Experimental Study On Corrosion Of Organic Acid To Red Clay-Cemented Soil Pile

Ground water-soil surroundings may cause the subsurface structures erosion resulting in strength reduction and traping the building safety into risks, thus the research of influence on which is of great significant theoretical and practical value. This ariticle focused on the red clay-cemented soil, and through strength and immersion test to discuss the issues:relationships of red clay-cemented soil of uncomfined compression strength versus the cement mixing ratio and curing age, and interaction mechanisims between organic acid (citric acid, fulvic acid (FA), singicylic acid, oxalic acid) and red clay-cemented soil. This article mainly inverstigated the following items:(1) The uncomfined compression strength of the red clay-cemented soil composited mass can reach over2MPa, and the sensitivity of that decreases with the cement addition; the ratio of early strength to that after90days also tends to reduce with the increased cement addition, consequently, adopt the early strength to estimate the90days’should consider the mixture ratio.(2) There is a severe corrosivity to the composited mass by citric acid, the erosion process can be divided into the decline, stable and undulate stages of acid comsuptioin rate. When the pH>4.5, decomposition dissolution is the dominant reaction, and the crystallization expansion while pH<3.5; and it shows the two when the pH value ranges from3.5to4.5, the surface layer performs the decomposition dissolution and the other one within the specimen; an erosion prediction model is constructed under the condition.(3) Fulvic acid has some corrosivity to the composited mass conserved3days, while slight after37days. The erosion process clarifies to fast and slow sections, of which the former stage is the primary and the latter is weak.(4) Singicylic acid is of great corrosivity to the composited mass, and the smaller the pH value the more significant effect will show, and the foundamental of which is the decomposition dissolution to the cement hydration products; the overall erosion process consists of the descendant and steady phases of acid comsuption rate: the model f(t)=atb atbcan describe the acid comsuption versus the elapsed time well under different pH values.(5) The erosion process of the oxalic acid to the composited mass is of disintegration and recrystallization, cement hydration products and Fe2O3in the red clay-cemented soil are decomposed while indissolvable CaC2O4and FeC2O4are recrystallized, the erosion process includes the crystallization layer formation, transition and the rapid reaction periods, and the former two mainly show the disintegration and transformation of the cement hydration products, while the third period exists disintegration and transformation to both the cement hydration products and Fe2O3in the red clay.(6) The erosion process of composited mass is related to the pH value of organic acid solution, also the acid type is a crucial factor. Where there is a difference in erosion mechanisim for different acid type, there is a final different failure model.