Research On Loess Reinforced By Modification Sodium Silicate

The sodium silicate is one of widely used chemical grouting materials now, with irrigation, low cost, adaptability, non-toxic, etc. But it will aging, the effects of aging result in the loss of bond strength up to30%～35%. Now sodium silicate used in engineering practice rarely consider the effects of aging. For better solidification effect, sodium silicate was modified by various methods. The mechanical strength of loess reinforced by modified sodium silicate was studied. The physical component such as chemical composition and mineral composition, microstructure were tested and analyzed by carrying out x-ray diffraction, scanning electron microscope and mercury porosimeter. Find the way of modification of sodium silicate which usded in foundation reinforcement in loess region. There are important scientific significance and application value for modified sodium silicate and reinforcement of rock and soil in loess region.(1) The mechanical strength of loess reinforced by temperature modified sodium silicate was studied. The results showed that the mechanical strength of loess was improved obviously with the temperature of sodium silicate increasing. Diffraction intensity of parts of the mineral was reducing in the X-ray diffraction patterns, and low density amorphous phase peak groups appeared. The SEM images showed that the gel films increased with the temperature of sodium silicate increasing. Surface area of pores increased with the temperature increasing. The findings indicate that the increased amorphous phase and the gel films caused to decreased most probable pore size and increased small pores. The mechanism of loess reinforced by temperature modified sodium silicate is due to reinforcement of the bond strength of cement in microstructure and formation of three dimensional networks of frame.(2) The mechanical strength of loess reinforced by compound modification sodium silicate was studied. The results showed that the mechanical strength of reinforced loess was significant improved. Diffraction intensity of parts of the mineral was increasing in the X-ray diffraction patterns, and low density amorphous phase peak groups still existed. The SEM images showed that crack of gel films reduced, and bonding relatively tended to close. Surface area of pores increased and mode pore diameters reduced after sodium silicate modified. The mechanism of loess reinforced by compound modification sodium silicate is due to reinforcement of the bond strength of cement in microstructure.(3) The freezing-thawing resistance of loess samples reinforced by modified sodium silicate compared to unmodified samples have been greatly improved. There is a certain critical value between mass loss, strength loss and freeze-thaw cycles. The mass loss increased sharply and strength drastically reduced when freeze-thaw cycles reach a certain number of times. Silicic acid gel films make pore connectivity bad and moisture migration more difficult. When free water in the pores freeze resulting in non-uniform temperature stress. These effects damage the links between the skeleton particles and weaken its cementation. A further weakening of the cementation will occur in the melting process. After repeated freeze-thaw cycles, the partial skeleton of the microstructure of the sample particles damage, micro-structural damage and the specimen strengtha decrease.