a plasma arc torch heat based apparatus and method converts a quantity of particulate soil having a first set of engineering properties into a selected number of smaller quantities each having improved engineering properties differing from the first set of engineering properties and makes practical utilization of the smaller quantities for applications in which the first set of engineering properties were not suited . the apparatus includes a rotatable kiln which is positionable at an angle to horizontal such that soil is received in an upper end and discharged at a lower end thereof . the kiln is heated to a controlled temperature based on the properties of the soil before treatment and the desired improved properties after treatment to meet application requirements .