Effect of zeolite to clay ratios on the formation of zeolite-clay-white cement composite cylinder as an encapsulant of urea fertilizer

Zeolite-clay-white cement composite cylinders have been prepared for the encapsulant of urea powder. The composites were made by mixing natural zeolite, clay, and white cement at certain ratios using a home-made cylinder mold. All processes were done at room temperature. The composites were characterized using infrared (IR) spectroscopy and X-ray diffraction (XRD). Mechanical properties of the composites were evaluated through compressive strength and water absorption capacity test. The infrared spectra showed functional groups at 3448 and 1636 cm–1, indicating the presence of calcium silicate hydrate as the main product of hydration and pozzolanic reactions in the composite. The XRD patterns also confirmed the presence of calcium silicate hydrate as tobermorite (d = 3.34, 3.22, 2.75, and 2.28 Å) and jennite (d = 4.50 Å). Increasing the natural zeolite ratio in the composite decreased the compressive strength but increased water absorption capacity. The composite cylinders are envisaged as the encapsulant of urea powder and act as a slow-release fertilizer. © 2021 Trans Tech Publications Ltd, Switzerland.