Study On Mechanical Properties And Durability Of Fiber Rubber Concrete

With the concept of green building gaining popularity,how to save resources,protect the environment and reduce pollution has become a new task in the new era.As a typical representative of solid waste building materials utilization,it is important to realize the wide application of rubber concrete in practical engineering has very important significance.In this thesis,the mechanical properties,frost resistance,micro-morphology,pore structure and pore size distribution of fiber rubber concrete were studied by experiments.The main results are:(1)The influence of fiber type and fiber content on mechanical properties of rubber concrete was studied through the mechanical properties test,such as compressive test and flexural test.The results showed that:①The single doped steel fiber can improve the compressive strength and flexural strength of rubber concrete.Single polypropylene fiber can also improve the flexure strength of rubber concrete to a certain extent,but the improvement effect of compressive strength is not obvious.②The improvement effect of mixed fiber on the compressive strength of rubber concrete is better than that of polypropylene fiber.When the total amount of mixed fiber is small,the compressive strength of mixed fiber rubber concrete is better than that of steel fiber rubber.However,when the total amount of mixed fiber is large,the addition of mixed fiber will hinder the development of compressive performance,and the improvement effect is not as good as that of single fiber.③The improvement effect of mixed fiber on the flexural strength of rubber concrete is not as good as that of single doped steel fiber or single doped polypropylene fiber.When steel fiber and polypropylene fiber are mixed into rubber concrete,if S=0.5%or P=0.05%,the flexure strength will increase with the increase of another fiber content;If the content of steel fiber is too much(1%≤S≤1.5%)or polypropylene fiber is too much(0.1%≤P≤0.15%),the bending strength will decrease with the increase of the content of another fiber.(2)Through freeze-thaw cycle test,the influences of fiber content and fiber type on mass loss rate,residual compressive strength and strength loss rate of rubber concrete were studied.The results showed that:①With the increase of the number of freeze-thaw cycles,the mass loss rate of mixed fiber reinforced rubber concrete and steel fiber reinforced rubber concrete increases gradually,while the polypropylene fiber reinforced rubber concrete will have a short quality rebound phenomenon in the early freeze-thaw period,and then with the increase of polypropylene fiber content,the mass loss rate changes from negative to positive and gradually increases.②The addition of steel fiber or polypropylene fiber can improve the residual compressive strength,and the improvement effect of mixed fiber on the residual compressive strength depends on the fiber content.When the content of steel fiber is small(S=0.5%～1%)or polypropylene fiber is small(P=0.05%～0.1%),the residual compressive strength of mixed fiber rubber concrete is better than that of single fiber rubber concrete.When the content of steel fiber is too large or polypropylene fiber is too large,the improvement effect is not as good as single fiber.(3)The effects of different fiber types and different content on the microstructure and pore structure of rubber concrete were studied by scanning electron microscopy and mercury injection test.The results showed that:①The compactness of rubber concrete structure is poor,and there are larger cracks and more holes inside.The addition of fiber can effectively reduce the number of internal defects,cracks and holes,but when the amount of mixed fiber is high,the internal holes and cracks will increase,and the structural compactness will decrease.②With the addition of fiber,the median pore diameter,average pore diameter and specific pore volume will decrease obviously,but the change range of the most holes is small.③When steel fiber or polypropylene fiber is added separately,the total porosity will decrease,and the pore size distribution will be improved,and the number of harmless and less harmful pores will increase.④When steel fiber and polypropylene fiber are mixed into rubber concrete,if the amount of steel fiber or polypropylene fiber is less,the total porosity will decrease with the increase of the content of another fiber,and the internal harmless porosity or the proportion of the total porosity will increase.If the content of steel fiber or polypropylene fiber is too much,the addition of another fiber will deteriorate the internal pore structure,resulting in the increase of the total porosity and the increase of harmful pores and multiple harmful pores.This thesis has 78 pictures,9 tables,and 100 references.