Abstract: Fly ash is one of the numerous substance that cause air, water and soil pollution, disrupts ecological cycles and set off environmental hazards. Fly ash produced during the burning of powdered coal in thermal power plants is a hazardous waste. Disposal of this enormous amount of fly ash faces problem of huge land requirement, transportation, and ash pond construction and maintenance, which can be reduced by utilizing fly ash as a construction material for civil engineering structures. Soil stabilization has been implemented for improving soils, which have inadequate engineering properties. An attempt has been made in this present paper to highlight on the pollution hazards due to the disposal of fly ash into the environment and its utilization in civil engineering activities by conducting some laboratory investigations. This paper describes a research that is carried out to study the effect of gypsum and fly ash on compaction properties and California bearing ratio values of silty sand. Different percentages of fly ash (i.e. 10, 15 and 20%) alone and with combination of gypsum (i.e. 2 and 4%) were added to the soil in order to evaluate the optimum moisture content and maximum dry density. The given result of specimens illustrate that the combination of gypsum and fly ash in soil is more effective than fly ash treatment alone.