ash on the physical and mechanical properties of waste rubber powder foam concrete,and determine the optimal mix proportion and the primary and secondary order of the influencing factors.The results show that the dry density and compressive strength of waste rubber powder foam concrete decrease with the increase of rubber powder and foaming agent content,and decrease with the increase of fly ash content;The water absorption decreases with the increase of rubber powder content,and increases with the increase of foaming agent and fly ash.The optimal mix ratio was determined to meet the specification requirements.The order of influence on dry density and compressive strength is: foaming agent>rubber powder>fly ash;The primary and secondary order of influence on water absorption: fly ash>foaming agent>rubber powder.(3)The static bending test and fatigue load test of waste rubber powder foam concrete were carried out.The effect of rubber powder content on flexural strength and deflection was tested by electro-hydraulic servo fatigue testing machine and strain gauge,and the change rule of rubber powder content and stress level on fatigue life was also tested.The toughness and fatigue resistance of waste rubber powder foam concrete were analyzed;Draw a fatigue strain curve and analyze the relationship between the number of cycles and strain.The results show that rubber powder can reduce the flexural strength of foam concrete,but increase the peak deflection of foam concrete and enhance the toughness of foam concrete;The fatigue life of waste rubber powder foam concrete decreases with the increase of stress level,and increases with the increase of rubber powder content.Under cyclic loading,the strain of waste rubber powder foam concrete experienced three stages: strain initiation,strain stable development,and strain rapid growth.(4)The fatigue life is analyzed using the Weibull distribution theory.Through linear regression analysis,a good linear relationship is presented,which conforms to the Weibull distribution rule.Using Weibull distribution probability model,the fatigue test results of waste rubber powder foam concrete are analyzed.The fatigue life of waste rubber powder foam concrete under different assurance rates is calculated,and the double logarithmic fatigue equation under different assurance rates is established.Combined with the actual traffic volume of the supporting project,relevant data are substituted into the double logarithmic fatigue life equation,and the fatigue life of waste rubber powder foam concrete subgrade under different assurance rates is predicted.The calculated results are greater than the cumulative equivalent standard axle load times within the design life of the actual project,which meets the requirements of the design service life of the highway.