concretefurniture

[concretefurniture]

DAY 5 (2) - Field Visit

Our second stop was the main factory of Aarya Precast Pvt. Ltd where production happens. 

Machine 1: Concrete Mixer

Product – 8ft X 4ft GRC Jaali

Components

White Cement – 25 kg

Super Plasticizer (reduces water content)

Pigment (coloration) – 100g

Sand – 25kg

White Polymer – 500ml

Water

The quantity of each component is calculated based on the total volume required to make the product. Concrete is mixed vigorously to remove debris and maintain consistency of colour.

This was an old concrete mixer used earlier 

Glass reinforcement

Clay Aggregates

Mixed concrete ready for first coat

Machine 2: Spray Station

Production Method : Spray Mix

At first, a layer of concrete is sprayed in the mould. Due to the air pressure, the density of the concrete is high when compared to the Pre Mix method of production(see below). The air pressure also helps in removing air bubbles.

After this initial layer, a second layer of concrete mixed with glass fibres (reinforcement) is sprayed.

In the case of a rubber mould, a mould releasing agent is applied as a coat to ease the demoulding process.  

Finally, concrete is manually leveled in the mould and left still for 8 hours. During this time, the concrete hardens.

Production Method : Pre Mix

This production method is predominantly manual. Similar to Spray Mix method, the first layer applied is of concrete while the second layer is reinforced by mixing glass fibres.

This process is done on a vibrating table as it helps in avoiding air pockets.

Pigments

Pigments in the form of iron oxides can be added to the concrete mix to give it colour. If the colour is added directly to the mix, even if the concrete chips off, the colour does not change. 

This type of staining process only colours the surface of the object. 

[concretefurniture]

DAY 5 (1) - Field Visit

On Day 5, we visited Aarya Precast, a well equipped concrete factory in Ahmedabad, India. During our visit, we learnt about the machinery used, its various production processes and also got a hands on experience of how the material is handled!

Our educational trip began with a visit to one of Aarya Precast’s  godowns. This godown stored architectural elements like jaalis, domes and cornices.

Basic Process

The 1ft X 1ft unit master mold of a jaali is an FRP mold. Each extrusion has tapered edges for the ease of demoulding.

This is the master piece made of MDF. The master piece is used to make the master mold. 

The final product is as you can see above. 

Modular Concrete Bathroom

This modular bathroom is predominantly made of concrete with metal framework that serve as structural support. The walls are outlined with silicone gaskets to avoid water seepage. 

The internal bathroom fittings are concealed between two layers of 12mm walls. The walls are simply bolted and can be handled by two men. This design makes dismantling and rebuilding simple.

Grey panels - 12mm

Brown Panels – 18mm

This concrete wash basin has a leather texture on it. This texture was derived using actual leather fabric.

All panels are epoxy coated in order to make it water proof. The external walls are weather proof and are 12mm thick. 

Planters

The white colored planter - externally painted

The pink colored planter – Acid washed

The yellow colored planter – epoxy coated, no additional wash applied.

These benches were trial pieces. All of them are epoxy coated.

Types of Moulds

The following two moulds are silicone (white) and rubber moulds (red)

Mold for a Masjid Dome. 

Material – Concrete and FRP

[concretefurniture]

DAY 2

Day 2 revolved around understanding the science and technique behind moulding concrete. The first half of the day was a presentation by experts from Aarya Precast, Ahmedabad and the second half of the day was spent discussing the final outcome of this course. We were asked to choose a direction in which we would like to proceed and choose a product we would like to execute.

Notes

Composite Concrete

Primary reinforcements for concrete include fibre glass, carbon, steel etc.

Material Composition

Concrete widely comprises of cement, fine aggregate, fibre, admixtures, water and pigment.

Production Methods

There are broadly two kinds of production methods

1. Spray Mix- Sprayed concrete is usually referred to as Gunite (dry mix) or Shotcrete(wet mix). It is usually self-supporting without the need for form work.

2. Pre Mix

Admixtures

Admixtures are substances other than cement, water and aggregate that are added to the mix immediately before or during mixing. It contributes to achieving the perfect constituency ratio. Water based admixtures help in reducing the water content.

After concrete is poured onto mold, within the next 8 hours, changes can be made to the form. Slowly after, the concrete begins to harden.

Types of Moulds

Wooden 

Plywood - Smooth organic surfaces 

FRP

Rubber – Costliest but most versatile with best quality especially in case of mass production 

Silicon – Equally expensive but a little less rigid compared to rubber 

POP – Cost efficient but only suitable for one time use 

Fabric – water repellent

Surface Finishes

Smooth Surface 

Geometry 

Form 

Sharp 

Edges 

Stamped 

Acid Washed 

Stained 

Patterned

Acid washed concrete flooring 

Various Applications of Concrete

Bathing, Collection, Dining, Kitchen, Landscape Furniture (Interior and Exterior), Gift articles – organisers, planters etc. Stationary, Tableware, Lamps, Jewellery, Architecture Elements – Jali and Screens, Interior articles etc.

Points to Remember

Rubber molds are usually used when texture of form is of prime importance.

Foam Concrete – Can absorb water but it can’t pass through it

Pervious Concrete – Water can pass through but not get absorbed

Sources

Class Notes 

http://www.gunform.com/sprayed_concrete.php (Spray Mix) 

www.aboutcivil.org

[concretefurniture]

DAY 1

Hello and welcome to my blog for Design Workshop III - Concrete. Via this blog, I will record my learnings and experiences in this course.

Our day began with an introduction of the Concrete as none of us have worked with it earlier. We were briefed about its constituents, the different possibilities of the material and also its limitations.

Notes

Abbreviations

GRC – Glass Reinforced Concrete

GFRC – Glass Reinforced Fibre Concrete

Types of Concrete

Pervious concrete

Sandwich light weight concrete

Glass Reinforced concrete

Foam concrete

Constituents

The constituents of concrete depend on the desired type or texture. Standard GRC includes the following

Cement

Silica Sand

Iron Oxide

Stain (colour – optional)

Glass Fibre

Polymers

Water

Properties

In this course, we will lay emphasis on and experiment with GRC. Its properties include -

Strength and Durability. Used in the majority of buildings, bridges, tunnels and dams for its strength.

Versatility.

Low Maintenance.

Affordability.

Fire-resistance.

Relatively Low Emissions of CO

Reinforcing Concrete

While, concrete is known for its structural strength, the necessity for reinforcement arises when the section is longer horizontally, in case of complex forms and large scale.

Common materials used for reinforcement include Glass fibre, SS or MS rods that pass through the material in a mesh structure, fabric/textile etc.

Concrete and Other Materials

In case another material needs to be adjoined to concrete, sealants and joinery are used. For example, in the case of the picture below, butterfly joineries are used to hold the wood and concrete in place.

Staining

Apart from Gray / White which are natural colours of GRC, by the process of staining, a wide range of colours can also be applied. 

Post Treatment

PV Coat, Wax coat and Lacquer are used as surface finishes for concrete. A matt and glossy effect can also be achieved. 

Points to Remember

Minimum Thickness – 8mm

Maximum Thickness – 20mm

Chamfered or Filleted edges are generally observed on products with this material to hide errors and to prevent chipping off of the corners

For GRC, 1 cubic metre contains 5 bags of cement

Right angles are hard to achieve, a 10 degree slant is always needed in the mold of any furniture. 

Assignment 1

Before we start designing, we were asked to research about concrete and its various applications in the design industry, in pairs. 

Highlights

Many artists and designers are challenging concrete’s conventional brutal and rugged look. They play with form, surface graphics, constituency etc to give concrete a more graceful look. Once such designer is Tel Aviv based Itai Bar-on. 

Designers are also exploring fusion of concrete with materials like paper, textile, optical fibres to add an interesting twist to the product. 

This concrete fruit basket is made of mortar concrete. Its is very visually appealing due to the woven concrete appearance.