Experimental Study On The Influence Of Sessile Organisms On The Main Parameters Of Marine Concrete Durability

Corrosion of steel bars in marine concrete has caused seriously economic losses,and more and more attention has been paid to effective methods of anti-corrosion.It is found that marine sessile organisms,especially oysters settled on concrete structures in tidal zone can improve the chloride resistance of concrete,and then protect the steel bars from corrosion.Simultaneously,carbonization depth and water absorption are also the main parameters which affect the durability of concrete.However,there are limited studies about the effect of oysters settled on concrete surfaces,especially those settled oysters through artificial control,on the main parameters of concrete durability.Therefore,this paper studies the effect of oysters on the main durability parameters of marine concrete in the terms of Electric flux,water absorption and carbonization,discusses and explains the mechanism of anti-corrosion of reinforced concrete by oyster from the micro-perspective,providing a reference for the durability design and life prediction of marine concrete structures.In this paper,the effects of T and M inducer on the settlement of oysters on concrete surface were studied.The real sea exposure test shows that the addition of inducer T or M can significantly improve the rate of settled oysters on concrete surface,especially when the inducer T and M are compound added,the improving effect is pretty favorable.After the oysters attached on concrete,the electric flux test,water absorption test and carbonization test were carried out.The results show that dense attachment of oysters can effectively improve the chloride resistance of concrete and reduce the water absorption of concrete.The surface water absorption of the concrete with attached oysters decreases by up to70% in comparison to that without attached oysters.The attachment of oysters reduces the external CO2 entering into the concrete and reacts with Ca(OH)2,thus reducing the carbonization depth of concrete and improving the carbonization resistance of concrete.The results of Scan electron microscope(SEM)and mercury intrusion porosimetry(MIP)explain the result of macro-properties,there is a layer of oyster glue about 20 m thick in the transition zone between oyster shell and concrete.The colloidal layer is composed of rodshaped fibre structure and densely arranged.The attachment of oysters reduces the total pore volume and porosity of surface concrete,reduces the average pore size of concrete,improves the pore size distribution and the pore structure of concrete.After oyster's attachment,the number of harmful pores in concrete above 200 nm are significantly decreased and the number of harmless pores under 20 nm are significantly increased,while the change of pores within 20-200 nm is random.Finally,the bonding strength of oyster glue was analyzed.It is found that the bonding strength of oyster glue varies within the range of 0.91-1.45 MPa,and is much higher.The bonding strength of oyster glue is positively correlated with the compressive strength of concrete,the bonding strength increases with increasing compressive strength of concrete.In addition,the bonding strength of oyster is also predicted to be related to the porosity of the settlement substrate.