Before learning about concrete quality control. We should first know about a few basic things.
What is concrete?
Concrete is the most versatile building material used widely all around the world. It is made by mixing fine aggregates (sand), coarse aggregates (gravel), cement (binding material), water (lubricant), and admixture (optional).
It is strong, durable, low maintenance, fire-resistant, simple to use and can be made to fit any size in the world. Moreover, it’s cheap.
The most common cement used in concrete is Ordinary Portland Cement (OPC).
An example of admixture that can be used is Pozzolana.
There are different types of concrete. They are Lime concrete, Cement concrete, Reinforced Cement Concrete, Dry Ready-mix concrete, Ready mix concrete, Transit mix concrete, Regular concrete, High-strength concrete, stamped concrete, High-performance concrete, Self-consolidating concrete, Vacuum concrete, shotcrete, Roller- compacted concrete, Glass Concrete, Asphalt concrete, Rapid strength concrete, polymer concrete, Limecrete, Light-transmitting concrete and green concrete (also known as plastic concrete).
Why are aggregates used while making the concrete?
Aggregates are cheaper than cement. So this helps to reduce the cost of the concrete. Moreover, the aggregates also improve the structural properties of the concrete by increasing the strength of the concrete and reducing the amount as shrinkage as the concrete cures.
The exact amount and characteristics of different ingredients that should be taken to make the concrete is an essential factor that affects the quality of the concrete.
Note: The process of developing a specific concrete formula is called mix design.
Different types of concrete mix are used for a different purpose.
What is quality control of concrete?
Quality control of concrete is different than quality control of most manufacturing products. It is not what you do in the factory and define it and sell it.
Quality control of concrete is done by civil engineers or project managers or supervisors in the construction phase and during the placement phase, it is done by civil engineers only.
Quality control of concrete defines the durability, strength, and reliability of structure like a building, bridge, culvert road, etc.
Quality control of concrete includes the following points:
How it will be cast?
How it will be cured?
How it will be placed?
How it will be checked and tested?
What factors affect the quality of the concrete?
- Properties of raw materials used
- Shape and size of aggregates
- Water cement ratio
- Coarse/fine aggregates ratio
- Relative humidity
- Age of concrete
- Equipment used
- Compaction of concrete
- Curing of concrete
Importance of quality control
- To achieve quality and durable building structure.
- To make a building look elegant.
- To give a building more strength.
- To prevent the appearance of cracks in the concrete due to extreme weather condition or water vapour.
- To prevent the shrinkage of the concrete.
- To obtain a uniform product (concrete) every day.
- To ensure the consistency of the production.
Where does quality control begin?
The most important factor that affects the quality control of concrete is the production of raw materials used in the production of the concrete.
How does quality control continue?
- After selecting the raw materials having good qualities, the second step is handling and stockpiling the raw materials in the factory site.
- Then batching and mixing of the raw materials is done as per the use of the concrete.
- Then different tests are done to ensure the quality of the concrete.
- Finally, the concrete is transported and placed in the design site.
Common quality test for concrete
- Slump Test: To determine the workability of the concrete.
- The compacting factor test
- Compressive strength test
- Tensile strength test (Split Cylinder Test)
- Water Permeability Test
- Water Absorption Test
- Initial Surface Absorption Test
- Rapid Chloride Ion Penetration Test
Last four tests are used to determine the ability of the concrete to resist the weathering action, chemical attack and any process of deterioration.
Quality control is a very complicated task. Doing repeated work may be tiring or boring for a civil engineer. But you should look at it as a very important step.
Because there will no point in finding mistakes when concrete comes in the plastic stage. you have to find a mistake o the spot if any regarding placing, mixing, compacting, etc.
Let us take an example: If there is a fault in your mix design or mix properties and you will find it after one month of completing it, then you will think about demolishing the building or a big disaster happening soon. This might kill thousands of people causing great economic losses.
But this can be prevented if quality control is done consciously.
I hope this articles remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Sushmita Niraula