Hardening mixture

Abstract

The invention concerns a hardening mixture, which is manufactured from finely ground recycled materials. The hardening mixture comprises 10 to 20 % of ground gypsum, 35 to 59 % of ground blast-furnace slag, 10 to 30 % of ground mineral wool, glass or brick and 4 to 14 % of ground calcium hydroxide, where all ratios are given as a percentage by weight.

Description

[0001] HARDENING MIXTURE

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a cement-like mixture comprising recycled constituents which hardens with the addition of water.

[0004] PRIOR ART

[0005] One of the most essential goals of a circular economy is to save natural resources by means of effective and sustainable use of materials. Utilization of residues, side streams and demolition materials is pivotal for an effective circular economy.

[0006] Huge amounts of cement and concrete made with cement are used in construction. The most often used cement is Portland cement, which is manufactured from ground Portland cement clinker with the addition of gypsum. The manufacturing of cement requires a lot of energy and thus it produces a sizable portion of global carbon dioxide emissions. More environmentally friendly cements have been developed by replacing the Portland cement with constituents like fly ash and blast-furnace slag. As the share of Portland cement decreases, it results problems of lower compression strength than concrete has and longer hardening time of the resulting concrete, which limit use of such cements.

[0007] An example of reducing Portland cement and at the same time reducing carbon dioxide emissions is a supersulfated cement, which typically includes 80 to 85 % of blast-furnace slag, 10 to 15 % of gypsum and about 5 % of Portland cement. The supersulfated cement hardens slowly and at best reaches a compression strength that is about half of the compression strength of a conventional concrete.

[0008] Patent publication FR2200843A5 discloses a fiber-reinforced cement material which comprises 5 to 40 % fiber reinforcement.

[0009] Patent publication JPS5727958A discloses a material, which comprises slag, gypsum and slaked lime.

[0010] Patent publication JPS5771956A discloses an inorganic material, which comprises slag, gypsum and fiber material.

[0011] Patent publication EP2647610A2 discloses a board made of an inorganic material, which comprises blast-furnace slag, gypsum and reinforcing fibers. OBJECT OF THE INVENTION

[0012] An object of the invention is a hardening mixture, which solves or at least alleviates problems of the cements of the prior art and utilizes a recycled constituent or side streams.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014] The object of the invention is achieved with, for example, a hardening mixture, which comprises very finely ground gypsum, blast-furnace slag, recycled construction material and slaked lime (calcium hydroxide). In addition, small amounts of cement can be used, for example Portland cement or cement products made of that. Hardening time and compression strength can be improved further by using an accelerator.

[0015] DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of a first aspect of the invention is a hardening mixture, which comprises finely ground dry constituents in certain proportions expressed as percentage by weight. The hardening mixture comprises 10 to 20 % ground gypsum, 35 to 39 % ground blast-furnace slag, 4 to 14 % ground slaked lime and 10 to 30 % mineral wool, glass or brick ground to a 0 to 200 micrometer particle size. Hardening of the mixture is achieved with the addition of water. In a very advantageous embodiment, all the constituents of the hardening mixture are ground to a 0 to 200 micrometer particle size.

[0017] According to an embodiment, the hardening mixture comprises preferably 10 to 20 % gypsum, very preferably 11 to 17 % gypsum. In an embodiment said gypsum comprises gypsum board ground with its facing paper, which can be from industrial side streams or from a demolished building. Preferably the gypsum is ground to a 0 to 200 micrometer particle size. In an embodiment, the gypsum is dead burnt plaster, alpha gypsum or both dead burnt plaster and alpha gypsum.

[0018] The hardening mixture comprises preferably 35 to 59 % blast-furnace slag, very preferably 45 to 49 % blast-furnace slag. In an embodiment part of the blast-furnace slag is substituted by oil shale ash. Preferably at most 50 % of the blast-furnace slag is substituted by oil shale ash. Preferably the blast-furnace slag or a mixture of the blast-furnace slag and the oil shale ash is ground to a 0 to 200 micrometer particle size.

[0019] The hardening mixture comprises preferably 10 to 30 % or 15 to 30 % ground mineral wool, ground glass or ground brick, very preferably 19 to 25 % ground mineral wool, ground glass or ground brick. In an embodiment, said percentages can be only mineral wool, only glass or only brick. In an embodiment, said percentages can include a small amount of impurities, for example at most 5 % impurities. Mineral wool, glass and brick can be demolition materials from demolished buildings or those can be from industrial side streams. When utilizing demolition materials, it’s difficult, and often also unnecessary, to aim to a completely pure material. For example, there may be mortar as impurity among bricks, paper as impurity among mineral wool, etc. The material is often purer when utilizing side streams from industry but availability is more limited. In an embodiment all of the mineral wool, glass and brick can be utilized. In an embodiment mineral wool and glass, mineral wool and brick or glass and brick can be utilized. Regardless of which of these materials are utilized or where the materials originate from, the materials are ground to a 0 to 200 micrometer particle size.

[0020] The hardening mixture comprises preferably 4 to 14 % slaked lime, very preferably 5 to 10 % slaked lime. The slaked lime can be a virgin raw material but also industrial side streams or residue can be utilized. For example, calcium carbide resulting from manufacturing of acetylene can be utilized.

[0021] In an embodiment the hardening mixture also comprises 3 to 10 % by weight of demolished concrete that has been ground to a 0 to 200 particle size. The demolished concrete means concrete that has been demolished or discarded from whatever use it had. Preferably the utilization of demolished concrete in the hardening mixture replaces utilization of mineral wool, glass and brick.

[0022] In an embodiment the hardening mixture also comprises 5 to 30 % by weight of cement that includes clinker. That can be for example Portland cement or a commercial cement mix including Portland cement, such as for example a fast-setting cement mix. Hardening time and compression strength of an end product can be further improved by using relatively small amount of conventional cement that includes clinker in the hardening mixture.

[0023] Benefits of the hardening mixture of the first aspect of the invention over conventional cement are significantly smaller carbon dioxide emissions and vast utilization of recycled materials.

[0024] A second aspect of the invention is a method of producing an object from the hardening mixture according to the first aspect of the invention, aggregate and water. In an embodiment, an accelerator is also used.

[0025] The method according to an embodiment of the second aspect of the invention comprises steps of mixing constituents of the hardening mixture, obtaining water an amount that is 50 to 100 % of the mass of the hardening mixture, obtaining aggregate an amount that is 450 to 700 % of the mass of the hardening mixture, mixing said constituents of the hardening mixture, aggregate and water to form a smooth mass, allowing the smooth mass to harden at least 24 hours. In an embodiment, the mass is allowed to harden in a room temperature (20 °C). In an embodiment, the mass is allowed to harden in a temperature of at least 30 °C, where the hardening is faster than in the room temperature.

[0026] The aggregate consists of stone aggregates having various granularities, such as sand or mechanically crushed stone, concrete, brick, expanded clay or other similar stone aggregates.

[0027] In another embodiment, the method comprises steps of mixing constituents of the hardening mixture, obtaining water an amount that is 50 to 100 % of the mass of the hardening mixture, dissolving calcium chloride to said water where the amount of the calcium chloride is at most 1 % of the mass of the hardening mixture, obtaining aggregate an amount that is 450 to 700 % of the mass of the hardening mixture, mixing said constituents of the hardening mixture, aggregate and water to form a smooth mass, allowing the smooth mass to harden at least 24 hours. In an embodiment, the mass is allowed to harden in a room temperature (20 °C). In an embodiment, the mass is allowed to harden in a temperature of at least 30 °C, where the hardening is faster than in the room temperature.

[0028] The calcium chloride dissolved in the water accelerates a hardening reaction of the hardening mixture so the calcium chloride acts as an accelerator. Preferably small amounts of a second accelerator or a third accelerator is used in addition to the calcium chloride. The term "small amount" in this context means an amount that is at most 1 % of the mass of the hardening mixture and preferably at most 0.4 % of the mass of the hardening mixture. Typical additives for concrete, such as plasticizers, accelerants, frostproofers, retarders, etc. can be used if needed in addition to the calcium chloride or instead of the calcium chloride. Suitable additives for accelerating hardening of concrete, i.e. accelerators, can be potassium silicate, magnesite, metakaolin and calcium hydroxide (slaked lime). Commercial accelerators include PENTARAPID products CR 1001, AG 3 and AG 4 from Pentachem sir, and also CHRYSO Turbo F100 accelerator. Preferably one or more of the previously mentioned accelerators are used together with the calcium chloride as an accelerator. For example, by using CHRYSO Turbo F100 accelerator, use of the calcium chloride can be reduced to 0.5 % of the mass of the hardening mixture and preferably to at most 0.1 to 0.4 % of the mass of the hardening mixture. In an embodiment an accelerator, which accelerates hardening of concrete, is added to the hardening mixture.

[0029] Use of the calcium chloride is preferably minimal in order to avoid problems relating to corrosion.

[0030] In an embodiment an object of about one cubic meter is produced with 300 to 350 kg of the hardening mixture, 1850 kg of aggregate and 150 to 300 kg of water depending on the use. A semi-dry mass is achieved when using 150 kg of water, where as a pourable mass is achieved by using 170 to 300 kg of water.

[0031] It is obvious to the skilled person in the art that, as technology develops, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not limited to only the examples presented above, rather they may vary within the scope of the claims.

Claims

CLAIMS1. A hardening mixture, which comprises as percentage by weight10 to 20 % of ground gypsum,35 to 59 % of ground blast-furnace slag,10 to 30 % of ground mineral wool, ground glass or ground brick, and4 to 14 % of ground calcium hydroxide, wherein the hardening mixture is characterized in that said ground mineral wool, ground glass or ground brick has been ground to a 0 to 200 micrometer particle size.

2. The hardening mixture according to claim 1, wherein said gypsum comprises ground paper-faced gypsum board.

3. The hardening mixture according to any one of claims 1 to 2, wherein said ground mineral wool, ground glass or ground brick is demolition material that has been ground to a 0 to 200 micrometer particle size4. The hardening mixture according to any one of claims 1 to 2, wherein said ground mineral wool, ground glass or ground brick is stone wool dismantled from a building, where said stone wool that has been ground to a 0 to 200 micrometer particle size.

5. The hardening mixture according to any one of claims 1 to 4, where said blast-furnace slag has been ground to a 0 to 200 micrometer particle size.

6. The hardening mixture according to any one of claims 1 to 5, where the hardening mixture also comprises 3 to 10 % of demolished concrete that has been ground to a 0 to 200 micrometer particle size.

7. The hardening mixture according to any one of claims 1 to 6, where all constituents of the hardening mixture have been ground to a 0 to 200 micrometer particle size.

8. The hardening mixture according to any one of claims 1 to 7, where the hardening mixture comprises 11 to 17 % of ground dead burnt gypsum as a percentage by weight.The hardening mixture according to any one of claims 1 to 8, where the hardening mixture comprises 45 to 49 % of ground blast-furnace slag as a percentage by weight. The hardening mixture according to any one of claims 1 to 9, where the hardening mixture comprises 19 to 25 % of ground mineral wool, ground glass or ground brick as a percentage by weight. The hardening mixture according to any one of claims 1 to 10, where the hardening mixture comprises 5 to 10 % of ground calcium hydroxide as a percentage by weight. The hardening mixture according to any one of claims 1 to 11, where the hardening mixture comprises 5 to 30 % of cement that includes clinker as a percentage by weight. A method of producing an object using the hardening mixture of any one of claims 1 to 12, where the method comprises steps of mixing the constituents of the hardening mixture, obtaining water an amount that is 50 to 100 % of the mass of the hardening mixture, obtaining aggregate an amount that is 450 to 700 % of the mass of the hardening mixture, mixing said constituents of the hardening mixture, aggregate and water to form a smooth mass, and allowing the smooth mass to harden at least 24 hours. A method of producing an object using the hardening mixture of any one of claims 1 to 12, where the method comprises steps of mixing the constituents of the hardening mixture, obtaining water an amount that is 50 to 100 % of the mass of the hardening mixture, obtaining aggregate an amount that is 450 to 700 % of the mass of the hardening mixture, adding an accelerator, which accelerates hardening of concrete, mixing said constituents of the hardening mixture, aggregate, water and accelerator to form a smooth mass, andallowing the smooth mass to harden at least 24 hours.