Effect Of Graphene Oxide/Silane On Waterproofing Performance And Chloride Resistance Of Cement-Based Materials

As the main form of marine engineering,reinforced concrete structures often fail in advance within the design service life due to the complexity of the marine environment,resulting in serious safety accidents and economic losses.The corrosion of steel bars caused by chloride ions is the primary factor causing the damage of reinforced concrete.In addition,the main factors such as chloride,freeze-thaw damage,wetting-drying cycles,etc.,which cause the deterioration of concrete durability,all involve the migration of moisture into the interior of the matrix.Therefore,hindering the transmission of external water and chloride ions to the interior of cement-based materials is of great and far-reaching significance for improving the durability of reinforced concrete structures in marine engineering and reducing corrosion losses caused by the marine environment.In this paper,graphene oxide/silane（GS）composite was used to improve the waterproofing and chloride resistance of cement-based materials.Simultaneously,considering the diversity of cement-based material mix ratios and the inevitability of bearing loads in practical projects,the influence and mechanism of factors such as water to binder ratio,fly ash,and load on the performance of cement-based materials and the protective effect of GS were explored.In addition,the feasibility of synergistically improving the properties of cement-based materials by silane,graphene oxide（GO）,and fly ash was analyzed.The main conclusions of the study are as follows:（1）GS combined with hydration products through dehydration condensation reaction to form a protective film on the surface of cement-based materials,while silane polymers can react with Ca（OH）₂ to generate additional C-S-H gels to improve the microstructure of cement-based materials.Therefore,GS can significantly improve the hydrophobicity and chloride resistance of the matrix.（2）The increase of water to binder ratio accelerated capillary water absorption and chloride transport,but it had a positive effect on chloride binding and GS protection.On the one hand,increasing the water to binder ratio promoted cement hydration and enhanced the bond between GS and hydration products.On the other hand,the high porosity caused by high water to binder ratio was also beneficial to the penetration of GS while accelerating the transport of water and chloride ions,thus facilitating the distribution and formation of GS protective film.（3）For the cement paste with standard curing of 28 d,both ordinary fly ash（OFA）and silane-modified fly ash（SFA）resulted in a decrease in compressive strength and waterproofing performance.It is worth noting that the dosage and proportion of the three have a significant influence on the performance of the sample.When doped with30%SFA,silane,GO and fly ash can synergistically form a dense gel network structure,thus improving the mechanical properties and waterproofing performance of the matrix.In addition,under the combined effects of filling,reducing hydration products,and reducing the Ca/Al ratio of fly ash,the diffusion of chloride ions decreased first and then increased,and the chloride binding increased first and then decreased.Moreover,the protective effect of GS was weakened.（4）Tensile stress led to an increase in porosity and pore size,accelerating capillary water absorption and chloride transport,and intensifing carbonation.In addition,it also resulted in the decomposition of hydration products and Friedel’s salts.Simultaneously,the increase of tensile stress was beneficial to the penetration of GS and enhanced the protective effect of GS,while the compressive stress exhibited the opposite effect.