Experimental Study On Mechanical Properties Of Desert Sand Concrete Beams

The number of rivers in northwestern China is small and unevenly distributed,which makes the contradiction between supply and demand of coarse and medium sand resources needed in engineering construction increasingly conspicuous,and restricts the development of construction industry.In this situation,using the Xinjiang's desert sand resources to replace some coarse and medium sand in concrete was proposed,which not only make full use of desert sand resources,but also reduced transportation costs,thereby reduced engineering costs and improving the local environment.In this paper,the desert sand concrete beam in Xinjiang was taken as the research object.According to the orthogonal test and the single factor test,the optimal mix ratio of desert sand concrete was obtained.Based on the experimental study of 15 desert sand concrete beams and 3 plain concrete beams with concrete strength grade C40,the influence laws of shear to span ratio,reinforcement ratio,stirrup ratio,loading mode,desert sand content and other factors on the flexural and shear properties of the beams were obtained.(1)According to the comprehensive analysis,the optimal mix ratio of desert sand concrete was that the water-to-binder ratio was 0.4,the sand ratio was 0.3,the desert sand replacement rate was 80%,the fly ash content was 7.5%,and the water reducing agent dosage was 0.4%.(2)Based on the desert sand replacement rate and the reinforcement ratio,the experimental data of 8 beams were analyzed.The results showed that during the stress process of desert sand concrete beam,the strain variation of the normal section concrete was basically consistent with the flat section assumption,and its failure mode and the failure mechanism were basically the same as that of ordinary concrete beams;the ultimate bending moment bearing capacity of desert sand concrete beams decreased first and then increased with the increase of desert sand replacement rate.(3)Through the study of 18 beams,the shear capacity of desert sand concrete beams was obtained.Test results showed that the damage process of desert sand concrete beams were similar to that of ordinary concrete beams and had almost the same initial stiffness.The destruction process was divided into three stages: initial cracking,crack initiation and destruction.When ??1.0,the beam often was baroclinic failure;when 1.0<??2.5,the beam often was shear bending failure;when 2.5<??3.0,the beam was bending failure;the shear capacity of desert sand concrete beam increased with the increase of reinforcement ratio and stirrup ratio;the shear span ratio decreased as the shear span ratio increased;the desert sand replacement rate increased as the shear capacity gradually decreased.Under the L1 and L2 loading modes,the shear capacity of desert sand concrete beams was relatively close,but they were significantly lower than the shear capacity under L3.