Effect Of Graphene Oxide Modified In（OH）₃ On Properties Of Cement-based Composites

As a typical load-bearing material,cement concrete has the advantages of high compressive strength,high hardness and low cost,which is irreplaceable in the field of infrastructure construction.The main problem of cement concrete is the low flexural strength and brittleness,which leads to the sudden brittleness damage of many important cement concrete projects and frequent engineering accidents.Cement concrete is an uneven porous brittle material with micro-nano size defects.When subjected to external loads,serious stress concentration occurs at the micro-nano defects,leading to micro-nano cracks in the body of hydration products.Under the action of continuous load,micro and nano cracks continue to expand and merge,forming macro cracks,and eventually lead to brittle fracture of concrete.Therefore,the key to improve the toughness,strength and cracking resistance of high-performance concrete is to strengthen the structural strength of concrete from micro and nano scale and prevent the formation and expansion of micro and nano cracks.As a two-dimensional nanomaterial,graphene oxide（GO）can control crack generation and propagation at the nanoscale,which is an ideal material for improving the toughness of cement-based composites.However,the GO surface roughness is low,and its binding force with the cement concrete matrix is weak,which is easy to disstick in the process of concrete fracture and failure,and can not give full play to the strengthening and toughening effect.In this paper,In Cl₃ was used as a precursor,urea and sodium citrate were used as precipitators and reducing agents,and nano In（OH）3 particles with uniform dispersion on GO surface and good crystallinity were prepared by hydrothermal method,which effectively solved the problem of smooth GO surface.The effects of precursor concentration,precipitator,hydrothermal time and hydrothermal temperature on the properties of In（OH）₃@GO were investigated.The surface roughness,specific surface area and microscopic morphology of In（OH）₃@GO were characterized by AFM,BET and SEM.At the same time,the effects of In（OH）₃@GO on the heat of hydration,water absorption,porosity,mechanical properties and micro-morphology of cement-based materials and the mechanism of action were explored.The main conclusions reached are as follows:（1）The specific surface area and roughness of In（OH）₃@GO can be effectively improved by adjusting the concentration of precursor,and the bending strength of cement-based materials can be further improved.The BET and AFM results show that when c(In³⁺)/c（GO）is 4,the specific surface area and surface roughness of In（OH）₃@GO are increased by 49.4%and 67.6%,respectively,and the 7-day and 28-day bending strength of cement paste are increased by 30.3%and 38.1%,respectively.（2）The size and distribution of spherical nano In（OH）₃ particles on GO surface can be effectively adjusted by changing the concentration of precipitator,and the specific surface area of In（OH）₃@GO can be further improved.The size of nano In（OH）₃ particles on GO surface increased first and then decreased with the increase of the concentration of precipitator and reductant.When the concentration ratio of precipitant to GO is 33 and the content of In（OH）₃@GO is 0.03%,the cumulative heat release of hydration of cement slurry increases by19.0%,the porosity of 28-day hardened cement slurry decreases to 14.41%,and the bending strength increases to 15.10MPa.（3）With the extension of hydrothermal time,the specific surface area of In（OH）₃@GO firstly increases and then decreases.When the hydrothermal time is 12 h,the specific surface area of In（OH）₃@GO reaches the maximum.Compared with the control group,the specific surface area of In（OH）₃@GO increased by 122.5%to 28.32 m²/g.（4）By controlling the hydrothermal temperature,the particle morphology of nano In（OH）₃on GO surface can be effectively regulated,and the specific surface area of In（OH）₃@GO can be further improved.When the hydrothermal temperature is lower than 140℃,the number of spherical nanoparticles In（OH）₃ on the GO surface increases gradually with the increase of the hydrothermal temperature,and the specific surface area of In（OH）₃@GO increases gradually.However,when the hydrothermal temperature exceeds 140℃,the nano In（OH）₃@GO on the GO surface changes from spherical to cubed and agglomerates obviously,resulting In a significant decrease in the specific surface area of In（OH）₃@GO.When the hydrothermal temperature is 140℃,the specific surface area of In（OH）₃@GO increases to 35.87 m²/g（5）The incorporation of In（OH）₃@GO can effectively reduce the porosity and water absorption of cement paste,and improve the flexural strength.At 0.03%In（OH）3@GO,the porosity,water absorption and bending strength of 28-day hardened cement slurry decrease by21.5%to 12.08%,46.8%to 5%and 36.9% to 14.1 MPa respectively.