Study On Size Effect Of Mechanical Properties Of Recycled Aggregate Thermal Insulation Concrete

Recycled aggregate thermal insulation concrete(RATIC)is a multi-functional green concrete.It has insulation,environmental protection,light load and other advantages because of using the construction waste-old concrete and insulation particles-glass hollow beads.The rational utilization of recycled aggregate not only alleviates the resource shortage pressure of natural gravel in China,but also relieves the environmental pressure due to the accumulation of large amount of construction waste.The addition of insulation aggregate makes the thermal conductivity of concrete lower,and realizes the concrete building insulation system and structure System with service cycle.Recycled aggregate thermal insulation concrete has a broad application prospects.The size effect is an important feature of the quasi-brittle material,and the strength decreases as the size increases.Concrete also has this feature as a brittle material.This paper studies the size effect of mechanical properties of recycled aggregate thermal insulation concrete,reveals its size effect on the mechanical properties of different recycled aggregates and different strength grades,and compared with ordinary concrete,recycled concrete and thermal insulation concrete based on the research of the research group.The research provides basic data for engineering applications.The main contents of this paper include:(1)Studies on size effect of recycled aggregate thermal insulation concrete with different recycling rate of recycled aggregate.Five recycled aggregates replacement ratios of 0%,30%,50%,70% and 100% were designed under strength grade C40 as a benchmark of RATIC with different size test block.The size effect of the mechanical properties was studied.The results show that when the size of the test piece is the same,the concrete strength is improved with the increase of the substitution rate and the elastic modulus reaches maximum at 50%.The RATIC dimensional effect parameter of the length of 200 mm is 12.4%,20.5%,20.5%,7.4% and 15.6% with the increase of the substitution rate,which is consistent with the law of concrete strength with the replacement rate of recycled aggregate.(2)Studies on the size effect of recycled aggregate thermal insulation concrete with different strength grade.The size effect of the mechanical properties was studied by using C30,C40 and C50 three strength grade of RATIC under recycled aggregates replacement ratios 50%.The results show that when the strength grade increases,the size effect is enhanced,the tension and compression ratio decreases,the brittleness of the concrete increases.Dimensional effect parameter of compressive strength of RATIC is 10.4%,20.5% and 19.8% when the strength grade is C30,C40 and C50.(3)Studies on Size Effect of Different Types of Concrete.The effects of recycled aggregate,heat-retaining aggregate and their interaction on the size effect of concrete were analyzed by designing normal concrete(NC),recycled aggregate concrete(RAC)and thermal insulation concrete(TIC)with the same strength grade.The results show that strength of four kinds of concrete decreases with the increase of the specimen size,but the obvious degree is different.Dimensional effect parameter of compressive strength of ordinary concrete,recycled concrete,thermal insulation concrete and recycled aggregate thermal insulation concrete is 6.7%、9.2%、12.4%、7.4%-11.9% when the designed strength is C40.The elastic modulus of the four kinds of concrete does not show a significant size effect,the value of the change in the range of 3%.