AU2008200188A1

AU2008200188A1 - Improved concrete mixture

Info

Publication number: AU2008200188A1
Application number: AU2008200188A
Authority: AU
Original assignee: HUNTER PRE CAST CONCRETE Pty Ltd
Current assignee: HUNTER PRE-CAST CONCRETE Pty Ltd
Priority date: 2007-09-26
Filing date: 2008-01-14
Publication date: 2009-04-09

Description

Australian Patents Act 1990 Regulation 3.2 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title Improved concrete mixture The following statement is a full description of this invention, including the best method of performing it known to me/us:- P/00/011 5102 P \WPDOCS\ARS\SPECE\I I Jln 20333651_fur. tc.Cls CPr nCcz Py LdCompci csmdoc-14/01/2008 00 -1- SIMPROVED CONCRETE MIXTURE ct Background of the Invention This invention relates generally to concrete and more particularly to an improved 00 00 concrete mixture.

Concrete is a widely used structural material which finds many applications. For r example buildings can be constructed using structural panels formed from concrete. There 00 are several factors which affect the use of concrete panels in the construction of buildings.

ri 10 For example concrete panels of the type described above are often manufactured away from the building site. As such the weight of such panels becomes an important consideration because of the need to transport the panels as well as the handling of such panels during the erection of the building. Furthermore in recent years there has been an emphasis placed on improving the energy efficiency of a building. For example the heat losses and gains of a building have become an important design criteria. In cooler climates there is a desire to reduce heat losses in a building. Conversely in warmer climates there is a desire to try and minimise heat gains.

It is an object of the present invention to provide an improved concrete mixture which improves one or more of the aforementioned design criteria.

Summary of the Invention According to one aspect of the present invention there is provided a concrete mixture comprising cement, fine and coarse aggregate which when mixed with water and cured forms a concrete material characterised in that the coarse aggregate comprises bottom ash.

Bottom ash is a non-combustible by-product of coal which is burned in a furnace typically used for the generation of steam, electric power or both.

According to another aspect of the present invention there is provided a concrete mixture comprising: cement; fine aggregate; and coarse aggregate which includes bottom ash wherein when the mixture is mixed with water and allowed to cure for 28 days a concrete material is produced which has a compressive strength of at least 20 Mpa and an R value of 0.08 or greater and preferably 0.11 or greater.

P\WPDOCS'ARSISPECIEN IJ.20335651 I i)uir Pc-C" Concro Py PidConipI t spw dc.14/01/2008 00 -2- Preferably the bottom ash included in the coarse aggregate is sized up to 40 mm and may be present in the mixture up to 1 100kg/m 3 The fine aggregate may include bottom ash which may sized down to 5mm fractions or less.

The fine aggregate may comprise naturally occurring or manufactured sand 00 00 although some of the fine aggregate may include bottom ash fines. The fine aggregate is preferably less than 5mm fractions.

N The cement may for example be Portland cement blended cement or a combination 00 thereof. Preferably the cement is present in the range of 250kg/m 3 to 500kg/m 3 The N, 10 cement may be dosed to produce a minimum compressive strength of 25 MPa at twenty eight days.

Preferably the water is town, dam or from a recycled source and may be used at a rate up to 200 litres/m 3 The concrete mixture may further include fire clay which may be present up to 20kg/m 3 The concrete mixture may further include chemical admixtures. Typical admixtures may include WRAc an entraining, WRRe, Ac, HWR set controlling and/or water reducing admixtures.

Preferably, prior to mixing with water the mixture includes 15% to 30% wt cement, 25% to 45% wt coarse aggregate and 25% to 45% wt fine aggregate.

According to another aspect of the present invention there is provided use of bottom ash as an aggregate for the preparation of a concrete material which may be a concrete mixture as described above.

According to another aspect of the present invention there is provided a building panel of concrete material formed from a concrete mixture as described above.

It has been discovered that by the use of bottom ash in the concrete mixture a relative light weight structural material can be produced while maintaining its structural integrity. In addition the material produced has a relatively low thermal resistance. The R value is a measure of a products insulating ability. The higher the R value the more resistance it has to heat loss or gain. It has been discovered that panels formed from the concrete mixture in preferred forms described above have an R value of about 0.11 compared to panels produced from conventional mixtures which have an R value of about 0.06. Conventional concrete mixtures have voids from about 2% to 5% whereas the P:\WPDOCS'ARSWJPECIEI I Jan2033565) _Hanlo P-Cas Ccrae Pty Lid Coapictc sp doe. 141011009 -3concrete mixture of the invention has voids up to 23%. It is believed this may be the reason for the improved lower thermal resistance.

Example A panel specimen formed from a concrete mixture according to the invention was tested to determine its thermal resistance.

The composition of the mixture is set out below: Material Quantity/M3 Source Cement 420 Kg/m 3 Morgan Cement Port Kembla Minus 40mm Bottom Ash 600 Kg/m 3 Blue Circle Ash Bayswater Power Station Minus 5mm Bottom Ash 430 Kg/m 3 Blue Circle Ash Bayswater Power Station Manufactured Sand 250 Kg/m 3 Hunter Quarries Karuah Fireclay 10 Kg/m 3 Building Product Supplies Thornton Adva 1.6 Kg/m Grace Australia Calcium 37 2.1 Kg/m 3 Grace Australia WRDA PA 3.6 Kg/m 3 Grace Australia AEA 0.2 Kg/ 3 Grace Australia Water 180 1/m 3 Mains Supply The concrete manufactured using conventional batching processes.

The thermal resistance measurements represent the average of six 4-hour test periods meeting the criteria in ASTM C1363 The mean sample temperature during testing was 23+1°C for temperature differentials of 18+0.5K and 12+0.5K as outlined in AS/NZS4859.1 Set out below is a summary of the results of the tests.

Product Description Specimen Mass Calculated Bulk Density Thermal Resistance, R, Thermal Conductance, C Thermal Conductivity, k 2.4x2.4m monolithic pre-cast concrete panel with a nominal thickness of 100mm 1090+5 kg 1910+1% kg/m 3 0.1 9.10+5% W.m-2.K l 0.903+8% P\WPDOCSARSWECI\I J _20335651 _Iiunta Pre-m i r ay L dConipka cpvmd d--410l2008 00 -4- 00 00 of the 100mm thick wall. The total thermal resistance for the wall systems (Rt) were calculated using the assumed values of 0.12 and 0.04 m 2 .K/W for internal air and external air film resistances as outlined in Appendix K of AS/NZS4859.1 These values are 00 Sindicated in Table 1 together with the thermal conductance and thermal transmittance (Ui 10 value) for each wall system.

Table 1. Thermal Transmission Properties of Pre-cast Concrete Walls 100-200mm Thick Wall Thickness Rm C-value Rt U-value (mm) (m 2 (W.m 2

.K'

t (m 2 (W.m-.K 100 0.11 9.03 0.27 3.69 150 0.17 6.02 0.33 3.07 175 0.19 5.16 0.35 2.83 200 0.22 4.51 0.38 2.62 The measurement error reported for the thermal conductivity above will also apply to the Rm component of the R 1 values together with any discrepancy in material thickness associated with the production of the pre-cast panels and those resulting from the possible introduction of a second layer of reinforcement.

ASTM C1363-97, "Standard Test Method for the Thermal Performance of Building Assemblies by Means of a Hot Box Apparatus", ASTM, West Conshohocken, PA, United States.

AS/NZS 4859.1:2002, "Materials for the thermal insulation of buildings. Part 1: General criteria and technical provisions", Standards Australia, Sydney, NSW, Australia.

P:WPDOCSARSSPECIDI I i. 2033565 I3Iwoa PR-C Conroc Pty LdComple cspm d-14/0112008 00 SThroughout this specification and the claims which follow, unless the context requires Sotherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

00 00 0 Finally, it is to be understood that various alterations, modifications and/or additions may CI be incorporated into the various constructions and arrangements of parts without departing 00 Sfrom the spirit or ambit of the invention.

(N

Claims

2. A concrete mixture according to claim 1 wherein the bottom ash included in the coarse aggregate is sized up to
3. A concrete mixture according to claim 1 or 2 wherein fine aggregate comprises bottom ash.
4. A concrete mixture according to claim 3 wherein the bottom ash included in the fine aggregate is sized less than A concrete mixture according to any one of claims 1 to 4 wherein the concrete material produced has a compressive strength of at least 25 MPa.
6. A concrete mixture according to any one of claims 1 to 5 wherein the concrete material produced has an R value of 0.11 or greater.
7. A concrete mixture according to any one of claims 1 to 6 wherein prior to mixing with water the mixture includes 15 to 30% wt cement, 25 to 45% wt coarse aggregate, and to 45% wt fine aggregate.
8. A concrete mixture according to any one of claims 1 to 7 wherein the concrete mixture further includes fire clay. P:\WPDOCSARSSPECIEMl I IJ.20335651 1.l Pr-Caul C-~rte Py Ud CopIvc spm dmcc14011200$ 00 -7-
9. A concrete mixture according to any one of claims 1 to 8 wherein the mixture t further includes WRAc, WRRe, Ac, and/or HWR.
10. Use of bottom ash as an aggregate for the preparation of a concrete material from a 00 concrete mixture according to any preceding claim. S11. A building panel comprising concrete material formed from a concrete mixture 00 according to any one of claims 1 to 9.