Experimental study on influence of plasticizer on fluidity of convection- solidified silt

Compared with the traditional backfill materials, the performance-controlled fluidized solidified (PCFS) backfill materials are characterized by high flow state and self-compaction, which can effectively avoid engineering problems caused by insufficient compaction, especially for backfill in narrow areas. Using silt as raw materials and cement as curing materials, the PCFS materials with controllable properties such as strength, fluidity and setting time are prepared. The influences of different initial conditions on the fluidity of the PCFS materials are discussed through the flow tests. In order to improve the flow performance of the PCFS materials, three water reducing agents, calcium lignosulfonate, naphthalene superplasticizer and polycarboxylate superplasticizer, are selected, and the effects of three water reducing agents on improving the flow of the PCFS materials are compared and analyzed. The results show that there is a positive linear correlation between the fluidity of the PCFS materials and the initial water content. The addition of cement will lead to a significant decrease in the fluidity of the PCFS materials, which mainly occurs when the cement content is less than 2%. The increasing range of fluidity of the PCFS materials by the three water-reducing agents is from large to small in the order of polycarboxylate superplasticizer > naphthalene superplasticizer > calcium lignosulfonate, wherein the incorporation of polycarboxylate superplasticizer and calcium lignosulfonate will introduce bubbles, and the "saturated content" of naphthalene superplasticizer and calcium lignosulfonate is 2% and 4%, respectively. Different cement contents will make the three kinds of water-reducing agent to improve the flow effects have a significant difference. The increase of cement content reduces the effects of the calcium lignosulfonate, has samll effects on the polycarboxylate superplasticizer, and shows " anomalous effects" on the naphthalene superplasticizer. Finally, the causes of "saturation content" and "anomalous effects" are discussed, and the expression formula for fluidity of the PCFS materials under the initial water content of 2w_L and cement content of 5% is proposed.