Study On Durability Of GFRP Burs And GFRP Reinforced Concrete Members Under Salt And Alkaline Environment

A series of accidents were caused by corrosion of reinforcing steel bars during the use of reinforced concrete structures.The corrosion of steel bars is particularly serious,especially in severe environments such as high temperatures,high humidity,and salt corrosion.Every country in the world needs to spend huge sums each year to repair concrete buildings damaged by corrosion of steel bars.FRP(Fiber Reinforced Plastic)has good corrosion resistance.Using FRP bars instead of steel bars is an effective method to thoroughly solve the corrosion problems of steel bars in concrete structures.Among many FRP materials,GFRP ribs are cheaper and their performance can satisfy many conditions of use,so they are favored by researchers.With the wide application of GFRP materials,the durability of GFRP and GFRP concrete components has become a concern of many scholars.However,the research on the durability of GFRP is short,and the research focuses on the reinforcement material itself.The research content is single,especially the research on the degradation rule and life prediction of GFRP reinforcement materials and their components is almost blank.Based on the above,this paper systematically studied the law of strength degradation of GFRP bars.Based on this,the process of bonding degradation of concrete members of GFRP bars was analyzed in detail,and the service life prediction model of GFRP bars was proposed.The main contents of the thesis include the following aspects:(1)In this paper,the experimental study of GFRP ribs under corrosive environment was carried out.The effects of temperature,load level and corrosive environment to the tensile strength of GFRP bars were studied.The results show that the increase of temperature and the increase of load level will accelerate the degradation of GFRP bars.The salt corrosion resistance of GFRP bars is better than that of alkali corrosion resistance.(2)Based on Fick’s second law,the degration model of tensile strength of GFRP bars was deduced from theory,and the test results were used to verify the tensile strength degradation model.After verification,the degration model is in good agreement with the experimental results,and the derived degradation model is reasonable.(3)To study the osmotic erosion of chloride ions on concrete,a numerical model for the penetration of chloride ions in concrete is established.the degradation rules of bare and wrapped tendons are compared.The results show that concrete does not effectively protect the tensile strength of internal reinforcements.Therefore,the degradation model proposed in this paper can accurately describe the tensile strength degradation of GFRP reinforcements in actual projects.(4)This paper proposes a model of the GFRP concrete member’s adhesion degradation.Multiple sets of experimental data are used to solve the degration model.After verification,the proposed degradation model is reasonable.This paper further predicts the bond strength in consideration of the actual ambient temperature and humidity.In this paper,a series of durability performance studies have been carried out on GFRP bars and their components.Many practically meaningful conclusions have been obtained through the study.This paper has a strong guiding significance for the application of GFRP bars in practical projects and the formulation of relevant design specifications.