Concrete is the mixture of cement, aggregates, water with or without admixtures which harden to form artificial hard rock.
Concrete is the one of the important and popular construction material, concrete is used in construction of different structures such as Dams, Retain walls, roads, buildings, pipes and tanks.
Concrete can be in two States or forms that is plastic state and in solid state.
Concrete in plastic state is called fresh concrete, this concrete is in liquid or semi solid form, able to flow and has not yet set.
Concrete in solid state is called hardened concrete, this is when it has changed from liquid or semi solid form into solid form.
Important characteristics of the Concrete that make it mostly and widely used are the following
- Concrete can be moulded into different shapes with significant strength.
- Economical Concrete of required properties can be produced for different projects.
The two important tests
There are two important tests that must be carried out to check the quality of concrete as their results give good indication to other properties of good concrete.
Workability Test
Workability is the measure of how easily to work with concrete which comprises concrete mixing , casting and compacting (vibrating), this shows easy concrete flows.
Workability of the fresh Concrete, indicate how best your concrete is in response to strength and durability.
Until today there is no way to measure workability of Concrete as it is workdone (Joule), but there are indication tests which conducted to check workability such as Slump test, flow chart method.
One of the most used indication test for workability is Slump test, which measures subsidence of concrete from its original shape.
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| Subsidence measurement of Concrete |
Slump test has three results which has its useful meaning to your concrete.
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| Types of slump test results |
True slump
This indicate that your concrete has adequate amount of water, right proportion of ingredients and well mixed.
The concrete that is found with this kind of result, it is expected to have required strength per mix design, and required durability.
Shear Slump
This indicate that your concrete has less fines that is its lack adhesiveness (bond) between concrete ingredients.
Lack of bond between ingredients produce concrete which is not durable.
Collapse Slump
This indicate that your concrete has a lot of mixing water, having much water to your concrete reduces its strength and durability.
Compressive Strength .
Compressive strength is what the concrete is required to provide, so this is the one of important property that is required to verify if your concrete will perform it's function.
This test is done by applying compression load on concrete cubes cured for some days to check their resistance limits to forces.
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| Curing of Concrete Cubes |
Resistance limits, these are maximum compression forces that concrete cubes withstand when crushed in compression testing machine.
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| Compression machine crushes concrete cube |
The resistance limits forces are then divided to cube surface area, the determined stress is termed as the strength of concrete, which is used to indicate the concrete class.
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| Crushed Concrete Cubes |
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