| 摘要 |
PROBLEM TO BE SOLVED: To provide an additive for soil improvement capable of improving the flowability of a soil cement and improving excavational properties and workability due to the retention of flowability and further reducing the amount of surplus soil to be discharged by incorporating a carboxylic acid based polymer to be obtained by allowing a predetermined amount of a hypophosphorous acid (salt) to be present in polymerizing an acrylic acid based monomer as an additive for soil improvement. SOLUTION: In an apparatus equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen inlet tube are charged 150 pts.wt. water and heated to 100 deg.C in a nitrogen stream. Then, while maintaining the water at 100 deg.C under stirring, 460 pts.wt. monomer aqueous solution obtained by dissolving 353.5 pts.wt. acrylic acid and 17.3 pts.wt. sodium hypophosphite in water and 90 pts.wt. initiator aqueous solution obtained by dissolving 5.6 pts.wt. ammonium persulfate in water are continuously added dropwise over three hours, respectively. Further, the reaction solution is maintained at the same temperature for one hour to complete the polymerization. After cooling, the reaction solution is neutralized by the addition of 471 pts.wt. 40% sodium hydroxide and diluted with water to obtain an acrylic acid polymer. |
