Stop Press - Textile Concrete: The First Decade
Non-woven (textile) concrete was researched as Netcem by Prof Dave Hannant et al., University of Surrey / Department of Civil Engineering in 1970 as an alternative to asbestos fibre cement. That industry continued for another 30 years, for them now very costly years.
PP fibrillated mesh (Carricrete) created a pseudo-ductile product, stiffened by including Cemfil. Netcem was licensed to Montacatinni as Retiflex and was used in:
- Europe to make corrugated roof sheeting,
- New Zealand to make cattle drinking troughs,
- South Africa to make FloLok drain channels for the Gold Mines.
In 1994 it was announced that following two takeovers the Retiflex plant would close; this would have created a vacuum in the South African mining industry. But looms were standing, a textile was designed / made / tested. Inhouse testing by Grinaker-Duraset, showed that their FloLok drain channels were 33% stiffer than those made using Retiflex. In 1996 South Africa had an already proven replacement. SA patent 3203 / 1997 USA 2000; Canada, Australia and Europe followed.
The basis of the patent: bonded yarns for weft insertion usually into a leno weave (mesh) textile. In three-point bend tests this resulted in 40% stiffer textile concrete than unbonded yarns. With Retiflex / 100% + 33% + 40% (say 175%), and for 2006 we have BondTex. The bonds can be made inline, on looms, knitting machine, or simple lay-up on ultrasonic bonding machines.
BondTex: bottom right of collage - patent filed.. February 15, 2006
Textile concrete is flexible: it can be ribbed, flanged, bonded to rigid sheet materials, such as Curv or SS., or supported by a steel space frame. The three yarns shown left centre have 6 mm pitch bonds (or as required), the basis of SA 3203 1997. The yarns have a bonded spun / fibrous sheath. This forms the interface for cement (or other) matrix. BondTex (February 15, 2006) can be made using bonded yarns, plus nodal bonds; is a bonded textile. An allotrope of BondTex will be used to reinforce the webs of concrete honeycombs.. 60 - 75% weight saving, in stiff / tough panels, etc.
Layers of CemForce or (under development) BondTex can be used to make CemPly®, illustrated top row of the collage; the honeycomb is a micro-version of the waffle shown to its left. A customized CemForce/Curv/CemForce backing plate was used for the photo-litho reproduction of the lady; the lion head was laser engraved from a custom made CemPly® plate; the Isibonelo sign is an example of bonded appliqué work - CemPly®.
Isibonelo was made and sealed into steel shutters in eGoli (the City of Gold); it means “We are showing the way”.. the through coloured CemPly® Logo and 6 mm thick text (I = 75 cm high) weighed 60 kg; four backing plates 125 kg / 1.5 x 3 m. Gross weight 2.5 T. Isibonelo was lifted into place with other shutters by the main contractor. During the pour, its backing plates became wet and mechanically bonded and framed by the pour.
N.B. The 100 mm radii in the corners of the installed sign, the point of departure being the transfer of the sign direct from its shutters to the face of the pour. The bolts securing the sign to the shutters were removed prior to stripping.. comment on site: “hope it’s the right way up?”
For innovative / quality concrete work, Murray & Roberts Construction was recognised in The Fulton Awards, the sign by South African National Sign Association; immediately afterwards, we surfaced on the Web, now with our own website.
Carricrete/CemFil/Netcem/CemForce/BondTex are stepping stones on a 40 year path, that extended back 50 years to propylene being condensed into polypropylene (1954). In the 1960s the technique was awarded a Nobel Chemistry Prize, and PP was being used in concrete. Ultrasonic welding originated in the 1950s as a method of bonding polypropylene; today is used to bond your car together, a reason to choose polypropylene for automobiles. No glue to come unstuck.. autogenous.. bonding by ultrasonics, we have bonded CemStrands at 1 km/min; expect to speed up the manufacture of textiles.