A method of treating a shell sand by heating it to 300.degree. C. maximum for a time sufficient to remove substantially all of the water and organic content while maintaining substantially all of the inherent porosity of the shell sand. Generally, the time required varies between 10 minutes maximum at 300.degree. C. to about 1 hour at 95.degree. C. The resulting material is useful in cementitious compositions, particularly mortars, these being characterised by a high flexibility and an exceptionally high degree of resistance to fire or heat.
A protective coating on a metal surface comprises a particulate material produced by a method including heating an animal skeletal material to a temperature of at least 1000.degree. C. for a time sufficient to convert at least part of the calcium carbonate in the skeletal material to calcium oxide and produce a calcined product; and then contacting at least part of the calcined product with water to produce the particulate material containing calcium hydrate.
