EXPERIMENTAL STUDY ON TENSILE STRENGTH OF POLYMER CURING AGENT/FIBER MODIFIED SAND

In this paper, the polymer curing agent and polypropylene fiber are used to reinforce sand in compound. The pull-out test is carried out on the remolded samples with different polypropylene fiber contents, curing agent contents and dry density to measure its tensile strength. The study compares the change regulation of tensile strength of sand before and after improvement, then analyzes its mechanism of composite reinforcement with scanning electron microscope(SEM). The experimental results show that the composite reinforcement of polymer curing agent and polypropylene fiber can significantly improve the tensile strength of sand. Fiber content, curing agent content and dry density have great influences on the tensile strength of modified sand. For specimens with the same dry density and polymer curing agent content, the tensile strength gradually increases with the increase of fiber content. For the specimens with 4% curing agent content and 1.5 g·cm^-3 dry density, as fiber content increases from 0.2% to 0.8%, the tensile strength increases from 79.06 kPa to 194.51 kPa. For the specimens with the same dry density and fiber content, the tensile strength increases as polymer curing agent content increasing. For the specimens with 0.8% fiber content and 1.5 g·cm^-3 dry density, the tensile strength increases from 63.16 kPa to 194.51 kPa as polymer curing agent content increases from 1% to 4%. As the dry density increase, the tensile strength first increases and then decreases with the peak at approximately1.55 g·cm^-3. Composite reinforcement has the advantages of physical and chemical reinforcement. Through the interaction force among fibers and sand particles and the bonding force of polymer among sand particles, tensile strength of the modified sand is greatly improved. The results of this study also provide some references for further research on composite reinforcement of sand soil and its engineering application.