Flexible concrete

Abstract

The invention relates to a cement powder blend comprising, based on total weight 45-90 wt. % non-Portland cement; 5-30 wt. % polyvinylalcohol; the blend having a content of 0-25 wt. % siliceous fly ash; and 0-25 wt. % limestone, preferably polyvinylalcohol having a size distribution with D.sub.10=170-270 μm, D.sub.50=370-450 μm, D.sub.90=690-850 μm and D.sub.100=1000-1300 μm. Further the invention relates to concrete composed of a blend according to the invention and aggregate.

Claims

1. A cement powder blend comprising, based on total weight 45-90 wt. % non-Portland cement; 5-30 wt. % polyvinylalcohol; the blend having a content of 0-25 wt. % siliceous fly ash; and 0-25 wt. % limestone, wherein the polyvinylalcohol has a size distribution with D.sub.10=170-270 μm, D.sub.50=370-450 μm, D.sub.90=690-850 μm and D.sub.100=1000-1300 μm.

2. The cement powder blend according to claim 1, comprising 50-80 wt. % non-Portland cement; and further comprising 5-20 wt. % siliceous fly ash; 5-20 wt. % limestone; and 5-15 wt. % polyvinylalcohol.

3. The cement powder blend according to claim 1, wherein the non-Portland cement is a geopolymer cement comprising metakaolin.

4. The cement powder blend according to claim 3, wherein the non-Portland cement is a geopolymer cement comprising a silica-based geopolymer represented by the formula (Na,K)-n(Si—O—)—(Si—O—Al—).

5. The cement powder blend according to claim 1, wherein the non-Portland cement is a geopolymer cement comprising a sol-gel-based geopolymer represented by the formula (Na,K)—(Si—O—Al—O—Si—O—).

6. A construction slurry of a cement powder blend according to claim 1 and water in a weight to weight ratio water to the non-Portland cement in the range of 0.2-0.7.

7. The construction slurry according to claim 6, wherein the construction slurry is a cement slurry.

8. A hardened construction slurry of claim 6.

9. The hardened construction slurry according to claim 8, wherein at least a substantial part of the polyvinyl alcohol is present in the form of hybrid particles composed of non-Portland cement and polyvinyl alcohol.

10. The hardened construction slurry according to claim 8, wherein the construction slurry is a hardened cement slurry having an expansion of 0-25% determined with sample length measurements during curing at 60° C.

11. The hardened construction slurry according to claim 8, wherein the construction slurry is a hardened cement slurry having a stiffness of 1.0-2.5 N/mm.sup.2 measured by means of direct tensile strength at 7 days, as measured at about 20° C.

12. A concrete comprising the construction slurry of claim 6; 20-50 wt. % fine aggregates, having a particle size of less than 4 mm; and 35-60 wt. % coarse aggregates, having a particle size in the range of 4-20 mm; with the proviso that the total aggregate content is 60-90 wt. %.

13. A product, comprising concrete according to claim 12, wherein the product is selected from the group consisting of infrastructural elements, buildings, concrete ware, and elements for pre-fab buildings.

14. The product according to claim 13, wherein the product is a building.

15. A cement powder blend comprising, based on total weight 45-90 wt. % non-Portland cement; 5-30 wt. % polyvinylalcohol; the blend having a content of 0-25 wt. % siliceous fly ash; and 0-25 wt. % limestone, wherein the polyvinyl alcohol has an ester value in the range of 1-250 mg KOH/g, as determinable by EN-ISO 3681:1998 and/or wherein the polyvinyl alcohol is a polyvinyl alcohol of which a 4% aqueous solution has a viscosity, at 20° C., as determined by EN-ISO 12058-1:2002, in the range of 1-40 mPa.Math.s.

16. The cement powder blend according to claim 15, comprising 50-80 wt. % non-Portland cement; and further comprising 5-20 wt. % siliceous fly ash; 5-20 wt. % limestone; and 5-15 wt. % polyvinylalcohol.

17. A construction slurry of a cement powder blend according to claim 15 and water in a weight to weight ratio water to the non-Portland cement in the range of 0.2-0.7.

18. The construction slurry according to claim 17, wherein the construction slurry is a cement slurry.

19. A hardened construction slurry of claim 17.

20. The hardened construction slurry according to claim 19, wherein at least a substantial part of the polyvinyl alcohol is present in the form of hybrid particles composed of non-Portland cement and polyvinyl alcohol.

21. The hardened construction slurry according to claim 19, wherein the construction slurry is a hardened cement slurry having an expansion of 0-25% determined with sample length measurements during curing at 60° C.

22. The hardened construction slurry according to claim 19, wherein the construction slurry is a hardened cement slurry having a stiffness of 1.0-2.5 N/mm.sup.2 measured by means of direct tensile strength at 7 days, as measured at about 20° C.

23. A concrete comprising the construction slurry of claim 17; 20-50 wt. % fine aggregates, having a particle size of less than 4 mm; and 35-60 wt. % coarse aggregates, having a particle size in the range of 4-20 mm; with the proviso that the total aggregate content is 60-90 wt. %.

24. A product, comprising concrete according to claim 23, wherein the product is selected from the group consisting of infrastructural elements, buildings, concrete ware, and elements for pre-fab buildings.

25. The product according to claim 24, wherein the product is a building.

26. The cement powder blend according to claim 15, wherein the non-Portland cement is a geopolymer cement comprising metakaolin.

27. The cement powder blend according to claim 26, wherein the non-Portland cement is a geopolymer cement comprising a silica-based geopolymer represented by the formula (Na,K)-n(Si—O—)—(Si—O—Al—).

28. The cement powder blend according to claim 15, wherein the non-Portland cement is a geopolymer cement comprising a sol-gel-based geopolymer represented by the formula (Na,K)—(Si—O—Al—O—Si—O—).

Description

EXAMPLE 1: PREPARATION OF CONSTRUCTION SLURRY FROM CALCIUM ALUMINATE CEMENT AND PVA

(1) A cement powder blend with 15 wt. % of polyvinyl alcohol (Mowiol 4-88), with ester value of 8 mg KOH/g, viscosity 28 mPa.Math.s and D.sub.10=233 μm, D.sub.50=440 μm, D.sub.90=767 μm and D.sub.100=1132 μm, combined with 85 wt. % calcium aluminate cement (Calumex Quick Caltra) was prepared. The resultant powder blend was mixed with water (in a weight to weight ratio water to powder blend of 0.4) to form a cement slurry (cement paste) at 20° C.

EXAMPLE 2: PREPARATION OF CONSTRUCTION SLURRY FROM CALCIUM ALUMINATE CEMENT, PVA, LIMESTONE AND FLY ASH

(2) A cement powder blend with 15 wt. % of polyvinyl alcohol (Mowiol 4-88), with ester value of 8 mg KOH/g, viscosity 28 mPa.Math.s and D.sub.10=233 μm, D.sub.50=440 μm, D.sub.90=767 μm and D.sub.100=1132 μm, combined with 55.25 wt. % calcium aluminate cement (Calumex Quick Caltra), 17 wt. % limestone and 12.25 wt. % fly ash was prepared. The resultant powder blend was mixed with water (in a weight to weight ratio water to powder blend of 0.4) to form a cement slurry (cement paste) at 20° C.

EXAMPLE 3: PREPARATION OF A REFERENCE CONSTRUCTION SLURRY FROM PORTLAND CEMENT, PVA, LIMESTONE AND FLY ASH

(3) A cement powder blend with 15 wt. % of polyvinyl alcohol (Mowiol 4-88), with ester value of 8 mg KOH/g, viscosity 28 mPa.Math.s and D.sub.10=233 μm, D.sub.50=440 μm, D.sub.90=767 μm and D.sub.100=1132 μm, combined with 55.25 wt. % CEM I 42.5 Portland cement, 17 wt. % limestone and 12.25 wt. % fly ash was prepared. The resultant powder blend was mixed with water (in a weight to weight ratio water to powder blend of 0.4) to form a cement slurry (cement paste) at 20° C.

EXAMPLE 4: SETTING TIME

(4) The initial setting time of the construction slurries according to Examples 1, 2 and 3 were evaluated. Results are shown in the Table below.

(5) TABLE-US-00001 Initial setting (min) Final setting (min) Ex 1 90 190 Ex 2 110 230 Ex 3 640 1000
It was shown that the construction slurries according to the invention, i.c. comprising calcium aluminate cement set much more quickly compared to construction slurries comprising Portland cement.

EXAMPLE 5: DIRECT TENSILE STRENGTH AT 7 DAYS

(6) The cement slurries of Example 1 and 2 were fully sealed with water on the surface and cured up to 7 days. Then the direct tensile strength of the hardened cement slurry was determined (following AASHTO T314-07) and stiffness was calculated from the strain-stress diagrams.

(7) Results of the test are presented in the Table below.

(8) TABLE-US-00002 Tensile Strength δl at Fmax Strain at break Elastic modulus (MPa) (mm) (%) (N/mm2) Ex 1 4.22 0.7 4.00 1.99 Ex 2 3.70 0.8 4.51 1.32

(9) From the experiment it was concluded that a flexible concrete according to the invention (made using a powder blend according to the invention) has a ductile behaviour. This property distinguishes the flexible concrete from normal concrete mixes. The ductility presented can have an effect in how a road is constructed and allow for less or no joints that will increase driving comfort. This property will not compromise the environmentally friendly aspect of concrete roads as the material remains a cement based material.

(10) Another important property of the flexible concrete is that the ductility is not directly connected to its strength which allows strength optimization without sacrificing the ductile character. This is also not common for normal concrete where there is a relationship between mechanical properties and elasticity.

(11) Usage of this material can vary as it has a good affinity both with concrete and with asphalt. This would allow usage in different pavement layers on top of already existing layers as a combination layer or even as a repair material.

EXAMPLE 6: PREPARATION OF CONSTRUCTION SLURRY FROM GEOPOLYMER CEMENT AND PVA

(12) Cement powder blend with 15 wt. % of polyvinyl alcohol (Mowiol 4-88), with ester value of 8 mg KOH/g, viscosity 28 mPa.Math.s and D.sub.10=233 μm, D.sub.50=440 μm, D.sub.90=767 μm and D.sub.100=1132 μm, combined with 85 wt. % geopolymer cement are prepared.

(13) The used geopolymer cements for different blends are either metakaolin or ground granulated blastfurnace slag (GGBS).

(14) The resultant powder blend is mixed with water (in a weight to weight ratio water to powder blend of 0.4) to form a cement slurry (cement paste) at 20° C.

(15) Setting time and tensile strength are determined as described in Examples 4 and 5 respectively.

EXAMPLE 7: PREPARATION OF CONSTRUCTION SLURRY FROM CALCIUM ALUMINATE CEMENT, PVA, LIMESTONE AND FLY ASH

(16) A cement powder blend with 15 wt. % of polyvinyl alcohol (Mowiol 4-88), with ester value of 8 mg KOH/g, viscosity 28 mPa.Math.s and D.sub.10=233 μm, D.sub.50=440 μm, D.sub.90=767 μm and D.sub.100=1132 μm, combined with 55.25 wt. % calcium aluminate cement (Calumex Quick Caltra), 17 wt. % limestone and 12.25 wt. % fly ash is prepared. The resultant powder blend is mixed with water (in a weight to weight ratio water to powder blend of 0.4) to form a cement slurry (cement paste) at 20° C.

(17) The used geopolymer cements for different blends are either metakaolin or Ground granulated blastfurnace slag (GGBS).

(18) Setting time and tensile strength are determined as described in Examples 4 and 5 respectively.