Experimental Study on the Improvement of Red Mudstone Filler by Calcium Lignosulfonate-fiber and MICP Synergistic Effect

In order to enhance the microbial improvement effect of red mudstone filler, calcium lignosulfonate and basalt fiber were used as admixtures to cooperate with microorganisms to improve the red mudstone filler. The MICP mixing method was used to test the physical and mechanical properties of the red mudstone filler. The effects of different amounts of calcium lignosulfonate and basalt fiber on the unconfined compressive strength, failure characteristics, no-load expansion rate and disintegration resistance of the red mudstone filler treated by MICP mixing and their changing laws were studied through relevant experiments. The mechanism of calcium lignosulfonate-basalt fiber and microorganisms in the improvement of red mudstone filler was revealed. The results show that: (1) Compared with the MICP group, when the content of calcium lignosulfonate and basalt fiber is 3% and 0.2% respectively, the synergistic improvement effect of the sample is the best, the longitudinal wave velocity is increased by 39.49%, the unconfined compressive strength is increased by 134.55%, and the peak strain at failure is increased by 32.34%. The calcium lignosulfonate-fiber and MICP synergistic effect can significantly improve the compactness, strength, and deformation resistance of red mudstone filler. (2) After the addition of calcium lignosulfonate and basalt fiber, the no-load expansion rate of the red mudstone filler is reduced by 53.84% ~ 73.07%, and the disintegration of the optimal content group sample is improved from moderate disintegration to no disintegration. (3) The mechanism of calcium lignosulfonate and basalt fiber synergistic with microorganisms to improve the red mudstone filler mainly includes three aspects: the cementing and filling effect of lignin polymer, the reinforcement effect of basalt fiber, and the synergistic promotion effect of calcium lignosulfonate and basalt fiber on MICP. The research results can provide new ideas for the improvement of red mudstone filler materials in high-speed railway subgrades.