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Wednesday, January 11, 2017

CONCRETE CLOTH

By Shibi

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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