Experimental Research On Fracture Properties Of Doped Lithium Slag Recycled Concrete

Because of the different physical properties of the internal components of the concrete,the joints between the various parts are not the same.It is a complex composite material,and due to the effects of loads and the environment,the failure mechanism is extremely complex.The study of fracture properties of concrete is difficult and necessary.As a kind of mineral admixture,lithium slag,although it is not widely used at present,has a certain amount of lithium slag to improve the mechanical properties of concrete.Although the recycled aggregate has its own insufficiency,it also has its advantages.With the idea of sustainable development deeply rooted in people's minds,the research on recycled concrete has attracted more and more attention.Therefore,in this paper,for the lithium-doped slag-recycled concrete materials,the cubic compressive strength,splitting tensile strength,and fracture properties(mainly including fracture energy and double K fracture toughness)are studied in the following three aspects:(1)The cubic compressive strength and splitting tensile strength of recycled concrete mixed with lithium slag have been experimentally studied.The test results show that the cubic compressive strength and splitting tensile strength are mixed with lithium slag.The increase of the amount increases,with the increase of the replacement rate of the recycled coarse aggregate,showing the trend of increasing first and then decreasing.(2)Three-point bending beam method was used to test the fracture performance of recycled concrete with lithium-doped slag.The load-cross-middle deflection curve(P-? curve)was obtained through the test,and the fracture energy under various working conditions with different initial crack height ratios,lithium slag content,and recycled coarse aggregate replacement rate was calculated according to the calculation formula of fracture energy.The test results show that the fracture energy of the lithium-doped slag-recycled concrete gradually decreases with the increase of the initial joint height ratio.When the lithium slag content increases,the fracture energy of the lithium-doped slag concrete gradually decreases.With the increase of the replacement rate of recycled coarse aggregates,the fracture energy of recycled concrete with lithium residue increases first and then decreases.(3)The crack initiation load of the test piece was measured by a resistance strain gauge method,and the load-strain curve(P-? curve)and the load-crack opening migration curve(CMODP-curve)were obtained through the test.The double K fracture toughness of recycled concrete mixed with lithium slag was calculated.The test results show that the starting fracture toughness of recycled concrete with lithium-doped slag gradually decreases with the increase of the initial joint height ratio,and the instability fracture toughness is hardly affected by the initial joint height ratio.The double K fracture toughness of recycled concrete with lithium doped slag increases with the increase of lithium slag content,and the increase in the instability fracture toughness is greater.With the increase of the replacement ratio of recycled aggregates,the fracture fracture toughness and the instability fracture toughness both showed an increase and then decrease.