Bendable Concrete

Bendable concrete is also called as Engineered Cementitious Composites, or ECC.

It belongs to a class of cementitious composites with ultra-ductile fibre reinforcement that is distinguished by their high ductility and precise crack width control.

In this article you’ll learn:

• What is Bendable concrete?
• Types of Bendable concrete.
• Merits and Demerits of the Bendable concrete.
• Lots more.

So, if you’re ready to go with Bendable concrete, this article is for you.

Let’s dive right in.

What is Bendable Concrete?

Polymer fibers that have been micro mechanically constructed are used to reinforce bendable concrete.

The same basic components as conventional concrete is used to create ECC, but a High-Range Water Reducing (HRWR) agent is also added to ensure good workability.

Purpose of Bendable Concrete:

• Making lightweight concrete is difficult because it requires lowering the density without compromising strength or cost.
• ECC includes minuscule silk-coated polyvinyl alcohol fibres and extremely fine silica sand (manometer thick).
•  The surface coating prevents the fibres from fracturing by allowing them to start slipping when they are overloaded.
•  It stops the fibre from rupturing, which would cause significant cracking.
• ECC is particularly well suited for critical components in seismic zones because of its excellent energy absorbing qualities.

Composition of Bendable Concrete:

The components of an engineered cementitious composite are: (53 grade of OPC).

• Sand.
• Water.
• A strong plasticizer
• PVA fibre has a 40-m diameter and a length of 12 mm.

Since ECC Concrete naturally forms microcracks with significant deflection, coarse aggregates are purposefully omitted from the mix.

Corresponding to an ECC Concrete property, coarse aggregates widen cracks.

Features of Bendable Concrete:

Flexibility of Concrete:

In flexible concrete, the fibers serve as the reinforced material.

Unlike fiber reinforced concrete, the composite strain in ECC hardens after a fracture.

 When fibres rupture in fibre-reinforced concrete, cracks begin to appear, this lowers the capacity of fibre-reinforced concrete to withstand stress.

 However, flexible concrete performs well in this test because of its high fracture toughness and high damage tolerance.

Concrete that is bendable has unique qualities, such as:

• Flexible concrete has a tensile strength between 10 and 15 MPa.
• Flexible concrete has a compressive strength of up to 70MPa.
• Flexible concrete develops self-healing properties that aid in filling the microcracks with a complex byproduct of cement’s reaction with rainwater.
• Concrete that is bendable has a maximum tensile strength of 3 to 5%.
• Flexible concrete has a three hundred times higher strain capacity than regular concrete. This is the element that gives concrete flexibility.

Bendable Concrete Mix Ratio Design Processing:

PVA fibre at 2% was the initial mix proportion, and the superplasticizer dose was 30 ml per slab mould (700x150x60 mm), 10 ml per cube mould (70.6×70.6×70.6 mm), and 0.5 ml per slab mould (700x150x30 mm).

By using this ratio, workability could be attained. Concrete is mixed in a 1:2 (cement: sand) ratio with a w/c of 0.5.

1.Bendable Concrete Casting Procedure:

• The mixing had an impact on ECC Concrete’s achievement.
• This indicates that good mixing techniques can improve the quality and performance of ECC Concrete.
• The homogeneity of the mixed material has an impact on the concrete’s quality as well.
• Flexural tests were performed on the slab both before and after the addition of new concrete.
• For greater concrete strength and better cement-PVA fibre bonding, proper concrete mixing is advised.
• The mixing process was started after the concrete mix design was completed. ECC Concrete was hand-mixed during the mixing process.
• The steps for hand mixing were as follows:
  • Add sand,
  • Cement,
  • PVA fibres gradually,
  • Then 50% water and superplasticizer.
  • As you gradually incorporate more water and superplasticizer, keep mixing until a homogeneous mixture is achieved.

2.Concrete specimen placing, compacting, and casting:

The bendable concrete mold needs to be oil-coated before concrete is poured in order to make it easier to remove concrete specimens.

ECC concrete had to pass a workability test before it could be put into concrete molds to test its hardened properties.

 To lessen the honeycombing, tamping was done with a tamping rod as fresh concrete was being poured into the molds.

 It enables the fresh concrete to be fully compacted, allowing any trapped air voids to escape. If the concrete was not appropriately compacted, its maximum strength cannot be achieved.

Concrete was then leveled on the concrete’s surface following this procedure.

The first task after the concrete has been placed and compacted is levelling.

Then concrete in the mold was left overnight to allow the freshly laid concrete to set after it had been leveled.

3.Curing of Concrete Specimen:

The bendable concrete samples are removed from the molds after 24 hours.

To achieve the concrete’s hardening property, all of the concrete samples were put into a curing tank with a controlled temperature of 25 C for a duration of 28 days.

 Curing is a crucial step in ensuring that concrete specimens don’t lose moisture as they develop the necessary strength.

Lack of healing will result in improper strength gain.

In order to evaluate the hardened properties of ECC Concrete, concrete specimens were withdrawn from the curing tank after 7, 14, and 28 days of curing.

4.Testing on concrete:

It is necessary to test the specimen after the curing process.

Cubes and slabs are tested for 7, 14, and 28 days as part of investigations.

 Cubes were tested using compression testing equipment, and slabs of (two different thicknesses) were tested using a flexural testing machine, which also allowed for the determination of the slab’s bendable properties.

Advantages of Bendable Concrete:

1. This concrete has high resilience.
2. It has elevated ductility.
3. They are very strong.
4. Unlike traditional concrete, flexible concrete does not release any harmful gases.
5. Also has greater crack resistance.
6. It is lighter than traditional concrete in terms of weight.
7. They have less steel reinforcement is used.
8. It gains the ability to heal itself.

Disadvantages of Bendable Concrete:

1. They are flexible pricing calls for skilled labour.
2. Construction using flexible concrete is expensive.
3. It is challenging to find specialized materials for flexible concrete.
4. The quality of flexible concrete is influenced by the materials used and the environment in which it is created.
5. When compared to conventional concrete, flexible concrete has a lower compressive strength.

Application of Bendable Concrete:

Constructing Roads and Bridges:

When constructing roads and bridges out of bendable concrete, expansion and contraction joints are not required.

This is due to the flexible concrete’s capacity to adapt to changes in its environment.

Construction that is Earthquake-Resistant:

More tensile stresses can be absorbed by structures made of flexible concrete. As a result, they are able to withstand high vibration brought on by dynamic forces like an earthquake.

Concrete Canvas Construction:

The concrete canvas, which is typically built for military purposes, is meant to be extremely strong and long-lasting.

Concrete that is flexible can be used effectively.

Also read: Reinforced Cement Concrete | Fibre Reinforced Concrete | Geopolymer Concrete

Conclusion:

After concrete compression and flexural strengths are measured, and the results are contrasted with those of traditional cubes and slabs.

The bendable concrete has greater strength and flexibility than conventional concrete, which helps it resist cracking and perform more effectively in seismic areas.