Concrete Cloth is flexible cement impregnated fabric. Process of making concrete cloth, properties, materials and applications in construction is discussed.
Concrete has evolved enormously and drastically from a long time. New technologies, methods and materials have been found and invented to suit the requirements.
Innovation like bacterial concrete, green concrete and other have emerged in recent days one of the concrete technology that has evolved in the form of Concrete Cloth.
Concrete Cloth is a cement impregnated flexible fabric. It hardens when hydrated to form thin, durable, fireproof and waterproof concrete layer.
The popularity of concrete cloth is due to its physical properties mainly flexibility. Like a soft cloth, concrete cloth can be used to cover the surface of an irregular structure.
Concrete cloth takes the shape of outer profile of a structure. This concrete does not need a plant or mixing equipment. They come in the form of rolls, just spread the role in the required place and water it.
Concrete cloth is made of three-dimensional fiber matrix, made up of a specially formulated concrete mix. A PVC layer is done in the bottom surface to make it waterproof. On the other side of the concrete cloth it is added with polyethylene and polypropylene yarns fiber.
Fig: Concrete Cloth Section and Details
Installation of concrete cloth is 10 times faster compared with traditional concrete. It can be easily installed, nailed or fixed to any host by nails or adhesives. They are easily portable by a human eliminating the use of machines on site.
History of Concrete Cloth
The technology of concrete cloth was found for the use of emergency shelters. This technology wasn’t commercialized for other works. Later researches were made on concrete cloth and incredible product was introduced to construction field.
The concept of concrete cloth was first proposed by Brewen and Crawford in 2005. Later the research was conducted and the British Engineering Company found the Revolutionary material called as Concrete Cloth or Concrete Canvas. It is a new era product in the field of construction.
Material Properties of Concrete Cloth
The material property of concrete are its strength and physical properties:
Strength of Concrete Cloth
The typical strength is discussed below:
An early high strength is required for concrete cloth. Compressive strength test on concrete cloth is based on ASTM C473 part 07. Compressive strength of 38 MPa was obtained on 7th day. The 10th day compressive strength was recorded at 40MPa and then 10 day compressive Young’s modulus was 500 MPa.
Bending Test on Concrete Cloth
It is the ability of material to resist the bending forces. The 7-day minimum bending stress is 3.3 MPa and bending modulus is 180 MPa.
Abrasive Resistance Test
The resistance exerted by the body for abrasive action is abrasion resistance. As per ASTM C1353 part 8, the standard method used to calculate a materials abrasive resistance, concrete cloth lost 60% less weight than that of marble over 2000 repeated cycles.
Physical Properties of Concrete Cloth
Concrete cloth is normally available in 3 thicknesses, 5mm, 8mm and 13 mm thick. Theoretically there is no limit in the thickness of concrete cloth. A typical thickness can be in between 2 to 15 mm.
The factors that limit the thickness of concrete cloth is its ability to penetrate liquid or water through it to the lower and interior base of the material for hydration.
The time required by the concrete cloth from end of mixing to initial set of concrete cloths is known as setting time.
For concrete cloth, the initial setting time should be greater or equal to 120 minutes and final setting time is greater than or equal to 240 minutes. Concrete cloth can achieve 70 to 80% of its strength in 24 hours of hydration.
Before hydration of concrete cloth, the density is 1500 kg/m3 and after hydration the dry density increases 30 to 35% the range of 1952-2050 kg/m3.
Process of Making Concrete Cloth
The process of placing, hydrating and achieving the strength of the concrete cloth is explained in the following steps,
Preparation of Subgrade
The subgrade on which the concrete cloth will be placed is to be prepared properly so as the concrete cloth takes the shape of its host.
So, any type of rocks, uneven shape regions or vegetation are to be properly taken care of. Compact and smooth surface is to be prepared prior to the placement of concrete cloth.
Placement of Concrete Cloth
Now the concrete cloth is placed upon the prepared subgrade. One cloth is overlapped over the other to get a strong bond.
The PVC coated layer is placed at the bottom so that the water supplied for the hydration of concrete cloth doesn’t seep through it and water is lost. The fibrous layer is placed on the top or upwards.
After the placement of concrete cloth, the extra concrete cloth is cut down which is exceeding the required area of installation. This cutting must be done using the commonly used cutting tools.
Fastening or Anchoring
Now the concrete cloth is to be anchored or fixed to the host material so that it doesn’t displace. For soil, host nails or anchors or screws are used. For hard surface adhesives are also used.
Hydration of Concrete Cloth
Hydration of concrete cloth can be done by following two methods:
In this method, the concrete cloth is dipped into water for not less than 90 seconds and placed.
The concrete cloth is placed and the water is sprayed on it. Care must be taken that the direct Jet of pressure water is not used as it washes wash away the cementitious material from the fiber.
Saline or non-saline water can be used for hydration of concrete cloth. The water to cement ratio is 1:2 by weight.
Re-Spraying or Curing
The required amount of water is supplied to concrete clothes at the first time only, but due to warm temperature or when placed on steep or vertical surfaces some amount of water is lost. To replenish, spraying is done after an hour or two.
Application of Concrete Cloth in Construction Works
Concrete cloth has been used in many fields of civil engineering, some of the common uses are:
Concrete Cloth for Slope Protection
The slopes of dams, roads, embankments are usually installed with truffing to protect it from soil erosion, reduction of shear strength caused by many factors, but the maintenance cost of truffing is more.
Concrete cloth is used on slopes for slope stabilization, erosion control for both permanent and temporary slope protection.
Mining Applications of Concrete Cloth
The inner surface of the mine is to be protected from listening and breaking. At this places usually sprayed concrete is used. By using concrete cloth at mines, the cost can be reduced by 20% when compared to sprayed concrete.
Dust Suspension by Using Concrete Cloths
One of the uses of concrete cloth is in defense sector is that it can be used as the dust suspension. Places like helipad, due to turbulent air current created by helicopter rotor, the loose soil particles are washed up into the air.
This could negatively affect human beings, wildlife and machines. This concrete cloth can be used around helipad which controls the washing up of loose soil.
Applications of Concrete Cloth in Ditching
Ditches are used for water channels or waste water can be lined with concrete cloth, which protects the water seeping from ditches. Its quick and less expensive to install as compared to the conventional way of ditching.
Concrete Cloth Applications in Pipe Protection
Overland and underwater pipelines usually undergo corrosion or direct impacts. To overcome these, concrete cloth can be used as a coating for pipes which provide protection against corrosion and impacts. It provides superior tough shield.
Advantages of Concrete Cloth
Portable: They are easy to carry, transport and deployed without specialized equipment.
Rapid: Concrete cloth can be hydrated either by being sprayed or by being fully immersed in water. Once hydrated, it remains workable for four hours and hardens to 80% strength within 24 hours. This time can be reduced by adding accelerants into the dry mix at the point of manufacture.
Easy to use: Dry concrete cloth can be cut or tailored using simple hand tools. It can be easily repaired or upgraded using existing cement products.
Flexible: This can be easily nailed or anchored through before setting.
Strong: The fiber reinforcement acts to prevent cracking, absorbs energy from impacts and provides a stable failure mode.
Waterproof: The PVC backing on one surface ensures that concrete cloth is completely waterproof.
Hydration: Hydration takes place by filling the sack with water. Hydration is aided by the fiber matrix, which helps water into the cement.
Setting: The concrete cloth cures in the shape of the below structure on which it is placed and 24 hours later the structure is ready to use.
Adaptable: Concrete cloth is currently supplied on 1.2m-wide rolls but can be manufactured with a roll width of up to 5m. The cloth can be produced in a range of thicknesses from 5–20mm.
Durable: The Concrete cloth is chemically resistant and will not degrade in UV.
Fireproof: The Concrete cloth is a ceramic-based material and will not burn.
Limitation of Concrete Cloth
- Concrete cloth cannot be over hydrated and an excess of water is always recommended.
- Do not jet high pressure water directly onto the Concrete cloth as this may wash a channel in the material.
- Concrete cloth has a working time of 1-2 hours after hydration. So do not move CC once it has begun to set.
- Working time will be reduced in hot climates.
- If Concrete cloth is not fully saturated, the set may be delayed and strength reduced.
Market Availability of Concrete Cloth
Concrete cloth is available in different sizes and different thickness as per their uses. The come in bulk rolls or batched rolls. The market available concrete cloth specifications are: