Experimental Study On Concrete Recycled Aggregate Mixed With Water Stabilized Crushed Stone Base In Cold Area

With the rapid development of China’s economy and urbanization,a large amount of construction waste has been produced in cities.These wastes are disposed by randomly stacking or buried in digging pits,which not only occupies land resources,pollutes water resources,but also causes inconvenience to surrounding residents.In order to solve the problem that how to deal with the construction waste,the recycled aggregate comes,which is produced with crushed construction waste.Natural aggregate is replaced with the recycled aggregate in road base.This consumes construction waste and protects the ecological environment.This paper mainly studies the experimental research of mixing recycled coarse aggregate into cement stabilized crushed stone base in cold areas.The main contents and achievements of this paper are as follows:(1)Comparison of basic characteristics between recycled aggregate and natural aggregate.The density of recycled aggregate is lower than that of natural aggregate,and the water absorption rate is on the contrary.The crush value,needle-like particle content,and abrasion value of both meet the specification requirements.(2)the material mix ratio is determined by compaction test and 7d unconfined compressive strength test.The four groups of replacement ratios with a representative value of compressive strength greater than 5MPa have a cement content of 4.5%.At the same time,the strength of a mixture with a cement content of 5% is comparatively studied,so the cement content is determined to be 4.5% and 5%.(3)Through unconfined compressive strength test,indirect tensile strength test,compressive rebound modulus test,the influence of 7d,28 d,90d age,cement content,and replacement rate on strength is analyzed.With a certain age and cement content,as the replacement rate increases,the compressive strength,indirect tensile strength,and compressive resilience modulus all show a downward trend;the replacement rate and cement content are constant,and the longer the curing age,the greater the strength and the compression resistance.The greater the modulus of resilience;the tensile-compression ratio of 4.5% is greater than that of the cement content of 5.0%,so the toughness of 4.5% cement is better than that of 5.0% cement;the linear relationship between the representative strength value and the replacement rate is fitted by Origin software,It is predictable that the replacement rate will decrease with every 10% increase in strength.(4)With the same mixture ratio,curing for 28 days,5 freeze-thaw cycles,analysis of the effect of freeze-thaw on the compressive strength of the specimens,it is concluded that the 5.0% cement content is higher than the 4.5% cement content of the specimens.Frost resistance is good;the cement content is constant,as the replacement rate increases,the representative value of compressive strength decreases after freezing and thawing,and the relative loss rate of compressive strength before and after freezing and thawing also decreases.The performance of recycled coarse aggregate is not as good as that of natural aggregate,but it meets the requirements of road base aggregate specifications.The increase in replacement rate and the decrease in strength of specimens are in line with the general law.The increase in recycled coarse aggregates in the freeze-thaw environment inhibits the decrease in strength of specimens.The research in this paper provides reference value for the application of recycled aggregates in road bases in cold regions.