Abstract: A free aggregate usable in forming wood concrete products is formed of a plurality of individual wood pinchips encased in kaolin to a degree sufficient to seal in water soluble "cement poisons" held in the pores of the chips, while maintaining the individual chips in a free aggregate form. The product is formed by a process which includes the step of encasing the individual particles with a mineralizing coating of the kaolin to a degree sufficient to seal in the water soluble cement poisons. As a preliminary step, the pores of the chips are sealed with an aluminum sulphate-water solution. Once cured, the chips are dimensionally stable, will not deteriorate and are not easily influenced by environmental conditions. Moreover, since the cement poisons are sealed within the chips, they cannot leach out to suppress hardening of a portland cement mix into which the chips may be introduced to form an aggregate in the formation of wood concrete products.