Composition for Activating Super Sulfated Cement

Abstract

The invention relates to a composition for activating a super sulfated cement (SSC), the composition comprising calcium sulfoaluminate (CSA) and/or calcium aluminate (CA) or a composition of both and calcium hydroxide (CH) wherein the composition comprises 65 wt. % to 85 wt. % CSA and/or CA and 15 wt. % to 35 wt. % CH and to a super sulfated cement comprising blast furnace slag, a calcium sulfate component and the composition for activating the super sulfated cement and concrete made from the super sulfated cement and predetermined aggregates.

Claims

1-14. (canceled)

15: A composition for activating a super sulfated cement, the composition comprising: (a) 65 wt. % to 85 wt. % of at least one of calcium sulfoaluminate and calcium aluminate, and (b) 15 wt. % to 35 wt. % calcium hydroxide.

16: The composition of claim 15, wherein the composition comprises: (a) 70 wt. % to 80 wt. % of the at least one of calcium sulfoaluminate and calcium aluminate and (b) 20 wt. % to 30 wt. % calcium hydroxide

17: The composition of claim 15, wherein calcium aluminate is partially substituted by calcium sulfate.

18: The composition of claim 15, wherein both calcium sulfoaluminate and calcium aluminate are present, the composition comprising: (a) from 5 wt. % to 95 wt. % of calcium sulfoaluminate, and (b) from 95 wt. % to 5 wt. % of calcium aluminate, in each case, based on the total amount of calcium sulfoaluminate and calcium aluminate in the composition.

19: The composition of claim 17, wherein both calcium sulfoaluminate and calcium aluminate are present, the composition comprising: (a) from 5 wt. % to 95 wt. % of calcium sulfoaluminate, and (b) from 95 wt. % to 5 wt. % of calcium aluminate, in each case, based on the total amount of calcium sulfoaluminate and calcium aluminate in the composition.

20: The composition of claim 15, wherein (a) calcium sulfoaluminate is present as calcium-sulfoaluminate-cement, and/or (b) calcium aluminate is present as calcium-aluminate-cement, and/or (c) calcium hydroxide is present as slaked lime.

21: The composition of claim 16, wherein (a) calcium sulfoaluminate is present as calcium-sulfoaluminate-cement, and/or (b) calcium aluminate is present as calcium-aluminate-cement, and/or (c) calcium hydroxide is present as slaked lime.

22: The composition of claim 17, wherein (a) calcium sulfoaluminate is present as calcium-sulfoaluminate-cement, and/or (b) calcium aluminate is present as calcium-aluminate-cement, and/or (c) calcium hydroxide is present as slaked lime.

23: The composition of claim 18, wherein (a) calcium sulfoaluminate is present as calcium-sulfoaluminate-cement, and/or (b) calcium aluminate is present as calcium-aluminate-cement, and/or (c) calcium hydroxide is present as slaked lime.

24: A super sulfated cement comprising: 1 wt. % to 5 wt. %. of the composition of claim 15, 6 wt. % to 20 wt. % of the calcium sulfate component and remainder blast furnace slag.

25: A super sulfated cement comprising: 1 wt. % to 5 wt. %. of the composition of claim 16, 6 wt. % to 20 wt. % of the calcium sulfate component and remainder blast furnace slag.

26: A super sulfated cement comprising: 1 wt. % to 5 wt. %. of the composition of claim 17, 6 wt. % to 20 wt. % of the calcium sulfate component and remainder blast furnace slag.

27: A super sulfated cement comprising: 1 wt. % to 5 wt. %. of the composition of claim 18, 6 wt. % to 20 wt. % of the calcium sulfate component and remainder blast furnace slag.

28: A super sulfated cement comprising: 1 wt. % to 5 wt. %. of the composition of claim 19, 6 wt. % to 20 wt. % of the calcium sulfate component and remainder blast furnace slag.

29: The super sulfated cement of claim 24, wherein blast furnace slag is present in an amount of at least 79 wt. %.

30: The super sulfated cement of claim 24, wherein the calcium sulfate component is at least one selected from the group consisting of calcium sulfate dihydrate, calcium sulfate hemihydrate, and anhydrous calcium sulfate.

31: The super sulfated cement of claim 24, wherein the super sulfated slag cement further comprises a setting retardant.

32: A concrete comprising aggregates and the super sulfated cement of claim 15.

33: A concrete comprising aggregates and the super sulfated cement of claim 18.

34: An object selected from the group consisting of (i) precast concrete parts, (ii) buildings, (iii) objects made with civil engineering, (iv) tunnels, and (v) submarine applications, where the object comprises the concrete of claim 32.

Description

[0062] The invention is explained by means of different embodiments and accompanying drawings showing:

[0063] FIG. 1: a table showing different inventive mixtures of a first slag with hemihydrate and an activator composition according to the invention in relation to a common blast furnace cement CEM III, and the respective compression strength after one, seven and 28 days;

[0064] FIG. 2: a table showing a first slag with hemihydrate and activated with CH and CAC or CSA according to the invention, in relation to a known mixture with CEM III and anhydrite;

[0065] FIG. 3: a table showing the impact of the nature of calcium sulfate on inventive mixtures;

[0066] FIG. 4: a table showing the impact of the slag.

[0067] According to the invention, instead of activating super sulfated cement with Portland cement or alkaline activation, the super sulfated cement is activated by CSA or CA or a composition of both and CH.

[0068] Together with these activating constituents, calcium sulfate as anhydrite, hemihydrate or gypsum may be present. The slag in the super sulfated cement is therefore activated by the composition of the calcium sulfate carrier as well as by the activating composition of CSA and/or CA and CH.

[0069] In table 1, in the first column from the left, a super sulfated cement which is activated by a composition of hemihydrate and CEM III/B is shown as a reference. In relation hereto, a composition with CSA without any calcium hydroxide is shown. Further, a composition of CSA and CH in different amounts is mentioned as well as a composition comprising only CA and a composition with CA and CH.

[0070] Super sulfated cement activated according to the state of the art with a CEM III/B cement appears to have a short term compressive strength after day one of 3 MPa, wherein the long term compressive strength after 28 days is 43.4 MPa.

[0071] In comparison, a composition in which the CEM III is substituted by CSA leads to a short term compressive strength of 0.7 MPa but to a long term compressive strength which is significantly higher than the one of a composition activated by CEM III. The compressive strength after seven days is significantly improved over the compressive strength of the reference example.

[0072] Super sulphated slag cement activation with CA substituting CEM III of the prior art exhibits a short term compressive strength after one day similar to the one with CSA (i.e. remarkably low) and almost the same after seven days and 28 days.

[0073] An inventive activation of columns 3, 4, 6 and 7 of table 1 shows that by substituting the CEM III/B by a composition of 0.75% CSA and 0.25% CH leads to compressive strengths at any stage which are higher than the compressive strength of the reference. The compressive strength can be even higher when the CSA content and the CH content are doubled to 2% in total.

[0074] The composition with CA and CH behaves in a comparable manner so that the strength values of a composition with 0.75% CA and 0.25% CH come close to the determined compressive strengths of the CSA/CH composition with 0.75% and 0.25%. The same appears to be true for a composition in which the said constituents are doubled to 1.5% and 0.5%.

[0075] In comparison to the sole addition of CAS or the sole addition of CA, it is obvious that a composition comprising of CSA and CH or CA and CH shows a massive synergistic effect between these respective two constituents.

[0076] In these examples, hemihydrate was used as a sulfate carrier.

[0077] It can be seen from table 2, example 2, that the substitution of hemihydrate with anhydrites leads to a lowered compressive strength at all stages.

[0078] In table 3, the impact of the nature of the calcium sulfate is shown. Compositions in this table are known compositions activated using CEM III/B and hemihydrate (column 1) and anhydrite (column 2) in an amount of 8%.

[0079] As it is apparent from examples 1 and 2, the use of anhydrites lowers the short term and long term compressive strength but leaves the compressive strength after seven days in the same range as the compositions using hemihydrate.

[0080] Upon activation with a composition of CSA in an amount of 1.5% and CH in an amount of 0.5%, the substitution of the calcium sulfate carrier has an impact on the achievable compressive strength.

[0081] The short term compressive strength is best when using hemihydrate. Using anhydrite leads to relatively low early compressive strength after one day. The use of gypsum leads to an early compressive strength which is higher than the compressive strength of a known activated product regarding a short term compressive strength after one day, but also after seven and 28 days. After 28 days the composition with hemihydrate shows the highest compressive strength.

[0082] In further examples, the anhydrite is partly substituted with hemihydrate (in a weight ratio 2:1) with an activating composition comprising an amount of 1.50% CSA and 0.50% CH. It can be seen that the compressive strength values of the composition in which anhydrite is substituted are between those of a pure anhydrite composition and the pure hemihydrate composition.

[0083] Substitution of another 4% of the anhydrite with the hemihydrate (weight ratio 1:2) so that the content of hemihydrate is 8% and that of anhydrite is 4%, leads to compressive strength which in the early stage is a little bit lower than that that with a content of hemihydrate only but is nearly the same after seven days and is a bit higher after 28 days.

[0084] Further, to show the influence of the amount of hemihydrate its content was raised from a range of 8% to 16% up to 20% while keeping the CSA and CH amounts at the same level of 1.50% and 0.50%. As shown, the compressive strength with 8% hemihydrate is in the early stage lower, after seven and 28 days more or less the same. By raising the hemihydrate content over 12% to 16%, the early stage compressive strength increases after one day and is close to the compressive strength of the composition with 12% hemihydrate. However, it leads to a higher compressive strength after seven and 28 days.

[0085] The compressive strength after seven and 28 days can even be further increased with a composition containing 20% hemihydrate but this results in an early stage compressive strength after one day.

[0086] Therefore, it seems that keeping the hemihydrate content between 6% and 20%, preferably between 8% to 14% leads to a maximum in the available compressive strength over the period from one day to 28 days, while up to 4% anhydrite may be present.

[0087] In table 4, the impact of the slag is shown.

[0088] Two references with 90% blast furnace slag 1 and 89% blast furnace slag 2 respectively, as well as 8% hemihydrate and 2% and 3% CEM III/B are shown. The composition with 3% CEM III/B and slag 2 exhibits a lower compressive strength after one day and a remarkably lower strength after seven days. The compressive strength after 28 days is higher.

[0089] A composition according to the invention with 86% slag 1, 12% hemihydrate and the activating composition with 1.50% CSA and 0.50% CH, displays a remarkable compressive strength after one day, after seven days and even after 28 days in regard to the reference.

[0090] In a second example slag 2 is used. The amount of slag 2 in the invention is 83% and the amount of hemihydrate is raised to 12% as well as the amount of CSA to 3.75% and CH to 1.25%. In comparison to the reference activated with CEM III/B the mid term and long term compressive strength is remarkably higher. In the reference example a higher amount of CEM III/B (3%) is required for sufficient activation.

[0091] The results show that the activation according to the invention leads to improved compressive strengths. The results further show that the composition according to the invention improves the hydration of the slag.

[0092] In comparison to known activation solutions, an increased strength at early stages and at 28 days is achievable. Moreover, with W/C 0.5 even a higher strength class is achievable with the activation according the invention in comparison to a known activation.

[0093] The inventors found that the optimal weight ratio of CSA/CA to calcium hydroxide is 3 to 1, wherein for the calcium sulfate the amounts of anhydrite or hemihydrates should be 6% to 20%, preferably 8% to 16% and even more preferably around 12%.

[0094] All binders mentioned in the tables were mixed with water W/B 0.5 wherein 450 g binder, 225 g water and 1350 g EN sand were mixed as defined in EN 196-1.

[0095] According to the invention, an activator comprising 75% CSA or (CA+gypsum) and 25% CH is preferably present in the SSC composition in an amount of 1 to 5%.

[0096] According to the invention, the SSC composition comprises at least 79% slag, and from 6% to 20%, preferably 8% to 16% and even more preferably around 12% calcium sulfate.

[0097] If hemihydrate is used as calcium sulfate, the inventive composition may further comprise up to 0.05% Retardan 2000P as a setting retardant to avoid flash setting.