Have you ever wondered about making stronger cement that is also friendly to the environment? Well, GGBS is a unique answer to this. It is a special concrete-seek product from the waste of industry, which will turn the chemical reactions detrimental to the environment into beneficial ones and make concrete stronger. GGBS is a great option for building long-lasting structures, environmentally friendly. GGBS works a revolution in the construction area. Let’s go into GGBS deeply.
What is GGBS?
The ground granulated blast furnace slag is a cementitious material, made from a by-product of iron. The blast furnaces are heated at about 1500°C, fed up with a carefully controlled mixture of iron ore, limestone and coke. As a result of high temperature, the molten iron and molten slag are extracted. The molten slag consists of silica and alumina, with a certain amount of oxides. The slag is then granulated by cooling, by passing through high-pressure water jets, which are then dried and ground to produce fine granules of GGBS, less than 5mm.
Properties of Ground Granulated Blast Furnace Slag
Physical Properties
- Colour: Off-white, allowing for lighter finishes in concrete.
- Specific Gravity: Approximately 2.9
- Bulk Density: 1200 kg/m³
- Fineness: 350 m²/kg
Chemical Composition
- Calcium Oxide: 40%
- Silica: 35%
- Alumina: 13%
- Magnesia: 8%
Mechanical Properties
- Strength: It may have low early strength, but it gains enhanced compressive, flexural, and split tensile strength as time passes.
- Workability: This concrete mix is a very workable mix-in proportions; it makes it easy to place and compact.
- Durability: They increase resistance to all kinds of chemical and external attacks to increase life expectancy.
Sustainability and Environmental Benefits
- Energy Efficiency: Very little energy is consumed in the process of making GGBS than in the manufacturing of Portland cement.
- Carbon Footprint: There is less carbon footprint because of the partial replacement of such with Portland cement.
- Waste Utilization: They are made of wastes from the iron and steel industry, promoting the usage of waste, and reducing the landfill.
Applications of GGBS
- Used for the construction of all types of residential, commercial and industrial structures.
- Used for the construction of large-scale infrastructural projects such as roads, flyovers and mass concreting works.
- Ideal for water retaining structures and marine constructions, due to its high water resistant properties.
- Pre-cast concrete products such as blocks, and other structural elements can be built.
- Foundations and piles for high-rise buildings can be built or can be precast.
Advantages of Using GGBS in Construction
- GGBS in concrete increases the strength and durability of the concrete structure.
- It reduces the voids in the concrete structure, preventing water ingress.
- The mixture of GGBS and concrete gives a workable mix that possesses good pumpable and compaction characteristics.
- They provide enhanced resistance against chemical attacks, especially against sulfate and chloride attack.
- The colour of the GGBS cement is light and evenly distributed.
- The repair and maintenance cost of structures that use GGBS is low, increasing the lifecycle of the structures.
How To Use GGBS in Concrete Mix?
Determine the Replacement Percentage
The first step of using GGBS cement in the concrete mix is to understand the amount of OPC that needs to be replaced. Typically, the replacement range varies from 20% to 70% depending on the strength and durability requirements of the project.
Mix Design
Based on the amount of replacement, the mix design can be altered to maintain workability. The amount of cement, water, and aggregates can be determined wisely, so that it does not change the consistency desired for the mix.
Mixing and Compacting
Combine the GGBS with the OPC, aggregates, and water in a mixer, and blend until it attains a homogenous mix. Ensure that the mix is of uniform consistency, and workable condition.
Curing
Cure the prepared GGBS concrete mix under moisture to enhance strength, and reduce the chances of dissipation.
Quality Tests
After curing, quality checks such as slump test, compressive strength, and durability test can be done to identify the workability, resistance and strength, before use.
Key Differences of GGBS vs OPC
| Properties | GGBS | Ordinary Portland Cement (OPC) |
| Composition | Calcium Oxide- 40%Silica- 35%Alumina- 13%Magnesium- 8% | Calcium Oxide- 50 – 67%Silica- 17 – 25%Alumina- 3 – 8%Calcium Sulphate- 3 – 4%Iron Oxide- 3 – 4%Magnesium Oxide- 0.1 – 3%Sulphur- 1 – 2% |
| Strength | Has low initial strength and gradually gains strength over time. In general, 15 to 20% lower in strength compared to OPC in the first 28 days. | Has high initial strength, due to its quick setting time in the first 7 to 28 days. |
| Durability | Offers higher resistance to chemical attacks such as sulfate and chloride. | Often prone to chemical degradation in aggressive environments. |
| Setting Time | It has a slower setting time as compared to OPC. | It has a faster setting time, that is within 30 to 60 minutes, making it ideal for rapid construction. |
| Heat of Hydration | It generates less heat during hydration, and reduces the risk of cracking. | It generates high heat during hydration, which can lead to thermal cracking in large structures. |
| Longevity | Performs better over an extended period, making it ideal for projects requiring long-term durability. | May degrade in aggressive environments, requiring frequent repairs and maintenance. |
| Cost | Generally more expensive than the OPC due to the GGBS processing. | Relatively cheaper due to simple manufacturing and widespread availability. |
Conclusion
In conclusion, GGBS is a greener form of cement compared to ordinary Portland cement. It uses waste materials from industries to some extent, thus helping in pollution control and reducing harmful gas emissions. GGBS makes concrete better with respect to strength and durability and more workable under adverse conditions. The use of GGBS in construction means environment-friendly and long-living buildings.
Mithali Konety