ADDITIVE FOR CEMENT-FREE BUILDING MATERIALS

Abstract

An additive for producing a hardenable building material, especially a mineral composition comprising clays, comprising or consisting of: a) a dispersing agent, selected from aluminates, aluminate precursors, phosphates, silicates and/or polyacrylates, which is capable of dispersing clay particles in an aqueous slurry, and b) a coagulating agent, selected from salts of divalent metal cations, preferably salts of alkaline earth metals and/or iron, especially magnesium, calcium and/or iron salts, capable of causing clay particles to agglomerate in a aqueous slurry.

Claims

1-29. (canceled)

30. An additive for producing a hardenable building material comprising: a) a dispersing agent, selected from aluminates, aluminate precursors, phosphates, silicates and/or polyacrylates, which is capable of dispersing clay particles in an aqueous slurry, b) a coagulating agent, selected from salts of divalent metal cations, which is capable of causing clay particles to agglomerate in an aqueous slurry.

31. The additive according to claim 1, whereby the dispersing agent comprises a polymetaphosphate, an alkali metal silicate, NaAlO.sub.2,Na.sub.2Al.sub.2O.sub.4 and/or Al.sub.2O.sub.3.

32. The additive according to claim 1, whereby the dispersing agent comprises a phosphate and a further dispersant from the group consisting of aluminates, aluminate precursors, silicates and/or polyacrylates.

33. The additive according to claim 3, whereby a weight ratio of the phosphate to the further dispersant is in the range of 0.5 - 10.

34. The additive according to claim 3, whereby a weight proportion of the phosphate is higher than a weight proportion of the further dispersant.

35. The additive according to claim 1, whereby the dispersing agent furthermore comprises a pozzolanic compound, whereby a weight ratio of the pozzolanic compound to the dispersing substance(s) is in the range of 1 - 15.

36. The additive according to claim 6, whereby the pozzolanic compound is selected from fly ash.

37. The additive according to claim 1, whereby the coagulating agent comprises magnesium oxide and/or calcium oxide.

38. The additive according to claim 1, whereby a weight ratio of the dispersing agent to the coagulating agent is in the range of 0.1 - 10.

39. The additive according to claim 1, comprising: a) a dispersing agent comprising a phosphate and a further dispersant selected from the group consisting of aluminates, aluminate precursors, silicates, polyacrylates and combinations thereof, and b) a coagulating agent selected from the group consisting of magnesium oxide, calcium oxide and combinations thereof.

40. The additive according to claim 1, comprising: a) a dispersant comprising: sodium hexametaphosphate; sodium aluminate; whereby a weight ratio of the phosphate to the aluminate is in the range of 2 - 4; optionally a pozzolanic compound; whereby, if a pozzolanic compound is present, a weight ratio of the pozzolanic compound to the other dispersing substances is in the range of 3 - 7; b) a coagulating agent comprising: magnesium oxide optionally a pozzolanic substance whereby, if a pozzolanic compound is present, a weight ratio of the pozzolanic compound to the other coagulating substances is in the range of 3 - 12; and whereby a weight ratio of the dispersing agent to the coagulating agent is in the range of 0.7 - 1.5.

41. The additive according to claim 1, whereby the additive is a kit-of-parts being present in the form of a multi-component composition comprising a first component in a first receptacle that comprises the dispersing agent and a second component in a second receptacle that comprises the coagulating agent.

42. The additive according to claim 1, whereby the additive is essentially free of hydraulic binders and/or clays.

43. The additive according to claim 1, whereby a particle size of the dispersing agent is ≤ 1′100 .Math.m and whereby a particle size of the coagulating agent is ≤ 1′100 .Math.m.

44. The aqueous slurry of claim 1, comprising an additive according to claim 1, mineral particles comprising clays, and water, whereby the aqueous slurry is essentially free of cement.

45. The aqueous slurry according to claim 44, containing 5-80% by weight, in particular 10-70% by weight, especially 25-60% by weight, of water, with respect to the overall weight of the slurry.

46. The aqueous slurry according to claim 44, comprising 0.01-2% by weight of the dispersing agent, based on the total dry weight of fines having a particle size below 100 .Math.m in the slurry, and comprising 0.01-2% by weight of the coagulating agent, based on the total dry weight of fines having a particle size below 100 .Math.m in the slurry.

47. A method for the manufacture of a solid building material comprising the steps of: (i) extracting a mineral fraction comprising clay particles from a soil (ii) optionally adjusting the particle size of the mineral fraction extracted with respect to its clay, sand, gravel or silt content, (iii) preparing a first aqueous slurry from at least a portion of the extracted and optionally graded mineral fraction, (iv) adding a dispersing agent as defined in claim 1, which capable of dispersing the clay particles to the first aqueous slurry to obtain a second aqueous slurry, (v) adding a coagulating agent as defined in claim 1, which is capable of causing agglomeration of the clay particles to the second aqueous slurry to obtain an aqueous building material slurry, (vi) introducing the slurry of aqueous building material into a formwork, and (vii) allow the slurry of aqueous building material to harden so as to obtain a solid building material.

48. The method according to claim 47, whereby the solid building material manufactured is a brick or a clay panel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0198] The drawings used to explain the examples show:

[0199] FIG. 1 a comparison of the dispersing effects of two different dispersing agents on the yield stress of an aqueous slurry;

[0200] FIG. 2 a comparison of the interplay between MgO as coagulating agent and three different dispersing agents (sodium hexametaphosphate; sodium silicate; and sodium polyacrylate) in aqueous slurries;

[0201] FIG. 3 a comparison of the effects of different couples of dispersing agents and coagulating agents on the yield stress of an aqueous slurry;

[0202] FIG. 4 the effect of fly ash on the dispersing effect of sodium hexametaphosphate;

[0203] FIG. 5 the effectivity of three different sodium silicate dispersants with different Si/Na ratios;

[0204] FIG. 6 a comparison of molded bodies obtained with (left side) and without (right side) using a coagulating agent.

EXAMPLES

Additive Components and Additives

[0205] Table 1 shows several dispersing agents whereas table 2 shows different coagulating agents, which can be used in the inventive additives. In table 3, two specific additives are shown. All substances used are commercially available.

TABLE-US-00001 Dispersants No. Na-hexameta-phosphate [g] Al.sub.2O.sub.3 [g] Na-metasilicate [g] Na-polyacrylate [g] Fly ash [g] D1 0.05 0.02 - - D2 0.10 - 0.05 - D3 0.072 - 0.36 D4 0.20 - - - D5 0.10 - 0.10 - D6 - - 0.20 - D7 - - - 0.20 -

TABLE-US-00002 Coagulating agents No. Substance/ [g] Fly ash [g] C1 MgO/0.05 0.02 C2 MgO/0.10 - C3 CaCl/0.10 - C4 CaSO.sub.4.Math.2 H.sub.2O/0.10 - C5 MgSO.sub.4/0.10 - C6 Ca(NO.sub.3).sub.2.Math.4 H.sub.2O/0.10 - C7 Ca(OH).sub.2/0.10 -

TABLE-US-00003 Additives No. Na-hexametaphosphate [g] MgO [g] Fly ash [g] A1 0.14 0.14 1 A2 0.07 0.07 1

[0206] Additives A1 and A2 have been provided as two-component compositions with the dispersing agent and the coagulating agent in two separate receptacles.

Tests

[0207] For testing the effectiveness of the dispersing agents or coagulating agents, respectively, an aqueous slurry comprising 60% by weight of clays and 40% by weight of water was produced. Subsequently, the slurry has been treated with one of the dispersing agents and/or the coagulating agents (for proportions see below).

[0208] FIG. 1 shows a comparison between dispersing agent D4 and D5. Both dispersing agents have been added in a proportion of 0.2% by weight with regard to the dry weight of the total weight of fines in the slurry.

[0209] As evident from FIG. 1, dispersing agent D5 comprising a combination of sodium hexametaphosphate and sodium silicate is more effective in reducing the yield stress of the slurry with increasing time.

[0210] FIG. 2 shows a comparison of the interplay between the coagulating agent C2 (MgO) and three different dispersing agents D4 (NaHMP = sodium hexametaphosphate), D6 (NaSil = sodium silicate) and D7 (NaPA = sodium polyacrylate). Thereby, the proportions of the dispersing agents were kept constant. It can be seen that the effectiveness of the coagulating agent depends on the nature of the dispersing agent used and the concentration of the coagulating agent. Increasing the coagulating agent proportion or the coagulating agent/dispersing agent ratio speeds up the setting of the slurry.

[0211] FIG. 3 shows a comparison of the yield stress of different couples of dispersing agents (D4, D6) and coagulating agents (C2 - C7) right after addition of the additives. Thereby, the proportions of the dispersing agent and the coagulating agent were kept constant. As can be seen from FIG. 3, when using calcium chloride, calcium sulphate or calcium nitrate as the coagulating agent, there is a rapid increase in the yields stress. The highest increase is achieved with sodium hexametaphosphate as the dispersing agent. Having a quick setting opens doors for applications such as the production of bricks, panels, plaster and the like.

[0212] On the other hand MgO, Ca(OH).sub.2 or CaO as coagulating agents delay the setting. Thus, with these coagulating agents, it is possible to provide slurries with a relatively long workability what important e.g. for applications such as poured earth concrete, floor slabs and the like.

[0213] FIG. 4 shows the effect of a partial replacement of sodium hexametaphosphate by fly ash. Sodium hexametaphospate alone (line with square symbols) was used in a proportion of 0.2% by weight with regard to the dry weight of the total weight of fines in the slurry. For the test with flay ash (line with circle symbols), with regard to the dry weight of the total weight of fines in the slurry, a combination of 0.1% by weight of sodium hexametaphosphate and 0.15% by weight of fly ash was used. As can be deduced, the yield stress can be reduced significantly when using fly ash. Since fly ash in general is relatively cheap, this is a highly interesting effect, which allows for reducing the amount of sodium hexametaphosphate and other dispersing substances.

[0214] For reasons of comparison, FIG. 5 shows the effectiveness of three different sodium silicate dispersants with different Si/Na ratios.

Mortar-Like Building Materials

[0215] A mortar-like building material was produced by mixing, based on the dry weight of the mineral particles, 28% by weight of clays and 72% by weight of sand (< 4 mm). Subsequently, water was added in order to produce an aqueous slurry with a proportion of 14% by weight of water with respect to the overall weight of the slurry. The aqueous slurry then was treated in a first step with the dispersing agent of additive A1 in order to dispense the particles and in a second step with the coagulating agent of additive A2 in order to initiate coagulation of the slurry. The concentration of the dispersing agent was about 0.2% by weight, based on the total dry weight of fines having a particle size below 100 .Math.m. Likewise (if used) the proportion of the coagulating agent, was about 0.2% by weight, based on the total dry weight of fines having a particle size below 100 .Math.m.

[0216] In fresh state, the aqueous slurry or the workable mortar-like composition, respectively, in this case has a flow table spread of about 40 - 55 cm.

[0217] For reasons of comparison, a similar slurry was produced. However, in this case, the coagulating agent was omitted. FIG. 6 shows a comparison of the molded bodies obtained with (left side) and without (right side) coagulating agent.

[0218] As can be seen from the object on the right side of FIG. 6, without the addition of the coagulating agent, the mortar composition collapses after 24 hours, whereas in the presence of the coagulating agent (left side of FIG. 6), a self-supporting molded body is obtained.

[0219] Measurements of the compressive strength in line with the standards described above (using prisms of 40×40×160 mm), showed that when using the dispersing agent in combination with the coagulating agent (additive A1), compressive strength after 14 days of about 5.5 MPa are obtained. In contrasts, when omitting the coagulating agent, the maximum compressive strength observed after 14 days was about 3 MPa.

Production of Bricks

[0220] Furthermore, based on compositions comprising clays, sand, water and inventive additives, uncalcined bricks with a final compressive strength of about 15 MPa could be produced. With additional calcination at a temperature of 800° C., bricks with a compressive strength of about 20 MPa were obtained.

[0221] Without addition of the inventive additives, the compressive strength obtainable was about half of the values mentioned above.

Production of Concrete-Like Materials

[0222] Based on compositions comprising clays, sand, gravel water and inventive additives concrete-like materials could be produced with a final compressive strength of about 3 MPa (measured in cubes of 15×15×15 mm).