Shotcrete composition

Abstract

A shotcrete composition comprising a) a cementitious binder; b) an ettringite formation controller comprising (i) a glyoxylic acid condensate and/or a glyoxylic acid adduct; and c) an alkali-free, aluminum-based shotcrete accelerator. The invention further relates to a process comprising providing a cementitious composition comprising a) a cementitious binder, and b) an ettringite formation controller comprising (i) a glyoxylic acid condensate and/or a glyoxylic acid adduct; admixing an alkali-free, aluminum-based shotcrete accelerator to the cementitious composition to obtain a shotcrete composition; and applying the shotcrete composition onto a surface to obtain a shotcrete structure and allowing the shotcrete structure to harden. The invention also relates to a hardened shotcrete structure obtained by this process.

Claims

1. A shotcrete composition comprising: a) a cementitious binder; b) an ettringite formation controller comprising (i) an amine-glyoxylic acid condensate; and c) an alkali-free, aluminum-based shotcrete accelerator selected from aluminum salts, aluminum complexes, aluminum hydroxides, and mixtures thereof; wherein the shotcrete composition has a strength as measured by a penetration resistance force at 6 minutes to 6 hours.

2. The composition according to claim 1, wherein the amine-glyoxylic acid condensate is at least one of a melamine-glyoxylic acid condensate, a urea-glyoxylic acid condensate, a melamine-urea-glyoxylic acid condensate, or a polyacrylamide-glyoxylic acid condensate.

3. The composition according to claim 1, wherein the ettringite formation controller additionally comprises (ii) a carbonate source.

4. The composition according to claim 3, wherein the carbonate source is selected from inorganic carbonates having an aqueous solubility of 0.1 gL.sup.1 or more, organic carbonates, and mixtures thereof.

5. The composition according to claim 4, wherein the inorganic carbonate is selected from the group consisting of sodium carbonate, lithium carbonate and magnesium carbonate; and the organic carbonate is selected from the group consisting of ethylene carbonate and propylene carbonate.

6. The composition according to claim 1, wherein the ettringite formation controller additionally comprises (iii) a component selected from polycarboxylic acids or salts thereof whose milliequivalent number of carboxyl groups is 5.00 meq/g or higher; and -hydroxy carboxylic acids or salts thereof.

7. The composition according to claim 6, wherein the polycarboxylic acid is selected from phosphonoalkyl carboxylic acids, amino carboxylic acids, and polymeric carboxylic acids.

8. The composition according to claim 6, wherein the component is selected from: polycarboxylic acids or salts thereof whose milliequivalent number of carboxyl groups is 5.00 to 15.00 meq/g; and -hydroxy carboxylic acids or salts thereof.

9. The composition according to claim 1, wherein the cementitious binder is selected from Portland cement, calcium aluminate cement, sulfoaluminate cement, or combinations thereof.

10. The composition according to claim 1, wherein the composition additionally comprises a latent hydraulic binder or a pozzolanic binder, or mixtures thereof.

11. The composition according to claim 1, additionally comprising a dispersant.

12. The composition according to claim 11, wherein the dispersant is selected from the group of comb polymers having a carbon-containing backbone to which are attached pendant cement-anchoring groups and polyether side chains, non-ionic comb polymers having a carbon-containing backbone to which are attached pendant hydrolysable groups and polyether side chains, the hydrolysable groups upon hydrolysis releasing cement-anchoring groups, sulfonated melamine-formaldehyde condensates, lignosulfonates, sulfonated ketone-formaldehyde condensates, sulfonated naphthalene-formaldehyde condensates, phosphonate containing dispersants, phosphate containing dispersants, and mixtures thereof.

13. The composition according to claim 1, wherein the composition exhibits superior early strength, as compared to the composition without b) ettringite formation controller comprising (i) an amine-glyoxylic acid condensate.

14. A process comprising: providing a cementitious composition comprising a) a cementitious binder, and b) an ettringite formation controller comprising (i) an amine-glyoxylic acid condensate; admixing an alkali-free, aluminum-based shotcrete accelerator selected from aluminum salts, aluminum complexes, aluminum hydroxides, and mixtures thereof to the cementitious composition to obtain a shotcrete composition; and applying the shotcrete composition onto a surface to obtain a shotcrete structure and allowing the shotcrete structure to harden.

15. A hardened shotcrete structure obtained by the process according to claim 14.

Description

(1) The invention will be described in more detail by the accompanying drawings and the subsequent examples.

(2) FIGS. 1a and 1b show the experimental results of mini-slump tests of concrete mixes.

(3) FIGS. 2a and 2b show the experimental results of tests for determining the compressive strength of concrete mixes.

(4) FIGS. 3a and 3b show the experimental results of tests for determining the compressive strength of further concrete mixes.

(5) FIGS. 4a and 4b show the experimental results of tests for determining the penetration resistance force of mortar mixes.

(6) FIGS. 5a and 5b show the experimental results of tests for determining the penetration resistance force of further mortar mixes.

EXAMPLES

A.) Materials

(7) Two typical shotcrete cement types from Germany and Austria were used: Mergelstetten CEM I 52,5R and a mixed cement 2:1(w/w) Eiberg CEM 152,5N:Fluasit (the latter is a mix of limestone, slag & fly ash). Both cement types comprise Portland cement clinker and a sulfate source.

(8) As plasticizers MasterGlenium SKY 594 (further abbreviated as MG SKY 594 or SKY 594) and Melflux 6680L (further abbreviated as MF), both available from BASF Construction Solutions GmbH, were used. Both MasterGlenium SKY 594 and Melflux 6680L are polycarboxylate ether (PCE) based plasticizers.

(9) In the reference mixes, hydration control additive MasterRoc HCA 10 (further abbreviated as MR HCA 10 or HCA 10), available from BASF Construction Solutions GmbH, was used. MasterRoc HCA 10 is an aqueous solution of organic acids comprising phosphonic acid and citric acid.

(10) As sprayed concrete accelerators MasterRoc SA 160 and SA 167, both available from BASF Construction Solutions GmbH, were used. Both MasterRoc SA 160 and SA 167 are aqueous suspension type alkali-free accelerators based on aluminum sulfate with solid content in the range of 504% and 605% correspondingly. As reference accelerators, sodium aluminate as an aqueous solution with a solid content of 40%, and sodium silicate as an aqueous solution with a solid content of 41.5%, both of which are alkali containing accelerators, were included in the experiments.

(11) A glyoxylic acid urea condensate was synthesized as follows: Glyoxylic acid (1.2 g of glyoxylic acid, 50 wt.-% solution in water) was charged into a reaction vessel and aqueous potassium hydroxide (40 wt.-%) was added until a pH value of 5 was reached. 1 g of urea was added and the mixture was heated to 80 C. After 7 h, the highly viscous substance was analyzed by gel permeation chromatography method (GPC) as described below. The thus obtained glyoxylic acid urea condensate is an aqueous solution with a solids content of 49.3%.

(12) An ettringite formation controller was prepared according to the following method:

(13) BMF: The glyoxylic acid urea condensate was mixed with sodium gluconate and sodium carbonate in the weight proportion of solids/actives 3:1:3.

B.) Analytical Methods

(14) Gel Permeation Chromatography (GPC)

(15) Column combination: OH-Pak SB-G, OH-Pak SB 804 HQ and OH-Pak SB 802.5 HQ by Shodex, Japan; eluent: 80 vol.-% aqueous solution of HCO.sub.2NH.sub.4 (0.05 mol/l) and 20 vol.-% acetonitrile; injection volume 100 l; flow rate 0.5 ml/min. The molecular weight calibration was performed with poly(acrylate) standards for the RI detector, purchased from PSS Polymer Standards Service, Germany.

C.) Application Tests

(16) C.1) Concrete Tests

(17) Concrete mixes were prepared on the basis of the compositions according to the following table.

(18) TABLE-US-00001 Base Composition Component B1 B2 Cement (2:1(w/w) Eiberg CEMI 52,5N:Fluasit) 680 g Cement (Mergelstetten CEMI 52,5R) 670 g Norm sand (DIN EN196-1) 1350 g 1350 g Grit (2-5 mm), washed, 900 g 900 g limestone-based, DIN EN 12620:2002 Water (total amount) 293.9 g.sup. 288.1 g.sup.

(19) 8 concrete mixes were prepared, comprising a base composition as well as the components according to the following table.

(20) TABLE-US-00002 Concrete Mix C1 C2 C3 C4 * C5 C6 C7 C8 * Base Composition B1 B1 B1 B1 B2 B2 B2 B2 Further Components [wt.-%] Plasticizer (MG SKY 594) ** 0.4 0.3 Plasticizer (Melflux 6680L) ** 0.025 0.005 0.02 0.06 0.005 0.04 Hydration control additive 0.2 (MasterRoc HCA 10) *** Ettringite formation controller 1.05 1.75 0.7 0.7 1.75 1.05 (BMF) ** * comparative example ** wt.-% of the sum of solids of active components relative to the weight of cement (bwoc) *** wt.-% of aqueous solution relative to the weight of cement (bwoc)

(21) Concrete mixes C1 to C8 were prepared by mixing all components and slump retention was evaluated.

(22) Concrete Mixing Procedure:

(23) The concrete mixing was performed in a Hobart mixer with double mixing action (shaft and planetary) using a bowl with a capacity of 4.7 liters. Sand, grit and cement were placed into the bowl and mixed in the dry state at speed 1. Subsequently, 80% of the water were added and the resulting mixture was mixed at speed 1 for further 2 min. Thereafter, an aqueous solution of the plasticizer and, if applicable, MasterRoc HCA 10, in the remaining 20% of the water were added and the mixture was mixed again for 2 min at speed 1.

(24) For the mixtures with ettringite formation controller BMF, a modified mixing procedure was used, wherein plasticizer and ettringite formation controller both are dissolved in 100% of the mixing water for the concrete mix and added at once after initial premixing of dry components. The further mixing procedure is the same as in the above-mentioned case.

(25) When the mixture is further used for slump retention assessment, the concrete mix is transferred to a mini-slump cone (see the description of the mini-slump test below) after a total of 5 min of mixing.

(26) When the mixture is further mixed with an accelerator, the speed of mixing is switched to speed 2 after a total of 5 min and the accelerator is injected into the mixture via syringe as fast as possible. After 15 seconds of mixing with the accelerator, the mixtures are filled into 4416 cm prism molds, densified at a vibrating table for 30 seconds, sealed with plastic foil and stored at 20 C., 65% relative humidity, for further strength measurements.

(27) Mini-Slump Test:

(28) The mini-slump test is a modified concrete slump test for small volumes of concrete, which allows the precise prediction of the results of standardized concrete slump test DIN EN 12350-2. For the mini-slump test, a modified mini-slump cone is used, which represents a half of a standard Abrams cone (truncated cone with dimensions 50, 100 and 150 mm of upper inner diameter, lower inner diameter and height). This cone is placed on a flat plate, filled with fresh concrete mix in two stages of approximately equal volume and each layer is tamped 15 times. Subsequently, the upper concrete surface is levelled, and then the cone is removed and the slump (the difference between the height of the cone and the height of the resulting concrete heap) is recorded.

(29) This test is repeated as frequently as needed (in this case every 15 to 30 min) to assess the slump retention of the mixes. For each repeated slump test the concrete mix is premixed with a Hobart mixer for 1 min at speed 1.

(30) FIG. 1a shows the mini-slump test results of concrete mixes C1 to C4. FIG. 1b shows the mini-slump test results of concrete mixes C5 to C8. The dosage of ettringite controller was varied in both cement types to investigate its effect on slump retention, as well as strength development in the presence of accelerators. The initial slump of the mixes was adjusted to the same initial value by adjusting the dosage of plasticizers, so as to allow for comparability of the mixes.

(31) It is evident that the concrete mixes comprising ettringite formation controllers of the invention show a sufficiently long open time, which can be adjusted to the desired value by dosage variation of ettringite controller.

(32) Furthermore, it was found that visually, the concrete mixes comprising ettringite formation controllers of the invention, both with and without accelerator, are initially less viscous than the comparative concrete mixes without ettringite formation controllers, indicating a higher degree of pumpability and sprayability.

(33) Accelerators were added to concrete mixes as prepared above (accelerated concrete mixes) according to the following tables.

(34) TABLE-US-00003 Accelerated Concrete Mix C1-A1 C1-A2 C4-A1 ** C4-A2 ** C1-A3 C1-A4 C4-A3 ** C4-A4 ** Components of Concrete Mix C1 C1 C4 C4 C1 C1 C4 C4 Further Components [wt.-%] * Accelerator 6 8 6 8 (SA 160) Accelerator 5 7 5 7 (SA 167) Accelerated Concrete Mix C5-A1 C7-A1 C8-A1 ** C8-A2 ** C5-A2 C7-A2 C7-A3 C8-A3 ** C8-A4 ** Components of Concrete Mix C5 C7 C8 C8 C5 C7 C7 C8 C8 Further Components [wt.-%] * Accelerator 6 8 6 8 (SA 160) Accelerator 5 5 7 5 7 (SA 167) * wt.-% of aqueous solution relative to the weight of cement (bwoc) ** comparative example

(35) The compressive strength of the prepared prisms comprising accelerated concrete mixes was measured after 4, 6 and 24 h according to the norm DIN EN 206-1/DIN 1045-2. By using a ZWICK 1446 machine, each prism was broken into two equal pieces. Thus, two values could be obtained for each prism.

(36) The results are shown in FIGS. 2a, 2b, 3a and 3b. It is evident that the concrete mixes comprising ettringite formation controller of the invention show significantly higher early strength than the corresponding comparative concrete mixes, which is particularly relevant for earlier re-entry time in mines and tunnels, and under difficult working conditions like unstable ground, where fast rates of advance are required, or if thick layers have to be sprayed overhead.

(37) C.2)Mortar Tests

(38) Mortar mixes M1 to M12 with compositions according to the following tables were prepared.

(39) TABLE-US-00004 Mortar Mix Component M1 M2 M3 * M4 * M5 M6 * Cement [g] 836 836 836 836 (2:1(w/w) Eiberg CEMI 52,5N:Fluasit) Cement [g] 836 836 (Mergelstetten CEMI 52,5R) Norm sand [g] 1350 1350 1350 1350 1350 1350 (DIN EN196-1) Plasticizer [wt.-%]** 0.4 0.4 0.3 (MG SKY 594) Plasticizer [wt.-%]** 0.025 0.025 0.04 (Melflux 6680 L) Accelerator [wt.-%]*** 8 8 (SA 160) Accelerator [wt.-%]*** 7 7 7 7 (SA 167) Hydration control additive [wt.-%]*** 0.2 0.2 (MasterRoc HCA 10) Ettringite formation controller [wt.-%]** 1.05 1.05 1.05 (BMF) Water [g] 376.2 376.2 376.2 376.2 376.2 376.2 (total amount) * comparative example **wt.-% of the sum of solids of active components relative to the weight of cement (bwoc) ***wt.-% of aqueous solution relative to the weight of cement (bwoc)

(40) TABLE-US-00005 Mortar Mix Component M7 M8 * M9 * M10 M11 * M12 * Cement [g] 836 836 836 (2:1(w/w) Eiberg CEMI 52,5N:Fluasit) Cement [g] 836 836 836 (Mergelstetten CEMI 52,5R) Norm sand [g] 1350 1350 1350 1350 1350 1350 (DIN EN196-1) Plasticizer [wt.-%]** 0.025 0.025 0.025 0.04 0.04 0.04 (Melflux 6680 L) Accelerator [wt.-%]*** 7 7 (SA 167) Accelerator [wt.-%]*** 7 7 (sodium aluminate) Accelerator [wt.-%]*** 7 7 (sodium silicate) Ettringite formation controller [wt.-%]** 1.05 1.05 1.05 1.05 1.05 1.05 (BMF) Water [g] 372.6 372.6 372.6 372.6 372.6 372.6 (total amount) * comparative example **wt.-% of the sum of solids of active components relative to the weight of cement (bwoc) ***wt.-% of aqueous solution relative to the weight of cement (bwoc)

(41) Mortar mixes M1 to M6 were obtained similarly to the concrete mixes described above, however the difference in the composition is that these mortar mixes do not comprise aggregates in the range of 2 to 5 mm, so as to enable the measurement of penetration resistance force using an electronic sprayed concrete penetrometer (Mecmesin AFG 500N) equipped with a 1.6 mm needle.

(42) Mixing and Measurement Procedure:

(43) All the components except the accelerator were mixed for 3.5 min, having the same initial consistency and being prepared in equally big buckets. Afterwards, the accelerators were added and the mixes were further mixed for 40 seconds, and the obtained accelerated mortar mixes were compacted in the buckets to create a smooth flat surface. The penetration resistance force of a needle (diameter of 1.6 mm) into the mortar mixes from the upper smoothened surface was measured over a period of 6 min to 6 h (10 measurements for each point of time to calculate an average), starting from the addition of the accelerators using the above-mentioned penetrometer (Mecmesin AFG 500N). The results of the penetration resistance force measurements directly correlate with the strength of the mortar mixes and can be used as a prediction for corresponding big scale concrete tests. The measurement results are shown in FIGS. 4a, 4b, 5a and 5b.

(44) FIG. 4a shows the results for mortar mixes M1 to M4 comprising the 2:1(w/w) Eiberg CEMI 52,5N:Fluasit cement. The comparison of M1 to M3 shows that in the presence of alkali-free accelerator SA 167, the mortar mixes comprising ettringite formation controller of the invention shows significantly higher early (6 min to 6 h) strength than the mortar mixes comprising reference hydration control additive HCA 10. The comparison of M2 to M4 shows that this effect is also observed in the presence of alkali-free accelerator SA 160.

(45) FIG. 4b shows the results for mortar mixes M5 and M6 comprising Mergelstetten CEMI 52,5R cement. It is again evident that in the presence of alkali-free accelerator SA 167, the mortar mix comprising ettringite formation controller of the invention shows significantly higher early (6 min to 6 h) strength than the mortar mix comprising no ettringite formation controller.

(46) FIG. 5a shows the results for mortar mixes M7 to M9 comprising the 2:1(w/w) Eiberg CEMI 52,5N:Fluasit cement and ettringite formation controller BMF. It is evident that in the presence of alkali-free accelerator SA 167, the mortar mix shows significantly higher early (6 min to 6 h) strength than in the presence of alkali containing accelerators sodium aluminate and sodium silicate, respectively.

(47) FIG. 5b shows the results for mortar mixes M10 to M12 comprising Mergelstetten CEMI 52,5R cement and ettringite formation controller BMF. It is again evident that in the presence of alkali-free accelerator SA 167, the mortar mix shows significantly higher early (6 min to 6 h) strength than in the presence of alkali containing accelerators sodium aluminate and sodium silicate, respectively.