Experimental investigation of the strength properties of sand-clay mixtures reinforced with randomly distributed discrete polypropylene fibers

This paper describes the findings of a series of laboratory unconfined compression tests and split tensile tests performed on specimens of varying fiber-sand-clay proportions. Sand was mixed with clay at six different proportions, namely 0.0, 1.0, 2.5, 5.0, 7.5, and 10.0% by dry weight of clay. Fiber was included in the sand-clay mixture at four different percentages, namely 0.0, 0.25, 0.5, and 1.0% by dry weight of clay. Compaction characteristics of the sand-clay mixtures were evaluated at standard compaction energy. According to fiber content, four groups of samples were prepared at maximum dry unit weight and optimum water content. For each of the four sample groups, unconfined compressive stress-axial strain and split tensile stress-diametrical strain behavior of the fiber-sand-clay mixtures were investigated. The test results showed that unconfined compressive strength (UCS) reached its maximum value at a fiber/clay ratio of 1.0% and sand/clay ratio of 7.5%. There was a reasonably strong linear correlation (R-2 approximate to 1.0) between UCS and average initial tangent modulus values. The ratio of UCS to split tensile strength (STS) for all fiber-sand-clay mixtures varied between 3.2- and 5.8-fold.