Shear Strength Improvement of Clay Soil Stabilized by Coffee Husk Ash

Finding alternatives to natural resources is important for a sustainable future and is essential to infrastructure projects. Among these replacements is the use of coffee waste as soil stabilizers. Coffee husk ash (CHA) is a solid waste obtained by the processing of coffee beans on a farm or factory. The main aim of this study is to determine the geotechnical properties of clay soil treated with CHA to develop a low-cost, environmentally friendly alternative composition. Laboratory tests were conducted to investigate the influence of CHA on the physical properties and the mechanical properties of clay. The CHA concentration was adjusted from 5% to 25% by the dry weight of clay in 5% increments. The clay classification of the mixture becomes coarser following the addition of the CHA. At 25% CHA, a peak UCS of 130.83 kN/m(2) was measured compared with the untreated clay of 89.17 kN/m(2). In addition, the cohesion values and internal friction angles of soil for 0% and 25% CHA increased from 80.1 kN/m(2) to 148.7 kN/m(2) and from 16.1 degrees to 25.8 degrees, respectively. It was found that CHA can improve the strength of clay by forming a pozzolanic and hydration process that fills soil voids and binds particles together.