TIPA Promotes The Dissolution Mechanism Of Aluminum Phase And Its Effect On The Mechanism Of Hydration And Chloride Ion Binding

Due to the increasing scarcity of river sand resources and the development of regional resources,people began to pay attention to the resource utilization of sea sand.However,chloride ions in sea sand have the risk of steel corrosion and have the potential to damage the reinforced concrete structure.Binding chloride ions is an important means of solving this problem.Chemical binding is relatively stable due to the relatively stable hydration products Friedel salt and Kuzel salt formed by the chloride ion and AFm phase,and is considered to be an effective means for solidifying chloride ions.The formation of the AFm phase is closely related to the aluminum phase eluted in the system.Based on the“13th Five-Year”National Key R&D Program Sub-project-The research and application of chloride binding and new transportation resistance technology in sea-sand concrete.This paper proposes to use triisopropanolamine（TIPA）to promote the dissolution of aluminum phase in fly ash,ground granulated blast furnace slag and lithium slag,so as to achieve the purpose of improving the solidification of chloride ions.The hydration performance and chloride ion binding mechanism of cement-based materials were studied in detail.The cement-based materials mainly include cement-fly ash cementitious material system,cement-ground granulated blast furnace slag cementitious material system and cement-lithium slag cementitious material system,and also studied the effect of TIPA on ion elution of supplementary cementitious materials in pore solution.Combined with various modern testing methods,it analyzes macroscopic mechanical properties,microscopic hydration process and hydration products.Provide theoretical support for the solidification behavior of chloride ions for concrete.The results of this paper show that:（1）In the simulated concrete pore solution,because the three supplementary cementitious materials contain a large amount of aluminum phase and silicon phase,TIPA has a chelation effect on the aluminum phase and the iron phase,which promotes the disintegration of the structure resulting in the dissolution of the aluminum and silicon phases in the supplementary cementitious materials.For aluminum ions,the amount of aluminum ions eluted in the pore liquid increases with the increase of TIPA concentration.For silicate ions,TIPA also promotes the dissolution ability of the supplementary cementitious material in the immersion pore liquid.In the fly ash and lithium slag,it is shown that the concentration of silicate ions increases with the increase of TIPA content,and the silicate ions consumption in the granulated blast furnace slag due to its inherent hydraulic property in an alkaline environment.increase.The most obvious change is iron ions.When there is no TIPA,the iron ions in the pore liquid are not dissolved or eluted in a small amount,but once TIPA is added,the dissolution rate of iron ions is greatly increased.（2）The addition of TIPA promotes the hydration of cement-based materials,including accelerated hydration of cement and accelerated hydration of supplementary cementitious materials.At the same age,as the amount of TIPA increased,its strength increased.The addition of TIPA promoted the conversion of AFt to AFm,which increased the content of AFm in the system;at the same time,the content of calcium hydroxide in the system was reduced due to the addition of TIPA.Mainly because TIPA promotes the pozzolanic reaction of the supplementary cementitious materials,causing the calcium hydroxide to be consumed in a large amount.TIPA promotes the hydration of cement and the hydration of supplementary cementitious materials,the reaction rate is increased,the average chain length of C-S-H gel increases,and the Al/Si ratio also increases.（3）The dose of TIPA affects the chloride ion binding mode and the binding properties of chloride ions in the research system.The chloride ion binding of cement-based materials mainly involves physical adsorption and chemical reaction.From XRD and TG-DTG,the chemical generation of Friedel salt and Kuzel salt is increased.The amount of Friedel salt and Kuzel salt varies with the Al³⁺/SO₄^2-.When the amount of gypsum in the cement is constant,TIPA promotes the dissolution of aluminum ions in the system,resulting in an increase in the amount of AFm,and the AFm phase reacts with chloride ions to form Friedel salt and Kuzel salt.Physical solidification is mainly concerned with the adsorption of C-S-H gel.It can be seen from the analysis of NMR that the addition of TIPA promotes the hydration of cement and the pozzolanic reaction of supplementary cementitious materials,which makes the average chain length of C-S-H gel grow,and the effect of physical adsorption of chloride ions is enhanced.