When you see a crack in your concrete slab or wall, your first thought is that something has gone wrong–but this isn’t always the case.
Concrete cracks are widespread, but they are often misunderstood. When a homeowner notices a crack in his slab or wall, mainly if the concrete is fresh, he immediately suspects something is wrong. This isn’t always the case, however. Cracks are unavoidable in some cases. The best a contractor can do is try to keep the cracking under control. This is accomplished by properly preparing the sub-base, ensuring that the concrete is not too wet, using reinforcement where appropriate, adequately positioned, and spacing cracks control joints and expansion joints. However, cracks will occur despite any precautions taken.
Cracks in reinforced concrete slabs are caused by various factors such as poor concrete quality, poor structural design, improper steel bar spacing, long slab spans, improper aggregates, and so on. Although issues related to inappropriate structural design can be avoided during the design stage, other factors can be avoided during the project’s construction stage.
1. Improper Structural Design – Another reason for cracks in a reinforced concrete slab is a low reinforcement ratio caused by design errors. A lower reinforcement ratio results in a slab with lower load-bearing power. As a result, the reinforced concrete slab cracks when exposed to lighter loads.
2. Wrong Steel Bars Spacing – Cracks in the reinforced concrete slab will form when the distance between primary and distribution reinforcement is greater than the specified spacing.
3. Poor Concrete Quality – One of the causes of crack production in reinforced concrete slabs is a compromise in concrete consistency. Low concrete strength, specifically tensile strength, is a function of poor concrete quality. As a result, concrete’s tensile strength approaches its absolute limit at very low-stress magnitudes. Incorrect water-to-cement ratios, inadequate concrete mixing, incorrect concrete placement, and insufficient consolidation are all factors that may compromise the consistency of concrete. As a result, follow the correct concrete placement protocol and prepare and pour concrete according to the specified mix.
4. Improper Curing – Concrete shrinkage can occur due to improper curing, which can lead to cracks. Furthermore, it can reduce the concrete’s strength. Improper curing can result in shallow fine cracks that run parallel to each other.
5. Insufficient Concrete Cover – The needed safety for steel bars is reduced when there is an inadequate concrete cover. As a result of the chloride attacks, steel can corrode, causing the concrete to break along steel bars.
6. Expansions in Cracks – Expansion is another factor that causes concrete to crack. A concrete slab, like everything else, can grow as the temperature rises. This can put a lot of strain on a slab. The concrete expands and pushes against everything in its way, such as a brick wall or another concrete slab. If none of them can flex, anything will break as a result of the impact.
7. Wrong selection of materials – To reduce the probability of crack initiation in the reinforced concrete slab, the correct concrete constituent, such as aggregate, must be chosen. The use of alkali-aggregate in concrete can cause cracks to form.
Why is Reinforcement Important?
Synthetic fibers, reinforcing wire mesh, and rebar will strengthen concrete, but none of them can keep it from cracking. In reality, by preventing normal concrete shrinkage, too much steel will cause a slab to crack. If cracks do occur, however, reinforcing may be used to keep the various parts intact.
The presence of reinforcement may mean the difference between a crack remaining hairline in nature or splitting and expanding into something unsightly. Steel reinforcing may also be used to keep the mortar on all sides of a gap on the same horizontal axis. This means that neither side heaves or settles more than the other, posing a tripping threat. It’s not always possible to trace what triggered a specific crack. Proper site planning and concrete finishing techniques, on the other hand, can help to reduce the appearance of cracks and produce a more aesthetically pleasing project.
The value of a good mix design in concrete crack control cannot be overstated. It’s not always easy to figure out what triggered a specific crack. Site preparation, a good mix, and good concrete finishing techniques can reduce the appearance of cracks and produce a more aesthetically pleasing concrete project.