Erosion Resistance Of Silicate-Sulphoaluminate Compound System Cement Concrete In High Concentration Magnesium Sulfate Solution

To solve the problem that the concrete structures were faced high concentration sulfate, magnesium salt erosion in Xinjiang region, the experiment studied the erosion resistance of sulphur aluminate cement concrete, silicate-sulphur aluminate compound cement concrete and silicate-sulphur aluminate compound cement with the mineral admixture concrete with the method of "immerse erosion resistance test method"(K), and observed mortar specimen microscopicly with the methods of scanning electron microscope(SEM) and energy spectrum analysis(EDS) etc. The result of the experiment showed that:(1)The resistance of sulfate aluminate cement concrete to separate sodium sulfate erosion was limited. When the concentration of sulfuric acid root ion was 〔SO42-〕≤20250mg/L, sulphur aluminate cement mortar specimen had good erosion resistance. However, when the concentration of sulfuric acid root ion was 〔SO42-〕≥60000mg/L, whether mortar specimens could keep erosion resistance ability under the condition of long age needed further research.(2)When the concentration of sulphate, magnesium salt erosion was 〔SO42-〕≤20250mg/L、〔Mg2+〕=15200mg/L, sulphur aluminate cement mortar specimen had good erosion resistance. However, the concentration of magnesium ion was fixed 〔Mg2+〕=15200mg/L), when the concentration of sulfuric acid root ion was 〔SO42-〕≥60000mg/L, mortar specimen was damaged on surface and loss the ability to resist erosion soon.(3) In the erosion solution 〔SO42-〕≤20250mg/L,〔Mg2+〕=15200mg/L, although the silicate- sulphur aluminate composite system cement concrete had no obvious erosion damage appearance, but corrosion resistance coefficient of a downward trend. The mortar specimen could not resist the damage of magnesium sulfate salt erosion solution.(4) In silicate- sulphur aluminate composite system cement concrete, slag was easier to play the potential activity than fly ash. In the solution of sulphate, magnesium salt erosion(〔SO42-〕≥60000mg/L、〔Mg2+〕=15200mg/L), silicate- sulphur aluminate compound system cement concrete mixed 40% slag could keep the erosion resistance of the composite cement system concrete well.(5) In the solution of sulphate, magnesium salt erosion and the concentration of magnesium ion was(Mg2+〕=15200mg/L) which was fixed, erosion damage form of mortar specimen was associated with sulfuric acid root ion concentration. Basically has the following two kinds:When〔SO42-〕≤20250mg/L, the erosion damage form given priority to magnesium salt erosion pattern. Although Mortar specimen had no obvious erosion characteristics,but the corrosion resistance coefficient decreases obviously. The main reason for erosion damage was the reaction of magnesium ion(Mg2+) and calcium hydroxide(Ca(OH)2). As the result,magnesium hydroxide without cementing ability was generated and hydrated calcium sulphoaluminate(AFT) was decomposed.When〔SO42-〕≥60000mg/L, the erosion damage form given priority to sulfate attack pattern. Mortar specimens not only corrosion coefficient decreased, but also appeared surface erosion damage phenomenon. The main reason for erosion damage was the reaction of magnesium sulfate(MgSO4) and calcium hydroxide(Ca(OH)2). As the result,magnesium hydroxide without cementing ability was generated and hydrated calcium sulphoaluminate(AFT) was decomposed. What was more, mortar specimen surface generated a large number of dihydrate gypsum crystals,which was the main cause of mortar specimen surface erosion damage.