Strength Behaviors of PP Fiber-Reinforced Soil

Soil mixing method is a simple and economical operation in ground improvement. In recognizing carbon deduction during construction, it is important that the compressive strength, tensile strength, and bending moment can meet the requirement under working condition while reducing the amount of cement used. In this paper, we utilized Ottawa sand, Portland cement, and polypropylene (PP) fiber as the reinforced material to evaluate the mechanical behaviors of the material due to the addition of PP fibers. Specimen configurations include 5% cement addition by weight, water–cement ratios 1.0, PP fiber additions (0, 0.25%, 0.5%, and 1.0% by weight), and fiber length (6 and 12 mm). Unconfined compressive tests, Brazilian tests, and 3-point bending tests were performed to evaluate the effectiveness of fiber reinforcement through peak strength ratio, brittleness index, and toughness index. Test results indicated that at 28 curing days, the compressive strength, tensile strength, and bending moments capacity increased by 17%, 13%, and 28%, respectively. Furthermore, adding PP fibers increases the toughness so that the use of reinforcing steel can be reduced for diaphragm wall construction.