Study On The Effect Of Zirconium Phosphate Composites On The Durability And Mechanical Properties Of Marine Concrete

The durability of concrete structures in the marine environment has always been a major concern for researchers.Marine concrete in service is subject to a variety of physical,chemical and biological effects,such as ionic erosion,wet and dry alternation,microbial adhesion corrosion,wave erosion and mechanical damage,etc.Their interactions aggravate the damage deterioration of marine concrete and seriously affect the service life of marine concrete structures.In this paper,we synthesizedα-zirconium phosphate（α-ZrP）as a nano-material to improve the durability of marine concrete,and prepared intercalation composites（ZrP-I.M.）and nano-zirconium phosphate-acrylamide composites（ZrP-AM）on this basis.They were used as modified materials to improve the durability and mechanical properties of marine concrete by"external coating"and"internal mixing",respectively.The following studies were conducted.（1）The intercalated composite ZrP-I.M.was prepared by a one-step in situ synthesis method,in which organic polyethyleneimine（PEI）was intercalated with silver ions（Ag⁺）with bactericidal properties between inorganicα-ZrP layers to form an organic-inorganic composite,and Ag⁺was reduced to nano-silver in situ to obtain ZrP-I.M.The influence laws of temperature and proportion on the structure and morphology of the synthesized ZrP-I.M.were investigated.The experimental characterization by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,thermogravimetric analysis（TG）,and related chemical reaction mechanisms and microscopic models were used to analyze the influencing factors of ZrP-I.M.synthesis and its morphology regulation laws,etc.In the experiment,it was found that the temperature of ZrP-I.M.synthesis needs to be≥100℃.The high temperature and high-pressure conditions are crucial for the crystallization of gel-like precursor materials to generate ZrP-I.M.In addition,the synthesis of ZrP-I.M.is influenced by the molar ratio of phosphoric acid/zirconium oxychloride under certain conditions of phosphoric acid concentration.When the molar ratio is<6:1,ZrP-I.M.is not synthesized and the microscopic morphology of the obtained material is spherical or clustered,while when the molar ratio is≥6:1,the lamellar intercalated composite ZrP-I.M.will be successfully synthesized.（2）Functional nano-modified coatings were obtained using ZrP-I.M.for the protection of marine concrete by nano-modification of silicone based and epoxy resin-based coatings,respectively.Subsequently,the modified coating specimens were tested for water resistance,chloride ion penetration resistance,bacterial inhibition and abrasion resistance,and the results showed that the above properties of the coating specimens were excellent.In the capillary water absorption test experiment,the water absorption rate of ZrP-I.M.modified silicone coated concrete was reduced by 87.98%relative to the baseline group,and the water absorption rate of modified epoxy resin coated concrete was reduced by 95.38%relative to the baseline group.In the chloride ion resistance test,the chloride ion penetration depth of the modified silicone coating was reduced from 8mm to 3mm,and the chloride ion penetration depth of the modified epoxy resin coating was reduced from 2mm to 0.5mm.In the bacterial inhibition test,the surface of the silicone coating and epoxy resin coating were modified by ZrP-I.M.,and there were almost no microorganisms attached to the coating surface and their metabolites,which indicated the anti-bacterial,anti-biological and anti-corrosion effects of the modified coating.This indicates that the modified coating has significant anti-bacterial and anti-biofouling corrosion effects.In the wear resistance test,the friction coefficient of ZrP-I.M.modified silicone coated concrete was reduced from 1.25 to 0.3 relative to the reference group,the depth of wear marks was reduced from 65μm to within 20μm,and the wear rate was reduced from 13.7583×10^-3mm³/Nm to 0.5833×10^-3mm³/The excellent wear resistance is attributed to the good mechanical properties of ZrP-I.M.nanomaterials,which improve the wear resistance of the coating,and the two-dimensional lamellar structure also acts as a solid lubricant,with significant lubrication and friction reduction effects.In addition,the slip sheet structure composed of ZrP-I.M.interlayer nano-silver and ZrP sheet layer also enhances the lubricity of the coating surface.（3）Taking polymer modified cementitious materials as a starting point,acrylamide（AM）monomer was inserted betweenα-ZrP layers to obtain ZrP-AM,a nano zirconium phosphate-acrylamide composite,which was blended into concrete to prepare ZrP-polymer composite modified concrete.The organic-inorganic composite structure was established by using the in-situ polymerization of ZrP interlayer and external AM,while forming a star-like network structure together with the ZrP of the lamellae,and then forming a bond with the cement hydration products.The ZrP-polymer composite modified concrete was co-modified by in situ polymerization of ZrP and AM in the lamellae,so that ZrP and AM can play a synergistic role.ZrP-AM can play the advantage of nano-materials to promote the hydration reaction of cement and enhance the mechanical properties of concrete by improving the density of concrete,and it can also obtain the polymer network formed by in situ polymerization of AM to enhance the flexural strength of concrete.The experimental results showed that the flexural strength of concrete modified by ZrP-AM（1%admixture）was improved by about 120%relative to the reference group and about 55%relative to the polymer modified group.