High strength cement, mortar and concrete including industrial by-products
Cementitious compositions in which the cementitious properties of fly-ash are carefully controlled. 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 citric salt, for example potassium citrate, may be used as a reaction accelerator. Boric compounds may be used as a retarder in the compositions.
1. An article of manufacture comprising a hydrated and hardened cement composition comprising a pozzolan powder;
two or more activators, at least one of which has a pH between 6 and 9; and
a retarder,
wherein the hydratable cement has a calcium content expressed as the oxides of 15 wt % or more based on the total weight of the hydratable cement; and
wherein said activator having a pH of between about 6 and about 9 accounts for greater than 50% of the total weight of activators in said hydratable cement.
2. An article of manufacture comprising a hydrated and hardened cement composition comprising a pozzolan powder;
one or more pH neutral activators; and
a retarder,
wherein the hydratable cement has a calcium content expressed as the oxides of 15 wt % or more based on the total weight of the hydratable cement, and
wherein the pH neutral activators account for greater than 50% of the total weight of activators in said hydratable cement; and
wherein the hydratable cement has less than 20% by weight Portland cement based on the total weight of the hydratable cement.