Cementitious compositions in which the cementitious properties of fly ash are carefully controlled are described. The cementitious compositions may be substantially free harsh acids and bases such as citric acids (≈pH 2.2) and alkali metal activators including alkali hydroxides (≈pH 12-14) and metal carbonates (≈pH 11.6). The use of these harsh chemicals creates acid base reactions during use of the products. Instead of these harsh chemicals, a lactic acid salt based activator is be used as a reaction accelerator. Boric compounds may be used as a retarder in the compositions.