Studies On Characteristic And Test Methods Of Chloride Ion Transport Of Alkali-activated Materials

Portland cement and concrete products has been widely used in our daily life,with the development of the society and the environmental protection consciousness enhancement,the environment problem caused by Portland cement increasingly prominent.It's necessary to find a sustainable development materials to reduce the application of Portland cement,alkali-activated materials is one of them.Alkali-activated materials are mainly consist of alkaline activated agent and the gel composition.Caustic alkali and alkaline salt is common used as alkaline activated agent,gelled material mainly comes from industrial by-product,usually including granulated blast furnace slag,phosphorous slag,steel slag,fly ash and metakaolin,etc.The resistance of chloride ion penetration is important for material durability performance,but because of the high density of pore structure and complex chemical composition of pore solution,the resistance of chloride ion penetration of alkali activated material has less research.The transportation of chloride ions within cement-based materials is a complicated process,and the main methods for chloride ion transfer are natural diffusion and electric acceleration.Natural diffusion tests are consistent with the actual situation,but the test time is too long and the operation is complicated.so the electrical accelerated test methods has been put forward and improved,in order to the test results can accurately reflect the resistance of chloride ion penetration performance in a relatively short period of time.The non steady state migration tests(NT build 492)test and rapid chloride penetration test(ASTM C1202)are used to evaluate the chloride ion transport properties in concrete,but these two methods can or can't used in alkali activated materials still need further study.The results show that there is chloride concentration in the pore solution of cement-based materials,but there is no literature research on the phenomenon of alkali-activated materials.This paper used the non-steady state migration test and rapid chloride penetration test to study the effect of modulus of water glass,the amount of fly ash,alkali dosage and curing system on the chloride ion transport properties of alkali-activated mortar.Comparing the results of two kinds of test methods to analysis it's applicability in alkali activated materials.In this paper,the concentration of chloride ions in the pore solution of alkali-activated materials was studied.The studies on characteristic and test methods of chloride ion transport of alkali-activated materials shows that when increasing the modulus of water glass and alkali dosage in a certain range,the compressive strength and resistance to chloride ion transport properties can improved.The addition fly ash can reduce the compressive strength and the resistance to chloride ion transport properties,the steam curing condition adversely affected on the compressive strength and resistance to chloride ion transport characteristics.Electric transfer coefficient can indicate the chloride ion transport properties of alkali activated materials,charge passed may can't evaluate the chloride ion transport properties of alkali activated materials,there is not exist linear correlation between Electric transfer coefficient and charge passed,charge passed can not converted into electric transfer coefficient by a simple formula in alkali activated materials.The study of chloride ion condensation in pore solution of alkali activated slag paste shows that when compared with ordinary Portland cement paste sheet,alkali activated slag paste sheet needs longer time to reach distribution of chloride ions.The condensation of chloride ions in the pore solution of alkali-activated materials also exist.Condensation coefficient increases with the modulus of water glass and alkali dosage;fly ash instead of a certain amount of slag,with the substitution of fly ash increases,condensation coefficient increases first and then decreases;with the increase of chloride ion concentration in the solution,the chloride ion condensation coefficient decreased gradually.