Universal hydraulic binder based on fly ash type F
The present invention concerns the development of a simple, multipurpose, low cost, environmental friendly and safe binder formulation and related process, based on high volumes of alkaline activated class F fly ash residue (>760%) without ordinary Portland cement and related products, offering a wide scope of applications. More specifically, the universal binder is based on a very limited number of components (fly ash type F, Blast Furnace Slag and a mixture of alkali silicates and carbonates). The binder allows developing considerable strength at the early stage (at room temperature) and very high resistances at 28 days. The binder applies to pastes, mortars concretes and pre-cast with the same flexibility of an Ordinary Portland Cement.
1. A hydraulic cementitious binder manufactured from fly ash, blast furnace slag and a chemical activator comprising:
from 60 to 85 wt. % of fly ash containing less than wt. 8% of CaO;
from 8 to 28 wt. % of blast furnace slag; and
a chemical activator containing:
from 1 to 4 wt. % of alkaline silicates; and
from 7 to 11 wt. % of alkaline carbonates.
2. A cementitious binder according to claim 1 , wherein the fly ash is pure class F fly ash.
3. A cementitious binder according to claim 1 , wherein the fly ash has a specific surface from 200 to 500 square meters per Kg.
4. A cementitious binder according to claim 1 , wherein the blast furnace slag has a specific surface from 350 to 600 square meters per Kg.
5. A cementitious binder according to claim 1 , wherein the alkaline silicates are at least one of sodium silicates, potassium silicates, or lithium silicates; and the alkaline carbonates are at least one of sodium carbonates, potassium carbonates, or lithium carbonates.
6. A cementitious binder according to claim 1 , wherein the alkaline silicates are sodium or potassium silicates; and alkaline carbonates are sodium or potassium carbonates.
7. A cementitious binder according to claim 1 , wherein the chemical activator has an silica to alkali molar ratio from 0.1 to 0.4.
8. A cementitious binder according to claim 1 , further comprising industrial or agricultural residues containing either high alkalis content or highly reactive amorphous silica.
9. A mortar characterized in that it comprises water and sand mixed with a binder according to claim 1 .
10. A concrete characterized in that it comprises water, sand and aggregate mixed with a binder according to claim 1 .
11. A method to produce mortar or concrete based on a binder with the following composition:
from 60 to 85 wt. % of fly ash containing less than 8% w/w of CaO;
from 8to 28 wt. % of blast furnace slag; and
a chemical activator containing:
from 1 to 4 wt. % of alkaline silicates; and
from 7 to 11 wt. % of alkaline carbonates,
comprising the following steps:
a) Preparing an activator solution by dissolution of the chemical activator in water;
b) Mixing the activator solution with sand and/or aggregate, class F fly ash and blast furnace slag.
12. A method to produce mortar or concrete according to claim 11 wherein mixing the activator solution with sand and/or aggregate, class F fly ash and blast furnace slag comprising the following steps:
a) Preparing an initial mix by homogenisation of sand and/or aggregate, class F fly ash and water;
b) Preparing a hardening slurry mixture by homogenisation of the activator solution and the blast furnace slag;
c) Mixing the initial mix with the hardening mixture slurry.
13. A method according to claim 12 wherein the initial mix comprising from about 1 to about 5% by weight of water.
14. A method according to claim 11 , wherein the fly ash is pure class F fly ash.