Castable material based on cementitious binder with shrinkage resistance
Some embodiments are directed to a new castable cement based material containing a special admixture based internal curing system to reduce the shrinkage and avoid the formation of cracks, and method of producing the same.
1. A castable cement based material with enhanced shrinkage resistance, comprising:
a Portland cement based binder in an amount of at east 290 kg per cubic meters of fresh castable cement based material;
sand having a particle size less than 3 mm in diameter in an amount of between 500 Kg and 1600 Kg per cubic meters of fresh castable cement based material;
water;
a water/total binder ratio in weight located between 0.25 and 0.7;
an internal curing system;
a volume of paste in an amount of at east 300 l per cubic meters of fresh castable cement based material; and
fine aggregates having a particle size greater than 3 mm and less than 10 mm in diameter or/and coarse aggregates; wherein:
the internal curing system is in an amount of between 2 g to 30 g (dry solid content)/liter with respect to the total volume of paste;
the internal curing system contains at least a wax emulsion (A) in an amount in dry solid content with respect to the total binder content between 0.04 weight % to 1.35 weight %, and hexylene glycol (B) in an amount in dry solid content with respect to the total binder content is between 0.1 weight % to 3 weight %; and
the dry solid content ratio between the wax emulsion (A) and the hexylene glycol (B) in weight is between 0.2 and 1.0.
2. The castable cement based material according to claim 1 , wherein the internal curing system further contains a water retention agent (C) and/or a rheology modifier (D).
3. The castable cement based material according to claim 2 , wherein the water retention agent and/or rheology modifier is chosen from polysaccharides or polymers of acrylic acid.
4. The castable cement based material according to claim 2 , wherein the water retention agent (C) is a polysaccharide.
5. The castable cement based material according to claim 2 , wherein the rheology modifier (D) is chosen from at least one of acrylic acid, polyethylene, alkylene oxide polymers and its esters.
6. The castable cement based material according to claim 2 , wherein the amount of the water retention agent (C) in dry solid content with respect to the total binder content is located between 0.0025 weight % to 0.20 weight %.
7. The castable cement based material according to claim 2 , wherein the amount of the rheology modifier (D) in dry solid content with respect to the total binder content is located between 0.000075 weight % to 0.01 weight % (for rheology modifier being an acrylic acid) or 0.0005 weight % to 0.02 weight % (for rheology modifier being a polysaccharide).
8. The castable cement based material according to claim 3 , wherein the water retention agent (C) is a polysaccharide.
9. The castable cement based material according to claim 3 , wherein the amount of the water retention agent (C) in dry solid content with respect to the total binder content is located between 0.0025 weight % to 0.20 weight %.
10. The castable cement based material according to claim 4 , wherein the amount of the water retention agent (C) in dry solid content with respect to the total binder content is located between 0.0025 weight % to 0.20 weight %.
11. The castable cement based material according to claim 5 , wherein the amount of the water retention agent (C) in dry solid content with respect to the total binder content is located between 0.0025 weight % to 0.20 weight %.
12. The castable cement based material according to claim 3 , wherein the amount of the rheology modifier (D) in dry solid content with respect to the total binder content is located between 0.000075 weight % to 0.01 weight % (for rheology modifier being an acrylic acid) or 0.0005 weight % to 0.02 weight % (for rheology modifier being a polysaccharide).
13. A method of producing a castable cement based material as defined in claim 2 , the method comprising:
adding, separately from each other, wax emulsion (A), glycol-based shrinkage reducing agent (B), and water retention agent (C) and/or rheology modifier (D); and
performing the adding before, during or after mixing of the other components of the castable cement based material.
14. The method according to claim 13 , further comprising the steps of mixing wax emulsion (A), glycol-based shrinkage reducing agent (B), rheology modifier (D) and water retention agent (C) in an admixture, and adding the admixture to other components of the castable cement based material.
15. The method according to claim 14 , wherein the component D has a dosage (dry solid content) ranking from 0.015% to 0.2% in weight of the admixture containing all the other components A, B, water and C.
16. The method according to claim 14 , wherein the dry solid content ratio between components A and component B in weight is typically located between 0.2 and 1.0.