Preparation Of Graphene Oxide/Silane Composite Emulsion And Its Effect On Durability Of Concrete

Concrete is the most widely used and largest building material in modern civil engineering and the most important structural material.Research on the durability of concrete concern,the American scholar Sitter has vividly described the economic loss due to improper or ill-considered measures resulting from insufficient durability of concrete caused by"five times the law."Research on the durability of concrete has always shown that the existence of water is the main cause of concrete damage.The harmful ions usually rely on water to enter the interior of the concrete,causing damage to the structure,resulting in reduced durability.Therefore,controlling the entry of moisture is One of the main measures to improve the durability of concrete.Silane-permeable waterproof material has become a commonly used concrete waterproof material on the market due to its good permeability and excellent waterproof effect.However,silane waterproof materials also have disadvantages such as volatilization and uneven penetration,so they need to be optimized and improved.In this paper,isobutyl triethoxysilane monomer is used as the main raw material.In the process of preparing silane emulsion,graphene oxide suspension is added,and graphene oxide/silane composite emulsion is prepared by controlling temperature and stirring speed.The suitable range of graphene oxide was determined by stability test,and the optimal blending amount of graphene oxide was determined by the water absorption test of cement mortar block.The effects of graphene oxide,silane emulsion and graphene oxide/silane composite emulsion on the durability of concrete were studied by means of water absorption,salt absorption,RCM,gas passage and carbonization.The microscopic test method（SEM,XPS,FTIR and TGA）was used to study the composite mechanism between graphene oxide and silane and study the protective mechanism of composite emulsion on concrete.The results of the capillary water absorption test showed that the water absorption of the concrete coated with the composite emulsion was more than 89%lower than the blank group.Even after the concrete surface was worn by 6 mm,the water absorption of the concrete coated with the composite emulsion was still more than 80%lower than the blank group.The composite emulsion also has a good waterproof effect on the cracked cement-based material.When the mortar test block is prefabricated with a 0.5 mm crack,the water absorption at the crack is reduced by more than 90%compared with the uncoated.The capillary salt test results show that the chloride ion content of the concrete coated with the composite emulsion reaches a stable state at a depth of 10 mm,and the content is only 0.06%.It does not cause damage to the concrete inside the concrete,and compared with the chlorine ion content at a depth of 10 mm with the blank group,the chloride ion content was reduced by 76%.In the fast chloride ion migration test,the migration speed of chloride ions was accelerated by electric acceleration.At the end of the test,the depth of the cement-based material coated with the composite emulsion was9.18 mm,which was 81.2%lower than the blank group,and the composite emulsion was coated.The chloride-based mobility coefficient of cement-based materials was0.77×10^-12 m²·s^-1,which was 78.6%lower than the blank group.The Auto-Clam test results show that although the composite emulsion has a certain influence on the permeability of concrete,it does not hinder the"breathing"of concrete.In the rapid carbonization test,the carbonized depth of the concrete coated with the composite emulsion was 2.59 mm（W/C=0.4）and 3.67 mm（W/C=0.6）,and the carbonization depth was reduced by 54.8%（W/C=0.4）and 59.4%（W/C=0.6）compared with the blank group.In the microscopic test,the internal chemical bond of the composite emulsion was detected by FT-IR,and the characteristic peak appearing near 1083.3 cm-1 was generated by the vibration of Si-O-C covalent bond,indicating that the graphene oxide and the silane were successfully connected.XPS test results show that the amount of C-OH in the composite emulsion is lower than the amount of C-OH in the silane emulsion,indicating that C-OH in the composite emulsion participates in the formation of Si-O-C covalent bond,so that the number of C-OH in the composite emulsion is reduced.The results of SEM and EDS show that the composite emulsion forms a hydrophobic layer combined with flocculent and cluster structure in the cement-based material,thereby improving the waterproof effect of the composite emulsion.The TGA results show that the hydrophobic layer formed by the composite emulsion decomposes between 300-500°C,which proves that the composite emulsion can be well connected with the cement-based material.