Experimental Study On The Effect Of Rubber Particle Size On The Durability Of Concrete Under Freeze-thaw Cycles

There is a large temperature difference between day and night(freeze-thaw cycle)in Northwest my country,which is easy to adversely affect the performance of concrete materials.The composition of waste tires is extremely complex,and the decomposition time under natural conditions is extremely long.pollution,resulting in "black pollution".In this paper,waste tires are designed to be processed into rubber particles(10 mesh,20 mesh,30mesh),and added to concrete(with a dosage of 20%)to prepare rubber concrete.The freeze-thaw cycles are 0,25,50,75,The compressive strength,splitting tensile strength and dynamic compressive properties of rubberized concrete were tested at 100 and 125 times,and the changes in performance parameters of mass loss rate and relative dynamic elastic modulus were observed and compared with ordinary concrete.Finally,based on SEM scanning technology,the mechanism of rubber improving concrete performance under freeze-thaw cycle environment is revealed from a microscopic point of view.The research results include the following aspects:(1)The addition of rubber slowed down the reduction of mass loss rate and dynamic elastic modulus of concrete after freeze-thaw cycles,and improved the frost resistance of concrete.Among them,the addition of 30-mesh rubber improves the frost resistance of concrete the best.(2)The incorporation of rubber into concrete reduces its compressive and splitting tensile strength.In the process of freeze-thaw cycles,with the increase of the number of cycles,the strength of concrete decreases significantly,but the addition of rubber effectively slows down the reduction rate of concrete strength.When 20% 30-mesh rubber was added,the effect on concrete strength was minimal,and it was most effective in slowing down the strength reduction after freeze-thaw cycles.(3)The SHPB test device was used to impact the rubber concrete after different cycles at 0.3,0.45,and 0.6MPa air pressure.The results show that the dynamic compressive strength of the same rubber concrete decreases with the increase of the number of freeze-thaw cycles.With the increase of the impact air pressure,the strain rate increases,and the dynamic compressive strength of the specimen increases.Different particle sizes of rubber have different effects,among which 30-mesh rubber is the best.(4)It can be seen from the comprehensive analysis of the specimen’s force failure morphology and SEM microscopic test that the addition of rubber reduces the freeze-thaw damage inside the concrete specimen,increases the toughness of the concrete,and makes the integrity of the specimen better than that of ordinary concrete.To sum up,the addition of rubber effectively improves the performance of concrete,and provides more opportunities for the reuse of waste rubber tires and the practical engineering application of rubber concrete.