Geopolymer Concrete

Geopolymer concrete is a type of concrete made by reacting aluminate and silicate bearing materials with a caustic activator. Typically, waste materials such as fly ash or slag from iron and metal products are used which helps lead to a clean environment.

This concrete is an innovative, eco-friendly building material that is used as a replacement for cement concrete.

Here we will learn about geopolymer, types of geopolymers & much more.

Introduction to geopolymer concrete:

The name geopolymer was given in 1978 by a French professor Davidovits, who represents abroad range of materials characterized by a network of inorganic molecules.

The geopolymers will depend onthermally activated natural materials such as meta kaolinite or industrial byproducts like fly ash or slag to provide silicon active sources (SI) and aluminum (Al).

Water is not included within the chemical reaction of the geopolymer concrete, instead the water is expelled throughout treatment and subsequent drying.

Types of Geopolymer Concrete:

1.Slag based geopolymer concrete:

Slag is a mixture of steel oxide and silicon dioxide, it forms a transparent by-product materials in melting processing of iron ore.

OPC substitute with slag improves performance and reduces lifecycle prices, also increases its compressive strength.

Examples are core slag, steel slag, iron blast furnace slag.

2.Rock-based geopolymers concrete:

The MK-750 forms this geopolymer in slag-based replaced by natural rock-forming minerals.

Feldspar and quartz are natural rock-forming minerals.

3.Fly ash based geopolymer concrete:

Fly ash based geopolymer concrete improves workability and increases compressive strength.

It reduces the cost of OPC with CO2 emissions.

Also reduces drying shrinkage.

4.Alkali Activated geopolymers concrete:

In alkali activated geopolymers concrete, heat curing is finished at 60 to 80 c.

In a 1: 2 aluminosilicate gel, fly-ash particles are embedded.

5.Slag-Based geopolymer concrete:

This slag based geopolymer concrete includes silicates, blast furnace slag and fly-ash.

6.Ferro-silicate geopolymers concrete:

This ferro silicate geopolymers concrete has comparable properties to rock-based geopolymer, it has excessive iron oxide content.

They are formed by substituting some aluminium atoms within the matrix.

Properties of geopolymer concrete:

Workability:

An increase in NaOH and sodium silicate solution reduces the flow of mortar.

A superplasticizer or additional water can be added to increase working capacity.

Compressive strength:

It depends on curing time and temperature.

It increases with fly ash content and grows with the beauty of fly ash.

Resistance against the aggressive environment:

It is used in the construction of marine structures.

In OPC, a white layer of crystals forms on an acidic surface, there is no gypsum deposition and visible cracks in GPC.

A soft and powder layer that forms during the initial stages of exposure that becomes harder later.

Mass loss was 3% upon exposure to H2S00 in GPC and 20–25% in OPC, the amount of alkali is high and the weight is reduced.

GPC showed better resistance.

Behavior of geopolymer at elevated temperature:

High strength loss during the initial treatment period (up to 200°C), no more than 600°C forward strength loss & no visible cracks up to 600°C.

Minor cracks at 800°C- GPC with more compatibility between aggregates and matrix led to less strength loss.

Bond strength:

About one third of its compressive strength & four times compared to OPC.

Advantages of Geopolymer Concrete:

1. geopolymer concrete has high compressive strength.
2. It has high tensile strength.
3. Also has low creep.
4. Low drying shrinkage.
5. It has resistant to heat and cold.
6. They are chemically resistant.
7. It is highly durable.

Disadvantages of Geopolymer Concrete:

1. They are difficult to produce.
2. Also, requires special handling.
3. Chemicals like sodium hydroxide are harmful to humans.
4. They have a high cost of alkaline solutions.
5. Pre-mixed with pre-mix or pre-cast material.
6. The geo-polymerization process is sensitive.
7. It loses uniformity.

Applications of Geopolymer:

Pavements:

Light pavement can be inserted using GPC.

No bleeding water goes to the surface.

Aliphatic alcohol-based sprays are used to provide protection against drying.

Retaining Wall:

A 40MPa precast panel was used to create the retaining wall.

The panels are 6 meters long and 2.4 meters wide.

These panels were fixed under ambient conditions.

Water Tanks:

Two water tanks were constructed, one with 32MPa concrete mixed with cement and the other with geopolymer concrete.

Calcium hydroxide deposition resulted in autogenic treatment in OPCs.

Due to the gel swelling mechanism in the GPC tank there is little calcium hydroxide.

Nominal leak in the rapidly healing tank.

Boat Ramp:

The ground slab for the ramp was built using a geopolymer reinforced with GFRP.

Entire components remain inactive until the activator chemicals are added.

Precast Beam:

The formal three suspended floor level GCI building of GPC Beam and buildings have curved soffits.

Water pipes were placed inside them for temperature controlled hydronic heating of top and bottom construction locations.

GPC formally beams three suspended floor levels of the GCI building, there was a curved coffin beaming.

Water pipes were placed inside them for controlled hydronic heating of top and bottom construction locations.

The formal three suspended floor level GCI building of GPC Beam and buildings have curved soffits.

Water pipes were placed inside them for temperature.

Also read: Prestressed Concrete, Ready Mixed Concrete & Underwater Concrete

Conclusion:

Geopolymer concrete is a promising construction material due to its low carbon dioxide emissions.

High early strength, acid resistance, fire resistance, low creep and shrinkage make it better in use than OPC.