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Quality Assurance in Concrete Construction
Quality Assurance in Concrete Construction: The quality of the concrete in construction is an essential consideration. Concrete is used for everything from foundations to exterior and interior walls, to floors, to counter tops, to many other applications. Quality assurance in concrete construction is a huge part of any project that uses this material. Make sure you’re on track by reading this article.
The quality of the concrete is critical in the building industry, since concrete is the primary component of any structure. The longevity, load bearing capacity, and tolerance to environmental conditions such as wind, snow, and water are all determined by the composition of concrete.
Thus, the quality of concrete must be considered before constructing any building or other structure. Generally, the consistency of concrete is monitored at various points in the concreting process.
Checking the Quality of Concrete at Various Stages
- Checks on the consistency pre-concreting
- Tests for quality control during the concreting phase
- Checks for post-concrete quality control
1. Pre-concrete Quality Control Inspections
This level of quality assurance is comprised of two stages.
- Conducting a review of the specification specifications for excavation, formworks, and steel bars.
- Quality test on specific ingredients (such as cement)
Compressive strength measurements on cement cubes are used to determine the quality of the cement. However, in order to achieve optimal control, cement:
- Should be checked once for each source and then every two months afterwards.
- Should be shielded from moisture
- Should be retested after three months if extended storage is inevitable.
- If big lumps are discovered in cement bags, they should be discarded.
Concrete aggregates must conform to prescribed specifications. The physical and mechanical properties of aggregate, such as form, grading, resilience, basic gravity, and water absorption, all influence the consistency of concrete. These aggregate properties should be determined prior to using it in the manufacture of concrete.
Additionally, the amount of harmful materials and chemical impurities should be determined. Sand bulking is also a critical property in a variety of respects. When volume batching is performed, it produces inappropriate effects. It raises the water cement ratio, lowering the strength.
For efficient quality of aggregates:
- Are needed to be checked once initially to ensure the source’s approval
- Should then be checked for moisture content once or twice daily, with allowance provided for aggregate moisture content.
Water quality should be tested against the specifications stated in the applicable specification. Chemical examination shall be performed to verify the source. When impurities are suspended, it is important to store water for a period of time to enable them to settle. Concrete cubes made with this water are checked in case of uncertainty.
At least three cubes or cylinders of defined size prepared with the water proposed to be used shall have an overall compressive strength of at least 90% of the average strength of three equivalent concrete cubes prepared with distilled water after 28 days.
2. Checks During the Concreting Process
Supervision is needed during the concrete manufacturing process, including batching, grinding, shipping, laying, compacting, and curing. Precautions should be taken during the concreting process.
- The concrete mix modeling can take place in the laboratory using the materials that would be used on-site.
- Concrete should be batched as far as possible by weight. If weight batching is not practical, volume batching under careful supervision and in the presence of the engineer in charge can be allowed.
- During mixing, the mixer should be completely powered. The products should be fed in the correct order. The mixer’s speed should be between 15 and 20 revolutions per minute. In any case, the mixing time should not be less than 2 minutes. When unloading the concrete from the mixer, segregation can be stopped.
- Workability is a critical property of concrete when it is in its fresh condition. As a result, slump or compaction factor tests should be conducted to determine the workability of concrete. For every 25 m3 of concrete, approximately three experiments should be conducted.
- Precautions should be taken to ensure that no segregation occurs during the shipment of concrete.
- Concrete should not be lowered from greater than a 1 m height. If the drop height is greater than one meter, chutes can be used.
- Concrete should be put as close to its final location as possible to prevent rehandling.
- Concrete can be compacted using vibrators. Internal vibrator entry spacing does not exceed 0.6 m. It should be drawn out gradually to avoid leaving gaps in the mortar. Vibrators should have a frequency of at least 7000 cycles/minute.
- Curing should be carried out for a given period of time to ensure that the concrete develops the required strength. As soon as the concrete gets stiff, it can be coated with hessian.
- The type work should lead to the structure’s final form. It should be inspected prior to beginning the concrete work. The forms’ interiors should be washed and oiled, and they should be discarded after the agreed time frame.
- From an early age, concrete should be insulated from extreme heat and cold. Concreting should not be carried out at temperatures less than 4.50C or greater than 400. Water and aggregates can be cooled in very hot conditions. It is permissible to use licensed retarders.
- Water and aggregates can be heated in very cold temperatures. Additionally, licensed quality accelerators can be used.
3. Checks during Post Concreting
Once the concrete has been laid and compacted, compression measurements are performed on the concrete cubes. In the case of ordinary concrete, cubes are formed from the concrete produced on-site. The hardened concrete must be inspected for conformance to the design specifications in terms of dimensions, shape, and scale.
Additionally, the general appearance of the concrete’s surface should be examined. Similar ratios are used to determine dimensions. Reinforcement should be adequately covered by concrete, and where apparent reinforcement is found in a portion of a building, the portion should be discarded or appropriate steps taken.
Typically, concrete hardness is determined using cube or cylinder samples checked after 28 days. If the obtained intensity falls below the specified minimum, one or more of the following steps can be taken.
- Load testing and deflection and / or strain estimation
- Cores are removed from structures and their strength is determined.
- Schmidt hammer test or UPV experiments are non-destructive tests. These measures have only a very rough indication and are mainly used to determine construction uniformity.
- Analyses of the chemical composition of reinforced concrete.
Concrete Quality Tests That Are Important
Numerous tests are conducted to determine the quality of concrete. The following relevant measurements are routinely performed:
- Compressive strength
- Check for Water Permeability
- Initial Surface Absorption Test