Synthetic aggregate compositions derived from spent bed materials from fluidized bed combustion and fly ash

A method of preparing cementitious compositions comprising the steps of:

• collecting one part spent residue from a fluidized combustion bed;
• adding liquid water to the one part spent residue sufficient to form conditioned spent residue;
• adding 0.4-0.8 parts pozzolanic material to the one part conditioned spent residue to form a blend;
• adding liquid water at ambient temperature to the blend to form a blend product;
• forming the blend product into a shape;
• curing the shape at ambient temperature while maintaining the shape saturated with liquid water.

A method of preparing a shaped cementitious composition comprising the steps of:

• admixing conditioned spent bed material and fly ash at a ratio between 1.0:0.4 to 1.0:0.8 to form a blend;
• adding controlled amounts of water to the blend to form a blend product;
• forming the blend product into a shaped article;
• and
• curing the shaped article while maintaining ambient temperature and while saturating the shaped article with liquid water until the shaped article exhibits a dimensional change of less than about 0.0001 inches/inch per day.

A method of certifying a dimensionally stable synthetic aggregate formed from a blend of spent bed material and fly ash, comprising the steps of:

• forming a plurality of standardized test shape samples;
• testing one of said plurality at a first time to determine an initial value of X-ray diffraction pattern, percent weight loss on ignition and oven dry weight;
• testing another of said plurality after an interval to determine a revised value for at least one of an X-ray diffraction pattern, percent weight loss on ignition and oven dry weight;
• and
• determining whether the synthetic aggregate is dimensionally stable by comparing the initial value and the revised value.