Study On Loading Behavior Of R.C.Columns With Recycled Aggregates

In recent years,with the constant development of urbanization,construction industry is growing rapidly,which gradually increases the demand for sand and gravel.As a consequence,while the uncontrolled exploitation of natural sand and gravel aggregate seriously affects the ecological environment,a lot of construction waste which can not be effectively used caused serious secondary damage.Recycled concrete technology allows the recycle of waste concrete and thus reduces the demand for natural aggregate resource.It not only protects the natural ecological environment,but also solves the problem of waste treatment in city construction.By adoption this technology,the coordination of resource and environment will be realized and the sustainable development in the construction industry can also be promoted.In order to offer more reference to the application of recycled concrete in practical engineering,twelve R.C.columns with recycled aggregates(replacement rates are 0%,50%and 70%respectively)are designed and made in this research.In addition,the axial compression test and eccentric loading test(eccentricities are 60mm,94mm and 140mm)are carried out.(1)Through the comparative analysis of test phenomena and destruction mode,the results show that the test phenomena and destruction mode of the R.C.columns with recycled aggregates and the R.C.columns with natural aggregates are similar.(2)Through the comparative analysis of the load-strain curve of reinforcing steel bar and concrete,the results show that the load-strain curve of the R.C.columns with recycled aggregates and the R.C.columns with natural aggregates are similar.And the beams' cross section strain at midspan of concrete conforms to the plane section assumption.(3)Through analysis of the lateral deflection,the result shows that the deformability of members does not have significant changes with the recycled aggregates addition.(4)The bearing capacity of the columns is calculated,and the calculated value and measured value are compared and analyzed.The results show that the calculation formula of bearing capacity for ordinary concrete columns in Code for Design on Concrete Structures(GB50010-2010)is applicable for R.C.columns with recycled aggregate,but for the eccentrically loaded members with tension failure,the calculated value should be adjusted through multiplying by coefficient of 0.9.(5)The cracks of the columns are compared and analyzed,the results show that the development features of the cracks between the eccentric compression members with different eccentricity and those with different replacement rates are similar.When the eccentricity is big,the crack resistance is same between the recycled concrete columns and ordinary concrete columns;when eccentricity is small,recycled concrete columns have better crack resistance than ordinary concrete columns.