Construction material based on a mineral binder comprising synergistically effective hydrophobisation agent combinations

Abstract

The invention concerns construction materials based on a mineral binder, which include a synergistically effective hydrophobisation mixture. The invention also relates to methods for processing of such construction materials and the use of a synergistically effective mixture for the hydrophobisation of a mineral binder based construction material.

Claims

1. A construction material based on a mineral binder comprising a mineral binder and a synergistically effective mixture of Ca(OH).sub.2, a silicon-based hydrophobisation agent and a fatty acid salt-based hydrophobisation agent, or precursors of a fatty acid salt-based hydrophobisation agent, wherein Ca(OH).sub.2 is present in a ratio of 2:1 to 20:1 relative to combined weight of said silicon-based hydrophobisation agent and said fatty acid salt-based hydrophobisation agent, and wherein the precursors of a fatty acid salt-based hydrophobisation agent is selected from fatty acid and esters thereof, wherein Ca(OH).sub.2 is present in an amount of 1 wt. % to 15 wt. %, based on total dry weight of said construction material, wherein said silicon-based hydrophobisation 13 as agent is present in an amount of 0.01 wt. % to 4.99 wt. %, based on total dry weight of said construction material, wherein said fatty acid salt-based hydrophobisation agent, or precursors of said fatty acid salt-based hydrophobisation agent, is present in an amount of 0.01 wt. % to 4.99 wt. %. based on total dry weight of said construction material, and wherein said construction material has a lower average total absorptivity for water as determined in accordance with EN 520:2004 5.9.2, as compared to a comparable construction material that is free of Ca(OH).sub.2, said silicon-based hydrophobisation agent, and said fatty acid salt-based hydrophobisation agent or precursors of said fatty acid salt-based hydrophobisation agent.

2. The construction material according to claim 1, wherein the fatty acid in the fatty acid salt-based hydrophobisation agent is a C.sub.4 to C.sub.30 fatty acid, preferably a C.sub.8 to C.sub.24 fatty acid and more preferably a C.sub.12 to C.sub.22 fatty acid, or a mixture of such acids.

3. The construction material according to claim 1, comprising a total content of 0.02 to 5 wt.-% and preferably 0.04 to 1 wt.-% of all hydrophobisation agents based on the dry weight of the construction material.

4. The construction material according to claim 1, wherein the mineral binder is a hydraulic binder, preferably the hydraulic binder comprises a calcium sulfate based binder and/or a cement binder, most preferably the calcium sulfate based binder comprises more than 60 wt.-% calcium sulfate based on the total weight of the mineral binder.

5. A method for the preparation of a construction material based on a mineral binder comprising the steps of: (i) mixing water with a mineral binder and a synergistically effective mixture of Ca(OH).sub.2, a silicon-based hydrophobisation agent and a fatty acid salt-based hydrophobisation agent, or precursors of a fatty acid salt-based hydrophobisation agent and optionally additional additives; (ii) shaping the construction material, and (iii) allowing the construction material to set, wherein Ca(OH).sub.2 is present in a ratio of 2:1 to 20:1 relative to combined weight of said silicon-based hydrophobisation agent and said fatty acid salt-based hydrophobisation agent, and wherein the precursors of a fatty acid salt-based hydrophobisation agent is selected from fatty acid and esters thereof, wherein Ca(OH).sub.2 is present in an amount of 1 wt. % to 15 wt. %, based on total dry weight of said construction material, wherein said silicon-based hydrophobisation agent is present in an amount of 0.01 wt. % to 4.99 wt. %, based on total dry weight of said construction material, wherein said fatty acid salt-based hydrophobisation agent, or precursors of said fatty acid salt-based hydrophobisation agent, is present in an amount of 0.01 wt. % to 4.99 wt. %, based on total dry weight of said construction material, and wherein said construction material has a lower average total absorptivity for water as determined in accordance with EN 520:2004 5.9.2, as compared to a comparable construction material that is free of Ca(OH).sub.2, said silicon-based hydrophobisation agent, and said fatty acid salt-based hydrophobisation agent or precursors of said fatty acid salt-based hydrophobisation agent.

Description

DESCRIPTION OF THE INVENTION

(1) In the following, the invention will be illustrated further by means of examples, which must however not be construed has having any limiting implications on the invention.

EXAMPLES

(2) A plaster composition was formulated from calcium sulfate hemihydrate as mineral binder, rheology modifiers, setting regulators and fillers by addition of an appropriate amount of water to provide the required fluidity. An exemplary composition for Sample 6 is given in Table 1.

(3) TABLE-US-00001 TABLE 1 Components Amount [kg] Calcium sulfate hemihydrate 530 Calcium hydroxide 50 Filler comprising fine limestone <0.1 mm, 398.6 quartz sand <0.8 mm) Cellulose thickener 2.5 Accelerators 0.2 Starch based rheology modifiers 0.6 Retarders comprising phosphate based 2.1 retarders and organic based retarders. Silicon-based hydrophobisation agent 3 (Silres Powder E) Fatty acid salt-based hydrophobisation 2 agent (Bearophob ECO) Perlite 11 Total 1000

(4) Aside from the hydrophobisation agents and the calcium hydroxide, all other samples have an identical composition to the composition of Sample 6, which is shown in Table 1. This identical composition is summarized as plaster composition in the first column of Table 2. The only other exceptions are Samples 1 and 8, where the total amount of plaster composition differs. In both samples, the difference in the amount of the plaster composition is solely attributable to a difference in the amount of calcium sulfate hemihydrate. Table 2 focuses on the components that were varied: calcium hydroxide (Ca(OH).sub.2), the silicon-based hydrophobisation agent and the fatty acid salt-based hydrophobisation agent. More specifically, Baerophob ECO (a 1:1 mixture of sodium oleate and calcium stearate by Baerlocher GmbH) and Silres Powder E (a silane based hydrophobisation agent by Wacker Chemie AG) were used. All quantities are given in the respective parts by weight per 1000. The amount of the plaster composition, incl. the mineral binder, is given on a dry basis.

(5) TABLE-US-00002 TABLE 2 Plaster composition comprising mineral binder, filler, Fatty acid additives other Si-based salt-based than Ca(OH).sub.2 hydro- hydro- and hydro- phobisation phobisation phobisation agents Ca(OH).sub.2 agent agent Sample 1* 950 50 0 0 Sample 2 945 50 5 0 Sample 3* 995 0 5 0 Sample 4* 945 50 0 5 Sample 5 945 50 2 3 Sample 6 945 50 3 2 Sample 7 945 50 4 1 Sample 8 944 50 4 2 *Comparative samples

(6) The thus prepared samples were shaped (i.e. in a cast or mold), allowed to set and dried to a constant weight. Subsequently, the average total absorptivity and, in the case of Sample 8, also the capillary absorptivity of the samples was determined.

(7) For the determination of the average total absorptivity, 4416 cm prisms of the set compositions were analyzed as described in EN 520:2004, 5.9.2.

(8) For the determination of the capillary absorptivity, samples were assessed according to EN 1015-18:2002.

(9) The results of these tests are provided in Table 3 below:

(10) TABLE-US-00003 TABLE 3 Average total Capillary absorptivity absorptivity [%] [kg/m.sup.2min.sup.0.5] Sample 1* 32.5 Sample 2 3.7 Sample 3* 16.3 Sample 4* 34.8 Sample 5 3.4 Sample 6 3.7 Sample 7 3.4 Sample 8 2.5 0.2 *Comparative samples

(11) As is apparent from Table 3, the samples comprising only one of the hydrophobisation agents (with the exception of Sample 2) provide only moderate hydrophobisation at a respective agent content of about 0.5 wt.-% based on the dry weight of the construction material. Interestingly, the sample comprising both calcium hydroxide and a silicon-based hydrophobisation agent (Sample 2) provided much lower absorptivity than Sample 3 with only the silicon-based hydrophobisation agent.

(12) The performance of Samples 5 to 7 is about comparable or slightly better than for Sample 2 and significantly better than that of Sample 3 and 4, which only comprise one of the hydrophobisation agents. In Sample 8, where the combined hydrophobisation agent content was increased slightly from 0.5 to 0.6 wt.-%, the average absorptivity was reduced even further.