Study On The Modification Of Reclaimed Aggregate Of Concrete And Its Application In Cement Stabilized Macadam Base

With the acceleration of China's urbanization construction,more and more buildings need to be demolished and rebuilt.In this process,a lot of waste concrete will be generated,and it will require a lot of manpower and material resources to deal with it.The burden.Crushing waste concrete into aggregates for recycling and reuse,on the one hand,can save a lot of high-quality natural reduce the development of mountainous areas,and protect the environment;on the other hand,it can reduce the amount of waste concrete and turn waste into treasure.Sustainable development is of great significance.The waste concrete recycled aggregate has defects such as low apparent density and high water absorption rate.If it is directly applied to the base,it will cause a series of problems such as cracks in the base.In view of this,this article strengthens the recycled aggregates,and then researches its application in the base.This paper first tested the three physical properties of the apparent density,water absorption and crushing value of the recycled aggregate,observed its microstructure with the help of SEM,and compared and analyzed it with natural aggregate.The results show that there are a large number of voids,microcracks and interface transition regions in the recycled aggregate,which makes its apparent density low,and its water absorption and crushing values high,so it cannot be applied directly,and it needs to be modified.To improve various performance indicators.Secondly,the abrasion tester and water glass,nano-SiO₂ and osmotic crystalline materials were used to physically and chemically strengthen the recycled aggregates,and the strengthening effect was evaluated through performance testing.It is concluded that the physical strengthening effect is average;Chemical strengthening has a better effect on the performance of recycled aggregates.In contrast,4%water glass and 6%nano-SiO₂ have a more significant effect on the water absorption of recycled aggregates.This paper also analyzes the chemical strengthening effect from the microstructure of the recycled aggregate through scanning electron microscopy,energy spectrum analysis and pore size analysis.The results show that the microcracks and interface transition regions of the recycled aggregate after chemical strengthening are repaired.Both the total pore size and the maximum pore size are reduced.Thirdly,four kinds of cement stabilized recycled aggregates with different amounts of recycled aggregate were configured,and various test pieces were formed according to the cement dosage of 4%and 5%to test the strength characteristics,rebound modulus,freeze resistance and Shrink characteristics and analyze their influencing factors.The results show that properly increasing the amount of recycled aggregate within a certain range can increase the split strength and split spring modulus of cement stabilized recycled aggregates,but the unconfined compressive strength and compressive rebound modulus As it decreases,the anti-freezing characteristics show a downward trend;The amount of recycled aggregate has a greater impact on the shrinkage characteristics of the aggregate.With the increase of the amount of recycled aggregate,both the dry shrinkage coefficient and the temperature shrinkage coefficient increase.The road performance of the cement stabilized recycled aggregate with the appropriate amount can meet Construction requirements.Finally,a random-feed model of aggregate was used to generate a meso-finite finite element model of cement stabilized recycled aggregate,and the cracking of the semi-rigid base was studied.Research shows that the cumulative fracture length of the recycled aggregate after the strengthening is shorter;There is a peak in the stress distribution along the cracking path of the recycled aggregate.The stress peak and stress zero point of the aggregate before the strengthening are closer to the top surface loading point,and the degree of cracking is larger and the crack is longer.At the same time,the length of failure of the recycled aggregate after strengthening is longer than that before strengthening,the initial damage to the bonding interface is delayed,and the rate of bonding failure is slower.