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Document Type and Number:
WIPO Patent Application WO/2009/045088
Kind Code:
A CPF liner is available in the form or sheet which comprises of 2 layers of 100% Polypropylene. When properly placed on the surface of formworks (either wood, steel or plastic) it can improve the quality of concrete, cast in such formworks. Especially the concrete cover of up to 25mm depth, being the "fore-most" line of defense, has the distinction of best quality concrete, (irrespective of the mix design or type of cement used). The overall increase in cement content in this outer zone promotes optimum concrete properties such as all round strengths and impermeability, hence the long term durability, even in marine and other aggressive environments. Easy disposable or incinerated are some advantages provided by this material. The use of this CPF liner eliminates the need for release agents (oil or chemical form). Surface fair face concrete finish of near perfect quality is also produced, avoiding the need for added surface coatings or plastering, saving a lot of unnecessary workmanship.

LEE, Boon Ming (No.18, Jalan USJ 2/6H UEP Subang Jaya, Selangor Darul Ehsan, 47500, MY)
Application Number:
Publication Date:
April 09, 2009
Filing Date:
May 14, 2008
Export Citation:
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LEE, Boon Ming (No.18, Jalan USJ 2/6H UEP Subang Jaya, Selangor Darul Ehsan, 47500, MY)
International Classes:
Domestic Patent References:
Foreign References:
Other References:
WILSON D: "CONTROLLED PERMEABILITY FORMWORK (CPF)" CONCRETE, CONCRETE SOCIETY, CAMBERLEY, GB, vol. 28, no. 2, 1 March 1994 (1994-03-01), pages 20-22, XP000439315 ISSN: 0010-5317
Attorney, Agent or Firm:
SHAARI, Zaraihan (Shearn Delamore & Co, 7th Floor Wisma Hamzah-Kwong Hing,No, Leboh Ampang Kuala Lumpur, 50100, MY)
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1. A CPF (Controlled Permeability Formwork) liner comprising of 2 layers of porous materials with good permeability (See Attachment 1), characterized in that no part of the liner is included in or on the formwork.

2. The formwork liner of claim 1, characterized in that absorbs (6) excessive water during the concreting and drains it down.

3. The claim 1 also, characterized in that the liner absorbs and releases up (7) excessive air out from the (4) concrete.

4. The followings are extra claims that CPF Liner usage yield other important results:

• Uniformly fair face finish concrete surface in homogeneous deep coloration.

• Concrete surface with near zero blowholes and blemishes. • All round high surface strengths resistant to abrasion & dusting as a result of lowered w/c ratio and increase in cement content.

• Well cured surface finish of high alkalinity that is hostile to microorganism / fungus growth. • Homogenous increase in cement content up to 100kg / m3 in the 25mm hardened casing.

• For watertight concrete construction, eliminating the need of so called "membrane" or "integral" waterproofing systems.

• No need to use form release agents. • Provides ideal surfaces for coatings minus the need of additional preparatory works.

Extended service life of the R.C. structure thereby reduces cost of maintenance.



Technical Field This invention relates to formwork lining material for improving quality of concrete through normal casting.


Historically, the ancient people of Japan used bamboo mat as CPF, but the result was far from satisfactory. This modern invention relates to the use of PET (Polyethyleneterephthalate) or PP (Polypropylene) as raw materials for CPF, so as to maintain its microscopic pore size of less than 0.03mm.

Despite the many advancements in concrete technology, serious problems continue to plague the performance of so-called "good quality concrete" finished structure incorporating the use of conventional and traditional formwork i.e. timber, steel, plastic, etc. resulting in a greatly weakened and poor concrete finishes, gravely shortening the design life of the structure itself.

Through researches and experiments, the introduction of a controlled permeability liner during the process of placing and compaction of concrete, significantly improved the overall surface finishes, water tightness, long-term durability and life span of the structure.

Disclosure of Invention:

This innovation is utilizing a controlled flow and filtering technology vide a durable synthetic non-woven fabric, designed to promote all round quality control process of placing, compaction and workmanship during concrete casting. Also to produce the ultimate

protective finished concrete cover of a completed structure, where the use of conventional and traditional formwork is unworkable.

This CPF liner is a non-woven fabric, synthetic liner installed in the formwork face to function as a filter media to retain cement particles and allowing the release of entrapped air without the detrimental build up of w/c ratio in the concrete surface zone. All other normal concreting practices are maintained, but no release agents shall be used.

In the process of concrete placing and compaction, the hydrostatic head forces any excess water and air through the controlled pore structure whilst cement fines are prevented from escaping. The liner fabric provides a drainage passage for clear water and air to be stored and subsequently drained.

The water retention capacity in the liner fabric (0.35L/m2) contributes significantly to the curing regime of the cast concrete surface - Fig. 2.

Description of Drawings and Best Mode for Carrying Out the Invention

In order that the invention may be more readily understood and put into practical effect, a preferred example of the invention will now be described with reference to the accompanying drawings, in which :

FIG. 1 illustrates a preferred example of a 5 step procedure on how CPF should be fixed onto a timber formwork.

FIG. 2 illustrates a standard concreting arrangement and how CPF works.

(l)The timber formwork has already been lined tightly by (2) CPF and is ready in receiving (4) concrete to cast, where by set of rebars are installed in place earlier. By using (5) vibrator sufficiently, its vibrations will automatically pressurize the wet concrete against the static CPF, which in turn absorbs any exercise amount of (6) water and drain it down, while any excessive (7) air from the concrete mixture will be released up.

In this way, CPF controls and improves the quality of case concrete.

Attachment 1

Technical Data Sheet

FIG. 1 CPF Liner is available in rolls of width size ranging from 1.5 meter to beyond 3 meters. Always ensure the correct size used to match the intended form to avoid wastage.

Steps 1 It is important to note that CPF-liner is to be installed fully tensioned in all directions to prevent any unwanted waves on the concrete surface finish. CPF-liner shall be installed in the dry and warmth, lengthwise vertically against plywood form. Staple free end to edge of form (preferably away from concrete contact face) allowing at least 50mm all round perimeter overhand and a minimum 200mm at the roll cut end for tensioning purpose.

Step 2 Install Tensioning Clamp and begin tensioning process until no visual slacks is noticeable, then staple down the tensioned zone only.

Step 3&4 In the cross section edges, install tensioner clamps to both sides, pull one free end down and staple down. On the opposing end apply tension till no visual crease is noticeable, then staple down and staple finish the rest. Form the Tie Rod holes when the CPF-liner is fully tensioned and stapled down by using a sharp knife and stapler.

Step 5 Excess CPF-liner overhanging maybe tucked down the form edge and stapled or trimmed off.

Important a) Use a stainless steel knife/blade or Heavy Duty scissor for cutting CPF-liner to avoid feather edges. b) Use only industrial type stapler with staple size minimum

6mm or maximum 8mm. c) Tension clamps and vices shall be as recommended by the Manufacturer/Supplier. d) For Joints, simply overlap (100mm) and staple down or butt. e) For extended lengths or extended width applications consult Manufacturer/Supplier. f) For curved forms or non-plywood faced forms consult Manufacturer/Supplier for guidance.