고로슬래그와 아라미드 섬유를 이용한 보강그라우트재 특성 연구

Abstract

Various grouting methods have been used recently to secure the stability of the ground in civil engineering works at the sites such as old reservoirs and dams. The grouting method is used for reinforcement and waterproofing of soft ground and restoring foundation and increasing bearing capacity of the structured damaged by subsidence and uneven subsidence due to lowering or rising of groundwater level and vibration at reservoir or dam. The cement is commonly used as a binder in ground improvement method such as grouting method, however these cement materials may cause environmental problems. The replacement of cement with a large amount of admixture, an industrial byproduct, has been increasing as an effort to reduce the amount of cement used. In the grouting field for improving ground, the rapid drop in fluidity and rapid hardening of furnace slag in early phase may be advantageous and the strength of grout material, unlike cement concrete, does not require initial high strength. In addition, cement is a brittle materials and have poor resistance against tensile and horizontal forces. The purpose of this study was, therefore, to develop a ground improvement method of higher resistance, an recently raised domestic issue, by improving tensile and horizontal force with aramid fiber. For the purpose, this study used furnace slag fine powder, cement, and recycled aramid fiber. The calcium hydroxide was used as a furnace slag fine powder for membrane destruction by latent hydraulic activity. To avoid the environmental problems caused by existing LW method, various laboratory tests were performed based on above mixing materials before site application and optimum mixing ratio was determined by analyzing the increase in compressive strength due to lateral force improvement, a characteristics of fiber material, durability, and establishment of compressive strength and waterproof due to replacement with large amount of furnace slag fine powder. In order to confirm the effect of strength improvement by grout material, geltime and uniaxial compressive strength tests on related homo-gel and sand-gel were performed. In addition, permeability tests to determine waterproof effect, SEM and EDX analysis to characterize the ground enforced by addition of fiber demolition agent, and heavy-metal leaching test and pH test to determine environmental effect were performed. The results of laboratory tests showed that the uniaxial compressive strength of both homo-gel and sand-gel increase with the increase in contents of fiber demolition agent and processing rate of surface agent, suggesting that the bridging activity caused by aramid fiber in cement material promotes uniaxial compressive strength. The highest 3-days and 28-days strengths in homo-gel were found to be C:B 100 : 0% and O:A 1.2 : 1.0% of C:B 40 : 60%, respectively. and these of sand-gel were O:A 1.2 : 1.0% of C:B 40 : 60% in both cases. The permeability coefficient was lowest in C:B 40 : 60%, suggesting that the this new mixed material of this study has excellent waterproof effect according to mixing rate of furnace slage fine powder and aramid fiber, therefore, is expected to be used as a cut off wall grouting material in the field.