Characteristics of water-swelling friction reducing materials on the pulling-out removal of temporary works

Water-swelling friction reducing materials (WSFRMs) are commonly used as a "pulling-out assisting material" for temporary works such as steel sheet-piles and H-steels that are required to be removed and collected after use. Generally, WSFRMs are coated to steel sheet-piles and H-steels before these are driven into the ground or placed in mortar fluid. The WSFRMs absorb moisture in the ground or mortar to swell and form a swelling membrane over the piles. Then, the membrane works also as a lubricating membrane and as a result it can reduce friction. The authors pay attention to these characteristics of WSFRMs and try to develop a special material that can swell only when soaked in an alkaline moisture environment without swelling in acid or a neutral water environment, in addition to the conventional material that swells in any type of moisture environment. In this paper, considering that both types (alkaline and conventional) of WSFRMs are used as "pulling-out assisting material" for temporary steel sheet-piles and H-steels, we perform through experiments on the swelling ratios of the materials as well as on the pulling-out characteristics of the steel flat-bar to which the WSFRMs are coated in advance.