GB2158762A

GB2158762A - Composite pipes

Info

Publication number: GB2158762A
Application number: GB08412295A
Authority: GB
Inventors: T H Waite
Original assignee: SPUN CONCRETE Ltd
Current assignee: SPUN CONCRETE Ltd
Priority date: 1984-05-14
Filing date: 1984-05-14
Publication date: 1985-11-20
Also published as: GB8412295D0

Abstract

A concrete pipe is provided with a preformed external, inert synthetic plastics coating (2) within which the pipe annulus (1) has been cast. The composite pipe is formed by creating a master sleeve within a concrete casting mould and making a laying-up mould to lay-up a glass reinforced plastics sleeve, the sleeve is cured and inserted in the casting mould, concrete is poured into the cast and allowed to cure, the bonding between annulus and sleeve may be assisted by ties, and the addition of grit before the final cure. <IMAGE>

Description

SPECIFICATION Improvements in and relating to pipes This invention is concerned with improvements in and resulting to pipes and more particularly to pipes made of concrete.

It is known to make pipes of concrete, usually incorporating metal reinforcement, by casting between static spaced concentric cylindrical shuttering or by spin casting concrete in cylindrical shuttering. Pipes made by either procedure have been used for laying in open trenches and subsequent burial and in forming subterranean ducts by creating a subterreanean bore and successively inserting into the bore entry as the bore advances, pipe lengths, each newly inserted length being driven forward by jacks and carrying forward with it the end- to-end pipe lengths previously inserted.

Such pipes for use in these procedures are satisfactory but the concrete has limited life in certain conditions.

According to one aspect of this invention there is provided a concrete pipe which has a preformed external, inert synthetic plastics coating within which the pipe has been cast.

According to another aspect of this invention there is provided a method of making a concrete pipe in which an inert synthetic plastics sleeve is formed having an external surface corresponding to the internal surface of the pipe mould so as to be insertable with a sliding fit in the mould, casting a concrete annulus within the sleeve with which the sleeve will bond on setting of the concrete and removing the composite cast pipe from the mould.

Features and advantages of this invention will appear from the following desription of one embodiment given by way of example only, reference being made to the accompanying cross-section of joint details of adjacent pipe lengths.

Each pipe length comprises a cast concrete annulus 1 within an inert synethtic plastics sleeve 2, the pipe lengths being interengageable by way of a female end 3 of one receiving a male end 4 of an adjacent pipe length. The sleeve 2 of each pipe length is formed preferably by creating a master sleeve within a concrete casting mould and making a laying-up mould, preferably of timber, from the master, the laying-up mould being used to lay-up a glass reinforced plastics sleeve, the plastics material being inert. An isophthalic resin is presently preferred.

The sleeve is preferably finished on its internal surface with a resin rich tissue to ensure the sealing in of all the fibres and thereby close any microscopic paths through the sleeve along any fibre which might otherwise be exposed at each surface of the sleeve and present a path for water to pass through the sleeve wall.

Also on the internal surface of the sleeve, preferably tie means (not shown) are provided, such as conventional wire or plastic ties, these being layed in during completion of the laying-up operation of the sleeve so that the ties are anchored in the sleeve.

The cured sleeve is then slipped axially into the concrete casting mould, reinforcing rods are set up within the sleeve, preferably engaging within the exposed parts of the ties and the concrete is then poured, cast and allowed to cure.

The sleeve will itself bond with the concrete but that bond is backed up by the ties. In addition before final curing of the sleeve a coarse sand or grit may be sprinkled over the internal surface to assist in bonding with the concrete.

The female end of each pipe length is defined by one exposed end of the sleeve while the male end is defined by an end of the cast concrete annulus, coated by the other end of the sleeve, of reduced outside diameter and preferably having a channel 6 to receive a sealing ring (not shown). Various forms of joint can be adopted. There is shown a packing ring 7 to lie between the annular end faces 8, 9 of the cast concrete but here again a variety of arrangements are possible.

In forming a subterranean duct, a boring machine may be used which may be remotely controlled from the surface. As this machine advances through the ground, pipe lengths as described are inserted successively into the bore entrance and as each pipe length is inserted it is driven forward by jacking means which bear upon the rear end face, relative to the direction of advance, of the concrete annulus of that pipe length which will abut at its leading end face the preceding length and drive forward that length and any others ahead of it. The packing ring 7 will assist in obtaining abutment of adjacent end faces of adjacent concrete annuli fully around those faces.Also the internal surface of the female end of each pipe length is preferably ground after removal from the casting mould to provide for accurate fit with a male end, the internal surface of the sleeve at the female end being on that surface during laying-up which is remote from the laying-up mould.

To illustrate an example of the type of pipe length to which this invention can be applied, the pipe dimensions may be 1780mm outside diameter, 1470mm inside diameter and 2.5m length. The sleeve may be of Smm thickness except at the female end, where as illustrated it is thickened.

A pipe length as described has the advantage that the life of the concrete will be increased by the protection afforded by the sleeve, as compared with an internal coating which would survive longer than the concrete but not have the same structural strength after deterioration of the concrete as an externally coated concrete pipe. As an added advantage it has an external surface of lower coefficient of friction than concrete and thus reduce the power required for jacking and will withstand adequately the likely abrasive effect of being jacked. A pipe as described may also be used for laying in a trench particularly where the ambient conditions are not conducive to use of the known cast concrete pipes having no protective coating.

Claims

1. A method of making a composite pipe comprising the steps of forming an inert synthetic plastics sleeve and casting a concrete annulus within the sleeve.

2. A method according to claim 1 wherein the sleeve is formed within a casting mould for concrete and has an external surface corresponding to the internal surface of the casting mould so as to be insertable with a sliding fit in the mould and so that the concrete annulus can bond with the internal surface of the sleeve.

3. A method according to claims 1 or 2 wherein the sleeve is formed by creating a master sleeve within a concrete casting mould and making up a laying-up mould from the master, the laying-up mould being used to lay-up the sleeve.

4. A method according to any of the preceding claims wherein the sleeve is finished on its internal surface with a resin rich tissue to seal in glass fibres and provide an internal fluid barrier.

5. A method according to any one of the preceding claims wherein tie means are provided on the internal surface of the sleeve, and reinforcing rods are set up in the casting mould and engage the exposed parts of the ties.

6. A method according to any preceding claim wherein before final curing, coarse sand or grit is sprinkled over the internal surface of the sleeve to assist bonding with the concrete annulus.

7. A method according to any of claims 1 to 6, wherein the plastics sleeve is made from an isophthalic resin.

8. A pipe comprising a preformed, external inert synthetic plastics sleeve and a concrete annulus cast within the sleeve.

9. A pipe according to claim 8, wherein the pipe is inter-engageable with adjacent pipes by way of male and female ends.

10. A pipe according to claim 9, wherein the female end of each pipe is defined by a portion of the internal surface of the sleeve which is exposed and the male end is defined by an end of the cast concrete annulus coated by the sleeve and the composite having a reduced outside diameter.

11. A pipe according to claim 10, wherein the internal surface of each female end is ground to ensure an accurate fit with each respective male end.

12. A pipe according to claim 10 or 11, wherein the external surface of the male end has a channel formed therein to receive a sealing ring.

13. A pipe according to claim 9, wherein complete abutment of adjacent pipe lengths is by way of a packing ring inserted in between the respective end faces of concrete annuli.

14. A pipe according to any one of claims 8 to 13, wherein the concrete annulus is provided with reinforcing rods.

15. A pipe according to claim 14, further comprising tie means anchored in the sleeve and engaging said reinforcing rods.

16. A pipe according to any one of claims 8 to 15, wherein the plastics sleeve is made from an isophthalic resin.

17. A method of making a composite pipe substantially as herein described with reference to the accompanying drawing.

18. A pipe substantially as herein described with reference to the accompanying drawing.