Strength of silty soil treated with cement and reinforced with plastic bottle waste under conventional and wetting-drying conditions

This research aims to study the engineering properties of silty soil reinforced with plastic waste fiber (PWF) extruded from water plastic bottles. Other reinforced soil samples have been treated with cement, except for control samples (untreated soil samples). Curing time, length and percentage of fiber are the variables studied in this research. Lab testing results show that adding plastic waste fiber to the silty soil helps to increase the unconfined compressive strength, indirect tensile strength and punching-tensile strength. The results of soil samples treated with 4% cement show that all strength values have increased significantly. These properties also increase with the increase in the curing time. The increase in strength values of natural soil samples compared with cement-treated samples was (91.7 kPa to 1800 kPa), (6.1 kPa to 312 kPa) and (12 kPa to 371 kPa) for the unconfined compressive, indirect tensile and punching-tensile strength for 28 days of curing time. Regarding the effect of wetting-drying cycles on the strength properties, the results show that the natural soil samples fall apart immediately after being soaked in water. However, the results for samples reinforced with plastic waste fiber, treated with 4% cement and cured for 28 days show that the unconfined compressive, indirect tensile and punching-tensile strength decrease with the wetting-drying cycle from (2500 kPa to 1000 kPa), (435 kPa to 189 kPa) and (580 kPa to 448 kPa), respectively.