FLY ASH BASED CASTABLE CONSTRUCTION MATERIAL WITH CONTROLLED FLOW AND WORKABILITY RETENTION

Abstract

A castable construction material with controlled flow and workability retention comprising (a) a binder comprising from 75% to 100% by weight of fly ashes comprising from 1.5% to 35% by weight of Ca O and a Lost on Ignition (LOI) value from 0.5% to 5.5% by weight, (b) an activator comprising an alkali hydroxide and an alkali silicate, wherein the activator is from 3% to 25% by weight with respect to the castable construction material, (c) sand, (d) fine aggregates, (e) coarse aggregates, (f) free water and (g) a workability retention agent wherein selected from the group consisting of polycarboxylate ether polymer (PCE), polyamines, polyethylene imines, polyacrylamides, polyacrylate (EO, PO) ester, polymethacrylate (EO, PO) ester, polyammonium derivatives and co-polymers thereof, polydiallyldimethylammonium chloride, benzalkonium chlorides, substituted quaternary ammonium salts, chitosans, caseins and cationically modified colloidal silica.

Claims

1. A castable construction material with controlled flow and workability retention comprising: (a) a binder comprising from 75% to 100% by weight of fly ashes comprising from 1.5% to 35% by weight of CaO and a Lost on Ignition (LOI) value from 0.5% to 5.5% by weight, (b) an activator comprising an alkali hydroxide and an alkali silicate, wherein the activator is from 3% to 25% by weight with respect to the castable construction material, (c) sand, (d) fine aggregates, (e) coarse aggregates, (f) free water and (g) a workability retention agent wherein selected from the group consisting of polycarboxylate ether polymer (PCE), polyamines, polyethylene imines, polyacrylamides, polyacrylate (EO, PO) ester, polymethacrylate (EO, PO) ester, polyammonium derivatives and co-polymers thereof, polydiallyldimethylammonium chloride, benzalkonium chlorides, substituted quaternary ammonium salts, chitosans, caseins and cationically modified colloidal silica.

2. Castable construction material according to claim 1, further comprising an element selected from the group consisting of from 0% to 25% by weight of ground granulated blast furnace slag comprising from 40 to 70% by weight of CaO and from 30 to 60% by weight of SiO.sub.2; from 0% to 25% by weight of pozzolans comprising from 4 to 7% by weight alkali and a Lost on Ignition (LOI) value from 0.01% to 7; and from 0% to 25% in weight of any combination of slag and pozzolans.

3. Castable construction material according to claim 1, wherein the ratio alkali hydroxide/alkali silicate is from 1:1.5 to 1:2.5.

4. Castable construction material according to claim 1, wherein said alkali hydroxide is in solution, wherein the weight solid content of said alkali hydroxide in the solution is from 30 to 50% by weight and the molarity of said alkali hydroxide in the solution (mole per liter of free added water) is from 2.5 to 6.

5. Castable construction material according to claim 1, wherein said alkali silicate is in solution, wherein the weight solid content of said alkali silicate in the solution is from 30 to 50% by weight and the molarity of said alkali hydroxide in the solution (mole per liter of free added water) is from 1 to 2.5.

6. Castable construction material according to claim 1, wherein the concentration range of said polycarboxylate ether polymer is from 0.12% to 0.75% by weight of total binder.

7. Castable construction material according to claim 1, wherein concentration of fly ashes is from 80% to 100% by weight.

8. Castable construction material according to claim 1, wherein said alkali silicate is sodium metasilicate.

9. Castable construction material according to claim 5, wherein the molarity of said alkali silicate is from 1 to 1.8.

10. Castable construction material according to claim 5, wherein the molarity of said alkali silicate is from 1.2 to 2.0.

11. Castable construction material according to claim 5, wherein the molarity of said alkali silicate is from 1.5 to 2.2.

12. Castable construction material according to claim 5, wherein the molarity of said alkali silicate is from 1.8 to 2.3.

13. Castable construction material according to claim 5, wherein the molarity of said alkali silicate is from 2 to 2.5.

14. Castable construction material according to claim 1, wherein said workability retention agent is in a dosage in dry solid content from 0.15 to 0.6%.

15. Castable construction material according to claim 1, wherein said workability retention agent is in a dosage in dry solid content from 0.6 to 1.2%.

16. Castable construction material according to claim 1, wherein said workability retention agent is in a dosage in dry solid content from 1.2 and 1.6%.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0068] FIG. 1. Shows the dependence between the flow of the fresh castable material and the dosage of the activator for a first embodiment according to the invention where the binder is pure fly ash. Results were obtained by preparing mortar samples with two different fly ashes (see Table 3 for reference fly ash LA and fly ash AND), and a standard 0-4 mm sand, at different activator dosages. Activators were dosed at a constant ratio, and the dosage was expressed as molarity based on the total water. The targeted flow was 15010 mm and the water demand to achieve was recorded and expressed as water to binder ratio. The water demandflow of the geopolymer mortar varied significantly when changing the dosage of the activator system.

EXAMPLES OF THE INVENTION

[0069] The examples have been prepared using various fly ashes and ground granulated blast furnace slags; chemical compositions are respectively indicated in Tables 3 and 4.

[0070] Mortar samples have been prepared using standard 0-4 mm sand, concrete-like samples have been prepared using sand 0-4 mm (natural opr crushed), medium size 4-8 mm round or crushed and large aggregates 8-16 to maximum 25 mm (round or crushed).

[0071] Mortars and concrete are mixed using standard equipment, for a time of 20 seconds to some minutes. All mortars and concretes were prepared by mixing all ingredients with no specific sequence or methodology to be close to industrial conditions. Batch sizes vary from some liters to over 100 liters in semi-industrial mini batching plant.

[0072] Except when specified, the samples were cured in curing chambers (20 C. min 95% humidity) for 1, 7 and 28 days.

[0073] Strength measurements were done using compression tests on cubes for both mortars and concretes (444 cm for mortars and 161616 cm for concrete).

[0074] Flow is measured according to EN 12350-2.

[0075] Examples are provided for one cubic meter (1 m.sup.3) of corresponding fresh castable material when all ingredients are mixed.

[0076] In all examples the total binder content, the slag, fly ash, sand and aggregates content are provided in Kg content in one cubic meter (1 m.sup.3) of corresponding fresh castable material when all ingredients are mixed.

[0077] The total binder content represents the sum in weight of all puzzolanas (fly ash, slag, etc.) contained in one cubic meter (1 m.sup.3) of corresponding fresh castable material when all ingredients are mixed.

[0078] The ratio w/b eff represents the ratio in weight between the efficient water (or free water participating to the reaction) and the total binder content for one cubic meter (1 m.sup.3) of corresponding fresh castable material when all ingredients are mixed.

[0079] Activators and workability retention agent or admixtures are expressed in solid content (SC) weight.

[0080] Dosages are expressed in weight ratio (Kg/Kg) between solid content of an activator or workability retention agent or admixture and the total binder content.

TABLE-US-00003 TABLE 3 Chemical composition of several fly ashes samples by X-ray Analysis (fluorescence) MEL STO LA ALE AND SA 1 2 3 4 6 9 SiO.sub.2 (%) 53.42 51.38 49.14 36.49 58.64 57.39 Al.sub.2O.sub.3 (%) 33.65 25.30 26.55 19.41 23.06 22.00 Fe.sub.2O.sub.3 (%) 5.35 8.70 6.29 6.10 6.09 6.94 CaO (%) 1.25 4.38 5.84 23.53 1.90 2.64 MgO (%) 0.85 0.90 2.58 5.10 1.31 1.95 SO.sub.3 (%) 0.01 0.39 0.51 1.00 0.25 0.24 Na.sub.2O (%) 0.28 0.40 0.84 3.05 0.25 0.73 K.sub.2O (%) 0.97 2.43 3.02 0.46 1.74 1.92 TiO.sub.2 (%) 3.23 1.38 1.04 1.49 1.65 1.10 P.sub.2O.sub.5 (%) 0.04 0.23 0.41 0.73 0.43 0.34 Mn.sub.2O.sub.3 (%) 0.24 0.04 0.10 0.03 0.08 0.07 LOI 950 C (%) 0.52 2.89 2.90 0.99 2.50 4.92 Sum (%) 99.81 98.41 99.22 99.71 97.89 100.24 Glassy 86.11 87.5 81.95 89.28 72.25 79.98 Content (%)

TABLE-US-00004 TABLE 4 Chemical composition of ground granulated blast furnace slag samples X-ray Analysis (florescence) 1 2 3 4 5 6 7 8 SiO.sub.2 (%) 34.020 32.62 32.20 32.39 35.88 34.83 36.80 34.83 Al.sub.2O.sub.3 (%) 11.760 14.13 14.21 14.07 10.61 11.48 10.94 11.48 Fe.sub.2O.sub.3 (%) 0.880 1.11 0.58 0.47 0.57 0.37 0.40 0.37 CaO (%) 41.910 41.92 41.99 42.21 41.17 41.46 41.15 41.46 MgO (%) 5.750 6.19 6.52 6.49 7.74 6.98 8.62 6.98 SO.sub.35 (%) 2.780 2.76 1.84 1.96 1.52 2.39 2.20 2.39 Na.sub.2O (%) 0.050 0.20 0.16 0.21 0.00 0.34 0.22 0.34 K.sub.2O (%) 0.280 0.38 0.29 0.37 0.35 0.39 0.37 0.39 TiO.sub.2 (%) 1.070 0.52 0.49 0.49 0.55 1.64 0.56 1.64 P.sub.2O.sub.5 (%) 0.430 0.01 0.00 0.01 0.01 0.01 0.38 0.32 Mn.sub.2O.sub.3 (%) 0.010 0.31 0.29 0.36 0.42 0.32 0.01 0.01 LOI 950 C (%) 0 0.91 0.73 0.50 0.26 0.00 0.95 0.11 Sum (%) 98.94 99.24 99.32 98.55 99.10 100.21 100.67 100.21 Glassy 93 95 91 89 90 95 96 92 Content (%)

Example 1SF1 Reference Concrete Mix

[0081]

TABLE-US-00005 Material Unit Quantity Total binder content kg/m.sup.3 400 Fly ash reference (table 3) LA Fly ash content kg/m.sup.3 400 Slag reference (table 4) Slag content kg/m.sup.3 0 w/b eff 0.41 Slag/fly ash ration Kg/Kg Activator 1 dosage Molarity Mol 2.3 Activator 2 dosage Morality Mol 6 Total solid content (SC) activators % SC total binder in 19 1 and 2 weight content Workability retention agent dosage % SC total binder content Sand 0/4 round kg/m.sup.3 687 Fine aggregates gravel 4/8 round kg/m.sup.3 431 Coarse aggregates gravel 8/16 kg/m.sup.3 481 round Entrained air l/m.sup.3 20 Paste Volume l/m.sup.3 373 Results Unit Value Slump class SF1 Slump flow mm 620 Workability retention min 10 Strength at 2 days Mpa 4.5 Strength at 7 days Mpa 12.3 Strength at 28 days Mpa 21.5

Example 2SF1 Reference Concrete Mix with Workability Retention Agent

[0082]

TABLE-US-00006 Material Unit Quantity Total binder content kg/m.sup.3 400 Fly ash reference (table 3) LA Fly ash content kg/m.sup.3 400 Slag reference (table 4) Slag content kg/m.sup.3 0 w/b eff 0.41 Slag/fly ash ration Kg/Kg Activator 1 dosage Molarity Mol 2.3 Activator 2 dosage Morality Mol 6 Total solid content (SC) of activators % SC total binder in 19 1 and 2 weight content Workability retention agent dosage % SC total binder 1.2 content Sand 0/4 round kg/m.sup.3 687 Fine aggregates gravel 4/8 round kg/m.sup.3 431 Coarse aggregates gravel 8/16 kg/m.sup.3 481 round Entrained air l/m.sup.3 20 Paste Volume l/m.sup.3 373 Results Unit Value Slump class Slump flow mm 615 Workability retention min 45 Strength at 2 days Mpa 4.85 Strength at 7 days Mpa 11.9 Strength at 28 days Mpa 23.1

[0083] From examples 1 and 2 the effect of the workability retention agent is demonstrated by the workability retention increase from 10 minutes to 45 minutes. The 2 examples also show that the initial fresh properties and the final mechanical properties are not affected by the addition of the workability retention agent. Following examples 3-4 show different mix designs using various binder content and various binder compositions, using the workability retention agent to ensure workability retention of at least 45 minutes.

Example 3Concrete S4 Flow Class

[0084]

TABLE-US-00007 Material Unit Quantity Total binder content kg/m.sup.3 450 Fly ash reference (Table 3) MEL Fly ash content kg/m.sup.3 340 Slag reference (Table 4) GER Slag content kg/m.sup.3 110 w/b eff 0.38 Slag/fly ash ration Kg/Kg 0.32 Activator 1 dosage Molarity Mol 2 Activator 2 dosage Morality Mol 5 Total solid content (SC) of activators 1 % SC total binder in 16 and 2 weight content Workability retention agent dosage % SC total binder 0.6 content Sand 0/4 round kg/m.sup.3 679 Fine aggregates gravel 4/8 round kg/m.sup.3 426 Coarse aggregates gravel 8/16 round kg/m.sup.3 475 Entrained air l/m.sup.3 18 Paste Volume l/m.sup.3 386 Results Unit Value Slump class S4 Slump flow mm 220 Workability retention min 45 Strength at 1 days Mpa 2.05 Strength at 7 days Mpa 13.8 Strength at 28 days Mpa 23.9

Example 4Concrete SF2 Flow Class

[0085]

TABLE-US-00008 Material Unit Quantity Total binder content kg/m.sup.3 350 Fly ash reference (table 3) LA Fly ash content kg/m.sup.3 350 Slag reference (table 4) Slag content kg/m.sup.3 0 w/b eff 0.42 Slag/fly ash ration Kg/Kg Activator 1 dosage Molarity Mol 2.3 Activator 2 dosage Morality Mol 6 Total solid content (SC) of % SC total binder in 20 activators 1 and 2 weight content Workability retention agent dosage % SC total binder 1.2 content Sand 0/4 round kg/m.sup.3 726 Fine aggregates gravel 4/8 round kg/m.sup.3 456 Coarse aggregates gravel 8/16 kg/m.sup.3 508 round Entrained air l/m.sup.3 2.2% Paste Volume l/m.sup.3 338 Results Unit Value Slump class SF2 Slump flow mm 670 Workability retention min 60 Strength at 1 days Mpa 2.1 Strength at 7 days Mpa 4.5 Strength at 28 days Mpa 20.0

Example 5Concrete S1 Flow ClassSpecific Mix Design Elaborated for the Production of Concrete Pipes for Sewages

[0086] The concrete was produced on a central mixer using conventional techniques and procedures. The concrete was transported by belt conveyors to the different casting units. Different sizes RCP were produced by dry cast and by packer head methods.

TABLE-US-00009 Material Unit Quantity Total binder content kg/m.sup.3 400 Fly ash reference (table 3) STO Fly ash content kg/m.sup.3 400 Slag reference (table 4) Slag content kg/m.sup.3 0 w/b eff 0.32 Slag/fly ash ration Kg/Kg Activator 1 dosage Molarity Mol 1.8 Activator 2 dosage Morality Mol 4.7 Total solid content (SC) of activators 1 % SC total binder in 12 and 2 weight content Workability retention agent dosage % SC total binder 1.2 content Sand 0/4 crushed kg/m.sup.3 827 Fine aggregates gravel 4/8 crushed kg/m.sup.3 570 Coarse aggregates gravel 8/11 crushed kg/m.sup.3 329 Entrained air l/m.sup.3 20 Paste Volume l/m.sup.3 322 Results Unit Value Slump class S1 Slump flow mm <50 Workability retention min 60 Strength at 1 days* Mpa 14.57 Strength at 7 days Mpa 16.72 Strength at 28 days Mpa 23.22 *Samples were steam cured at 60 C. for 12 h before normal curing conditions

Example 6Concrete S1 Flow ClassSpecific Mix Design Elaborated for the Production of Concrete Pipes for Sewages

[0087] The concrete was produced on a central mixer using conventional techniques and procedures. The concrete was transported by belt conveyors to the different casting units. Different sizes RCP were produced by Hawk Eye equipment.

TABLE-US-00010 Material Unit Quantity Total binder content kg/m.sup.3 350 Fly ash reference (table 3) ALE Fly ash content kg/m.sup.3 350 Slag reference (table 4) Slag content kg/m.sup.3 0 w/b eff 0.33 Slag/fly ash ration Kg/Kg Activator 1 dosage Molarity Mol 1.5 Activator 2 dosage Morality Mol 3 Total solid content (SC) of activators 1 % SC total binder in 8 and 2 weight content Workability retention agent dosage % SC total binder 1.5 content Sand 0/4 crushed kg/m.sup.3 944 Fine aggregates gravel 4/8 crushed kg/m.sup.3 946 Coarse aggregates gravel 8/11 crushed kg/m.sup.3 Entrained air l/m.sup.3 20 Paste Volume l/m.sup.3 274 Results Unit Value Slump class S1 Slump flow mm <50 Workability retention min 120 Strength at 1 days* Mpa 12.7 Strength at 7 days Mpa 18.5 Strength at 28 days Mpa 24.9 *Samples were steam cured at 60 C. for 12 h before normal curing conditions

[0088] Alternatively, the castable material according to the invention may advantageously contain high strength fibers (steel or aramid or carbon or glass fiber or mineral fibers), organic or synthetic fibers.

[0089] Alternatively, the concrete mix of the invention may have a partial of full substitution of the sand and aggregates with lightweight sand and aggregates (expanded shale, expanded clay, expanded glass or pumice, natural puzzolans, etc.). This enables to obtain lightweight structural fiber reinforced concretes with densities below 1800 kg/m.sup.3, preferably below 1600 Kg/m.sup.3 or even more preferably below 1400 kg/m.sup.3, to reduce the weight of the structural element and to increase the thermal resistance (or reduce the thermal conductivity)

[0090] Finally, the castable material according to the invention may contain other type of admixtures like air entrainers to increase the amount of controlled air in the final hardened product, water reducers and plasticizers or superplasticizers, etc.

[0091] The invention provides many advantages that could not be achieved before: [0092] the invention enables using high dosages of fly ash in the binder (over 75% of fly ash in weight % to 100% fly ash), thus reducing the costs of raw materials and providing a solution that can be used in many location where good quality slag is not available. [0093] the invention enables to achieve workability retention of at least 45 minutes irrespective of the initial flow of the fresh castable material. [0094] the invention can be used for pipes manufacturing, more specifically for sewage pipes, using the excellent chemical, sulfates and acid resistance of alkali activated puzzolanas in comparison to normal cement based concrete [0095] the invention enables using the castable material for in situ job casting requiring various fresh placement properties (pavement, building, infrastructure, marine application, etc.) as well as for pre-cast industry.