Systemical investigation on the determination of sulfate in cement-based materials based on a promoted conductometric titrator

Abstract

The concentration of sulfate ion in cement-based materials is the basic data for the design and evaluation of concrete structures exposed to sulfate lakes and saline soil areas. In this study, a conductivity titrator was developed and used to test the sulfate concentration in concrete corroded by sulfate attack based on the Internet of Things. The theories of conductivity measurement and conductivity titration were described; The main hardware composition and software design of conductometric titrator were introduced; Then, the effects of temperature, concentration, hydroxyl ion and hydrogen ion on the conductivity of solution of sodium sulfate and barium chloride were explored by the titrator; The titration parameters, the influence of hydroxyl and hydrogen ion on sodium sulfate titration were determined by test of sulfate ion titrated by barium chloride with known concentration; Finally, the titrator was used to test the sulfate concentration in cement-based materials after sulfate attack. The results show that the titrator can measure the conductivity of solution with 0.4% accuracy and the concentration of sulfate ion with 0.8% accuracy; During the titration of sulfate ion, the concentration of barium chloride should be twice that of sulfate ion, the titration rate should be less than 0.828 mL/s, and the titration volume should be at least 10 mL; It is found that the influence of hydroxyl ion can be effectively eliminated by adding nitric acid or hydrochloric acid, and the influence of hydrogen ion can be effectively eliminated by adding sodium carbonate. This conductivity meter can accurately test the sulfate concentration in the concrete after corrosion.