AU2005200215A1

AU2005200215A1 - Aggregate with light-weight granular stone for the production of concrete as well as a method for its production

Info

Publication number: AU2005200215A1
Application number: AU2005200215A
Authority: AU
Inventors: Georg Partlic; Anton Trenkwalder
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-01-20
Filing date: 2005-01-18
Publication date: 2005-08-04
Also published as: DE502004000404D1; EP1561734A1; ATE321741T1; IL166296A0; EP1561734B1

Abstract

An aggregate comprises a hydraulic binder mixture containing ash with a calcium oxide content of 10-20 wt.%, and additive(s). An independent claim is also included for the production of the aggregate.

Description

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P001ool Section 29 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Aggregate with light-weight granular stone for the production of concrete as well as a method for its production The following statement is a full description of this invention, including the best method of performing it known to us: AGGREGATE WITH LIGHT-WEIGHT GRANULAR STONE FOR THE PRODUCTION OF CONCRETE AS WELL AS A METHOD FOR ITS

PRODUCTION

00 o The present invention relates to an aggregate with light-weight granular stone for the production of concrete, comprising a hydraulic binding agent mixture as well as one or several additives. The invention additionally relates to a method Ofor the production of this aggregate.

N Aggregates of the above-mentioned type are known from EP-A 1 188 726.

According to this teaching, the starting point was the idea to replace naturally occurring aggregates, such as sand and gravel, since their use is dependent on the local geological conditions. The use of naturally occurring aggregates was replaced by using waste materials, such as those derived from metal smelters.

Thus, an aggregate in the form of a loose bulk material was produced from smelter's sand with the addition of cement. While this granular additive is handled easily as it can be dosed in a simple manner during the course of the production of concrete, its setting properties with the neat cement of the concrete are sometime less than satisfactory.

Here, the invention intends to provide a solution.

According to the invention, an aggregate of the above-mentioned type is proposed which is characterised in that in the hydraulic binding agent mixture, ash with a calcium oxide content (free calcium content) of 10 to 20% by weight relative to 100% ash is present. This ash is preferably one which has been obtained from the burning of bark or wood. Therefore, waste products occurring in the paper and cellulose industries can advantageously be re-used.

Advantageously, the aggregate also consists of an hydraulic binding agent in the form of cement.

In terms of the invention, the water or water of crystallisation that is present in the aggregate, is also regarded as an additive. This is the case because, for hydraulic binding agents, the additives harden after the application of water.

Therefore, it can never be excluded that, also after the hardening process, water of crystallisation is present in the aggregate in bonded form. Swelling and/or pore creation agents prove to be particularly preferred additives for achieving a lightweight granular stone.

A shell-like structure of the additive is to be regarded as a light-weight granular stone in terms of the invention, the additive essentially consisting of a 0o core and a shell region whereby in the core region the hydraulic binding agent is predominantly deposited in the form of cement whereas in the shell region, the hydraulic binding agent is deposited in the form of the ash with the calcium 0 content of 10 to 20% as mentioned before.

1 Further advantageous embodiments of the subject matter of the invention 0 10 are disclosed in the dependent claims.

SFurthermore, the invention relates to a method for the production of the aggregate in terms of the invention, which is characterised in that, in a first step of the method, the larger part of the hydraulic binding agent in the form of ash with the further hydraulic binding agent in the form of cement together with the addition of water as well as further additives such as swelling and/or pore creation agents is homogeneously mixed, and that, in a further step of the method where the remaining ash is added, the aggregate is pelletised to create the light-weight granular stone.

This first pelletising step may advantageously be followed by one or two pelletising steps in order to shape the form and surface of the light-weight granular stone accordingly. Furthermore, a drying stage can be added to the one or more pelletising steps.

Advantageously, the mixing process can be carried out in a first step of the method, namely in a concrete mixing plant, whereas the subsequent pelletising steps can be carried out in a mobile unit, for example in a pelletising plant fitted into a sea container or onto a truck. This results in the advantage that the stationary unit's capacity is used up by the mixing process whereas, with the mobile unit, the aggregate according to the invention can be delivered to several production plants for producing the concrete.

In the following, the invention is explained in more detail by way of an exemplary embodiment for the implementation of the invention as well as by way of Figures 1 and 2 wherein Fig. 1 shows a possible embodiment of the aggregate according to the invention and Fig. 2 a schematic example of the method for carrying out the method according to the invention.

For carrying out the method according to the invention, the hydraulic binding agent in the form of ash is placed, for example, in a cascade or gravity 0o fed mixer 4. Here, the larger part of the ash employed, about 60 to 70% by weight, is blended with the additional mixture components inside the storage vessels while being stirred constantly. Using appropriate dosing, the additional 0 hydraulic binding agents, for example cement 9, the additives such as water 1 as well as pore creation agents 11, are introduced via pipelines. The components 0 10 are thoroughly mixed which can be controlled via the dosing speed and the rotational speed of the mixer. Subsequently, the remaining ash 8 is added into the pelletising unit 5. However, it is also conceivable to distribute the ash 8 into further pelletising units 6, 7 so that, in a further pelletising process, form and surface of the pellets can be shaped accordingly.

This process results in a shell-like structure of the inventive aggregate 1 as it is created, in Fig. 1 for example, in the form of a core region 2 consisting essentially of cement and a shell region 3 consisting mainly of ash. The advantageous application of the additive in the production of concrete results from the shell-like structure of the light-weight granular stone, the advantage being that, as a result of the ash particles being mainly deposited in the shell region 3, the aggregate pellets 1 do not stick together. Furthermore, as a result of using the ash particles as well as the pore creation agents, the surface contains many pores such that, when the aggregate 1 is used in subsequent concrete production, a satisfactory bonding, i.e. interlocking, of these pellets with the neat cement of the concrete is guaranteed.

Summing up it can be said further that the free calcium content of 10 to by weight being present in the hydraulic binding agent in the form of ash, is of great importance in particular for the pelletising process because the relatively high calcium oxide content leads to a quick reaction with the additional hydraulic binding agent, namely the cement, so that the aggregate according to the invention is ready for storage within a few minutes. Furthermore, the pelletising process can, independent of the stationary mixing process, be arranged in mobile

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4 O units so that the aggregates produced according to the invention can be delivered to several production units for the production of concrete.

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Claims

1. An aggregate for concrete production, consisting of a hydraulic binding Sagent mixture as well as of one or several additive(s), characterised in that ash 00 with a calcium oxide content (free calcium content) of 10 to 20% by weight relative to 100% by weight of ash, is present in the hydraulic binding agent mixture. (Ni

2. The aggregate according to claim 1, characterised in that the hydraulic binding agent is obtained, in the form of ash, from the burning of bark or wood. (Ni

3. The aggregate according to claim 1 or 2, characterised in that cement is present as a further hydraulic binding agent.

4. The aggregate according to one of the claims 1 to 3, characterised in that the ratio of ash:cement equals 1:1. The aggregate according to one of the claims 1 to 4, characterised in that, as further additive(s), swelling and/or pore creation agent(s) is (are) used.

6. The aggregate according to claim 5, characterised in that the additive(s) content lies in the range of 0.1 to 20% by weight relative to 100% by weight of the aggregate.

7. The aggregate according to one of the claims 1 to 6, characterised in that the light-weight granular stone is available in the form of spheres or pellets.

8. The aggregate according to claim 7, characterised in that the light-weight granular stone has a shell-like structure with the core region containing mainly cement and the shell region containing almost exclusively ash.

9. The aggregate according to one of the claims 1 to 8, characterised in that the aggregate has a raw density of 500 to 2000 kg/m 3 0 10 A method for producing an aggregate according to one of the claims 1 to 9, c characterised in that, in a first process step, the larger part of the ash is Shomogeneously mixed with the further hydraulic binding agents such as cement as well as possibly additives and that, in a second process step, the light- weight granular stone of the aggregate is formed by pelletising.

11. The method according to claim 10, characterised in that the remaining Sportion of ash is added in one or several steps downstream of the first pelletising ci step. c 12. The method according to claim 10 or 11, characterised in that the mixing process is carried out in a stationary unit and the pelletising step or the pelletising steps are carried out in mobile units. DATED this 19th day of January 2005 GEORG PARTLIC AND ANTON TRENKWALDER WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA