Fly ash-based cementitious mixture

A method of forming a building product comprising:

• providing a Class C fly ash with at least 15% by weight of CaO equivalent;
• forming a cementitious mixture, wherein forming the cementitious mixture includes:
• forming a hydraulic binder mixture comprising between 75 to 100% by weight of the Class C fly ash;
• adding one or more aggregates comprising between 10 and 80% by weight of the cementitious mixture;
• adding a set control system comprising between 0.04 and 5% by weight of the cementitious mixture, wherein the set control system includes a mixture of 1 part boron in salt or acid form and between 3 and 27 parts of dextro (L+) tartaric acid by weight;
• adding between 3 and 25% by weight of water to the cementitious mixture;
• mixing the mixture and water in air while applying shear forces;
• vibration compacting the mixture into a shape under a confining pressure less than 345 kPa;
• and
• hardening the vibration compacted mixture at a temperature below 100° C. and in the presence of water.