Construction castable material with controllable flow or slump

Abstract

Construction castable material with controllable flow or slump comprising (a) a binder comprising 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, representing from 10% to 60% of the binder weight and ground granulated blast furnace slag comprising from 40% to 70% by weight of CaO and from 30 to 60% by weight of SiO2, representing from 40% to 90% of the binder weight, (b) an activator comprising alkaline reagents selected from the group composed by water glass, preferably in solution with 30 to 50% by weight solid content, sodium metasilicates and sodium hydroxide, (c) sand, fine and coarse aggregates and (d) organic acids or conjugated salts of organic acids in a dosage from 0.001% to 3% by weight with respect to the binder.

Claims

1. A construction castable material with controllable flow or slump comprising (a) a binder comprising 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, representing from 10% to 60% of the binder weight, and ground granulated blast furnace slag comprising from 40% to 70% by weight of CaO and from 30 to 60% by weight of SiO2, representing from 40% to 90% of the binder weight; (b) an activator mix comprising alkaline reagents composed by water glass, sodium metasilicates and sodium hydroxide, wherein a solid active content of sodium metasilicates and sodium hydroxide in the activator mix is in the range of 2.5:1 and 0.5:1, respectively; (c) sand, fine and coarse aggregates, water; and (d) organic acids or conjugated salts of organic acids in a dosage from 0.001% to 3% by weight with respect to the binder, the organic acid is tartaric acid, aldaric acid, or maleic acid; wherein a ratio between a solid active content of said activator mix to the total binder content is between 4.5 weight % and 8 weight %; and wherein the construction castable material with controllable flow provides a consistency of concrete slump of class between S3 and S5 and/or consistency of concrete flow of class between F4 and F6, and a workability retention time of from 30 minutes to 150 minutes.

2. The construction castable material according to claim 1, wherein the binder in (a) comprises pozzolanas.

3. The construction castable material according to claim 1, wherein said sodium metasilicates are pentahydrate sodium metasilicates.

4. The construction castable material according to claim 1, wherein (d) further comprises Polycarboxylate Ether Polymers (PCE).

5. The construction castable material according to claim 4, wherein the concentration range of said Polycarboxylate Ether Polymers is from 0.12% to 0.75% by weight of binder.

6. The construction castable material according to claim 1, wherein in (b) the alkaline reagents composed by water glass is in a solution with 30 to 50% by weight solid content.

7. The construction castable material according to claim 1, wherein the binder in (a) further comprises natural fibers, metallic fibers or polymeric fibers.

8. The construction castable material according to claim 1, wherein the binder in (a) further comprises alkali content, silica fumes, fillers or limestone.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 plots tartaric acid effect on initial workability for a slag concrete.

(2) FIG. 2 plots compressive strength development after 2 days (white bars) and 28 days (black bar) for slag concrete containing 0% to 1.5% tartaric acid to modify initial workability.

(3) FIG. 3 plots yield stress for a geopolymer concrete containing 250 kg/m3 binder and different tartaric acid dosages (from 0 to 3% with respect to binder).

(4) FIG. 4 plots yield stress vs. viscosity for a 250 kg/m3 binder geopolymer concrete. The higher the dosage of tartaric acid the lower the viscosity and the yield stress.

(5) FIG. 5 plots initial yield stress vs. slump for a 450 kg/m3 binder geopolymer concrete. The higher the tartaric acid dosage, the lower the yield stresses.

(6) FIG. 6 plots yield stress vs. viscosity in a 450 kg/m3 binder geopolymer concrete.

(7) FIG. 7 plots workability retention (open time) of geopolymer concrete mixes containing 0% to 1.5% tartaric acid with respect to binder.

(8) FIG. 8 is a picture of a mix design showing strong segregation between paste and aggregates when the water binder ratio is too high or when the dosage of the aldaric acids is too high.

EXAMPLES OF THE INVENTION

Example 1. Concrete Admixture. Chemical Composition

(9) A concrete mix composition used in the examples is shown below.

(10) TABLE-US-00003 TABLE 3 Weight (Kg/m3) Ground Granulated Blast Furnace Slag 315 Fly ashes 135 Mixing water 191.1 Activator 1 22.5 Activator 2 45 Tartaric Acid 2.3 Aggregates 0-4 666.5 Aggregates 4-8 320.1 Aggregates 8-16 614.5 Water/binder ratio 0.72

(11) Fly ash, blast furnace slag and natural pozzolanas compositions used in the examples are given in Tables 3, 4 and 5 respectively.

(12) TABLE-US-00004 TABLE 4 Chemical composition of several fly ashes samples by X-ray diffraction 1 2 3 4 5 6 7 8 SiO.sub.2 (%) 60.83 58.64 57.41 34.17 49.61 41.86 53.42 57.39 Al.sub.2O.sub.3 (%) 20.85 23.06 18.48 12.85 24.34 26.22 33.65 22.00 Fe.sub.2O.sub.3 (%) 5.05 6.09 8.06 2.02 14.72 18.90 5.35 6.94 CaO (%) 2.19 1.90 3.78 34.03 3.70 7.94 1.25 2.64 MgO (%) 1.56 1.31 1.89 5.47 1.62 1.36 0.85 1.95 SO.sub.35 (%) 0.36 0.25 0.35 1.74 0.39 0.82 0.01 0.24 Na.sub.2O (%) 0.35 0.25 1.03 0.11 0.47 0.18 0.28 0.73 K.sub.2O (%) 1.53 1.74 2.07 1.19 1.18 1.25 0.97 1.92 TiO.sub.2 (%) 1.01 1.65 0.83 0.62 1.76 0.94 3.23 1.10 P.sub.2O.sub.5 (%) 0.24 0.43 0.17 0.05 0.20 0.40 0.04 0.34 Mn.sub.2O.sub.3 0.05 0.08 0.09 0.84 0.10 0.06 0.24 0.07 (%) LOI 950 4.18 2.50 4.17 5.38 1.16 0.70 0.52 4.92 C. (%) Sum (%) 98.21 97.89 98.33 98.47 99.27 100.64 99.81 100.24

(13) TABLE-US-00005 TABLE 5 Chemical composition of ground granulated blast furnace slag samples by X-ray diffraction 1 2 3 4 5 6 7 8 SiO.sub.2 (%) 33.98 32.62 32.20 32.39 35.88 34.83 36.80 34.83 Al.sub.2O.sub.3 (%) 14.70 14.13 14.21 14.07 10.61 11.48 10.94 11.48 Fe.sub.2O.sub.3 (%) 1.46 1.11 0.58 0.47 0.57 0.37 0.40 0.37 CaO (%) 42.08 41.92 41.99 42.21 41.17 41.46 41.15 41.46 MgO (%) 3.97 6.19 6.52 6.49 7.74 6.98 8.62 6.98 SO.sub.35 (%) 1.63 2.76 1.84 1.96 1.52 2.39 2.20 2.39 Na.sub.2O (%) 0.18 0.20 0.16 0.21 0.00 0.34 0.22 0.34 K.sub.2O (%) 0.31 0.38 0.29 0.37 0.35 0.39 0.37 0.39 TiO.sub.2 (%) 0.58 0.52 0.49 0.49 0.55 1.64 0.56 1.64 P.sub.2O.sub.5 (%) 0.02 0.01 0.00 0.01 0.01 0.01 0.38 0.32 Mn.sub.2O.sub.3 0.34 0.31 0.29 0.36 0.42 0.32 0.01 0.01 (%) LOI 950 0.87 0.91 0.73 0.50 0.26 0.00 0.95 C. (%) Sum (%) 98.37 99.24 99.32 98.55 99.10 100.21 100.67 100.21

(14) TABLE-US-00006 TABLE 6 Chemical composition of natural pozzolanas obtained by X-ray diffraction 1 2 3 SiO.sub.2 (%) 70.23 63.86 56.25 Al.sub.2O.sub.3 (%) 15.52 16.17 18.72 Fe.sub.2O.sub.3 (%) 2.21 3.66 6.88 CaO (%) 2.08 2.59 4.55 MgO (%) 0.37 0.52 1.66 SO.sub.35 (%) 0.00 0.00 0.02 Na.sub.2O (%) 2.62 1.83 2.12 K.sub.2O (%) 3.53 3.01 2.15 TiO.sub.2 (%) 0.28 0.43 1.02 P.sub.2O.sub.5 (%) 0.01 0.04 0.28 Mn.sub.2O.sub.3 (%) 0.11 0.26 0.15

Example 2. Dosage of Tartaric Acid in the Admixture. Effect of Tartaric Acid on Slump, Strength, Rheological Results and Placing Characteristics

(15) The influence of tartaric acid as workability modifier has been evaluated, using slag concrete having a binder to aggregates ratio of 0.28. water to binder ratio of 0.5 and an activator to binder ratio of 0.2.

(16) The slump (in cm) was measured in order to compare different dosages of tartaric acid. FIG. 1 shows the comparative chart for additions from 0 to 1.5% tartaric acid to illustrate the effect on the slag based concrete workability after mixing.

(17) Compressive strength tests showed that even though early age strength is less than the reference, the final strength, after 28 days, is improved. FIG. 2 is an example of such effect on the mechanical properties of activated concretes when using tartaric acid.

(18) As can be seen on FIG. 1 the concrete not having tartaric acid had lower slump cone test value (class S4). The slump increased from 9 cm to 26 cm without modifying water content or activator dosage. As already mentioned, there was also an effect on strength development while having a 28 days compressive strength of 31.15 MPa other mixes containing tartaric acid have developed more than 44.6 MPa and up to 76.4 MPa.

(19) Rheological properties have been determined for geopolymer concretes containing 300 kg/m3 (FIG. 3) and 450 kg/m3 binder (FIG. 5). Results are shown in FIGS. 3 and 5. Higher binder content has also been tested and is considered in this invention, typically up to 600 kg/m3.

(20) According to these results it is possible to determine how the yield stress (Pa), minimum stress to be exceeded for a structured fluid to flow, decreases as the slump increases. This means that by having a higher dosage of tartaric acid the slump of the concrete increases and the yield stress decreases.

(21) FIGS. 4 and 6 plots the yield stress previously referred in function of the viscosity. It can be seen that at 0% tartaric acid the stress/viscosity value is the highest while the 3% tartaric acid with respect to binder content has reduced this value towards lower viscosity and lower yield stress in both cases, with different binder content.

(22) It has been observed that by using tartaric acid in the geopolymer concrete mix design it is possible to maintain fresh workability during longer open time. Somehow the characteristic rapid setting of geopolymer concrete is altered by the use of the tartaric acid giving as a result the workability retention of concrete ready mixes up to 120 min, as can be shown in Table 7.

(23) TABLE-US-00007 TABLE 7 Ref Ref-1 MX01 MX01-1 Coarse Aggregate 1 Kg/m.sup.3 480 480 480 480 Coarse Aggregate 2 Kg/m.sup.3 360 360 360 360 Fine Aggregates Kg/m.sup.3 770 770 770 770 Slag Kg/m.sup.3 315 315 315 315 Fly Ash Kg/m.sup.3 135 135 135 135 Water/Binder Kg/m.sup.3 0.45 0.45 0.45 0.45 Activator 1 Kg/m.sup.3 45 45 45 45 Activator 2 Kg/m.sup.3 22.5 22.5 22.5 22.5 PCE Kg/m.sup.3 0 3 0 0.5 Tartaric Acid Kg/m.sup.3 0 0 1 1 Slump (cm) 8 11 23 26 Setting time (min) 30 30 120 120

(24) A higher plasticizing effect is achieved when tartaric acid is combined with PCE. If no tartaric acid is added to the mixture, a higher amount of PCE is required, and low performance is obtained.

(25) It was observed from the various tests that dosages of admixtures larger than the one described (3% of organic acid and 0.75 ASC % of PCE with respect to binder) will lead to a very unstable mix design (segregation, bleeding) and will dramatically affect the setting time and strength development of the construction material as can be seen in the FIG. 7.

(26) Strong segregation between paste and aggregates occurs when the water binder ratio and/or the dosage of the aldaric acids is too high (see FIG. 7).