By Shibi
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Page 1
CHAPTER-1
INTRODUCTION
Concrete
cloth is an upcoming revolution in civil world, which in turn have a wide range
of application in rapid construction, in state of emergency etc. due to its own
physical property, mainly, flexibility and easy to use. Among various engineering
applications of 3D spacer fabric reinforced cementitious composites; concrete
canvas (CC, the concept was first proposed by Brewin and Crawford in 2005) is
one of the most promising products.
Concrete
cloth is a flexible concrete impregnated fabric that hardens on hydration to
form a thin, durable, water and fire proof layer. Like soft cloth,CC can
closely cover the surface of arbitrary structure or element before using. Its
shape is completely the same as the outer profile of the structure or element
where CC is covered. Essentially, it’s concrete on a roll.CC allows concrete
construction without the need for plant or mixing equipment. Simply position
the canvas and just add water. The water does not need to be potable, and
bore-hole water, river water or seawater can be used. No major ground
excavation or foundation work is required.
Concrete
cloth consists of a 3- dimensional fiber matrix containing a specially
formulated dry concrete mix. A PVC backing is provided on one surface to make
it water proof. The other side of the cloth is aided with a hydrophilic fiber
(polyethylene and polypropylene yarns) and thus hydration occurs by drawing
water into the mixture.
The cloth may be hydrated either by
spraying or by being fully immersed in water. To check whether water penetrated
through the whole thickness of the sample, it was cut along the cross section
after hardened. It was seen that the density of the paste in bottom layer was
similar to the top layer. Therefore, the current water-spaying method guarantees
that the water penetrated through the whole thickness of sample. The
time-dependent compressive strength of cubic CSA-based CC sample with
dimensions of 15 mm x 15 mm x 15 mm was also determined to obtain the suitable
curing age for tensile test and 10-day compressive strength of the sample
almost reached the maximum mechanical strength value. The geometric patterns of
outer textile substrates of 3D spacer fabric play a vital role in loading
capacity and the solid fabric dominate the tensile strength and ultimate
elongation.
They can be easily nailed, stapled
or coated with an adhesive for easy attachment to other surface. Once set, the
fibers reinforce the concrete, preventing crack propagation & providing a
safe plastic failure mode. Compared to traditional concrete solutions, it is
faster, easier and more cost effective to install and has the additional
benefit of reducing the environmental impact of concreting works by up to 95%.
Typical
installation speeds are up to 10 times faster than conventional concrete
solutions. It is available in man portable rolls eliminating the need for plant
on site and allowing concrete installation in areas with limited access.
Prior
to hydration, Concrete cloth layers can be cut to length using basic hand tools
eliminating the hazards associated with using power tools in high risk
environments. The concrete is pre-mixed so there is no need for mixing,
measuring or compacting but just add water. It greatly reduces transportation
cost and on site storage. It is a low mass, low carbon technology.
Fig 1.1 CC cross section
(Source: www.concrete canvas.co.uk)
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