mixing with fiber bundles of 40 mm or with polypropylene fibers of 6 mm, were cured for 28 days and tested to show the relationship between their strength versus fiber contents. When the fiber content was 2%, the relationship
between strength versus fiber contents is approximately linear. The fiber bonds and tensile strength provided by fibers were the main source of improvement for specimens with low cement contents. However, for the specimens with cement content of 4% and 6%, it appears that the cementation effect became the dominant source of improvement and that excessive fibers do not further assist in increasing the strength of improved clay. The