دانلود رایگان مقاله اثر میدان الکتریکی و در صورت شکست TSA از مواد مبتنی بر سیمان

Abstract

The impact of electrical field on the sulfate attack of cement-based materials at low temperatures was studied to rapidly detect Thaumasite Sulfate Attack (TSA) in the laboratory and in future engineering. Sulfate attack of cement paste with 30 wt% replacement of CaCO3 powder soaked in Na2SO4 solution, MgSO4 solution, or CaSO4 solution was measured under the condition of 5 ± 2 °C when an electrical field was applied. Appearance changes and compressive strength of the samples were tested to evaluate the corrosion degree. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopic measurements were applied to study the microstructure of the corrosion product. The test results indicate that sample damage was obvious, compression strength declined rapidly, and ettringite and/or thaumasite were found in the corrosion product after applying the electrical field for 90 days. A muddy product with TSA characteristics was formed, and thaumasite composition was found in the corrosion product after applying the electrical field for 120 days when MgSO4 solution was used as the corrosion medium. It is confirmed that an electrical field can accelerate TSA failure in cement-based materials.

4. Conclusions and discussion

The present work investigated the effect of an electrical field on the TSA of cement-based materials. The results indicated that the electrical field can quickly accelerate the TSA process in the cathode area of cement-based materials when using Na2SO4 solution as the cathode and MgSO4 solution as the anode.(1) The results of SEM/EDS, XRD, and FTIR indicated that TSA clearly occurred due to the function of the MgSO4 solution and electrical field after 120 days. (2) Cement-based materials were more easily damaged by sulfate under an electrical field, which led to noteworthy reduction of compressive strength (particularly when the anodic solution was MgSO4, indicating that the electrical field accelerated TSA). (3) The electrical field mainly accelerated the migration of ions into the cement-based materials and the rates of the chemical reactions in the cement-based materials. However, more research is required on the mechanism of TSA under the action of electrical fields, especially the ion distribution (Ca2+, Mg2+, and SO4 2−) and pH at different sites in cement-based materials. Moreover, different electric field parameters should be researched in the future, e.g., electrical field voltage and electrical field period.