Experimental Study On The Mechanical Properties Of Sea Water Sea Sand Coral Concrete

Concrete mixed with seawater,sea sand and coral coarse aggregate not only has good mechanical properties,but also is conducive to saving land building materials and making full use of marine resources.As a new material system,seawater sand coral concrete has received little research at present.Based on the existing results,the compressive deformation and failure characteristics of marine sand coral concrete are studied in this paper.The following work is mainly carried out.The research status of seawater concrete,seawater sand concrete and coral concrete is summarized.On this basis,the experimental study on the compressive properties of seawater sand coral concrete is completed,and the influences of various parameters on the mechanical properties of ordinary seawater sand coral concrete and modified seawater sand coral concrete are analyzed.Taking the types of mixed water,fine aggregate and admixture as research parameters,the axial compressive performance test of seawater sand coral concrete was completed.The cube compressive strength and Prism(geometry)compressive strength of concrete at various ages are measured,and the stress-strain curve and Poisson’s ratio curve are obtained.The influence of various factors on the failure characteristics and mechanical deformation performance of concrete is analyzed.The results show that the whole process of mechanical deformation is significantly different from that of ordinary concrete.Affected by coral aggregate,the material failure mode is brittle failure.Shell in sea sand affects the compactness of concrete and reduces its strength.The strength of seawater concrete is higher than that of fresh water concrete,but its ductility is worse.Fly ash and granulated blast furnace slag as additives improve the strength and peak strain of seawater sand coral concrete.Taking cement varieties,types of admixtures and amount of admixtures as research parameters,the axial compressive performance test of modified seawater sea sand coral concrete was completed.The results show that the strength of concrete specimens using low basicity sulphoaluminate cement is slightly lower and the ductility is increased than that of Portland cement.The strength and ductility of the specimens are improved best by adding stainless steel fiber.The failure mode of the specimens is also changed from brittle failure to ductile destruction,and the strength is improved.However,the performance improvement of single-doped polypropylene fiber or double-doped fiber is slightly lower than that of single-doped steel fiber under the same conditions.Based on digital image processing technology and digital speckle correlation method,the deformation and crack damage evolution process of marine sand coral concrete under compression are studied from microscopic and macroscopic perspectives,and the material deformation of each phase in concrete and the occurrence and development of cracks are analyzed.The results show that the strength of coarse aggregate has great influence on concrete,and cracks appear in cement mortar,coral coarse aggregate and interface transition zone at the initial loading stage.The crack is smaller before peak stress,and it grows to failure after peak stress.The failure main crack crosses coral coarse aggregate,cement mortar and interface transition zone.Seawater and sea sand will enhance the influence on the vertical strain field of concrete,while fly ash admixture will weaken the influence of chloride ion and shell in seawater and sea sand on the vertical strain field of material.Finally,the research and analysis in this paper are summarized and concluded,and relevant suggestions are put forward for the research on the axial compressive properties of marine sand coral concrete.