Experimental Study On Mechanical Properties Of Cement Soil Under Ammonium Sulfate Erosion

In this paper,aiming at the characteristics of corrosion of cement soil structure by residual ammonium sulfate solution in rare earth mining in southern China,in order to improve the corrosion resistance of cement soil structure,in combination with the science and technology project of Jiangxi provincial bureau "Study on the Durability of Cement Base structure in the Highway Engineering of Earth Mining Area after In-situ Leaching"(NO.2014C007),and "the mechanism and control of the corrosion of cement soil in the ionic rare earth mining area of Jiangxi Province Natural Science Foundation Project"(NO.20151BAB206054),making a research on the law of the cement soil resisting corrosion of ammonium sulfate.Specific research contents include:(1)Five different concentrations of ammonium sulfate solution were used to test the cement soil specimen.Under the different soaking ages and ammonium sulfate concentration,variation regularity of apparent morphology,compressive strength and stress-strain curve of cement soil specimen were analyzed.Research shows: The apparent and mechanical properties of cement soil in the environment of ammonium sulfate impregnation are obviously changed,the greater the concentration of the solution and the longer the soaking age,corrosion effect is more significant;The corrosion resistance coefficient of cement soil in 1.5g/L ammonium sulfate solution decreased with age and then stabilized,the compressive strength of high concentration cement soil specimen increases slowly and then decreases rapidly with age,28 days to reach the maximum strength,but the erosion resistance is gradually weakened;The greater the cement content,the greater the compressive strength in the clean water,compressive strength and corrosion resistance in ammonium sulfate solution first increase and then decrease,when cement content reaches 20%,the maximum value is reached.(2)The dry wet cycle test of cement soil specimen was carried out with five different concentrations of ammonium sulfate solution.Under different cycle index and ammonium sulfate concentration,variation regularity of apparent morphology,compressive strength and stress-strain curve of cement soil specimen were analyzed.Research shows: The effect of wet and dry cycle of ammonium sulfate on the apparent quality and mechanical properties of cement soil was significant.The higher the concentration,the more obvious the corrosion effect.Wet and dry cycle of cement soil erosion resistance is higher in 1.5g/L ammonium sulfate solution.With the increase of the number of cycles,the compressive strength and corrosion resistance of cement soil under several other ammonium sulfate concentrations increases rapidly and then decreases slowly,the maximum value occurs when the loop times is 6.The compressive strength of cement soil increases with the increase of cement content.(3)Using the orthogonal test method,the effects of fly ash,slag,polycarboxylate superplasticizer and four kinds of additives on the corrosion resistance of cement soil specimen were studied.Research shows: Polycarboxylate superplasticizer is one of the most important factors affecting the mechanical properties of cement soil,in the clean water and ammonium sulfate solution,the best proportion of cement soil in dry wet cycle test is 40% fly ash,60% slag,0% polycarboxylate superplasticizer and NaOH 2%.Based on the scanning electron microscope(SEM)and element composition scanning test,the microstructure and corrosion resistance of several kinds of additives were studied,it is concluded that the microscopic morphology changes coincide with the changes of macro mechanical properties.