What Does Concrete Quality Control Mean?

Concrete is a crucial and widely used material in the construction industry. Concrete is made from raw materials such as cement, sand, aggregates, admixtures, and water. According to the specifications, all of these raw materials are mixed in a specific proportion to form concrete.

Concrete is commonly used to construct elements such as columns, beams, walls, lintels, slabs, copings, and foundations. The prepared concrete, as a material, must meet specific quality standards to be accepted for use in the construction of various concrete elements.

Concrete quality should be checked, maintained, and corrected if the quality standards do not match the required level. If the concrete is of poor quality, it may hurt the construction.

Concrete quality is checked at three different stages of construction. These are their names:

• Concrete quality control before concreting, concrete quality control during concreting, and concrete quality
• control after concreting (or after the construction of an element).
• Let’s take a close look at all three stages of concrete quality control.

First Step: Checking the Concrete’s Quality Before Pouring the Foundation

Before even beginning to work with the concrete, the quality of the raw materials must first be evaluated, and only after that can they be combined in the appropriate proportions to produce fresh concrete. The quality of the concrete is directly proportional to the quality of the raw materials used in its production.

At this point, the quality of the concrete is monitored and controlled in two separate stages. The following is a list of them:

• First step: evaluating the quality of the raw materials used in the concrete mix.
• In the second step, fresh concrete will be subjected to a battery of quality control tests.

First Step: Evaluating the Materials Used to Make Concrete

Cement, sand, aggregates, and water are the constituents that makeup concrete in that order. As a result, it is essential to have some kind of check to ensure that the quality of all of these materials is maintained.

Cement

To determine the quality of cement, standard tests involving cement cubes and their compressive strengths are typically carried out. Before the beginning of the concreting process, there are a few things that are vitally important and need to be attended to maintain quality control over the cement. These items are:

• It is important to conduct quality assurance tests on cement before using it in the concrete mixture.
• After that, the cement needs to be inspected once every two months.
• It is important to keep cement well away from any moisture.
• If the cement is going to be stored for a longer period of time, it should be retested after every three months.
• It is unacceptable to accept cement bags if they contain large chunks of cement in any of the bags.

Aggregates (Fine and Coarse)

A variety of attributes, including shape, size, grade, water absorption, durability, specific gravity, and specific volume, are associated with aggregates. When making the concrete, it is important to verify that the sample of aggregates that will be used as the desired qualities in each of these categories. Additionally, impurities are required to be eliminated before incorporating them into the concrete mixture.

• Several things to keep in mind while performing the inspection of the coarse aggregates
• Because they have a more uneven surface, the coarse aggregates are superior to the smooth aggregates in terms of their ability to bond.
• To ensure that the concrete has the appropriate amount of strength, the aggregates should be hard and robust enough.
• Even after being submerged underwater for a full day, the aggregates should not have a water content that is higher than 10%.
• The proportion of flaky and elongated aggregates in the concrete must not exceed 35 per cent of the total quantity of aggregates used in the mixture.
• A ratio of 70:30 or 60:40 between aggregates with a size of 20 millimeters and 10 millimeters should be used to allow for better compaction and to achieve a higher density in the concrete.
• When evaluating the quality of fine aggregates or sand, there are a few key considerations to keep in mind.
• Sand used in the production of concrete must remain on a 150-micron sieve and must pass through a 4.75-millimetre sieve.
• Because clay is what makes sand cohesive, the amount of clay that should be present in the sand should be reduced. Clay shouldn’t make up more than 8% of the total volume.
• Sand with a moisture content of more than 5% is not recommended for use in the production of concrete.

Water

Concrete can’t be made without water, which is an essential component. The quality of the concrete is determined both by the amount of water used and its quality. It is important to check the following aspects of the water’s quality:

• Harmful substances with a chemical composition.
• Contaminants found in water.

At least three cubes of concrete should be cast using a specific sample of water to verify the water’s quality. The compressive strength of the concrete should then be measured after it has been allowed to cure for 28 days. If the compressive strength is lower than 90%, it is recommended that the water sample be rejected.

Controlling the quality of the concrete while it is being cast is the second stage.

During the process of concrete, the following considerations are kept in mind for quality control of the concrete:

It is imperative that the design mix of concrete exactly match the mix design that is specified in the specification.

A concrete mixture ought to have its components, which are components of concrete, thoroughly mixed.

To ensure a thorough blending, the mixing machine should be rotated between 15 and 20 times, according to one recommendation.

Precautions must be taken to prevent the practice of segregation.

To guarantee that the concrete is perfectly workable, a slump test is required to be carried out for every 25 m3 of concrete that is poured.

To prevent segregation, the dropping height of concrete should not be higher than one meter.

After the concrete has been poured, the area must be properly vibrated to eliminate any air pockets that may have formed.

Concrete must be allowed to cure properly for seven days after it has reached its final hardness.

Stage 3: Concrete Quality Control After Concreting

As soon as the concrete has reached the desired consistency, its quality is evaluated using the following procedures:

• There are both chemical tests and analyses carried out on the concrete.
• The core is extracted from the concrete element, and then it undergoes testing to determine the concrete’s strength.
• On the concrete structure, non-destructive tests such as the rebound hammer test are carried out.
• The dimensions and shapes of the concrete structure are being evaluated for accuracy.