AU2009212918B2

AU2009212918B2 - Fibre Reinforced Pre-Case Concrete In-Ground Structures and Methods of Manufacture of the Same

Info

Publication number: AU2009212918B2
Application number: AU2009212918A
Authority: AU
Inventors: John Francis Holmes; Patrick Michael Moulton
Original assignee: HOLMES NOMINEES AUST Pty Ltd
Current assignee: HOLMES NOMINEES (AUST) Pty Ltd
Priority date: 2008-09-05
Filing date: 2009-09-04
Publication date: 2013-05-02
Anticipated expiration: 2029-09-04
Also published as: NZ579465A; AU2009212918C1; AU2009212918A1

Abstract

- 18 Cementitious compositions containing: hydraulic cement; aggregate; water; dispersant; synthetic fibres; wherein the synthetic fibres comprise between 1 OOg and 5 8 kg of per cubic metre of the cementitious composition, and wherein in-ground structures cast from said cementitious compositions meet the requirements of AS3600 and AS5 100, methods of constructing pre-cast and cast inground concrete structures therefrom and concrete structures formed using said methods. 04/09/09,dc 17489 cap speci.doc,18

Description

0 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION INVENTION TITLE: Fibre Reinforced Pre-Cast Concrete In-Ground Structures and Methods of Manufacture of the Same The following statement is a full description of this invention, including the best method of performing it known to us:- -2 FIELD OF THE INVENTION This invention relates to in-ground structures, and more particularly to pre cast in ground concrete pits and associated structures, cast in ground concrete structures, methods of manufacturing the same, and compositions for use in such 5 manufacture. BACKGROUND TO THE INVENTION In-ground pre-cast structures and in-ground cast structures are commonly used as storm water pits, electrical pits, communication pits, well pits, valve pits and trade waste and effluent pits and associated products in the civil construction 10 industry. These pits have to withstand the pressure of earth or other materials around them as well as the impact of vehicles passing over them. They are required to last for periods of at least up to 100 years. Many road authorities require storm water pits, for example, to comply with a durability design of 60 to 100 years. This requirement is difficult to achieve with steel reinforced concrete pits with 100 mm thick walls and 15 base as typically used in the industry. The use of steel reinforcing is increasingly expensive as the cost of steel rises. There are also problems where the steel begins to rust due to water ingress into the concrete or through the concrete. This leads to structural instability and collapse of the pits. Additionally, there are significant labour and economic costs due to the weight of steel reinforced concrete pits. The 20 production and use of steel reinforcement also places pressure on the environment through significant CO 2 emissions. US Patent No. 6,942,727 discloses compositions for use in pre-cast cementitious members. However, compositions according to that US Patent are suitable for moulding of members in the flat or horizontal position rather than 25 moulding of cementitious members in a vertical position. As such the compositions are not suitable for forming in-ground pre-cast structures or in-ground cast structures such as storm water pits. The present invention is aimed at ameliorating those problems associated with steel reinforced structures described above. 30 04/09/09,dc 17489 cap speci.doc,2 -3 SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a method of manufacturing pre-cast reinforced concrete in-ground structures. According to another aspect of the invention there are provided pre-cast 5 in-ground reinforced concrete structures formulated from mixes of concrete and fibres including non-metal synthetic fibres. According to another aspect of the invention there is provided a method of manufacturing cast concrete in-ground structures (commonly called cast in situ concrete structures). 10 According to yet another aspect there are provided cast in-ground reinforced concrete structures formulated from mixes of concrete and fibres including non metal synthetic fibres. According to yet another aspect of the invention there are provided compositions for the manufacture of pre-cast in-ground reinforced concrete 15 structures and cast in-ground reinforced concrete structures. DESCRIPTION OF THE INVENTION Compositions for the manufacture of pre-cast in-ground reinforced concrete structures according to one aspect of the invention are predominantly concrete mixes reinforced with synthetic fibres at a dose rate of between 1Og and 8 kg of per cubic 20 metre of concrete mix. Preferably the dose rate is between 2 kg and 6 kg of fibres per cubic metre of concrete mix. More preferably the dose rate is between 3 kg and 5 kg of fibres per cubic metre of concrete mix. According to another aspect of the invention there are provided cementitious compositions containing: 25 hydraulic cement; aggregate; water; dispersant; synthetic fibres; 30 wherein the synthetic fibres comprise between 1OOg and 8 kg of fibres per cubic metre of the resulting cementitious composition. 04/09/09,dc 17489 cap speci.doc,3 -4 According to another aspect of the invention the fibres comprise between 2 kg and 6 kg of per cubic metre of the cementitious composition. More preferably the fibres comprise between 3 kg and 5 kg of fibres per cubic metre of the cementitious composition. 5 According to yet another aspect of the invention there are provided cementitious compositions containing: hydraulic cement; supplementary cementitious materials; aggregate; 10 water; dispersant; synthetic fibres; wherein the synthetic fibres comprise between 1OOg and 8 kg of fibres per cubic metre of the cementitious composition. 15 According to another aspect of the invention the fibres comprise between 2 kg and 6 kg of per cubic metre of the cementitious composition. More preferably the fibres comprise between 3 kg and 5 kg of fibres per cubic metre of the cementitious composition. Preferably, the hydraulic cement is Portland cement. 20 Preferably, the supplementary cementitious materials are one or any combination of fly ash, ground granulated blast furnace slag (GGBF Slag), amorphous silica, silica fume Preferably, the fibres used are polypropylene fibres. However, fibres made from other materials, including other thermoplastic polymers, could be used. 25 Although steel and other metal fibres can be used they are not preferred. This is primarily because of health and occupational reasons and because many metal fibres rust or corrode. Further, the dosage rates of steel fibres for purposes such as shotereteing are significantly high. Dosage rates of between 30 and 60 kgs per cubic metric of concrete or cementitious composition have been indicated for shotcreteing. 30 While metal fibres, usually steel fibres, are used for shotcreteing, (e.g. in tunnelling or mining), slabs, or architectural panels, their use in pre-cast in-ground concrete structures, either alone or in conjunction with reinforcing bars or mesh, is not known. 04/09/09.dc 17489 cap speci doc.4 -5 Preferably the fibres are between 15 millimetres and 100 millimetres long, more preferably they are between 40 millimetres and 60 millimetres long. Preferably the fibres are twisted microfibres. Microfibres or a blend of microfibres and macrofibres are preferred to macrofibres alone as microfibres, or blends of 5 microfibres and macrofibres, are less prone to migrate towards the surface or upper level of a mix during pouring. Especially preferred are twisted microfibres of the type as sold under the trade name Forta Ferro. While Forta Ferro has previously been specified for crack control in supported structures (usually in combination with reinforcing, primarily steel reinforcing bars or mesh) it is not known to have been 10 used previously for reinforcement in in-ground structures. The dosage rate in the present invention is significantly higher than that specified for crack control in supported structures. A cementitious composition according to the present invention has to fall within acceptable parameters for slump and spread to enable it to be properly used in 15 moulds. Accordingly, dispersants, preferably polycarboxylate dispersants, are added prior to moulding. A preferred polycarboxylate dispersant is that sold under the trade name Glenium 27. Preferably the cementitious composition has a slump of between 40 mm and 120 mm. Preferably the cementitious composition has a spread of between 500 20 mm and 900 mm, more preferably a minimum spread of 550 mm. Preferably the water-cementitious content ratio is between 0.30 and 0.45 on a mass : mass basis. Preferably the cementitious content:aggregate ratio is between 600:1600 and 350:1850 on a mass:mass basis. 25 Preferably the aggregate particles are no more than 20 mm in size and the aggregate preferably consists of both sand and coarse aggregate or pebbles, with the coarse aggregate or pebbles being between 7 mm and 20 mm in size. The invention also relates to methods for constructing pre-cast in-ground concrete structures. 30 One such method includes the steps of batch mixing concrete, agitating to a pre-selected slump, adding synthetic microfibres or a blend of microfibres and macrofibres at a rate of between 2 kg and 6 kg per cubic metre of concrete mix and at 04/09/09,dc 17489 cap speci.doc,5 -6 least one dispersant, continuing agitation, adding additional dispersant, ascertaining whether the resultant mixture has a flow spread within the desired limits (i.e., between 500 and 900 mm, more preferably between 550 mm and 900 mm), optionally adding more dispersant and continuing agitation until a desired spread is 5 attained, pouring the resultant mix into moulds in a predetermined manner, allowing the mix in the moulds to cure and removing the mould parts. Preferably the mix is poured centrally over an inverted mould from a concrete kibble with the kibble mouth being held no more than 300 mm above the mould to prevent segregation of the mix. The mix is allowed to flow evenly over the 10 sides of the inner part of the mould in a slow steady fashion so that it occupies the space between the inner part of the mould and the outer formwork of the mould. Neither the concrete mix nor the mould is to be vibrated in any manner at any time during or after the pouring operation. It is important to maintain visual contact to ensure that the flow is even. This is to be done by the pouring operator. The mix 15 must flow at an even rate of around the inner part of the mould and any penetrations in the mould walls. The pour is interrupted at depth intervals of approximately 300 mm up the mould wall. At each interval the pouring stops for one minute to allow entrapped air in the mixture to escape. Pouring is then recommenced. Pouring continues in this manner until the mould has been completely filled. At all times the 20 pouring operator maintains visual contact to ensure that the mix is flowing evenly around the mould walls and any penetrations. Once the concrete mix is completely settled inside the mould and all air has escaped, the top of the mould is floated off level. After a curing compound, such as Masterkure 404, is sprayed onto the exposed surface of the concrete to limit evaporation during the hardening phase of the 25 concrete. This is in accordance with the Applicant's specification for the application of curing compounds. The moulds are left intact for a period of 16 to 18 hours before the removal of the outer formwork. At that stage the product is inspected and labelled and subsequently removed from the mould inner. Penetrations are then removed and pit 30 finishing operations are carried out. The invention also relates to pre-cast in-ground reinforced concrete structures and associated products or cast in-ground, concrete structures formed from 04/09/09,dc 17489 cap specidoc,6 -7 cementitious compositions as aforesaid reinforced with synthetic fibres at a dose rate of between 2 kg and 6 kg of per cubic metre of cementitious composition, preferably where the dose rate is between 3 kg and 5 kg of micro fibre per cubic metre of cementitious composition. 5 Pre-cast in-ground reinforced concrete structures, associated structures, and cast in-ground, concrete structures according to the invention may be square, rectangular, polygonal, circular, elliptical, oval or any variation of these in cross section, according to desired end uses. While they may have nominal internal dimensions of 1000 millimetres x 1000 millimetres where the cross-section is square, 10 they are not so necessarily so restricted. The thickness of the walls and base of the pre-cast in-ground reinforced concrete structures can be between 50 millimetre and 150 millimetre. For most tasks 100 millimetre thickness will suffice. Where concrete structures are cast in-ground the thickness of the walls and base of the structures can be between 50 mm and 450 mm. For most tasks 150 mm thickness will suffice. 15 The pre-cast in-ground reinforced concrete structures or cast in-ground concrete structures according to the invention should comply with the requirements of AS3600 and AS5100. AS3600 is the Australian Standard for concrete structures. AS5100 is the Australian Standard for bridge design. While the Australian Standards contain no specific strength or crush resistance requirements, an engineer designing a 20 structure that is to comply with these Standards must take into account the dead and live loads that may be applied to the structure, such as soil loadings and traffic loadings. When one is determining whether a particular structure falls under these two Australian Standards, one must determine which loads will be applicable to that structure and design the structure to withstand those loads. In-ground pits according 25 to the invention generally are suitable for any situation where the vertical loads do not exceed 21OkN and where the lateral pressures do not exceed 38kPa. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In order that the invention may be more clearly understood, reference is made to preferred embodiments of the cementitious composition, preferred methods for 30 forming pre-cast in-ground structures, and pre-cast in-ground structures. 04/09/09,dc 17489 cap spcci.doc,7 -8 Preparation of the Concrete Mix Example 1 The raw materials, both in type and quantity per cubic metre of concrete, are in accordance with specifications provided by the Applicant. A preferred 5 composition contains 500 kg/m 3 of Portland cement, either being the type GP or equal quantities of type GP and GB (triple blend), a total of 1,680 kg/m 3 of coarse and fine aggregates comprising 130 kg/m 3 of 10 mm aggregate, 680 kg/m 3 of 14mm pebble, and 860 kg/m 3 of sand. A total water content of 160 kg, leading to a water:cement ratio 0.32 on a mass : mass basis is preferred. The raw material is 10 batched into a truck for distribution, with a maximum of 3.5 cubic metres of concrete being blended in a five cubic metre capacity concrete truck. The mix is agitated in the truck for a period of between 18 and 23 minutes while being transported to the moulding site. At that stage the mix is inspected. Under this method the mix should have a slump of between 60 mm and 80 mm. 15 Glenium 27 polycarboxylate dispersant and Forta Ferro microfibres are then added to the mix under the following regime: 2 litres Glenium 27 per cubic metre of concrete is added first, followed by Forta Ferro microfibres at a dosage rate of between 3 kg and 5 kg per cubic metre of concrete. The resulting mixture is agitated for up to three minutes 20 at maximum agitator revolutions. A further 1 litre of Glenium 27 per cubic metre of concrete is then added and the mixture is again agitated for three minutes at maximum agitator revolutions. Following this a check of the spread of the mix on a VPBI spread board is undertaken. The concrete should flow to a final spread of 550 mm minimum with no segregation. 25 There should also be an even distribution of aggregate throughout the concrete paste. If the spread does not conform to these requirements then a further 0.5 litre of Glenium 27 per cubic metre of concrete is added and the resultant mix is agitated for a further two minutes at maximum agitator revolutions. The spread is again checked. If the spread does not conform to 30 the requirements the step of adding 0.5 litres Glenium 27 per cubic metre of concrete followed by agitation for two minutes at maximum agitator 04/09/09,dc 17489 cap spec Ldoc,8 -9 revolutions is repeated for up to three times. If the concrete does not conform to the spread requirement it is then discarded. Example 2 Again a preferred composition contains 500 kg/m 3 of Portland cement, 5 either being the type GP or equal quantities of type GP and GB (triple blend), a total of 1,680 kg/m 3 of coarse and fine aggregates comprising 130 kg/rm 3 of 10 mm aggregate, 680 kg/m 3 of 14mm pebble, and 860 kg/m 3 of sand. A total water content of 160 kg, leading to a water:cement ratio 0.32 is preferred. Glenium 27 polycarboxylate dispersant is added at a dosage 10 rate of 4 litres per cubic metre of concrete along with Forta Ferro fibres at a dosage rate of between 3kg and 5kg per cubic metre of concrete. The raw material is batched into a truck for transport to the moulding site which preferably is close by, with a maximum of 3.5 cubic metres of concrete being blended in a five cubic metre capacity concrete truck. The mix is 15 agitated in the truck for a period of between 18 and 23 minutes. At arrival at the moulding site, the spread of the concrete mix is checked on a VPBI spread board. The concrete should flow to a final spread at 550mm minimum with no segregation and aggregate must maintain an even distribution throughout the concrete paste. If the spread does not conform to 20 the 550mm minimum requirement, I litre of Glenium 27 polycarboxylate dispersant is added per cubic metre of concrete. The mix is agitated for a further 5 mins at maximum agitator revolutions, and spread test is repeated. If the concrete mix does not flow to minimum final spread of 550mm minimum the batch is rejected. 25 Moulding of the Concrete Once the concrete mix is batched and has a required spread, the mix is discharged in 0.7 cubic metre lots into a hopper or kibble which itself is capable of controlling the rate of discharge therefrom. The mix is then poured centrally over the 30 sides of inverted moulds with the kibble mouth being held no more than 300 mm above the mould to prevent segregation of the mix. The mix is allowed to flow evenly over the sides of the mould in a slow steady fashion so that it occupies the 04/09/09,dc 17489 cap spcci.doc,9 - 10 space between the outer formwork of the mould and the inverted mould. Neither the concrete mix nor the mould is vibrated in any manner at any time during or after the pouring operation. The pouring operator maintains visual contact to ensure that the flow is even. The mix must flow at an even rate of around the mould and any 5 penetrations in the mould walls. The pour is interrupted at depth intervals of approximately 300 mm up the mould wall. At each interval the pouring stops for one minute to allow entrapped air in the mixture to escape. Pouring is then recommenced. Pouring continues in this manner until the mould has been completely filled. At all times the pouring operator maintains visual contact to ensure that the mix is flowing 10 evenly around the mould walls and any penetrations. Once the concrete mix is completely settled inside the mould and all air has escaped, the top of the mould is floated off level. After this Masterkure 404 curing compound is sprayed onto the exposed surface of the concrete to prevent evaporation during the hardening phase of the concrete. This is in accordance with the Applicant's specification for the 15 application of curing compounds. The moulds are left intact for a period of 16 to 18 hours before the removal of the outer formwork. At that stage the product is inspected and labelled and subsequently removed from the in-mould inner. Penetrations are then removed and pit finishing operations are carried out. 20 During the first 48 hours after pouring of the article the pits are lifted with a Vic Pits Series 6RF60 or 5RF45 mechanical 360' rotator attached to a suitable fork truck. The rotator attachment has rubber based pads which are no less than 1000 mm x 1000 mm. The attachment must not deliver a force greater than 29 kN over an area of 300 mm x 340 mm. Pits have to be stored for a minimum of 48 hours before 25 transportation to a site. After that time the pits can be lifted on to a transporter using lifting holes provided in the pits for transportation and installation. The pits may then be installed in the locations in accordance with specifications prepared by the Applicant. Example of Invention 30 A preferred form of the invention is a square or rectangular pit consisting of a base and four side walls, and open at the top, manufactured using a concrete mix design with strength between 25 and 80 MPa. The thickness of the walls and base are 04109/09,dc 17489 cap spect.doc,10 - 11 between 50 mm and 150 mm. The resultant pit, if square in cross-section, can have dimensions of up to a maximum of 1000 x 1000 internal with a maximum internal depth of 2000 mm. Penetrations can be cast anywhere in the pit walls and can be of any size and shape to suit connecting pipes and/or box culverts up to 900 mm in 5 diameter. Two or more lift points, in the form of 50 mm diameter lifting holes, are cast through opposing side walls. Pits according to the invention must comply with a minimum loading calculated in AGB Group Computations 5872G-CL-SG02 which are for steel reinforced pre-cast concrete pits. The pits are suitable for use in an environment 10 where the load combinations are up to and including 210 kN vertical point load applied anywhere on the pit and 38 kPa, with a minimum of 25 kPa, combined lateral loads at the ultimate limit state, including traffic surcharge loads in accordance with Australian Standards AS3600 and AS5100. It is to be understood that the foregoing description relates merely to 15 preferred embodiments of the invention, and the variations and modifications will be possible thereto without departing from the spirit and scope of the invention. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise" and variations such as "comprises" and "comprising", are to be understood to imply the inclusion of a stated integer or step 20 or group of integers or steps but not the exclusion of any integer or step or group of integers or steps. Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia. 04/09/09,dc 17489 cap speci.doc, I I

Claims

1. In-ground reinforced concrete structures, either pre-cast or cast in-ground, formed from cementitious compositions reinforced with synthetic fibres at a dose rate of between 2 kg and 6 kg per cubic metre of the cementitious composition, wherein said cementitious compositions contain hydraulic cement, optionally, supplementary cementitious materials, aggregate, water, dispersant and synthetic fibres, wherein the hydraulic cement (or hydraulic cement plus supplementary cementitious material):aggregate ratio is between 600:1600 and 350:1850 on a mass:mass basis, wherein the water:hydraulic cement (or hydraulic cement plus supplementary cementitious material) ratio is between 0.30 and 0.45 on a mass:mass basis, and wherein the said cementitious composition has a spread of between 500 mm and 900 mm at the time casting of the said concentre structures commences.

2. In-ground reinforced concrete structures as claimed in claim 1 wherein the dose rate of synthetic fibres is between 3 kg and 5 kg per cubic metre of the cementitious composition.

3. In-ground reinforced concrete structures as claimed in either claim 1 or claim 2 wherein said synthetic fibres are made from thermoplastic polymers.

4. In-ground reinforced concrete structures as claimed in any one of claims I to 3 wherein said synthetic fibres are polypropylene fibres.

5. In-ground reinforced concrete structures as claimed in any one of claims I to 4 wherein said synthetic fibres are between 15 millimetres and 100 millimetres long.

6. In-ground reinforced concrete structures as claimed in any one of claims 1 to 4 wherein said synthetic fibres are between 40 millimetres and 60 millimetres long. 08/10/12jb17489 claims,12 - 13

7. In-ground reinforced concrete structures as claimed in either claim I or claim 2 wherein said synthetic fibres are twisted microfibres.

8. In-ground reinforced concrete structures as claimed in either claim 1 or claim 2 wherein said synthetic fibres are selected from microfibres, macrofibres or mixtures of microfibres and macrofibres.

9. Cementitious compositions containing: hydraulic cement; optionally, supplementary cementitious materials; aggregate; water; dispersant; synthetic fibres, wherein the synthetic fibres comprise between 1 OOg and 8 kg of fibres per cubic metre of the cementitious composition, the hydraulic cement (or hydraulic cement plus supplementary cementitious material):aggregate ratio is between 600:1600 and 350:1850 on a mass:mass basis, the water:hydraulic cement (or hydraulic cement plus supplementary cementitious material) ratio is between 0.30 and 0.45, and the aggregate comprises both sand and coarse aggregate or pebbles, with the coarse aggregate or pebbles being between 7 mm and 20 mm in size; and wherein the cementitious composition has spread of between 500 mm and 900 mm.

10. Cementitious compositions as claimed in claim 9 wherein the synthetic fibres comprise between 2 and 6 kgs of fibres per cubic metre of said cementitious composition.

11. Cementitious compositions as claimed in claim 9 wherein said synthetic fibres comprise between 3 kg and 5 kg per cubic metre of cementitious composition.

12. A method for constructing pre-cast in-ground concrete structures, including the steps of batch mixing concrete, wherein the concrete comprises hydraulic cement, 08/10/12jb 17489 claims, 13 - 14 optionally, supplementary cementitious materials, aggregate and water, with the hydraulic cement (or hydraulic cement plus supplementary cementitious material):aggregate ratio being between 600:1600 and 350:1850 on a mass:mass basis, and wherein the water:hydraulic cement (or hydraulic cement plus supplementary cementitious material) ratio is between 0.30 and 0.45 on a mass:mass basis, synthetic fibres at a rate of between 1 Og and 8 kg of fibres per cubic metre of cementitious composition and at least one dispersant, agitating and ascertaining whether the resultant mixture has a spread within predefined limits, optionally adding more dispersant and continuing agitation until a desired spread is attained, pouring the resultant mix into moulds in a predetermined manner, allowing the moulds to cure and removing the mould parts.

13. A method for constructing pre-cast in-ground concrete structures, including the steps of batch mixing concrete including synthetic fibres at a rate of between IOOg and 8 kg of fibres per cubic metre of cementitious composition wherein the concrete comprises hydraulic cement, optionally supplementary cementitious material, aggregate and water, with the hydraulic cement (or hydraulic cement plus supplementary cementitious material):aggregate ratio being between 600:1600 and 350:1850 on a mass:mass basis, and wherein the water:hydraulic cement (or hydraulic cement plus supplementary cementitious material) ratio is between 0.30 and 0.45 on a mass:mass basis, and at least one dispersant, agitating to a predefined spread, ascertaining whether the resultant mixture has a spread within predefined limits, optionally continuing agitation, adding additional dispersant, ascertaining whether the resultant mixture has a spread within predefined limits, pouring the resultant mix into moulds in a predetermined manner, allowing the moulds to cure and removing the mould parts.

14. A method for constructing pre-cast in-ground concrete structures as claimed in either claim 12 or claim 13 wherein the dose rate of synthetic fibres is between 2 kg and 6 kg of fibres per cubic metre of cementitious composition. 08/10/12jb17489claims,14 - 15

15. A method for constructing pre-cast in-ground concrete structures as claimed in any one of claims 12 to 14 wherein the desired flow spread is between 500 mm and 900 mm.

16. A method for constructing pre-cast in-ground concrete structures substantially as described herein. 08/10/12jb17489 claims,15