EFFECT OF PVA SHORT FIBERS AND GEOGRID ON THE FLEXURAL STRENGTH OF CEMENT-MIXED SANDY SOIL.

Cement-mixed soil has been widely used in road and railway construction. Mixing cement with soil increases its bearing capacity, stiffness, and shear strength while reducing the compressibility and volume changes of the soil. However, using only cement can lead to sudden and brittle failure due to the low tensile and flexural strengths of cement-mixed soils. In this study, the flexural strength and deflection behavior of cement-mixed sand, reinforced with geogrids (single and dual layers) and short fibers (0.5% and 1%), were investigated. Two types of biaxial geogrids were employed, along with polyvinyl alcohol (PVA) fibers measuring 12 mm in length and 0.1 mm in diameter. Standard silica sand and 6% ordinary Portland cement (OPC) Type I served as the sand and binding materials, respectively. Fifteen beam specimens, each measuring 15x15x53 cm, were prepared and cured for 28 days before testing. The experimental findings revealed that both the fiber content and the addition of biaxial geogrids improved the flexural behaviour of the cement-mixed sand. Specifically, incorporating fibers (0.5% and 1%) and dual-layer geogrids increased the first peak (f1) strength by 1.25 times and the peak strength by 2.53 times. Additionally, this reinforcement strategy enhanced crack patterns and distributed flexural loads across different parts of the beam specimens, resulting in multiple crack failure modes. Overall, the combined use of geogrids and fibers effectively reinforced the cement-mixed soil, producing a stress-deflection curve similar to that of steel bar-reinforced concrete, an improved failure mode, and the highest flexural strength. [ABSTRACT FROM AUTHOR]