Concrete is the most utilized construction material. Therefore checking the quality of concrete is important while using it for any type of construction. To check quality we must find what are Signs of Bad Concrete Pour reduce concrete strength and durability.
What Is Concrete?
Concrete is a material made up of cement, sand, aggregate, water, and admixture if required. Concrete is the most widely used construction material in the construction of any work. It is the strongest type of construction material. Without concrete, no construction is completed nowadays.
Concrete is made by mixing cement, sand, and aggregate together with water to create a homogeneous mix. When water is added to cement it reacts with cement and makes a strong bond between all ingredients of concrete. Concrete is strong in compression and weak in tension that why reinforcements are used to make it strong in tension also.
- Concrete is an evergreen material used in building construction.
- It used in road construction work.
- It used for constructing small check dams to big concrete dam construction.
- High-performance concrete used to build a bridge.
- Concrete is also used in gates, tunnel lines, and electrical controls.
- A floor made from concrete can be stamped to create an attractive surface. It is used in driveways and patios.
- Concrete is used in making electrical poles.
Signs of Bad Concrete Pour
Following are the signs of Poor Concrete Work,
1. During Concrete Pouring
First we discuss about signs of bad concrete pour or sign of bad concrete mix of fresh concrete,
1. Segregation of Concrete
Segregation of concrete is the separation of cement paste from the aggregate during handling and placing of concrete. It also occurs if the concrete is over compacted or vibrated, in which cement paste comes to the top, and aggregates settle at the bottom. Segregation is major sings of bad concrete mix.
Segregation in concrete affects the overall strength and durability of the concrete structure. In well-mixed concrete, all the aggregate particles are evenly coated with sand and cement paste and form a homogeneous mass.
2. Bleeding of Concrete
Bleeding occurs when the free water in the mix is pushed upward to the surface due to the settlement of heavier solid particles such as cement and water. There is some accepted limit but excessive bleeding can be problematic. The bleeding of concrete reduces the strength of concrete products. Bleeding is a signs of bad concrete.
The main reason factor that causes the bleeding in concrete is the water-cement ratio. A greater water-cement ratio leads to excessive bleeding. The type of cement used and fineness of aggregate particle is used to determining the bleeding rate. As a lesser fine in concrete, more bleeding will occur.
2. After Hardening of Concrete
1. Cracking of Concrete
Cracking after concrete gets hardened is a major defect of concrete. A crack in concrete is a fine linear fracture that extends partly or completely through the member. The major reason behind crack produced is tensile stress developed in concrete members. if concrete crack after hardening it is signs of bad concrete.
Tensile stresses are resisted by the concrete and reinforcement until the level of the tensile stresses exceeds the tensile capacity (modulus of rupture) of the concrete. After this resisting capacity the concrete cracks and the tensile force are transferred completely to the steel reinforcement.
Severity of Cracks in Concrete,
- Hairline cracks – less than 0.1 mm wide
- Narrow cracks – 0.1 mm to 0.3 mm wide
- Medium cracks – 0.3 mm to 1.0 mm wide
- Wide cracks – greater than 1.0 mm wide
2) Spalling of Concrete
Spalling occurs when a large piece of concrete separates from the main member. Spalling defects are very similar to scaling in which just flakes break loose from concrete.
This may reduce the strength of the structure and cause serve damage. Spalling is more likely to occur in freezing and throwing conditions.
This defect is a result of the continuation of the delaminating process which is caused by the actions of external loads, the pressure exerted by the corrosion of reinforcement.
It is also occurred by the formation of ice in the delaminated area results in the breaking off of the delaminated concrete. The affected area left behind is known as a sharp edge.
Severity of Spalling,
Light – Defect area measuring less than 150 mm in any direction or less than 25 mm in depth.
Medium – Defect area measuring between 150 mm to 300 mm in any direction or between 25 mm and 50 mm in depth.
Severe – Defect area measuring between 300 mm to 600 mm in any direction or between 50 mm and 100 mm in depth.
Very Severe – Defect area measuring more than 600 mm in any direction or greater than 100 mm in depth.
3) Scaling of Concrete
Scaling defect occurs in concrete when the loss of the surface portion of concrete or mortar as a result of the freeze-thaw deterioration of concrete occurs. This type of defect is common in on air-entrained concrete, but can also occur in air-entrained concrete in the fully saturated condition.
Scaling mainly occurs in poorly finished or overworked concrete were too many fines and not enough entrained air is found near the surface. So it is signs of bad concrete if scaling occurs in concrete.
Severity of Scaling,
Light – Loss of surface mortar up to 5mm depth without exposure of coarse aggregate;
Medium – Loss of surface mortar up to 6 to 10 mm depth with exposure of some coarse aggregates;
Severe – Loss of surface mortar up to of 11 mm to 20 mm with aggregate particles standing out from the concrete and a few completely lost.
Very Severe – loss of mortar and aggregate particles to a depth greater than 20 mm.
4) Honeycombing of Concrete
Honeycombing in concrete generally occurs due to improper compaction or vibration of concrete during placing which results in voids being left in the concrete where the mortar failed to completely fill the spaces between the coarse aggregate particles.
It is signs of bad concrete if there is honeycombing seen after removal of formwork.
Severity of Honeycombing,
Light – Defect up to depth less than 25mm.
Medium – Honeycombing to a depth between 25mm and 50mm.
Severe – Honeycombing to a depth between 50 mm and 100 mm.
Very Severe – Defects up to a depth greater than 100 mm.
5) Alkali Aggregate Reactions In Concrete
A chemical attack on concrete can occur if aggregates are alkaline and chemically reactive. concrete can be attacked by different chemically active matters like acids, some alkalis, numerous salt solutions, and organics such as fermenting liquids, sugars, and animal oils, especially if they contain free acids. It is signs of bad concrete.
Seawater is rich in suphate which is able to react with concrete and deteriorate it. Some chemicals that can cause corrosion that may reach the steel reinforcing rods may be particularly destructive because the large displacement of the corrosion products of the steel can cause cracking and spalling of the concrete.
6) Delamination of Concrete
Delamination is defined as discontinuity or separation of the concrete layer which is substantially separated but not completely detached from the concrete below or above it. Visibly, it looks solid single component concrete but can be identified as a hollow sound by tapping or chain dragging. It shows signs of bad concrete.
Delamination is generally started with corrosion of steel and subsequent cracking of the concrete. it may also occur when concrete is patched or overlaid due to the continued deterioration of the older concrete.
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