Waste phosphogypsum was heated at 210-230 degrees C for 0.25 h in a fluidization column and mixed with fly ash (20%), cement (5%) and sand (5%) to prep. binders for stabilization of road surface subsoil. Magnetic pretreatment of water used for prepn. of the composite materials (magnetic induction 1 T, exposure time 0.5 h) resulted in an increase in compressive strength of the mixts. (by 65%) and their frost resistance (by 22%).