Research On Durability And Life Prediction Of Nano-Modified Concrete In Corrosive Environment

Concrete is currently one of the most widely used building materials in construction engineering.In the saline soil environment of western China,due to the large amount of corrosive ions in the saline soil,the concrete has been eroded by the corrosive medium for long-term,and its durability gradually deteriorates until it fails.At present,how to improve the durability of concrete structures and how to extend their service life is the focus and difficulty of academic circles.At present,how to improve the durability of concrete structures and how to extend their service life is the focus and difficulty of academic circles.Nano-materials are hailed as one of the most important materials in the 21st century.Their special properties will undou btedly have a huge impact on building materials and even the entire civil engineering field.In order to study how to improve the durability of concret e and extend its service life in this paper,nano-CaCO₃ was used as an admixture for concrete to study th e resistance to sulfate corrosion resistance of nano-CaCO₃ modified concrete under different soaking methods.By periodically measuring the ultrasonic velocity and mass of the test piece,the compressive strength ratio Kα,the flexural strength ratio Kβ,the relative quality evaluation parameterω₁,the relative dynamic elastic modulus evaluation parameterω₂,the comprehensive damage evaluation parameterω,and the thickness of the corrosion layer d_f jointly characterizes the resistance to sulfate of nano-CaCO₃ modified concrete under different soaking methods.Combined with scanning electron microscopy（SEM）and X-ray diffraction analysis（XRD）micro-methods to study the microstructure characteristics of nano-CaCO₃ modified concrete after corrosion to reveal its deterioration mechanism.Based on this,driven by the measured life data,a variety of evaluation indicators were selected for processing and used as performance degradation indicators.The Wiener process was used as the degradation model of the nano-CaCO₃ modified concrete’s durability performance parameters after corrosion,and the life prediction was carried out.Mainly completed the following scientific research work and achieved corresponding results:（1）After the sulfate corrosion resistance test of nano-CaCO₃ modified concrete in the fully immersed state,the sulfate resistance of the specimens was analyzed based on various durability evaluation indicators.The study found that:from 0 to 180days,the evaluation parameters of the test pieces such asω₁,ω₂,Kβ,and Kαshowed an upward trend.However,ωand d_f began to change at 180days.According to the analysis,the appropriate addition of nano-CaCO₃ can enhance the resistance of concrete to sulfate corrosion,and the best effect is when the nano-CaCO₃ content is 1%.Microscopic tests show that there are corrosion products such as long rod-shaped,short columnar ettringite and slab-shaped gypsum inside the specimen after corrosion.These corrosion products can fill the concrete defects at the beginning of the test,but the corrosion inside the concrete will be exacerbated over time.（2）After the end of the sulfate corrosion resistance test of nano-CaCO₃ modified concrete in the half immersion state,the sulfate resistance of the specimens was analyzed based on various durability evaluation indicators.The study found that:from0 to 180days,the evaluation parameters of the test pieces such asω₁,ω₂,Kβ,and Kαshowed an upward trend,a downward trend from 180d to 360d,andωbegan to change at 180d.According to the analysis,the appropriate addition of nano-CaCO₃ can enhance the resistance of concrete to sulfate corrosion,and the best effect is when the nano-CaCO₃ content is 1%.The degree of concrete corrosion in different parts in descending order is:M area>D area>T area.Microscopic tests show that after th e corrosion,a large number of corrosive products such as rod-shaped ettringite crystals and gypsum gypsum crystals with well-developed and long crystal lengths appear inside the specimen,and white sodium decahydrate crystals also precipitate on the surface of the concrete.These corrosion products can improve concrete defects at the beginning of the test,but as the test time passes,it will cause cracks in the concrete,which will aggravate the concrete corrosion.（3）The Q-Q chart was used to verify various evaluation indexes of nano-CaCO₃modified concrete,and it was judged that the life prediction study of nano-CaCO₃modified concrete can be carried out through the Wiener random process.The study found that the remaining life of concrete specimens un der different soaking methods changed with the amount of nano-CaCO₃,and the effect was best when the nano-CaCO₃content was 1%.In actual engineering,when the content of nano-CaCO₃ is 1%,the resistance of concrete to sulfate corrosion will greatly incre ase,and the service life of concrete structures will also increase significantly.