Experimental Study On The Optimization Of Mechanical Properties Of Rubber Concrete And Its Application In Anti-collision Of Beams And Piers Member

Rubber is a material of high toughness.Adding it to concrete can not only improve the brittleness of concrete,increase its energy dissipation capacity,but also provide an environmentally friendly way for the treatment of scrapped tires.Combining with China's national conditions,the transportation network is crisscrossed and bridges often experience collision accidents.Therefore,anti-collision devices using rubber concrete can be a viable solution for reducing the risk of collision accidents and also for the recycling of scrapped tires.This paper has conducted an experimental study on the basic mechanical properties of rubber concrete,and has analyzed the compressive strength,elasticity modulus and damping ratio of rubber concrete impacted by four factors:rubber particle size,shape,pretreatment and admixture.Then,the opitimal rubber concrete was selected to make a protective coating for beam and pier members.By analyzing the dynamic response of the coating members under pendulum impact,the results indicated that the rubber concrete material had better anti-collision and vibration reduction effects.Furthermore,a detailed finite element model was established based on the experimental data.The main research conclusions are as follows:(1)The replacement of 20%fine aggregate with equal volume of rubber aggregate is a suitable method for preparing the rubber concrete.With the increase of the rubber particle size,the compressive strength of the rubber concrete first increased and then decreased.Rubber particle with too small size may adversely affect the hydration process of the cement.However,large-diameter rubber aggregates were prone to stress concentration.There may be an optimal range of rubber particle size for the static properties of rubber concrete.(2)Pretreatment of NaOH solution and incorporation of fiber-type rubber aggregates were the most effective optimization solutions for rubber concrete materials.By optimizing the properties of the rubber concrete material,the static properties such as the compressive strength and the elastic modulus were improved,while the dynamic performance such as the damping ratio still maintained its advantages over the ordinary concrete.Compared with ordinary concrete,rubber concrete had better damping ratio of more than 70%.(3)After covering a protective layer of rubber concrete to the beam or pier member,its impact stiffness was reduced,so that the peak impact force was reduced and also the displacement or the concrete strain was smaller.At the same time,due to the higher damping ratio of rubber concrete,it was observed that the impact energy was dissipated more quickly,the period of the response decay was shorter,and the damage of the component after impact was reduced,indicating that the rubber concrete coating had better anti-collision effect.(4)By comparing the dynamic response of the rubber concrete coating component made of granular or fiber rubber aggregates,it was shown that there was no significant difference in the effect of changing the rubber shape on the anti-collision propertiy of the concrete coating.Therefore,it was proved that the optimization of rubber concrete was able to improve its static performance but it had no obvious effect on the dynamic performance.Nevertheless,it still had the advantages of high damping and high energy dissipation capacity compared to ordinary concrete.(5)It was shown that the Concrete Plastic Damage model in ABAQUS was feasible for simulating rubber concrete materials and the impact test.The dynamic responses under impact load for the coating members were affected by the additional damping and additional stiffness.Moreover,the high damping and high energy dissipation property of the rubber concrete was the dominant cause of the dynamic response decrease.